68 Professors Ayrton and Perry on the 



quite straight, so that 



the ignition part of curve is (a + b\)/cl- m , . . (4) 



the expansion part of curve is Kl~ m (5) 



In our diagrams, 



k= 145-5, m = 1-479; 



Also a=0*257. 



Incurve ABC D, 6 = 4'372: 



„ AED, 6 = 1-457 



„ AFD, 6=0-782: 



„ AGH, 6 = 0-313. 



To use formula (4) in any given case. Find by the method 

 already given in § 4 the constants of equation (5) to the ex- 

 pansion part. Assume that the ignition is complete when 

 X=\ v Let the pressure at the beginning of the stroke be p ; 

 calculate the value of /cl~ m when X = 0, that is, when Z = clear- 

 ance or l , say; then 



p -i-fclo~ m is a, 

 and 



a + b\± = 1; 



or a=^l: and b- 



8. The Rate at ivhich the Fluid receives Heat as calculated 

 from its Volume and Pressure. — We shall now proceed to cal- 

 culate the heat received by the fluid. This we shall do as if, 

 instead of there being combustion going on among the par- 

 ticles of the fluid, we had the fluid a perfect gas receiving 

 heat from a great number of little furnaces, or pieces of hot 

 wire immersed in the fluid. Besides the heat here considered 

 we have the heat radiated to the cold cylinder. 



If A is the area of the piston in square inches,^ the pressure 

 of the fluid in pounds per square inch, and 2 the distance 

 moved through by piston in feet, the work done by the fluid 

 on the piston in an element of length dl is 



Ap dl foot-pounds. 



It is evident that if we represent the heat which is received 

 by the fluid in the length dl by 



Aq dl foot-pounds, 



so that \—a 



Po 



K 







