除雾器中细颗粒物湍流扩散模型研究

Research on the turbulent particle dispersion model in baffle demisters

为了研究细颗粒物在除雾器中的运动扩散规律以提高除雾器细颗粒物脱除效率的计算精度,研究粒径小于15μm的雾滴在除雾器中的运动。分别采用欧拉法和拉格朗日方法计算气相场和雾滴轨迹;分别耦合连续随机轨道(CRW)模型和离散随机轨道(DRW)模型对不同粒径(3~15μm)的细颗粒物的脱除效率进行计算,并与实验值进行对比;采用大涡模拟方法(LES)对除雾器中细颗粒物的运动进行进一步对比分析。研究结果表明:2种随机轨道模型能够在一定程度上提高除雾器中细颗粒物脱除效率的计算精度,其对细颗粒物的扩散预测在各向同性的湍流中较准确,而在各向异性湍流中结果并不理想。

To research the particle dispersion regularity in eliminators and improve the calculation accuracy of the droplets separation efficiency, the movement of droplets smaller than 15 μm in diameter in baffle demister was studied. The gas phase flow field was determined with Eulerian method and the droplet trajectories were computed by applying the Lagrangian method. Two turbulent dispersion models, i.e., discrete random walk （DRW） model and the continuous random walk （CRW） model, were used to predict the turbulent dispersion of the droplets. The separation efficiencies of the droplets （3 to 15 μm in diameter） were calculated and compared with the experiment results. Large eddy simulation （LES） was also used to predict the motion of droplets for further comparative analysis. The results show that the two turbulent dispersion models can improve the accuracy of the droplets separation efficiency computation. The stochastic trajectory models can predict the particle dispersion in homogeneous isotropic turbulent flows well while they have not good performance in inhomogeneous turbulent flows.