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

Abstract

A detailed study of the unsteady airflow through the fan stage of a bypass turbofan is pro- posed. Experiments are conducted in the turbofan test facility of ISAE, specially suited to reproduce windmilling operation in an ambient ground setup. Hot-wire anemometry is used to obtain steady Mach number and flow angle profiles as well as to characterize the unsteady, turbulent flow, at different stations across the fan stage (fan inlet, outlet and rotor/stator interface). Phase averaging of unsteady signals and integral length scale estimations provide further evidence of the presence of a vortex shedding from the stator, as well as the fact that it is correlated to the rotor blade passing frequency. Self-similarity of mean Mach number, flow angle and turbulent intensity profiles is observed. Furthermore, turbulent scale profiles are found to scale well with blade passing period.