Analysis of the Effect of Various Impeller Blade Angles on Characteristic of the Axial Pump with Pressure Fluctuations B
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RESEARCH PAPER
Analysis of the Effect of Various Impeller Blade Angles on Characteristic of the Axial Pump with Pressure Fluctuations Based on Time‑ and Frequency‑Domain Investigations Ahmed Ramadhan Al‑Obaidi1 Received: 20 October 2018 / Accepted: 18 September 2020 © Shiraz University 2020
Abstract In this work, the behaviors of flow field and pressure fluctuations in both time and frequency domains in an axial flow pump through changing various impeller blade angles are studied and investigated by using a CFD technique. The blade angles are changed between 30°, 45º, 60º and 75º. Numerical results are validated with the experimental values, as a good agreement was found between them. The developed flow analysis shows that the blade angle does influence the different flow behaviors and features, such as the static pressure, turbulent kinetic energy (TKE), pressure fluctuations, axial velocity, radial velocity and tangential velocity. The results have revealed that the TKE rises with flow rate decreases and high static pressure increases at the pump outlet region near the tip blade region. Another conclusion of the study is the fact that the blade angle with 60º is the better one in terms of lower-negative-pressure regions, when compared with the other settings. The first dominated frequency was pump rotational frequency, and the second important frequency is the BPF (blade passing frequency). Furthermore, the results showed that impeller blade angles and unsteady flow have a high influence on the pressure fluctuation amplitude. Moreover, the results of the presented numerical simulation would be useful for a future hydraulic design of an axial pump. Keywords Axial flow pump · Impeller blade angle · Pressure fluctuation · Time and frequency domains List of Symbols CFD Computational fluid dynamics 3D Three-dimensional Q Flow rate TKE Turbulent kinetic energy P Pressure n Number of element N Total number of element u, v and w Velocities in x, y and z t Time 𝜏 Shear stress ρ Density μ Kinematic viscosity θ Angle
* Ahmed Ramadhan Al‑Obaidi [email protected] 1
Department of Mechanical Engineering, College of Engineering, Mustansiriyah University, Baghdad, Iraq
1 Introduction There are different kinds of liquid moving machines, which convert fluid energy through transfer fluid energy to mechanical energy or transfer mechanical to fluid energy; these types are named as pumps. Also, they are generally used to lift the fluid from point to point or from a low level to a high level. Mostly can be classified pumps into two main groups. The first one is rotodynamic pumps, and the second important category is positive displacement pumps (Al-Obaidi 2018; Nelik 1999; Girdhar and Moniz 2011; Karassik 1998). The axial machine can be characterized through a relatively complex process starting from meridional section design to aerodynamic profile applications into the impeller blade cascade of the axial flow pump. The numerical simulation procedures to a three-dimensional environment have a high sig
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