为进一步改善船用低速二冲程甲醇-柴油双直喷发动机的燃烧与排放性能，以缸径500 mm扩散燃烧模式低速二冲程甲醇-柴油双燃料机为研究对象，应用Converge软件开展了发动机在额定负荷工况下的工作过程三维CFD数值模拟研究。系统分析了柴油-甲醇喷射间隔（0~4 °CA）、柴油喷射正时（361~363 °CA）以及甲醇喷射角度（-30 °~+10 °）对燃烧过程、动力性、经济性及NOx排放的影响。结果表明：适当缩短喷射间隔或提前柴油喷射正时均可提高发动机动力性和经济性，但NOx排放上升；综合考虑动力性、经济性与排放，喷射间隔1 °CA、柴油喷射正时362.5 °CA为最优组合。甲醇喷射角度对燃烧影响较小，当甲醇喷射角度向柴油侧靠近10 °（即-10 °）时，发动机动力性能、经济性能和排放水平均为最佳。本研究针对低速二冲程机特有的喷油器缸盖边缘对置布置方式，给出了喷射间隔、柴油正时及喷射夹角的优化值，为同类机型喷射策略设计提供了数值依据。

To optimize the combustion and emission performance of marine low-speed two-stroke methanol-diesel dual-fuel direct-injection engines and support maritime carbon reduction targets, this study focuses on a diffusion combustion mode low-speed two-stroke methanol-diesel dual-fuel engine with a bore diameter of 500 mm. The working process of the engine at rated power condition was numerically simulated using the three-dimensional CFD software Converge. A systematic analysis was conducted to examine the effects of the diesel-methanol injection interval (0–4 °CA), diesel injection timing (361–363 °CA) and methanol injection angle (–30 ° to +10 °) on in-cylinder combustion, power output, fuel economy and NOx emissions. The results indicate that appropriately shortening the injection interval or advancing the diesel injection timing can improve both engine power and fuel economy, although NOx emissions increase; taking both performance and emissions into account, an injection interval of 1 °CA and a diesel injection timing of 362.5 °CA constitute the optimal combination. The methanol injection angle has a relatively minor effect on combustion; when the methanol injection angle is shifted 10 ° closer to the diesel injection side (i.e. -10 °), the engine’s power performance, fuel economy and emission levels are all at their best. This study provides optimized values for injection interval, diesel injection timing and injection angle, considering the arrangement of methanol and diesel injector arrangement on the periphery of the cylinder head, thereby offering a numerical basis for the design of injection strategies for similar engine types.

国家自然科学基金项目（面上项目，重点项目，重大项目）；奥托循环氨燃料发动机燃烧关键技术研究