预燃室参数对射流点火甲醇发动机起动着火性能的影响

Effect of Pre-Chamber Parameters on Start Performance of Jet Ignition Engine Fueled with Methanol

针对点燃式甲醇发动机存在的冷起动困难问题,采用预燃室射流点火技术提高甲醇发动机的火焰传播速度和燃烧稳定性。基于单缸发动机台架试验,研究了射流孔孔径、预燃室燃油喷时刻以及预燃室燃油喷射量等参数对射流点火甲醇发动机冷机着火性能的影响。试验结果表明:预热室射流点火甲醇发动机在进气歧管开始喷油的数个循环之后才会出现第一个成功点火循环,并且从首次成功点火循环到发动机进入稳定燃烧状态之间存在成功点火与失火交替出现的过渡状态,表现为平均指示压力(IMEP)的大幅度振荡;射流孔的总流通面积与发动机的冷机着火性能关系密切,单孔2 mm预燃室由于射流孔的总流通面积过小、换气困难,废气无法有效排出,使得发动机长时间处于成功点火与失火交替出现的过渡状态;而单孔4 mm、单孔6 mm及三孔2.3 mm预燃室,由于总流通面积增大,冷机着火性能明显提升;在冷机状态下,预燃室喷射时刻对射流点火甲醇发动机的冷机着火性能影响不大,而提高预燃室喷油量可以明显提前成功着火循环出现的时刻,能有效改善射流点火甲醇发动机的冷起动性能。

For the cold start difficulty of methanol ignition engine,the pre-chamber jet ignition technology was used to improve the flame propagation speed and combustion stability.The single-cylinder engine bench test was conducted to study the effects of jet orifice diameter,injection timing and injection quantity in the pre-chamber on the ignition performance of methanol jet-ignition engine.The test results show that the first successful ignition cycle does not occur until several cycles after the fuel injection starts in the intake manifold and the alternate transition between successful ignition and misfire cycle exists with a large oscillation of average indicated pressure(IMEP)during the process of first successful ignition to stable combustion state.The total flow area of jet hole is closely related to the ignition performance of cold engine.The total flow area of 2 mm single jet hole in the pre-chamber is so small that the ventilation is difficult,and hence the exhaust gas cannot be effectively discharged so as to produce a long-term transition state.The performance of cold start improves significantly due to the increase of total flow area after using 4 mm single jet hole,6 mm single jet hole and 2.3 mm three jet holes.In addition,the injection timing of pre-chamber has little effect on the cold start performance,while increasing the injection amount of pre-chamber can significantly advance the timing of successful ignition cycle and hence improve the cold start performance of methanol jet-ignition engine.