Summer Training Report

On
“FREQUENT FAILURE OF CARBIDE TIPS
DURING VIBRO DRILLING OPERATIONS IN
HIGH PRESSURE TURBINE DISKS”
At

Sukhoi Engine Division

Hindustan Aeronautics Limited
Sunabeda,Koraput,Odisha-763002

in partial fulfilment of degree

Bachelor of Technology
in
Mechanical Engineering

Veer Surendra Sai University of Technology

Burla,Sambalpur,Odisha

Submited By:
Mr. Sunil Kumar Behera
Mr. Asutosh Sahoo
Mr. Rajeev Pramanik
Mr. Bardakanata Biswal
Mr. Bhagawan Mahanto
 Acknowledgment

We, the members of the project team, express our

deepest gratitude to Mr. Rudra Prashanna Das, Senior
Manager (Shop), Department 612-UMS, Sukhoi Engine
Division, Hindustan Aeronautics Limited (HAL), Koraput
Division, for his invaluable guidance and support
throughout the course of this project. His expertise
and encouragement have been instrumental in our
learning and successful completion of this case study.
We would also like to thank the technicians and
staff of Shop No. 615 for their cooperation and
assistance during our training period. Their practical
knowledge and insights provided us with a hands-on
understanding of the challenges and solutions in vibro
drilling processes.
Finally, we are sincerely thankful to Hindustan
Aeronautics Limited (HAL), Koraput Division, for giving
us the opportunity to undertake this training and
contribute to a real-world manufacturing scenario. This
experience has been immensely enriching and invaluable
for our professional growth.

Mr. Rudra Prashanna Das

Sr. Manager (Shop)Dept-612-UMS
SED, HAL Koraput Division
 References

NASA Glenn Research Center. (n.d.)

Retrieved from
https://www.nasa.gov/centers/glenn/home/index.html

NASA Jet Propulsion Laboratory. (n.d.). NASA .

Retrieved from https://www.jpl.nasa.gov

U.S. Army. (n.d.). (Lesson Plan AL0993).

GlobalSecurity.org.
Retrieved from
https://www.globalsecurity.org/military/library/polic
y/army/accp/al0993/le2.html

PubHTML5. (n.d.).
[_aviation__The_Jet_Engine_Gas_turbine__turbojet__tur
bofan_Rolls-Royce].
Retrieved from
https://pubhtml5.com/mwnl/fcwf/basic/51-100
 HAL Koraput Division

Hindustan Aeronautics Limited (HAL) is one of the

largest and oldest aerospace and defence companies in
India. It was founded in 1940 in Bangalore as
Hindustan Aircraft Limited by Walchand Hirachand, in
association with the then Kingdom of Mysore and
support from the British Government. The company was
established to support aircraft assembly and
maintenance during World War II.

After India’s independence, HAL was taken over by the

Government of India in 1942 and later merged with
Aeronautics India Limited in 1964 to form the current
HAL. Since then, HAL has been the backbone of India’s
aerospace development and defence aviation, involved
in the design, manufacture, and maintenance of
aircraft, helicopters, engines, avionics, and related
systems.

The Koraput Division of HAL, established in 1964,

plays a crucial role in manufacturing and overhauling
aero engines for military aircraft. It mainly
supports the Sukhoi Su-30MKI, MiG series, and other
fighter aircraft by providing indigenized engine
parts and conducting engine testing, assembly, and
maintenance.

The division is equipped with advanced manufacturing

and testing facilities and contributes significantly
to HAL’s goal of achieving self-reliance in India’s
defence sector. It also supports R&D activities and
collaborates with various institutions to enhance
technology and manufacturing capabilities.
PROPULSION SYSTEMS
When engineers want to move a vehicle through the air
or space, they must apply a force to the vehicle. This
force is known as thrust and is generated by the
propulsion system of the vehicle. Different propulsion
systems develop thrust in different ways, but all
thrust is generated through some application of
Newton’s third law of motion.
Newtons Third Law of motions gives a very interesting
idea for helping us to hover or fly something against
gravity. In other terms we need some masses to leave
very fast from an object in order to move the object
at a velocity conserving the momentum.

• ELECTRIC PROPULTIONS
Electric Propulsion Systems typically use electric
heating or electric or magnetic fields to
accelerate propellants (usually gases). These
systems can be very fuel-efficient but can only
accelerate relatively few particles of gasses at a
time, resulting in very tiny thrusts. Often, these
are ideal engines for deep space exploration where
transit times can be very long and rapid maneuvers
are not required.

• CHEMICAL PROPULTIONS
Chemical Propulsion Systems, on the other hand,
uses chemical reactions to release energy and
accelerate gases to generate thrust. These
systems produce relatively large thrusts in
relatively short periods of time. There are several
kinds of chemical propulsion, including
liquid/gaseous propulsion, solid propulsion, and
hybrid propulsion.

Non Air Breathing Propulsions

Usually known as the Rocket Propulsion Systems,
they don’t use the oxygen present in atmosphere
for combustion instead they carry their own oxygen.

• Liquid propulsion systems

Liquid propulsion systems are typically either a
monopropellant (a single propellant fluid) or a
bi-propellant (two fluids, a fuel and an
oxidizer). The propellants may be stored and fed
from high-pressure fuel tanks (pressure-fed) or
use turbopumps to move the propellant to the engine
(pump-fed). Some propellants ignite on contact
with one another, called hypergolic
propellants. These hypergolic propellants do not
require any other ignition system to burn – making
them much more reliable since there are no ignition
systems to possibly fail. They have good in-space
long-term storability but are also very toxic and
corrosive to handle. The Orion vehicle European
Service Module is an example of a vehicle with a
hypergolic engine system.
When the propellants are stored at temperatures
below the normal freezing point of water, they are
considered “cryogenic” and are typically liquids
or very cold, condensed gases. Hydrogen and Oxygen
are examples of cryogenic propellants, and their
advantage is very high performance and safer
handling than hypergolics. Their disadvantage is
trying to keep them cold for long periods of time
so that they don’t boil away.
The Space Shuttle Orbiter and its big orange tank
or the Saturn V rocket are examples of vehicles
with cryogenic liquid propulsion systems. Liquid
Propulsion systems can produce a wide range of
thrust, can be controlled on and off, but often
must be fueled and set up just prior to their
launch. Also included with Liquid propulsion
systems are Nuclear Thermal Systems, which
typically use a nuclear reactor to thermally heat
cryogenic hydrogen gas to very high temperatures
before exhausting the hydrogen through a rocket
nozzle.

