A RANS-based CFD method for prediction of design and installation effects on automotive cooling fan noise

Abstract

Given the quietness of electrified powertrains, the concern about noise generated by axial cooling fans has gained importance in the automotive industry, especially in the premium sector. Besides, the need of substantial fan-driven airflow during standstill battery charging represents an added reason to develop silent cooling systems that meet the noise regulations for public and residential areas. This has caused an increasing interest in conducting further research on axial fan acoustics and in achieving more effective and efficient computational fluid dynamics (CFD) and computational aeroacoustics (CAA) analyses in the design process of this type of machines.

As part of the so-called eFan2 project, this work aims at investigating the potential of steady-state Reynolds-averaged Navier-Stokes (RANS) simulations to yield profitable conclusions regarding the influence of the design and installation on the aeroacoustic noise generated by axial cooling fans. The moving reference frame (MRF) method was employed to recreate the effect of fan rotation on the computational fluid continuum. As the main core of the study, the impact of different mesh parameters and turbulence modelling on the total broadband acoustic power predictions was investigated on two fans with different geometry and architecture, for which validation data were produced during a dedicated experimental campaign.

A robust modelling methodology and valuable conclusions were achieved, highlighting the relationship between mesh resolution and predicted flow features and noise levels. Comparison with experimental data showed that the simulations reasonably well capture the trends of the total acoustic power over different operating conditions. Also, the simulation strategy for cases having greater tonal character is discussed.