Diesel Injection Strategy in a Premixed Charge Compression Ignition Engine Under a Low Load

Abstract

A diesel injection strategy in a premixed charge compression ignition(PCCI) engine was investigated under low load conditions. The main injection timing of the PCCI combustion was selected based on the simultaneous reduction of nitrogen oxides(NOX) and unburned hydrocarbon(UHC) emissions at an exhaust gas recirculation(EGR) rate of 30 %. Despite the main injection timing chosen, too advanced combustion phasing resulted in increased fuel consumption. Therefore, combustion phasing was effectively retarded by an additional EGR. Double injection strategy was implemented to reduce in-cylinder wall wetting. The UHC and carbon monoxide(CO) emissions were significantly reduced by optimizing pilot injection timing and quantity. In conclusion, the UHC and CO emissions were reduced effectively in the PCCI combustion using the double injection strategy and appropriate EGR rate, which resulted in increased combustion efficiency and improved fuel economy.