• Solid Propellants
Solid propellants are typically a solid cast
material that contains both fuel and oxidizer bound
in suspension that can produce thrust through
chemical reactions. This “fuel” can be handled at
room temperature until an ignition source is
applied. When the propellants are ignited, they
release both the fuel and oxidizer constituents
which burn and generate thrust. The solid rocket
boosters on either side of the space shuttle are
examples of solid propellant rockets. These
systems generate a lot of thrust, can be stored
for long periods of time in a “ready-to-go” state,
but generally lack the controllability of turning
them off and on when thrust is no longer needed or
when a series of thrust pulses is needed, with some
exceptions.

• Hybrid Propellant Systems

Hybrid propellant systems are a combination of
solid propellant systems and liquid propellant
systems. Typically, there is a solid-propellant
fuel but the oxidizer needed for combustion is kept
separate as a liquid or gas. Only so long as the
oxidizer is supplied over the solid propellant is
there combustion and thrust. The advantages of
this type of system is the high thrust of solid
propellant systems combined with the
controllability (on-off) of liquid propulsion
systems.
 Reference-
Glenn Research Centre, NASA

Air Breathing Propulsions

Aeropropulsion is focused on advancing air-
breathing propulsion technology for aerospace
vehicles and addressing high-speed propulsion
technology barriers.
Here the oxygen from the atmosphere is used as
oxydiser for the fuel.

• Piston Engines (with propellers)

This chapter handles aerodynamics and
thermodynamics of both internal combustion (IC)
engines and propellers into. IC engines – as
classified earlier – belong to the big family of
internal combustion. However, it is of the
intermittent combustion subgroup. This subgroup
of aero piston engines is either of the rotary
or reciprocating families. Rotary engines are
next categorized as either conventional or
Wankel engines. Reciprocating engines have
different types, namely, inline, horizontally
opposed, V-type, X-type, H-type, and radial type
engines. For pressure or power boosting, either
superchargers or turbochargers are added to
reciprocating engines. A detailed aerodynamics
and thermodynamics of reciprocating engines is
given. Terminology for four-stroke engine and
air standard analysis is presented. To examine
the generated power and efficiency of
reciprocating engines, both Otto and Diesel
cycles for four strokes and two strokes types
are thoroughly analyzed.

• Turbojet Engines
Most modern passenger and military aircraft
are powered by gas turbine engines, which are
also called jet engines. The first and simplest
type of gas turbine is the turbojet.
Large amounts of surrounding air are
continuously brought into the engine inlet. (In
England, they call this part the intake, which
is probably a more accurate description, since
the compressor pulls air into the engine.) We
have shown here a tube-shaped inlet, like one
you would see on an airliner. But inlets come in
many shapes and sizes depending on the aircraft's
mission. At the rear of the inlet, the air enters
the compressor. The compressor acts like many
rows of airfoils, with each row producing a small
jump in pressure. A compressor is like an
electric fan. We have to supply energy to turn
the compressor. At the exit of the compressor,
the air is at a much higher pressure than free
stream. In the burner a small amount of fuel is
combined with the air and ignited. (In a typical

jet engine, 100 pounds of air/sec is combined

with only 2 pounds of fuel/sec. Most of the hot
exhaust has come from the surrounding air.)
Leaving the burner, the hot exhaust is passed
through the turbine. The turbine works like a
windmill. Instead of needing energy to turn the
blades to make the air flow, the turbine extracts
energy from a flow of gas by making the blades
spin in the flow. In a jet engine we use the
energy extracted by the turbine to turn the
compressor by linking the compressor and the
turbine by the central shaft. The turbine takes
some energy out of the hot exhaust, but there is
enough energy left over to provide thrust to the
jet engine by increasing the velocity through
the nozzle.

• Turboprop Engines
To move an airplane through the air, thrust is
generated with some kind of propulsion system.
Many low speed transport aircraft and small
commuter aircraft use turboprop propulsion. On
this page we will discuss some of the
fundamentals of turboprop engines. The turboprop
uses a gas turbine core to turn a propeller. As
mentioned on a previous page, propeller engines
develop thrust by moving a large mass of air
through a small change in velocity. Propellers
are very efficient and can use nearly any kind
of engine to turn the prop.
There are two main parts to a turboprop
propulsion system, the core engine and the
propeller. The core is very similar to a basic
turbojet except that instead of expanding all
the hot exhaust through the nozzle to produce
thrust, most of the energy of the exhaust is used

to turn the turbine. There may be an additional

turbine stage present, as shown on the diagram,
which is connected to a drive shaft. The drive
shaft, also shown, is connected to a gear box.
The gear box is then connected to a propeller
that produces most of the thrust. The exhaust
velocity of a turboprop is low and contributes
little thrust because most of the energy of the
core exhaust has gone into turning the drive
shaft.
Because propellers become less efficient as
the speed of the aircraft increases, turboprops
are used only for low speed aircraft like cargo
planes. High speed transports usually use high
bypass turbofans because of the high fuel
efficiency and high speed capability of
turbofans.

