. Applied thermodynamics for engineers. he absolute exit velocity, iLmoring friction, \^ v — 2 u. The chans^e in ^^^- ^^^ ^^^^- ^^^ ^^^• 1 •. • \. X -, .1 1 ton Bucket, velocity IS v-\-v — Zu = 2{v-~?t), and the work Pel- is 2u{^— u) -^ g, whence the efficiency. 4:u(v— u) becomes a maximum at 100 per cent when upracticable. Complete reversal in turbine buckets is im- 530. Single-stage Impulse Turbine. The absolute velocity of steam enter-ing the buckets is computed from the heat drop and nozzle friction losses. In a turbine of this type, the speed of thebuckets can scarcely be made equalto
. Applied thermodynamics for engineers. he absolute exit velocity, iLmoring friction, \^ v — 2 u. The chans^e in ^^^- ^^^ ^^^^- ^^^ ^^^• 1 •. • \. X -, .1 1 ton Bucket, velocity IS v-\-v — Zu = 2{v-~?t), and the work Pel- is 2u{^— u) -^ g, whence the efficiency. 4:u(v— u) becomes a maximum at 100 per cent when upracticable. Complete reversal in turbine buckets is im- 530. Single-stage Impulse Turbine. The absolute velocity of steam enter-ing the buckets is computed from the heat drop and nozzle friction losses. In a turbine of this type, the speed of thebuckets can scarcely be made equalto half that of the steam; a moreusual proportion is The velocityu thus seldom exceeds 1400 ft. persecond. Fixing the bucket speed andthe absolute entering angle of thesteam (usually 20°) we determinegraphically the entering angle of thebucket. The bucket may now be de-signed with equal angles, which wouldeliminate end thrust if there were noFig. 253. Art. 530. —Bucket Outline. friction, or, allowance being made for. 376 APPLIED THERMODYNAMICS friction, either end thrust or the rotative component of the absolute exit velocitymay be eliminated. The normals to the tangents at the edges of the buckets being drawn, as ec, Fig. 253,the radius r is madeequal to about thickness t maybe made equal to the width bucket as thusdrawn is to a scale asyet undetermined;the widths kl vary inpractice from inch. (Porastudyof steam trajectoriesand the relation there-of to bucket design,see Roe, Steam Tur-bines, 1911.) It should be notedthat the hack, ratherthan the front, of thebucket is made tan-gent to the relativevelocity V. The work,per pound of steambeing computed fromthe velocity diagram,and the steam con-sumption estimatedfor the assumed out-put, we are now in aposition to design thenozzle. 531. Multi-stageImpulse Turbine. Ifthe number of pres-sure stages is few, asin the Curtis type, theheat drop may be di-vided equally betweenthe
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