Abstract
The use of green or alternative fuels is currently on the rise. Such fuels can now be utilized in many passenger car and in many commercial vehicles. Liquefied petroleum gas (LPG) has been employed as a alternative fuel for vehicles due to its low cost and reduced emissions. While vaporizer-type LPG engines were prevalent in the past, injection systems that directly inject liquid-phase fuel into the intake port are currently being researched so as to improve engine performance, charging efficiency, and cold start capability. Because the spray characteristics of liquid-phase LPG are different from those of conventional liquid fuels, it is necessary to understand the spray characteristics and evaporating processes of LPG so that more efficient and lower emission LPG engines may be developed. It is known that diesel engines are the main cause of smoke pollution in urban areas. Recently, several LPG engines for heavy-duty vehicles have been developed which have the capacity to replace some diesel engines. In this article, the diesel engines of the heavy duty vehicles apply to the LPLi system, and then the spray characteristics be known.. Measurements of the LPG injection quantities for four different injection pressures were performed in an atmospheric pressure environment. In addition, experiments were carried out regarding the spray characteristics at other injection pressures and surrounding pressures when the same fuel quantity was injected. Image processing techniques were used to confirm and analyze the spray characteristics. The images of the sprays show that the LPG spray penetration length increased at higher injection pressures. However, the LPG spray penetration length decreased as the surrounding pressure was increased. It was also observed that decreases in the LPG spray penetration length did not have a largely effect on the surrounding pressure when the injection pressure was 20 bar.
Key words : LPG (Liquefied petroleum gas), LPLi (Liquid-phase LPG injection), Intake port, Penetration