后喷策略对柴油机低负荷点排气温度及燃烧影响

Effect of Rear Injection Strategy on Exhaust Temperature and Combustion of Diesel Engine at Low Load Point

以某高压共轨重型柴油机为研究对象,利用converge软件建立了缸内燃烧数值模型,通过采集台架试验数据验证了模型的准确性,分析了单次后喷正时和喷油量对排气温度和缸内燃烧的影响规律。以排气温度为指标,基于单次后喷最优结果,提出并优化了双次后喷策略,分析了双次后喷对缸内燃烧的影响机理。结果表明,单次后喷喷油量一定时,排气温度随单次后喷正时增大呈先增大后减小趋势,单次后喷正时25°CA时,排气温度最高,相比无后喷工况排气温度提高146.2℃。在单次后喷基础上,优化双次后喷喷油量组合和双次后喷间隔。结果表明,在后喷油量相同时,双次后喷相比单次后喷可有效提高排气温度,且排放水平相当。第一次喷油量50%、第二次喷油量50%、间隔10°CA时,排气温度提高19.3℃。

Taking a high pressure common rail heavy diesel engine as the research object,a numerical model of in-cylinder combustion is established using the converge software.The accuracy of the model is verified by collecting bench test data,and the influence law of single rear injection timing and fuel injection amount on exhaust temperature and in-cylinder combustion is analyzed.Taking exhaust temperature as the target,based on the optimal result of single rear injection,the strategy of double rear injection is proposed and optimized,and the influence mechanism of double rear injection on combustion in cylinder is analyzed.The results show that the exhaust temperature increases first and then decreases with the increase of the single rear injection time when the injection amount is constant.When the single rear injection time is 25℃A,the exhaust temperature is the highest,which increases by 146.2℃ compared with the condition without the single rear injection time.Based on the single rear injection,the combination of double rear injection and the interval of double rear injection are optimized.The results show that compared with single rear injection,double rear injection can effectively increase the exhaust temperature,and the emission level is similar.When the first injection volume is 50%,the second injection volume is 50%,and the interval is 10℃A,the exhaust temperature is increased by 19.3℃.