Comparison Of Theory And Experiment For Propfan Inlets

Studies have indicated that the use of propfans can result in fuel savings of 20-25% relative to turbofans. Therefore, a program was initiated to perform wind-tunnel tests on a series of inlet models for advanced tractor, turboprop installations. Single-scoop, twin-scoop, and annular inlets were tested to obtain inlet pressure recovery and distortion, external cowl surface pressures, external cowl forebody drag, and propeller blade stress data. An analysis was undertaken for each of the propfan inlet configurations tested using Lockheed's QUADPAN panel program. Calculated nacelle surface pressures correlate well with experiment, except where Mach number is high or viscous effects predominate. The effect of the inlet interference flowfield on the propeller was calculated using Lockheed's PROPVRTX propeller analysis program. The results showed that displacing the inlet in the aft direction reduced the adverse effects on the propeller cyclic stresses. Measured propeller stress data support these results. It is concluded that inlet/cowl designs can be assessed by computational methods.