点燃式氨氢燃料发动机燃烧与排放模拟研究

Numerical Study on Combustion and Emissions of a Spark-Ignition Engine Fueled with Ammonia/Hydrogen Blends

通过三维数值仿真方法研究了化学当量比下掺氢比和点火时刻对点燃式氨氢燃料发动机燃烧与排放的影响。结果表明,增加掺氢比可加速火焰传播,缩短燃烧持续期,提高缸内压力和温度峰值。随着掺氢比增加,未燃氨和N_(2)O排放减少,燃料型和热力型NO生成增多。点火时刻的适当提前可有效改善燃烧特性,平衡NO、N_(2)O和未燃氨的排放。随着点火时刻的推迟,NO排放减少,N_(2)O和未燃氨排放呈相反趋势。然而,过于推迟点火会造成较多未燃氨排放,导致放热不完全,指示热效率下降。

The effects of hydrogen blending ratios and spark ignition timings on the combustion and emissions of a spark-ignition engine fueled with ammonia/hydrogen blends at the stoichiometric condition were investigated.The results show that increasing the hydrogen blending ratio can accelerate flame propagation,shorten the combustion duration,and raise peak in-cylinder pressures and temperatures.Besides,as the hydrogen blending ratio increases,unburned ammonia and N_(2)O emissions decrease,while both the formation of fuel-NO and thermal-NO increase.Properly advancing the ignition timing improves combustion characteristics,balancing the emissions of NO,N_(2)O,and unburned ammonia.With delayed ignition timing,the NO emission decreases,while the N_(2)O and unburned ammonia emissions exhibit an opposite trend.However,increased delay in ignition timing results in the increased emission of unburned ammonia,leading to the incomplete heat release during combustion and the decrease of indicated thermal efficiency.