344 



PRACTICAL MATHEMATICS 



175. The Hypothetical Steam Engine Diagram. Steam is ad- 

 mitted into the cylinder at constant pressure p v the volume in- 

 creasing from to v v 



FIG. 114. 



Work done = ^ 



Let the steam then expand to volume v 2 according to the law 

 pv n = Const. 



Work done = ^h - (^TH 

 n 1|_ \v z / J 



If p 3 is the back pressure, Work done during exhaust = p s v z 



p 3 



work done = p,v-. + *{ 1 r l ~ n } p s v 2 , where r = 

 n I 1 Vj_ 



Total 



If p e = mean effective pressure 



Total work done = p e v 2 



and 



r ( 



w- 1 



If the law of expansion is pv = Const 



