点火定时对缸内直喷汽油机燃烧及颗粒物排放的影响

采用燃烧分析仪和DMS500型快速颗粒取样分析仪,在一台缸内直喷汽油机上进行了点火定时对燃烧过程和颗粒物排放影响的试验研究.结果表明:随着点火定时的不断延迟,火焰发展期逐渐缩短,快速燃烧期逐渐增大,缸内压力峰值逐渐下降,瞬时放热率峰值和缸内最高燃烧温度均逐渐降低且后移,放热过程迟缓,膨胀行程缸内温度逐渐升高.缸内直喷汽油机排气颗粒物排放呈包括核态和积聚态颗粒物的双峰分布；随点火定时的推迟,核态和积聚态颗粒物峰值数密度均逐渐降低,颗粒物总数量浓度逐渐降低,积聚态颗粒物峰值粒径逐渐减小,而核态颗粒物峰值粒径受点火定时的影响较小.

Effect of Spark Timing on Combustion and Particle Emission for Gasoline Direct Injection Engine

The effects of sparking timing on combustion process and particle emission were investigated experimentally on a gasoline direct injection engine by using combustion analyzer and DMS500 fast particulate spectrometer. Results showed that with the delay of spark timing, flame development duration decreased gradually, and rapid burning duration increased gradually. Peak value of heat release rate and cylinder mean temperature showed a gradually decrease and backward shift, which induced a slow heat release process and high cylinder temperature in expansion stroke. Also, spark timing delay led to decrease in the peak cylinder pressure. Moreover, exhaust particles from GDI engine exhibited a bimodal size distribution including nucleation mode and accumulation mode particles. As the reduce of spark advance, total particle number concentration and peak value of particle number density in nucleation mode and accumulation mode decreased gradually, and peak size of accumulation mode particles showed a decreasing trend, but spark timing exhibited a slight influence on peak size of nucleation mode particles.