Experimental and Numerical Investigation of Blade Pressure Fluctuations on a CFK-Bladed, Counterrotating Propfan

In order to investigate pressure fluctuations on the blade surface experimentally, a CFK - bladed Counterrotating Prop-fan CRISP with an outer diameter of 1m has been instrumented with 20 piezoresistive pressure sensors on each rotor. An accompanying two-dimensional numerical simulation has been conducted using the unsteady code TRACE-U. The flowfield was subsonic in both rotors because of a chosen operating point of approximately 52% of the design speed at a corrected mass flow of 108 kg/s. Upstream potential effects upon the first rotor where found to be relatively small at this operating point. The paper focuses on downstream effects on the second rotor of both viscous and potential nature. The main sources causing fluctuations in blade pressure were to be found wake shedding from the first rotor, pressure perturbations caused by the wake of the first rotor impinging on the leading edge of the second rotor and reflections of these pressure perturbations on adjacent blade ro ws running upstream. An analysis of these unsteady flow phenomena taking into account both experimental and numerical data will be presented including a detailed comparison of both sets of data.