基于两级高能点火和被动预燃室的高压缩比汽油机燃烧及排放特性研究

Study on Combustion and Emission Characteristics of High Compression Ratio Gasoline Engine Based on Two-stage High Energy Ignition and Passive Pre-chamber

基于一台自然吸气缸内直喷汽油机,研究了高能点火、被动预燃室和两者结合对当量比和稀薄燃烧工况下燃烧与排放特性的影响。结果表明,高能点火结合被动预燃室,能够在小负荷工况下显著降低循环波动、缩短点火延迟期和燃烧持续期,两者效果相互叠加,能够进一步提高热效率。高能点火的被动预燃室可将稀燃极限由1.4小幅拓宽至1.5~1.6之间;在当量比工况,可使热效率相对提升最高达17.9%。而在大负荷工况下,高能点火结合普通火花塞或被动预燃室均对燃烧性能无明显提升作用。对于排放性能而言,高能点火对于排放性能的影响较小,而被动预燃室对排放影响更为显著;小负荷工况下,被动预燃室倾向于降低NOx排放;中大负荷工况下,被动预燃室倾向于增加NOx排放;两种负荷下,受到火焰淬熄和燃油撞壁作用的影响,被动预燃室的HC排放相比普通火花塞均略有升高。

Based on a naturally aspirated in-cylinder direct-injection gasoline engine,the influence of high energy ignition,passive pre-chamber,and the combination of the two on the engine.s combustion and emission characteristics under stoichiometric and lean burn conditions is studied.The results show that high energy ignition combined with passive pre-chamber can significantly reduce cyclic variation,shorten ignition delay and combustion duration,and improve thermal efficiency under low load conditions.The passive pre-chamber with high-energy ignition can slightly expand the lean burn limit from 1.4 to between 1.5 and 1.6;under stoichiometric conditions,the relative increase of thermal efficiency can reach up to 17.9%.Under heavy load conditions,high-energy ignition combined with ordinary spark plugs or passive pre-combustion chambers will not significantly improve the combustion performance.In terms of emission,high-energy ignition has less impact on emission performance,while passive pre-chamber has a more significant impact on emission.Under low load conditions,passive pre-chamber tends to reduce NOx emission;under medium and heavy load conditions,passive pre-combustion chamber tends to increase NOx emission.Under various loads,the HC emission of the passive pre-combustion chamber is slightly higher than that of ordinary spark plugs due to flame quenching and fuel hitting the pre-chamber wall.