• Ramjet Propulsions
Thrust is produced by passing the hot exhaust
from the combustion of a fuel through a nozzle.
The nozzle accelerates the flow, and the reaction
to this acceleration produces thrust. To
maintain the flow through the nozzle, the
combustion must occur at a pressure that is
higher than the pressure at the nozzle exit. In
a ramjet, the high pressure is produced by
"ramming" external air into the combustor using
the forward speed of the vehicle. The external
air that is brought into the propulsion system
becomes the working fluid, much like a turbojet
engine. In a turbojet engine, the high pressure
in the combustor is generated by a piece of
machinery called a compressor. But there are no
compressors in a ramjet. Therefore, ramjets are
lighter and simpler than a turbojet. Ramjets
produce thrust only when the vehicle is already
moving; ramjets cannot produce thrust when the
engine is stationary or static. Since a ramjet
cannot produce static thrust, some other
propulsion system must be used to accelerate the
vehicle to a speed where the ramjet begins to
produce thrust. The higher the speed of the
vehicle, the better a ramjet works until
aerodynamic losses become a dominant factor.
 The combustion that produces thrust in the
ramjet occurs at a subsonic speed in the

combustor. For a vehicle traveling

supersonically, the air entering the engine must
be slowed to subsonic speeds by the aircraft
inlet. Shock waves present in the inlet cause
performance losses for the propulsion system.
Above Mach 5, ramjet propulsion becomes very
inefficient. The new supersonic combustion
ramjet, or scramjet, solves this problem by
performing the combustion supersonically in the
burner.

• Scramjet Propulsions
A scramjet, or Supersonic Combustion Ramjet,
is a type of air-breathing jet engine
specifically designed to operate at extremely
high speeds—typically Mach 5 and above, which
is five times the speed of sound. Unlike
traditional jet engines that use rotating
compressors and turbines to compress air and
generate thrust, scramjets have no moving
parts. Instead, they rely entirely on the
speed of the vehicle itself to compress the
incoming air. This makes them much simpler in
design, but also much more difficult to
operate and control, because they only
function properly at very high speeds.
Scramjets are considered one of the most
promising technologies for future high-speed
transportation systems and spaceplanes because
they can efficiently travel through the
atmosphere without carrying heavy oxygen tanks
like rockets do.

The working principle of a scramjet engine is

based on the concept of supersonic combustion.
When a scramjet-powered vehicle reaches
hypersonic speeds, the air entering the engine
is moving so fast that it naturally gets
compressed by the shape of the engine’s
intake. Unlike in ramjets, where the incoming
air is slowed down to subsonic speeds before
combustion, scramjets allow the air to stay
supersonic throughout the entire process—from
intake to combustion to exhaust. This is what
makes scramjets unique and also extremely
challenging to build. Inside the engine,
hydrogen fuel is usually injected into the
compressed, high-speed airflow and ignited.
Combustion takes place at supersonic speeds,
and the resulting high-pressure, high-
temperature gases are expelled out of the rear
of the engine, producing thrust.

Scramjets are very efficient at hypersonic

speeds because they use oxygen from the
atmosphere instead of carrying liquid
oxidizers like rockets do. This reduces the
weight of the vehicle, making it more fuel-
efficient and capable of carrying more
payload. However, scramjets cannot operate
from a standstill or low speeds. They need to
 be launched using a different propulsion
system—like a rocket or a conventional jet
engine—until they reach the speeds required
for the scramjet to function. Once they’re
moving fast enough, the scramjet can take over
and maintain hypersonic flight. This need for
a “boost phase” is one of the main limitations
of scramjets, and a major engineering
challenge for developing practical scramjet-
powered aircraft or space launch systems.

Despite their challenges, scramjets hold great

promise for the future of high-speed travel
and space exploration. They have been tested
by agencies like NASA and ISRO, and used in
experimental vehicles like NASA’s X-43 and
India’s HSTDV (Hypersonic Technology
Demonstrator Vehicle). The ability to travel
at hypersonic speeds using atmospheric oxygen
opens up possibilities for low-cost satellite
launches, military applications, and even
space tourism. However, more research and
development are needed before scramjets can be
used in everyday transportation or routine
space missions.

• Turbofan Engines
A turbofan engine is the most modern variation
of the basic gas turbine engine. As with other
gas turbines, there is a core engine, whose parts
and operation are discussed on a separate page.
In the turbofan engine, the core engine is
surrounded by a fan in the front and an
additional turbine at the rear. The fan and fan
turbine are composed of many blades, like the
core compressor and core turbine, and are
connected to an additional shaft. All of this
additional turbomachinery is on the schematic.
As with the core compressor and turbine, some of
the fan blades turn with the shaft and some
blades remain stationary. The fan shaft passes
through the core shaft for mechanical reasons.
This type of arrangement is called a two spool
engine (one "spool" for the fan, one "spool" for
the core.) Some advanced engines have additional
spools for even higher efficiency.
The incoming air is captured by the engine
inlet. Some of the incoming air passes through
the fan and continues on into the core compressor
and then the burner, where it is mixed with fuel
and combustion occurs. The hot exhaust passes
through the core and fan turbines and then out
the nozzle, as in a basic turbojet. The rest of
the incoming air passes through the fan and
bypasses, or goes around the engine, just like
the air through a propeller. The air that goes
through the fan has a velocity that is slightly
increased from free stream. So a turbofan gets
some of its thrust from the core and some of its
thrust from the fan. The ratio of the air that
goes around the engine to the air that goes
through the core is called the bypass ratio.
 Because the fuel flow rate for the core is
changed only a small amount by the addition of
the fan, a turbofan generates more thrust for
nearly the same amount of fuel used by the core.
This means that a turbofan is very fuel
efficient. In fact, high bypass ratio turbofans
are nearly as fuel efficient as turboprops.
Because the fan is enclosed by the inlet and is
composed of many blades, it can operate
efficiently at higher speeds than a simple
propeller. That is why turbofans are found on
high speed transports and propellers are used on
low speed transports. Low bypass ratio turbofans
are still more fuel efficient than basic
turbojets. Many modern fighter planes actually
use low bypass ratio turbofans equipped with
afterburners. They can then cruise efficiently
but still have high thrust when dogfighting. Even
though the fighter plane can fly much faster than
the speed of sound, the air going into the engine
must travel less than the speed of sound for high
efficiency. Therefore, the airplane inlet slows
the air down from supersonic speeds.
The AL-31FP Turbofan Engine
The Saturn AL-31FP aero engine is a turbofan design
which is based on gas turbine cycle.
The Saturn AL-31 (originally Lyulka) is a family of
axial flow turbofan engines, developed by the Lyulka-
Saturn design bureau in the Soviet Union, now NPO
Saturn in Russia, originally as a 12.5-tonne (122.6 kN,
27,560 lbf) powerplant for the Sukhoi Su-27 long range
air superiority fighter. The design of the AL-31
turbofan began in the 1970s under the designation
izdeliye 99 by the Lyulka design bureau, also known as
Lyulka-Saturn.
The AL-31FP (F stands for Forsazh, meaning
afterburning, and P for Povorotnoye Soplo, meaning
thrust vectoring nozzle) is an advanced variant of the
AL-31F. The need for enhanced maneuverability and
combat effectiveness in modern fighter jets drove its
development.

