256 



ENGINE TESTS. 



sation and leakage is much greater in the low-pressure cylinder 

 than in the H. P. cylinder. For example, reference may be made 

 to Engines No. 32, 36, 46A, 47A, 48B, 52D, and 53, in which 

 the proportions of cylinder condensation and leakage are as 

 follows : 



The average of these shows 10% more condensation and 

 leakage in the L. P. cylinder than in the H. P. cylinder. 



That leakage in itself produces an important effect in com- 

 pound engines is exhibited in the case of one engine reported, 

 that of No. 38, where the feed-water consumption per I. H. P. 

 per hour is 19.36 Ibs. The leakage here was in the low-pres- 

 sure piston ; and although the cylinders of the engine were j;i< -k- 

 eted, and the receiver also jacketed, the condensation and 

 leakage at cut-off in the H. P. cylinder was 32.5% against 

 17.5% by the simple-engine curve, and 57.0% at cut-off in the 

 L. P. cylinder ; the increase between the two cylinders being 

 24.5%. 



If we may judge from indications of one test, that of Engine 

 No. 26, the effect of leakage upon the consumption of steam 

 and economy of the engine may be exceedingly marked, and at 

 the same time have so little influence upon the lines of the 

 diagram that it may be scarcely noticeable. In this instance, 

 the form and position of the expansion line with reference to a 

 hyperbolic curve drawn through the cut-off point of the diagram 

 is so nearly the same that careful measurements would hardly 



