缸内直喷汽油机复合燃烧技术

A Compound Combustion Technology for Gasoline Direct Injection Engine

针对缸内直喷汽油机(GDI)存在的主要排放未燃HC和NOx问题,提出了燃烧理论空燃比的复合喷射燃烧技术,运用了废气再循环(EGR)分层技术.复合喷射通过稳压腔辅助喷射燃油和缸内直接喷射燃油,使缸内形成准均质混合气,以满足各种工况下GDI对混合气的要求.在负荷由小到大直至满负荷的范围内都可避免出现过稀区、过浓区,这利于燃烧并减少HC排放;利用在进气管上设计的独特的废气通道,通过滚流分层充气方法,将进气冲程再循环的废气和油气分层,以形成废气-油气-废气馅饼状分层,从而提高了废气再循环率,降低了NOx排放.两种技术的结合,可以解决GDI发动机存在的主要排放问题.实验证明:复合燃烧系统与EGR分层充气技术的有效结合,可以在各种工况下降低NOx排放,降低量为61%;可以降低冷启动时的HC排放,降低量至少为50%.

A combustion technology with stoichiometric air-fuel ratio using compound injection and exhaust gas recirculation （EGR） stratification was proposed to solve the problem of unburned HC and NOx emission in gasoline direct injection（GDI）engines. The quasi-homogenous charge can be formed by compound injection technique,i.e.,plenum injection and cylinder direct injection,to reduce the HC emission. Adopting the unique design of the exhaust passage in the intake manifold,the recirculated exhaust gas and fuel can be stratified in the intake stroke to achieve the higher EGR rate,leading to the lower NOx emission. The experimental results show that the NOx emission under all operating conditions and the HC emission during cold-start could decrease by up to 61% and 50%,respectively,with the combination of the compound combustion system and the EGR technology.