单滴碳氢燃料的燃烧特性

Study on the Droplet Combustion Characteristics of Hydrocarbon Fuel

建立了单滴燃料燃烧过程的计算模型和数值方法 ,并用之计算单滴燃料的蒸发和燃烧过程。计算发现 ,环境空气压力和燃料临界压力相近时 ,液滴具有最小的燃烧时间 ,即液滴寿命最短 ;当环境压力低于燃料临界压力时 ,燃烧时间随着环境介质压力的增大而降低 ,这是因为在燃烧期内 ,气液界面一直存在 ,气液界面间的相平衡控制着蒸发速率 ,进而控制着燃烧时间 ;环境空气压力高于燃料临界压力时 ,着火后液滴表面很快变为超临界状态 ,其后不存在相变过程 ,燃料的燃烧速率主要受控于燃料和氧气的扩散速率。由于扩散系数几乎与压力成反比 ,所以 ,随着压力增高 ,燃料从高浓度区向火焰区域扩散的速度减小 。

WT5”BZ]Since the single droplet combustion is one of the basic process in the liquid fuel spray combustion,it is very important to study the basic process so as to further improve and perfect the combustion process.The calculation model of the single droplet combustion process was established.It can be found from the calculation that when the ambient pressure is equal to the fuel critical pressure,the droplet will have the minimum combustion time and the droplet lifetime.When the ambient pressure is lower than the fuel critical pressure,the combustion time will decrease with the increasing of ambient pressure.As the gas liquid interface always exists in the combustion process,the phase equilibrium will control the evaporation rate and combustion time.When the ambient pressure is higher than the fuel critical pressure,the droplet surface will soon be transformed into a supercritical state after ignition and the phase transformation will not exist at that time.The combustion rate of fuel is controlled by the diffusion rate of fuel and oxygen.The diffusion coefficient and the pressure are inversely proportional,therefore the higher the ambient pressure,the longer the combustion time is. [WT5”HZ]