未着火循环废气改善柴油机冷起动的燃烧

采用柴油的替代研究燃料正庚烷和压燃式燃烧模型,计算研究了起动阶段引入未着火循环的燃烧产物对下一循环燃烧的影响.未着火循环的燃烧产物与完全燃烧循环有明显不同,其中含有许多未燃燃油和中间活性物质,将其以EGR的方式重新引入气缸中能有效改善下一循环的燃烧,计算结果表明,中间活性物质起到了关键作用.进行了EGR影响柴油机起动性能的试验研究,结果表明,起动初期的循环中,引入EGR可以改善燃烧,试验结果验证了计算分析的合理性,为改善柴油机冷起动性能提供了一种新思路.根据正庚烷燃烧的化学动力学理论,结合计算过程中各物质浓度的变化,研究了EGR改善燃烧的机理.

Utilization of Non-Firing Cycle Exhaust Gases to Improve Diesel Engine Combustion During Cold Start Process

Compression ignition model and diesel fuel alternative(n-heptane)were used to study the influence of non-firing cycle exhaust gases on diesel engine combustion during the cold start process.Exhaust gas of non-firing cycle is greatly different from that of normal combustion which contains residual fuel and active intermediate.Introducing these gases into cylinder can obviously improve the subsequent combustion cycle.It was found that the active intermediates in the exhaust gases play a leading role in the process.For the cold start experiment of diesel engine which introduces EGR,it was found that EGR could remarkably increase the in-cylinder pressure and heat release rate.The experiment confirmed the calculation results.A new method to improve the cold start performance of diesel engine is presented.Based on nheptane oxidation and analyzing the species concentrations,the mechanism of combustion improvement by introducing non-firing cycle products was studied.