Experimental Analysis of the Flow through the Fan Stage of a High-Bypass Turbofan in Windmilling Conditions

A detailed study of the air flow through the fan stage of a high bypass turbofan in engine-out conditions is proposed, to address the key performance issues of this severe case of off-design operation. Experiments are conducted in the new turbofan test rig of ISAE, specially suited to reproduce windmilling operation in an ambient ground setup. The engine is equipped with conventional measurements to characterize the cycle performance and directional five-hole probes are used to characterize the flow across the fan stage. These first results confirm the findings of the literature that the fan outlet guide vane operates under severe off-design angle-of-attack. Massive flow separation is expected in the stator vanes, generating an important pressure loss that contributes to engine drag. This comprehensive database will allow the calibration and validation of 3D RANS simulations to provide a better understanding of the internal losses in windmilling conditions