怠速工况发动机富氧燃烧排放及其稳定性研究

Emission and Combustion Stability Under Engine Idling Condition with Oxygen-Enriched Intake Charge

利用氧的体积分数为21％～27％的富氧空气进气，研究点燃式发动机启动后最初怠速工况排放特性和规律。试验表明，在氧的体积分数为23％～25％的低富氧程度下，CO、HC排放降低作用更加显著，同时NOx排放升高程度处于较低水平。相反，在高富氧浓度下，CO、HC排放降低程度明显减小，NOx排放大幅提高。因此，低富氧浓度在改善发动机怠速工况燃烧排放中具有重要作用和应用潜力。研究还表明，随着供气氧的体积分数的增加，压力峰值提高，相位提前，发动机循环变动减小。进气氧的体积分数对瞬时转速循环变动性影响是有限度的，23％左右的低富氧作用最为明显，随着富氧程度增加，作用逐渐减小。

Combustion and emission characteristics under engine idling condition with oxygen-enriched intake charge （oxygen concentration 21%-27% ） were investigated. The oxygen-enriched charge improves the combustion and stability and reduces CO and HC emissions remarkably with a penalty of high NOx emission. In fact, low oxygen enrichment slightly increases NOx emission but greatly decrease in CO and HC emissions. Therefore, low oxygen enrichment （23%-25%） under idling condition presents a potential benefits in engine combustion. It is important to balance a comprehensive profit of HC, CO and NOx emissions with oxygen enrichment. The results show that, with the increment of oxygen enrichment, the peak pressure is increased, the angle of peak pressure is advanced, and the cyclic variation is decreased. The influence of oxygen enrichment on the variation of engine speed shows larger at low oxygen enrichment but weaker at large oxygen enrichment.