Investigation of a Diffuser-Volute Combination With Variable Cross-Sectional Area for Centrifugal Fans

The present paper focuses on the potential efficiency improvements and the stable operating range of a centrifugal fan for fuel cell applications. Improvements will be achieved by variability of the cross-sectional area of diffuser and volute by use of a moving backplate. The investigation consists of three parts: The first part describes the design and the performance prediction of a diffuser-volute combination with a variable cross-sectional area, based on empirical correlations and low-resolution CFD (Computational Fluid Dynamics) simulations. For the second part, high-resolution 360 degree CFD simulations are used to gain deeper insight into the flow mechanisms and their influence on fan performance. The last part presents the experimental investigations carried out to validate the numerical models. For this purpose, a demonstrator of the fan including a diffuser-volute combination with variable cross-sectional area is manufactured and investigated using optical PIV (Particle Image Velocimetry) measurements.