两段喷射直喷式汽油机燃烧系统的混合气形成规律

针对一般直喷式汽油机燃烧系统设计复杂的问题,研究开发了一种以两段喷射作为分层稀燃混合气形成主要手段的汽油缸内直喷式燃烧系统。该文用三维模拟计算和试验的方法研究了两段喷射控制分层混合气形成的基本规律。研究结果表明:一次喷油时刻存在着最佳值,过早过晚都使喷雾碰壁,不利于混合气的形成和燃烧。二次喷油时刻也存在最佳值,在进气上止点后250°CA进行二次喷油,可使火花塞周围的混合气在点火时刻较适宜,有利于点火。两次喷射油量之比对混合气的形成有显著影响,当其控制在1/3左右时,缸内混合气的分层结构较为合理。

Nonuniform mixture formation by a two-stage gasoline direct injection combustion system

A two-stage, direct injection gasoline combustion system was developed to improve combustion system design. The two-stage injection with flexible injection timings provides a stratified mixture in the cylinder that provides more effecient combustion. The effects of the two-stage injection strategies on the mixture formation were then simulated numerically. The 3-D simulation results validated by the experiments show that there is an optimal first injection time for proper mixing, with early or late injection resulting in fuel impingement on the cylinder wall or the bottom of the piston bowl. A second injection at (250 CA) after the intake TDC provides a reasonably thick mixture near the spark plug that is easily ignited. The ratio of the two injection fuel quantities significantly influences the mixture formation. A ratio of 13 gives a reasonable mixture distribution in the cylinder.