Automotive Blower Design with Inverse Method Applied on Wheel and Volute

D2 - Theoretical & Numerical Methods for Centrifugal Fans

Expectations in terms of energy efficiency, thermal and acoustic comfort are increasingly important in the automotive industry. The radial fan that is used for thermal management of the interior is particularly concerned because ventilation performance contributes to the well being of passengers, and to the reduction of electrical consumption of on-board systems. Recent attempts to optimize this machine have shown the difficulty to improve them while respecting the numerous operating point (ventilation of different areas, heating, air conditioning, defrost, dehumidification), the limited packaging in the dashboard and the constraints of manufacturing.
A design method aimed to reduce the development time is investigated in the present study. It is based on an inverse design method and the objectives are to improve the efficiency, to reduce the losses and flow unsteadiness.
A first detailed simulation of an existing blower was done accordingly to our test rig conditions, allowing reproducing the behavior of the complete system. Overall performance obtained were compared to experiment and discussed to assess the validity of the numerical results. Further analysis of the flow were performed to get the blade loading and to determine velocity triangles at wheel inlet and outlet. These results were used to specify targets for the 3D inverse design method to redesign the wheel.
Several wheels with different levels of complexity have been produced, and two of them were selected for study: the first one respects constraints of the plastic injection process, whereas the second one is intended to assess the remaining potential if constraints are relaxed. Numerical simulations conducted on these wheels showed improved performances when measured in term of total pressure between blade inputs and outputs.
Further possible gains were identified in the scroll which was designed for a different type of wheel and which produces significant losses. Post-processing of speed and flow distributions at the wheel exit were used to conduct a very quick re-optimization of the volute with a inverse design method for volute design. Results obtained after these two steps were verified by numerical simulation and compared to the original design in terms of overall performance and detailed flow analysis in the wheel and the volute. As expected, efficiency gains have resulted in a reduction of secondary flows in the volute, to the benefit of attenuated interaction at the tongue.