The document discusses different types of impulse turbines. It begins by introducing impulse turbines and explaining that they rely on the dynamic action of steam passing through nozzles and imparting force on turbine blades. It then describes three main types of impulse turbines: simple impulse turbines where pressure remains constant; pressure compounded turbines which step down pressure in multiple stages; and velocity compounded turbines which step down velocity through alternating fixed and moving blades. Finally, it discusses pressure-velocity compounded turbines which consider both pressure and velocity changes in a multi-stage design.

1. TURBO MACHINERY
IMPULSE TURBINE
Mechanical Engineering Dept.
5th semester
CIT RAIPUR
By,
Indra Kumar Sarpar
Deepak Dhruw
Rohit Kumar Patwa
Vishal Sahu
Narendra Kumar Rajbhar

2. INTRODUCTION
 Steam Turbine is one of the most important prime mover for
generating electricity. This falls under the category of power
producing turbomachines.
 In the turbine, the energy level of the working fluid goes on
decreasing along the flow stream.
 The thermal efficiency of modern steam power plant above
120 MW is as high as 38% to 40%.
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3. PRINCIPLE OF OPERATION OF STEAM
TURBINE
 The steam turbine depends completely
upon the dynamic action of the steam.
 According to Newton’s second law of
motion, the force is proportional to the rate
of change of momentum (mass x velocity).
If the rate of change of momentum is
caused in the steam by allowing a high
velocity jet steam to pass over curved
blade, the steam will impart a force to the
blade. If the blade is free, it will move off
(rotate) in the direction of force.
 In fig.8.1(a)
C1 = Initial velocity, C2 = Final velocity
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4. WORKING PRINCIPLE:-
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5. CLASSIFICATION OF STEAM TURBINE
Impulse Turbine
Impulse-reaction Turbine
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6. IMPULSE TURBINE
 The basic idea of an impulse turbine is that a jet of stream
from a fixed nozzle pushes against the rotor blades and
impels them forward.
 The velocity of steam is twice as fast as the velocity of blade.
 Pressure drops take place in the fixed blade (nozzle).
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7. TYPES OF IMPULSE TURBINE
Simple Impulse Turbine.
Compounding of Impulse Turbine.
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8. SIMPLE IMPULSE TURBINE
It is the impulse turbine, where the steam expanded
within the nozzle and there is no any change in the
steam pressure as it passes over the blades.
It means that the pressure remain constant
through turbine.
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9. COMPOUNDING OF IMPULSE TURBINE
 Compounding is a method for reducing the rotational speed of the impulse
turbine to practical limits.
 If the high velocity of stream is allowed to flow through one row of moving
blades, it produces a rotor speed of about 30,000 r.p.m. which is too high
for practical use.
 Leaving loss is also very high. It is therefore essential to incorporate some
improvement in the simple impulse turbine for possible by making use also
to achieve high performance.
 This is possible by making use of more than one set of nozzles, blades,
rotors, in a series keyed to a common shaft, so that either the steam
pressure or the jet velocity is absorbed by the turbine in stages.
 The leaving loss also will than be less.
This process is called compounding of steam turbine.
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10. TYPE OF COMPOUNDED IMPULSE
TURBINE
 Pressure Compounded Impulse Turbine
 Velocity Compounded Impulse Turbine
 Pressure and Velocity Compounded Impulse Turbine
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11. PRESSURE COMPOUNDED IMPULSE
TURBINE
 In this type of turbine, the compounding is done for pressure of steam only i.e. to
reduce the high rotational speed of turbine the whole expansion of steam is
arranged in a number of steps by employing a number of simple turbine in a
series keyed on the same shaft.
 Each of these simple impulse turbine consisting of one set of nozzles and row of
moving blades is known as a stage of the turbine and thus this turbine consists of
several stages.
 The exhaust from each row of moving blades enters the succeeding set of nozzles.
 Thus we can say that this arrangement is nothing but splitting up the whole
pressure drop from the steam chest pressure to the condenser pressure into a
series of smaller pressure drop across several stages of impulse turbine and
hence this turbine is called Pressure – compound impulse turbine
 THIS IS ALSO KNOWN AS RATEAU TURBINE.
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12. ARRENGEMENT OF PRESSURE
COMPOUNDED IMPULSE TURBINE
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Nozzle
Moving
blade

13. VELOCITY COMPOUNDED IMPULSE
TURBINE
 In this type of turbine, the compounding is done for velocity of steam only
i.e. drop in velocity is arranged in many small drops through many
moving row of blades instead of a single row of moving blades.
 In this turbine, moving and fixed blades ( guide blades ) are placed
alternately.
 Moving blades are fitted with the wheel while the fixed blades are
fitted with the casing.
 The whole expansion of steam from the steam chest pressure down to the
exhaust pressure take place in the nozzles only.
 Therefore pressure remain constant after nozzle.
 IT IS ALSO KNOWN AS CURTIS TURBINE.
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14. ARRANGMENT OF VELOCITY
COMPOUNDED IMPULSE TURBINE
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15. PRESSURE-VELOCITY COMPOUNDED
IMPULSE TURBINE
 Here we consider pressure and velocity simultaneously, hence it is
named as pressure velocity compounded impulse turbine.
 Here we have arrangement of two rotars or wheels.in each rotars we
have installation of many row of moving blades,hence we get a
decrease in velocity.
 Also we install two nozzles in whole arrangement, which helps in
splitting pressure.
 Here we use two row wheels as we consider two row wheels
arrangement more efficient than three row wheels arrangement.
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16. ARRANGEMENT OF P-V COMPOUNDED
IMPULSE TURBINE
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Moving
blade
Nozzle
Guide
blade

17. THANK YOU!
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