Abstract
Two blade curvatures representative of those found in automotive fans are compared. Measured performances are analyzed for forward and backward curved blades, either with or without heat-exchangers placed in front of them. The backward fan demonstrated good efficiency but poor acoustics, whereas it is the contrary for the forward fan. Investigations are completed by a numerical analysis of the flow in the cooling module. Different integration effects are highlighted depending on the blade curvature, showing variation in pressure, torque and efficiency. Analyses of blade loadings show that the flow is more homogeneous with a forward curved fan and it produces less unsteadiness at the blade tip. Post-processing of detached eddy simulations (DES) shows density fluctuations on the blade wall and confirms the correlation between the large vortical structures and the acoustic sources for both fans. In addition, with the forward fan, the sound propagation is less directed towards the axis of rotation and it yields up to −3.6 dB of sound pressure level (SPL) measured in front of the cooling module. As a conclusion, any choice for a fan must result from a compromise between aerodynamics and aeroacoustics, and the final performances must be carefully checked on the module.
Highlights
Automotive thermal management relies strongly on the cooling module that is placed on the front-end of the car
A comparative study was undertaken between a forward and a backward curved fan
Tests and simulations confirm that the use of backward blades optimizes aerodynamic efficiency at the operating point at the expense of acoustics
Summary
Automotive thermal management relies strongly on the cooling module that is placed on the front-end of the car. It is composed of a set of coolers and a fan system, both designed to maximize heat exchanges in various conditions and minimize the acoustic annoyance. Stringent new regulations on vehicle efficiency and noise emission have more than ever yielded investigations of the multi-physic optimization of the fan, assessing performance in the actual context, i.e., once integrated in the cooling module. Engineers who design fans face several difficulties when sizing them. First of all, they have to make compromises of all kinds between aerodynamic performance, acoustics, packaging requirements, etc. Due to the integration effects that vary from one geometry to another, it is uncertain whether a fan system optimized for bench measurement conditions is the most appropriate for the thermal cooling of a vehicle
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