喷射压力对电热塞引燃甲醇发动机的影响研究

基于电热塞引燃式直喷甲醇发动机,采用三维数值模拟方法研究了喷射压力对甲醇雾化、空燃混合、燃烧、排放的影响。研究表明:提高喷射压力使可燃混合气的均匀程度提高,而缸内平均温度和压力降低。火核形成于电热塞端部,火焰传播呈现出与柴油机和汽油机不同的规律。在高喷射压力下,处于靠近电热塞一端的燃烧室凹坑中的可燃混合气首先燃尽,而后火焰向外部传播。在排放物方面,喷射压力越大,膨胀行程中甲醛的含量越高,但排气中甲醛残余量越低,膨胀段甲醛与排气过程产生的甲醛相比可忽略不计。增大喷射压力有利于增加发动机的膨胀功,提高动力性,但喷射压力过高导致早燃,反而有损动力输出。

Effects of Injection Pressure on Methanol Engine Ignited by Glow Plug

The effects of injection pressure on methanol atomization,air-fuel mixing,combustion and emissions were studied by three-dimensional numerical simulation based on the glow plug piloted direct-injection pure methanol engine.The results show that the increase of injection pressure will lead to the uniformity of in-cylinder mixture and the decrease of in-cylinder average temperature and pressure.The ignition occurs at the end of electric plug and the flame propagation shows a law different from diesel and gasoline engine.The mixture in the combustion chamber pit near the end of electric plug burns out first and then the flames spread to the surrounding space under high injection pressure.The higher injection pressure will lead to the higher formaldehyde content in expanding process,but it will also lead to the less formaldehyde residual in the exhaust.Compared with the formaldehyde content of exhaust process,that of the expansion process can be negligible.Increasing injection pressure is beneficial to increase engine expansion power and improve power performance,but too high injection pressure will lead to premature combustion which will deteriorate power output.