EGR与进气富氧对直喷柴油机NO和碳烟排放的影响

使用增压中冷直喷柴油机,采用进气富氧与高比率EGR相结合的技术,实现富氧燃烧条件下的低NO-碳烟排放.单独使用富氧燃烧,NO的排放将随氧体积分数的上升而增加.单独使用高EGR,碳烟(Smoke)的排放会随EGR率的增加而增加.将富氧进气与高比率EGR的结合,可以通过富氧的强氧化性降低Smoke排放,通过大比率EGR来控制燃烧温度,抑制NO的过度增长.试验结果表明:1,600,r/min(经济转速)下,EGR率为35%～45%,进气氧体积分数为21%～23%;2,200,r/min(最高转矩)下,EGR率为20%～50%,进气氧体积分数为22%～24%;在上述范围内的EGR与O2搭配,可以实现低于原机的NO-Smoke排放.综合考察发动机在各种掺比下的功率、油耗,探索出适合发动机各个工况的富氧及EGR组合区域,在该区域内发动机的功率、油耗和排放水平都能得到兼顾.

Influence of EGR and Oxygen-Enriched Air on DI Engine NO-Smoke Emission

Low NO-Smoke emission with oxygen-enriched combustion is achieved with a commercial turbocharged inter-cooled direct injection diesel engine using oxygen-enriched intake air and high rate EGR.An operating regime was identified in which NO increased dramatically when increasing oxygen concentration without optimization.Smoke increases with the increase of EGR rate.Using the blended oxygen-enriched air and high rate EGR gas,soot was reduced and NO was inhibited.Experimental results reveal that,the engine can get lower NO-Smoke emission than that of original engine with following EGR and oxygen enrichment combination.They are,engine speed of 1,600,r/min in with EGR rates of 35% to 45% and O2 concentration of 21%-23%.The maximum torque speed of 2 200,r/min in with EGR rates of 20% to 50% and O2 concentration of 22%-24%.The experiment suggests the best region of EGR and oxygen concentration where engine power,fuel consumption and emissions can be balanced.