Aerodynamic Layout Optimization Of A New Type Four Ducted Fan Micro Aerial Vehicle

Aerodynamic layout design of a new four ducted fan micro aerial vehicle is presented in this work. Its overall design is carried out, during which the flying wing aerodynamic layout with Inverse Zimmerman wing is used,two ducted fans as a dynamic system are installed above and under the wing respectively, the take-off weight can be estimated to be about 300 g, S3010 wing airfoil and Inverse Zimmerman wing plane shape with excellent aerodynamic performance are chosen as wing. Ducted fan power system can be designed according to the four states of new four ducted fan micro aerial vehicle in task profile which includes hovering flight, vertical flight, transient state from vertical flight to cruise and cruise.The installation locations of ducted fan including axial direction, spanwise and longitudinal direction relative to wing are optimized with the method of the orthogonal experimental design. Firstly, the scheme of installation locations of ducted fan can be generated by selecting orthogonal table39L(3), and then the aerodynamic performances can be calculated by the density solver with the method of time derivative pretreatment and RNG k -e turbulence model. The eventual optimization results show that the optimal level combination of single objective to minimize pitching moment coefficient and drag coefficient and maximize the lift coefficient and lift-to-drag ratio is that the locations of axial direction, spanwise and longitudinal direction relative to wing are 120mm、55mm and 60mm、120mm、50mm and 60mm、80mm、45mm and 70 mm and 80mm、50mm and 60 mm for pitching moment coefficient、lift coefficient、drag coefficient and lift-to-drag ratio respectively; multi objective optimal level combination is that the locations of axial direction, spanwise and longitudinal direction relative to wing are 80mm、45mm and 60 mm respectively.The aerodynamic performances of integrated optimal level combination above are analyzed. Firstly, thrust characteristics of ducted fan under hovering state can be analyzed. Secondly, the aerodynamic performances under cruise state including lift coefficient, drag coefficient and pitching moment coefficient, lift-to-drag ratio of wing and thrust characteristic of ducted fan are analyzed with different attack angle and fan rotating speed. Finally, flow characteristics on the surface of wing are analyzed. Limit streamlines on the surface of wing show that there is no flow separation under smaller attack angle; flow separation begins to be appeared on the wing tip with the increase of attack angle; with the attack angle continues increased, flow separation and attached line are generated respectively from the wing leading edge to trailing edge and separated flow between flow separation line and attached line spans from the wing root to the wing tip with the adsorption effect of wing tip vortex, adverse pressure gradient on the surface of wing is increased to make separation line near the leading edge move forward gradually and the area of attached flow is expanded gradually with the effect of adsorption of the wing tip vortex when attack angle is increased.