Comparison of different low temperature combustion strategies in a light duty air cooled diesel engine

Low temperature combustion (LTC) strategies produce near zero oxides of nitrogen (NO,,) and particulate matter (PM) emissions, however, they result in a narrow operating load range. The present work compares three different LTC strategies, viz. Homogenous Charge Compression Ignition (HCCI), Premixed Charge Compression Ignition (PCCI), Reactivity Controlled Compression Ignition (RCCI) in a production, light duty diesel engine to come up with a suitable strategy to achieve lower emissions and wider operating range. The engine intake, exhaust and fuel injection systems are modified to implement LTC strategies. Using a suitable controller, the engine operating parameters in terms of direct injected diesel timings, injection pressures, port injected gasoline timings, gasoline to diesel ratio, intake air temperatures, fuel vaporizer temperature and concentration of exhaust gas recirculation depending upon the LTC strategy are optimized to achieve maximum brake thermal efficiency. Before modifications, the engine is operated 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 in the entire load range with 16.3% higher brake thermal efficiency, near zero NOx and smoke emissions, however, HCCI and PCCI could reach only upto 40% and 60% of rated load, respectively.