Numerical Investigation on Bubble Distribution of a Multistage Centrifugal Pump Based on a Population Balance Model

Abstract

This work aimed to study the bubble distribution in a multiphase pump. A Euler-Euler inhomogeneous two-phase flow model coupled with a discrete particle population balance model (PBM) was used to simulate the whole flow channel of a three-stage gas-liquid two-phase centrifugal pump. Comparison of the computational fluid dynamic (CFD) simulation results with experimental data shows that the model can accurately predict the performance of the pump under various operating conditions. In addition, the liquid phase velocity distribution, gas-phase distribution, and pressure distribution of the second stage impeller at a 0.5 span of blade height under three typical working conditions were compared. Results show that the region with high local gas volume fraction (LGVF) mainly appears on the suction surface (SS) of the blade. With the increase in inlet gas volume fraction (IGVF), vortices and low velocity recirculation regions are generated at the impeller outlet and SS of the blade, the area with high LGVF increases, and gas–liquid separation occurs at the SS of the blade. The liquid phase flows out of the impeller at high velocity along the pressure surface of the blade, and the limited pressurization of fluid mainly happens at the impeller outlet. The average bubble size at the impeller outlet is the smallest while that at the impeller inlet is the largest. Under low IGVF conditions, bubbles tend to break into smaller ones, and the broken bubbles mainly concentrate at the blade pressure surface (PS) and the impeller outlet. Bubbles tend to coalesce into larger ones under high IGVF conditions. With the increase in IGVF, the bubble aggregation zone diffuses from the blade SS to the PS.

Numerical Simulation of Gas–Liquid Two-Phase Flow Characteristics of Centrifugal Pump Based on the CFD–PBM

“…Assuming m 0 = 1, m 1 = 10 −4 (m), m 2 = 10 −8 (m 2 ), m 3 = 10 −12 (m 3 ) and the initial minimum diameter as 0.1 mm the maximum diameter for the bubbles to grow is 3 mm. The minimum and maximum diameter can be accurately selected according to pump parameters [25,26]. The initial diameter distribution at the inlet is shown in Figure 1.…”

“…However, the research of this study still focuses on the GVF and velocity streamline distribution without corresponding to bubbles diameter. Recently, Yan [26] used the PBM to investigate bubble distribution in a multistage centrifugal pump, which suggested that the PBM can predict hydraulic performance precisely and show bubble distribution well.…”

Analysis of Fluid-Structure Coupling Vibration Characteristics of Pipeline Transporting Bubbly Fluid Medium: With Application to Luxury Passenger Ship Life Area Pipeline

“…Also, it was widely used in the chemistry feld to describe the fow characteristics such as fuidized beds and bubbling towers [30,31]. In addition, in the feld of hydraulic machinery, the PBM model was also applied to the simulation of cavitation in the fow channel of the water pump, which provided a reference for the structure of the water pump [32,33]. Te above examples show that the PBM model can simulate the fow characteristics of the bubbly fuid, and its simulation accuracy can meet the requirements of mechanical structure design optimization.…”

CFD–PBM Simulation of Liquid–Liquid Dispersions in a Pump-Mixer

“…Most of the applications of the CFD–PBM approach were to reveal detailed spatial and temporal information inside bubble columns, ,− and now more and more research works are being performed to study the multiphase flow characteristics in the rotational machinery, for example, centrifugal pumps − and stirring tanks. − ,, For the CFD–PBM approach, the key is to find reliable and accurate breakup and coalescence kernels for population balance modeling. However, there are significant distinctions in the form and predictive ability of various kernels in the literature, − which make it hard to be adopted directly by different researchers.…”