On the performance of a radial pump impeller by varying the outlet blade angle

The systematic research on the influence of the various design aspects of a centrifugal pump in its performance in the whole range of the flow rates requires numerical predictions and experiment. The present ongoing research is concerned with the influence of the outlet blade angle in the performance of a laboratory centrifugal pump fitted in the pump test rig in the Fluid Mechanics Laboratory of the University of Patras.

The design and off-design performance characteristic curves, the local and global variables of the flow field and the resulted non-uniform circumferential pressure field are numerically predicted for three shrouded radial impellers with different outlet blade angle. The computational fluid dynamics analysis is carried out with the commercial software package Fluent which has been widely used in the field of turbomachinery.

The volute of the laboratory centrifugal pump is of rectangular section with rounded corners and its diffuser extends in the radial direction. Three shrouded impellers of constant width (b=20mm) with six untwisted blades backward facing have been designed according to Pfleiderer method. The blade length in the three impellers is almost equal. All impellers have the same diameters in suction and pressure side as well as the same blade’s leading edge angle (β₁=14 deg) and they vary in the blade’s trailing edge angle which is β₂=20, 30 and 50 deg, respectively. The diameters of the impellers at the suction and pressure side are D₁=150mm and D₂=280mm, respectively.

The incompressible flow through the rotating impeller is solved in a moving frame of reference with constant rotational speed equal the rotational speed of the impeller. The flow through the stationary parts of the pump is solved in an inertial reference frame. The turbulence of the flow is modeled with standard k-ε model that is rated as the most used model that combines simplicity, robustness and reasonable accuracy.

Aerodynamics and aeroacoustics of horizontal axis wind turbines

The aerodynamic and aeroacoustic behavior of wind turbines presents spe­cial characteristics which make their prediction a significant research subject. The rotor design is directly influenced by the aerodynamic analysis and the complexity of the rotor flow field. The understanding of the noise source mech­anisms, depending on the rotor aerodynamic parameters and the operating conditions is very important for a wide range of the rotor’s frequency spectrum. Thus, the noise prediction of a wind turbine is a challenging matter similar to other complicated aeroacoustic problems such as helicopter or propeller noise.

CFD simulations in centrifugal pumps

The design of hydraulic turbomachines has reached the stage were improvements can only be achieved through a detailed understanding of the internal flow. The prediction of the flow in such equipment is very complicated due to the rotation and the curved three-dimensional shape of the impellers. Furthermore, the flow in turbomachines shows unsteady behavior, especially at off-design conditions, as a result of interaction between impeller and pump casing. Considering these complexities, computer simulations will become increasingly important. Computational fluid dynamics (CFD) analysis is being increasingly applied in the design of centrifugal pumps. With the aid of the CFD approach, the complex internal flows in water pump impellers, which are not fully understood yet, can be well predicted, to speed up the pump design procedure. Thus, CFD is an important tool for pump designers. The use of CFD tools in turbomachinery industry is quite common today. Many tasks can numerically be solved much faster and cheaper than by means of experiments. Nevertheless the highly unsteady flow in turbomachinery raises the question of the most appropriate method for modeling the rotation of the impeller.