STEAM TURBINE.ppt

8/14/2019 STEAM TURBINE.ppt

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Prof Ir Dr. Ab Saman b. Abd Kader, PEng, MIEM,MCIT

Faculty of Mechanical Engineering, UTM


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A steam turbine is a mechanical devicethat extracts thermal energy from

pressurized steam, and converts it into

rotary motion. It has almost completely replaced the

reciprocating piston steam engine

primarily because of its greater thermalefficiency and higher power-to-weight

ratio.


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continue. Because the turbine generates rotary motion,

it is particularly suited to be used to drive anelectrical generatorabout 80% of allelectricity generation in the world is by use ofsteam turbines.

The steam turbine is a form of heat enginethat derives much of its improvement in

thermodynamic efficiency through the use ofmultiple stages in the expansion of the steam,which results in a closer approach to the idealreversible process.


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2 main type of turbine :- IMPULSE

REACTION


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The impluse arrangement is made up of a ringof nozzles followed by a ring of blades.

Due to this higher ratio of expansion of steam in

the nozzle the steam leaves the nozzle with avery high velocity.

This jet of steam is directed into the impulse

blades and leaves in a different direction (Figure1.0).

There is only a very small end thrust on theturbine shaft.


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FIGURE 1.0 : IMPULSE BLADING


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The reaction arrangement is made up of a ringof fixed blades attached to the casing.

A row of similar blades mounted on the rotor, i.e.moving blades (Figure 1.2)

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The blades are mounted and shaped to producea narrowing passage.

A change in velocity of the steam as a result of achange in direction and an impulsive force isalso produced with this type of blading.

The more correct term for this bladearrangement is impulse-reaction.


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PARSONS - a reaction turbine where steamexpansion takes place in the fixed and moving blades.

CURTISan impulse turbine with more than one row

of blades to each row of nozzles.

De Lavala high-speed impulse turbine which hasonly one row of nozzles and one row of blades.

Rateauan impulse turbine with several stages, eachstage being a row of nozzles and a row of blades.


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The construction of an impulseturbine is shown in Figure 1.3.


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FIGURE 1.3 : IMPULSE TURBINE


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1. ROTOR

acts as the shaft which transmits the mechanicalpower produced to the propeller shaft via thegearing.

2. BLADES

When the turbine rotor is rotating at high speedthe blades will be subjected to considerablecentrifugal force and variations in steam velocityacross the blades will result in blade vibration.


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provides the various low-pressuresteam supplies and extraction

arrangements for all the glands in theturbine unit (Figure 1.4).


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FIGURE 1.4 : GLAND STEAM

SEALING SYSTEM


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Only impulse turbine have diaphragms.

Diaphragms are circular plates made up of twosemi-circular halves.

Fits between the rotor wheels and is fastenedinto the casing.

The nozzles are housed in the diaphragm around

its periphery. The central hole in the diaphragm is arranged

with projections to produce a labyrinth gland.


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Serve to convert the high pressure and high

energy of the steam into a high-velocity jet ofsteam with a reduced pressure and energycontent.

The steam inlet nozzles are arranged in severalgroups with all but the main group havingcontrol valves.

In this way the power produced by the turbinecan be varied.

Both impulse and reaction turbines have steaminlet nozzles.


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Serves two functions in a steamturbine :1. It provides an oil film

2. It removes heat generated in the bearings


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FIGURE 1.5 : LUBRICATING OIL

SYSTEM


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The valves which admit steam to the ahead or

astern turbines are known as manoeuveringvalves

3 valves - the ahead, the astern andthe

guarding or guardianvalve.

Operation of the ahead manoeuvring valve willadmit steam to the main nozzle box.

Operation of the asterm manoeuvring valve willadmit steam to the guardian valve.

Steam is then admitted to the astern turbines.


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Is provided with all installations to prevent

damage resulting from an internal turbine fault.

Arrangements are made in the system to shutthe turbine down using an emergency stop and

solenoid valve.

Operation of this device cuts off the hydraulic oilsupply to the manoeuvring valve and thus shuts

off steam to the turbine.


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This main trip relay is operated by a number of

main fault conditions which are :1. Low lubricating oil pressure.

2. Overspeed.

3. Low condenser vacuum.

4. Emergency stop.

5. High condensate level in condenser.

6. High or low boiler water level.


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1. Warming-through a steam turbine

2. Manoeuvring

3. Emergency astern operation4. Full away

5. Port arrival


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Thank you.

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STEAM TURBINE.ppt