火花塞微孔喷氢对发动机燃烧及排放的影响

Effect of hydrogen injection through spark plug microporous on engine combustion and emissions

在缸内直喷汽油机上加装氢气喷射系统,设计氢气射流引导结构,在火花塞上增加氢气喷射孔,使氢气富集到火花塞附近引燃混合气,实现稀薄混合气的快速燃烧,研究固定转速(1600 r/min)下,掺氢比φ_(h)分别为0、2.5%、3.0%、3.5%、4.0%、4.5%、5.0%和过量空气系数λ分别为1.0、1.1、1.2、1.3、1.4、1.5对汽油机稀燃特性与排放特性的影响。结果表明:稀燃模式下,掺氢能使缸压峰值升高,峰值相位提前;掺入少量氢气可以抵消稀燃导致的燃烧恶化的影响,使得不同热释放的燃烧持续时间明显缩短;φ_(h)为3.5%时,发动机循环变异系数降低到5%以下;不同λ时,排放中CO、HC的体积分数随φ_(h)增大而降低,但NO_(x)的体积分数随φ_(h)增大而升高;与纯汽油模式相比,稀燃模式下掺氢,排放中CO的体积分数降幅小于0.1%,使NO_(x)的体积分数明显降低。

A hydrogen jet guiding structure is designed and installed on a direct injection gasoline engine,a hydrogen injector with micro nozzle is added on the spark plug to enrich hydrogen near the spark plug and ignite the mixture,so as to accelerate the combustion of the lean mixture.The effects of hydrogen mixing ratioφ_(h) is 0,2.5%,3.0%,3.5%,4.0%,4.5%,5.0%and excess air coefficientsλis 1.0,1.1,1.2,1.3,1.4,1.5 at a fixed speed(1600 r/min)on lean mixture combustion characteristics and emission characteristics of gasoline engine are studied.The results show that in lean mixture combustion mode,hydrogen can increase the peak cylinder pressure and advance the peak phase;adding a small amount of hydrogen can shorten the combustion duration for different heat release.Whenφ_(h) is 3.5%,the coefficient of variation of engine cycle decreases to below 5%.The volume fraction of CO and HC is decreased with the increase ofφ_(h),the volume fraction of NO_(x) is increased with the increase ofφ_(h).Compared with the pure gasoline mode,in lean mixture combustion mode the volume fraction of CO is decreased by less than 0.1%,and the volume fraction of NO_(x) is decreased significantly.