火花点燃式甲醇汽油发动机冷起动过程燃烧特性研究

With the application of EURO Ⅲ and more stringent legislations, engine emissions during cold start become a major part to be controlled. A 3-cylinder port fuel injection (PFI) engine fueled with methanol-gasoline blends was used to study combustion and emission characteristics during this process. The cylinder pressure analysis indicates that engine combustion is improved with the methanol addition into gasoline. With the increase of methanol fraction, the flame developing period and the fast combustion period are shortened, the Indicated Mean Effective Pressures becomes higher during the first 100 cycles. Meanwhile, a novel quasi-instantaneous sampling system was designed to measure engine emissions during cold start and warm-up processes. The results at 5℃ show that the unburned hydrocarbon (UHC) and carbon monoxide (CO) decrease obviously. HC is reduced about 40% and CO is reduced nearly 70% when the engine is fueled with M30 (30% methanol in volume) during cold start and warm-up period. The exhaust gas temperature is about 140 ℃ higher in 200s after starting compared with gasoline.