气液两相正庚烷射流燃烧的直接数值模拟

Direct Numerical Simulation of Gas-Liquid Two-Phase n-Heptane Jet Combustion

本文采用直接数值模拟的方法,对常压下的气液两相正庚烷射流火焰进行了研究,低温空气携带正庚烷液滴作为高速射流进入计算区域,正庚烷液滴在热伴随流的作用下蒸发产生燃料蒸汽,与氧气进一步混合发生燃烧。分析了液滴的蒸发和分布特性,研究了气液两相燃烧中同时存在的预混和非预混燃烧,引入一种修正的火焰因子来区分预混和非预混燃烧模态,发现在上游区域预混和非预混燃烧同时发生在射流边缘,在下游区域预混和非预混燃烧开始出现在射流中心。预混燃烧的强度在全局上高于非预混燃烧的强度,但其对总热释率的贡献沿流向逐渐降低。

In this paper, the direct numerical simulation is employed to study the gas-liquid twophase n-heptane jet flame under atmosphere condition. The low-temperature air carries n-heptane droplets as a high-speed jet into the simulation field. After evaporation, fuel vapor is produced, and is further mixed with oxygen to burn. The evaporation and distribution characteristics of droplets were analyzed, and the simultaneous premixed and non-premixed combustion in gas-liquid two-phase combustion was studied. A modified flame index was introduced to distinguish the premixed and non-premixed combustion modes. It was found that premixed and non-premixed combustion occur simultaneously at the edge of the jet in the upstream location, and begin to appear at the center of the jet in the downstream location. The intensity of premixed combustion is globally higher than that of non-premixed combustion, but its contribution to the total heat release rate gradually decreases along the streamwise location.