Compression rate influence on the internal combustion engine efficiency

Nowadays, engines with the adjustable compression ratio are not used, which apparently could be explained by their design complexity. However, the known twin-shaft machines could be introduced without significant complications. Thus, a decrease in the engine efficiency at the increased crankshaft speed could be compensated by the compression ratio. The paper presents results of calculating efficiency and fuel consumption at the compression ratio of 8.6 and crankshaft speed of 2000 and 4000 min–1, as well as at the compression ratio of 13 and rotation speed of 4000 min–1 for the combustion character indicators equal to 3 and 1. It shows the indicated characteristics approximation at the higher rotation frequency to those at the lower rotation frequency with the increased compression. The engine parameters for various modes based on the Wiebe theory previously calculated made it possible to determine efficiency and fuel consumption for the corresponding engine operating modes.