Noise Control for Cooling Fans on Heavy Vehicles

E1 - Noise of Cooling Fans in Automotive Applications

An important subsystem in surface transportation vehicles; rail bound, automotive and heavy duty is the engine cooling module. For this reason the European Commission is funding the Efficient Cooling Systems for Quieter Surface Transport (ECOQUEST) project and the overall technical objectives are innovative contributions towards reduced noise emission and energy efficient cooling modules. There three main objectives in the project concern; implement an integrated simulation platform to gather modelling tools for noise, near-field acoustic scattering and propagation towards listeners in the far field, develop thermally and acoustically optimal cooling modules, and development of innovative fan designs and new passive noise control.

Throughout this project two different main objects for fan passive noise control have been examined both experimentally and theoretically; the heat exchanger and inlet parallel baffle silencers.

For the first object seven heat exchangers were experimentally assessed, using a modified version of ISO 15186-1:2000, to test the acoustic transmission for a diffuse field. In addition a sample from each heat exchanger type was also cut out and tested by measuring the acoustic two-port in a duct, i.e., the transmission and reflection at normal incidence were determined. Theoretically, the basic configuration is assumed to be a matrix of parallel and rectangular narrow channels. The developed model is based on a so called equivalent fluid for an anisotropic medium. It is mainly dependent on the heat exchanger geometry combined with the Kirchhoff model for thermo-viscous wave propagation in narrow tubes. The proposed model is validated using the experimental results.

In order to reduce the transmission through heat-exchangers they can be fitted with parallel baffle silencers. In ECOQUEST a new type of such silencers using Micro Perforated Plates (MPP:s) have been designed and tested. Results from this work are presented showing that such MPP baffle silencers can provide up 10-20 dB added damping in the frequency range of interest.