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Aerospace 2016, 3(4), 30;

Numerical Study of Transition of an Annular Lift Fan Aircraft

UAV Research Institute, Northwestern Polytechnical University, 127 West Youyi Road, Xi’an 710072, China
Author to whom correspondence should be addressed.
Academic Editor: Robert Spall
Received: 14 August 2016 / Revised: 12 September 2016 / Accepted: 17 September 2016 / Published: 23 September 2016
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The present study aimed at studying the transition of annular lift fan aircraft through computational fluid dynamics (CFD) simulations. The oscillations of lift and drag, the optimization for the figure of merit, and the characteristics of drag, yawing, rolling and pitching moments in transition are studied. The results show that a two-stage upper and lower fan lift system can generate oscillations of lift and drag in transition, while a single-stage inner and outer fan lift system can eliminate the oscillations. The characteristics of momentum drag of the single-stage fans in transition are similar to that of the two-stage fans, but with the peak of drag lowered from 0.63 to 0.4 of the aircraft weight. The strategy to start transition from a negative angle of attack −21° further reduces the peak of drag to 0.29 of the weight. The strategy also reduces the peak of pitching torque, which needs upward extra thrusts of 0.39 of the weight to eliminate. The peak of rolling moment in transition needs differential upward thrusts of 0.04 of the weight to eliminate. The requirements for extra thrusts in transition lead to a total thrust–weight ratio of 0.7, which makes the aircraft more efficient for high speed cruise flight (higher than 0.7 Ma). View Full-Text
Keywords: VTOL; annular duct; lift fan; aircraft; transition VTOL; annular duct; lift fan; aircraft; transition

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Jiang, Y.; Zhang, B. Numerical Study of Transition of an Annular Lift Fan Aircraft. Aerospace 2016, 3, 30.

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