不同湍流强度下液雾燃烧的直接数值模拟

Direct Numerical Simulation of Spray Combustion with Various Turbulent Intensities

采用欧拉方法求解气相场,采用拉格朗日方法跟踪液滴颗粒,对液雾燃烧进行了直接数值模拟研究.分析了不同湍流强度下液雾燃烧的液滴蒸发特性和燃烧特性.发现在低混合分数区域,液滴蒸发速率约等于零.当混合分数大于夹层内平均混合分数的时候,液滴蒸发速率随混合分数线性增加.液雾燃烧的着火时间与相同条件下气体混合物的着火时间相比会更长.湍流在混合分数空间中抑制了液体燃料的蒸发,但是能够加强燃料和氧化剂的混合,从而进一步促进化学反应的进行.

Direct numerical simulation is employed to investigate spray combustion. The gas phase is simulated using the Eulerian approach, while the droplets are treated with the Lagrangian method. The droplet evaporation and combustion characteristics of spray combustion with various turbulent intensities are analyzed. It is found that the conditionally averaged evaporation rate almost vanishes in low mixture fraction regions, and it increases linearly when the mixture fraction is larger than the mean mixture fraction in the slab layer. The ignition delay time of spray combustion is larger than that of gaseous combustion. The conditionally averaged evaporation rate decreases with turbulent inten- sity in the mixture fraction space, while the conditionally averaged heat release rate and temperature generally increase with turbulent intensity due to the enhanced mixing between the fuel and oxidizer.