AL-31FP engine, stands for

A Name of designer- Arkhip Mikhailovich Lyulka
L Name of company-Lyulka, now NPO Saturn
31 stands for series
F stands for afterburner (Farsa in Russian language)
P stands for thrust vectoring nozzle (Povorothoye in
the Russian language)
The Gas Turbine Cycle
Gas turbines usually operate on an open cycle.
1. A compressor takes in fresh ambient air (state 1),
compresses it to a higher temperature and pressure
(state 2).
2. Fuel and the higher-pressure air from the
compressor are sent to a combustion chamber, where
fuel is burned at constant pressure. The resulting
high-temperature gases are sent to a turbine (state
3).
3. The high-temperature gases expand to the ambient
pressure (state 4) in the turbine and produce
power. The exhaust gases leave the turbine.
4. The rotating turbine is connected to the compressor
hence completing the cycle

The gas turbines generally runs on the thermodynamic

principal of Braton Cycle.
• Braton Thermodynamic Cycle
Gases have various properties that we can observe
with our senses, including the gas pressure p,
temperature T, mass, and volume V that contains the
gas. Careful, scientific observation has determined
that these variables are related to one another, and
the values of these properties determine the state
of the gas. A thermodynamic process, such as heating
or compressing the gas, changes the values of the
state variables in a manner which is described by the
laws of thermodynamics. The work done by a gas and
the heat transferred to a gas depend on the beginning
and ending states of the gas and on the process used
to change the state. It is possible to perform a
series of processes, in which the state is changed
during each process, but the gas eventually returns
to its original state. Such a series of processes is
called a cycle and forms the basis for understanding
engine operation.
 Here we discuss the Brayton Thermodynamic Cycle
which is used in all gas turbine engines. The figure
shows a T-s diagram of the Brayton cycle. Using the
turbine engine station numbering system, we begin
with free stream conditions at station 0. In cruising
flight, the inlet slows the air stream as it is
brought to the compressor face at station 2. As the
flow slows, some of the energy associated with the
aircraft velocity increases the static pressure of
the air and the flow is compressed. Ideally, the
compression is isentropic and the static temperature
is also increased as shown on the plot. The
compressor does work on the gas and increases the
pressure and temperature isentropically to station 3
the compressor exit. Since the compression is ideally
isentropic, a vertical line on the T-s diagram
describes the process. In reality, the compression
is not isentropic and the compression process line
leans to the right because of the increase in entropy
of the flow. The combustion process in the burner
occurs at constant pressure from station 3 to station
4. The temperature increase depends on the type of
fuel used and the fuel-air ratio. The hot exhaust is
then passed through the power turbine in which work
is done by the flow from station 4 to station 5.
Because the turbine and compressor are on the same
shaft, the work done on the turbine is exactly equal
to the work done by the compressor and, ideally, the
temperature change is the same. The nozzle then
brings the flow isentropically back to free stream
pressure from station 5 to station 8. Externally, the
flow conditions return to free stream conditions,
which completes the cycle. The area under the T-s
diagram is proportional to the useful work and thrust
generated by the engine. The p-V diagram for the
ideal Brayton Cycle is shown here:
AL-31FP Turbofan Engine Diagram:
Components & their Machining:
The AL-31FP engine consists of various components which
goes under various machining procedure before being
assembled at the assembly complex.
Here are some of them to be discussed:

1. Bullet Nose Faring

It is a cone like hollow structure installed at
the front end of the engine and facilitates the
air to flow laminarly to reduce turbulences as much
as possible. And also it contains anti-icing sys.

2. Inlet Guide Vanes (Variable)

IGVs are located at the front of the compressor
section. They control the angle at which air enters
the compressor, ensuring uniform airflow
distribution to the compressor blades.
By adjusting the airflow angle, IGVs prevent
flow separation and stall in the compressor,
especially during varying engine speeds. This
ensures stable compressor operation under a wide
range of conditions.
Made up of Titanium alloy consisting of 23
internal and external rings that are connected by
themselves with 23 moveable IGVs. The circular ring
cavity on the external ring forms a channel to
convey hot air trapped from the HPC compressor for
the de-icing system. Their leading edge is fixed &
trailing edge is moveable and capable of deflection
from -30° ~ 0°. In AL31FP, the inlet guide vanes
are variable so that their local angle of incidence
can be changed according to velocity and altitude
of flight automatically by fly by wire control
unit. There is a temperature sensor in this section
as this is the intake section in ‘nose fairing’.
If the temperature is very low and there is ice
formation it activates an anti-icing system, which
 blows the hot air tapped from the turbine section
into the hollow section of guide vanes and heats
the intake air. The guide vanes are manufactured
from titanium-based based alloy by forging and
relevant machine processes as per technology. The
outer casing is made up of aluminium alloy by
forging and machine process.

3. Low Pressure Stator Vanes

The stator vanes are stationary components
positioned between the rotating stages of the LP
compressor. They direct the airflow exiting one
rotor stage to ensure it enters the next stage at
the optimal angle.
The vanes help convert the rotational kinetic
energy imparted by the rotor into increased
pressure, a key aspect of the compression process.
This ensures the LP compressor operates
efficiently and delivers consistent airflow to the
downstream components.

The stator vanes smoothen the airflow between

stages, preventing turbulence or flow separation.
 This contributes to overall engine stability and
prevents compressor stall, especially at varying
engine speeds.
These are mainly composed of titanium alloyed
with other materials to withstand high pressure of
the air flows. Some of the stator veins are
variable and some are stationary, and in variable
stator veins we can control the angle of flow to
control pressure accordingly as per engine
equirements.

