【摘要】 基于某重型甲醇气道喷射(PFI)发动机开展缸内直喷点燃(DISI)燃烧系统开发，系统研究了进气道结构和喷油策略等对重型甲醇DISI发动机流动、燃烧及排放的影响.结果表明：双切向进气道能显著增强缸内流速，浓混合气分布区域小，燃烧持续期短，指示热效率绝对值提高了0.68%(46.93%).采用早喷策略可以获得较均匀的混合气分布，指示热效率更高，但火花塞附近的局部当量比较低，点火稳定性较差.晚喷策略可以提高火花塞附近的局部当量比，提高点火稳定性，但热效率会下降，一氧化碳(CO)和未燃甲醇排放升高.提高喷射压力可改善缸内混合气分布，减少浓混合气分布区域，同时克服燃烧室中心区域当量比偏低的问题，显著提高点火稳定性和燃烧效率，此外通过增强缸内湍流强度，加快火焰传播速度和缩短燃烧持续期，在喷射压力为50 MPa条件下，指示热效率达47.46%；提高喷油压力也可降低CO和未燃甲醇排放，但氮氧化物(NO_x)排放有所增加.更多还原

【Abstract】 Based on a heavy-duty methanol port fuel injection (PFI) engine,a direct injection spark ignition(DISI) combustion system development study was carried out to systematically investigate the effects of intake port structure and injection strategy on the flow,combustion and emission of a heavy-duty methanol DISI engine.The results show that the double tangential intake port can significantly enhance the in-cylinder flow rate,with a small local rich mixture distribution area and a short combustion duration,and the absolute indicated thermal efficiency is increased by 0.68%(46.93%).The early injection strategy can obtain a more uniform mixture distribution and higher indicated thermal efficiency,but the local equivalent ratio near the spark plug is low and the ignition stability is poor.The late injection strategy can increase the local equivalence ratio near the spark plug and improve the ignition stability,but the thermal efficiency will be decreased and the carbon monoxide (CO) and unburned methanol emissions will be increased.Increasing the injection pressure can improve the in-cylinder mixture distribution,reduce the thick mixture distribution area,and at the same time overcome the problem of low equivalence ratio in the center area of the combustion chamber,which significantly improves the ignition stability and combustion efficiency.In addition,by enhancing the intensity of in-cylinder turbulence,accelerating the flame propagation speed and shortening the combustion duration,the indicated thermal efficiency reaches 47.46%under the injection pressure of 50 MPa.Increasing injection pressure also reduces CO and unburned methanol emissions,but nitrogen oxide (NO_x) emissions increase.更多还原