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为了提高30μm以下小密度颗粒的分离效率,采用κ-ε/RNG模型和DPM模型对改造后的两级旋风分离器内含尘气流的流动及分离特性进行了三维数值分析。将气体相作为连续介质,采用κ-e湍流模型对流场进行数值模拟;将颗粒相作为离散体系,采用随机轨道模型对颗粒的运动轨迹进行追踪,并分析其阻力与分离效率。结果表明,与常规分离器不同,气流进入两级分离器内筒后出现上、下分流。在外筒近壁柱体和锥体区均有涡流,中心轴线上无滞流、倒流现象。同一高度轴向速度呈非轴对称分布,切向速度基本呈轴对称分布。不司高度截面轴向速度分布差异较大,切向速度分布规律较一致。研究表明,随粒径增大,颗粒逃逸率减小,分离效率增大,但捕捉率则先增后减。粒径为5μm时分离效率达60%,比常规分离器分离效率有较大提高。运动路径、分离时间的增加以及内外筒切向速度的差异足使分离效率提高的主要因素。
In order to improve the separation efficiency of small-density particles below 30μm, three-dimensional numerical analysis of flow and separation characteristics of the dust-laden gas flow in the modified two-stage cyclone was carried out by using κ-ε / RNG model and DPM model. Using the gas phase as a continuous medium, the κ-e turbulence model was used to simulate the flow field. The particle phase was used as the discrete system. The trajectory of the particle was tracked by random orbital model, and its resistance and separation efficiency were analyzed. The results show that, unlike the conventional separators, the gas flow enters the two-stage separator after the upper and lower shunt. In the outer cylinder near the cylinder wall and the cone region has a vortex, no stagnation on the central axis, the phenomenon of backflow. The same height axial velocity was non-axisymmetric distribution, tangential velocity basically axisymmetric distribution. The axial velocity distributions of the section at different height are quite different, and the law of tangential velocity distribution is more consistent. The results show that as the particle size increases, the particle escape rate decreases and the separation efficiency increases, but the capture rate increases first and then decreases. Particle size of 5μm separation efficiency of 60%, compared with the conventional separator separation efficiency has been greatly improved. Movement path, separation time increase and the difference between the tangential speed of the inner and outer cylinder enough to improve the separation efficiency of the main factors.