Fuel Injection Strategies for Improving Performance and Reducing Emissions of a Low Compression Ratio Diesel Engine

The present work investigates the effects of lowering the compression ratio (LCR) from 18:1 to 14:1 and optimizing the fuel injection parameters across the operating range of a mass production light-duty diesel engine. The results were quantified for a regulatory Indian drive cycle using a one-dimensional simulation tool. The results show that the LCR approach can simultaneously reduce the oxides of nitrogen (NO_x) and soot emissions by 28% and 64%, respectively. However, the unburned hydrocarbon (HC) and carbon monoxide (CO) emissions increased significantly by 305% and 119%, respectively, with a 4.5% penalty in brake specific fuel consumption (BSFC). Hence, optimization of fuel injection parameters specific to LCR operation was attempted. It was evident that advancing the main injection timing and reducing the injection pressure at low-load operating points can significantly help to reduce BSFC, HC and CO emissions with a slight increase in the NO_x emissions. On the contrary, retarding the main injection timing and increasing the injection pressure at high-load operating points can further reduce the soot emissions without elevating the NO_x emissions. The results obtained with optimized injection timings quantified for the Indian drive cycle show that the soot emissions of the LCR engine are further reduced from 64% to 76%. Moreover, the HC and CO emissions penalty could be reduced significantly to 76% and 54%, respectively, and the fuel consumption penalty could be brought down to 1.6%. Thus, by adopting the proposed fuel injection strategy, the emissions and fuel consumption penalty of LCR engines can be reduced significantly.