Spray and combustion processes under simulated cold start condition in a constant volume combustion chamber

Abstract

Cold start for diesel engine is an important issue due to high amount of unburned hydrocarbon and combustion instability. In order to mitigate the problem, fundamental understanding about effects of engine operating condition on spray and combustion characteristics is essential. In this work, macroscopic spray and combustion experiments were performed under simulated low temperature cold start condition in a constant volume combustion chamber (CVCC). The results of spray and combustion experiments were compared with those of warmed up start condition. In-chamber pressure analysis was combined with high speed imaging. The diesel fuel was injected into the CVCC at a simulated engine operating conditions with injection pressure of 35 MPa. Macroscopic spray visualization results showed longer liquid tip penetration length and wider spray angle under cold start condition. In terms of combustion visualization, partial misfires of diesel spray were observed under cold start condition, whereas all spray plumes were ignited under warmed up condition. Lengthened ignition delay with lower peak of in-chamber pressure and flame luminosity were observed under cold start condition.