File:Applied thermodynamics for engineers (1913) (14764044934).jpg

Identifier: appliedthermodyn01enni (find matches)
Title: Applied thermodynamics for engineers
Year: 1913 (1910s)
Authors: Ennis, William Duane, 1877-
Subjects: Thermodynamics
Publisher: New York, Van Nostrand
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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three drums,and the fixed buckets project inward from the casings. The diameters of thedrums increase by steps; the increasing volume of the steam within any section isaccommodated by varying the bucket heights. Tlie balance pistons P, P, P areused to counteract end thrust. The speed is fairly high, and special provisionmust be made for it in the design of the bearings. Governing is effected by inter-^mittently opening the valve T; this valve is wide open whenever open at all. The length of this machine is sometimes too great for convenience. To over-come this, the double-flow turbine receives steam near its center, throughexpanding nozzles which supply- a simple Pelton impulse wheel. This utilizesa large proportion of the energy, and the steam then flows in both directionsaxially, through a series of fixed and moving expanding buckets. Besides reduc-ing the length, this arrangement practically eliminates end thrust and the neces-sity for balance pistons. APPLICATIONS OF TURBINES 391
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392 APPLIED THERMODYNAMICS 540. Applications of Turbines. Turbo-locoraotives have been experimentedwith in Germany; the direct connection of the steam turbine to high-pressurerotary air compressors has been accomplished. In stationary work, the directdriving of generators by turbines is common, and the high rotative speeds of thelatter have cheapened the former. At high speeds, difficulties may be experi-enced with commutation; so that the turbine is most successful with alternating-current machines. When driving pumps, turbines permit of exceptionally highlifts with good efficiencies for the centrifugal type, and low first costs. For low-pressure, high-speed blowers, the turbine is an ideal motor. (See Art. 239.) Theoutlook for a gas turbine is not promising, any gas cycle involving combustion atconstant pressure being both practically and thermodynamically inefficient. The objections to the turbine in marine application have arisen from the highspeed and the difficulty of reversing.

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