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The various losses in steam turbines and their causes are as follows:

The expansion of steam through a number of stages of turbine is shown in Fig. 7.13. A1B1 represents isentropic expansion in the first stage. The actual state of steam with frictional reheating is shown by point A2. Therefore, the actual heat drop in the first stage is A1C1. Similarly, the isentropic and actual heat drops in the succeeding stages are…

The steam passes to the fixed blades with velocity va1. Fixed blades also act as nozzles with pressure drop occurring, while steam passes through them so that there is gain in kinetic energy and steam leaves the fixed blades with velocity va2. The expansion of steam and the enthalpy drop occur in fixed and moving blades. The…

1 Advantages 2 Limitations

Let u = circumferential or tangential linear velocity of blades    va1 = absolute velocity of steam at inlet of moving blade    va2 = absolute velocity of steam at outlet of moving blade    vw1 = velocity of whirl at the entry of moving blade       = va1 cos α1    vw2 = velocity of whirl at the exit of moving blade        = va2 cos α2    vf 1 = velocity of flow at inlet of moving…

If the entire pressure drop from boiler pressure to condenser pressure is carried out in a single stage nozzle, the velocity of steam entering the turbine blades will be very high and consequently, the turbine speed will be very high. Such high speed turbine rotors are not useful for practical purposes and a reduction gearing…

The comparison of impulse and reaction turbines is given in Table 7.1.   Table 7.1 Comparison of impulse and reaction turbines

On the basis of principles of operation, steam turbines are classified as follows:

A steam turbine works on the dynamic action of steam. Steam is caused to fall in pressure in a passage or nozzle. Due to this fall in pressure, certain amount of heat energy is converted into kinetic energy to give it high velocity. The high velocity steam impinges on the moving blades of the turbine…