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THE combustion chamber of a Diesel engine is, in substance, a chemical retort where the ad- dition of heat changes injected fuel from a liquid into a gas. Thermo-dynamically, the faster fuel burns the more efficient is the combustion, and to procure rapid combustion the fuel charge must be intimately mixed with the air compressed in the cylinder. This mixing process is termed turbulence. vided, as in high compression type engines, fuel must be directly injected into a cylinder in a man- ner to burn extremely rapidly. Hence, very high fuel injection pressures are necessary to secure |
adequate atomization. To effect this, clean, high grade fuel is injected at high pressure through small orifices over a short injection period. During the combustion period, these factors are directly responsible for a high combustion pres- sure rise per degree of crank travel, with maxi- mum high combustion pressure. The latter is necessary to obtain a given power output of the cylinder, the index of which is mean effective pressure. An indicator diagram of this perform- ance would show an abrupt pressure rise at the end of the compression stroke and a rapid falling off of pressure on the expansion or power stroke. A combustion system with these characteristics will show a relatively lower mean effective pres- |
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DE LA VERGNE 8-cylinder, 1,000-hp Model VO Diesel engine used in Baldwin Diesel-electric switching locomotives. |