Abstract
Micro aerial vehicles (MAVs) usually suffer from several challenges, not least of which are unsatisfactory hover efficiency and limited fly time. This paper discusses the aerodynamic characteristics of a novel Hex-rotor MAV with a coaxial rotor capable of providing higher thrust in a compact structure. To extend the endurance during hover, flow field analysis and aerodynamic performance optimization are conducted by both experiments and numerical simulations with different rotor spacing ratios (i = 0.56, 0.59, 0.63, 0.67, 0.71, 0.77, 0.83, 0.91). The measured parameters are thrust, power, and hover efficiency during the experiments. Retip ranged from 0.7 × 105 to 1.3 × 105 is also studied by Spalart–Allmaras simulations. The test results show that the MAV has the optimum aerodynamic performance at i = 0.56 with Retip = 0.85 × 105. Compared to the MAV with i = 0.98 for Retip = 0.85 × 105, thrust is increased by 5.18% with a reduced power of 3.8%, and hover efficiency is also improved by 12.14%. The simulated results indicate a weakness in inter-rotor interference with the increased rotor spacing. Additionally, the enlarged pressure difference, reduced turbulence, and weakened vortices are responsible for the aerodynamic improvement. This provides an alternative method for increasing the MAV fly time and offers inspiration for future structural design.
Highlights
We proposed a hex-rotor Micro aerial vehicles (MAVs) with a novel structure consisting of a coaxial rotor which showed a better payload capacity with a compact airframe
The experimental results showed that the aerodynamic characteristics and hover performance of MAVs can be improved notably by adjusting the horizontal distance between rotors
The data presented exhibited a weak tendency of inter-rotor interference with the decreased rotor spacing ratio
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Micro aerial vehicles (MAVs) have attracted widespread interest in society due to the flexibility in performing flight missions in complex environments. The extensive applications of quad-rotor MAVs, in particular, have promoted innovation in the fields of film shooting, express delivery, military surveillance, and so forth [1,2,3,4,5]. Further applications are restricted on account of the load capacity limitation.
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