基于非均相流模型的离心泵气液两相流动数值研究

Numerical Investigation of Gas-Liquid Two-phase Flow in Centrifugal Pumps Based on Inhomogeneous Model

为研究离心泵气液混输状态下的内部流动特性,基于Eulerian-Eulerian非均相流模型以空气和水作为工作介质,在不同进口含气率工况下对离心泵内流场进行定常和非定常数值计算,相间阻力作用采用Schiller Nauman模型,得到叶轮内气相分布情况以及气液两相的速度流线图,探求气液两相在泵内的流动规律。计算结果表明:在叶片进口边压力面气相浓度较高处,会产生漩涡,说明叶轮流道内漩涡的产生与气体的聚集有很大的关系;增大进口含气率到10%时,叶轮流道内靠近吸力面处已经出现比较明显的相态分离现象,气相有沿着叶片吸力面向叶轮出口运动的趋势;气相在叶轮流道内会沿流道中部向前后盖板运动,随着含气率增大,靠近前后盖板侧的气相浓度逐渐增大,靠近叶轮出口边前盖板侧的气相浓度增加较后盖板更明显,最终气体可能会堵塞流道;在一个旋转周期内,叶轮出口压力呈周期性变化,进口含气率从1%增至10%,叶轮出口压力逐渐降低,监测点在不同含气率下压力脉动主频在叶片通过频率附近,进口含气率不超过10%时对监测点压力脉动的主频及次主频影响不大;通过对比试验结果和数值计算结果,证明所采用的计算模型和方法基本可靠。

In order to study the flow characteristics of centrifugal pumps when transporting the gas-liquid mixture,water and air were chosen as the working medium,numerical simulation was conducted on a centrifugal pump under different conditions of inlet gas volume fraction（ IGVF） based on the EulerianEulerian inhomogeneous model. The drag force was approximated by the Schiller Nauman model. No other interfacial forces were considered. The gas distribution and velocity streamline in the impeller were obtained to discuss the gas and water flow characteristics of the pump. The results showed that gas concentration was high at the inlet pressure side of the blade,where the vortex would exist,indicating that the gas concentration had a great relationship with the vortex aggregation in the impeller passages.When the IGVF was increased to 10%,phase separation had obviously appeared at the suction side of the blades in the impeller passages,and gas had a movement trend along the suction side to the outlet of the impeller. Gas was moved from the center of the passages to the front and back shroud,and with IGVF increased,gas fraction in the back shroud near the leading edge and back shroud would be increase. Gas fraction in the front shroud near the trading edge was increased significantly than that in the back shroud,and the gas may eventually choke the passages. Within a rotation period,the outlet pressure of impeller was cyclically changed,when IGVF was increased from 1% to 10%,the outlet pressure of impeller was gradually decreased, and pressure pulsation frequency of the monitors was near the blade passing frequency at different IGVF values. When the IGVF was not higher than 10%,IGVF had no obvious effects on the pressure pulsation frequency and time frequency of the monitoring points. By comparing theexperimental results with the numerical results,the reliability of the mathematical model and calculation methods was confirmed.