【摘要】 在CONVERGE中建立氨气道喷射和缸内直喷两种氨/柴油双燃料发动机三维模型；经试验数据验证后，研究了转速为1 200 r/min、柴油喷油量为5 mg/cyc及氨能量替代率为60%小负荷工况下双直喷模式的燃烧与排放特性，并与气道喷射模式对比，探究了氨两次喷射的影响．结果表明：缸内直喷氨通过柴油引燃实现扩散燃烧，提高了燃烧速度并缩短燃烧持续期；氨直喷时刻为0°CA ATDC时，平均指示压力（0.34 MPa）和指示热效率（34.9%）较气道喷射提高近一倍．小负荷下双直喷模式缸内平均温度接近1 200 K，利于选择性非催化还原（SNCR）反应，降低NO_x排放；同时，较高的缸内温度和更快的扩散燃烧速度使得N₂O和未燃NH₃排放明显下降．氨两次喷射相比单次喷射可提高热效率，合理的喷射时刻可以显著降低N₂O和未燃NH₃排放，但会增加NO_x排放；优化参数后氨两次喷射相比单次喷射当量温室气体（CO₂）排放最多减少37%.更多还原

【Abstract】 Three-dimensional CFD models of an ammonia/diesel dual fuel engine were developed using CONVERGE software for ammonia port injection mode and dual fuel direct injection（DI） mode respectively. The models were validated against engine experimental data. The combustion and emission characteristics of the dual direct injection mode were investigated at 1 200 r/min under low-load conditions,with a diesel injection quantity of 5 mg/cyc and an ammonia energy substitution ratio of 60%. The effects of split ammonia injection were examined by comparing with ammonia port fuel injection mode. Results show that direct in-cylinder ammonia injection,ignited by diesel,promotes diffusion combustion,increases the combustion rate,and shortens the combustion duration. When the ammonia injection timing is 0° CA ATDC,the indicated mean effective pressure（0.34 MPa） and indicated thermal efficiency（34.9%） are nearly twice those of ammonia port injection mode. In the dual direct-injection mode under low-load conditions,the average in-cylinder temperature approaches 1 200 K,which favors selective non-catalytic reduction（SNCR） reactions,thereby reducing NO_x emissions. Meanwhile,the relatively high incylinder temperature and faster diffusion combustion further reduce N₂O and unburned NH₃ emissions. Compared with single injection,split ammonia injection further improves thermal efficiency. With optimized timing,this strategy markedly reduces N₂O and unburned NH₃ emissions,albeit with increased NO_x. Under optimized parameters,split ammonia injection achieves up to a 37% reduction in equivalent greenhouse gas（CO₂） emissions compared with single injection.更多还原