Abstract:

The vortex pump, a common type of centrifugal pump, finds wide application in the chemical industry. In chemical reaction processes, the pumped fluid often exhibits two-phase flow conditions, such as bubbly inflow. Understanding the evolution mechanism of the flow field in vortex pumps under bubbly inflow conditions is crucial for optimizing their structure and improving gas-liquid transportation performance. This study aims to investigate the gas-liquid two-phase flow field of a vortex pump under four different inlet gas volume fractions (IGVF) (1%, 5%, 10% and 15%) and three liquid flow rates (96, 120 and 144 m³/h), by coupling the mixture multiphase model and the population balance model. The energy gradient theory, entropy generation analysis, and flow field evolution law are used to reveal the energy conversion characteristics of the vortex pump under bubbly inflow conditions. The results indicate that in the vaneless chamber, the circulating flow takes the form of a vortex strip, with intensified circulation near the volute. The vortex strip distribution is wide-ranging and exhibits a stable structure. However, the strength of the circulating flow in the smaller radius section of the vaneless chamber is weak and only present in part of the flow channels. With an increase in IGVF, the vortex area in the vaneless chamber progressively expands, along with an increase in the number of vortex nuclei. However, when the IGVF increases to 10% and the gas content continues to increase, the number of circulating flows does not change significantly. At higher IGVF, gas accumulates at the impeller channel, resulting in an augmented energy gradient at the outer edge of the recessed chamber and vaneless chamber, as well as an increase in pulsation entropy production loss. This condition also leads to a more turbulent flow field. Consequently, the pressure increment and efficiency of the vortex pump decrease rapidly under high IGVF.

Key words: vortex pump, gas-liquid flow, bubble, population balance, energy conversion

摘要：

探究泡状入流条件下旋流泵流场演化机理和能量转换特性，对优化旋流泵结构和提升其气液混输性能具有重要意义。采用混合多相流模型与种群平衡模型进行耦合计算了旋流泵气液两相流场，结合能量梯度理论、熵产分析与流场演化规律，获得了泡状入流条件下旋流泵的能量转换特性。结果表明，循环流在无叶腔内呈涡带分布，其中涡室附近的循环流强度较高，涡带分布范围广且结构稳定，而无叶腔小半径处的循环流涡带强度较弱，仅存在于部分流道。随着入口体积含气率的增加，无叶腔内涡团面积逐渐增大，涡核数量有所增加。但当入口体积含气率增加到10%后，继续提高含气率，则循环流数量没有明显变化。在高入口体积含气率下，气相在后缩腔叶轮内聚集，使得后缩腔与无叶腔外缘能量梯度函数值增大，脉动熵产损失提高，流场更加紊乱，旋流泵效率与压差下降。

关键词: 旋流泵, 气液两相流, 气泡, 种群平衡, 能量转换