Studies on Low Compression Ratio Diesel Engine : 3rd Report, Relation between Combustibility and Performances

抄録

In a diesel engine, by a systematic controlling of the burning rate, the performances i.e., thermal efficiency, maximum pressure, maximum rate of pressure rise, combustion noise emission and maximum combustion temperature which affects the density of NOx emission, etc. may be controlled. In this paper, the performance values, for example the indicated thermal efficiency, were calculated stepwise based on Wiebe's combustion function, and the relationships between the combustion rate and each performance value were investigated. In addition, the harmonics of engine noise were considered to be related to that of the cylinder pressure variation, hence the harmonics of cylinder puressure variation were calculated for the estimation of noise emission. As a result of the calculations, it was clarified that when the combustion rate was controlled to a desired free value with a low compression ratio, the performances, i.e. indicated thermal efficiency, maximum pressure, combustion noise etc., could be improve simultaneously. Thus, a theoretical guide to improving the performances of a low compression ratio diesel engine was obtained.