2. Pumps and turbines in which energy is supplied or extracted by a rotating shaft are
properly called turbomachines.
Turbomachines
Not all pumps or turbines utilize a rotating
shaft, however. The hand-operated air pump
you use to inflate the tires of your bicycle is a
prime example.
The up and down reciprocating motion of a
plunger or piston replaces the rotating shaft in
this type of pump, and it is more proper to call
it simply a fluid machine instead of a
turbomachine.
3. Turbomachinery - Classification
There are two broad categories of turbomachinery, pumps and turbines.
The word pump is a general term for any fluid machine that add energy to a fluid.
Pumps are energy absorbing devices since energy is supplied to them, and they
transfer most of that energy to the fluid usually via a rotating shaft.
4. Turbines, on the other hand, are energy producing devices. They extract energy
from the fluid and transfer most of the energy to some form of mechanical energy
output, typically in the form of a rotating shaft.
Turbomachinery – Classification cont..
5. Turbomachinery – Classification cont..
The purpose of a pump is to add energy to a fluid, resulting in an increase in fluid
pressure, not necessarily an increase of fluid speed across the pump.
The purpose of a turbine is to extract energy from a fluid, resulting in a decrease of
fluid pressure, not necessarily a decrease of fluid speed across the turbine.
6. Turbomachinery – Pumps
Fluid machines that move liquids are called pumps, but there are several other
names for machines that move gases.
A fan is a gas pump with relatively low pressure rise and high flow rate. Examples
include ceiling fans, house fans, and propellers.
A blower is a gas pump with relatively moderate to high pressure rise and moderate
to high flow rate. Examples include centrifugal blowers in automobile ventilation
systems, furnaces etc.
7. A compressor is a gas pump designed to deliver a very high pressure rise, typically
at low to moderate flow rates. Examples include air compressors that run pneumatic
tools and inflate tires at automobile service stations, and refrigerant compressors used
in heat pumps, refrigerators, and air conditioners.
Turbomachinery – Pumps
Pumps
Positive
Displacement
Pumps
Dynamic
Pumps
8. Turbomachinery – Positive-Displacement Pumps
In Positive – Displacement Pumps, fluid is sucked into an expanding volume and then
pushed along as that volume contracts.
Examples
Three-lobe
rotary pump
Gear pump Double screw pump
9. Turbomachinery – Positive-Displacement Pumps
Operation of a positive-displacement pump
In the figure, four phases of operation of a two- lobe rotary pump is shown. The two
rotors are synchronized by an external gear box so as to rotate at the same angular
speed, but in opposite directions. In the diagram, the top rotor turns clockwise and the
bottom rotor turns counterclockwise, sucking in fluid from the left and discharging it to
the right.
10. If you refer the previous figure again, you can realize that the gaps exist between the
rotors and the housing and between the lobes of the rotors themselves cause to leak
the fluid through these gaps, reducing the pump’s efficiency.
Turbomachinery – Positive-Displacement Pumps
Positive displacement pumps are ideal for high-pressure applications like pumping
viscous liquids or thick slurries, and for applications where precise amounts of liquid
are to be dispensed or metered, as in medical applications.
11. High-viscosity fluids cannot penetrate the gaps as easily; hence the net head (and
efficiency) of a rotary pump generally increases with fluid viscosity.
This is one reason why rotary pumps (and other types of positive displacement
pumps) are a good choice for pumping highly viscous fluids and slurries.
They are used, for example, as automobile engine oil pumps and in the foods
industry to pump heavy liquids like syrup, tomato paste, and chocolate, and slurries
like soups.
Turbomachinery – Positive-Displacement Pumps
12. Turbomachinery – Positive-Displacement Pumps
Example
A two-lobe rotary positive-displacement
pump, moves 0.45 cm3 of SAE 30
motor oil in each lobe volume Vlobe, as
sketched in the figure. Calculate the
volume flow rate of oil for the case
where the pump speed is 900 rpm.
13. Turbomachinery – Dynamic Pumps
There are three main types of dynamic pumps that involve rotating blades called
impeller blades or rotor blades, which give momentum to the fluid.
For this reason they are sometimes called rotodynamic pumps or simply rotary
pumps (not to be confused with rotary positive-displacement pumps, which use the
same name).
Dynamic
Pumps
Centrifugal
flow pumps
Axial-flow
pumps
Mixed flow
pumps
14. Turbomachinery – Dynamic Pumps
Centrifugal flow pump
In a centrifugal-flow pump, fluid enters axially (in the same direction as the axis of
the rotating shaft) in the center of the pump, but is discharged radially (or
tangentially) along the outer radius of the pump casing. For this reason centrifugal
pumps are also called radial-flow pumps.
Centrifugal pumps and blowers can be easily identified by their snail-shaped casing,
called the scroll .They are found all around your home—in clothes washers and
dryers, hairdryers, vacuum cleaners, bathroom exhaust fans etc.
15. Turbomachinery – Dynamic Pumps
Figure shows Side view and frontal view of a typical centrifugal pump. Fluid enters
axially in the middle of the pump (the eye), is flung around to the outside by the rotating
blade assembly (impeller) is discharged out the side of the pump.
16. Axial Pumps
In an axial-flow pump, fluid enters and leaves axially, typically along the outer portion
of the pump because of blockage by the shaft, motor, hub, etc.
The rotor of a helicopter, for example, is a type of axial-flow pump The lift force on the
blade is caused by pressure differences between the top and bottom surfaces of the
blade.
