Comparison of a Singularity- and an Inverse Design Method for Axial Flow Fans Based on Numerical Simulations

Abstract

In this contribution two different design methods for axial flow profiles are presented. A direct method based on a singularity method (SDM) is compared with an inverse design method (IDM). For the application of the SDM a profile is used with a circular arc camber line and a thickness distribution of bisuper-ellipses. The stagger angle is adjusted in such a way that the turning of the flow on the cross section is realized. For the adjustment of the stagger angle of the cross section the fast working SDM is applied. The stagger angle is varied until the corresponding deflection angle calculated by the SDM is reached. The IDM consists of an inverse boundary layer- and an inverse potential theory method. Along the suction side the shape factor of the boundary layer is prescribed conveniently for the laminar and turbulent part. The velocity distribution at the outer edge of the boundary is calculated by an inverse boundary layer method. On the pressure side the velocity distribution is chosen in such a way that a corresponding circulation is realized for turning the flow. Finally, the whole geometry of the cascade is calculated by the inverse potential theory method. The examination of one cross section is done numerically using the commercial RANS Solver ANSYS CFX. Low Reynolds number of approximately 4.25 × 105 and the transition from laminar to turbulent are taken into account by the transition SST model.