燃烧室形状对增压中冷柴油机燃烧和排放影响的数值模拟

摘要

Maintaining the constant compression ratio,five novel combustion chambers with different geometries were designed based on the combustion chamber of the prototype.Simulation on the influence of combustion chamber with six geometries on the combustion process of a diesel engine was made with STAR-CD.Results show that the impingement of spray on the wall with deep re-entrant combustion chamber results in the enhanced turbulence motion and improves the mixture formation rate.It is favorable to achieve quick combustion by increasing the pit depth of combustion chamber when the throat diameters are the same.The deepened bowl of combustion chamber leads to the increased maximum pressure and the decreased combustion duration.The combustion chamber with deep re-entrant bowl gives higher combustion rate and lower soot emission but higher NOx emissions.The combustion chamber with shallow-diskre-entrant gives an opposite behaviours.%在保持压缩比不变的条件下,基于原机燃烧室,新设计了5种不同形状的燃烧室,应用CFD数值模拟软件STAR-CD模拟研究了6种不同形状的燃烧室对柴油机燃烧过程的影响.结果表明,喷雾和深坑缩口型燃烧室壁面碰撞后能产生较强的湍流运动,提高混合气的形成速率.当燃烧室喉口直径相同时,增加燃烧室凹坑深度有利于实现快速燃烧.随着燃烧室凹坑加深,最高爆发压力升高,燃烧持续期缩短;深坑缩口型燃烧室燃烧速度快,Soot排放低,但NOx排放高,而浅盘缩口型燃烧室则相反.