过量空气系数对HCNG发动机燃烧排放的影响

Effects of excess air ratio on the combustion and emission characteristics of HCNG engines

为了使天然气掺氢(HCNG)发动机达到更好的经济性和排放性,在一台6缸天然气发动机上研究了过量空气系数(λ)与掺氢体积比对HCNG发动机燃烧、效率及废气排放的影响。结果表明:对各种掺氢比燃料,随着λ增大,最大燃烧放热率都降低,燃烧持续期增加,发动机指示热效率、NOx排放先增后降,CH4、CO排放先降后增;掺氢天然气相对纯天然气燃烧持续期缩短,因此HCNG发动机相对纯天然气发动机经济性和排放性更好。对于发动机的每个工况,都存在一个最佳的λ,使得发动机的各种性能达到最优平衡。

The influence of the excess air ratio （λ） and the hydrogen blending ratio on the combustion and emissions of an HCNG fuelled engine were investigated experimentally to improve the economy and emission characteristics of the HCNG engine. The results show that, regardless of the hydrogen blending ratio, the maxinum burn rate decreases, the NOx emissions first increase and then decrease, while the CH4, CO emissions first decrease and then increase as λ increases, The addition of hydrogen into CNG increases the burn rate and improves the engine＇s efficiency and emissions. Each operating condition has an optimal λ which makes the engine achieve best overall performance.