Based on RNG k-ε turbulence model and sliding grid technique, solid-liquid two-phase three-dimensional(3-D) unsteady turbulence of full passage in slurry pump was simulated by means of Fluent software. The effects of...Based on RNG k-ε turbulence model and sliding grid technique, solid-liquid two-phase three-dimensional(3-D) unsteady turbulence of full passage in slurry pump was simulated by means of Fluent software. The effects of unsteady flow characteristics on solid-liquid two-phase flow and pump performance were researched under design condition. The results show that clocking effect has a significant influence on the flow in pump, and the fluctuation of flow velocity and pressure is obvious, particularly near the volute tongue, at the position of small sections of volute and within diffuser. Clocking effect has a more influence on liquid-phase than on solid-phase, and the wake-jet structure of relative velocity of solid-phase is less obvious than liquid-phase near the volute tongue and the impeller passage outlet. The fluctuation of relative velocity of solid-phase flow is 7.6% smaller than liquid-phase flow at the impeller outlet on circular path. Head and radial forces of the impeller are 8.1% and 85.7% of fluctuation, respectively. The results provide a theoretical basis for further research for turbulence, improving efficient, reducing the hydraulic losses and wear. Finally, field tests were carried out to verify the operation and wear of slurry pump.展开更多
CO_(2)管道输送作为碳捕集、利用和封存(carbon capture,utilization and storage,CCUS)技术中的连接碳源和碳汇的关键环节,未来将在实现碳中和过程中发挥重要作用。对于管道水击工况,其产生的压力震荡可能超过管内承压和低于泵的进站...CO_(2)管道输送作为碳捕集、利用和封存(carbon capture,utilization and storage,CCUS)技术中的连接碳源和碳汇的关键环节,未来将在实现碳中和过程中发挥重要作用。对于管道水击工况,其产生的压力震荡可能超过管内承压和低于泵的进站压力。目前,超临界CO_(2)管道水击及控制理论还不成熟。建立以质量、动量和能量守恒定律为基础的描述管道内一维气体流动的数学模型,采用特征线法进行求解,利用MATLAB编程计算,分别与Kiuchi提出的输气系统模型的模拟结果和商业软件OLGA模拟的结果进行对比分析。结果表明:与输气系统模型的模拟结果大体一致,与OLGA软件计算压力和流量的最大相对误差分别为0.02%和2.32%,满足工程计算精度的要求。对于管道压缩机启停、阀门紧急开关和流量急剧变化等在较短时间内引起管道参数变化的快瞬变过程,通过设置急剧变化值进行模拟,所建立的模型能够计算出各个节点的参数变化情况且精度较高,可为超临界CO_(2)管道输送工艺仿真软件国产化提供理论支持与技术支持。展开更多
The electrical contact and mechanical performances of Ag-SnO_(2) contact materials are often improved by additives,especially Cu and its oxides.To reveal the improvement mechanism of metal additive,the effects of Cu n...The electrical contact and mechanical performances of Ag-SnO_(2) contact materials are often improved by additives,especially Cu and its oxides.To reveal the improvement mechanism of metal additive,the effects of Cu nanoparticles on the interface strength and failure behavior of the Ag-SnO_(2) contact materials are investigated by numerical simulations and experiments.Three-dimensional representative volume element(RVE)models for the Ag-SnO_(2) materials without and with Cu nanoparticles are established,and the cohesive zone model is used to simulate the interface debonding process.The results show that the stress−strain relationships and failure modes predicted by the simulation agree well with the experimental ones.The adhesion strengths of the Ag/SnO_(2) and Ag/Cu interfaces are respectively predicted to be 100 and 450 MPa through the inverse method.It is found that the stress concentration around the SnO_(2) phase is the primary reason for the interface debonding,which leads to the failure of Ag-SnO_(2) contact material.The addition of Cu particles not only improves the interface strength,but also effectively suppresses the initiation and propagation of cracks.The results have an reference value for improving the processability of Ag based contact materials.展开更多
基金Project(51375498)supported by the National Natural Science Foundation of China
文摘Based on RNG k-ε turbulence model and sliding grid technique, solid-liquid two-phase three-dimensional(3-D) unsteady turbulence of full passage in slurry pump was simulated by means of Fluent software. The effects of unsteady flow characteristics on solid-liquid two-phase flow and pump performance were researched under design condition. The results show that clocking effect has a significant influence on the flow in pump, and the fluctuation of flow velocity and pressure is obvious, particularly near the volute tongue, at the position of small sections of volute and within diffuser. Clocking effect has a more influence on liquid-phase than on solid-phase, and the wake-jet structure of relative velocity of solid-phase is less obvious than liquid-phase near the volute tongue and the impeller passage outlet. The fluctuation of relative velocity of solid-phase flow is 7.6% smaller than liquid-phase flow at the impeller outlet on circular path. Head and radial forces of the impeller are 8.1% and 85.7% of fluctuation, respectively. The results provide a theoretical basis for further research for turbulence, improving efficient, reducing the hydraulic losses and wear. Finally, field tests were carried out to verify the operation and wear of slurry pump.
文摘CO_(2)管道输送作为碳捕集、利用和封存(carbon capture,utilization and storage,CCUS)技术中的连接碳源和碳汇的关键环节,未来将在实现碳中和过程中发挥重要作用。对于管道水击工况,其产生的压力震荡可能超过管内承压和低于泵的进站压力。目前,超临界CO_(2)管道水击及控制理论还不成熟。建立以质量、动量和能量守恒定律为基础的描述管道内一维气体流动的数学模型,采用特征线法进行求解,利用MATLAB编程计算,分别与Kiuchi提出的输气系统模型的模拟结果和商业软件OLGA模拟的结果进行对比分析。结果表明:与输气系统模型的模拟结果大体一致,与OLGA软件计算压力和流量的最大相对误差分别为0.02%和2.32%,满足工程计算精度的要求。对于管道压缩机启停、阀门紧急开关和流量急剧变化等在较短时间内引起管道参数变化的快瞬变过程,通过设置急剧变化值进行模拟,所建立的模型能够计算出各个节点的参数变化情况且精度较高,可为超临界CO_(2)管道输送工艺仿真软件国产化提供理论支持与技术支持。
基金Projects(11872257,11572358)supported by the National Natural Science Foundation of ChinaProject(ZD2018075)supported by the Hebei Provincial Education Department,China。
文摘The electrical contact and mechanical performances of Ag-SnO_(2) contact materials are often improved by additives,especially Cu and its oxides.To reveal the improvement mechanism of metal additive,the effects of Cu nanoparticles on the interface strength and failure behavior of the Ag-SnO_(2) contact materials are investigated by numerical simulations and experiments.Three-dimensional representative volume element(RVE)models for the Ag-SnO_(2) materials without and with Cu nanoparticles are established,and the cohesive zone model is used to simulate the interface debonding process.The results show that the stress−strain relationships and failure modes predicted by the simulation agree well with the experimental ones.The adhesion strengths of the Ag/SnO_(2) and Ag/Cu interfaces are respectively predicted to be 100 and 450 MPa through the inverse method.It is found that the stress concentration around the SnO_(2) phase is the primary reason for the interface debonding,which leads to the failure of Ag-SnO_(2) contact material.The addition of Cu particles not only improves the interface strength,but also effectively suppresses the initiation and propagation of cracks.The results have an reference value for improving the processability of Ag based contact materials.
