Experimental and Numerical Studies on Flow Characteristics of Centrifugal Pump under Air-water Inflow

Abstract

A two-phase liquid pumping test ring is built to study the flow induced characteristics of centrifugal pump under the air-water flow working condition. Pump performances are measured under different flow rates and different inlet air void fraction (a). Pressure pulsation signal spectrums and their probability density maps are also recorded. The calculations, using URANS k-epsilon turbulence model combined with the Euler-Euler inhomogeneous two-phase model, are also performed to obtain inner flow structure inside the impeller and volute channels under different air-water conditions in order to understand the pump characteristic evolutions. The results show that the performance of centrifugal pump is more sensitive to air inlet injection at low flow rates. The maximum air void fraction of model pump could reach 10% when the pump operates at the highest efficiency point, and the performance drops sharply when the air void fraction is more than 8%. The dominant frequency of pump outlet pressure pulsation is still at the blade passing frequency even under two-phase condition. Frequency amplitude increases with the increase of a. The greater the a, the more low frequency appears in broadband characteristics. With the increase of a, the probability density amplitude of pressure pulsation decreases gradually, and its span becomes gradually wider as well. Comparisons between numerical local results, experimental unsteady pressure can explain part of the phenomena that are found in the present paper.

A Comparative Study on Centrifugal Pump Designs and Two-Phase Flow Characteristic under Inlet Gas Entrainment Conditions

“…In particular when α0 is 7%, the air-water separation phenomenon is more obvious, but the air-water coexistence is dominant. The flow field distributions of pump 1 and pump 2 are similar, and some results of pump 1 have been reported before [15,16]. Moreover, pump 2 already shows better handing ability for air entrainment, so the follow-up analysis is mainly based on the flow field information of pump 2 then.…”

“…The general Equation (16) is used to calculate the turbulent kinetic energy. It is a physical quantity commonly used to describe the loss of the viscosity of the fluid and the extent of the The flow field distributions of pump 1 and pump 2 are similar, and some results of pump 1 have been reported before [15,16]. Moreover, pump 2 already shows better handing ability for air entrainment, so the follow-up analysis is mainly based on the flow field information of pump 2 then.…”

“…Both pumps are single stage coupled systems with a spiral volute and shroud type impeller. Pump 1 has been already investigated by our research team, and the results can be found in several publications by Si et al [15,16,27]. The meridional shapes of each pump impeller are given in Figure 1.…”

“…Due to the complex geometries, the experimental visualization to the internal flow behavior and bubble movement of centrifugal pumps is very difficult. Si et al [15,16] experimentally studied the overall performance and pressure pulsation characteristics of a centrifugal pumps under inlet air-water two phase flow conditions. It was revealed that the dominant frequency of the pressure pulsation located at the pump outlet is still the blade passing frequency, even with air entrainment.…”

Experimental Investigations on the Inner Flow Behavior of Centrifugal Pumps under Inlet Air-Water Two-Phase Conditions

“…An open-type test loop was built to assess the pump performance and inner flow visualization measurement. As shown in Figure 1, the air injection system was able to provide 0.2 mm diameter bubbles using a specific compressor device (more details can be found in Si et al [19,20]. The dehydrated air flow rate was measured and controlled by micro-electro-mechanical flow sensors systems (Bürkert 8107), which could supply a constant air mass flow rate in standard conditions value (25 • C, 101,325 Pa).…”