Clean copy

FORM 2
THE PATENTS ACT 197
(39 of 1970)

THE PATENTS (AMENDMENT) RULES, 2006

COMPLETE SPECIFICATION
(See section 10 and rule 13)

l . TITLE OF THE INVENTION

Centrifugal Impeller And Turbomachine

2. APPLICANT

NAME Nuovo Pignone S.p.A.

NATIONALITY IT
ADDRESS Via Felice Matteucci, 2 50127 Florence (IT)

3. PREAMBLE TO THE DESCRIPTION

COMPLETE

The following specification particularly describes the invention and the manner in which it is to be
performed.

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 DESCRIPTION
TECHNICAL FIELD

Embodiments of the subject matter disclosed herein generally relate to

composite centrifugal impellers for turbomachines and related production

methods, particularly, but not exclusively, for oil and gas applications.

Other Embodiments generally relates to a mold for producing this

centrifugal impeller, some particular components to make this centrifugal

impeller with this mold, and a turbomachine in which said impeller could be

used.

BACKGROUND ART

A component of a centrifugal turbomachine is the centrifugal i mpeller,

which transfers, in general, energy from the motor that drives the

turbomachine to a working fluid being compressed or pumped by accelerating

the fluid outwards from the center of rotation; the kinetic energy imparted by

the impeller to the working fluid is transformed into pressure energy when

the outward movement of the fluid is confined by a diffuser and the machine

casing. This centrifugal machine is called, in general, a compressor (if the

working fluid is gas) or a pump (if the working fluid is a liquid).

Another type of centrifugal turbomachine is an expander, which uses

the pressure of a working fluid to generate mechanical work on a shaft by

using an impeller in which the fluid can be expanded.

US 4,676,722 describes a wheel for a centrifugal compressor made by

a plurality of fiber loaded scoops. A disadvantage of this particular impeller

is that the various scoops have direct fiber reinforcement substantially in the

radial direction, so it is difficult to balance circumferential stress as

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generated by centrifugal forces at a high speed of rotation. After

manufacturing, the sectors are joined to each other by the adhesive strength

of a bonding agent, which limits the maximum speed of operation. Also, the

method of manufacture, in which the assembly is drawn into place by

filaments, is restricted to relatively simple geometries (e.g. with straight -

edged sectors) which may have low aerodynamic efficiency.

US 5,944,485 describes a turbine of thermo-structural composite

material, particularity one of large diameter, and a method for manufacturing

the turbine that provides mechanical coupling for its assembly by means of

bolts, grooves, slots, and so on. A disadvantage of this impeller is that the

mechanical coupling cannot ensure a high resistance at high rotational

velocity when using either a corrosive or erosive working fluid. Therefore the

reliability of this component may decrease dramatically. In addition, the

scheme for attaching the airfoil to the hub provides user continuous fibers

around the internal corners of the passages. Since these are typically areas of

high stress, it is desirable to have fibers that are continuous from the airfoil to

the cover and from the airfoil to the hub.

US 6,854,960 describes a segmented composite impeller or propeller

arrangement and a manufacturing method. The main disadvantage of this

impeller is that it relies on adhesive bonding to join identical segments. As a

result, it does not have a high mechanical resistance to work at high rotational

velocity, and centrifugal forces can separate identical segments and destroy

the impeller itself. Another disadvantage is that it is not possible to build an

impeller with vanes with complex geometry, as is the case with three

dimensional or similar impellers.

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 In general, a disadvantage of all the aforesaid impellers is that they

present a relatively complex mechanical structure, because they are composed

of several different components that need to be made independently and then

mechanically assembled together. Moreover, the components made of fibers

have to be built in general by expensive metal molds, increasing the cost of

manufacture. Also, different metal molds have to be used to build these fiber

components for each different type of impeller, which significa ntly increases

the cost of manufacture. Again, these mechanical assemblies are not easily

achievable by means of automated machinery, further increasing the time and

cost of manufacture.

Another disadvantage is that the vanes of these impellers are not

protected in any way from solid or acid particles suspended in the working

flow, therefore erosion and corrosion problems could be significant and may

lead to the destruction of the component.

Yet another disadvantage is that it may be difficult to achieve the

mechanical assembly of all the components needed for optimal operations of

the impeller at high speed. Moreover, any distortion produced by the tensions

and forces created during use can cause problems during operation, especially

at high speed; vibrations may occur during operation, caused by wear and/or

by a faulty assembly of various components. Therefore, the impeller may fail.

To date, notwithstanding the developments in technology, these

disadvantages pose a problem and create a need to produce si mple and

inexpensive centrifugal impeller for turbomachinery in an even faster and less

expensive way, while at the same time producing an improved and high

quality finished product. A particular need exists to produce an innovative

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 centrifugal impeller by taking advantage of composite and fiber technologies,

whilemostly preserving the mechanical, fluid-dynamic and aerodynamic

properties of metallic impeller, in order to effectively use this innovative

impeller in the turbomachinery field. Design improvements are needed to

take greater advantage of the inherent strengths of composites, and to enable

safe operation at higher tip speeds than is possible with typical metallic

impellers.

SUMMARY

An object of the present invention is to produce a simple, fast and

cheap mold for building a centrifugal impeller, overcoming at least some of

the drawbacks mentioned above.

A further object is to develop a method for the production of said

impeller, particularly a method for creating the impeller using composite

material.

A further object is to produce some components to make said impeller

by said mold in an easy and cheap way.

According to a first aspect, there is a centrifugal impeller for a

turbomachine comprising a plurality of aerodynamic vanes; each of these

vanes comprising internal walls on which is associated at least a fabric

element.

In other words, the aerodynamic vanes are the empty spaces between

adjacent blades. During the use of the impeller, in a few words, the working

fluid enters into an inlet eye of each aerodynamic vane, passes through the

vane, in which the fluid is pushed radially by the geometry of the vane itself

and by the rotation of the impeller, and finally goes out through an eye outlet

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of each vane.

It must be understood that, in this description and in the attached

claims, the term “fabric” is used to imply a number of one or more of a

variety of different fibrous structures woven into a pattern, such as a braid

pattern, a stitched pattern, or an assembly of layers (and not woven

arrangements only). See the descriptions below.

In a particularly advantageous embodiment of the subject matter

disclosed, first fabric elements are configured to surround each aerodynamic

vane in order to substantially reproduce the shape of the aerodynamic v ane

such that the aerodynamic characteristics of said vane are preserved. The

fabric comprises fibers that are advantageously and preferably continuous

around the entire internal surface of each vane thereby providing a high

resistance to mechanical stresses generated at these locations. In this way a

single vane becomes particularly resistant to the mechanical stress and at the

same time is able to preserve its aerodynamic characteristics.

In another advantageous embodiment of the invention, a second fabr ic

element is configured to alternately surround an upper wall of a vane and a

lower wall of an adjacent vane passing along the respective blade

therebetween such that the aerodynamic characteristics of said vane are

preserved.

In another advantageous embodiment, a third fabric element has a

substantially conical surface with fabric blades stretching out from the

surface; these fabric blades being able to reproduce substantially the blades

of the finished impeller..

It is clear that the aforesaid three embodiments could be realized in

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different ways according to specific needs of manufacturing or use; also, it

does not exclude realizing these embodiments in combinations one to the

other.

In another embodiment, a shaped component is associated inside each

of the aerodynamic vanes in order to act against the erosion or corrosion

phenomena caused by the working fluid.

In fact, the working fluid could be a gas, a liquid or in general a

mixture thereof, and the erosion or corrosion process could be aggravate d by

the high rotational speed of the impeller, which causes the liquid or solid

particles in the flow to strike the blade with higher force.

In another advantageous form of implementation, the impeller

comprises a fourth fabric element placed over the aerodynamic vanes; this

fourth fabric element could substantially have a centrifugal shroud shape and

function.

Moreover, the impeller could comprise a fifth fabric element having

substantially an annular planar shape that realizes substantially a rear -plate

for the impeller itself.

A sixth fabric element could be fitted under the aerodynamic vanes;

this element has substantially an annular shape and is able to be matched with

the external inferior surface of the vanes.

A seventh fabric element could be advantageously fitted around an

axial hole inside which a rotor of the turbomachine fits. The fourth, fifth,

sixth and seventh fabric elements could be provided, preferably in

combination one to the other, to increase the mechanical resistance of the

finished impeller; however, it must be understood that these fabric elements

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could be used alone or in various combinations according to the specific

needs of manufacturing or use.

In an advantageous embodiment, all the aforesaid fabric elements –

when provided – are enclosed or associated in the filling material, typically

called “matrix”, in order to obtain a more rigid shape for the impeller.

In a particularly advantageous embodiment, all of the aforesaid fabric

elements – when provided – are matched or pressed together in order to

minimze the empty spaces between them. In this case, the filling material

used to fill the spaces between adjacent fiber elements is reduced as much as

possible, in order to maximize the amount of structural fiber within the

volume. This will further increase the mechanical resistance of the finished

impeller.

In a further advantageous embodiment, an inner core element is placed

under the aerodynamic vanes in order to facilitate the manufacturing process

of the impeller, in particular to facilitate the deposition of the said fourth,

fifth, sixth, and seventh fiber elements in place, and, when provided,

providing a base for the fiber deployment. Also, the core element could be

configured advantageously to give a higher strength and st iffness during the

work of the finished impeller at high rotational velocities.

The core could be made at least by a material more rigid than the

filling material before it’s cured, for example: wood (for example balsa),

foam (for example epoxies, phenolics, polypropelyne, polyurethane,

polyvinyl chloride PVC, acrylonitrile butadiene-styrene ABS, cellulois

acetate), honeycomb (for example kraft paper, aramid paper, carbon or glass

reinforced plastic, aluminum alloys, titanium, and other metal alloys),

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polymers (for example phenolics, polyimides, polyetherimides,

polyetheretherketones), or metallic materials or others.

In particularly advantageous embodiments, the core consists of

unfilled cavities that decrease the overall density of the core, so that it is

substantially lower than that of the fabric or filling material. This will result

in lower forces on the adjacent structure when subjected to high rotational

velocities.

In particular embodiments, the core could be surrounded, in part, by at

least one of the aforesaid fabric elements - alone or in various combinations,

when provided – in order to obtain a particularly compact, rigid and resistant

system.

According to a preferred embodiment of the invention, the above

fabric elements are made by a plurality of unidirectional or multidirectional

fibers, realized substantially to have a high anisotropy along at least a

preferential direction. These fibers could have a substantially thread -like

shape, as for example carbon fibers, glass fibers, quartz, boron, b asalt,

polymeric (such as aromatic polyamide or extended-chain polyethylene)

polyethylene, ceramics (such as silicon carbide or alumina) or others.

It does not exclude, however, that these fabric elements could be

realized with two or more layers of fibers, with a combination of fibers of

different types or with different types of elements, as for example with

granular, lamellar or spheroidal elements or woven, stitched, braided, non -

crimp or other fabrics, unidirectional tapes or tows, or any other fiber

architectures. .

The above filling material could be realized by a material able to hold

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together, to evenly distribute the tensions inside, and to provide high

resistance to high temperatures and wear for the fabric elements; on the

contrary, the fabric elements are able mainly to provide high resistance to the

tensions during the work of the impeller. Moreover, the filling material can

be arranged to present a low specific mass or density in order to reduce the

weight of the impeller and thus the centrifugal force generated during the

work.

The filling material could be preferably an organic, natural or

synthetic polymer material, whose main components are polymers with high

molecular weight molecules, and which are formed by a large number of

basic units (monomers) joined together by chemical bonds. Structurally, these

molecules may be formed from linear or branched chains, tangled with each

other, or three-dimensional lattices, and mainly composed of carbon and

hydrogen atoms and, in some cases, oxygen, nitrogen, chlorine, silicon,

fluorine, sulfur, or others. In general, polymeric materials are a very large

family of hundreds and hundreds of different substances.

