预燃室式柴油-天然气双燃料船用发动机热效率优化燃烧控制策略仿真研究

基于CONVERGE软件建立了预燃室式柴油/天然气双燃料船用二冲程发动机的三维计算流体动力学（computational fluid dynamics，CFD）模型，研究了压缩比、引燃柴油质量和喷射压力、引燃柴油喷射角度对燃烧过程的影响，探索了提高柴油/天然气双燃料船用发动机热效率的燃烧策略。结果表明：提高压缩比可以提高缸内的最大爆发压力，从而有效提高热效率，但受发动机机械强度的限制，压缩比为12.5时可以获得较佳的效果；适当增大引燃油量和喷射压力，可以使射流火焰的着火点增加，点火能量增强，对热效率略有改善；调节引燃柴油的喷射角度，将引燃油喷射到CH4浓度较高区域可以获得更好的引燃效果，降低指示燃料消耗率；提高压缩比至12.5结合推迟喷油策略对热效率的改善效果更为明显。

Simulation Study on Improving Thermal Efficiency of Diesel/Natural Gas Dual Fuel Marine Engine

Based on the converge software, a three-dimensional computational fluid dynamics (CFD) model of pre-chamber diesel/natural gas dual fuel two-stroke marine engine is established. The effects of compression ratio, pilot diesel mass and injection pressure, pilot die-sel injection angle on the engine combustion process are studied in order to improve the thermal efficiency. The results show that in-creasing compression ratio can increase the peak cylinder pressure and improve thermal efficiency effectively, but limited by the me-chanical strength of the engine, the compression ratio of 12.5 in this study can obtain better effect. Increasing the mass and pressure of pilot diesel appropriately can increase the ignition point and enhance the ignition power of jet flame, which is conducive to improve thermal efficiency. By adjusting the injection angle of pilot diesel and conduct the pilot diesel to the region with more methane can get better ignition effect and reduce the indicated specific fuel computation. Increasing the compression ratio by 12.5 combined with delaying the injection time of pilot diesel can get a more significant effect on improving the thermal efficiency.