Abstract:To improve spray impingement on wall and atomization in diesel engine combustion chamber, a double-layer diffluent combustion system with circular guiding collision boss was proposed for DI diesel engine. In this combustion system, the spray double-layer diffluence and secondary atomization were realized by matching the combustion chamber geometry with fuel spray to mix fuel and air sufficiently and utilize air in the clearance space effectively. Simulation results indicate that in the double-layer diffluent combustion system fuel density distribution becomes more homogeneous, leading to temperature distribution in the combustion chamber relative uniform during combustion process. Experimental results demonstrate that brake specific fuel consumption and soot emission decrease by 5.5% and 25.5% respectively while engine NO_x emissions increase about 12.4% for the type Ⅱ double-layer diffluent combustion system at three different fuel injection advance angles compared to conventional omega combustion system.