液体射流泵内部流动分析:Ⅰ试验与三维数值模拟

Analysis of flow in liquid jet pump—Part Ⅰ:Experiment and three-dimension numerical simulation

对偏向吸入和水平放置的液体射流泵的基本性能和内部流动分别进行了试验和三维数值模拟.数值模拟采用k-ε双方程湍流模型和SIMPLE算法,数值模拟结果与试验结果在最高效率工况附近基本重合.利用数值模拟结果对射流泵内两股流体的混合过程和流动规律进行了分析,发现对于大流量工况(流量比q>0.8),在喉管入口0.6倍喉管直径长度内,出现由局部损失和摩阻损失引起的当地压力比降低,被吸流体能量损失的现象;随着流量比的增大,单位被吸流体获得能量减少,两股流体传能距离增加,速度混合均匀长度为6～8倍喉管直径,大于喉管内压力比达到峰值的长度;喉管内两股流体混合流动过程与形成充分发展湍流过程类似;对偏向吸入的射流泵,吸入腔体内流动不对称,导致内部截面存在二次流动诱导旋涡,但是喉管内二次流动速度远小于主流速度,因此采用二维理论分析能够反映射流泵性能的主要特征.

The performance of a horizontally installed liquid jet pump with side suction was tested and its internal flow was analyzed by numerical simulation.The standard k-ε two-equation turbulence model and SIMPLE method were adopted in the numerical simulations.The simulated performance parameters agreed well with experimental ones at the best efficiency point.Two-fluid mixing process and its flow pattern in the pump were analyzed as well based on the numerical simulation results.At a large flow ratio（q0.8）,a reduced local pressure ratio and the suctioned liquid with loss of energy are observed in the region from throat inlet to 0.6 times the throat diameter down stream due to mixing and local frictional losses.As the flow ratio increases,the energy obtained by the suction fluid is decreased,thus the distance where an energy transfer takes place between two fluids increases;the two fluids velocity becomes uniform once the suctioned liquid travels in the nozzle for a distance as long as 6-8 times the throat diameter.However,the peak pressure occurs in less than that distance.Such a two liquid mixing process in the throat is similar to that of fully developed turbulent flow.For the side suction jet pump,there are vortexes in the cross-section induced by a secondary flow due to asymmetric flow in the suction chamber,but the velocity of the secondary flow is so smaller than the mainstream velocity in the throat that the major characteristics of the jet pump can be obtained by a two dimensio-nal theoretical analysis.