A Round Robin Test of a Low-Pressure Axial Fan
G2 Sound Power Levels Determination
We discuss the reproducibility of aerodynamic and aeroacoustic results on a benchmark low-pressure axial fan at different test facilities. The interest in this type of fans is growing due to the new demands for cooling of electrified powertrains in the automotive industry. But reference data sets for validating measurement methods and simulations are scarce. We will use the benchmark case set up and documented by Zenger et al . They have published and made publicly available the geometry and test setups/methods to make it possible to reproduce their results. However, there are always practical difficulties; production differences when making the actual fan, variations in the lab setups and equipment for example.
We have 3D printed the shroud and three copies of the fan. They have then been painted/coated and manually sanded. The deviations of the final prototypes from the nominal geometry were measured in a standardized dimensional management set up. The surface roughness was also determined. The reason for printing three copies is to see the variations one can expect from small production differences.
Initially the fans were tested in a rig where accurate performance and aeroacoustic measurements can be made, but no detailed flow field measurements are available. In the benchmark case the upstream test chamber is anechoic, while in our rig the conditions are resembling that of a semi-anechoic room. We discuss the differences in the methods and results and how they can be interpreted and compensated for. The acoustic characteristic curve as well as spectra at different operating conditions are given along with discussions on directivity. Subsequent measurements in a rig which yields detailed flow field measurements were planned. However, non-conclusive results from the latter limit the discussion on results from the first testing facility.
 Zenger, F., Junger, C., Kaltenbacher, M., and Becker, S., "A Benchmark Case for Aerodynamics and Aeroacoustics of a Low Pressure Axial Fan," SAE Technical Paper 2016-01-1805, 2016, doi:10.4271/2016-01-1805.