Installation Effects on the Flow Generated Noise from Automotive Electrical Cooling Fans 2020-01-1516

With the electrification of road vehicles comes new demands on the cooling system. Not the least when it comes to noise. Less masking from the driveline and new features, as for example, cooling when charging the batteries drives the need for silent cooling fans. In this work a cluster installation of electrical fans is studied in different generalized installations and operating conditions. The fans are installed in a test rig where the operation could be controlled varying the speed, flow rate and pressure rise over the fan. On the vehicle side of the fan a generalized packaging space (similar to an engine bay for conventional vehicles) is placed. In this packaging space different obstruction can be placed to simulate the components and radiators used in the vehicle. Here generalized simple blocks in different configuration are used to provide well defined and distinct test cases. Of special interest are cases with poor inlet flow profile and the influence of this on the sound generation. Noise results are compared to scaling laws for the influence of fan speed, efficiency and clustering. It is shown that the fans are not so sensitive to the downstream installation as long as they are not run in an extreme end of the efficiency curve. For engineering use a scaling law with relative fan speed is sufficient. More unexpected results are seen when clustering the fans. The cluster makes more noise than the individual fans suggest. It was also found that deactivating two of the four fans actually increases the noise in the tested installation. These clustering effects are believed to be due to non-uniform inlet flow with increased turbulence levels.