Calculation of the characteristic diagram of an axial fan using CFD

Abstract

The characteristic curves of a ventilator with adjustable blade angle were calculated using CFD. The characteristic curve is valid for a certain blade angle of a single stage ventilator and was measured on a test stand according to DIN 24163. To evaluate the critical points for the calculation of the characteristic curves, a number of blade angles have been considered. It turned out that the points with the maximum deviation between measurement and calculation were lying close to the optimum efficiency point of the fan operation in the vicinity of the separation line. For further studies of the influence of mesh resolution, turbulence modelling and geometric modelling, one operation point showing relatively large deviations from the measurements was chosen. For this operation point, a successive refinement of the mesh was done to get a grid independent solution. The mesh of the grid independent solution was used to study the influence of several turbulence models including two equation k-ε and k-ω models and a ω based Reynolds stress model and the influence of the blade tip gap. Finally, one curve from the characteristic diagram was recalculated using the best performing turbulence model and the results were compared to measurements.