. Electric railway review . ibrium. In small machines, however, the advan-tages of the double-flow principle are not as pre-eminent as inthe large, principally because of the absence of the necessitytherefor from a mechanical standpoint, and by reason of thefact that the economy of two small machines is not likely to May 30, 190S. ELECTRIC RAILWAY REVIEW 643 be as good as one of twice the capacity. In turbines of verylarge size, however, where proportions exist more favorableto the attainment of high economy, the latter advantage doesnot obtain. The double-flow turbine may thus be regarded as
. Electric railway review . ibrium. In small machines, however, the advan-tages of the double-flow principle are not as pre-eminent as inthe large, principally because of the absence of the necessitytherefor from a mechanical standpoint, and by reason of thefact that the economy of two small machines is not likely to May 30, 190S. ELECTRIC RAILWAY REVIEW 643 be as good as one of twice the capacity. In turbines of verylarge size, however, where proportions exist more favorableto the attainment of high economy, the latter advantage doesnot obtain. The double-flow turbine may thus be regarded as theresult of an insistent demand for turbine-generating units of illustration that since the two elements are identical, and thesteam flows through them in opposite directions, the axialthrust of the steam on the blades, due to the difference ofpressure between the inlet and outlet of each element, will beexactly the same in both sections. Therefore, perfect steambalance under all conditions of pressure, vacuum and load, is. Westinghouse Double-Flow Turbines—Interior of Brunot Island Station of the Pittsburg Railways Company, Showing Turbines During Erection. larger capacity at high speeds. For the large machines, theadvantages of the combined impulse and reaction principle ofsteam expansion, together with the double-flow construction,are so important that the practical result, as embodied in themachine under description, is most fortunate. The Parsonsand the double-flow type are practically upon the same basis obtained without the use of dummy or balance pistons. Asthese low-pressure turbines are designed to utilize all theexhaust steam from a non-condensing reciprocating engine, itis possible to tie the engine and turbine together electrically,thus making the use of a governor on the low-pressure turbineunnecessary. With the exception that, as mentioned, the gov-
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