Stator Performance for Automotive Cooling Fans with Unsteady Inlet Conditions

The choice between using stators or support arms downstream of an engine cooling fan depends on the lift and drag forces. A transient, Computational Fluid Dynamic (CFD) simulation was performed of a stator configuration. Results for an unsteady (sinusoidal) inlet condition, based on Laser Doppler Velocimetry (LDV) data of a flow downstream of an automotive fan, are compared to steady inlet conditions. Vortex shedding and suction side separation were observed with a steady inlet condition. Due to the vortex shedding the lift coefficient fluctuated. The mean lift coefficient was 68% lower than the published data used for design. The mean lift coefficient observed was similar to what was expected from a cambered plate of 2% camber at the same angle of attack. The performance of the stators under unsteady inlet conditions was different than under steady inlet conditions and therefore steady flow velocities are not an effective input to design. For the flow condition tested the stators provided a benefit compared to support arms, and therefore, their use is recommended.