4. Low Pressure Compressor Roter

The low-pressure compressor (LPC) rotor is part of
the low-pressure spool, which includes the fan and
LP compressor stages. The rotor consists of a
series of rotating blades mounted on a shaft, which
compress incoming air in stages, raising its
pressure and temperature before delivering it to
the high-pressure compressor.
 The LPC in the AL-31FP typically consists of
four stages, with each stage including a rotor
followed by stator vanes. The rotor blades impart
kinetic energy to the incoming air, increasing its
velocity and pressure.
These 4 stages of LPCR are actually the fan
compressors as they were present outside of the
core engine. A Titanium based alloy Ti-6Al-4V
(Grade 5) is used generally for manufacturing of
the compressor section.

5. Intermediate Casing
The intermediate casing in AL-31FP, serves as a
critical component located between the low-
pressure (LP) compressor and the high-pressure
(HP) compressor. Its primary role is to ensure
smooth airflow transition, structural integrity,
and integration of auxiliary systems. The casing
is designed to guide compressed air from the LP
compressor to the HP compressor with minimal
turbulence or energy loss. It incorporates turning
vanes or guide vanes to optimize the airflow angle,
while ports are provided to extract bleed air for
systems like cabin pressurization, anti-icing, and
cooling. Structurally, the intermediate casing
acts as a load-bearing connection between the
forward and aft sections of the engine, housing
the bearings that support the rotating shafts of
the LP and HP compressors. It also serves as a
mounting point for attaching the engine to the
airframe and includes provisions for damping
vibrations, ensuring operational stability.
Made up of titanium alloys making it stronger
to withstand loads. It is the primary load-carrying
member of the engine the air delivered from LPC is
divided in bypass main duct flow, and thrust from
the engine is transferred to the aircraft by this
casing It contains of outer ring, inner ring &
splitter nose ring, 12 hollow struts connected,
and all three rings with each other. The struts
are numbered clock view from the rear it is a
welded construction to support the HPC casing and
LPC casing and this is used to hang the engine to
aircraft. It is made up of nickel-based alloy. At
the intermediate casing, there is a bypass of LPC
compressed air with a bypass ratio of 0.57:1.

The central bevel drive which is said to be

the heart of the power transmission in the engine
is also placed in this intermediate casing. The
aircraft gearbox transmits power to the engine
gearbox through means of a flexible shaft and the
engine gearbox transmits rotational power to the
 central bevel drive and the bevel gear in transmits
power to the HPC rotor in changing 90 degrees of
direction of power. So, when the HPC rotor attains
40% of its rpm automatically the aircraft auxiliary
power cuts off and engine turbine power comes into
action. While the power is generated by the turbine
some amount of power is transmitted to the aircraft
gearbox from the central bevel drive in the
opposite direction to run the aircraft
accessories.

6. High Pressure Compressor Stator

The high-pressure compressor (HPC) stator is a
crucial component in gas turbine engines, designed
to guide and compress airflow efficiently. It
consists of stationary vanes or blades positioned
between the rotating stages of the compressor.
These stator vanes direct the airflow at the
optimal angle for the subsequent rotor stage,
ensuring maximum aerodynamic efficiency and
compression. Constructed from high-strength
materials to withstand extreme temperatures and
pressures, the stator also helps stabilize the
airflow, minimizing turbulence and enhancing
overall engine performance.

7. High Pressure Compressor Rotors

HPC delivers the highly compressed air to the main
engine duct connected to the C.C. (Combustion
Chamber). The High-Pressure Compressor Rotor
(HPCR) is a drum-disk-type construction consisting
of multiple interconnected sections. These
sections include the 1st, 2nd, and 3rd stages of
the rotor in the first section, which is electron
beam welded, making it a rigid and non-dismantlable
assembly. The second section comprises the discs
for the 4th, 5th, and 6th rotor stages and features
cone-type flanges for load-bearing purposes. The
first and second sections are connected using bolts
at specified flange points, and a front trunnion
is bolted to this section for added structural
support. The third section contains the discs for
the 7th, 8th, and 9th rotor stages, along with an
additional disc equipped with labyrinth seals to
enhance sealing efficiency. These discs are bolted
to a cone-type rear flange section, ensuring
structural integrity and stability.
To maintain the necessary clearances between
components, three spacer rings are installed
between the casings. A special bolt passes through
these rings and the discs, ultimately attaching to
the turbine shaft to transmit torque from the High-
Pressure Turbine Rotor (HPTR) to the High-Pressure
Compressor Stator (HPCS). The HPCS consists of a
first casing, which houses the Inlet Guide Vanes
(IGVs) and the 1st stage stator blades, and a
second casing that accommodates the 4th to 8th
stage stator blades. The 9th stage stator blade is
installed on the combustion chamber casing.
The High-Pressure Compressor (HPC) blades are
forged for superior strength and undergo precise
profile-making
operations. While
the 1st stage
blades are exempt,
the remaining
stages undergo a
cold rolling
process to refine
their aerodynamic
profiles and
enhance
durability. This
complex assembly
of rotors and
stators, supported
by advanced
manufacturing
 techniques such as electron beam welding and cold
rolling, ensures efficient compression, torque
transmission, and overall engine performance.

