Numerical and experimental investigation of performance improvements of a cross-flow fan

Abstract

The cross-flow fan has an inherent ability to provide thrust to an airfoil as well as provide boundary layer control. The thrust can be easily vectored and usually the cross-flow fan is fully embedded within the airfoil, making its operation relatively safe. Those characteristics make it very favorable as a propulsive means for a vertical takeoff and landing (VTOL) aircraft. However, further design improvements are needed for competitive comparison with existing conventional aircraft propulsion methods. The baseline configuration was scaled from a 12-inch diameter, 30-bladed rotor developed by Vought Systems in the 1970s to a 6-inch rotor as a more realistic size for integration into a propulsive wing. Using the computational fluid dynamics (CFD) software, ANSYS CFX, previous baseline configuration models were validated at full-speed range to verify the software's prediction. Then, a model with the cross-flow fan embedded at the trailing edge was built and different configurations were examined. An attempt was made to improve the performance of the cross-flow fan embedded airfoil by thrust and thrust-to-power ratio, and lift and drag forces were calculated. CFD results have shown that a rotor with fewer blades can improve performance and a 22-bladed rotor was selected and examined experimentally. Results were compared with the baseline 30-bladed rotor.