One or more auxiliary compounds can also be added to the polymer

materials, such as micro- or nanoparticles, which have different functions

depending on the specific needs, for example to strengthen, toughen,

stabilize, preserve, liquefy, color, bleach, or protect the polymer from

oxidation.

In an advantageous form of implementation of the invention, the

polymer filling material is constituted, at least in part, from a thermoplastic

polymer such as PPS (polyphenylene sulphides), PA (polyamide or nylon),

PMMA (or acrylic), LCP (liquid crystal polymer), POM (acetal), PAI

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(polyamide imide), PEEK (poly-ether-ether-ketone), PEKK (poly-ether-

ketone-ketone), PAEK (poly-aryl-ether-ketone) , PET (Polyethylene

tereptalato), PC (poly carbonate), PE (polyethylene), PEI (Poly -ether-imide),

PES (polyether), PPA (poliptalamide), PVC (polyvinyl chloride), PU

(polyurethane), PP (polypropylene), PS (polystyrene), PPO (polifenilene

oxide), PI (polyimide; exist as thermosetting), or more. For particularly high

temperature applications various polyimides such as polymerized monomeric

reactant (PMR) resins, 6F-Polyimides with a phenylethynyl endcap (HFPE),

and phenylethynyl-terminated imide (PETI) oligomers may be preferred.

In another advantageous form of implementation of the invention, the

polymer filling material is at least partly constituted of a thermosetting

polymer, such as Epoxy, phenolic, polyester, vinylester, Amin, furans, PI

(exist also as thermoplastic material), BMI (Bismaleimides), CE (cyanate

ester), Pthalanonitrile, benzoxazines or more. For particularly high

temperature applications various thermosetting polyimides such as

polymerized monomeric reactant (PMR) resins, 6F-Polyimides with a

phenylethynyl endcap (HFPE), and phenylethynyl-terminated imide (PETI)

oligomers may be preferred.

According to another advantageous embodiment of the invention, the

filling material is composed of a ceramic material (such as silicon carbide or

alumina or other) or even, at least in part, from a metal (such as aluminum,

titanium, magnesium, nickel, copper or their alloys), carbon (as in the case of

carbon-carbon composites), or others.

An advantage of the impeller created according to the invention is that

it presents high quality and innovative characteristics.

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 In particular, the impeller is extremely light while, at the same time,

has a comparable resistance with respect to the known impeller made of metal

used in the turbomachine field (for high rotational velocity and for high

pressure ratio).

In fact, a traditional metallic impeller could weigh from about 10 to

2000 kg depending on the impeller size, and the impeller according to the

invention could weigh from about 0.5 to 20 kg (for the same type of

impeller). Therefore, the weight reduction is greater than 75%.

Another advantage is that an impeller made according to the invention

could be used with a lot of different fluids (liquid, gas or a mixture thereof)

and with fluids that present high corrosive or erosive characteristics.

A further advantage is comes from the fact that it is particularly

inexpensive and simple to produce and to handle. See description below.

Another advantage is that it is particularly easy to apply more

components or elements to improve the quality or the mechanical

characteristics of the impeller according to specific requirements, like the

shaped components or fiber elements made by specific shape or other.

Again, another advantage is that an impeller made according the

present invention could be of different types, preserving at the same time

aerodynamic and mechanical characteristics For example, the impeller could

be a three dimensional impeller, a two dimensional impeller, or others.

According to a second aspect, there is a turbomachine wherein at least

a centrifugal impeller as described above is implemented.

In particular, this turbomachine could be a centrifugal compressor (for

gas) or pump (for liquid), or else it could be a centrifugal expander; in any

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case, the turbomachine has preferably a plurality of these impellers associated

on a common shaft in metal or other material (for example a composite

material).

According to a third aspect, there is a mold to build a centrifugal

impeller for a turbomachine comprising of, at least, an annular insert

comprising a plurality of aerodynamic vane inserts reproducing the

aerodynamic vanes of the finished impeller.

In particular, the annular insert could be made by a single piece or,

preferably, by joining together a plurality of pieces, see below.

The mold comprises preferably and advantageously a base plate having

an internal face and an external face, the internal face being configured to

reproduce a rear-surface of the impeller and the external face being

substantially opposite to the internal face; an upper-ring having an internal

face and an external face, the internal face being configured to reproduce a

front-surface of the impeller and the external face being substantially

opposite to the internal face.

In other embodiments, the mold comprises the aforesaid fabric

elements having preferably and advantageously a (semi) rigid shape and

being made separately before placed inside the mold.

In a particularly advantageous embodiment of the invention, the mold

comprises the inner core associated under the centrifugal impeller preform

and over the base plate; the inner core could be realized in numerous different

embodiments according to different technical needs or requirements of use.

See below.

In another advantageous embodiment of the invention, the mold

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comprises a plurality of shaped components able to be associated on an

external surface of each aerodynamic vane insert; these shaped com ponents

are configured to act against the erosion or corrosion of the working fluid

during the work of the finished impeller.

In particular, these shaped components could be associated between

one of the aforesaid fabric elements and the surfaces of the an nular insert

corresponding to the walls of the vanes, in a position where the erosion or

corrosion process caused by the working fluid is higher.

A closure system could be provided to close the preform between the

base-plate and the upper/ring, in order to center and lock said impeller

preform between them. This system could be realized in a plurality of

different types, for example in a mechanical system (centering pins, screws or

others), a geometrical system (shaped holes, shaped grooves, shaped teeth,

shaped surfaces or others), or others systems.

An injection system is provided to inject the filling material inside the

mold by means of injection channels made inside the base plate and/or the

upper-ring.

An advantage of the mold according to the present invention is that the

finished impeller the mold produces is high quality and has innovative

characteristics for the turbomachinery field.

Another advantage is that the material used for the annular insert could

be something low-cost and easy to machine, such as high-density foam or

ceramic.

Moreover, the material is very compact and yet extremely versatile,

because it is possible to make a lot of different types of impellers providing

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an annular insert with specific geometry and shape (in particular thr ee or two

dimension impellers).

Yet another advantage of the mold design is that it allows a single –step

infusion and cure of the filling material through the entire part. This provides

for a high strength part and eliminates the need for secondary joini ng

operations such as bonding, machining, or mechanical attachment which can

be costly and time-consuming. In addition, the possibility for part

contamination or handling damage between operations is eliminated.

According to a fourth aspect, there is an aerodynamic vane insert

configured to reproduce at least an aerodynamic vane of the finished

centrifugal impeller such that the aerodynamic characteristics of the vane of

the finished impeller are preserved.

Advantageously, the aerodynamic vane insert comprises at least a

central region configured to properly reproduce the aerodynamic vane and

end-regions configured to be associated with end-regions of an adjacent insert

forming the annular assembly.

In a particularly advantageous embodiment, these shaped end -regions

are configured to be associated with end-regions of an adjacent insert in order

to create the inlet and respective outlet eyes for the working fluid and for

handling, positioning the insert within the mold, and containing resin

channels. More, the shaped end-regions could be provided with sealing

elements to avoid a leakage during the injection of the filling material.

In a preferred embodiment, the aerodynamic vane inserts are made by

at least a single piece; however it does not exclude that the inserts could be

made of two or more pieces or, on the contrary, a single insert could produce

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two or more aerodynamic vanes according to the particular embodiments.

The advantage of this aspect of the invention is that it allows the

fabrication of vanes with complex 3D geometry such that the inserts can

readily be removed from the impeller after the filling material has cured.

According to another exemplary embodiment, an aerodynamic vane

insert is joined with other vane inserts to form an annular assemb ly

reproducing of all the aerodynamic vanes of the finished impeller such that

the aerodynamic characteristics of the vanes of the finished impeller are

preserved.

This annular insert could be made also by a single piece. See below.

In a preferred embodiment, the annular insert comprises, preferably

and advantageously, a first face, a second face, a plurality of shaped slots,

and an axial hole.

The first face is configured to reproduce the upper surface of the

annular assembly of all the aerodynamic vanes of the finished impeller; the

second face is substantially opposite to the first face and configured to

reproduce the lower surface of the aforesaid annular assembly; the plurality

of shaped slots are provided to reproduce substantially the lateral walls of the

vanes; and the an axial hole reproduces substantially the axial hole of the

finished impeller in which a rotor of the turbomachine is placed.

Advantageously, the aerodynamic vane insert and the annular insert

can be made by an appropriate material according to the fabrication process

or the type of finished impeller, and it could be a soluble or breakable

material, a reformable material, or a solid material that can be extracted in

multiple pieces, such as - but not limited to - metal, ceramic, polymer, wood,

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or wax. Some specific examples include water soluble ceramics (for example

Aquapour™ from Advanced Ceramics Manufacturing), state-change materials

(for example "Rapid Reformable Tooling Systems" from 2Phase

Technologies), shape memory polymers (for example Veriflex® Reusable

Mandrels from Cornerstone Research Group).

An advantage of the aerodynamic vane inserts and the annular insert

according to the present invention is that they are able to build a finished

impeller of high quality and with innovative characteristics for the

turbomachinery field.

Another advantage is that they are extremely versatile, because it is

possible to make many different types of aerodynamic vanes providing a

specific geometry and shape thereof, for example impeller of tw o or three

dimensional types, or others.

Still another advantage is - in general - that the finished impeller could

be made in a single injection and does not require subsequent assembly and

bonding. This reduces manufacturing time and improves the struc tural

integrity of the part. However, it does not excluded injecting and curing each

vane individually and then combining these vanes in a subsequent step with

the hub and shroud.

According to a fifth aspect, there is a method for building a centrifugal

impeller for a turbomachine, that comprise at least a step to fabricate an

annular insert comprising a plurality of aerodynamic vane inserts reproducing

the aerodynamic vanes of the finished impeller such that the aerodynamic

characteristics of the vanes and the finished impeller are preserved.

The aerodynamic vanes are the empty spaces between two adjacent

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blades through which the working fluid can flow when the impeller is

working See also the description before.

In an advantageous embodiment of the invention, this method

comprises a step to build a plurality of aerodynamic vane inserts made by

said appropriate material, each of them reproducing at least an aerodynamic

vane of the impeller and each configured to associate with each other to

realize the annular insert.

In an alternative embodiment of the invention, it provides a step to

build the annular insert from a single piece using a specific mold.

In another embodiment of the invention, it provides a step to build a

first fabric element able to be associated around each of the said aerodynamic

vane inserts.

In yet another embodiment, another step is provided to build a second

fabric element able to be associated on an upper wall of a vane and on a

lower wall of the adjacent vane of the annular insert.

More, other steps are provided to build a third fabric element able to

form continuously a plurality of blade walls and a wall between the blades.

It’s clear however that there could be a lot of ways to build fabric

elements and to associate them on the impeller inserts according to assembly

or application needs.

In another embodiment of the invention, another step is provided to

associate, at least, a shaped component on the external surface of each

aerodynamic vane insert before associating the fabric element on it. In this

way it is possible to enclose the shaped component between the aerodynamic

vane insert and the respective fabric element.

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 In yet another embodiment of the invention, another step is provided to

associate an inner core under the annular insert in order to give a higher

strength and stiffness during the work of the finished impeller at the high

rotation velocities and, at the same time, to facilitate its construction

providing a solid base for the fibers deployment.

Advantageously, the filling material could be filled inside the mold by

an infusion process, such as resin transfer molding (RTM), vacuum assisted

resin transfer moldling (VARTM), structural reaction injection molding

(SRIM), reinforced reaction injection molding (RRIM), or others. It’s clear

that it does not exclude using other methods according to specific needs of

construction or use.

