为了探究折叶片旋流泵固液两相输送机理,基于CFD-DEM(Computational fluid dynamics-discrete element method)耦合算法,选用油菜籽和黄豆颗粒等比例混合,在不同流量工况和体积分数下对旋流泵进行固液两相流数值模拟和试验研究。同时也...为了探究折叶片旋流泵固液两相输送机理,基于CFD-DEM(Computational fluid dynamics-discrete element method)耦合算法,选用油菜籽和黄豆颗粒等比例混合,在不同流量工况和体积分数下对旋流泵进行固液两相流数值模拟和试验研究。同时也研究了折叶片旋流泵内部流动规律及颗粒分布特征。小流量工况下,进口管内螺旋回流长度较长,对进口来流扰动较大。随着流量增大,进口管回流长度逐渐缩短。叶轮前端面旋涡随流量增大,数量先增加后减少,且逐渐向折点方向聚拢。泵内颗粒受循环流和贯通流的共同作用,进口管中心部颗粒主要受贯通流影响,直接穿过无叶腔,冲击叶轮进口;靠近管壁的颗粒受循环流影响较大。无叶腔内颗粒分布呈现出:中心部最高,中间部随外径增大浓度逐渐降低,外缘部浓度稍有上升。叶轮前半部颗粒数量明显少于叶轮后半部,颗粒沿叶片第1段折边运动,在折点处开始发生分离,不再跟随第2段折边。不同工况下,泵进口有不同程度的螺旋回流现象,导致进口过流面积减小。循环流的存在,使得无叶腔和进口管的颗粒充分旋起,泵送能力增强,不易发生堵塞。展开更多
【目的】探究旋流式固液两相流泵内流动特征。【方法】基于CFD-DEM(Computational Fluid Dynamics-Discrete Element Method)耦合模型,选用油菜籽颗粒,在不同流量工况和颗粒体积分数下对旋流泵固液两相流场进行数值模拟和试验研究,研究...【目的】探究旋流式固液两相流泵内流动特征。【方法】基于CFD-DEM(Computational Fluid Dynamics-Discrete Element Method)耦合模型,选用油菜籽颗粒,在不同流量工况和颗粒体积分数下对旋流泵固液两相流场进行数值模拟和试验研究,研究旋流式固液两相流泵的内部流动规律及颗粒分布特征。【结果】小流量工况下循环流漩涡特征较明显,进口旋转回流长度较长,对进口来流扰动较大,随着流量增大,循环流影响范围减小;泵内颗粒受到贯通流和循环流的共同作用。管壁中心颗粒受贯通流的影响较大,颗粒穿过无叶腔直接进入叶轮,而靠近管壁的颗粒受循环流的影响较大;叶轮内沿着轴向3个截面处颗粒分布有着较为明显的差异,从叶轮前端面到后盖板,颗粒数量逐渐增多;蜗室内存在一对旋转方向相反的漩涡,在第Ⅴ断面之后前侧涡束逐渐消散,后侧涡束一直旋转至第Ⅷ断面处;在贯通流和循环流的作用下,油菜籽颗粒被旋转回流沿着管壁面带入到进口区域。【结论】循环流的存在导致旋流泵效率较低,但在输送颗粒时循环流起到较大的作用,使得泵输送性能较强;模型泵数值模拟与试验结果基本一致,验证了模拟的可靠性。展开更多
Cavitation is one of the most important performance of centrifugal pumps. However, the current optimization works of centrifugal pump are mostly focusing on hydraulic efficiency only, which may result in poor cavitati...Cavitation is one of the most important performance of centrifugal pumps. However, the current optimization works of centrifugal pump are mostly focusing on hydraulic efficiency only, which may result in poor cavitation performance. Therefore, it is necessary to find an appropriate solution to improve cavitation performance with acceptable efficiency. In this paper, to improve the cavitation performance of a centrifugal pump with a vaned diffuser, the influence of impeller geometric parameters on the cavitation of the pump is investigated using the orthogonal design of experiment （DOE） based on computational fluid dynamics. The impeller inlet diameter D1, inlet incidence angle Aft, and blade wrap angle ~0 are selected as the main impeller geometric parameters and the orthogonal experiment of L9（3＂3） is performed. Three-dimensional steady simulations for cavitation are conducted by using constant gas mass fraction model with second-order upwind, and the predicated cavitation performance is validated by laboratory experiment. The optimization results are obtained by the range analysis method to improve cavitation performance without obvious decreasing the efficiency of the centrifugal pump. The internal flow of the pump is analyzed in order to identify the flow behavior that can affect cavitation performance. The results show that D1 has the greatest influence on the pump cavitation and the final optimized impeller provides better flow distribution at blade leading edge. The final optimized impeller accomplishes better cavitation and hydraulic performance and the NPSHR decreases by 0.63m compared with the original one. The presented work supplies a feasible route in engineering practice to optimize a centrifugal pump impeller for better cavitation performance.展开更多
