蒸发性对燃油瞬态喷雾撞击壁面的动态传热影响

Effect of Fuel Volatility on Heat Transfer of Spray Impingement on Piston Surface

直喷发动机燃油喷雾撞击壁面形成油膜,导致燃烧效率降低,颗粒物排放增加。伴随撞壁的动态传热过程对油膜蒸发具有重要影响。本文针对正戊烷、甲醇、甲醇汽油混合燃料瞬态喷雾撞击壁面,研究了不同条件下蒸发性对燃油瞬态喷雾撞击壁面动态传热影响。结果表明,提高喷油温度可促进燃油雾化,增大喷油压力或降低喷油距离可提高液滴撞壁强度,缩短液膜存在时间。撞壁瞬态温度与热流密度动态变化特征受燃油蒸发性与喷雾条件联合影响。

Fuel spray impingement on piston surfaces causes liquid film formation for Gasoline direct injection(GDI)engine,resulting in a reduction in combustion efficiency and increase in particulate emissions.Dynamic heat transfer has an impact on liquid film evaporation during fuel impingement.In this paper,the effect of fuel volatility on spray impingement heat transfer with n-pentane.methanol and methanol-gasoline mixture was examined.Results showed that increasing the fuel injection temperature helped to improve atomization of the fuel spray.An increase in injection pressure and a decrease in impact distance both increased impact strength,which led to a shorter liquid film lifetime on the surface.The dynamic characteristics of transient piston temperature and heat flux were jointly affected by fuel volatility and other spray conditions.