不同喷射策略对甲醇稀燃直喷发动机性能的影响

For a single-cylinder direct-injection spark-ignition lean-burn methanol engine, the influence of multiple injection strategies on engine performance is investigated. Three experimental groups with three different injection strategies are selected for a total of 22 operating conditions to explore the impact of varying injection frequencies, timing, and fuel proportions on the engine' s power, economy, and emissions performance. The research results show that compared to single injection, multiple injections can effectively optimize the in-cylinder combustion process of methanol engines, concentrating the maximum in-cylinder pressure and its corresponding crank angle distribution, significantly reducing the number of degradation cycles by up to 85% and cycle-to-cycle variations by up to 65%. While multiple injections may lead to increased CO and HC emissions compared to single injection, systematic optimization of injection and ignition parameters can reduce NO∗ emissions. Under the conditions of this study, the optimal performance is achieved with injection timings of 270°, 180°, and 90° before top dead center for the three injections, with fuel proportions of 0. 38, 0. 42, and 0. 20, respectively. The engine achieves the best comprehensive performance with these settings. Overall, the engine's comprehensive performance under the three injection strategy surpasses that of one or two injections, indicating that the three-injection strategy has higher potential for optimizing the engine's comprehensive performance.