Experimental optimization of reactivity controlled compression ignition combustion in a light duty diesel engine

Reactivity Controlled Compression Ignition (RCCI) is emerging as a most promising combustion strategy to achieve near zero oxides of nitrogen (NOx) and smoke emissions along with higher brake thermal efficiency. The present work attempts to implement RCCI strategy in a production, light duty diesel engine by replacing an existing mechanical fuel injection with a flexible common rail direct injection diesel system and a low pressure gasoline port fuel injection system. Further, the engine compression ratio is reduced through modifications in piston bowl. Using a suitable controller, the engine operating parameters in terms of direct injected diesel timings, injection pressure, port injected gasoline quantity and gasoline to diesel ratio at each load conditions are optimized to achieve maximum brake thermal efficiency. Before modifications, the engine is run under conventional combustion mode at rated speed, varying loads to establish baseline reference data. The obtained results show that the engine could be operated in RCCI mode over its entire load range with a maximum increase of 14.2% brake thermal efficiency, near zero NOx and smoke emissions compared to conventional combustion. Further, reducing compression ratio is found to increase brake thermal efficiency by 7.6% and reduce carbon monoxide by 16.8% in RCCI.