36 ENGINE TESTS. 



compound engine, we may take the case of Engine No. 32, in 

 which the ratio of volumes of the cylinders is as 1 to 3.43, and 

 the mean effective pressure in the two cylinders 41.26 Ibs. and 

 9.28 Ibs. respectively. The equivalent m.e.p. to be used in 

 computing the steam accounted for in the H. P. cylinder is 

 46.26 + (9.28 x 3.43) = 41.26 + 31.83 = 73.09. For the low- 



41.26 

 pressure cylinder the quantity is 9.28 X t , <9 = 9.28 4- 12.03 



= 21.31. 



As an example of this method applied to a triple expansion 

 engine we may take the case of Engine No. 59, in which the 

 ratios of volumes are as 1 to 2.94 to 6.5, and the mean effec- 

 tive pressures, 60.56 Ibs., 13.22 Ibs., and 10.16 Ibs. respectively. 

 The quantity to be used for the H. P. cylinder is 60.56 + 

 (13.22 x 2.94) + (10.16 x 6.05) = 60.56 + 38.87 + 66.04 = 

 165.47. The quantity for the intermediate cylinder is 13.22 Ibs. 



+ T5 + (10 ' 16 x ^l> == 20 * 6 + 18 ' 22 + 22>4( ' = r>6 ' 28 - 



For the low-pressure cylinder the quantity is 10.16 + (13.22 x 

 J|^L ) + k| = 9.32 + 5. 98+ 10.16 = 25.46. 



The weights of steam per cubic foot used in the formulae for 

 determining the steam accounted for in the tests under con- 

 sideration are those deduced from Regnault's experiments as 

 given in D. K. Clark's Manual. 



The following examples will serve to illustrate the use of 

 the formulae, one case being a single expansion engine and the 

 other a triple expansion. 



Engine No. 22, Simple Condensing Engine. 



Clearance 2 % 



Cut-off pressure above zero 75.6 Ibs. 



Weight per cubic foot at cut-off pressure .1773 



Release pressure ]">."> 



Weight per cubic foot at release pressure .0399 



Mean effective pressure 37.17 



Compression pressure 3 



Weight per cubic foot at compression pressure .0085 



