Research on the Deposition and Orientation Characteristics of Cylindrical Particles in a Gas-solid Two-phase Turbulent Flow Through a Curved Tube
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摘要: 针对在Reynolds数Re=3000 ~ 50000、Stokes数St=0.1 ~ 10、Dean数De=1400 ~ 2800的情况下，长径比β=2 ~ 12的圆柱状颗粒流经弯管湍流场时的取向与沉积特性进行了研究。圆柱状颗粒的运动采用细长体理论结合Newton第二定律进行描述，取向分布函数由Fokker-Planck方程给出，平均湍流场通过求解Reynolds平均运动方程结合Reynolds应力方程得到，作用在颗粒上的湍流脉动速度由动力学模拟扫掠模型描述。通过求解湍流场以及颗粒的运动方程和取向分布函数方程，得到并分析了沿流向不同截面和出口处颗粒的取向分布，讨论了各因素对颗粒沉积特性的影响。研究结果表明，随着St和颗粒长径比β的增加、De和Re的减少，颗粒的主轴更趋向于流动方向。颗粒的沉积率随着De、Re、St和颗粒长径比的增大而增加，所得结论对于工程实际应用具有参考价值。Abstract: In the case of Reynolds number Re=3000 ~ 50000, Stokes number St=0.1 ~ 10, Dean number De=1400 ~ 2800, the orientation and deposition characteristics of cylindrical particles with aspect ratio β=2 ~ 12 in a turbulent flow through a curved tube are studied. The motion of cylindrical particles is described by the slender body theory combined with the Newton's second law. The orientation distribution function of cylindrical particles is given by the Fokker Planck equation. The mean velocity of the flow is obtained by solving the Reynolds-averaged Navier-Stokes equation and Reynolds stress equation. The turbulent fluctuating velocity acting on particles is described by the kinetic simulation sweeping model. By solving the equations of turbulent flow and particle motion and orientation distribution function, the orientation distribution of particles on the cross-section at different axial positions and outlet is obtained and analyzed. The effects of various parameters on the deposition rate of particles are discussed. The results showed that the main axis of particles tends to the flow direction with the increase of St and β, and the decrease of De and Re. Deposition rate of particles increases with increasing De, Re and β. However, it shows a non monotonic trend with the change of St. Conclusion has reference value for practical engineering application.
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图 4 平均轴向速度和轴向脉动速度均方根的分布(Re=10500, De=2460)：（a） 平均轴向速度；（b） 轴向脉动速度均方根
Figure 4. Distribution of mean axial velocity and RMS value of fluctuating axial velocity (Re=10500, De=2460): (a) mean axial velocity; (b) RMS value of fluctuating axial velocity
图 5 横截面上颗粒平均取向分布(Re=30000, St=1, De=2200，β=8)
Figure 5. Distributions of mean orientation of particles on cross-section (Re =30000, St =1, De=2200，β=8)
图 6 不同St时颗粒平均取向分布(Re=30000, De=2200, β=8)
Figure 6. Distribution of particle orientation for different St (Re =30000, De =2200, β=8)
图 7 不同De时颗粒平均取向分布(Re =30000, St=1, β=8)
Figure 7. Distribution of particle orientation for different De (Re=30000, St=1, β=8)
图 8 不同Re时颗粒取向分布(De=2200, St=1, β=8)
Figure 8. Distribution of particle orientation for different Re (De=2200, St=1, β=8)
图 9 不同β时颗粒取向分布(Re=30000, De =2200, St=1)
Figure 9. Distribution of particle orientation for different β (Re=30000, De =2200, St=1)
图 10 不同St下的颗粒通过率(De=1862, Re=10500, β=1)
Figure 10. Penetration efficiency of particles at different St (De=1862, Re=10500, β=1)
图 11 不同颗粒长径比时沉积率与St的关系(Re=30000, De=2200)
Figure 11. Relationship between deposition rate and St at different particle aspect ratio (Re=30000, De=2200)
图 12 不同Re下沉积率与St的关系(De=2200, β=8)
Figure 12. Relationship between deposition rate and St at different Re (De =2200, β=8)
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