156 ENGINE TESTS. 



Engine No. 39 is a single valve, cross compound, unjacketed 

 engine, with a shaft governor operating on the cut-off of the 

 high-pressure cylinder. The valves are of the piston type pro- 

 vided with an inefficient ring packing. A jet condenser is 

 used, operated by an independent air-pump driven with steam 

 taken from the engine pipe. The quantity thus used was 

 determined by an independent test and allowed for. Steam is 

 supplied from vertical water- tube boilers, and a separator placed 

 in the steam pipe secured what was believed to be commercially 

 dry steam without superheating. The valves and pistons all 

 leaked a considerable amount. The load consisted of dynamos 

 furnishing current for electric lighting. With the exception 

 of the low-pressure cylinder and the valves, this engine is 

 the same as No. 35. During the interval between the tests the 

 engine had been provided with new valves fitted with packing 

 and a complete new low-pressure cylinder of larger size. 



Referring to the test on Engine No. 35, the figures given here 

 show an improvement, due largely to a better distribution of 

 the steam, which was accomplished by a change of proportion 

 in the steam cylinders. The increase in the size of the low- 

 pressure cylinder enabled this cylinder to do a larger proportion 

 of the work, with corresponding advantage. The reduction 

 in the quantity of feed water consumed per horse power per 

 hour amounted to 18.3% ; and the reduction in the steam 

 accounted for by the diagrams at cut-off, which is 17.5%, fur- 

 nishes a reason for the change. In view of the leakage of the 

 valves and pistons, it is not surprising that the proportion of 

 steam accounted for is low ; and this is true in the case of both 

 engines. 



To make a ready comparison of the diagrams in the two 

 cases under consideration, showing the general effect of the 

 change of cylinders, diagrams from Engine No. 35, taken with 

 the same load, are superposed in dotted lines upon those relat- 

 ing to No. 39, which are represented in full lines. 