In another preferred embodiment, another step is provided to remove

the annular insert after the infusion and curing process of the filling material;

this could be achieved by flushing with liquid or gas, in the case of a soluble

insert, heating, in the case of meltable insert, breaking, in the case of

breakable insert, or designing the geometry of the annular insert such that it

can be removed without change, in the case of solid insert. Anyhow, this

removing step is such that the annular insert could be extracted or dissociated

from the finished impeller after the infusion process in such a way that the

aerodynamic characteristics of the vanes of the finished impeller are

preserved.

In another preferred embodiment, still another step is provided to

fabricate all or portions of the aerodynamic vane inserts and of the annular

insert using an additive manufacturing technique to minimize the need for

machining the inserts. These additive manufacturing methods include, but are

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 not limited to, stereolithography, fused deposition modeling, laser sintering,

and electron beam melting. The choice of method will depend on many

factors including the molding temperature and desired dimensional tolerances

of the impeller. This is especially attractive for applications where small

quantities of impellers with the same shape will be produced.

In yet another preferred embodiment, all or portions of the insert

would be cast using dies made with one of the additive manufacturing

methods mentioned above. In this case, the insert material could consist of a

ceramic that is soluble.

An advantage of the method according to the invention is that the

finished impeller produces by the method is of high quality and has the

aforesaid innovative characteristics for the turbomachinery field.

Another advantage is that it is particularly easy to provide further

phases to add components or elements to improve the quality or t he

mechanical characteristics of the finished impeller according to specific

requirements.

A further advantage is that this method is extremely versatile, because

it is possible to built different types of impellers preserving aerodynamic and

mechanical characteristics thereof, for example two or three dimensional

impeller or others.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more apparent by following the description and

the accompanying drawings, which show schematically and not in scale non -

limiting practical embodiments. More specifically, in the drawings, where the

same numbers indicate the same or corresponding parts:

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 Figures 1A, 1B and 1C show cross-sections of an impeller according

to different embodiments;

Figure 2 shows an exploded assembly of a mold according to one

embodiment of the invention;

Figure 3 shows a lateral and exploded view of a mold similar to

Fig.2;

Figure 4 shows a component for the mold of Fig.3;

Figures 5 and 6 show a plurality of views of a component of th e mold

of Fig.2 or 3;

Figures 7 and 8 show other components according to particular

embodiments of the invention;

Figures 9A, 9B and 9C show a respective fiber element according to

particular embodiments of the invention;

Figure 10 shows a cross-section of the mold of Figg.2 or 3; and

Figures 11A to 11L show a plurality of fibers used with different

embodiments of the invention.

DETAILED DESCRIPTION

In the drawings, in which the same numbers correspond to the same

parts in all the various Figures, a finished centrifugal impeller for a

turbomachine according to a first embodiment of the invention is indicated

generically with the numeral 10A, see Figure 1A. This impeller 10A

comprises a plurality of aerodynamic vanes 13 formed between aerodynamic

blades 15 made by first fabric elements 1A (see also Fig.9A) and impregnated

with a first filling material M, typically referred to as a "matrix".

It’s clear that the number and the shape of the fabric elements, the

21
aerodynamic blades, and the corresponding vanes will vary depending on the

particular embodiment of the impeller. See description above.

A working fluid enters in the inlet eye of each vane 13 along an

incoming direction A, goes through the vane 13, and goes out from the outlet

eyes of the same vane along a direction B.

A shaped component 19 – shown not to scale in Fig.1A - is disposed

on an inferior wall 13I of the vane 13 between each blade 15 to prevent the

erosion of the working fluid during the work of the impeller 10A. A fourth

fabric element 4 is advantageously provided over the vane 13 having

substantially a centrifugal shroud shape and function. An inner core element

21 is associated under the vanes 13 and could be surrounded by a plurality of

further fabric elements 5, 6, 7. See description below.

In the embodiment, (see also description of the Fig. 7) this shaped

component 19 reproduces substantially the shape of the inferior walls 13I of

the vane 13 where the erosion process caused by the flow of the working fluid

could be higher; however it’s not to exclude that these components 19 could

be made with another shape or other materials. See description below.

The Fig.1B shows a second embodiment in which an impeller 10B is

provided with a second fabric element 1B (see also descripti on of Fig.9B)

configured to surround alternately an upper wall of a vane 13 and a lower

wall of an adjacent vane 13 passing along the respective blade 15

therebetween.

The Fig.1C shows a third embodiment in which an impeller 10C is

provided with a third fabric element 1C (see also description of Fig.9C)

configured to form the blades 15 and a superior wall 13S of the vane 13

22
between each blade 15; this third fabric element 1C is composed substantially

by an annular plate with a plurality of shaped sheets st retching out from the

plate to form the blades.

In both of the embodiments 10B and 10C could be provided the same

elements described for in the first embodiment of Fig.1A, as shown in the

Figures themselves, as the shaped component 19, the inner core 21, and

others.

In Fig.2 is shown an exploded view of a mold 100 to build said

centrifugal impeller 10A, 10B or 10C which comprises basically an annular

insert 110 (shown itself in exploded view in this Figure) and the inner core

element 21 between a base plate 113 and an upper-ring 115.

The annular insert 110 is made, in this particular embodiment, by

associating a plurality of aerodynamic vane inserts 200, each of them

reproducing an aerodynamic vane 13 of the finished impeller, to form an

assembly substantially annular or toroidal. See below.

The base plate 113 has an internal face 113A configured to reproduce a

rear-surface of the finished impeller 10A, 10B or 10C and an external face

113B being substantially opposite to the internal face 113A. The upper -ring

115 has an internal face 115A configured to reproduce a front -surface of the

impeller and an external face 115B substantially opposite to the internal face

115A.

The inner core element 21 is associated under the annular insert 110

and presents a first face 21A (see also Figg.2, 3 and 9), an opposed second

face 21B and an axial hole 21C. The first face 21A has advantageously a

shroud form, similar to a bell, or a tulipan configured to match the inferior

23
surface of the preform 110; the opposed second face 21B is configured to

reproduce substantially the rear-surface of the finished impeller and the axial

hole 21C is able to be associated on a shaft R of a machine where the finished

impeller can be installed.

In this drawing, the core element 21 is surrounded by a fifth fiber

element 5, a sixth fiber element 6, and a seventh fiber element 7. See below.

It has to be noted that in these drawings the shape of the core element

21 is presented to fill completely the space between the shaft and the perform

110; it does not exclude realizing the core element 21 to fill partially this

space in order to decrease the stress and at the same time the weight of the

finished impeller.

In another advantageous embodiment, these further fabric elements 5,

6 or 7 could be not provided when the core element 21 is made by metallic

material.

Moreover, shaped cavities or holes could be provided on the core

element 21 made by metallic material and inserted with part of the fabric

elements to fix more stably these elements on it.

Moreover, in Fig.2 it is shown a closure system 119 comprises - in this

advantageous embodiment - a plurality of closure pins 119A fixed on the

edge of the internal face 113A of the base plate 113 and with corresponding

closure holes 119B made on the edge of the internal face 115A of the upper-

ring 115; insertion holes 119C are provided on each aerodynamic vane insert

200 in a particular position, see description below.

It’s clear that the closure system 119 is described here as an example

of a realization; this system can vary enormously depending on the particular

24
embodiment.

In Fig.2 it is shown furthermore an axial insert 121 to form the axial

hole 21C of the finished impeller made with a specific material, eventually

the same material of the perform 110 and/or of the inserts 200.

It has to be noted that Fig.2 shows also a plurality of first fabric

elements 1A, each of them associated on the external surface of a respective

aerodynamic vane insert 200; it’s clear that the mold 100 could comprise also

the second and third fabric element 1B and respectively 1C (not shown in

Fig.2 for simplicity) to realize the finished impeller shown schematically in

Fig.1B and respectively 1C.

Fig.3 shows an exploded and lateral view of a mold similar to that of

Fig.2 in which the inserts 200 are associated together to form the annular

insert 110. In this Figure it is not shown the first fabric element 1A nor the

second or third fabric element 1B and 1C for simplicity.

More, in this drawing is shown the forth, fifth and sixt h fabric

elements 4, 5, 6 that could be provided inside the mold 100 to form the

finished impeller in an advantageous embodiment of the invention.

In particular, the fourth fabric element 4 is configured to be associated

between the annular insert 110 and the upper-ring 115; the fifth fabric

element 5 is configured to be associated between the core 21 and the internal

face 113A of the base plate 113; the sixth fabric element 6 is configured to

be associated between the annular insert 110 and the core 21; t he seventh

fabric element 7 is configured to be associated inside the axial hole 21C of

the core 21. These fabric elements 4, 5, 6, 7 could be impregnated with the

first filling material M during the manufactruing process.

25
 Moreover, in Fig.3 it is also shown the annular insert 110 partially in

section and configured to reproduce an annular assembly of a plurality of

aerodynamic vanes of the finished impeller such that the aerodynamic

characteristics of the finished impeller are preserved.

In a preferred embodiment here described, the annular insert 110

comprises a first face 110A made by the upper surface of the vanes annular

assembly and having substantially a form similar to a bell or a tulipan, and

able to be matched with the fourth fabric element 4. A se cond face 110B is

substantially opposite to the first face 110A and made by the lower surface of

the vanes annular assembly; a plurality of shaped slots 137 are provided to

reproduce substantially the blades 15 of each vane 13 and the axial hole 21C

being able to be associated to the rotor R of the turbomachine.

This annular insert 110 could be made by joining to each other a

plurality of said aerodynamic vane inserts 200 (as shown in these Figures) or

by a single piece, as said above.

In Fig.4 it is shown schematically a segmented fabric element 37 (see

also Fig.1A) able to be fitted inside the space at the corner of said shaped

slots 137 to increase the rigidity of the whole assembly of the finished

impeller, eliminate preferential flowpaths for the filli ng material, and avoid

regions containing only filling material with no fiber where cracking might

initiate during cure.

In a preferred embodiment, all the fabric elements 1 to 7 and 37 are

made by fabric material that present soft or (semi) rigid featur es, so they

could be made separately and associated together during the mold

assembling. The fabric material however could be made by other types

26
according to different embodiments or needs of use of the finished impeller.

Moreover, these fabric elements could be made of different types of fiber

material according to different embodiments, see below.

In Figg.5 and 6 it is shown schematically the aerodynamic vane insert

200 according to an advantageous embodiment of the invention, in which it

comprises a central region 200A configured to reproduce a vane 13 of the

finished impeller and opposite shaped end regions 200B, 200C configured to

be associated with shaped end regions 200B and respectively 200C of an

adjacent vane insert 200 to arrange the annular assembly realizing the annular

insert 110. In particular, the end regions 200B, 200C comprise a lateral

surfaces 200D and respectively 200E are able to engage with the lateral

surfaces 200D and respectively 200E of the adjacent vane insert 200.

Advantageously, the opposite shaped end regions 200B, 200C

reproduce the inlet eye and respectively the outlet eye of the vane 13.

Moreover, in this particular embodiment, the end regions 200B, 200C

are shaped in order to match with end regions of an adjacent insert 200 and,

at the same time, for handling and positioning the vane insert 200 within the

mold 100.

It’s clear that the form and the shape of these end regions 200B, 200C

could be changed according to the particular embodiments of the invention.

It has to be noted that the vane insert 200, shown here, represents a

three-dimensional vane; but it’s clear that this insert 200 could be made

according to other different types, for example a two-dimensional vane or

other.

In Fig.7 it is shown schematically the aforesaid shaped element 19

27
according to an advantageous embodiment of the invention, able to cover just

the portion of a vane 13 of the finished impeller where the erosion process is

higher, for example the bottom part thereof (see Fig.1A).

