两次喷射策略对汽油/聚甲氧基二甲醚高预混燃烧及排放的影响

在一台改造的单缸柴油机上进行了预主喷两次喷射策略对汽油/聚甲氧基二甲醚(PODE)高预混合燃烧(HPCC)影响的试验研究。研究结果表明:预主喷两次喷射策略能缩短主喷滞燃期,提前着火时刻;预主喷间隔较小或较大时,汽油/PODE HPCC燃烧放热率峰值较低;预主喷间隔为35°时燃烧放热率峰值最高,放热更加集中。预喷比例越大,预主喷间隔和主喷时刻对最大压升率和指示热效率的影响越大。通过预主喷两次喷射策略优化,可以显著提高汽油/PODE HPCC燃烧的指示热效率,减少碳氢和碳烟排放,但最大压升率有所增加。高负荷时,汽油/柴油HPCC因为碳烟排放的限制,适合采用两次喷射策略;汽油/PODE HPCC受限于最大压力升高率,更适合采用单次喷射策略。

Effects of Split Injection on Highly Premixed Charge Combustion and Emissions Fueled with Gasoline and Polyoxymethylene Dimethyl Ethers

Experiments have been conducted to explore the effects of split injection strategy on highly premixed charge combustion(HPCC) fueled with polyoxymethylene dimethyl ethers(PODE) and gasoline on a modified single-cylinder heavy-duty diesel engine. The results show that the split injection strategy can shorten the ignition delay and advance the auto-ignition timing. Lower heat release rate can be obtained with a smaller or larger injection interval for HPCC of gasoline and PODE, and the highest heat release rate with compact heat release pattern can be obtained with the injection interval of 35° crank angles. The effects of injection interval and main injection timing on the maximum pressure rise rate and indicated thermal efficiency are enhanced with higher pilot injection ratio. An optimized split injection strategy can significantly improve the indicated thermal efficiency, and reduce total HC and soot emissions; however, penalty in the maximum pressure rise rate is also observed with such strategy. It is seen that the split injection strategy can be helpful to reduce soot emission from HPCC of gasoline and diesel at high loads, while single injection strategy is more suitable for HPCC of gasoline and PODE for pressure rise rate suppression.