270 ENGINE TESTS. 



46. Test No. 46 B on this engine gave a feed-water consump- 

 tion of 21.59 Ibs. This may be compared with Engine No. 2, 

 which was run non-condensing at a pressure of 101 Ibs., and 

 gave 25.8 Ibs. consumption. Here the economy due to the 

 compound engine is 4.21 Ibs., or 16.3%. This is rather unfav- 

 orable to the compound engine on account of the relatively 

 small difference in the boiler pressures. 



Referring to the single-valve engines running condensing, 

 comparison may be made between Engine No. 41 and Engine 

 No. 19. Engine No. 19, the simple engine, used 27.15 Ibs. per 

 I. H. P. per hour, and Engine No. 41 B, compound, used 19.1 

 Ibs., the difference being 8.05 Ibs., or an economy of 29.6%. 

 There are no single-valve engines of the non-condensing class 

 from which to make a fair comparison between the com- 

 pound and simple engines, owing to the great difference in the 

 sizes ; but the results obtained on engines of this kind, disre- 

 garding their size, are of the same kind as those already 

 discussed. 



The results of the tests on the two triple expansion engines 

 which are given, show an average consumption of 12.63 Ibs. 

 of water per 1. H. P. per hour. This is below the average of 

 14.12 Ibs. for the various compound condensing engines which 

 are tabulated, and it is below the result obtained from any 

 individual engine given in that table. It is better to the ex- 

 tent of 10%, compared with the average. This result is not, 

 however, so good as that obtained from the special com- 

 pound Engine No. 51, where the ratio of cylinder areas is 

 about the same as the ratio between the low-pressure cylinder 

 and the high-pressure cylinder of triple expansion engines. 



VII. ECONOMY OF STEAM JACKETING AND RE-HEATING IN 

 COMPOUND 1 : N G I N ES. 



There are two compound engines given where the effect of 

 shutting off the steam from the jackets and re-heater tubes 

 was tested, these being No. 47 and No. 52. In each of these 

 cases, the difference in the feed-water consumption per I. H. P. 