8. Combustion Chamber
The combustion chamber is the main unit of the gas
turbine engine where the oxidization process is
completed and thrust is produced for the turbine
blades to rotate the shaft assembly with it.
Generally, in a combustion chamber, the fuel and
air mixture get burnt and produce mechanical
energy. This combustion chamber of annular type
consists of an outer casing, Inner casing & flame
tube. The fuel manifolds supply fuel to the
combustion chamber through 28 duel official

burners & fuel is ignited by two igniters. In the

 AL-31FP engine,
the combustion
chamber is an
'annular’ type
combustion
chamber that has
28 atomizers
with two
manifolds. It is
made of 5
components
namely outer
casing, inner casing, flame tube, manifold, and
burner which are forged separately and assembled
each other. As the combustion chamber is the very
hottest section in the chamber, it is made of a
Nickel-based alloy called BT-20, and the casings
are made up of isothermal forging. The forged
casings, manifolds, flame tube, burner, and
atomizers are sent to an electron discharge machine
to place holes in them as there is no standard
drill bit. EDM is an efficient process because of
drilling of holes takes more time. After the
combustion chamber, there is an air heat exchanger
which is said to be the turbine cooling section.
It is activated only when the exhaust temperature
of the combustion chamber increases by 800 degrees
and as well as the rpm of the high-pressure shaft
goes to 92% of its initial rpm. The air heat
exchanger is the combination of a series of small
tubes bent together and braced to each other. On
one side there is an inlet of hot gases from the
combustion chamber and other side there is an
outlet for cooled hot gases to HPT nozzle guide
vanes (1-stage turbine stator blades).
9. Turbine Assembly
In AL31FP the turbine section is a two-stage
impulse reaction type of turbine. One stage is a
High-pressure Turbine (HPT) and the second stage
is a Low-Pressure Turbine (LPT). The turbine discs
and blades are made up of nickel-based alloys which
are capable of being heat resistant. The blades
are specially made by investment casting process
with no post- surface finishing process because of
its precision.

The HPT turbine is connected to the HPC

compressor through a high-pressure spool and LPT
and LPC are connected utilizing a low-pressure
spool. The low-pressure spool will pass through
the hollow structure of the low-pressure spool. As
the hot gases come
from the combustion
chamber initially the
gases are guided by
the turbine stator
blades said to be
1st-stage turbine
nozzle guide vanes
and pass over through
1st-stage turbine rotor blades and next it passes
over the next stage of blades.
 As the gases at stator blades, are guided and
pressurized. The gas molecules expand through the
rotor blades under the kinetic energy of gas
molecules transfer to the blades, so there be an
impulse reaction develops over the blades and
causes the turbine to rotate. There is a special
cooling unit said to be The ‘turbine cooling unit’
which is activated at high temperatures and allows
to extension of the life period turbine section.
The HPT rotor blades have a typical aerofoil shape
with small holes drilled by an electron discharge
machine These holes are interconnected with the
disc so that there is cold compressed air flow
transfer between the compressor and turbine
through a bleed-air system.

In the ‘AL-31FP’ engine there are two types of

turbines are there
LPT- Low Pressure Turbine
HPT- High Pressure Turbine
The turbine section incorporates high-pressure and
low-pressure single- stage axial turbines,
arranged in series and the bearing supports as
well. A high- pressure turbine rotates high-
pressure compressors and the units installed in
 the aircraft accessory gearbox (A.A.G.B) and on
the engine accessory gearbox (E.A.G.B) low-
pressure turbine rotates the low-pressure
compressors and each turbine consists of a rotor
and nozzle guide vane (N.G.V) assembly.
The bearing support of the turbine section of the
load-carrying member of the engine. The radial
loads are transmitted from the HP and LP turbine
rotors to the bearing supports via the inter-rotor
bearing. LP turbine shaft and LP turbine rotor
bearing are located in the bearing support. The
turbine section comprises the bearing support
casing and bearing casing.
The turbine blades are made of nickel-based alloy
metals, which are high-temperature sustainable.
Both HPTR and LPTR are single states and have 90
blades.

10. AfterBurner
Afterburner(reheat) is used for more cruise
improvement and is intended only for ‘CRUISING
SPEED’ is a device done ‘after burning’
process at the exhaust nozzle to provide
thrust augmentation. Thrust augmentation
means to improve the thrust efficiency of the
engine which allows better performance in
flight mode such as short-length take-off and
more cruising speed. In AL-31FP The
Afterburner section consists of 5 fuel
manifolds out of which the primary manifold
supplies fuel to the flame tube and the
remaining manifolds spray the fuel. Then the
after-burner fuel pump supplies fuel to
2,3,4,5 manifolds in sequence. Once all the
manifolds have fuel there is flame carrier and
burning starts at all manifolds and the oxygen
supply cuts. There are two flame stabilizers
to stabilize the flame one big and the other
is small. By activating the afterburner there
is an increase of 6-9% of actual thrust and
there is an increase of 15 degrees in
temperature every 5 sec. & it usages fuels5
liters/sec at full reheated ‘c’ mode.
Some afterburner components are-
Exhaust Mixture
It is intended to mix the main duct gas stream
with bypass airflow before the transition
section
Transition Section
It is designed to provide for the steady burning
of the fuel in the afterburner
Afterburner Casing
It consists of casing & shield some portion
of the bypass air is supplied to the space
which is formed by shield and wall or
transition section casing and afterburner
casing to cool the jet nozzle and casing.
Exhaust Fairing
It is designed to decrease the exhaust gas
energy losses. The exhaust fairing preparation
is intended to decrease afterburner
intermediate burning.

11. Diffuser
The diffuser slows down the
compressor delivery air to
reduce flow losses in the
combustor. Slower air is
also required to help
stabilize the combustion
flame and the higher static
pressure improves the
combustion efficiency. There
are two casings inner
casing and an outer casing

made up of mnemonic,
and compressed air
from the compressor
is passed between to
cool the hot gases by
using a bleed air
system.
12. Thrust Vector Controlled Nozzle
The thrust vectoring variable area jet
nozzle is an all-mode supersonic C-D nozzle
their main parts are:
(i) The tilting unit consists of fixed
and moveable casing the fixed
casing is hinged to the moveable
casing by means up to pivots. The
moveable casing is turned
concerning fixed casing at the
maximum angle of ±14° utilizing
two pairs of hydraulic cylinders
located on both sides of the
horizontal axis of the tilting
device. The hinged pin of the
fitting device is turned relative
to the horizontal plane at an
angle of 32° counterclockwise for
the clockwise LH engine and
clockwise for the RH engine viewed
from the rear.
(ii) Subsonic Jet Nozzle is the
convergent nozzle with
synchronization drive and control
mechanism to control the nozzle
throat. There are 16 convergent
nozzle shutters with 16 sealing
spacers and the convergent
subsonic jet nozzle. The shutters
are controlled by 16 hydraulic
cylinders; the hydraulic
cylinders are fuel-operated to
actuate the jack. A high-pressure
pump (NP-160D) Delivers fuel
under pressure to the jacks. The
control is carried out by the
engine nozzle and afterburner
controller (RSF-31BT1).
(iii) The Supersonic nozzle is a
divergent nozzle with
synchronization drives and
control mechanism to control the
jet nozzle exit area by other
shutters. 16 divergent nozzle
shutters with 16 sealing spacers
form the divergent supersonic
section of the jet nozzle. The
 hydraulic cylinders control the

shutters.