In particular, this shaped element 19 is realized by a first surface S1

able to reproduce the shape of and to be associated on the inferior wall 13I of

a vane 13, see also Fig.1A; and by lateral edges S2 and S3 to reproduce

partially the shape of and to be associated on the lateral walls of the blades

15 inside the vane 13. Advantageously, this shaped element 19 can be

associated on the central region 200A of the vane insert 200 and enclosed by

the first, second or third fabric elements 1A, 1B or 1C, see also Figg.5 and 6.

In Fig.8 it is shown a different embodiment with respect to Fig.7 in

which a shaped component 20 is able to coat or cover completely the walls of

the vane 13; in other words, this shaped component 20 forms substantially a

closed channel able to reproduce entirely the vane 13 in which the working

fluid flows.

In particular, this shaped element 20 is realized by a first inferior

surface L1 able to reproduce the shape of and to be associated on the inferior

wall 13I of a vane 13; by lateral edges L2 and L3 to reproduce the shape of

and to be associated on the lateral walls of the blades 15 inside the vane 13

and by a second superior surface L4 to reproduce the shape of and to be

associated on the superior wall 13S of a vane 13.

At the same time, this shaped element 20 can be associated on the

central region 200A of the insert 200 and enclosed by the first, second or

third fabric element 1A, 1B or 1C.

These shaped elements 19, 20 could be made by a material resistant to

28
erosion or corrosion (as for example metal or ceramic or polymers or other)

and can also be used to further increase the mechanical resistance of the

finished impeller.

It’s clear that the shaped elements 19, 20 have to reproduce the shape

of the vane, so they could be of the three or two dimensiona l types, or other

types according to the shape of the particular vane in which they have to be

associated.

It has to be noted that the shaped elements 19, 20 can be fixed inside

the vane 13 by the filling material M and also by its shaped form in a simple

and useful way.

Fig.9A shows the first fiber element 1A (see also Fig.1A) that presents

a shape reproducing approximately the shape of the vane 13. In this case, this

element 1A could be made by any type of fibers – as described before – and

it could be advantageously semi-elastic or conformable so as to enlarge itself

to pass over the end regions 200B or 200C of the insert 200 and then to close

around the central region 200A. It is clear that, in a further embodiment, the

insert 200 could not include the end regions 200B, 200C. In another

embodiment, the element 1A could be braided, or otherwise produced,

directly onto the insert 200, so no fabric deformation would be required.

Fig.9B shows the second fiber element 1B (see also Fig.1B) that

presents a shape configured to surround alternately the superior wall 13S of

the vane 13 and the inferior wall 13I of an adjacent vane 13 passing along the

respective blade 15 therebetween. In particular, this second element 1B is

made substantially by a shroud plate shaped so as to form continuously all the

vanes 13 of the annular assembly placing a vane insert 200 and the adjacent

29
vane insert 200 opposed on its surface during the assembly of the mold 100.

Fig.9C shows the third fiber element 1C (see also Fig.1C) t hat presents

a configuration substantially made by an annular plate to form the superior or

inferior wall 13S or 13I with blade surfaces stretching out from this plate to

form the blade 15 of the finished impeller; this third fabric element 1C can be

placed substantially above the annular insert 110 (as shown in Fig.9C) or

under the annular insert 110 (as shown in Fig.1C) during the assembly of the

mold 100.

In Fig.10 it is shown schematically a cross-section of the mold 100 of

Figg.2 and 3, in which you can see in particular the vane inserts 200 and the

empty spaces inside which is contained the aforesaid fabric elements 1 to 7

and in which the filling material M is filled.

In a particularly advantageous embodiment, the empty spaces are made

so as to match or press together the fabric elements 1 to 7 placed inside so

that the adjacent fabric elements are strictly in contact each other.

In this way it is possible to decrease the empty spaces between two

adjacent fiber elements 1 to 7 as much as possible; the filling material M

being able to fill the spaces between fibers of the same fiber element 1 to 7 in

order to provide a high, and controlled, fiber volume fraction, see above; in

particular, using a closed mold it is possible to control these spaces to

provide a high, and controlled, fiber volume fraction.

The filling material M can be injected from a plurality of injection

holes 123 made in the base plate 113 and/or in the upper -ring 115.

In the Figg.11A to 11L there are shown a plurality of fibers that can be

used to make the fiber elements 1A, 1B, 1C, 4, 5, 6,7 or 37 according to

30
different embodiments of the invention.

In particular, shown in Fig.11A is a composite material comprising the

filling material M inside which are enclosed a plurality of continuous fibers

R2 which may be oriented in a preferential direction in order to have optimal

strength distribution on the fiber elements during the use of the finished

impeller.

In Figg.11B and 11C are shown composite materials composed of the

filling material M inside which are enclosed a plurality of particle fibers R3

and respectively discontinuous fibers R4.

In Figg.11D to 11L are shows respectively fibers composed of a

biaxial mesh R5, a sewed mesh R6, a tri-axial mesh R7, a multilayer warping

mesh R8, a three-dimensional twister fiber R9, a cylindrical three-

dimensional mesh R10 and respectively a three-dimensional interwoven mesh

R11. All these types of fibers or mesh can be variously oriented in order to

have optimal strength distribution on the fiber elements.

It has to be noted that over the years many types of synthetic fibers

have developed presenting specific characteristics for particular applications

that can be used according to the particular embodiments.

For example, the Dyneema ® (also known as "Gel Spun Polyethylene,

or HDPE) of the Company "High Performance Fibers b.v. Corporation” is a

synthetic fiber suitable for production of cables for traction, and it is used for

sports such as kite surfing, climbing, fishing and the production o f armors;

another fiber similar to the Dyneema is the Spectra ® patented by an U.S.

Company; and another fiber available on the market is the Nomex ®, a meta -

aramid substance made in the early sixties by DuPont.

31
 The disclosed exemplary embodiments provide objects and methods to

realize an impeller with innovative features. It should be understood that this

description is not intended to limit the invention. On the contrary, the

exemplary embodiments are intended to cover alternatives, modifications and

equivalents, which are included in the spirit and scope of the invention as

defined by the appended claims. Further, in the detailed description of the

exemplary embodiments, numerous specific details are set forth in order to

provide a comprehensive understanding of the claimed invention. However,

one skilled in the art would understand that various embodiments may be

practiced without such specific details.

Although the features and elements of the present exemplary

embodiments are described in the embodiments in particular combinations,

each feature or element can be used alone without the other features and

elements of the embodiments or in various combinations with or without

other features and elements disclosed herein.

This written description uses examples to disclose the invention,

including the best mode, and also to enable any person skilled in the art to

practice the invention, including making and using any devices or systems

and performing any incorporated methods. The patentable scope of the

invention is defined by the claims, and may include other examples that occur

to those skilled in the art. Such other example are intended to be within the

scope of the claims if they have structural elements that do not differ from the

literal language of the claims, or if they include equivalent structural

elements with insubstantial differences from the literal languages of the

claims.

32
 CLAIMS
1. A centrifugal impeller for a turbomachine comprising aerodynamic vanes

(13), characterized in that each of them (13) comprises internal walls on which is

associated a fabric element (1A; 1B; 1C; 4; 5; 6; 7; 37) , wherein a second fabric (1B)

element is alternately associated on an upper wall (13S) of a vane (13) and a lower wall (13I)

of an adjacent vane (13) passing along the respective blade (15) there between.

2. The impeller as claimed in claim 1, wherein the first fabric elements (1A) are

configured to surround each of said aerodynamic vanes (13).

3. The impeller as claimed in claim 1, wherein the second fabric element (1B) is

configured to surround alternately the upper wall (13S) of the vane (13) and the

lower wall (13I) of the adjacent vane (13) as a continuous fabric element passing

along the respective blade (15) there between.

4. The impeller as claimed in claim 1, wherein a third fabric element (1C) has a

conical surface with blades stretching out from said surface.

5. The impeller as claimed in claim 1, wherein the impeller comprises one of the

followings:

- a fourth fabric element (4) associated over said aerodynamic vanes (13); said

fourth element (4) having substantially a centrifugal shroud shape and function;

- a fifth fabric element (5) provided to realize substantially a rear-plate for the

finished impeller; said fifth element (5) having substantially an annular planar

shape;

- a sixth fabric element (6) associated under said aerodynamic vanes (13); said

sixth element (6) having substantially an annular shape able to be matched with

the external inferior surface of said aerodynamic vanes (13);

- a seventh fabric element (7) associated around an axial hole (21C) used to

34
 associate a rotor for the turbomachine;

- a segmented fabric element (37) able to be fitted inside the space at the corner

of shaped slots (115) of the vanes (13) to increase the rigidity of the whole

assembly of the finished impeller, eliminate preferential flowpaths for the filling

material, and avoid regions containing only filling material with no fiber where

cracking might initiate during cure;

- a shaped component (19; 20) associated inside each of said aerodynamic

vanes (13) in order to act against the erosion of the working fluid.

6. The impeller as claimed in claim 1, wherein said fabric elements (1A; 1B; 1C;

4; 5; 6; 7; 39) are impregnated with a filling material (M).

7. The impeller as claimed in claim 1, wherein an inner core element (21) is

associated under said aerodynamic vanes (13) in order to facilitate the

manufacturing process of said impeller.

8. The impeller as claimed in claim 7, wherein said core element (21) is

surrounded by one of the following: said fourth, fifth, sixth, seventh fiber elements

(4; 5; 6; 7).

9. The impeller as claimed in claim 1, wherein said fabric elements (1A; 1B; 1C;

4; 5; 6; 7; 37) are made by unidirectional or multidirectional fibers, realized

substantially to have a high anisotropy along a preferential direction.

Dated this 06th day of March 2019.

Yours faithfully,

Chaitanya Wingkar
Agent for the Applicant [IN/PA -1532]
35
A centrifugal impeller for a turbomachine characterized in that it comprises a plurality of
aerodynamic vanes (13), each of them (13) having internal walls on which is associated a
fabric element (1A; 1B; 1C; 4; 5; 6; 7; 37).
 Clean Copy

Applicant: Nuovo Pignone No. of Sheets: 8

Application Number: 4514/DELNP/2012 Sheet No.: 1

B 13 I
Ú×Ùò ïß 4 10A
13
15
1A
19 13
15
13S
13
A
6
5 1A

21

B 7 19
4
13 I 10B
13
15
19
1B 13
13S 15 4
B
13 10C
A 13 I
6 13
15 Ú×Ùò ïÝ
5 1B 19 1C
21 13
13S 15
19 13
7 A
6

Ú×Ùò ïÞ 5
21

7 19

Patent Agent Name: Chaitanya Wingkar

Reg. No.: IN/PA- 1532
 Clean Copy

Applicant: Nuovo Pignone No. of Sheets: 8

Application Number: 4514/DELNP/2012 Sheet No.: 2

FIG. 2
121
115B 123

115
119B

ì 110
115A

119C
ì
200C 1A

200B

21C 6
200
21A

21
5
21B
113A

113

119A

113B
123

Patent Agent Name: Chaitanya Wingkar

Reg. No.: IN/PA- 1532
 Clean Copy

Applicant: Nuovo Pignone No. of Sheets: 8

Application Number: 4514/DELNP/2012 Sheet No.: 3
121

115
115B 119B

115A

200C
110
200A 137
FIG. 3 110A
119C

110B
200B 200B
6

37

21C
21
21A
FIG. 4
21B 5
7 119A
113A
113

Patent Agent Name: Chaitanya Wingkar

Reg. No.: IN/PA- 1532
 Clean Copy

Applicant: Nuovo Pignone No. of Sheets: 8

Application Number: 4514/DELNP/2012 Sheet No.: 4

200E 200C
200

1A 200E
119C
200D

200A

19 FIG. 5
200A
200B 200D

200D
119C

200B FIG. 6

200D 200A

1A 19

200
200E

200E 200C

Patent Agent Name: Chaitanya Wingkar

Reg. No.: IN/PA- 1532
 Clean Copy

Applicant: Nuovo Pignone No. of Sheets: 8

Application Number: 4514/DELNP/2012 Sheet No.: 5

S2
19

S3

S2
FIG. 7

S3
S1

L1
L3
L2
20

L4

L2

FIG. 8
L1 L3

Patent Agent Name: Chaitanya Wingkar

Reg. No.: IN/PA- 1532
 Clean Copy

Applicant: Nuovo Pignone No. of Sheets: 8

Application Number: 4514/DELNP/2012 Sheet No.: 6
A

FIG. 9A
1A

200A

A A
1B
FIG. 9B

15

B
15

B
B 200A
A
A
FIG. 9C 1C

15

B 200A
B

Patent Agent Name: Chaitanya Wingkar

Reg. No.: IN/PA- 1532
 Clean Copy

Applicant: Nuovo Pignone No. of Sheets: 8

Application Number: 4514/DELNP/2012 Sheet No.: 7

200B

B
123

119A

4
115
200C

61A-1B-1C
A
121
21

7
A
200C

5
200

123
119A
FIG. 10

113
115

200B
B

Patent Agent Name: Chaitanya Wingkar

Reg. No.: IN/PA- 1532
 Clean Copy

Applicant: Nuovo Pignone No. of Sheets: 8

Application Number: 4514/DELNP/2012 Sheet No.: 8

FIG. 11B FIG. 11C

FIG. 11A

M M
M R2 R4
R3

M
R6

R5
FIG. 11D FIG. 11E
M R8

R7
M

FIG. 11F FIG. 11G

R11
R9 R10

M
M
FIG. 11H FIG. 11I FIG. 11L

Patent Agent Name: Chaitanya Wingkar

Reg. No.: IN/PA- 1532
 Marked copy

FORM 2
THE PATENTS ACT 197
(39 of 1970)

