Rotating Fluid Machines
(Turbines & Pumps)
Group Members:
Kashif Usman 51-FET/PhDME/F22
Hamid Masood 109-FET/MSME/F22
Fluid Machines (Hydraulic Machines)
⚫A fluid machine is a device which
converts the energy stored by a fluid
into mechanical energy or vice versa.
⚫Hydraulic machines are defined as those
devices which convert either hydraulic
energy into mechanical energy or
mechanical into hydraulic energy.
Classification
⚫According to energy consideration
Machines that supply energy to fluid (Pumps)
Machines that extracts energy from fluid (Turbines)
Hydraulic Machines
⚫ Turbine is a device that extracts energy from a
fluid (converts the energy held by the fluid to
mechanical energy)
⚫ Pumps are devices that add energy to the fluid
(e.g. pumps, fans, blowers and compressors).
HydraulicTurbines
Hydraulic Turbines
⚫Hydraulic Turbines are devices that
convert hydraulic energy(energy
possessed by water) into mechanical
energy.
⚫The energy of the water can be in the form
of potential or kinetic energy.
Turbines
⚫ Hydro electric power is the most remarkable
development pertaining to the exploitation of
water resources throughout the world
⚫ Hydroelectric power is developed by hydraulic
turbines which are hydraulic machines.
⚫ Turbines convert hydraulic energy or hydro-
potential into mechanical energy.
⚫ Mechanical energy developed by turbines is
used to run electric generators coupled to the
shaft of turbines
⚫ Hydro electric power is the most cheapest
source of power generation.
Turbines Classification
⚫ According to the energy used
Impulse turbine
Reaction turbine
⚫ Direction of water flow
Axial flow - Radial in axial out
Inward flow - Outward flow
⚫ According to the head available to the inlet of turbine
High Head Turbine (250-1800m), Pelton Wheel
Medium Head Turbine (50-250m), Francis Turbine
Low Head Turbine ( <50m), Kaplan Turbine
⚫ According to the specific speed
Low specific speed ( <50) Pelton wheel
Medium specific speed (50 < Ns < 250) Francis
High Specific speed ( >250) Kaplan
⚫ According to the fluid used
Water Turbine (Pelton Wheel, Francis Turbine, Kaplan Turbine)
Gas Turbine
Steam Turbine
Turbines Classification (Contd…)
⚫ Impulse Turbine
All available head of water is converted into kinetic
energy or velocity head in a nozzle. The water shoots
out of the nozzle and hits a bucket which rotates a shaft.
Water is in contact with atmosphere all the time and
water discharged from bucket fall freely
The flow is similar to open channel flow and works
under atmospheric pressure.
The kinetic energy of water is converted to mechanical
energy.
The water entering the turbine exerts a force in the
direction of the flow.
Pelton wheel is an example.
Turbines Classification (Contd…)
⚫ Reaction Turbine
The entire water flow takes place in closed conduit and
under pressure.
At the entrance to turbine/runner only part of the energy
is converted to kinetic energy, remaining into pressure
energy
The flow is similar to the closed conduit flow.
The water exerts a reaction opposite to the direction of
its flow while leaving the turbine.
Reaction turbines may be inward or outward or radial
flow.
Francis turbine, Kaplan Turbines are some example
Impulse Turbine
⚫ Pelton Wheel
It consists of a wheel mounted on a shaft.
Buckets are mounted on the periphery of the wheel
Water is impinged on the buckets and energy is
transferred
The water has only kinetic energy
Each bucket is shaped like a double hemispherical cup
with a sharp edge at the center.
Pelton wheel is used for high head of water (150-
2000m)
The flow is tangential.
Pelton Wheel
Pelton Wheel
Pelton Wheel
Reaction Turbine
⚫ Francis Turbine
The Francis turbine is a reaction turbine, which means that the
working fluid changes pressure as it moves through the turbine,
giving up its energy. A casement is needed to contain the water
flow. The turbine is located between the high pressure water
source and the low pressure water exit, usually at the base of a
dam.
The inlet is spiral shaped. Guide vanes direct the water
tangentially to the runner. This radial flow acts on the runner
vanes, causing the runner to spin. The guide vanes (or wicket
gate) may be adjustable to allow efficient turbine operation for a
range of water flow conditions.
As the water moves through the runner its spinning radius
decreases, further acting on the runner. Imagine swinging a ball
on a string around in a circle. If the string is pulled short, the ball
spins faster. This property, in addition to the water's pressure,
helps inward flow turbines harness water energy
Francis Turbine
Draft Tube
⚫ The turbines have to be installed
a few meters above the flood
water level to avoid inundation. (In the case of
impulse turbines this does not lead to significant
loss of head)
⚫ In the case of reaction turbines, the loss due to
the installation at a higher level from the tailrace
will be significant.
Draft Tube
⚫ This loss is reduced by connecting
a fully flowing diverging tube from
the turbine outlet to be immersed
in the tailrace at the tube outlet.
⚫ The loss in net(effective) head is
reduced by this arrangement. Also
because of the diverging section of the tube the kinetic
energy is converted to pressure energy which adds to
the effective head.
Francis Turbine
Kaplan Turbine
⚫ The Kaplan turbine is a propeller-type water
turbine that has adjustable blades.
⚫ It is an axial flow reaction turbine
⚫ Because of the adjustable blades it is possible to
run at maximum efficiency at any load.
⚫ Water flows through the guide vanes, and then
flows axially through the runners.
⚫ The runner blade angles can be changed by a
lever.
⚫ It can work on very low head but requires high
flow rate.
Kaplan Turbine
Kaplan Turbine
Pumps
Pumps
⚫A pump is a device used to move gases,
liquids or slurries. A pump moves liquids
or gases from lower pressure to higher
pressure, and overcomes this difference in
pressure by adding energy to the system.