These main parts are controlled & fitted with-

•Jet nozzle casing:
It is the outer casing, which is used to
connect the diffuser section and nozzle
section. Made up of titanium-based alloy for
strain hardening.

•Flaps:
Flaps are the moving parts in the nozzle
section that play a vital role in
controlling the throat area of the nozzle.
There are different flaps in the nozzle
section while viewing in top view of the
inlet of the engine.1) Inner flaps/Lower
flaps are the flaps before the throat of the
nozzle and are made of nickel alloy because
of high- temperature contact.2) Upper flaps
are the flaps after the throat area.3) Outer
flaps are the flaps covering the inner
components of hydraulic, pneumatic, and
mechanical linkages and forming nozzle
shape.

•Spacers:
Spacers are the stationary parts and act
as supporters to the flaps, which are
interconnected with hinge supports. There
are also different types related to the
flaps and supports respective flaps. In
alignment, one flap and one spacer are
arranged in a circular shape and connected
with hinge supports.

•Mechanical linkages:
Mechanical linkages are the connectors for
different components and are used in
mechanical movements with the activation of
pressure cylinders. Linkages like crossbeam,
lever, telescopic support, brackets, piston
rods, limiters.

•Hydraulic cylinders:
2 types of hydraulic cylinders are used
in the nozzle section.
i) One type consists of four cylinders,
which are used to tilt the nozzle in
a vertical direction up and down 14
degrees regarding the front view.
ii) The second type consists of 16
cylinders, which are used in controlling
the throat area, either
expansion/contraction with mechanical
linkage to the flaps.

•Pneumatic cylinders:
There are 16 pneumatic cylinders, which
are used for restricting the over,
expansion/contraction of the nozzle throat
area by flaps and it is limited by limiters
around the upper flaps interconnected with
cylinders.

•Graphite ring:
Graphite ring is a ring, that fits in between
the nozzle and diffuser section of the
afterburner, provides lubrication during the
time of tilting, and is covered with jet
nozzle casing.
CASE STUDY: Analysing the Challenges in Vibro
Drilling for High-Pressure Turbines

Introduction:
Upon carefully studying each and every
manufacturing processes related to the HPT
Disk, Part No.: 104.04.02.008 we came over a
very special operation, the Vibro Drilling
operation with Operation No.: 1234456 at the
turbines shop, Shop No.: 615 of Sukhoi Engine
Division at Hindustan Aeronautics Limited.
Observations at the worksite revealed a
significant issue—numerous broken carbide
drill tips scattered across the tool desk.
Conversations with the technicians confirmed
that drill bit failures are a recurring
problem, disrupting operations and
necessitating frequent tool replacements.

Materials:
While looking at the design and operation
booklets what they call “The Technology
Booklets” we found a Russian notation for the
super alloys used in the HPT Disks ie.
ХН62БМҚТЮ – ид and upon research we found the
composion of the super alloys.
The designation ХН62БМҚТЮ follow a naming
convention of Russian or CIS-region alloys,
specifically those used for high-performance
applications like aviation, power generation,
or chemical industries. Here's a breakdown of
what the components of the name might signify
based on the typical Russian metallurgical
nomenclature:
ХН: Indicates the base composition, usually Хром
Chromium) and Никель (Nickel). This suggests
 it's a chromium-nickel-based alloy, likely a
high-temperature or corrosion-resistant
material.
62: Represents the approximate percentage of
nickel in the alloy.
БМ: Indicates the addition of specific elements:
• Б: Typically Молибден (Molybdenum)
for strength and high-temperature
performance.
• М: May signify Марганец (Manganese)
or Медь (Copper), depending on context,
for enhanced properties like toughness
or corrosion resistance.
ҚТЮ: Likely represents minor alloying additions or
specific properties:
• Қ: Possibly Кобальт (Cobalt) for
improved heat resistance.
• Т: Likely Титан (Titanium) for
strength and grain refinement.
• Ю: May indicate Алюминий (Aluminum)
for oxidation resistance or other
alloying roles.

Whereas the Carbide Tips of the drill bits in

the vibro drilling apparatus are generally
Cemented Carbides, but their exact composition
and design depend on the specific requirements
of the vibro drilling process.

Hardness:
The hardness of the HPT Disk was given to be
3,0……3,4HB D IND on the Brinell Hardness
scale, with additional notation indicating
specific test parameters.
 1. Brinell Hardness (HB):
3,0…3,4HB indicates the Brinell hardness
value, ranging from 3.0 to 3.4 HB.
This is an extremely low hardness value,
which is unusual for metallic alloys. It
could suggest:
▪ The material is in an annealed
(softened) state.
▪ It might refer to an early-stage
processing material (e.g., raw
cast form) or a non-metallic
material, such as a composite.
2. D IND:
This refers to the type of indenter used
in the Brinell test.
D typically signifies a steel or tungsten
carbide ball with a specified diameter,
commonly 10 mm.
IND could stand for "Indentation,"
referring to the method of applying load
and measuring hardness.

Procedure for Vibro Drilling Operation:

The processes associated with the vibro drilling
operations are as found by us are detailed below:
1. Casing of the machine was opened.
2. View the fineness of the jig bushes and rigidity
of fastening.
3. View the mounting surface of Jig for the absence
of depressions, dents and chips.
4. Carefully cleaned the mounting surfaces from the
chips and hair brush.
5. Mount the part on the jig with the clamp
carefully, without affecting bushes and without
 allowing any dents, depressions on the mounting
surfaces of the part.
6. Fix the part with the fixing area along the
Firtree slot, masked with 2 lines & fast the
part.
7. Drill 2 holes on outlet with
dimensions.
(1)
(2)
(3)
(4)
8. Drill remaining 88 holes.
9. Remove the part.
10. Check Dimensions (1),(4) and sign the route
card.

