Gas-Engine Indicator- Diagram. 73 



50 per cent, is correct, we are still not in a position to state 

 the total loss of heat from the cylinder. 



It is to be remembered that W is the indicated work. The 

 useful work of a gas-engine, given out by the crank-shaft, is 

 about 0*8 W, there being an expenditure of 02 W in over- 

 coming the mechanical friction of the engine. 



10. It is unnecessary to put before the Society the curves 

 obtained by us by employing (6) on the discontinuous expres- 

 sions of § 7 for the indicator-diagrams. 



11. Rate of Loss of Heathy the Fluid during Compression. — 

 For the compression part of the diagrams, 



7=1-385, 

 and 



p= 39-36 Z 1 " 304 . 

 Rate at which heat is received by fluid is — q, if 



and by § 8, 



36-36 Z 1,304 O-7) 



-q=- ^ LL 



7-1 



-q = l l '* u 39-36 x 



m— 7 



7-1 ' 



m-7=--081, 



7-l = -385. 



Therefore the rate at which heat is received by fluid is 



-0-2104^, 



being proportional to the pressure, and is negative — that is, 

 the fluid is radiating heat to the cylinder. 



12. Rate at which Fluid radiates Heat to cold Cylinder. — 

 It was found by the pyrometric measurements of Messrs. 

 Brooks and Steward that the temperature of the products of 

 combustion in the clearance-space, if there has been a recent 

 explosion, is about 410° C. ; and for the purpose of deter- 

 mining the temperature of the fluid before compression, they 

 take 1*4 volume of coal-gas and 9*25 of air at 22° C. with 

 7*94 volumes of products of past combustions at 410° C, from 

 which, assuming that the specific heats of the constituents do 

 not alter with temperature, they find that the temperature of 

 the mixture before compression is 120° C. This is sufficiently 

 correct for our present purpose, and if we take it as the tempe- 

 rature when l = 2'222 y .p =14t'7 , we can find the temperature 

 corresponding with any point of any of the indicator-diagrams. 



