【摘要】 建立了一个适用于超临界压力下包括能够正确描述跨临界迁移现象的液滴燃烧模型,提出了跨临界迁移时刻液滴表面处燃料质量流束有限的新观点.利用开发的计算模型,以碳氢燃料液滴自燃着火为研究对象,研究了亚临界和超临界压力下单液滴的燃烧特性,并从传热传质过程出发,阐明了跨临界迁移前、后液滴燃烧过程的热质输运机理及物理控制因素.结果表明:在亚临界压力下,液滴燃烧不会发生跨临界迁移现象,燃烧过程始终受燃料在液滴表面处相变的控制,液滴的燃烧速度取决于传热过程,并且液滴温度受该压力下燃料沸点的限制而增长缓慢.而在超临界压力下,液滴着火之后很快发生跨临界迁移现象,此后燃料向燃烧反应区域的扩散不存在相变,液滴的燃烧速度取决于传质过程,并且液滴温度不再受燃料沸点的限制而持续升高.更多还原

【Abstract】 A droplet combustion model which can correctly describe the transcritical transition phenomenon in super-critical pressure environment was built up. A new perspective was proposed that the mass stream is limited when the droplet surface is under transcritical transition time. Based on the developed model,the combustion characteristics of single droplet in sub- and super-critical pressure environment were studied. Being the spontaneous ignition of hydrocarbon fuel droplet as the research object,and heat and mass transport mechanism and physical factors controlling the droplet combustion process before and after the transcritical transition are expounded by analyzing on the heat and mass transfer process. Result shows that droplet ignition does not have the transcritical transition phenomenon under the sub-critical pressure environment,and the combustion process is controlled by the phase change of fuel on the droplet surface. Droplet combustion rate depends on the speed of heat transfer,and droplet temperature increases slowly because of the boiling point limitation under the sub-critical pressure. Droplet will quickly approach transcritical transition phenomenon after the ignition under super-critical pressure,and there is no phase change during fuel diffusing into the combustion zone. Moreover,droplet combustion rate depends on the speed of mass transfer,and droplet temperature increases continuously without the boiling point limitation.更多还原