REVIEW OF FEED -WATER TESTS. 



IT could hardly be expected that conclusive information upon 

 the subjects which are of most interest in connection with the 

 operation of steam engines could be obtained from a large num- 

 ber of tests made on engines of various sizes, running under 

 different conditions of service, and located in plants which are 

 not always best adapted for experimental purposes or research, 

 like the tests under consideration. Such tests, however, cannot 

 but bring out some points on these subjects which are of consid- 

 erable practical value, if for no other reason than that the tests 

 were, in the main, conducted under those very circumstances of 

 practical operation which alone could give results of that nature. 



The tests furnish information in regard to cylinder condensa- 

 tion, leakage of valves and pistons, the effect of pressure and 

 speed, the economy of condensing and superheating, the relative 

 economy of simple, compound, and triple expansion engines, the 

 effect of steam jacketting and reheating, the effect of different 

 ratios of cylinder areas in compound engines, and some miscel- 

 laneous questions ; and these are discussed in the order named. 



I. CYLINDER CONDENSATION AND LEAKAGE. 



Cylinder condensation and leakage is that part of the feed- 

 water consumption which is not accounted for by the indicator 

 diagram. It is necessary to put these two losses in one class, 

 There is no way of separating them either absolutely or ap- 

 proximately. The only practicable thing to do is to test the 

 valves and pistons for leakage with the engine at rest ; and if 

 under these conditions they prove to be tight, it is fair to as- 

 sume that the leakage under conditions of running is practically 

 nothing, and the part not accounted for by the diagram is 

 wholly or substantially cylinder condensation. If a similar 

 engine, working under similar conditions, is found by such tests 



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