【摘要】 为了解决微型均质压燃自由活塞发动机燃烧温度和压力过高、尾气排放氮氧化物浓度高的问题，采用数值模拟的方法，建立微型均质压燃自由活塞发动机的数值模型，并通过与试验结果的对比验证模型的正确性。在此模型基础上，以水蒸气为稀释剂，研究燃料稀释和进气稀释对微型氢气均质压燃自由活塞发动机燃烧和氮氧化物排放特性的影响。研究结果表明：水蒸气的存在会延迟着火时间；在燃料稀释方式下，当稀释率由0增加至0.1时，最高燃烧温度降低145 K，最高压力降低1 MPa，氮氧化物排放浓度降低69%，但同时平均有效指示压力下降了0.11 MPa；而在进气稀释方式下，最高燃烧温度和氮氧化物排放下降的幅度较小，且最高燃烧压力呈现先增加后减少的趋势。因此，在降低燃烧温度、压力和氮氧化物排放方面，燃料稀释的效果较好，但发动机的做功能力会随燃料稀释率的增大而降低。更多还原

【Abstract】 To address the issues of excessively high combustion temperature and pressure, as well as high concentrations of nitrogen oxides in the exhaust gases of micro-HCCI free-piston engines, a numerical simulation approach was employed. Initially, a numerical model of the micro-HCCI free-piston engine was established and validated against experimental results to confirm its accuracy. Based on this model, the effects of fuel dilution and intake air dilution on the combustion and NO_x emission characteristics of a miniature hydrogen homogeneous compression-ignition free-piston engine were investigated using water vapor as the diluent. The results show that the presence of water vapor delays the ignition moment. In the fuel dilution mode, when the dilution rate increases from 0 to 0.1, the maximum combustion temperature decreases by 145 K, the maximum pressure decreases by 1 MPa, and NO_x emission concentrations decrease by 69%, but at the same time, the average effective indicated pressure decreases by 0.11 MPa. In the intake dilution mode, the decreases of the maximum combustion temperature and NO_x emissions are smaller, and the maximum combustion pressure shows a tendency to initially increase and then decrease. Therefore, fuel dilution is more effective in reducing combustion temperature,pressure, and NO_x emissions, but the power output of the ergine will decrease with the increase of fuel dilution rate.更多还原