Rotor Blade Unsteady Aerodynamics at High Loading Including Dynamic Stall

Abstract

The unsteady aerodynamics of rotor blades generated by stator-rotor interactions at high-loading, off-design conditions is investigated through experiments in a low-speed axial-flow research compressor. The inlet guide vanes (IGV’s) generated inlet flow and the resulting 1 stage rotor blade unsteady aerodynamic response at design and offdesign conditions are quantified. Measurements define the compressor time-average performance, the 1 stage rotor relative flow field, and the rotor blade surface unsteady pressures. The rotor blade unsteady aerodynamic response as a function of flow coefficient is considered in three ways. First, time histories of the ensemble-average rotor blade surface unsteady pressures are examined. Second, the frequency content of these unsteady pressure data is examined and finally, the measured and the linear theory unsteady aerodynamic responses are compared. Wake induced dynamic stall on the rotor blade suction surface is identified at off-design time-average incidence angles. The stall vortex, characterized by a low-pressure unsteadiness moving down the chord at 40% of the free stream velocity, is identified as the key factor of unsteady blade response that must be modeled at offdesign conditions.six.