直喷发动机燃用天然气掺氢混合燃料的燃烧特性

Combustion Characteristics of a Direct Injection Engine Fueled with Natural Gas/Hydrogen Blends

开展了缸内直喷火花点火发动机燃用天然气掺氢混合燃料燃烧特性和放热过程的试验研究．研究结果表明：在给定喷射脉宽条件下，天然气掺氢比小时，燃烧放热率低，当氢气的体积分数达到10％～18％后，对提高混合燃料发动机燃烧速率有明显效果；火焰发展期、快速燃烧期、燃烧持续期和放热率曲线型心位置对应的曲轴转角随掺氢比增加呈先增加后减小趋势，当氢气的体积分数达到18％时可以缩短火焰发展期、快速燃烧期和燃烧持续期，放热率曲线型心位置对应的曲轴转角靠近上止点；缸内最高燃烧压力、最高燃气平均温度、最大压力升高率和最高放热率随掺氢比的增加呈先减小后增加趋势；天然气掺氢燃烧特性在低转速时比在高转速时受掺氢比的影响大．

The experimental investigation to combustion characteristics and heat release process in a direct injection spark-ignited engine fueled with natural gas/hydrogen blends was executed, For a fixed fuel injection duration, the results show that the heat release rate decreases with the increase of φ（H2） （the hydrogen volume fraction） as φ（H2） is smaller, and increases with the increase of φ（H2） as φ（H2） is over 10%. So only φ（H2 ） reaches a certain level, the combustion can be improved. The flame development duration, the rapid combustion duration and the total combustion duration increase with the increase of φ（H2） when φ（H2） is less than 10% and decrease when φ（H2） increases from 10% to 18%. The crank angle of the center of heat release curve moves apart from the top-dead-center with the increasing φ（H2 ） and gets near the top-deadcenter as φ（H2） reaches to 18%. The maximum cylinder gas pressure, the maximum mean gas temperature, the maximum rate of pressure rise and the maximum heat release rate decrease with the increase of φ（ H2 ） when φ（ H2 ） is less than 10%, and they increase with the increase of φ（H2 ） when φ（H2） increases from 10%to 18%. The investigation shows that the influences of hydrogen addition on natural gas/hydrogen mixture combustion are more obvious at low engine speed than those at high engine speed.