. The steam-engine and other heat-motors. s and the volumes that are in communicationat such critical positions (Figs. 159 and 160). Cross-compound Engines.—Draw the cards from a cross-com-pound engine, crank leading; rotation clockwise; initial pres-sure cyl., 180 pounds abs.; number of expansions, 30; ratioof cylinder volumes, 6 to 1; volume of cyl., 5 cu. ft.; volumeof receiver, 10 cu. ft.; cut-off on cyl., 1/3 stroke; back pressurein cyl., 1 pound abs. Volume of cyl. =6x5 = 30. 30Volume of cyl. at cut-off = ^ = 1 cu. ft. 5Ratio of expansion in cyl. =
. The steam-engine and other heat-motors. s and the volumes that are in communicationat such critical positions (Figs. 159 and 160). Cross-compound Engines.—Draw the cards from a cross-com-pound engine, crank leading; rotation clockwise; initial pres-sure cyl., 180 pounds abs.; number of expansions, 30; ratioof cylinder volumes, 6 to 1; volume of cyl., 5 cu. ft.; volumeof receiver, 10 cu. ft.; cut-off on cyl., 1/3 stroke; back pressurein cyl., 1 pound abs. Volume of cyl. =6x5 = 30. 30Volume of cyl. at cut-off = ^ = 1 cu. ft. 5Ratio of expansion in cyl. = y = 5. M VI. TIPLE-EX P. IXSION ENGIXES. 311 30The volume of cyl. at cut-off = — =10 cu. ft. o The constant mass passing through the cycle or Px Vx = 180 X1 =» ISO. The pressure at cut-off in the cyl. must equal 18010 18 pounds = H. Lay off AB= ISO pounds; AC=; £D = : then- 180 ISO EF = -^- = 3Q pounds and C^ = ^r^6 pounds, and the ordinate at H is laid off for 18 pounds. Join H and G by an hyperbola* 150-. Fig. 160. Check. The pressure at H is three times that at G. We must now find the volume of the cyl. that is exhaust-ing into the receiver at an instant before cut-off takes the length of the connecting-rod is to be considered, graphicconstruction will be found easier than by analysis. For simplicitywe shall assume infinite rods and obtain our results analytically. Draw the circular diagram (Fig. 160) in accordance with thedata. It is evident that ce represents the desired volume if ejrepresents the volume cf the cyl. *j ef ^ ei ef-ef. 312 TEE STEAM-ENGINE AND OTHER HEAT-MOTORS. hence da=oc = e/V (1/2)2-(1/6)2 = .47 ef,ec = .50ef-A7ef = Mef. The required volume is therefore .03 X 5 cu. ft. = .15 cu. ft. Hence the pressure in the cyl. at cut-off, in the receiverand in the cyl. when the piston of the latter has .15 cu. ft. of•exhaust-steam behind it is 18 pounds. Lay off A J =.15 cu. ft. and lay off an ordinat
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