The American Society of Mechanical Engineers

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56 TRANSACTIONS OF T H E A.S.M.E. JANUARY, 1941 Fio. 7 C r o s s S e c t i o n s T h r o u g h N o n c o n d e n s i n g T u r b i n e s f o r H i g h I n i t i a l P r e s s u r e s a n d T e m p e r a t u r e s ( A p p r o x im a te ly t o sc a le .)
WARREN—MODERN LARGE STEAM TURBINES FOR GENERATOR DRIVE 57 original designs, however, have been refined in certain ways as a result of this testing, and have been made much better from the mechanical standpoint as a result of operating experience with turbines in the interim. Some turbines have been built where condenser placement on the turbine operating level has perm itted a “stream flow” or “diffuser” type of exhaust hood. On these units vacuum measurements were obtained a t the last wheel which were greater than the vacuums existing in the condenser. These hoods have been in service for a number of years on several turbines in the Chicago district with great success, but generally this type of condenser arrangement has not been favored by station designers on account of the extra space and unconventional arrangement required, although a gain somewhat in excess of one per cent results. N o n c o n d e n s i n g T u r b i n e s Fig. 7 shows three sizes of noncondensing turbines for high pressures and tem peratures. These have been built in quite a number of cases to supply industrial process steam, or to operate as superposed turbines exhausting into existing lower-pressure condensing turbines. The first of these is for 10,000 kw to 15,000 kw capacity, 800 psi to 1200 psi pressure, and up to 900 F. This size machine generally requires no by-pass, and passes all of the steam through the first-stage wheel. The second is a recently designed machine for 15,000 kw to 20,000 kw capacity, for the same pressure range as the first, and up to 925 F. In this size a by-pass becomes advisable in order to secure the best possible light-load economy. The design shown is one of the latest involving an internal by-pass, which, as previously pointed out, perm its all of the steam to pass through the first-stage wheel at all loads. The third shows a type of machine which has been built for from 25,000 kw to 00,000 kw capacity, for a wide range of steam conditions up to 2300 psi pressure and up to 950 F. The first two of the foregoing machines are of the single-shell type. The third machine is of a type which was developed only a few years ago, and is known as the “double-shell” construction. I t has been successfully applied to a num ber of installations at high pressures and temperatures. Operating experience on seven of these turbines now in commercial service has been decidedly favorable. Trouble from steam leaks has not occurred. Shell distortions have been reduced to much less than ever previously experienced even in turbines at lower pressures and tem peratures. The dismantling of this type has been made easier owing to greater ease of handling the smaller shell bolts and the reduced shell distortions. Several other machines of this type are now being installed or manufactured. D e v e l o p m e n t o p D o u b l e S h e l l 10 Double-shell construction has had a rather interesting developm ent through four steps, the last of which is not yet in operation. The various steps in this design are shown in Fig. 8. Basically, the principle is to surround the working parts of the turbine with a steam tight inner shell carrying its own bolting flange, and to build around this a second shell. The space between the two shells is m aintained by communication with a lower stage in the turbine a t a pressure interm ediate between the intial pressure in the inner shell and the atmosphere. The total pressure drop is thus divided into two stages; neither shell 10 "Logan Double-Shell Turbine,” by G. B. Warren, Power, vol. 8 3 , 1937 p p . 3 0 2 -3 0 5 . ‘'53,000-Kw 3000-Iipm Superposed Turbine for Waterside Station,” by G. B. Warren, Combustion, vol. 9, 1938, pp. 27-32. F i o . 8 V a r i o u s D o u b l e - S h e l l D e s i g n s S h o w i n g S u c c e s s i v e D e v e l o p m e n t s
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Transactions of The American Societ
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Transactions of The American Societ
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W ILLIAM A. H ANLEY P r e s id e n
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The American Society of M echanical
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A.S.M.E. SOCIETY RECO RD S, PA R T
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A.S.M.E. SO CIETY RECO RD S, PA R T
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W. S. P a t terso n Heat Transfer (
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COLUMBUS Organized: 1920 Territory:
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MINNESOTA Organized: Minneapolis, 1
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SAVANNAH (Continued) E x e c u t iv
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A.S.M.E. SOCIETY RECO RD S, PA R T
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P IP E FLANGES AND FITTINGS (B16) (
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MINIMUM REQUIREM ENTS FOR PLUMBING
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A.S.M.E. SO CIETY R EC O RD S, PA R
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Index to Society Records, Part 1 Th
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The T ren d of A ir T ran sp o rtat
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ALLEN —T R E N D OF A IR TR A N S
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The American Society of Mechanical Engineers

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