关键词: 内燃机, 可变排气门升程, 废气再循环, 燃烧特性, 排放特性

Abstract:

Based on the self-developed hydraulic variable valve train， the improvement potential of the internal exhaust gas recirculation （EGR） coupled ignition strategy for methanol engine energy saving and emission reduction was studied. The results show that the exhaust valve lift decreases and the internal EGR increases. An increase in internal EGR results in a decrease in the peak cylinder pressure and in-cylinder temperature， a delay in the combustion center， an increase in the combustion duration， and an increase in the variation of the combustion cycle. Properly adjusting the ignition timing， the methanol engine can still distribute the combustion center within a reasonable range and run smoothly even at 42% internal EGR. In addition， internal EGR combined with ignition timing has different effects on improving fuel consumption and emissions under different loads. The effective thermal efficiency and fuel economy are the best at 20% load， which are improved by 3.2% and 12.7% respectively. The NO _x and HC_{emission was the best at 40% load， which decreased by 64.25% and 20.8%， respectively.}

Key words: engine, variable exhaust valve lift, exhaust gas recirculation, combustion characteristics, emission characteristics