EXPERIMENTAL STUDY ON LIQUID PHASE LPG SPRAY AND ICING PHENOMENON FOR A MIDDLE CLASS DIESEL ENGINE APPLICATION

Spray and icing visualization experiments were carried out to investigate spray characteristics and the icing phenomenon of a liquid phase LPG (liquefied petroleum gas) injection (LPLi) system that was intended for use in a modified, medium-duty diesel engine. The spray visualization experiments were conducted for different injection pressures and ambient pressures. Increasing injection pressure was found to benefit spray droplet atomization, enhancing vaporization of the fuel. As a result, the spray penetration length was shortened with increasing injection pressure at atmospheric ambient pressure. However, as the ambient pressure was increased, the penetration length increased with higher injection pressure. The long penetration might result in wall-wetting, causing harmful engine-out emissions such as total hydrocarbon (THC) and CO. It was also observed that ice formed on the nozzle tip and intake port due to the freezing of moisture around the components. This icing phenomenon is the direct cause of unstable engine combustion, resulting in engine emissions. Therefore in this research, the intake air and cylinder head temperatures were changed to investigate the effects of the temperature changes on the icing phenomenon. As a result, both the air and the head temperature increase could reduce the icing phenomenon and the air temperature was more effective.