Abstract
In order to study the aerodynamic characteristics of a Hex-rotor micro aerial vehicle (MAV) with different rotor spacing, both experiments and numerical simulations are performed in this paper. First of all, a series of aerodynamic parameters to characterize the hover performance of the Hex-rotor MAV are analyzed theoretically. Secondly, tests on the Hex-rotor MAV with different rotor spacing ratios ( $i=0.5$ , 0.56, 0.63, 0.71, 0.83, 1.00) is presented in detail. The thrust and power of the Hex-rotor MAV are obtained from the self-designed test platform. In the meanwhile, pressure and velocity distribution of the Hex-rotor MAV are obtained by Computational Fluid Dynamics (CFD) simulation. The results show that the aerodynamic performance of the Hex-rotor MAV is varied with the rotor spacing. Specifically, the rotor interference is inclined to improve the aerodynamic performance of the Hex-rotor MAV with the proper rotor spacing. Owing to the increase of rotor spacing, the interactions between rotors are weakening gradually. In addition, the uniformity of velocity distribution, the stability of downwash distribution and the integrity of vortex are the necessary conditions for a larger thrust of the Hex-rotor MAV. Finally, combined with the test and simulation results, it is also found that there is larger thrust characterized with better aerodynamic performance at $i=0.63$ , which is assumed as the best rotor arrangement of the Hex-rotor MAV. Especially for ${{Re}}=1.16\times 10^{5}$ , the thrust increases by 6.09%, and the hover efficiency increases by about 9.17% in general.
Highlights
A Hex-rotor micro aerial vehicle (MAV)composed of three coaxial rotors is emerged with a strong potential in both civil and military
In order to effectively evaluate the aerodynamic performance of the Hex-rotor MAV, two indexes are adopted for evaluation: power loading and hover efficiency
In this paper, the power loading and hover efficiency of the Hex-rotor MAV are analyzed theoretically, and the numerical simulation and experimental study are presented in detail
Summary
Composed of three coaxial rotors is emerged with a strong potential in both civil and military. The connection between adjacent coaxial rotors forms an equilateral triangle, which will make the weight of the whole machine relatively concentrated near the center of mass of the MAV This kind of coaxial multi-rotor MAV has the characteristics of compact structure, outstanding load capacity, and strong controllability of yaw [1,2,3,4,5]. The optimal rotor arrangement for this kind of Hex-rotor MAV with coaxial rotors is still unknown and insufficient in aerodynamic analysis related to the hover efficiency. In view of these facts, our current works seeks to answer the following questions: How does a change in rotor spacing between coaxial rotors affect the propulsive efficiency as a whole?. How do the interferences change into the benefit for the thrust increment without power increment for some cases?
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