Identifier: steamengineturbi01heck (find matches)
Title: The steam engine and turbine; a text-book for engineering colleges
Year: 1911 (1910s)
Authors: Heck, Robert Culbertson Hays, 1870-
Subjects: Steam-engines Steam-turbines
Publisher: New York, D. Van Nostrand company
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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r fixed or moving.Speaking approximately, the fixed vanes deliver a current at a velocityequal to that of the moving vanes, so that the steam can pass right intothe channel entrances between the latter; and the moving vanes deliverbackward steam which leaves the channels with a relative velocity aboutequal (but opposite) to the speed of the vanes themselves, or with anabsolute velocity of nearly zero. We here refer to component velocityin the direction of vane movement, as distinct from the general pro-gressive flow across the vane rows, or parallel to the axis of the rotor.The whole matter is discussed and graphically exhibited in Chapter IX,where it is shown that this turbine is not purely of the reaction type, butthat there is also some little impulse exerted by the current in enteringthe moving vane rows. (/) The Parsons Turbine. — Considering now the general drawingin Fig. 25, we note one important characteristic in the enlargement of 30 A GENERAL VIEW OF THE SUBJECT. (Chap. I.
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:3 CE o 1o o CI the rotor toward the low-pressure end: here the steam flows from rightto left. This enlargement, together with the increase in vane length,provides the necessary increase in cross area of steam channel. On theannular side of each step or section there will be a steam pressure which 4(/)) THE STEAM TURBINE. 31 will tend to force the whole rotor toward the left; further, there will be ahigher pressure on the right or entrance side of each vane row than onthe left or discharge side, and thus an additional force toward the left.To neutralize these forces, the balance discs or ^^pistons, Pi, P2, P3, areput on the right end of the rotor, and pressures are equalized throughthe passages Di, D2, D3. Since but half of the total pressure drop takesplace in the rotor vanes, the balance-piston diameters extend only tomid-length of the vanes. Leakage is minimized by a coUar-and-groovesurface of piston and casing, forming what is called a labyrinth packing(see Chapter X). The main co

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