汽油机瞬变工况各缸差异性的试验研究

An Experimental Study on the Differences Between Cylinders in a Gasoline Engine Under Transient Conditions

采用动态压力实测与数值模拟相结合的方法,对一台车用汽油机各缸参数瞬变值进行连续检测,得到各缸参数的变化范围、变化规律和各缸差异程度。通过对比分析得出各缸差异性的影响因素及其对汽油机瞬变状态下热功转换过程的影响。结果表明:在瞬变工况下,各缸充气效率相对偏差在±5%以内,在中低转速时主要受进气平均压力影响,高转速时主要受压力波和缸内残余废气量影响;各缸RGF和充气效率的差异性呈现对称关系;在中低转速时,各缸PMEP差异性主要受进气平均压力影响,而在高转速时则主要受RGF影响;IMEP相对偏差是充气效率和RGF等参数综合影响的结果,最大值达到±30%以上。以上规律为缩小多缸汽油机瞬变工况下各缸差异性提供了依据。

The transient values of parameters in each cylinder of a vehicle gasoline engine are continuously measured by adopting a method of combining dynamic pressure masurement with numerical simulation, so the varying range,the law of variation of parameters in each cyliner and the degrees of their differences between cylinders are obtained. Through comparative analyses,the affecting factors of differences between cylinders and their effects on the conversion process from thermal energy to work under the transient states of gasoline engine are obtained. The results show that under transient conditions, the relative deviation of volumetric efficiency betweeen cylinders is within ±5%,and it is mainly affected by average intake pressure at low and medium speeds,while it is influenced by pressure wave and in-cylinder residual gas fraction （RGF） at high speeds. There appears a symmetry relation-ship between the differences in RGF and the differences in volumetric efficiency. The relative deviation of PMEP betweeen cylinders is mainly affected by average intake pressure at low and medium speeds,and is influenced by RGF at high speeds. The ralative deviation in IMEP reaches over ±30% at most and is the result of concurrent effects of volumetric efficiency and RGF etc. The law mentioned above provides a basis for reducing the discrepancy between cylinders of gasolie engine under transient conditions.