冷起动时甲醇掺烧液化气发动机的甲醛和未燃甲醇排放

Emissions of Formaldehyde and Unburned Methanol from a Methanol Engine with Liquefied Petroleum Gas as Ignition Improver During Cold Start

基于单循环燃料喷射控制策略及冷起动,在一台125mL单缸电控喷射点燃式发动机上,试验研究了LPG(液化石油气)与甲醇循环喷射量的质量比和LPG迟后甲醇喷射时刻对甲醇掺烧LPG发动机甲醛和未燃甲醇排放的影响.甲醇掺烧LPG发动机中LPG仅起辅助起动作用.试验结果表明:增大LPG与甲醇循环喷射量质量比可使甲醇掺烧LPG发动机着火性能改善,未燃甲醇排放减少,甲醛排放增多;合理控制LPG迟后甲醇喷射时刻可显著改善着火性能,减少未燃甲醇排放,而甲醛排放稍有增加;LPG迟后甲醇在曲轴转角为276°时(上止点前)喷射,缸内最大压力达4.46MPa,未燃甲醇的体积分数减小到1173×10-6.甲醇掺烧LPG发动机时起动工况的甲醛和未燃甲醇排放量随LPG与甲醇循环喷射量的质量比和LPG迟后甲醇喷射时刻的变化呈相反的变化趋势.

The effects of the mass ratio of injected liquefied petroleum gas（LPG）to methanol and the LPG injection timing delay relative to the methanol injection timing on the formaldehyde and the unburned methanol emissions of a methanol blended with LPG engine during cold start were experimentally investigated using the single-cycle methanol injection strategy on an engine with fuel injection spark-ignition controlled electronically.The LPG offers only a function of supplementing start in methanol blended with LPG engines.The results show that the increase of the mass ratio of injected LPG to methanol improved firing performance of the methanol blended with LPG engine and reduced the unburned methanol emission.Optimal control of the LPG injection timing delay improved firing performance and reduced the unburned methanol emission significantly,and increased the formaldehyde emission slightly.At 276°of the LPG injection timing delay,the maximum pressure in cylinder reached 4.46 MPa and the unburned methanol emission decreased to 1173×10-6.The emissions of formaldehyde and unburned methanol of the methanol blended with LPG engine during cold start varied inversely with the mass ratio of injected LPG to methanol and the LPG injection timing delay.