THE PATENTS (AMENDMENT) RULES, 2006

COMPLETE SPECIFICATION
(See section 10 and rule 13)

l . TITLE OF THE INVENTION

Centrifugal Impeller And Turbomachine

2. APPLICANT

NAME Nuovo Pignone S.p.A.

NATIONALITY IT
ADDRESS Via Felice Matteucci, 2 50127 Florence (IT)

3. PREAMBLE TO THE DESCRIPTION

COMPLETE

The following specification particularly describes the invention and the manner in which it is to be
performed.

1
 DESCRIPTION
TECHNICAL FIELD

Embodiments of the subject matter disclosed herein generally relate to

composite centrifugal impellers for turbomachines and related production

methods, particularly, but not exclusively, for oil and gas app lications.

Other Embodiments generally relates to a mold for producing this

centrifugal impeller, some particular components to make this centrifugal

impeller with this mold, and a turbomachine in which said impeller could be

used.

BACKGROUND ART

A component of a centrifugal turbomachine is the centrifugal impeller,

which transfers, in general, energy from the motor that drives the

turbomachine to a working fluid being compressed or pumped by accelerating

the fluid outwards from the center of rotation; the kinetic energy imparted by

the impeller to the working fluid is transformed into pressure energy when

the outward movement of the fluid is confined by a diffuser and the machine

casing. This centrifugal machine is called, in general, a compressor (if the

working fluid is gas) or a pump (if the working fluid is a liquid).

Another type of centrifugal turbomachine is an expander, which uses

the pressure of a working fluid to generate mechanical work on a shaft by

using an impeller in which the fluid can be expanded.

US 4,676,722 describes a wheel for a centrifugal compressor made by

a plurality of fiber loaded scoops. A disadvantage of this particular impeller

is that the various scoops have direct fiber reinforcement substantially in the

radial direction, so it is difficult to balance circumferential stress as

2
generated by centrifugal forces at a high speed of rotation. After

manufacturing, the sectors are joined to each other by the adhesive strength

of a bonding agent, which limits the maximum speed of oper ation. Also, the

method of manufacture, in which the assembly is drawn into place by

filaments, is restricted to relatively simple geometries (e.g. with straight -

edged sectors) which may have low aerodynamic efficiency.

US 5,944,485 describes a turbine of thermo-structural composite

material, particularity one of large diameter, and a method for manufacturing

the turbine that provides mechanical coupling for its assembly by means of

bolts, grooves, slots, and so on. A disadvantage of this impeller is that the

mechanical coupling cannot ensure a high resistance at high rotational

velocity when using either a corrosive or erosive working fluid. Therefore the

reliability of this component may decrease dramatically. In addition, the

scheme for attaching the airfoil to the hub provides user continuous fibers

around the internal corners of the passages. Since these are typically areas of

high stress, it is desirable to have fibers that are continuous from the airfoil to

the cover and from the airfoil to the hub.

US 6,854,960 describes a segmented composite impeller or propeller

arrangement and a manufacturing method. The main disadvantage of this

impeller is that it relies on adhesive bonding to join identical segments. As a

result, it does not have a high mechanical resistance to work at high rotational

velocity, and centrifugal forces can separate identical segments and destroy

the impeller itself. Another disadvantage is that it is not possible to build an

impeller with vanes with complex geometry, as is the case with three

dimensional or similar impellers.

3
 In general, a disadvantage of all the aforesaid impellers is that they

present a relatively complex mechanical structure, because they are composed

of several different components that need to be made indep endently and then

mechanically assembled together. Moreover, the components made of fibers

have to be built in general by expensive metal molds, increasing the cost of

manufacture. Also, different metal molds have to be used to build these fiber

components for each different type of impeller, which significantly increases

the cost of manufacture. Again, these mechanical assemblies are not easily

achievable by means of automated machinery, further increasing the time and

cost of manufacture.

Another disadvantage is that the vanes of these impellers are not

protected in any way from solid or acid particles suspended in the working

flow, therefore erosion and corrosion problems could be significant and may

lead to the destruction of the component.

Yet another disadvantage is that it may be difficult to achieve the

mechanical assembly of all the components needed for optimal operations of

the impeller at high speed. Moreover, any distortion produced by the tensions

and forces created during use can cause problems during operation, especially

at high speed; vibrations may occur during operation, caused by wear and/or

by a faulty assembly of various components. Therefore, the impeller may fail.

To date, notwithstanding the developments in technology, these

disadvantages pose a problem and create a need to produce simple and

inexpensive centrifugal impeller for turbomachinery in an even faster and less

expensive way, while at the same time producing an improved and high

quality finished product. A particular need exists to produce an innovative

4
 centrifugal impeller by taking advantage of composite and fiber technologies,

whilemostly preserving the mechanical, fluid-dynamic and aerodynamic

properties of metallic impeller, in order to effectively use this innovative

impeller in the turbomachinery field. Design improvements are needed to

take greater advantage of the inherent strengths of composites, and to enable

safe operation at higher tip speeds than is possible with typical metallic

impellers.

SUMMARY

An object of the present invention is to produce a simple, fast and

cheap mold for building a centrifugal impeller, overcoming at least some of

the drawbacks mentioned above.

A further object is to develop a method for the production of said

impeller, particularly a method for creating the impeller using composite

material.

A further object is to produce some components to make said impeller

by said mold in an easy and cheap way.

According to a first aspect, there is a centrifugal impeller for a

turbomachine comprising a plurality of aerodynamic vanes; each of these

vanes comprising internal walls on which is associated at least a fabric

element.

In other words, the aerodynamic vanes are the empty spaces between

adjacent blades. During the use of the impeller, in a few words, the working

fluid enters into an inlet eye of each aerodynamic vane, passes through the

vane, in which the fluid is pushed radially by the geometry of the vane itself

and by the rotation of the impeller, and finally goes out through an eye outle t

5
of each vane.

It must be understood that, in this description and in the attached

claims, the term “fabric” is used to imply a number of one or more of a

variety of different fibrous structures woven into a pattern, such as a braid

pattern, a stitched pattern, or an assembly of layers (and not woven

arrangements only). See the descriptions below.

In a particularly advantageous embodiment of the subject matter

disclosed, first fabric elements are configured to surround each aerodynamic

vane in order to substantially reproduce the shape of the aerodynamic vane

such that the aerodynamic characteristics of said vane are preserved. The

fabric comprises fibers that are advantageously and preferably continuous

around the entire internal surface of each vane thereby providing a high

resistance to mechanical stresses generated at these locations. In this way a

single vane becomes particularly resistant to the mechanical stress and at the

same time is able to preserve its aerodynamic characteristics.

In another advantageous embodiment of the invention, a second fabric

element is configured to alternately surround an upper wall of a vane and a

lower wall of an adjacent vane passing along the respective blade

therebetween such that the aerodynamic characteristics of said vane are

preserved.

In another advantageous embodiment, a third fabric element has a

substantially conical surface with fabric blades stretching out from the

surface; these fabric blades being able to reproduce substantially the blades

of the finished impeller..

It is clear that the aforesaid three embodiments could be realized in

6
different ways according to specific needs of manufacturing or use; also, it

does not exclude realizing these embodiments in combinations one to the

other.

In another embodiment, a shaped component is associated inside each

of the aerodynamic vanes in order to act against the erosion or corrosion

phenomena caused by the working fluid.

In fact, the working fluid could be a gas, a liquid or in general a

mixture thereof, and the erosion or corrosion process could be aggravated by

the high rotational speed of the impeller, which causes the liquid or solid

particles in the flow to strike the blade with higher force.

In another advantageous form of implementation, the impeller

comprises a fourth fabric element placed over the aerodynamic vanes; this

fourth fabric element could substantially have a centrifugal shroud shape and

function.

Moreover, the impeller could comprise a fifth fabric element having

substantially an annular planar shape that realizes substantially a rear-plate

for the impeller itself.

A sixth fabric element could be fitted under the aerodynamic vanes;

this element has substantially an annular shape and is able to be matched with

the external inferior surface of the vanes.

A seventh fabric element could be advantageously fitted around an

axial hole inside which a rotor of the turbomachine fits. The fourth, fifth,

sixth and seventh fabric elements could be provided, preferably in

combination one to the other, to increase the mechanical resistance of the

finished impeller; however, it must be understood that these fabric elements

7
could be used alone or in various combinations according to the specific

needs of manufacturing or use.

In an advantageous embodiment, all the aforesaid fabric elements –

when provided – are enclosed or associated in the filling material, typically

called “matrix”, in order to obtain a more rigid shape for the impeller.

In a particularly advantageous embodiment, all of the aforesaid fabri c

elements – when provided – are matched or pressed together in order to

minimze the empty spaces between them. In this case, the filling material

used to fill the spaces between adjacent fiber elements is reduced as much as

possible, in order to maximize the amount of structural fiber within the

volume. This will further increase the mechanical resistance of the finished

impeller.

In a further advantageous embodiment, an inner core element is placed

under the aerodynamic vanes in order to facilitate the manufacturing process

of the impeller, in particular to facilitate the deposition of the said fourth,

fifth, sixth, and seventh fiber elements in place, and, when provided,

providing a base for the fiber deployment. Also, the core element could be

configured advantageously to give a higher strength and stiffness during the

work of the finished impeller at high rotational velocities.

The core could be made at least by a material more rigid than the

filling material before it’s cured, for example: wood (for example balsa),

foam (for example epoxies, phenolics, polypropelyne, polyurethane,

polyvinyl chloride PVC, acrylonitrile butadiene-styrene ABS, cellulois

acetate), honeycomb (for example kraft paper, aramid paper, carbon or glass

reinforced plastic, aluminum alloys, titanium, and other metal alloys),

8
polymers (for example phenolics, polyimides, polyetherimides,

polyetheretherketones), or metallic materials or others.

In particularly advantageous embodiments, the core consists of

unfilled cavities that decrease the overall density of the core, so that it is

substantially lower than that of the fabric or filling material. This will result

in lower forces on the adjacent structure when subjected to high rotational

velocities.

