88 THE THERMODYNAMICS OF THE MARINE OIL ENGINE. 



"It should be mentioned that all auxiliaries are steam driven, one oil-fired boiler being 

 fitted on deck for port use and a smaller one in the engine-room for use at sea. Firing is 

 accomplished partly by oil and partly by the exhaust gases from the engines. The boiler is 

 of the ordinary marine type, having two furnaces, so that the gases are continually passing 

 through one furnace, to act, in the first place, as a silencer, and in the second to utilize the 

 waste heat from the exhaust. The second furnace is free for an oil burner, but we find it 

 unnecessary, as, with the steering and other small engines usually working at sea, sufificient 

 steam to drive them is generated by the exhaust gases alone, which is a great saving." 



This has a bearing on the practical value of the economizing boiler. 



Second, Mr. W. R. Haynie, in speaking of the low-pressure engine, said, "which gives 

 the same effective or service results at a sacrifice of economy which varies from 8 to 12 

 per cent." 



In the plates accompanying this paper there is shown a figure illustrating the loss in the 

 slow injection of the fuel (see Plate 24). If you consider that the thermal efficiency of 

 the normal high-pressure Diesel engine is no better than could be obtained with compression 

 pressure of 275 pounds, as shown by this figure and brought out at the bottom of page 80, 

 then the error of the statement made by Mr. Haynie that the low-pressure engine has a lower 

 efficiency will at once be apparent. Mr. Haynie speaks as if low-pressure engines were on 

 the market. The hot-head engine is in a way a low-pressure type. That should not be con- 

 fused with the low-pressure type proposed. The hot-head type is limited to small sizes. As 

 brought out in the paper any Diesel can run on low compression provided that it can first be 

 warmed. This is, however, an impossibility for a Diesel engine. While Mr. Haynie did 

 not bring up the reduced power in the low-compression type that is a more common fallacy 

 than the low-efficiency idea. 



Third, Mr. Haynie asked : "Is it not a fact that the injection air is used largely for two 

 purposes? In the true Diesel or original Diesel, it was used for force to blow the air into 

 the engine?" My answer was, "Yes." It should have been "No" and "Yes." Injection air 

 in all cases is used only to force the oil into the engine. This is taken up at the top of page 

 82 of the paper. 



In his last remarks Mr. Haynie said: "By the lower compression we obviated the high' 

 temperatures created by that compression, and by the breaking up of the oil with a mixture 

 of air you can get complete combustion at a lower compression pressure which follows the 

 curve of temperature of course." 



This seems to infer that in an engine it is possible to reduce the pressure of compres- 

 sion, and hence the temperature of compression and make-up for this reduction by a change 

 in the condition of the fuel injected. The writer's experiments do not bear this out. He has 

 found there is but little difference in the compression, and hence the temperature needed to 

 ignite all fuels. Experiments with different fuels seem to indicate that the fuel must be 

 broken up into a spray in order for the temperature of the compressed air to act at all. Then, 

 if the fuel is properly sprayed, the temperature of compression must be around 1,000° F. 

 We found it to be impossible to start our experimental engine on those nights when the shop 

 and engine were both cold — close to 32° F. We got no results, regardless of the fuel which 

 we used. The same engine adjusted in the same way would start on heavy oil if the shop 

 and engine were around 60° F. It appears that while the pressure of compression can be 

 lowered in the oil engine the temperature of compression must not be lowered. 



