甲醇/ICTL柴油机低负荷燃烧与排放特性的研究

Research on the Combustion and Emission Characteristics for an Methanol/ICTL Diesel Engine under Low Load Condition

在一台满足国六排放法规的四缸柴油机上采用甲醇/ICTL双燃料燃烧模式,实验研究了预喷策略耦合EGR对其在低负荷工况下燃烧稳定性的影响规律。结果表明:在研究工况下,相比于纯ICTL燃烧模式,甲醇替代率为15.2%时,SOOT和NOx的降幅分别为66.3%和33.5%,但COV(p)接近5%的上限标准,燃烧稳定性变差,限制了甲醇替代率的进一步提高;较早的预喷正时(-19℃A)有助于改善甲醇混合气活性,降低SOOT排放,但NOx排放量会增高,过早的预喷正时(超过-29℃A)能够进一步降低SOOT排放,而NOx排放量基本保持不变,但COV(p)超过25%;增加预喷油量会降低SOOT排放量,但NOx排放量增高,当预喷油量为2.1mg/cyc时,COV(p)为15.2%;提高EGR率,能够有效降低NOx排放量,并提高燃烧稳定性,当EGR率提高至35%时,COV(p)为2.99%。

The influence of pre injection strategy coupled with EGR on combustion stability of a methanol/ICTL dual fuel engine under low load conditions was experimentally studied,which is modified by a four cylinder diesel engine that meets the national VI emission regulations.The results showed that under the study conditions,SOOT and NOx significantly declined by 66.3%and 33.5%compared to the pure ICTL mode when the methanol substitution rate was 15.2%.How-ever,COV(p)was close to the upper limit standard of 5%,which limits the further improvement of methanol substitution rate;Early pilot injection timing(-19℃A)is useful for improving the activity of methanol mixture and reduce SOOT emissions,but NOx emissions will increase.Early pre injec-tion timing(exceeding−29℃A)can further reduce SOOT emissions,while NOx emissions remain basically unchanged,but COV(p)exceeds 25%;Furthermore,the SOOT emissions are reduced with increasing pilot injection quantity,but the NOx emissions will increase and the COV(p)is 15.2%,when the pilot injection quantity is 2.1mg/cyc;NOx emissions greatly reduced and the combustion stability effectively increased with increasing the EGR rate.When the EGR rate is increased to 35%,the COV(p)is only 2.99%.