W3-i= pdv w\icv&pzvl=piv\ 



= 15.4X144X906- 

 = 607,000 ft. lb. 



-23.0X144X680 



I^5-i=^(z'i-^'o)=15.0X144(0-906) 

 = -1,960,000 ft. lb. 



(3) 

 (4) 



(5) 



The sum of equations (1) through (5) is 897,000 

 ft. lb., the work output. 



Similarly, the work input to a single supply cylinder 

 during one cycle of operation (one revolution) is 

 represented in figure b by the area bounded by the 

 p-v trace 6-7-8-9. Cylinder volumes at beginning 

 of compression, vy, and at end of compression, Vg, are 

 612 and 430 cubic feet, respectively, if the compression 

 process is assumed to be polytropic with ;2=1.30. 



Work, W, for individual processes is calculated as 

 follows: 



H^6-7=^(^'6-^'7) = 14.5X144(0-612) 



= -1,280,000 ft. lb. (6) 



W^7- 



_p7V7—psVi 

 8 — 1 



l — n 

 = 14.5X144X612—23.0X144X430 



-0.30 



= 477,000 ft. lb. 



(7) 



I^8-9=M^8-J'9) = 23.0 XI 44(430-0) 



= 1,423,000 ft. lb. (8) 



The sum of equations (6) through (8) is 620,000 

 ft. lb., the work input. 



Assuming a "diagram factor" (actual indicated 

 work-;-indicated work according to idealized p-v 

 diagrams) of 0.90, and assuming an over-all me- 

 chanical efficiency (accounting for friction losses) of 

 0.90, the net work output per revolution for the 

 four pairs of cylinders may be written 



0.90X0.90(897,000-620,000)X4=904,000 ft. lb. (9) 



Multiplying net work (equation 9) by 9 revolutions 

 per minute and dividing by 33,000 foot pounds per 

 horsepower-minute gives the net horsepower output 

 at the paddle shaft as 247: 



Net horsepower output= 



904,000X9 



33,000 



= 247 hp. 



U.S. GOVERNMENT PRINTING OFFICE: 1960 



For sale by the Superintendent of Documents, TJ.S. Qoverrunent Printing Office 

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