A OENTUKy's 1'KUC4RESS <»F THE STEAM ENGINE. CO] 



rise of the pressure to 1.0<iO po.md.. would oive uppioximat.dy 87 5 

 per^c-ent efficiency. Meantime the expendituiv in heat units uculd 

 be 7.500 per horsepower per hour; that of steam, at 1,000 units per 

 pound would be 7.5: and that of fuel about 0.75 pound at the l.,wer 

 pressure: while at tht> higher these fi.oures would become 5.000 B. T. I'., 

 5 pounds of steam, and 0.5 pound of good fuel l)urncd in a hell,.,- . it- 

 high efficiency. 



The Rankine cycle, defective in its lack of that cojupression wlii.-h 

 is an essential characteristic of the Carnot cy«-k\ gives constants in our 

 equations about -20 per cent above those of the latter, measuring licat, 

 steam, and fuel consumption, and proportionally lower in measures of 

 efficiency. Where heat wastes occur, as in the real case, to the extent 



8 10 S 10 12 11 1« 18 20 22 24 20 i« 30 



THOUSANDS B.T.U.AND LBS.STEAM (S 1000 B.T.U.EACH PER H.P. PER HOUR 

 FIG. 6.— GAIN IN EFFICIENCY 



of 20 per cent or more, these variations from tlie ideal ease become 

 proportionately increased. The expenditures of the best eugiiu's will 

 average, in this case, probably 20 per cent internal wast<> and the con- 

 stants become about 18,000 and 22,0(X) for the ideal and th(> real case, 

 respectively, as measuring heat expenditure, and 15 and is foi- the 

 constant in the measure of efficiency. 



Fig. shows, on this basis, the Ideal limit of the Carnot i-yele. me:i^ 

 uring efficiency by expenditure of heat in thousands H. T. T., costs in 

 steam and in fuel being computed on the assumption of l,o<>o H.T. V. 

 per pound, and 10 pounds evaporation ]wv pound of best fuel in the 

 best steam boilers. 



The scale and diagrams are constru.ted f..r a pres.s.ire limit ..f 5oo 



pounds per sijuare inch. 