In particular embodiments, the core could be surrounded, in part, by at

least one of the aforesaid fabric elements - alone or in various combinations,

when provided – in order to obtain a particularly compact, rigid and resistant

system.

According to a preferred embodiment of the invention, the above

fabric elements are made by a plurality of unidirectional or multidirectional

fibers, realized substantially to have a high anisotropy along at least a

preferential direction. These fibers could have a substantially thread -like

shape, as for example carbon fibers, glass fibers, quartz, boron, basalt,

polymeric (such as aromatic polyamide or extended-chain polyethylene)

polyethylene, ceramics (such as silicon carbide or alumina) or others.

It does not exclude, however, that these fabric elements could be

realized with two or more layers of fibers, with a combination of fibers of

different types or with different types of elements, as for example with

granular, lamellar or spheroidal elements or woven, stitched, braided, non -

crimp or other fabrics, unidirectional tapes or tows, or any other fiber

architectures. .

The above filling material could be realized by a material able to hold

9
together, to evenly distribute the tensions inside, and to provide high

resistance to high temperatures and wear for the fabric elements; on the

contrary, the fabric elements are able mainly to provide high resistance to the

tensions during the work of the impeller. Moreover, the filling material can

be arranged to present a low specific mass or density in order to r educe the

weight of the impeller and thus the centrifugal force generated during the

work.

The filling material could be preferably an organic, natural or

synthetic polymer material, whose main components are polymers with high

molecular weight molecules, and which are formed by a large number of

basic units (monomers) joined together by chemical bonds. Structurally, these

molecules may be formed from linear or branched chains, tangled with each

other, or three-dimensional lattices, and mainly composed of carbon and

hydrogen atoms and, in some cases, oxygen, nitrogen, chlorine, silicon,

fluorine, sulfur, or others. In general, polymeric materials are a very large

family of hundreds and hundreds of different substances.

One or more auxiliary compounds can also be added to the polymer

materials, such as micro- or nanoparticles, which have different functions

depending on the specific needs, for example to strengthen, toughen,

stabilize, preserve, liquefy, color, bleach, or protect the polymer from

oxidation.

In an advantageous form of implementation of the invention, the

polymer filling material is constituted, at least in part, from a thermoplastic

polymer such as PPS (polyphenylene sulphides), PA (polyamide or nylon),

PMMA (or acrylic), LCP (liquid crystal polymer), POM (acetal), PAI

10
(polyamide imide), PEEK (poly-ether-ether-ketone), PEKK (poly-ether-

ketone-ketone), PAEK (poly-aryl-ether-ketone) , PET (Polyethylene

tereptalato), PC (poly carbonate), PE (polyethylene), PEI (Poly -ether-imide),

PES (polyether), PPA (poliptalamide), PVC (polyvinyl chloride), PU

(polyurethane), PP (polypropylene), PS (polystyrene), PPO (polifenilene

oxide), PI (polyimide; exist as thermosetting), or more. For particularly high

temperature applications various polyimides such as polymerized monomeric

reactant (PMR) resins, 6F-Polyimides with a phenylethynyl endcap (HFPE),

and phenylethynyl-terminated imide (PETI) oligomers may be preferred.

In another advantageous form of implementation of the invention, the

polymer filling material is at least partly constituted of a thermosetting

polymer, such as Epoxy, phenolic, polyester, vinylester, Amin, furans, PI

(exist also as thermoplastic material), BMI (Bismaleimides), CE (cyanate

ester), Pthalanonitrile, benzoxazines or more. For particul arly high

temperature applications various thermosetting polyimides such as

polymerized monomeric reactant (PMR) resins, 6F-Polyimides with a

phenylethynyl endcap (HFPE), and phenylethynyl-terminated imide (PETI)

oligomers may be preferred.

According to another advantageous embodiment of the invention, the

filling material is composed of a ceramic material (such as silicon carbide or

alumina or other) or even, at least in part, from a metal (such as aluminum,

titanium, magnesium, nickel, copper or their alloys), carbon (as in the case of

carbon-carbon composites), or others.

An advantage of the impeller created according to the invention is that

it presents high quality and innovative characteristics.

11
 In particular, the impeller is extremely light while, at the same time,

has a comparable resistance with respect to the known impeller made of metal

used in the turbomachine field (for high rotational velocity and for high

pressure ratio).

In fact, a traditional metallic impeller could weigh from about 10 to

2000 kg depending on the impeller size, and the impeller according to the

invention could weigh from about 0.5 to 20 kg (for the same type of

impeller). Therefore, the weight reduction is greater than 75%.

Another advantage is that an impeller made according to the invention

could be used with a lot of different fluids (liquid, gas or a mixture thereof)

and with fluids that present high corrosive or erosive characteristics.

A further advantage is comes from the fact that it is particularly

inexpensive and simple to produce and to handle. See description below.

Another advantage is that it is particularly easy to apply more

components or elements to improve the quality or the mechanical

characteristics of the impeller according to specific requirements, like t he

shaped components or fiber elements made by specific shape or other.

Again, another advantage is that an impeller made according the

present invention could be of different types, preserving at the same time

aerodynamic and mechanical characteristics For example, the impeller could

be a three dimensional impeller, a two dimensional impeller, or others.

According to a second aspect, there is a turbomachine wherein at least

a centrifugal impeller as described above is implemented.

In particular, this turbomachine could be a centrifugal compressor (for

gas) or pump (for liquid), or else it could be a centrifugal expander; in any

12
case, the turbomachine has preferably a plurality of these impellers associated

on a common shaft in metal or other material (for example a composite

material).

According to a third aspect, there is a mold to build a centrifugal

impeller for a turbomachine comprising of, at least, an annular insert

comprising a plurality of aerodynamic vane inserts reproducing the

aerodynamic vanes of the finished impeller.

In particular, the annular insert could be made by a single piece or,

preferably, by joining together a plurality of pieces, see below.

The mold comprises preferably and advantageously a base plate having

an internal face and an external face, the internal face being configured to

reproduce a rear-surface of the impeller and the external face being

substantially opposite to the internal face; an upper-ring having an internal

face and an external face, the internal face being config ured to reproduce a

front-surface of the impeller and the external face being substantially

opposite to the internal face.

In other embodiments, the mold comprises the aforesaid fabric

elements having preferably and advantageously a (semi) rigid shape and

being made separately before placed inside the mold.

In a particularly advantageous embodiment of the invention, the mold

comprises the inner core associated under the centrifugal impeller preform

and over the base plate; the inner core could be realized in numerous different

embodiments according to different technical needs or requirements of use.

See below.

In another advantageous embodiment of the invention, the mold

13
comprises a plurality of shaped components able to be associated on an

external surface of each aerodynamic vane insert; these shaped components

are configured to act against the erosion or corrosion of the working fluid

during the work of the finished impeller.

In particular, these shaped components could be associated between

one of the aforesaid fabric elements and the surfaces of the annular insert

corresponding to the walls of the vanes, in a position where the erosion or

corrosion process caused by the working fluid is higher.

A closure system could be provided to close the preform between the

base-plate and the upper/ring, in order to center and lock said impeller

preform between them. This system could be realized in a plurality of

different types, for example in a mechanical system (centering pins, screws or

others), a geometrical system (shaped holes, shaped grooves, shaped teeth,

shaped surfaces or others), or others systems.

An injection system is provided to inject the filling material inside the

mold by means of injection channels made inside the base plate and/or the

upper-ring.

An advantage of the mold according to the present invention is that the

finished impeller the mold produces is high quality and has innovative

characteristics for the turbomachinery field.

Another advantage is that the material used for the annular in sert could

be something low-cost and easy to machine, such as high-density foam or

ceramic.

Moreover, the material is very compact and yet extremely versatile,

because it is possible to make a lot of different types of impellers providing

14
an annular insert with specific geometry and shape (in particular three or two

dimension impellers).

Yet another advantage of the mold design is that it allows a single –step

infusion and cure of the filling material through the entire part. This provides

for a high strength part and eliminates the need for secondary joining

operations such as bonding, machining, or mechanical attachment which can

be costly and time-consuming. In addition, the possibility for part

contamination or handling damage between operations is eli minated.

According to a fourth aspect, there is an aerodynamic vane insert

configured to reproduce at least an aerodynamic vane of the finished

centrifugal impeller such that the aerodynamic characteristics of the vane of

the finished impeller are preserved.

Advantageously, the aerodynamic vane insert comprises at least a

central region configured to properly reproduce the aerodynamic vane and

end-regions configured to be associated with end-regions of an adjacent insert

forming the annular assembly.

In a particularly advantageous embodiment, these shaped end-regions

are configured to be associated with end-regions of an adjacent insert in order

to create the inlet and respective outlet eyes for the working fluid and for

handling, positioning the insert within the mold, and containing resin

channels. More, the shaped end-regions could be provided with sealing

elements to avoid a leakage during the injection of the filling material.

In a preferred embodiment, the aerodynamic vane inserts are made by

at least a single piece; however it does not exclude that the inserts could be

made of two or more pieces or, on the contrary, a single insert could produce

15
two or more aerodynamic vanes according to the particular embodiments.

The advantage of this aspect of the invention is that it allows the

fabrication of vanes with complex 3D geometry such that the inserts can

readily be removed from the impeller after the filling material has cured.

According to another exemplary embodiment, an aerodynamic vane

insert is joined with other vane inserts to form an annular assembly

reproducing of all the aerodynamic vanes of the finished impeller such that

the aerodynamic characteristics of the vanes of the finished impeller are

preserved.

This annular insert could be made also by a single piece. See below.

In a preferred embodiment, the annular insert comprises, preferably

and advantageously, a first face, a second face, a plurality of shaped slots,

and an axial hole.

The first face is configured to reproduce the upper surface o f the

annular assembly of all the aerodynamic vanes of the finished impeller; the

second face is substantially opposite to the first face and configured to

reproduce the lower surface of the aforesaid annular assembly; the plurality

of shaped slots are provided to reproduce substantially the lateral walls of the

vanes; and the an axial hole reproduces substantially the axial hole of the

finished impeller in which a rotor of the turbomachine is placed.

Advantageously, the aerodynamic vane insert and the annular insert

can be made by an appropriate material according to the fabrication process

or the type of finished impeller, and it could be a soluble or breakable

material, a reformable material, or a solid material that can be extracted in

multiple pieces, such as - but not limited to - metal, ceramic, polymer, wood,

16
or wax. Some specific examples include water soluble ceramics (for example

Aquapour™ from Advanced Ceramics Manufacturing), state-change materials

(for example "Rapid Reformable Tooling Systems" from 2Phase

Technologies), shape memory polymers (for example Veriflex® Reusable

Mandrels from Cornerstone Research Group).

An advantage of the aerodynamic vane inserts and the annular insert

according to the present invention is that they are able to bui ld a finished

impeller of high quality and with innovative characteristics for the

turbomachinery field.

Another advantage is that they are extremely versatile, because it is

possible to make many different types of aerodynamic vanes providing a

specific geometry and shape thereof, for example impeller of two or three

dimensional types, or others.

Still another advantage is - in general - that the finished impeller could

be made in a single injection and does not require subsequent assembly and

bonding. This reduces manufacturing time and improves the structural

integrity of the part. However, it does not excluded injecting and curing each

vane individually and then combining these vanes in a subsequent step with

the hub and shroud.

According to a fifth aspect, there is a method for building a centrifugal

impeller for a turbomachine, that comprise at least a step to fabricate an

annular insert comprising a plurality of aerodynamic vane inserts reproducing

the aerodynamic vanes of the finished impeller such that the aerodynamic

characteristics of the vanes and the finished impeller are preserved.

The aerodynamic vanes are the empty spaces between two adjacent

17
blades through which the working fluid can flow when the impeller is

working See also the description before.