Turbomachinery – Dynamic Pumps
17. Turbomachinery – Dynamic Pumps
Axial-flow pumps (axial-
flow fans) may be open or
ducted:
(a) a propeller is an open fan
(b) a computer cooling fan is
a ducted fan.
18. Turbomachinery – Dynamic Pumps
A well-designed rotor blade or propeller blade has
twist, as shown by the orange cross sectional slices
through one of the three blades; Blade pitch angle
is higher at the root than at the tip because the
tangential speed of the blade increases with radius.
19. Turbomachinery – Turbines
Turbines have been used for centuries
to convert freely available mechanical
energy from rivers and wind into
useful mechanical work, usually
through a rotating shaft.
The picture shows an old windmill in
Klostermolle, Vestervig, Denmark that was
used in the 1800s to grind grain.
20. Turbomachinery – Turbines
When the working fluid is water, the turbines are called hydraulic turbines or
hydroturbines.
When the working fluid is air, and energy is extracted from the wind, the machine is
properly called a wind turbine.
Whereas the rotating part of a pump is called the impeller, the rotating part of a
hydroturbine is called the runner.
21. Turbomachinery – Turbines
In coal or nuclear power plants, the working fluid is usually steam; hence, the
turbomachines that convert energy from the steam into mechanical energy of a
rotating shaft are called steam turbines.
A more generic name for turbines that employ a compressible gas as the working
fluid is gas turbine. (The turbine in a modern commercial jet engine is a type of gas
turbine.)
22. Turbomachinery – Positive-Displacement Turbines
A positive-displacement turbine may be thought of as a positive-displacement pump
running backward—as fluid pushes into a closed volume, it turns a shaft or displaces a
reciprocating rod. The closed volume of fluid is then pushed out as more fluid enters the
device.
The most common example is the water meter in
your house. Many commercial water meters use
a rotating disc that wobbles and spins as water
flows through the meter.
23. Turbomachinery – Dynamic Turbines
Dynamic turbines are used both as flow measuring
devices and as power generators. For example,
meteorologists use a three-cup anemometer to measure
wind speed.
A typical three-cup anemometer
used to measure wind speed
24. Turbomachinery – Dynamic Turbines
Dynamic turbines those for witch the working fluid is water can be called
hydroturbines. There are two basic types of hydroturbines —impulse and reaction.
Comparing the two power-producing dynamic turbines, impulse turbines require a
higher head, but can operate with a smaller volume flow rate. Reaction turbines can
operate with much less head, but require a higher volume flow rate.
Hydro
Turbines
Impulse
Turbine
Reaction
Turbine
25. Turbomachinery – Impulse Turbines
In an impulse turbine, the fluid is sent through a
nozzle so that most of its available mechanical
energy is converted into kinetic energy. The high
speed jet then hits on bucket-shaped vanes that
transfer energy to the turbine shaft.
The modern and most efficient type of impulse
turbine was invented by Lester A. Pelton (1829–
1908) in 1878, and the rotating wheel is now called
a Pelton wheel in his honor.
26. Turbomachinery – Impulse Turbines
A close-up view of a Pelton
wheel showing the detailed
design of the buckets; the
electrical generator is on the
right.
27. Turbomachinery – Impulse Turbines
A view from the bottom of an
operating Pelton wheel
illustrating the splitting and
turning of the water jet in the
bucket. The water jet enters
from the left, and the Pelton
wheel is turning to the right.
28. Turbomachinery – Reaction Turbines
The other main type of energy -producing hydroturbine is the
reaction turbine, which consists of fixed guide vanes called
stay vanes, adjustable guide vanes called wicket gates, and
rotating blades called runner blades.
Flow enters tangentially at high pressure, is turned toward the
runner by the stay vanes as it moves along the spiral casing or
volute, and then passes through the wicket gates with a large
tangential velocity component.
29. Momentum is exchanged between the fluid and the runner as the runner rotates, and
there is a large pressure drop. Unlike the impulse turbine, the water completely fills
the casing of a reaction turbine.
For this reason, a reaction turbine generally produces more power than an impulse
turbine of the same diameter, net head, and volume flow rate. The angle of the
wicket gates is adjustable so as to control the volume flow rate through the runner.
Turbomachinery – Reaction Turbines
30. There are two main types of reaction turbine—Francis and Kaplan.
The Francis turbine is somewhat similar in geometry to a centrifugal flow pump,
but with the flow in the opposite direction.
In contrast, the Kaplan turbine is somewhat like an axial-flow fan running
backward.
Turbomachinery – Reaction Turbines
Reaction
Turbines
Francis Kaplan
32. Turbomachinery – Reaction Turbines
The runner of a Francis radial-flow turbine used at the
Round Butte hydroelectric power station in Chennai.
There are 17 runner blades of outer diameter 11.8 ft
(3.60 m). The turbine rotates at 180 rpm and produces
119 MW of power at a volume flow rate of 127 m3/s
from a net head of 105 m.
33. Turbomachinery – Reaction Turbines
The five-bladed propeller of a Kaplan
turbine used at the Warwick
hydroelectric power station in Cordele,
Georgia, United States. There are five
runner blades of outer diameter 12.7 ft
(3.87 m). The turbine rotates at 100
rpm and produces 5.37 MW of power
at a volume flow rate of 63.7 m3/s
from a net head of 9.75 m.
34. Turbomachinery – Wind Turbines
Numerous innovative wind turbine designs have been proposed and tested over the
centuries. We generally categorize wind turbines by the orientation of their axis of
rotation
Wind
Turbines
Horizontal Axis
Wind Turbines
(HAWT)
Vertical Axis
Wind Turbine
(VAWT)
