基于DSMC-CFD方法的气固两相流冲蚀预测研究

Erosion Prediction of Gas-Solid Flow Based on DSMC-CFD Method

目的研究气固两相流中固体颗粒间碰撞对冲蚀的影响。方法使用Eulerian-Lagrangian方法,将气相作为连续相,通过Navier-Stokes方程求解,颗粒平移运动由离散相模型(DPM)求解。颗粒间碰撞运动采用直接模拟蒙特卡罗(DSMC)方法进行模拟,用少量采样颗粒代替真实颗粒计算颗粒间碰撞,碰撞的发生条件通过修正的Nanbu方法判定,碰撞过程遵循颗粒间碰撞动力学模型,采用Grant-Tabakoff随机颗粒-壁面碰撞反弹模型,计算颗粒与壁面的碰撞运动。将颗粒运动信息导入5种不同的冲蚀模型,并将计算与未计算颗粒间碰撞的冲蚀预测模拟结果与实验数据进行对比。结果颗粒间碰撞位置主要分布在90°弯头外拱侧的颗粒高浓度区,随着颗粒质量流量的增大,颗粒碰撞次数增加,且直管段中碰撞次数占比增大。随着入口速度的增大,颗粒碰撞次数减少。使用DSMC-CFD方法计算的最大冲蚀位置沿弯管外拱轴线向高角度方向偏移,且数值比忽略颗粒间碰撞的CFD方法约低5%~15%,总冲蚀率则两者区别不大。结论引入DSMC方法计算颗粒间的碰撞,可以节省大量算力。弯管处发生颗粒间碰撞,DSMC-CFD冲蚀预测方法更符合实际,使用DSMC-CFD方法的Oka模型与实验测得值最贴近。

The work aims to study the effect of solid particle collision on erosion in gas-solid flow.Eulerian-Lagrangian method was used to solve the gas phase as a continuous phase by Navier Stokes equation,while the particle motion was solved by discrete phase model(DPM).The direct simulation Monte Carlo(DSMC)method was used to calculate the collision between particles.A small number of sampled particles were used to replace the real particles to calculate the collision between particles.The collision conditions were determined by the modified Nanbu method.The collision process followed the dynamic model of the collision between particles.The Grant-Tabakoff model for particles-wall collision rebound was used to calculate the collision motion between particles and wall.The particle motion information was introduced into five different erosion models,and the erosion prediction results of whether to calculate the collision between particles were compared with the experimental data.The location of particle to particle collision was mainly in the high concentration area of particles on the outer arch side of 90°elbow.With the increase of particle mass flow rate,the number of particle collisions increased,and the proportion of collision times in straight pipe section increased.With the increase of inlet velocity,the number of particle collisions decreased.The maximum erosion position calculated by DSMC-CFD method was shifted to the high angle direction along the outer arch axis of the elbow,and the numerical value was about 5%~15%lower than that of CFD method,which ignored the collision between particles.The total erosion rate by two methods had no large difference.Therefore,the calculation of particle collision by DSMC method can save a lot of effort.DSMC-CFD erosion prediction method is more practical for the particle corrosion at the elbow,and the results of Oka model using DSMC-CFD method are the closest to the experimental data.