Physics-Based Design and Optimization Strategy for Low-Pressure Axial Fans

Abstract For cost and manufacturing reasons, low-pressure axial fans are typically manufactured with three-dimensionally curved sheet metal blades of constant thickness. However, the design method for low-pressure axial fans presented in this work is also suited for the design of axial fans with thin blades. In addition, there is an increasing demand for a free shaped hub geometry, for example a conical hub contour. In the extended design strategy, the concept of the radial equilibrium is applied under the specification of a blade work distribution in the form of a design total pressure distribution in the radial direction on five partial flow sections. In addition, the radial equilibrium and the specified design total pressure distribution are also specified on five sections in the axial direction along the blade. This method is based on the application of pure analytical physics-based equations, which are solved on each partial flow section in the radial and axial direction and allows a detailed design of the blade geometry. Furthermore, the presented analytical extended design strategy has been optimized using statistical methods. This has been performed with ANSYS CFX 2023 and the ANSYS Workbench. For this purpose, a meta-model-based optimization strategy for the designed blade angles is proposed. The iterative application of the indirect optimization process, consisting of a DOE analysis, a response surface method (RSM) and a subsequent multi-objective optimization on the axial section in the direction of flow is efficient and effective. Finally, the extended design and optimization strategy has been applied and verified with numerical and experimental data. The comparison of the characteristics of the measurement data with the numerical CFD results showed a very good agreement and the accuracy and reliability of the developed CFD model have been validated.