直喷发动机燃用天然气掺氢混合燃料的性能与排放

对缸内直喷火花点火发动机燃用天然气氢气混合燃料时的性能与排放进行了试验研究．研究结果表明：在喷射脉宽一定的条件下，当天然气掺氢比例小时，平均有效压力和热效率有所下降，当掺氢比例达到一定值（即氢的体积分数为5％～10％）后，平均有效压力和热效率增加，此现象在稀混合气条件下更加明显，表明天然气掺氢对稀混合气燃烧过程的改善有显著作用；发动机HC和CO2的排放浓度随天然气中掺氢比例的增加而下降，原因是掺氢增加了混合燃料中氢碳的量的比值和混合气过量空气系数；在稀混合气条件下，发动机的NQ的排放浓度随掺氢比的增加而有所降低，CO的排放浓度基本上不随掺氢量的改变而改变。

Performance and Emissions of a Direct-Injection Engine Fueled with Natural Gas/Hydrogen Blends

An experimental study was conducted on performance and emissions of a direct--injection spark ignited engine fueled with natural gas/hydrogen blends. The results show that for a fixed fuel injection duration, the brake mean effective pressure and effective thermal efficiency would decrease with the addition of hydrogen in natural gas when hydrogen addition fraction is small and would increase with the increase of hydrogen fraction in natural gas when hydrogen fraction reaches up to 5 percent to 10 percent. This phenomenon is more obvious in the case of lean combustion, indicating a strong influence of hydrogen addition on lean mixture combustion. The exhaust HC and CO2 decreased with the increase of hydrogen fraction in natural gas, and this would be due to the increase in H/C ratio and excessive air ratio. Under the circumstance of lean mixture combustion, exhaust NOx decreased slightly with the increase of hydrogen addition while exhaust CO had little variation with hydrogen addition.