基于量纲一化的离心泵内部气液两相流动特性

为研究气液混输状态下离心泵内部流动及外特性的基本规律,以某一比转数n_s=132.2的直联式单级单吸离心泵为研究对象,基于量纲一化方法,在不同含气率及转速下进行外特性试验和数值模拟研究.结果表明:量纲一化参数的压力系数和速度系数能够较为直观地反映离心泵气液两相流内部流动的基本规律;随着转速的增大,低压区在叶轮进口附近的半径逐渐增大,低速区占据流道的面积也逐渐增大,此时由于气体主要聚集在叶轮流道及蜗壳附近,容易堵塞流道,液相与叶轮能量得不到有效地交换与传递,这是导致气液混输状态下含气率大于3%时离心泵外特性曲线不再遵循相似定律的主要原因;结合试验和数值模拟结果验证了所采用的Eulerian-Eulerian非均相流模型的合理性,为泵的优化设计提供了一定理论基础.

Characteristics of gas-liquid two-phase flow in centrifugal pump based on dimensionless method

In order to study the basic law of the internal flow and external characteristics of the centri-fugal pump under the condition of gas-liquid mixed transportation. The direct-coupled single-stage and single-suction centrifugal pump with a specific speed of n_s=132.2 was selected. Based on the dimensionless analysis method, the external characteristics tests and numerical simulation under the condition of different rotational speeds and different inlet gas volume fractions were carried out. The results show that the dimensionless parameters of pressure coefficient and velocity coefficient can directly reflect the basic internal flow of gas-liquid two-phase flow in centrifugal pump. With the increase of the rotating speed, the radius of the low-pressure area around the impeller inlet increases gradually, and the area of the low velocity occupying the flow passage also increases gradually. At this time, the gas mainly concentrated near the impeller flow passage and the volute, which is easy to block the flow passage, and the energy between the liquid phase and the impeller cannot be effectively exchanged and transferred, which is the main reason that the external centrifugal pump characteristics curve no longer follows the similarity law when the inlet gas volume fraction is more than 3% at the condition of gas-liquid mixed transportation. Combined with the experimental and numerical simulation results, the rationality of the Eulerian-Eulerian inhomogeneous model is verified, which provides a theoretical basis for the optimal design of the pump.