Numerical investigation on the hovering performance of contra-rotating ducted rotor for micro air vehicle
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ORIGINAL RESEARCH
Numerical investigation on the hovering performance of contrarotating ducted rotor for micro air vehicle Sang Wook Lee1 • Jong Kwon Kim2 Received: 15 December 2019 / Accepted: 3 September 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this study, the hovering performance of contra rotating ducted rotor (CRDR) for micro air vehicle (MAV) was performed by using computational fluid dynamics technique. A rotor shape with 5-inch diameter and 4.3-inch pitch for MAV was used. Aerodynamic performance and flow structures were investigated for a single rotor (SR), Contra Rotating Open Rotor and CRDR at various operating RPMs. In case of CRDR, thrust increased by 170% compared to that of SR due to the acceleration of flow at the duct inlet, and approximately 20% thrust improvement was observed compared to CROR. Duct of the CRDR was found to produce approximately 30% of the total thrust. Because torque of rear rotor is slightly greater than that of front rotor, adjustment of RPM or rotor blade shape would be necessary for the torque cancellation. Efficiency of each system was compared based on the power loading, and it was found that CRDR configuration is the most efficient configuration to generate thrust by consuming minimum power.
1 Introduction MAV (Micro Air Vehicle) means a small aircraft of less than 6 inches (154 mm) using a rotating wing to enable vertical takeoff and landing (Benedict et al. 2015). MAV is applicable not only to military usage but also various ways in indoor and outdoor such as fire surveillance, leisure, sports, lifesaving, and so on. These various missions require long flight times and high payload capabilities. However, owing to the small size and low flight speed, MAV operates at low Reynolds number flow regime where viscous effects are dominant. Thus the power consumption increases while the thrust decreases, thereby rapidly decreasing the rotor efficiency, which means low power loading (Hrishikeshavan et al. 2011). Various methods have been studied to increase thrust under size constraints. Representative methods are contra rotating open rotor (CROR) and contra rotating ducted rotor (CRDR). CROR induces thrust increase and torque & Sang Wook Lee [email protected] 1
Department of Mechanical Design Engineering, Wonkwang University, 460 Iksan-daero, Iksan 54538, Jeonbuk, Republic of Korea
2
Junsung E&R, 793 Hanam-daero, Buk-gu, Gwangju 61263, Republic of Korea
reduction by vertically positioning rotors rotating in opposite directions. Stuermer (2008) performed unsteady simulation of CROR using DRL TAU code to analyze the complex aerodynamic interactions. The author showed that rear rotor should have bigger pitch angle to obtain thrust balance between front and rear rotor. Grazia De Giorgi et al. (2017) analyzed the aerodynamic performance of CROR by using computational fluid dynamics (CFD), and showed that the effect of CROR is increased when the pitch angle of propeller is large or the forward ratio
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