Lect No 01

1. Unit No:02
Energy Conversion Devices
Prof. Yash B. Parikh
M.Tech (Computer Integrated Manufacturing)
B.E.(Mechanical Engineering)
Assistant Professor
Department of Mechanical Engineering

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3. Preface
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 When you go to an airport and see the commercial
jets there, you can't help but notice the huge engines
that power them.
 Most commercial jets are powered by turbofan
engines, and turbofans are one example of a general
class of engines called gas turbine engines.
 You may have never heard of gas turbine engines,
but they are used in all kinds of unexpected places.
 For example, they are used in many of the
helicopters, smaller power plants and even in the M-1
Tank.

4. History
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 The word "turbine" was coined in 1822 by the French
mining engineer Claude Burdin.
 It’s derived from the Latin word turbo, which means
a spinning object.
 During the 18th and 19th centuries, much progress
was made toward extracting the kinetic energy of
flowing water.
 This in turn devised water turbines.

5. Introduction
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 Turbines are devices that spin in the presence of a
moving fluid.
 A turbine looks like a large wheel with many small
radiating blades around its rim.
 There are four broad classes of turbine:
water (hydraulic), steam, wind, and gas.
 The most important application of the first three is
the generation of electricity; gas turbines are most
often used in aircraft.

6. Steam Turbine
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 Most power plants use coal, natural gas, oil or
a nuclear reactor to create steam.
 A steam turbine is a rotary machine which is
designed to convert the energy of high pressure and
high temperature steam into mechanical power.
 The steam runs through a huge and very carefully
designed multi-stage turbine to spin an output shaft
that drives the plant's generator.

7. Principle of Operation of Steam Turbine
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 The high pressure-low velocity steam is first
expanded in a passage (called as a nozzle) which
converts the steam into low pressure-high velocity jet
of steam.
 The resultant high velocity steam is passed over the
curved vanes (or blades).
 Due to this, there is a change in momentum and it
will exert a resultant force on the blades.
 These blades are attached to a disc on a shaft which
is free to rotate.
 The resultant force cause the rotor to rotate, and
thus the power is developed.

8. Types of Steam Turbine
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 There are mainly two types of steam turbines :
1. Impulse Turbines
2. Reaction Turbines

9. Impulse Turbine
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 These turbines use the principle of impulse.
 In which the stationary nozzles are used to exert a
force on a ring of moving blades.

10. Impulse Turbine
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 Impulse turbines convert the kinetic energy of a jet
of water to mechanical energy.
 e.g. Pelton Wheel

11. Reaction Turbine
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 Reaction turbines convert potential energy in to
mechanical energy.
 Reaction turbines develop torque by reacting to the
fluid's pressure or mass.

12. Reaction Turbine
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 These turbine does not use nozzles.
 Water flow is radial from exterior to interior.
 Flow changes gradually from radial to axial.
 The pressure of the fluid changes as it passes
through the turbine rotor blades.

13. Reaction Turbine
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 The overall efficiency of a reaction turbine is slightly
higher than the equivalent impulse turbine for the
same thermal energy conversion.
 e.g. Kaplan Turbine, Francis Turbine.

14. Difference between Impulse & Reaction Turbine
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 In an impulse turbine entire pressure energy is
converted in to kinetic energy (as in case of a pelton
turbine where the nozzle does this).
 In a reaction turbine only a part of the pressure
energy is converted to kinetic energy (as in case of
Francis and Kaplan turbines.)
 Impulse turbine is less efficient compared to reaction
turbine.
 In impulse turbine we get as high as 30,000 rpm
speed of rotor which is very difficult to handle.
 In reaction turbine rotor speeds are relatively low.
 Impulse turbines occupies less space than reaction
turbines.
 Impulse turbines are used for small scale applications

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16. Introduction
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 A gas turbine is an extension of the same concept
as that of steam turbines.
 In a gas turbine, a pressurized gas spins the turbine.
 In all modern gas turbine engines, the engine
produces its own pressurized gas, and it does this by
burning something like propane, natural gas,
kerosene or jet fuel.
 The heat that comes from burning the fuel expands
air, and the high-speed rush of this hot air spins the
turbine.
 Gas turbines are used to produce large quantities of
power in a self contained and compact unit.
 It has got low weight to power ratio than that of
I.C.Engines.

17. Introduction
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 Wind turbines, also known as wind mills, use the
wind as their motive force.
 A wind turbine looks nothing like a steam turbine or a
water turbine because wind is slow moving and very
light, but again, the principle is the same.