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为研究气相湍流场中液滴弥散和蒸发过程的特点和影响因素,加深对气液耦合作用的认知,用欧拉-拉格朗日相结合的办法数值模拟了稀液雾冷态受限射流和自由射流。欧拉坐标系下的气相湍流场使用大涡模拟技术模拟,离散液相则使用拉格朗日颗粒轨道模型进行描述,考虑相间质量、动量、能量交换,采用相平衡蒸发模型模拟液相的蒸发效应。模拟得到的液相速度场、粒径分布和质量流率等均和实验数据较好吻合。有回流的受限射流中初始惯性对Stokes数大的液滴弥散影响较大,而Stokes数在1附近的小液滴弥散更受气相流场结构影响。液雾单位体积蒸发速率和液滴弥散分布密切相关。自由射流中液滴受初始惯性和受气相流场作用大体一致,大小液滴的弥散分布基本满足自相似性。
In order to study the characteristics and influencing factors of liquid droplet diffusion and evaporation in the gas-phase turbulent flow field and to deepen the cognition of the gas-liquid coupling action, the Euler- Jet and free jet. In the Euler coordinate system, the gas-phase turbulence field is simulated by large-eddy simulation, while the discrete liquid phase is described by Lagrangian particle orbit model. The phase-equilibrium evaporation model is used to simulate the evaporation of the liquid phase considering the interphase mass, momentum and energy exchange effect. The simulated liquid velocity field, particle size distribution and mass flow rate are in good agreement with the experimental data. The initial inertia of the confined jet with back flow greatly affects the dispersion of large droplets of Stokes number, whereas the dispersion of small droplets with a Stokes number near 1 is more affected by the structure of the flow field in the gas phase. The volumetric evaporation rate of liquid mist is closely related to the dispersion of droplets. The droplets in a free jet are basically consistent with the initial inertia and the gas flow field, and the dispersion of the size droplets basically satisfies the self-similarity.