Effect of fuel injection timing and pressure on combustion, emissions and performance characteristics of a single cylinder diesel engine

For a diesel engine, fuel injection pressure (FIP) and injection timings are very important parameters, which influence the engine performance, emissions, and combustion. Other injection parameters affecting engine performance are rate of injection, injection pattern, number of injections etc. A single cylinder research engine was used to experimentally determine the effects of fuel injection strategies and injection timings on engine combustion, performance and emission characteristics. The experiments were conducted at constant speed (2500 rpm) with two FIPs (500 and 1000 bars respectively) and different start of injection (SOI) timings. Cylinder pressure and rate of heat release (ROHR) were found to be higher for lower FIPs however advanced injection timings gave higher ROHR in early combustion stages. Brake thermal efficiency (BTE) increased with increased injection pressures while exhaust gas temperature and brake mean effective pressure (BMEP) increased upto 500 bars. These parameters reduced slightly with increase in FIP. For advanced SOI, BMEP and BTE increased, while brake specific fuel consumption (BSFC) and exhaust gas temperature reduced significantly. Carbon dioxide (CO2) and hydrocarbon (HC) emissions decreased however nitrogen oxide (NOx) emissions increased with increasing FIP. Lower CO2 and HC emissions, and significantly higher NOx emissions were observed with advanced injection timings. Particulate number-size distribution increased with increasing engine load however it reduced with increasing FIP.