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A Study of a Skirtless Hovercraft Design

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A Study of a Skirtless Hovercraft Design A STUDY OF A SKIRTLESS HOVERCRAFT DESIGN THESIS Edward A. Kelleher, Ensign, USNR AFIT/GAE/ENY/04-J05 DEPARTMENT OF THE AIR FORCE AIR UNIVERSITY AIR FORCE INSTITUTE OF TECHNOLOGY Wright-Patterson Air Force Base, Ohio APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED. The views expressed in this thesis are those of the author and do not reflect the official policy or position of the United States Navy, United States Air Force, Department of Defense, or the United States Government. AFIT/GAE/ENY/04-J05 A STUDY OF A SKIRTLESS HOVERCRAFT DESIGN THESIS Presented to the Faculty Department of Aeronautics and Astronautics Graduate School of Engineering and Management Air Force Institute of Technology Air University Air Education and Training Command In Partial Fulfillment of the Requirements for the Degree of Master of Science in Aeronautical Engineering Edward A. Kelleher, BS Ensign, USNR May 2004 APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED. AFIT/GAE/ENY/04-J05 A STUDY OF A SKIRTLESS HOVERCRAFT DESIGN Edward A. Kelleher, BS Ensign USNR Approved: ______ ___________ Dr. Milton Franke (Chairman) date ______ ___________ Lt Col Raymond C. Maple (Member) date ______ ___________ Lt Col Montgomery Houghson (Member) date Abstract Three proposed skirtless hovercraft designs were analyzed via computational fluid dynamics to ascertain their lift generation capabilities. The three designs were adaptations from William Walter’s hybricraft primer and his patent for a fan driven lift generation device. Each design featured Coanda nozzles, or nozzles that utilize the Coanda effect, to redirect air flow to aid in the generation of an air curtain around a central air flow. The designs also utilized a Coanda wing as a lifting body to aid in lift generation. Each design was set at a height above ground of one foot and a radius of two feet. The craft was assumed to be axisymmetric around a central axis for a perfectly circular craft, much like a flying saucer. The craft can be divided into several parts, the core, the nozzles, the plenum chamber (for designs 2 and 3), and the wing. Flow is generated from rotor blades situated one foot above the top of the core of the craft. The nozzles are located at the edges of the craft below the wing. In designs two and three the plenum chamber is the region between the core and the wing. For each design three cases were performed where t was increased for each case. This resulted in a total of nine cases, three cases for three designs. For each case the ratio of nozzle thickness to the radius of the curved plate, t/R, was set to 0.344 and t was increased while R was calculated to maintain the ratio. The computational fluid dynamics (CFD) analysis captured the pressure data and the lift forces were calculated using a pressure differential analysis. Analysis proved that the hybricraft designs could produce positive lift. While the first design did not produce positive lift, the second and third designs managed to generate enough lift to support a craft of a maximum of 52810.24 kg. The max amount of lift produced was 5388.8 N, while the minimum positive lift generated was 3642.9 N. iv Acknowledgments I would like to thank my thesis advisor, Professor Milton Franke for his help in this project and his producing of the idea. I would also like to extend my thanks to Lt Col Maple for all his help with understanding computational fluid dynamics and getting the computers to work for this thesis. Also, I want to extend a thanks to my fellow ensigns for their ever diligence in keeping the faith till the end. My final thanks is to my Coach, Raymond Bautista and the American Fencing Academy of Dayton for giving me something to distract me when needed. v ABSTRACT ................................................................................................................................................ IV LIFT OF FIGURES ................................................................................................................................. VII LIST OF TABLES...................................................................................................................................VIII LIST OF SYMBOLS.................................................................................................................................. IX INTRODUCTION........................................................................................................................................ 1 BACKGROUND ............................................................................................................................................ 1 BACKGROUND THEORY:............................................................................................................................. 3 CURRENT OBJECTIVES................................................................................................................................5 NUMERICAL MODEL SETUP ................................................................................................................. 8 RESULTS.................................................................................................................................................... 14 GENERAL.................................................................................................................................................. 14 DESIGN 1 .................................................................................................................................................. 14 DESIGN 2 .................................................................................................................................................. 19 DESIGN 3 .................................................................................................................................................. 24 ANALYSIS.................................................................................................................................................. 30 GENERAL.................................................................................................................................................. 30 DESIGN 1 .................................................................................................................................................. 31 Case 1: ................................................................................................................................................ 31 Case 2: ................................................................................................................................................ 32 Case 3: ................................................................................................................................................ 33 DESIGN 2 .................................................................................................................................................. 34 Case 1: ................................................................................................................................................ 34 Case 2: ................................................................................................................................................ 35 Case 3: ................................................................................................................................................ 36 DESIGN 3 .................................................................................................................................................. 38 Case 1: ................................................................................................................................................ 38 Case 2: ................................................................................................................................................ 39 Case 3: ................................................................................................................................................ 41 CONCLUSIONS AND RECOMMENDATIONS.................................................................................... 43 APPENDIX A ............................................................................................................................................. 46 APPENDIX B.............................................................................................................................................. 57 SOURCES ................................................................................................................................................... 58 VITAE ......................................................................................................................................................... 59 vi Lift of Figures Figure 1: Full Scale AVRO Car.......................................................................................... 2 Figure 2: Naudin's Coanda Saucer Epxeriment .................................................................. 4 Figure 3: Schematic of the First Design ............................................................................. 6 Figure 4: Schematic of the Second Design......................................................................... 7 Figure 5: Schematic of the Third Design............................................................................ 8 Figure 6: The Hybrid Grid: A Close Up View of a Nozzle Plate....................................... 9 Figure 7: The Grid for the First Design, This is a 2-d Planar Cut of the Axisymmetric
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