点火位置对天然气直喷超稀燃烧影响的基础性研究

利用快速压缩装置进行了点火位置对天然气直喷超稀燃烧的基础性研究，研究结果表明：对于给定的当量比来说，存在一个最佳点火位置，在此位置点火时可以获得最短的燃烧持续期、最大的压力升高值、最高的燃烧效率，最快的燃烧放热率和最低的CO和未燃碳氢排放。最佳点火位置随当量比的减小而移向喷油嘴出口位置。当点火位置靠近喷油嘴出口位置时，稀燃极限可以延伸到更小的当量比，但可着火的当量比的范围变得狭窄。当量比大于0.1时，燃烧效率将维持在较高的数值；当量比小于0.1时，因未燃燃油所占的比例增加，燃烧效率明显降低。

A Basic Study on the Spark Electrode Gap Position to Natural Gas Direct Injection Super-Lean Combustion

A basic study on the ignition position to natural gas direct injection super-lean combustion was studied by using a rapid compression machine. The results show that the optimum spark electrode gap position exists for a specified equivalence ratio where it gives short combustion duration, high value of pressure rise, high combustion efficiency, rapid heat release rate, low concentration of CO and unburned hydrocarbon. The optimum spark electrode gap position will be close to the injector tip with the decreasing of equivalence ratio. Lean burn limit can be extended to even smaller equivalence ratio with closing the spark electrode gap to the injector tip whereas the range of equivalence ratios for the flammability becomes narrow with closing the spark electrode gap to the injector tip. High combustion efficiency can be maintained at the equivalence ratio φ≥0.1 and decreases remarkably at φ＜0.1 due to increasing the ratio of unburned fuel to the injected fuel.