Technical Requirements of Operation:

• Permissible Symmetry of holes T/2 0.15mm
(Relative Tolerance).
• Base of axis of symmetry slot(φ), Axis(T)
• It is ensured by jig check periodically as per
CTП 521.08.059 .
• Compulsory removal of drills after machining
of 3 holes.
• Drill bit’s tips made of carbide.
• Checking by L/M-15 for cracks in it.

Modes of Operations:
N: 770 RPM
S: 15.5 mm/min
F: 66 Hz
Coolant: MP-7
Diagram:
Following is the associated diagram we found for the
Vibro Drilling operation, Oprn. No.: 13524 on the HPT
Disk, Part No.: 104.04.02.008 of AL-31FP turbojet.

Observations:
• Procedure Review- Based on our comprehensive
survey and observation of the Vibro Drilling
operation, it has been noted that the process
is being executed seamlessly and in strict
adherence to the guidelines outlined in the
Technology Booklets.
The following aspects were particularly
highlighted:
1. Compliance with Standard Procedures:
o All steps, from the preparation of the
jig and the mounting of the workpiece
to the final inspection of drilled
holes, are being followed meticulously.
 o Technicians demonstrated thorough
knowledge of the prescribed
methodologies, ensuring consistency and
precision throughout the operation.
2. Effective Use of Resources:
o The jig and tooling components,
including the carbide drill bits, were
observed to be handled and maintained
as per the specified recommendations.
o Periodic inspections and cleaning
routines were carried out diligently,
minimizing the risk of misalignment or
wear-related issues.
3. Quality Assurance Measures:
o Dimensional checks and crack
inspections were conducted at the
prescribed intervals, ensuring the
drilled holes consistently met the
required tolerances.
o The use of calibrated tools and
adherence to inspection protocols
provided additional confidence in the
operation's reliability.
4. Smooth Workflow:
o The workflow was observed to be
uninterrupted, with well-defined roles
and responsibilities among the team
members.
o The implementation of proper handling
techniques and alignment processes
significantly reduced the likelihood of
operational errors or damages to the
parts.
 • Tool Inspection:
Upon inspection of various broken drill bits
and comparing them with new ones we found that
the tool is generally made up of steel having
hollow area with holes at sides for supply of
coolant through it and above which the
tungsten carbide tip of the bit is brazed to
it. Through better inspection we found two
types of tool failues:
(i) In some bits the carbide tip
wear out at the top making it
a smooth circular surface.
(ii) Other carbide tips gets twist
and fails.

• Material Hardness Test: A sample of the

material of the HPT Disk is taken to the
Brinell Hardness Testing Machine when under
the specified parameters the material testing
takes place to get the desired hardness in
Brinell scale ie. 3.0 to 3.4 HB.

Root Cause Analysis:

The analysis identifies two primary modes of
carbide tip failures: surface smoothing at the
tip and twisting and failure of the drill tips.
Below are the root causes associated with each
failure mode:
1. Surface Smoothing at the Tip
Observation: The carbide tip becomes
smooth at the top, losing its cutting edge
and reducing efficiency.
 Root Causes:
o Insufficient Cooling: Poor heat
dissipation leads to thermal degradation
and smoothing of the cutting edge.
o Excessive Friction: Suboptimal cutting
parameters (e.g., high speed, low feed)
increase friction.
o Material Hardness: The nickel-based
superalloy's high hardness accelerates
wear.
o Poor Lubrication: Inefficient coolant
delivery fails to minimize friction at the
cutting interface.

2. Twisting and Failure of Drill Tips

Observation: The carbide tip twists and
breaks during operation, causing complete
failure.

Root Causes:
o Excessive Torque: High mechanical load due
to improper feed rate or cutting speed.
o Misalignment: Tool or workpiece
misalignment generates uneven stress on
the tool.
o Chip Accumulation: Poor chip evacuation
increases resistance, leading to
twisting.
o Tool Weakness: Suboptimal geometry or
material of the drill tip concentrates
stress at weak points.

Common Contributing Factors:

Vibration Mismatch: Suboptimal frequency
and amplitude may exacerbate stress and wear.
 Work-Hardening: The material's tendency
to harden during cutting increases resistance.
Tool Material Limitations: Inadequate
coating or carbide composition for the
specific alloy.
Operational Practices: Lack of real-time
monitoring and adjustments during drilling.

Solutions and Recommendations:

Conclusion:
The vibro drilling process, as applied to high-strength
materials such as High-Pressure Turbine (HPT) disks,
offers numerous advantages but also presents
significant challenges that require precise
management.
Advantages of Vibro Drilling:
1. Enhanced Precision: The process ensures accurate
hole placement and consistent dimensional
tolerances, critical for aerospace applications.
2. Improved Surface Finish: The vibration-assisted
mechanism reduces burr formation, yielding
smoother surfaces compared to conventional
drilling.
3. Reduced Cutting Forces: The vibratory motion
minimizes resistance during cutting, prolonging
tool life under optimal conditions.
4. Suitability for Hard Materials: Vibro drilling is
effective for machining tough materials like
nickel-based superalloys used in HPT disks.
Challenges of Vibro Drilling:
1. Tool Wear and Failure: Carbide tips frequently fail
due to thermal and mechanical stresses,
particularly in hard materials.
2. Vibration Mismatch: Suboptimal tuning of frequency
and amplitude can exacerbate tool wear and affect
hole quality.
3. Cooling Efficiency: Insufficient cooling can lead
to overheating, causing thermal cracks and
reducing tool longevity.
4. Workpiece Properties: The tendency of materials
like nickel alloys to work-harden increases the
difficulty of machining.
5. Process Sensitivity: Even minor deviations in
cutting parameters or tool alignment can result in
reduced efficiency or tool breakage.