⚫Mechanical Energy Hydraulic energy
Pumps Classification
Pumps Classification (contd)…
⚫ Pumps are divided into two fundamental types based on
the manner in which they transmit energy to the pumped
media: kinetic or positive displacement.
⚫ In kinetic displacement, a centrifugal force of the
rotating element, called an impeller, “impels” kinetic
energy to the fluid, moving the fluid from pump suction to
the discharge.
⚫ Positive displacement uses the reciprocating action of
one or several pistons, or a squeezing action of meshing
gears, lobes, or other moving bodies, to displace the
fluid from one area into another (i.e., moving the material
from suction to discharge).
⚫ Sometimes the terms ‘inlet’ (for suction) and ‘exit’ or
‘outlet’ (for discharge) are used.
Pumps Applications
⚫To deliver fluid at a higher elevation or at a
long distance.
⚫To deliver fluid at a pressurized device
⚫For the control of hydraulic systems
⚫For drainage system, removing slurries,
mud, water
⚫For irrigation systems
⚫Cleaning, car wash
Centrifugal Pumps
⚫The hydraulic machines that converts the
mechanical energy into pressure energy
by means of centrifugal force acting on the
fluid are called centrifugal pumps.
⚫3 important parts are
Impeller
Volute casing
Suction and delivery pipes.
Centrifugal Pumps
Centrifugal Pumps (Contd…)
⚫The rotating part of the centrifugal pump is
called impeller. It is a rotating solid disk
with curved blades. Impellers could be
open, semi-open or closed.
Open Semi - Open Closed
Centrifugal Pumps (Contd…)
Backward curved Radial curved Forward curved
⚫ For Incompressible fluids (water) backward
curved vanes are used (pumps)
⚫ For compressible fluids (air) forward curved
vanes are used (compressors)
Centrifugal Pumps (Contd…)
⚫ Casing is an airtight passage surrounding the
impeller which converts the kinetic energy of the
fluid leaving the impeller into pressure energy.
⚫ Suction pipe is connected to the inlet of the
pump and other side is dipped into the fluid in a
sump. Delivery pipe is connected to the outlet
of the pump and other end delivers the fluid at
required height.
Centrifugal Pumps (Contd…)
Working principle
⚫ The impeller is keyed onto a shaft which is mounted on
bearings and is coupled to a motor which rotates the
impeller.
⚫ The kinetic energy of the impeller is transmitted to the
fluid and its velocity increases.
⚫ The volute casing converts the kinetic energy of the fluid
to pressure energy. The pressure at the center of the
impeller (eye) decreases as the fluid flows outward. The
decrease in pressure causes the fluid of the sump to
continuously flow through the suction pipes.
⚫ The high pressure fluid is delivered through the delivery
pipe.
Centrifugal Pumps (Contd…)
Centrifugal Pumps (Contd…)
Centrifugal Pumps (Contd…)
⚫Priming
The pump casing must be filled with liquid
before the pump is started, or the pump will not
be able to function.
To ensure that a centrifugal pump remains
primed most centrifugal pumps have foot valves
installed or are located below the level of the
source from which the pump is to take its
suction.
Centrifugal Pumps (Contd…)
⚫ Cavitations
If the suction pressure at the eye of the impeller falls
below the vapor pressure of the fluid being pumped, the
fluid will start to boil.
Any vapor bubbles formed by the pressure drop at the
eye of the impeller are swept along the impeller vanes
by the flow of the fluid. When the bubbles enter a region
where local pressure is greater than saturation pressure
farther out the impeller vane, the vapor bubbles abruptly
collapse.
This phenomenon is called cavitation.
Centrifugal Pumps (Contd…)
⚫There are several effects of cavitations
It creates noise, vibration, and damage to many
of the components.
We experience a loss in capacity.
The pump can no longer build the same head
(pressure)
The output pressure fluctuates.
The pump's efficiency drops.
Centrifugal Pumps (Contd…)
⚫Prevention of cavitation
Raise the liquid level in the tank
Lower the pumping fluid temperature
Reduce the N.P.S.H. Required
Use a pump with a larger, impeller eye opening.
Pump should be airtight
Friction losses should be decreased
Centrifugal Pumps (Contd…)
⚫Configuration of pumps
Pumps in parallel
⚫For high flow rate requirement
⚫Head or pressure developed is same as the
individual pump
⚫Flow rate is the summation of the individual pumps
Pumps in series
⚫For high head or pressure requirement
⚫Flow rate remains same as the individual pump
⚫Head or pressure is the summation of two pumps.
Centrifugal Pumps (Contd…)
⚫High velocity vs. High pressure
Water can be raised from one level to a higher
level in two ways – High pressure and High
velocity
High velocity method is very inefficient since the
friction increases with proportional to the square
of the velocity
High pressure method is efficient because of
low friction.
Rotary PDP
⚫ A rotary pump traps fluid in its closed casing and
discharges a smooth flow.
⚫ They can handle almost any liquid that does not
contain hard and abrasive solids, including
viscous liquids.
⚫ They are also simple in design and efficient in
handling flow conditions that are usually
considered to low for economic application of
centrifuges.
⚫ Types of rotary pumps include cam-and-piston,
gear, lobular, screw, and vane pumps
Rotary PDP
⚫External Gear Pump
Rotary PDP
⚫Internal Gear Pump
Rotary PDP
⚫Lobe Pump
Rotary PDP
⚫Vane Pump
Rotary PDP
⚫Screw Pump
Rotary PDP
⚫Diaphragm Pump
Cross-section of a diaphragm pump
Rotary PDP
⚫Piston pump
