为研究壁面粗糙度对离心泵空化过程的影响,利用雷诺时均N-S方程和RNG k-ε两方程,采用Zwart空化模型且不考虑水中溶解性气体对空化的影响,应用ANSYS CFX软件对设计流量工况下离心泵全流道气液两相湍流进行定常数值模拟,分析离心泵内部...为研究壁面粗糙度对离心泵空化过程的影响,利用雷诺时均N-S方程和RNG k-ε两方程,采用Zwart空化模型且不考虑水中溶解性气体对空化的影响,应用ANSYS CFX软件对设计流量工况下离心泵全流道气液两相湍流进行定常数值模拟,分析离心泵内部发生空化时,叶片壁面粗糙度对泵的外特性参数和内部流态的影响.计算结果表明:增大粗糙度将导致离心泵扬程、效率降低以及轴功率增大;泵处在临界空化及局部空化状态时,粗糙度对泵性能参数的影响程度大于泵处在空化初生及重空化状态下的影响程度;壁面粗糙度对湍流发展的影响规律与其对空化进程的影响作用具有相似性;当进口压力为81.06 k Pa和101.33 k Pa时,减小壁面粗糙度对改善离心泵性能有更显著的效果.展开更多
A two-fluid particle-wall collision model with consideration of wall roughness is pro- posed.It takes into account the effects of the friction,restitution and in particular the wall roughness, and hence the redistribu...A two-fluid particle-wall collision model with consideration of wall roughness is pro- posed.It takes into account the effects of the friction,restitution and in particular the wall roughness, and hence the redistribution of Reynolds stress in different directions,the absorption of turbulent en- ergy from the mean motion and the attenuation of particle motion by the wall.The proposed model is used to simulate sudden-expansion and swirling gas-particle flows and is validated by comparing with experimental results.The results show that the proposed model gives better results than those obtained by the presently used zero-gradient condition.Hence,it is suggested that the proposed model should be used as the wall boundary condition for the particle phase in place of the presently used boundary condition.展开更多
The present research aims to assess the capability of a comprehensive Euler/Lagrange approach for predicting gas-solid flows and the associated solid particle erosion.The open-source code OpenFOAM®4.1 was used to...The present research aims to assess the capability of a comprehensive Euler/Lagrange approach for predicting gas-solid flows and the associated solid particle erosion.The open-source code OpenFOAM®4.1 was used to carry out the numerical simulations,where the standard Lagrangian libraries were substantially extended to account for all necessary models.Particles are tracked considering both translational and rotational motion as well as all relevant forces,such as gravity/buoyancy,drag and transverse lift due to shear and particle rotation.The tracking time step was dynamically adapted ac-cording to the locally relevant time scales,which drastically reduces computational times.Stochastic approaches are adopted to model particle turbulent dispersion,particle collisions with rough walls and particle-particle interactions.Five solid particle erosion models,available in the literature,were considered to estimate pipe bend erosion.Three study cases are provided to validate the adopted nu-merical approach and erosion models extensively.The first case intends to evaluate the ability of the extended CFD code to predict the behaviour of gas-solid flows in pneumatic conveying systems.This goal is achieved by comparing the numerical results with the experimental data obtained by Huber(1997)and Huber and Sommerfeld(1994,1998)in a pneumatic conveying system.Here,the importance of considering inter-particle collisions and surface roughness for predicting particle velocity,mass flux and mean diameter distributions in gas-solid flows is highlighted.The second and third case intend to evaluate the ability of the erosion models in estimating bend erosion in diluted gas-solid flows.The erosion data obtained experimentally by Mazumder et al.(2008)and Solnordal et al.(2015)in very dilut pneumatic conveying systems is used for validating the numerical results,neglecting now inter-particle collisions and two-way coupling.Besides a comprehensive analysis of the different influential properties on erosion,the innovation of the present stu展开更多
文摘为研究壁面粗糙度对离心泵空化过程的影响,利用雷诺时均N-S方程和RNG k-ε两方程,采用Zwart空化模型且不考虑水中溶解性气体对空化的影响,应用ANSYS CFX软件对设计流量工况下离心泵全流道气液两相湍流进行定常数值模拟,分析离心泵内部发生空化时,叶片壁面粗糙度对泵的外特性参数和内部流态的影响.计算结果表明:增大粗糙度将导致离心泵扬程、效率降低以及轴功率增大;泵处在临界空化及局部空化状态时,粗糙度对泵性能参数的影响程度大于泵处在空化初生及重空化状态下的影响程度;壁面粗糙度对湍流发展的影响规律与其对空化进程的影响作用具有相似性;当进口压力为81.06 k Pa和101.33 k Pa时,减小壁面粗糙度对改善离心泵性能有更显著的效果.
基金The project supported by the Special Funds for the Major State Basic Research,China (G-1999-0222-08)
文摘A two-fluid particle-wall collision model with consideration of wall roughness is pro- posed.It takes into account the effects of the friction,restitution and in particular the wall roughness, and hence the redistribution of Reynolds stress in different directions,the absorption of turbulent en- ergy from the mean motion and the attenuation of particle motion by the wall.The proposed model is used to simulate sudden-expansion and swirling gas-particle flows and is validated by comparing with experimental results.The results show that the proposed model gives better results than those obtained by the presently used zero-gradient condition.Hence,it is suggested that the proposed model should be used as the wall boundary condition for the particle phase in place of the presently used boundary condition.
文摘The present research aims to assess the capability of a comprehensive Euler/Lagrange approach for predicting gas-solid flows and the associated solid particle erosion.The open-source code OpenFOAM®4.1 was used to carry out the numerical simulations,where the standard Lagrangian libraries were substantially extended to account for all necessary models.Particles are tracked considering both translational and rotational motion as well as all relevant forces,such as gravity/buoyancy,drag and transverse lift due to shear and particle rotation.The tracking time step was dynamically adapted ac-cording to the locally relevant time scales,which drastically reduces computational times.Stochastic approaches are adopted to model particle turbulent dispersion,particle collisions with rough walls and particle-particle interactions.Five solid particle erosion models,available in the literature,were considered to estimate pipe bend erosion.Three study cases are provided to validate the adopted nu-merical approach and erosion models extensively.The first case intends to evaluate the ability of the extended CFD code to predict the behaviour of gas-solid flows in pneumatic conveying systems.This goal is achieved by comparing the numerical results with the experimental data obtained by Huber(1997)and Huber and Sommerfeld(1994,1998)in a pneumatic conveying system.Here,the importance of considering inter-particle collisions and surface roughness for predicting particle velocity,mass flux and mean diameter distributions in gas-solid flows is highlighted.The second and third case intend to evaluate the ability of the erosion models in estimating bend erosion in diluted gas-solid flows.The erosion data obtained experimentally by Mazumder et al.(2008)and Solnordal et al.(2015)in very dilut pneumatic conveying systems is used for validating the numerical results,neglecting now inter-particle collisions and two-way coupling.Besides a comprehensive analysis of the different influential properties on erosion,the innovation of the present stu
