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In order to improve the reliability of fan design and the prediction of underhood engine cooling based on CFD, Valeo Motors and Actuators and Michigan State University have teamed up to develop a comprehensive experimental and numerical database. The initial focus has been on the simulations of the isolated fan environment in two different test facilities. To understand the discrepancies observed in the comparisons of integral performances, the first detailed hot wire measurements on the MSU test facility have been collected. The data are split into mean velocity components and RMS fluctuations. The former are successfully compared to three detailed turbulent numerical simulations of the corresponding facilities.

Requirement for more compact and more efficient fan systems to improve the automotive thermal management has urged Valeo to develop a complete automatic CFD procedure to numerically simulate the fan system. The present study has focused on the description and the validation of the flexible grid template used for the rotor-stator configurations. Three different efficient stators with increasing geometrical difficulties have helped testing this new capability. Grid refinement has been assessed and comparisons have been made between the initial stand-alone rotor and the same rotor with the three different stator designs. The simulations have been performed on a reasonable grid size that has been shown to capture most of the important flow features. The efficiency improvement brought by these stators has been clearly highlighted and estimated to be about 10%.

Requirement for more compact and more efficient fan systems to improve the automotive thermal management has urged Valeo to develop a complete automatic CFD procedure to numerically simulate the fan system. The present study has focused on the description and the validation of the flexible grid template that is meant to simulate the internal flow field within the fan system. This template closely fits in the previously developed rotor-stator parametric grid. The initial small rib reference design has been meshed and four different large rib cases with increasing geometrical difficulties have helped testing this new capability. The simulations have been performed on a medium size grid that has been shown to capture most of the important flow features. The ribs act as centrifugal pumps that drain airflow through the electrical motor. Larger ribs are shown to increase the flow rate through the motor by up to 25% with a marginal increase with swept ribs compared to radial ones.

The market needs for quieter and more compact engine cooling modules have led Valeo to develop a complete simulation based design (SBD) for its future fan technology. Its purpose is not only to improve the performances of the existing range, but also to reduce the design times significantly, and therefore to cut down the development costs. The current SBD involves using state-of-the-art CFD as a backbone. From an initial guess for a given design point based on a ducted flow approach, 2D blade cascade Navier-Stokes computations are performed to improve and optimize the initial profile. 3D Navier-Stokes computations are then performed to get the final stacking that will match the objective performances. All computations presented here have been achieved with TASCflow by ASC.

The market needs for quieter engine cooling modules and the upcoming stringent noise level regulations have led Valeo to develop a series of numerical codes which will give the fan designer accurate noise predictions and will also ideally complement its CFD simulation based design for its future fan technology [1]. The current approach involves three levels of noise prediction: first a global sound pressure level estimate which will use the fluid 2D CFD blade cascade information; secondly, a spectral distribution which relies on fan loads to provide a first estimate of the subjective noise; finally, a temporal approach based on the Ffowcs-Williams theory which will come the closest to the actual measurements and will fully use the 3D CFD fan data. Validation calculations and first predictions have shown that, even if an accurate absolute noise level cannot always be obtained (within 1 dBA), observed experimental trends are already well captured.

In an effort to model a complete engine cooling module, Valeo has developed static and dynamic FEA models for its engine cooling fans. The static FEA analysis has led to a significant fan weight optimization for constant Van Mises stresses and ring deflection (a 15% reduction). Both experimental and numerical results have stressed the importance of the model of the interface between the motor and the fan in the dynamic FEA modal analysis. Moreover, the main engine cooling fan modes have been identified for the first time.