ENGINE No. 51. 203 



Engine No. 51 is a horizontal cross compound, with jacketed 

 cylinders and a reheater. The condenser is of the siphon type, 

 and water is supplied by gravity. Both the barrel and the 

 heads of the high-pressure cylinder are jacketed, but only the 

 barrel of the L. P. cylinder. The reheater has sufficient sur- 

 face to superheat the steam, although not sufficient to prevent 

 some water condensing in the bottom of the shell, from which 

 it is drawn away by a trap. The jackets are drained by traps 

 which discharge to waste. The valves are all of the gridiron 

 tvpe. Steam is supplied from vertical boilers which super- 

 heat. The piston of the H. P. cylinder was found to show 

 some leakage. The low-pressure exhaust valve at the crank 

 end leaked quite badly. The piston of the L. P. cylinder and 

 the remaining valves were in good condition. Three tests 

 were made, using three different receiver pressures. 



These tests are of interest on account of the unusual ratio 

 of volumes of the cylinders. This ratio is about the same as 

 that which is common practice between the low-pressure and 

 high-pressure cylinder of a triple expansion engine. This 

 large ratio taken in conjunction with the high initial pressure, 

 and the fact that the steam was slightly superheated, furnishes 

 an explanation for the economical results obtained, which are 

 unusual. 



Comparing the three tests together, it appears that there was 

 a gradual improvement produced by increasing the receiver 

 pressure, the best result being obtained when that pressure was 

 the highest. 



In tliis connection, it is noticeable that as the receiver pres- 

 sure increased, and the cut-off in the low-pressure cylinder 

 tacame less, the steam accounted for by the low-pressure 

 cylinder became less. 



