Fuel temperature influence on spray and combustion characteristics in a constant volume combustion chamber (CVCC) under simulated engine operating conditions

• Cold diesel fuel exhibited deteriorated vaporization characteristics.
• Flame luminosity with cold diesel fuel was lower than warm diesel fuel.
• Cold diesel fuel showed lower in-chamber pressure and longer ignition delay.
• Ambient condition had more dominant effect than fuel temperature on combustion.

High amount of unburned hydrocarbon emission and combustion instability are serious problems in diesel engines during cold starting. In order to solve these troubles, the effects of fuel temperature on spray and combustion should be understood. In this study, macroscopic spray and combustion experiments were carried out over a wide range of fuel temperatures from 243 to 313 K. The tests were performed under simulated low temperature cold start condition. In-chamber pressure analysis and high speed imaging were combined in a constant-volume combustion chamber (CVCC). The diesel fuel was injected into the CVCC under simulated engine operating conditions with an injection pressure of 35 MPa. The cold diesel fuel showed a longer liquid penetration length and a narrower spray angle in macroscopic spray imaging. The reasons for the deteriorated spray characteristics were revealed to be the attenuation of the fuel evaporation and ambient air entrainment. In combustion imaging, partial misfires of the diesel spray were detected under cold start condition. On the other hand, all of spray plumes were successfully ignited under hot start condition. The peaks of in-chamber pressure and flame luminosity were decreased with cold fuel because of the poor air–fuel mixture preparation during the ignition delay period.