侧卷流和复合卷流燃烧系统混合燃烧特性

Fuel-Air Mixing and Combustion Characteristics of Lateral Swirl Combustion System and Multi-Swirl Combustion System

为研究侧卷流燃烧系统(LSCS)和复合卷流燃烧系统(MSCS)对直喷式柴油机性能的影响,通过单缸柴油机台架开展了LSCS和MSCS的燃烧性能试验,结合仿真分析,揭示了LSCS和MSCS的缸内油、气混合特性.结果表明:在小负荷和高过量空气系数φ_(a)下,MSCS体现出较好的燃烧性能,相比于LSCS,其燃油消耗率最大降幅为3.6 g/(kW·h),碳烟排放最大降幅为0.13 g/(kW·h),燃烧持续期最大降幅为2.6°CA;但在大负荷和低φ_(a)下,LSCS体现出更好的燃烧性能,相比于MSCS,其燃油消耗率最大降幅为2.6 g/(kW·h),碳烟排放最大降幅为0.56 g/(kW·h),燃烧持续期最大降幅为2.8°CA.仿真结果表明:随负荷减小或φ_(a)增大,燃油射流贯穿能力减弱,复合卷流燃烧室的弧脊能更有效地提升油、气混合质量;随负荷增大或φ_(a)减小,燃油射流贯穿能力增强,复合卷流燃烧室的弧脊阻碍了燃油射流扩散,侧卷流燃烧室的分流造型能更显著地改善油、气混合过程.

Combustion performance experiments were carried out on a single-cylinder diesel engine to study the influences of a lateral swirl combustion system(LSCS)and a multi-swirl combustion system(MSCS)on engine performance.Combined with simulation analysis,the fuel-air mixing and combustion characteristics were revealed for the LSCS and the MSCS respectively.Experimental results show that under low loads and high excess air coefficients,the MSCS obtains better combustion performance than the LSCS with the maximum reduction in fuel consumption of 3.6 g/(kW·h),in soot emission of 0.13 g/(kW·h)and in combustion duration of 2.6°CA.However,under heavy loads and low excess air coefficients,the LSCS shows better combustion performance than the MSCS with the maximum reduction in fuel consumption of 2.6 g/(kW·h),in soot emission of 0.56 g/(kW·h)and in combustion duration of 2.8°CA.Simulation results indicate that,when the engine load decreases or the excess air coefficient increases,the fuel spray penetration ability becomes weakened,and the circular ridge of the MSCS chamber improves fuel-air mixing quality more effectively.However,when the engine load increases or the excess air coefficient decreases,the fuel spray penetration ability is enhanced.The split-flow creation of the LSCS chamber improves the fuel-air mixing quality more evidently,while the circular ridge of the MSCS chamber hinders the diffusion of fuel spray.