M. Mahdi - Energy Conversion Department, School of Mechanical Engineering, Shahid Rajaee Teacher Training University, Tehran, Tehran, ۱۶۷۸۸۱۵۸۱۱, Iran
M. Rasekh - Energy Conversion Department, School of Mechanical Engineering, Shahid Rajaee Teacher Training University, Tehran, Tehran, ۱۶۷۸۸۱۵۸۱۱, Iran
V. Sajadi - Energy Conversion Department, School of Mechanical Engineering, Shahid Rajaee Teacher Training University, Tehran, Tehran, ۱۶۷۸۸۱۵۸۱۱, Iran

In the present work, the effects of modifying the tongue geometry of a centrifugal pump on pressure pulsations under the design and off-design conditions are carried out numerically by the unsteady analysis of fluid flow. Numerical modeling based on the Re-Normalization Group (RNG) k-ε turbulence model using a Mosaic mesh structure, a technology which can easily, quickly and formally connects any type of mesh for complex geometries and flow regimes, is applied to simulate the flow within the modeled pump, which is validated with the available experimental results. The flow is simulated through a commercial Computational Fluid Dynamics (CFD) software that solved Reynolds-Averaged Navier-Stokes (RANS) equations for a three-dimensional unsteady flow. In addition to choosing Qd (the design flow rate), ۰.۴ Qd and ۱.۲Qd  are also taken into account as the inlet flow rates. Besides, pressures of ۱۰۱KPa and ۱۳KPa are considered as additional inlet conditions for this investigation. This unsteady simulation employing different inlet conditions is used to investigate the impacts of various volute tongue angles on the pressure coefficient (cp ). Results indicate that, overall, by changing the angle from ۴۰° to ۸۵°, the value of the pressure coefficient at the pump outlet grows by about ۱۰% where it also causes a rise in the amplitude of pressure fluctuations. By the same token, a decrement to the inlet flow rate up to ۴۰% of the nominal value brings about the amplitude of pressure fluctuations at the pump outlet to be increased significantly.

Unsteady flow simulation, Centrifugal pump model, Off-design conditions, Computational fluid dynamics (CFD), Pressure fluctuations