Aerodynamic Performance Modeling of Ducted Fans and Shrouded Propellers for Preliminary Design

A new methodology has been formulated for the prediction of the aerodynamic loads on the rotor blades of a ducted fan or shrouded propeller. The method, implemented in Boeing's BEARPAD code, uses combined blade element momentum theory (BEMT) to model ducted fan performance both in hover and high-speed axial flight. Included in the model are adjustments to open rotor BEMT theory that allow solutions to be generated for the ducted fan configuration, including modifications for cascade theory and tip corrections near a wall. The accuracy of the model was confirmed in validations against wind-tunnel test data. The methodology is computationally cheap and suitably accurate, making it ideal for trade studies and preliminary design work. The main objectives of the study are the inclusion of ducted fan theory into a BEMT model, the validation of said model, and an application of the theory to examine ducted fan/shrouded propeller performance, particularly in comparison to open rotors.