Heat engineering; a text book of applied thermodynamics for engineers and students in technical schools . Fig. 145.—Velocity compounding. In the above figures it has been seen that when the steam isused on one blade the velocity of this blade has to be equal toone-half the velocity of whirl if a is fixed and /3 and 180 — ft arefixed. This means that the velocity of the wheel would be veryhigh. To reduce this, the velocity of whirl could be decreasedby decreasing the velocity from the nozzle. This is obtained by asmall drop in pressure in the nozzle. If steam is to be used through a large diffe
Heat engineering; a text book of applied thermodynamics for engineers and students in technical schools . Fig. 145.—Velocity compounding. In the above figures it has been seen that when the steam isused on one blade the velocity of this blade has to be equal toone-half the velocity of whirl if a is fixed and /3 and 180 — ft arefixed. This means that the velocity of the wheel would be veryhigh. To reduce this, the velocity of whirl could be decreasedby decreasing the velocity from the nozzle. This is obtained by asmall drop in pressure in the nozzle. If steam is to be used through a large difference in pressurethis would have to be utilized in a series of nozzles and is called pressure compounding. Another method is touse a series of movable and fixed blades as shown in Fig. 145,utilizing the high kinetic energy of discharge from one blade insuccessive blades. This is known as velocity compounding. 298 HEAT ENGINEERING The velocity diagrams are combined in Fig. 146, in which0 = 180 - ff0i = 180 - /3\In this the work per pound is: work = - a + 6 + ai + 6i A\. Fig. 146.—Combined diagram for velocities in a turbine with velocity compounding. The efficiency is: work 2c(a + b + a\ + 6i)
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