Studies on the Low Compression Ratio Diesel Engine : 1st Report, The Problems Arising from Low Compression Ratio

Abstract

Up to this time, the higher compression rations have been widely used in high speed diesel engines, but a lower compression ratio is demanded to achieve an increase in output with special regard to the stress of structure, engine noise etc. In this paper, some problems arising from the reduction of compression ratio in diesel engine were first described, and the basic data required to derive a low compression ratio in diesel engine were first described, and the periments, it was shown that the most important problems with low compression ratio are the reduction of maximum output and the increase of specific fuel consumption and this depends rather on the increase of cooling loss than on the reduction of theoretical thermal efficiency considering the rate of heat release in cycle. In the engine noise, the lower frequency part of sound pressure was reduced while, on the other hand the higher frequency part increased at a lower compression ratio. Consequently the sound pressure level of the overall range increased. In addition, the higher frequency part seems to be affected by the maximum rate of pressure rise regardless of compression ratio.