. Official proceedings . most economical combination for a unit is the cross-compound Westinghouse reaction turbinewith the high-pressure portion running at 1500 revolutions andthe low-pressure portion at 750 revolutions. With this arrange-ment the highest efficiency is obtained, because with the largevolumes of steam required to develop the high power and theability to combine the unit into high—and low—pressure cylin-ders, running at 1500 and 750 revolutions per minute, gives thecondition for best blading proportions throughout the turbinewithout departing from standards of practic
. Official proceedings . most economical combination for a unit is the cross-compound Westinghouse reaction turbinewith the high-pressure portion running at 1500 revolutions andthe low-pressure portion at 750 revolutions. With this arrange-ment the highest efficiency is obtained, because with the largevolumes of steam required to develop the high power and theability to combine the unit into high—and low—pressure cylin-ders, running at 1500 and 750 revolutions per minute, gives thecondition for best blading proportions throughout the turbinewithout departing from standards of practice already estab-lished. This machine would be very remarkable for its highefficiencw which it is believed could not be reproduced withany other known form of turbine. The construction, however,is considerably heavier than a single unit, would be morecostly to construct and install. Economy, In order to compare the efficiencies which can l)e r)l)tainedwith the Curtis, Rateau. and Tarsons machines, reference is 92. made to Figs. 5 to 11 inclusive, and-to the consideration thatthe maximum efiBcicncy for certain blade speeds in any typeof turbine is dependent on (a) design of the blade elements,(b) the relative ratio of the velocity of the blades to the velocityof the steam (c) the capacity of the turbine, and (d) the operat-ing conditions. Let Sb = mean blade speed, Let Ss =: mean steam speed, Let E = blade efficiency. If steam is admitted to a wheel with one row of impulseblades (Fig. 5), at a certain speed, Ss, and the blades are re-volved at different speeds, Sb, theoretically, the efficiency is ata maximum for a certain blade speed given by the ratio. SI) mean blade speed I Ss mean steam speed 2 S„ For an\- other ratios of the efficiencv will be smaller. S«becoming zero when Sb = zero and when Sb = Ss- SbThe actual maximum efficiencv and the ratio ■ at which S,it is obtained depend mainly on the angles of the blades andthe frictional losses in the machine. Curve
Size: 1340px × 1864px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorrailwayc, bookcentury1900, bookdecade1900, bookyear1901
