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This is problem 5-17 from El-Wakil’s Powerplant Technology book -- consider a simple combination turbine with...

This is problem 5-17 from El-Wakil’s Powerplant Technology book -- consider a simple combination turbine with one Delaval impulse stage and one 60 percent reaction stage. The nozzle of impulse stage receives steam at 900 psia and 900°F and leaves it at 300 psia. The nozzle efficiency is 97 percent and its angle is 20°. The blade speed is optimum and its velocity coefficient is 0.95. The impulse stage is followed on the same shaft by the reaction stage which exhausts to 100 psia. The steam entrance angles for that stage are also 20°. The efficiency of the fixed blades (nozzles) is 90 percent. Because of different diameters of the impulse and reaction moving blades, the velocity of the reaction blade is 1.5 that of the impulse blade. (a) Determine all steam velocities and draw the velocity diagram of the combined turbine, (b) calculate the work of each stage, in Btus per pound mass, and (c) calculate the individual stage and the turbine efficiencies.

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