This is problem 5-17 from El-Wakil’s Powerplant Technology book-- consider a simple combination turbine with one Delaval impulsestage and one 60 percent reaction stage. The nozzle of impulsestage receives steam at 900 psia and 900°F and leaves it at 300psia. The nozzle efficiency is 97 percent and its angle is 20°. Theblade speed is optimum and its velocity coefficient is 0.95. Theimpulse stage is followed on the same shaft by the reaction stagewhich exhausts to 100 psia. The steam entrance angles for thatstage are also 20°. The efficiency of the fixed blades (nozzles) is90 percent. Because of different diameters of the impulse andreaction moving blades, the velocity of the reaction blade is 1.5that of the impulse blade. (a) Determine all steam velocities anddraw the velocity diagram of the combined turbine, (b) calculatethe work of each stage, in Btus per pound mass, and (c) calculatethe individual stage and the turbine efficiencies.
