Experimental and Numerical Investigation for Predicting the Performance of Voluteless Centrifugal Fan Rotors

A better understanding of the flow field is crucial for improving the design of a turbomachine. In this work we investigate the performance of voluteless centrifugal fan rotors. The study includes two parts: experiments and numerical simulations through Computational Fluid Dynamics (CFD) techniques. Our test system allows the analysis of the flow behavior of centrifugal fan rotors maintaining the meridional shape without making substantial changes to their internal structure, but with different blade shapes, sizes, and blade numbers. To avoids irregular interference with the rotor flow from external components such as the collector a radial channel composed by two parallel discs was placed concentrically on the rotor axis at its outer periphery with special interest in measuring flow characteristics at the rotor outlet with a reliable accuracy. As an application case a typical centrifugal fan rotor with ten blades of single curvature in the circular arc shape has been investigated. Two types of measuring systems were used: one, with an aerodynamic probe located in the centrifugal rotor outlet and, the other, with a load cell for measuring the rotor shaft power. A comparison of the results by these two measuring arrangements shows some important characteristics, such as the phenomenon of the flow recirculation within the rotor. The experimental performance curves related to non-dimensional flow such as the slip factor, and pressure coefficient, revealed good matching with numerical simulations, highlighting the remarkable reliability of our experimental setup.