In an advantageous embodiment of the invention, this method

comprises a step to build a plurality of aerodynamic vane inserts made by

said appropriate material, each of them reproducing at least an aerodynamic

vane of the impeller and each configured to associate with each other to

realize the annular insert.

In an alternative embodiment of the invention, it provides a step to

build the annular insert from a single piece using a specific mold.

In another embodiment of the invention, it provides a step to build a

first fabric element able to be associated around each of the said aerodynamic

vane inserts.

In yet another embodiment, another step is provided to build a second

fabric element able to be associated on an upper wall of a vane and on a

lower wall of the adjacent vane of the annular insert.

More, other steps are provided to build a third fabric element able to

form continuously a plurality of blade walls and a wall between the blades.

It’s clear however that there could be a lot of ways to build fabric

elements and to associate them on the impeller inserts according to assembly

or application needs.

In another embodiment of the invention, another step is provided to

associate, at least, a shaped component on the external surface of each

aerodynamic vane insert before associating the fabric element on it. In this

way it is possible to enclose the shaped component between the aerodynamic

vane insert and the respective fabric element.

18
 In yet another embodiment of the invention, another step is provided to

associate an inner core under the annular insert in order to give a higher

strength and stiffness during the work of the finished impeller at the high

rotation velocities and, at the same time, to facilitate its construction

providing a solid base for the fibers deployment.

Advantageously, the filling material could be filled inside the mold by

an infusion process, such as resin transfer molding (RTM), vacuum assisted

resin transfer moldling (VARTM), structural reaction injection molding

(SRIM), reinforced reaction injection molding (RRIM), or others. It’s clear

that it does not exclude using other methods according to specific needs of

construction or use.

In another preferred embodiment, another step is provided to remove

the annular insert after the infusion and curing process of the filling material;

this could be achieved by flushing with liquid or gas, in the case of a soluble

insert, heating, in the case of meltable insert, breaking, in the case of

breakable insert, or designing the geometry of the annular insert such that it

can be removed without change, in the case of solid insert. Anyhow, this

removing step is such that the annular insert could be extracted or dissociated

from the finished impeller after the infusion process in such a way that the

aerodynamic characteristics of the vanes of the finished impeller are

preserved.

In another preferred embodiment, still another step is provided to

fabricate all or portions of the aerodynamic vane inserts and of the annular

insert using an additive manufacturing technique to minimize the need for

machining the inserts. These additive manufacturing methods include, but are

19
 not limited to, stereolithography, fused deposition modeling, laser sintering,

and electron beam melting. The choice of method will depend on many

factors including the molding temperature and desired dimensional tolerances

of the impeller. This is especially attractive for applications where small

quantities of impellers with the same shape will be produced.

In yet another preferred embodiment, all or portions of the insert

would be cast using dies made with one of the additive manufacturing

methods mentioned above. In this case, the insert material could consist of a

ceramic that is soluble.

An advantage of the method according to the invention is that the

finished impeller produces by the method is of high quality and has the

aforesaid innovative characteristics for the turbomachinery field.

Another advantage is that it is particularly easy to provide further

phases to add components or elements to improve the quality or the

mechanical characteristics of the finished impeller according to specific

requirements.

A further advantage is that this method is extremely versatile, because

it is possible to built different types of impellers preserving aerodynamic and

mechanical characteristics thereof, for example two or three dimensional

impeller or others.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more apparent by following the description and

the accompanying drawings, which show schematically and not in scale non-

limiting practical embodiments. More specifically, in the drawings, where the

same numbers indicate the same or corresponding parts:

20
 Figures 1A, 1B and 1C show cross-sections of an impeller according

to different embodiments;

Figure 2 shows an exploded assembly of a mold according to one

embodiment of the invention;

Figure 3 shows a lateral and exploded view of a mold similar to

Fig.2;

Figure 4 shows a component for the mold of Fig.3;

Figures 5 and 6 show a plurality of views of a component of the mold

of Fig.2 or 3;

Figures 7 and 8 show other components according to particular

embodiments of the invention;

Figures 9A, 9B and 9C show a respective fiber element according to

particular embodiments of the invention;

Figure 10 shows a cross-section of the mold of Figg.2 or 3; and

Figures 11A to 11L show a plurality of fibers used with different

embodiments of the invention.

DETAILED DESCRIPTION

In the drawings, in which the same numbers correspond to the same

parts in all the various Figures, a finished centrifugal impeller for a

turbomachine according to a first embodiment of the invention is indicated

generically with the numeral 10A, see Figure 1A. This impeller 10A

comprises a plurality of aerodynamic vanes 13 formed between aerodynamic

blades 15 made by first fabric elements 1A (see also Fig.9A) and impregnated

with a first filling material M, typically referred to as a "matrix".

It’s clear that the number and the shape of the fabric ele ments, the

21
aerodynamic blades, and the corresponding vanes will vary depending on the

particular embodiment of the impeller. See description above.

A working fluid enters in the inlet eye of each vane 13 along an

incoming direction A, goes through the vane 13, and goes out from the outlet

eyes of the same vane along a direction B.

A shaped component 19 – shown not to scale in Fig.1A - is disposed

on an inferior wall 13I of the vane 13 between each blade 15 to prevent the

erosion of the working fluid during the work of the impeller 10A. A fourth

fabric element 4 is advantageously provided over the vane 13 having

substantially a centrifugal shroud shape and function. An inner core element

21 is associated under the vanes 13 and could be surrounded by a plura lity of

further fabric elements 5, 6, 7. See description below.

In the embodiment, (see also description of the Fig. 7) this shaped

component 19 reproduces substantially the shape of the inferior walls 13I of

the vane 13 where the erosion process caused by the flow of the working fluid

could be higher; however it’s not to exclude that these components 19 could

be made with another shape or other materials. See description below.

The Fig.1B shows a second embodiment in which an impeller 10B is

provided with a second fabric element 1B (see also description of Fig.9B)

configured to surround alternately an upper wall of a vane 13 and a lower

wall of an adjacent vane 13 passing along the respective blade 15

therebetween.

The Fig.1C shows a third embodiment in which an impeller 10C is

provided with a third fabric element 1C (see also description of Fig.9C)

configured to form the blades 15 and a superior wall 13S of the vane 13

22
between each blade 15; this third fabric element 1C is composed substantially

by an annular plate with a plurality of shaped sheets stretching out from the

plate to form the blades.

In both of the embodiments 10B and 10C could be provided the same

elements described for in the first embodiment of Fig.1A, as shown in the

Figures themselves, as the shaped component 19, the inner core 21, and

others.

In Fig.2 is shown an exploded view of a mold 100 to build said

centrifugal impeller 10A, 10B or 10C which comprises basically an annular

insert 110 (shown itself in exploded view in this Figure) and the inner core

element 21 between a base plate 113 and an upper-ring 115.

The annular insert 110 is made, in this particular embodiment, by

associating a plurality of aerodynamic vane inserts 200, each of them

reproducing an aerodynamic vane 13 of the finished impeller, to form an

assembly substantially annular or toroidal. See below.

The base plate 113 has an internal face 113A configured to reproduce a

rear-surface of the finished impeller 10A, 10B or 10C and an external face

113B being substantially opposite to the internal face 113A. The upper-ring

115 has an internal face 115A configured to reproduce a front -surface of the

impeller and an external face 115B substantially opposite to the internal face

115A.

The inner core element 21 is associated under the annular insert 110

and presents a first face 21A (see also Figg.2, 3 and 9), an opposed second

face 21B and an axial hole 21C. The first face 21A has advantageously a

shroud form, similar to a bell, or a tulipan configured to match the inferi or

23
surface of the preform 110; the opposed second face 21B is configured to

reproduce substantially the rear-surface of the finished impeller and the axial

hole 21C is able to be associated on a shaft R of a machine where the finished

impeller can be installed.

In this drawing, the core element 21 is surrounded by a fifth fiber

element 5, a sixth fiber element 6, and a seventh fiber element 7. See below.

It has to be noted that in these drawings the shape of the core element

21 is presented to fill completely the space between the shaft and the perform

110; it does not exclude realizing the core element 21 to fill partially this

space in order to decrease the stress and at the same time the weight of the

finished impeller.

In another advantageous embodiment, these further fabric elements 5,

6 or 7 could be not provided when the core element 21 is made by metallic

material.

Moreover, shaped cavities or holes could be provided on the core

element 21 made by metallic material and inserted with part of the fabric

elements to fix more stably these elements on it.

Moreover, in Fig.2 it is shown a closure system 119 comprises - in this

advantageous embodiment - a plurality of closure pins 119A fixed on the

edge of the internal face 113A of the base plate 113 and with corresponding

closure holes 119B made on the edge of the internal face 115A of the upper -

ring 115; insertion holes 119C are provided on each aerodynamic vane insert

200 in a particular position, see description below.

It’s clear that the closure system 119 is described here as an example

of a realization; this system can vary enormously depending on the particular

24
embodiment.

In Fig.2 it is shown furthermore an axial insert 121 to form the axial

hole 21C of the finished impeller made with a specific mater ial, eventually

the same material of the perform 110 and/or of the inserts 200.

It has to be noted that Fig.2 shows also a plurality of first fabric

elements 1A, each of them associated on the external surface of a respective

aerodynamic vane insert 200; it’s clear that the mold 100 could comprise also

the second and third fabric element 1B and respectively 1C (not shown in

Fig.2 for simplicity) to realize the finished impeller shown schematically in

Fig.1B and respectively 1C.

Fig.3 shows an exploded and lateral view of a mold similar to that of

Fig.2 in which the inserts 200 are associated together to form the annular

insert 110. In this Figure it is not shown the first fabric element 1A nor the

second or third fabric element 1B and 1C for simplicity.

More, in this drawing is shown the forth, fifth and sixth fabric

elements 4, 5, 6 that could be provided inside the mold 100 to form the

finished impeller in an advantageous embodiment of the invention.

In particular, the fourth fabric element 4 is configured to be associated

between the annular insert 110 and the upper-ring 115; the fifth fabric

element 5 is configured to be associated between the core 21 and the internal

face 113A of the base plate 113; the sixth fabric element 6 is configured to

be associated between the annular insert 110 and the core 21; the seventh

fabric element 7 is configured to be associated inside the axial hole 21C of

the core 21. These fabric elements 4, 5, 6, 7 could be impregnated with the

first filling material M during the manufactruing process.

25
 Moreover, in Fig.3 it is also shown the annular insert 110 partially in

section and configured to reproduce an annular assembly of a plurality of

aerodynamic vanes of the finished impeller such that the aerodynamic

characteristics of the finished impeller are preserved.

In a preferred embodiment here described, the annular insert 110

comprises a first face 110A made by the upper surface of the vanes annular

assembly and having substantially a form similar to a bell or a tulipan, and

able to be matched with the fourth fabric element 4. A second face 110B is

substantially opposite to the first face 110A and made by the lower surface of

the vanes annular assembly; a plurality of shaped slots 137 are provided to

reproduce substantially the blades 15 of each vane 13 and the axial hole 21C

being able to be associated to the rotor R of the turbomachine.

This annular insert 110 could be made by joining to each other a

plurality of said aerodynamic vane inserts 200 (as shown in these Figures) or

by a single piece, as said above.

In Fig.4 it is shown schematically a segmented fabric element 37 (see

also Fig.1A) able to be fitted inside the space at the corner of said shaped

slots 137 to increase the rigidity of the whole assembly of the finished

impeller, eliminate preferential flowpaths for the filling material, and avoid

regions containing only filling material with no fiber where cracking might

initiate during cure.

In a preferred embodiment, all the fabric elements 1 to 7 and 37 are

made by fabric material that present soft or (semi) rigid features, so they

could be made separately and associated together during the mold

assembling. The fabric material however could be made by other types

26
according to different embodiments or needs of use of the finished impeller.

Moreover, these fabric elements could be made of different types of fiber

material according to different embodiments, see below.