文摘为了探究折叶片旋流泵固液两相输送机理,基于CFD-DEM(Computational fluid dynamics-discrete element method)耦合算法,选用油菜籽和黄豆颗粒等比例混合,在不同流量工况和体积分数下对旋流泵进行固液两相流数值模拟和试验研究。同时也研究了折叶片旋流泵内部流动规律及颗粒分布特征。小流量工况下,进口管内螺旋回流长度较长,对进口来流扰动较大。随着流量增大,进口管回流长度逐渐缩短。叶轮前端面旋涡随流量增大,数量先增加后减少,且逐渐向折点方向聚拢。泵内颗粒受循环流和贯通流的共同作用,进口管中心部颗粒主要受贯通流影响,直接穿过无叶腔,冲击叶轮进口;靠近管壁的颗粒受循环流影响较大。无叶腔内颗粒分布呈现出:中心部最高,中间部随外径增大浓度逐渐降低,外缘部浓度稍有上升。叶轮前半部颗粒数量明显少于叶轮后半部,颗粒沿叶片第1段折边运动,在折点处开始发生分离,不再跟随第2段折边。不同工况下,泵进口有不同程度的螺旋回流现象,导致进口过流面积减小。循环流的存在,使得无叶腔和进口管的颗粒充分旋起,泵送能力增强,不易发生堵塞。
文摘【目的】探究旋流式固液两相流泵内流动特征。【方法】基于CFD-DEM(Computational Fluid Dynamics-Discrete Element Method)耦合模型,选用油菜籽颗粒,在不同流量工况和颗粒体积分数下对旋流泵固液两相流场进行数值模拟和试验研究,研究旋流式固液两相流泵的内部流动规律及颗粒分布特征。【结果】小流量工况下循环流漩涡特征较明显,进口旋转回流长度较长,对进口来流扰动较大,随着流量增大,循环流影响范围减小;泵内颗粒受到贯通流和循环流的共同作用。管壁中心颗粒受贯通流的影响较大,颗粒穿过无叶腔直接进入叶轮,而靠近管壁的颗粒受循环流的影响较大;叶轮内沿着轴向3个截面处颗粒分布有着较为明显的差异,从叶轮前端面到后盖板,颗粒数量逐渐增多;蜗室内存在一对旋转方向相反的漩涡,在第Ⅴ断面之后前侧涡束逐渐消散,后侧涡束一直旋转至第Ⅷ断面处;在贯通流和循环流的作用下,油菜籽颗粒被旋转回流沿着管壁面带入到进口区域。【结论】循环流的存在导致旋流泵效率较低,但在输送颗粒时循环流起到较大的作用,使得泵输送性能较强;模型泵数值模拟与试验结果基本一致,验证了模拟的可靠性。
基金Supported by National Science&Technology Pillar Program of China(Grant No.2014BAB08B01)National Natural Science Foundation of China(Grant No.51409123)+1 种基金Jiangsu Provincial Natural Science Foundation of China(Grant No.BK20140554)Training Project for Young Core Teacher of Jiangsu University,China
文摘Cavitation is one of the most important performance of centrifugal pumps. However, the current optimization works of centrifugal pump are mostly focusing on hydraulic efficiency only, which may result in poor cavitation performance. Therefore, it is necessary to find an appropriate solution to improve cavitation performance with acceptable efficiency. In this paper, to improve the cavitation performance of a centrifugal pump with a vaned diffuser, the influence of impeller geometric parameters on the cavitation of the pump is investigated using the orthogonal design of experiment （DOE） based on computational fluid dynamics. The impeller inlet diameter D1, inlet incidence angle Aft, and blade wrap angle ~0 are selected as the main impeller geometric parameters and the orthogonal experiment of L9（3＂3） is performed. Three-dimensional steady simulations for cavitation are conducted by using constant gas mass fraction model with second-order upwind, and the predicated cavitation performance is validated by laboratory experiment. The optimization results are obtained by the range analysis method to improve cavitation performance without obvious decreasing the efficiency of the centrifugal pump. The internal flow of the pump is analyzed in order to identify the flow behavior that can affect cavitation performance. The results show that D1 has the greatest influence on the pump cavitation and the final optimized impeller provides better flow distribution at blade leading edge. The final optimized impeller accomplishes better cavitation and hydraulic performance and the NPSHR decreases by 0.63m compared with the original one. The presented work supplies a feasible route in engineering practice to optimize a centrifugal pump impeller for better cavitation performance.
