EFFECT OF COMPRESSION RATIO ON DI DIESEL ENGINE PERFORMANCE AND COMBUSTION PARAMETERS AT DIFFERENT OPERATING CONDITIONS

This paper reports on the effect of compression ratio (CR) on the performance and emissions characteristics and the main combustion parameters at different operating conditions. The experiments were conducted on a single cylinder four stroke variable compression ratio direct injection diesel engine. Tests were carried out at compression ratios of 14:1, 16:1, and 18:1. From the test results, it was found that although there was a small carbon monoxide (CO) and unburned hydrocarbon (HC) penalty, the compression ratio has a potential to improve brake thermal efficiency (BTE) and the brake specific fuel consumption (BSFC). Reducing the compression ratio greatly reduced nitrogen oxides (NOx), smoke emissions and exhaust gases temperature. The results revealed that, with increasing compression ratio, Peak-in-cylinder pressure increases while, both peak value and duration of the premixed mode of burning diminish; furthermore, the end of combustion becomes more retard. This work develops a model that relates the fuel burning rate (FBR), with compression ratio, engine speed and load (BMEP).The FBR prediction agree with the experimental results, and Comparisons revealed that the relative deviations not exceed 2%.