“双壁面射流”燃烧系统性能的试验研究

Experimental study on performance of double-wall jet combustion system

为了改善直喷柴油机的排放与经济性能,该文开发了一种直喷柴油机"双壁面射流"燃烧系统。通过试验的方法研究了燃烧室结构参数、喷油器结构参数、转速、负荷及喷油时刻等运行条件对"双壁面射流"燃烧系统燃烧过程的影响。试验结果表明:随转速的增加,着火始点向后推迟,缸压峰值呈现出先增大后减小的趋势,瞬时放热率峰值、缸内燃烧平均温度和累计放热量都降低;随负荷的增加,着火点提前,缸压峰值对应的曲轴转角向后推迟,缸压峰值、缸内燃烧平均温度和累计放热量都增加,总指示热效率随负荷的增加而降低。不同燃烧室结构参数和喷油器参数的"双壁面射流"燃烧系统燃烧持续期,在2100r/min的负荷特性中,小负荷主要受压缩比的影响,大负荷主要受预混合燃烧量的影响;总指示热效率主要受压缩比和壁面油膜生成量的影响;而NOx与碳烟排放受预混合燃烧量和贯穿度的影响。将"双壁面射流"燃烧系统静态供油提前角提前到18°CA BTDC,能实现扭矩点与功率点同为0.21BSU的低碳烟排放。

A new ＂double wall jet＂ combustion system was designed for improving the emissions and fuel economy performance of DI diesel engine. Effects of such operating condition as structure parameters of combustion chamber and injector, speed, load and injection timing on the combustion process of ＂double wall jet＂ were investigated by experimental method. The results showed： with the increasing of engine speed, the SOC was lagged off, the peak of combustion pressure showed a trendy of increasing firstly and reducing subsequently; the transient ROHR, meaning temperature of combustion and accumulated heat release, were reduced. With the increasing of load, the SOC was advanced; the angle of peak pressure was lagged off; the peak pressure, mean temperature of combustion and accumulated heat release were increased, while the indicated thermal efficiency was reduced. At engine speed of 2100 r/min, the combustion duration of double-wall-jet combustion system was mainly affected by compression ratio at lower load, but mainly affected by the amount of pre-mixed combustion at higher load. The indicated thermal efficiency was mainly affected by compression ratio and fuel film of the wall of combustion chamber. Emission of NOx and smoke were affected by the amount of pre-mixed combustion and injection through. The static fuel supply timing was increased to 18°CA BTDC, which leads to 0.21 BSU smoke emission at the operating point of rate power and maximum torque.