Numerical investigation of internal flow characteristics in a mixed-flow pump with eccentric impeller
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(2020) 42:458
TECHNICAL PAPER
Numerical investigation of internal flow characteristics in a mixed‑flow pump with eccentric impeller Wei Li1,2 · Leilei Ji1 · Weidong Shi3 · Ling Zhou1 · Ramesh Agarwal4 · Elemam Mahmouda1 Received: 3 April 2020 / Accepted: 28 July 2020 © The Brazilian Society of Mechanical Sciences and Engineering 2020
Abstract In order to study the internal flow fields of mixed-flow pump with eccentric impeller, the numerical simulation and experiment have been conducted based on the dynamic sliding multi-region method. During simulation, the impeller domain has been separated by three sub-domains to apply the whirl effect. The pressure, turbulent kinetic dissipation and streamline distribution in the tip clearance were analyzed. The results show that the energy performance of calculation is basically consistent with the experimental results, which indicates the accuracy of energy performance prediction. The efficiency and head at the design flow condition drop about 20% and 11%, respectively, when e = 0.5 mm. The circumferential pressure distribution of impeller inlet and outlet is influenced greatly by the eccentric impeller, but the middle part of impeller suffered little effects as a result of the rotation effect of impeller. When the impeller is eccentric, the tip leakage flow and tip leakage vortex (TLV) are restrained at small tip clearance but enhance at large tip clearance. The angle between the TLV core and blade rim also increases at large tip clearance but decreases at small tip clearance. More energy has dissipated in the first half part of impeller channel within tip region, and the impacting depth increases with the increase in eccentricity, which affect the inlet flow fields of impeller at large eccentricity. The turbulent kinetic dissipation and hydraulic losses increase with the increase in eccentricity, which is the main factor for the decrease in pump efficiency. Keywords Mixed-flow pump · Eccentricity · Dynamic sliding multi-region (DSMR) · Tip leakage flow
1 Introduction The Alford effect was firstly noticed by Alford [1] in the field of axial flow gas turbine. When the impeller rotates with eccentricity, the blade tip clearance is unevenly distributed in the circumferential direction that increases the blade loading and generating a perpendicular force on the impeller [2]. Technical Editor: Daniel Onofre de Almeida Cruz. * Wei Li [email protected] 1
National Research Center of Pumps, Jiangsu University, Zhenjiang, People’s Republic of China
2
Institute of Fluid Engineering Equipment, JITRI, Zhenjiang 212009, Jiangsu, People’s Republic of China
3
College of Mechanical Engineering, Nantong University, Nantong 226019, People’s Republic of China
4
Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, MO 63130, USA
Some literature also focuses on the measurement of Alford’s force, e.g., Vance [3], Urlichs [4] and Laudadio [5]. Due to the rotor whirl and self-vibrations of impeller, the end shell is more l
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