缸内直喷汽油车细小颗粒物排放特性研究

Emission characteristics of fine particles from direct-injection gasoline vehicles

选取三辆满足国六排放标准的缸内直喷汽油车进行常温冷启动WLTC循环排放试验,研究不同车辆排放的粒径在23nm以上的固态颗粒物、6nm以上包含挥发性/半挥发性组分的颗粒物数量排放特性,并进行了比较研究.结果发现,在缸内直喷汽油车排放的6~30nm范围内包含挥发性/半挥发性物质的细颗粒物主要产生在WLTC循环减速段､高速段和超高速段;30~2500nm范围的挥发性/半挥发性的颗粒物主要在超高速段生成;其它工况下,23nm以上固态颗粒物在颗粒物数量排放中占主体.试验研究还发现GPF对6~30nm大小的细颗粒物捕集效果不佳,并且GPF再生时会产生高浓度6~30nm大小的细颗粒物排放.颗粒物碳质成分分析表明挥发性/半挥发性细颗粒物对法规测量的23~2500nm颗粒物的数量排放影响甚微,但对颗粒物质量排放影响明显.

Three direct-injection gasoline vehicles meeting China-6 emission standard were selected for cold start WLTC tests.The emission characteristics of solid particles above 23nm and particles containing volatile/semi-volatile components above 6nm were measured on the three vehicles.The test results showed that particles containing volatile/semi-volatile components in the particle size range of 6~30nm were mainly produced in the WLTC cycle deceleration condition,high-speed section,and ultra-high-speed section.Volatile/semi-volatile particles in the particle size range of 30~2500nm were mainly produced in the ultra-high-speed section.Solid particles above 23nm accounted for the bulk of the emissions in the rest conditions.GPF had limited effectiveness in intercepting particles in the 6~30nm particle size range.Moreover,GPF regeneration produced high concentrations of particles in the range of 6~30nm.Analysis of the carbonaceous composition of particles showed that volatile/semi-volatile particles had little effect on PN emissions of solid particles above 23nm measured by the emission regulation but had a significant impact on PM emissions.