In Figg.5 and 6 it is shown schematically the aerodynamic vane insert

200 according to an advantageous embodiment of the invention, in which it

comprises a central region 200A configured to reproduce a vane 13 of the

finished impeller and opposite shaped end regions 200B, 200C configured to

be associated with shaped end regions 200B and respectively 200C of an

adjacent vane insert 200 to arrange the annular assembly realizing the annular

insert 110. In particular, the end regions 200B, 200C comprise a lateral

surfaces 200D and respectively 200E are able to engage with the lateral

surfaces 200D and respectively 200E of the adjacent vane insert 200.

Advantageously, the opposite shaped end regions 200B, 200C

reproduce the inlet eye and respectively the outlet eye of the vane 13.

Moreover, in this particular embodiment, the end regions 200B, 200C

are shaped in order to match with end regions of an adjacent insert 200 and,

at the same time, for handling and positioning the vane insert 200 within the

mold 100.

It’s clear that the form and the shape of these end regions 200B, 200C

could be changed according to the particular embodiments of the invention.

It has to be noted that the vane insert 200, shown here, represents a

three-dimensional vane; but it’s clear that this insert 200 could be made

according to other different types, for example a two-dimensional vane or

other.

In Fig.7 it is shown schematically the aforesaid shaped element 19

27
according to an advantageous embodiment of the invention, able to cover just

the portion of a vane 13 of the finished impeller where the erosion process is

higher, for example the bottom part thereof (see Fig.1A).

In particular, this shaped element 19 is realized by a first surface S1

able to reproduce the shape of and to be associated on the inferior wall 13I of

a vane 13, see also Fig.1A; and by lateral edges S2 and S3 to reproduc e

partially the shape of and to be associated on the lateral walls of the blades

15 inside the vane 13. Advantageously, this shaped element 19 can be

associated on the central region 200A of the vane insert 200 and enclosed by

the first, second or third fabric elements 1A, 1B or 1C, see also Figg.5 and 6.

In Fig.8 it is shown a different embodiment with respect to Fig.7 in

which a shaped component 20 is able to coat or cover completely the walls of

the vane 13; in other words, this shaped component 20 forms substantially a

closed channel able to reproduce entirely the vane 13 in which the working

fluid flows.

In particular, this shaped element 20 is realized by a first inferior

surface L1 able to reproduce the shape of and to be associated on the inferior

wall 13I of a vane 13; by lateral edges L2 and L3 to reproduce the shape of

and to be associated on the lateral walls of the blades 15 inside the vane 13

and by a second superior surface L4 to reproduce the shape of and to be

associated on the superior wall 13S of a vane 13.

At the same time, this shaped element 20 can be associated on the

central region 200A of the insert 200 and enclosed by the first, second or

third fabric element 1A, 1B or 1C.

These shaped elements 19, 20 could be made by a material resis tant to

28
erosion or corrosion (as for example metal or ceramic or polymers or other)

and can also be used to further increase the mechanical resistance of the

finished impeller.

It’s clear that the shaped elements 19, 20 have to reproduce the shape

of the vane, so they could be of the three or two dimensional types, or other

types according to the shape of the particular vane in which they have to be

associated.

It has to be noted that the shaped elements 19, 20 can be fixed inside

the vane 13 by the filling material M and also by its shaped form in a simple

and useful way.

Fig.9A shows the first fiber element 1A (see also Fig.1A) that presents

a shape reproducing approximately the shape of the vane 13. In this case, this

element 1A could be made by any type of fibers – as described before – and

it could be advantageously semi-elastic or conformable so as to enlarge itself

to pass over the end regions 200B or 200C of the insert 200 and then to close

around the central region 200A. It is clear that, in a fur ther embodiment, the

insert 200 could not include the end regions 200B, 200C. In another

embodiment, the element 1A could be braided, or otherwise produced,

directly onto the insert 200, so no fabric deformation would be required.

Fig.9B shows the second fiber element 1B (see also Fig.1B) that

presents a shape configured to surround alternately the superior wall 13S of

the vane 13 and the inferior wall 13I of an adjacent vane 13 passing along the

respective blade 15 therebetween. In particular, this seco nd element 1B is

made substantially by a shroud plate shaped so as to form continuously all the

vanes 13 of the annular assembly placing a vane insert 200 and the adjacent

29
vane insert 200 opposed on its surface during the assembly of the mold 100.

Fig.9C shows the third fiber element 1C (see also Fig.1C) that presents

a configuration substantially made by an annular plate to form the superior or

inferior wall 13S or 13I with blade surfaces stretching out from this plate to

form the blade 15 of the finished impeller; this third fabric element 1C can be

placed substantially above the annular insert 110 (as shown in Fig.9C) or

under the annular insert 110 (as shown in Fig.1C) during the assembly of the

mold 100.

In Fig.10 it is shown schematically a cross-section of the mold 100 of

Figg.2 and 3, in which you can see in particular the vane inserts 200 and the

empty spaces inside which is contained the aforesaid fabric elements 1 to 7

and in which the filling material M is filled.

In a particularly advantageous embodiment, the empty spaces are made

so as to match or press together the fabric elements 1 to 7 placed inside so

that the adjacent fabric elements are strictly in contact each other.

In this way it is possible to decrease the empty spaces between tw o

adjacent fiber elements 1 to 7 as much as possible; the filling material M

being able to fill the spaces between fibers of the same fiber element 1 to 7 in

order to provide a high, and controlled, fiber volume fraction, see above; in

particular, using a closed mold it is possible to control these spaces to

provide a high, and controlled, fiber volume fraction.

The filling material M can be injected from a plurality of injection

holes 123 made in the base plate 113 and/or in the upper -ring 115.

In the Figg.11A to 11L there are shown a plurality of fibers that can be

used to make the fiber elements 1A, 1B, 1C, 4, 5, 6,7 or 37 according to

30
different embodiments of the invention.

In particular, shown in Fig.11A is a composite material comprising the

filling material M inside which are enclosed a plurality of continuous fibers

R2 which may be oriented in a preferential direction in order to have optimal

strength distribution on the fiber elements during the use of the finished

impeller.

In Figg.11B and 11C are shown composite materials composed of the

filling material M inside which are enclosed a plurality of particle fibers R3

and respectively discontinuous fibers R4.

In Figg.11D to 11L are shows respectively fibers composed of a

biaxial mesh R5, a sewed mesh R6, a tri-axial mesh R7, a multilayer warping

mesh R8, a three-dimensional twister fiber R9, a cylindrical three-

dimensional mesh R10 and respectively a three-dimensional interwoven mesh

R11. All these types of fibers or mesh can be variously oriented i n order to

have optimal strength distribution on the fiber elements.

It has to be noted that over the years many types of synthetic fibers

have developed presenting specific characteristics for particular applications

that can be used according to the particular embodiments.

For example, the Dyneema ® (also known as "Gel Spun Polyethylene,

or HDPE) of the Company "High Performance Fibers b.v. Corporation” is a

synthetic fiber suitable for production of cables for traction, and it is used for

sports such as kite surfing, climbing, fishing and the production of armors;

another fiber similar to the Dyneema is the Spectra ® patented by an U.S.

Company; and another fiber available on the market is the Nomex ®, a meta -

aramid substance made in the early sixties by DuPont.

31
 The disclosed exemplary embodiments provide objects and methods to

realize an impeller with innovative features. It should be understood that this

description is not intended to limit the invention. On the contrary, the

exemplary embodiments are intended to cover alternatives, modifications and

equivalents, which are included in the spirit and scope of the invention as

defined by the appended claims. Further, in the detailed description of the

exemplary embodiments, numerous specific details are set forth in order to

provide a comprehensive understanding of the claimed invention. However,

one skilled in the art would understand that various embodiments may be

practiced without such specific details.

Although the features and elements of the present exemplary

embodiments are described in the embodiments in particular combinations,

each feature or element can be used alone without the other features and

elements of the embodiments or in various combinations with or without

other features and elements disclosed herein.

This written description uses examples to disclose the invention,

including the best mode, and also to enable any person skilled in the art to

practice the invention, including making and using any devices or systems

and performing any incorporated methods. The patentable scope of the

invention is defined by the claims, and may include other examples that occur

to those skilled in the art. Such other example are intended to be within the

scope of the claims if they have structural elements that do not differ from the

literal language of the claims, or if they include equivalent structural

elements with insubstantial differences from the literal languages of the

claims.

32
 CLAIMS
1. A centrifugal impeller for a turbomachine comprising a plurality of

aerodynamic vanes (13), characterized in that each of them (13) having comprises

internal walls on which is associated a fabric element (1A; 1B; 1C; 4; 5; 6; 7; 37) ,

wherein a second fabric (1B) element is alternately associated on an upper wall (13S) of a

vane (13) and a lower wall (13I) of an adjacent vane (13) passing along the respective

blade (15) there between.

2. The impeller of as claimed in claim 1, wherein the first fabric elements (1A)

are configured to surround each of said aerodynamic vanes (13).

3. The impeller of as claimed in claim 1 or 2, wherein a the second fabric

element (1B) is configured to surround alternately an the upper wall (13S) of a the

vane (13) and a the lower wall (13I) of an the adjacent vane (13) as a continuous

fabric element passing along the respective blade (15) there between.

4. The impeller of at least one of the precedent claimsas claimed in claim 1,

wherein a third fabric element (1C) has a conical surface with blades stretching out

from said surface.

5. The impeller of at least one of the precedent claimsas claimed in claim 1,

wherein it the impeller comprises at least one of the followings:

- a fourth fabric element (4) associated over said aerodynamic vanes (13); said

fourth element (4) having substantially a centrifugal shroud shape and function;

- a fifth fabric element (5) provided to realize substantially a rear-plate for the

finished impeller; said fifth element (5) having substantially an annular planar

shape;

- a sixth fabric element (6) associated under said aerodynamic vanes (13); said

sixth element (6) having substantially an annular shape able to be matched with

34
 the external inferior surface of said aerodynamic vanes (13);

- a seventh fabric element (7) associated around an axial hole (21C) used to

associate a rotor for the turbomachine;

- a segmented fabric element (37) able to be fitted inside the space at the corner

of shaped slots (115) of the vanes (13) to increase the rigidity of the whole

assembly of the finished impeller, eliminate preferential flowpaths for the filling

material, and avoid regions containing only filling material with no fiber where

cracking might initiate during cure;

- a shaped component (19; 20) associated inside each of said aerodynamic

vanes (13) in order to act against the erosion of the working fluid.

6. The impeller of at least one of the precedent claimsas claimed in claim 1,

wherein said fabric elements (1A; 1B; 1C; 4; 5; 6; 7; 39) are impregnated with a

filling material (M).

7. The impeller of at least one of the precedent claimsas claimed in claim 1,

wherein an inner core element (21) is associated under said aerodynamic vanes (13)

in order to facilitate the manufacturing process of said impeller.

8. The impeller of as claimed in claim 7, wherein said core element (21) is

surrounded by at least one of the following: said fourth, fifth, sixth, seventh fiber

elements (4; 5; 6; 7).

9. The impeller of at least one of the precedent claimsas claimed in claim 1,

wherein said fabric elements (1A; 1B; 1C; 4; 5; 6; 7; 37) are made by a plurality of

unidirectional or multidirectional fibers, realized substantially to have a high

anisotropy along at least a preferential direction.

10. A turbomachine wherein it comprises at least a centrifugal impeller as

described from at least one of claim 1 to 9.

35
Dated this 06th day of March 2019.

Yours faithfully,

Chaitanya Wingkar
Agent for the Applicant [IN/PA -1532]

36
A centrifugal impeller for a turbomachine characterized in that it comprises a plurality of
aerodynamic vanes (13), each of them (13) having internal walls on which is associated a
fabric element (1A; 1B; 1C; 4; 5; 6; 7; 37).