Viability of Cross-Flow Fan with Helical Blades for Vertical Take-off and Landing Aircraft

Abstract

The cross-flow fan (CFF) is a lifting and propulsion device that retains the advantages of a fixed-wing aircraft by using a ducted lift fan. There is no upper limit to the rotor length-to-diameter ratio of a CFF, allowing the device to be installed along the length of the wing or lifting device. The CFF discharged vector can be easily rotated about the fan axis since the fan has no angular requirements, further allowing the capability of vertical take-off and landing (VTOL) by thrust vectoring. CFF possess the potential to propel an airframe to flight; however adequate thrust must be produced by the CFF in order for it to realize VTOL. Conventional CFFs designs with straight blades produce unacceptable noise levels for personal air vehicle operation. It is believed that helical blades could solve the sound pressure level problem and produce more thrust to aid VTOL. Using computational fluid dynamics (CFD) software, ANSYS-CFX, a three-dimensional (3-D) straight-bladed model was validated against previous studys experimental results. A 3-D model with helical blades was constructed to investigate the performance. The analytical results have shown that helical blades could increase the thrust performance of a CFF, and could possibly realize VTOL.