亚/超临界环境下燃料的喷雾燃烧特性研究

采用高温高压定容燃烧弹系统对亚/超临界环境下燃料在纯氧中的喷射燃烧现象进行试验研究,通过高速相机和阴影法进行燃烧图像信息的采集,研究在相同的超临界温度下,正己烷和乙醚两种燃料喷射燃烧火焰特性随环境压力和喷油脉宽的改变而呈现的差异性。试验结果表明:在亚临界压力下,两种燃料在不同喷油脉宽下的燃烧时间均随着环境压力的升高而升高,火焰发展后期基本保持较为稳定的形态和亮度,符合传统的喷射燃烧过程。正己烷在临界压力点下火焰长度最短,形态较为规则;超临界压力下,火焰形态有稳定趋势但仍有轻微波动,且火焰长度略短于亚临界;喷油脉宽改变时,燃烧时间在临界压力附近呈现出不同的趋势。乙醚的燃烧时间随压力的升高而增大,在临界压力处达到最大值,后随着压力的继续升高而下降,不同压力条件下火焰形态略有差别。燃烧现象存在差异性主要是由于亚/超临界坏境下燃料的物性参数和破碎蒸发机理不同。

Study on Fuel Sprayc Combustion Characteristics in Sub- and Super-Critical Environments

The combustion phenomena of fuel injection in sub- and super-critical oxygen environments was studied by using high temperature and high pressure constant volume bomb system. The combustion image information was collected by high speed camera and shadow method. At the same super-critical temperature, the difference of flame characteristics with the change of ambient pressure and injection pulse width was studied. The n-hexane and ether were used in the experiment. The experimental results show that the combustion time of the two fuels increases with the increase of ambient pressure at different injection pulse widths under sub-critical pressure, and the flame keeps a relatively stable shape and brightness in the stage of flame development, which conforms to the traditional spray combustion process. When n-hexane is at the critical pressure, the flame length is the shortest and its shape is more regular; at the super-critical pressure, the flame shape has a stable trend but still has light microwave motion, and flame length is slightly shorter than sub-critical. When the injection pulse width changes, the combustion time shows a different trend near the critical pressure. The combustion time of ether increases with the increase of pressure, reaches the maximum at the critical pressure, and then decreases with the increase of pressure; the flame morphology is slightly different under different pressure conditions. The difference of combustion phenomena is mainly due to the different physical parameters of fuel and the mechanism of fragmentation and evaporation under sub- and super-critical conditions, which provides a basis for further experimental and simulation research.