Modern Design of Automotive Axial Cooling Fans Using Inverse Methods

Many companies developing automotive axial fans have database of fan geometries that have been developed over a number of years as a result of long period of iterative development based on CFD and experimental tests. The know-how embedded in these optimum geometries is not very transferrable to other applications where different flow rates or pressure rise are required. Also the demand for more efficient and silent devices, especially for future BEVs and FCEVs push the aerodynamicist towards the limits of the classic methodologies. The aim of this paper is to present a methodology in which the important know-how of an optimum existing design is captured by using an inverse design method to reverse engineer the existing blade and hence recover the optimum loading of the fan blade. Then use this optimum loading as a basis for the design optimization of the automotive cooling fan that meets the new challenging requirements. In this paper, we want to show how this approach was implemented as well as the benefits gained on performance, acoustics and time-to-delivery. In order to combine both existing methods a complex aerodynamic design process involving reverse engineering, CFD simulations and experimental validation has been set. Starting from the loading obtained from reverse engineering of an existing design a process was followed in which the spanwise work and streamwise loading were varied systematically by using the inverse design method and the resulting performance evaluated by using a previously validated CFD simulation set up. Parallel, structural and modal analysis simulations were performed to ensure the integrity during operation. Performance measurements have confirmed the CFD simulations results and acoustic measurements showed an excellent behavior.