Towards a Full Digital Approach for Aeroacoustics Evaluation of Automotive Engine Cooling Fans and HVAC Blowers

H1 - Lattice Boltzmann Methods (ii)

In the automotive industry, the reduction of the main noise contributors of passenger cars such as engine, rolling, and aerodynamic noise, is giving more and more value to the acoustic efficiency of components and subsystems. This is particularly true with rotating machines, such as engine cooling fans and Heating Ventilation and Air Conditioning (HVAC) blowers. Since it can represent a strong competitive advantage and be a real market differentiator, automotive suppliers have to address the products’ acoustic performances as early as possible in the development phase.
Experimental methods have been used historically to reduce the most obvious noise sources and led to acoustically efficient products. But they have also shown limitations such as time, cost of prototypes, mechanical and aerodynamic constraints. In addition, the targets specified by car manufacturers are becoming harder to achieve. When dealing with experiments, the lack of insight into acoustic phenomena can reduce innovation opportunities. With the decreasing cost of computational resources, using a digital approach could help go beyond these constraints, reduce the number of expensive prototypes, accelerate the products development cycles, and bring more understanding in the noise generation mechanisms. Integrating these methods in the current development process of fan and blower systems could lead to achieving better acoustic performances and even exceeding the present targets while, at the same time, managing aerodynamic and mechanical objectives.
In a first publication [1], it has been shown how PowerFLOW, a compressible and unsteady Computational Fluid Dynamics (CFD) solver based on the Lattice-Boltzmann Method (LBM), can accurately capture the flow induced noise phenomena at the origin of the broadband contributions of a Condenser Radiator Fan Module (CRFM). It has been successfully used to rank different fan designs upon their aeroacoustics performances. A more recent study [2] presented its accuracy at predicting the tonal noise radiated by such a fan but also the effect of an upstream geometry on broadband noise. In this paper, the integration of this numerical methodology in the development process of Delphi Thermal Systems will be discussed, leading to better aeroacoustics performances and more efficient products. The use of this numerical simulation for predicting aeroacoustics phenomena can be extended to other products, which will be shown with the first validation results of HVAC blower noise predictions using PowerFLOW. Acoustic power predictions of an automotive HVAC blower freely discharging in a semi anechoic environment will be compared to experiments (Fig. 1). Transient and spectral analyses will be performed to give a better understanding of the main flow-induced noise generation mechanisms (Fig. 2).

Note : Figure 1 & 2 can be requested by email

[1] M. Piellard, B. Coutty, V. Le Goff, F. Pérot, V. Vidal, “Direct aeroacoustics simulation of automotive engine cooling fan system: an application study”, Aachen Acoustics Colloquium, Aachen, Germany, November 27-29 2013.
[2] M. Piellard, B. Coutty, V. Le Goff, F. Pérot, V. Vidal, “Direct aeroacoustics simulation of automotive engine cooling fan system: effect of upstream geometry on broadband noise”, 20th AIAA/CEAS Aeroacoustics Conference, No. AIAA Paper 2014-2455, Atlanta, GA, June 16-20 2014.