• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.48 no.2
• /
• pp.89-97
• /
• 2020

In this study, a numerical analysis was performed on 26 inch single and coaxial propeller using the ANSYS Fluent 19.0 Solver to analyse the effect of the distance between coaxial propellers as one of the design parameter. The Moving Reference Frame (MRF) method was used for single propeller, while the sliding mesh method was used for a coaxial propeller to analyse the flow field varying with azimuth angle. The thrust and power are decreased as the upper and lower propeller approaching each other. As H/D is increased, interference between the propellers is decreased. According to the flow field variable contour of the coaxial propeller, it appears that the change in aerodynamic performance is due to the loading effect and the tip vortex wake effect.

• Journal of Aerospace System Engineering
• /
• v.15 no.3
• /
• pp.30-44
• /
• 2021

Experimental investigation of counter-rotating propellers is subject to multiple time and cost constraint because of additional design parameters unlike single propeller. Also, a lot of computing time and resources are required for numerical analysis due to consideration of the interference between the upper and lower propellers. In the present study, numerical simulations were conducted to investigate the hover performance of counter-rotating propellers by using actuator method which is considered to be time-efficient. The accuracy of the present numerical methods was validated by comparing the ANSYS Fluent which is commercial CFD code. The axial spacing and rotational speed were selected as the analysis variables, and the aerodynamic performance was obtained under various conditions. Based on the obtained results, the Figure of Merit (FM) of single propeller and counter-rotating propellers and a prediction factor which enables prediction of counter-rotating propeller performance using a single propeller were derived to evaluate availability of the actuator method.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.8
• /
• pp.699-708
• /
• 2021

In this paper, the aerodynamic and aeroacoustic characteristics that vary depending on the rotation axial distance between the upper and lower rotor, which is one of the design parameters of the coaxial rotor, is analyzed in the hovering condition using the computational fluid dynamics. Aerodynamic analysis using the Reynolds Averaged Navier Stokes equation and the aeroacoustic analysis using the Ffowcs Williams ans Hawkings equation is performed and the results were compared. The upper and lower rotor of the coaxial rotor have different phase angle which changes periodically by rotation and have unsteady characteristics. As the distance between the upper and lower rotors increased, the aerodynamic efficiency of the thrust and the torque was increased as the flow interaction decreased. In the aeroacoustic viewpoint, the noise characteristics radiated in the direction of the rotational plane showed little effect by axis spacing. In the vertical downward direction of the axis increased, the SPL maintains its size as the frequency increases, which affects the increase in the OASPL. As the axial distance of the coaxial rotor increased, the noise characteristics of a coaxial rotor were similar with the single rotor and the SPL decreased significantly.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.3
• /
• pp.293-300
• /
• 2009

The rotorcraft-based unmanned aerial vehicle(UAV) capable of performing close-range surveillance and reconnaissance has been developed. Trade studies on mission feasibility led to the adoption of a coaxial rotorcraft with twin rotors counter-rotating in one axis and driven by electric motors. A commercial off-the-shelf flight control computer(FCC) and a radio frequency modem were adopted for autonomous navigation. In order to achieve an aerial view, commercial charge-coupled device camera was also integrated into the vehicle. The performance of the completed vehicle was proved with manual flight test, and mission capability was verified through waypoint navigation flight after being equipped with FCC. This paper treats the whole process of design and system integration for development of the coaxial rotorcraft UAV.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.50 no.7
• /
• pp.497-505
• /
• 2022

Performance and hub vibratory load analyses for a lift-offset coaxial rotor are conducted using a rotorcraft comprehensive analysis code, CAMRAD II. The lift-offset coaxial rotor is trimmed to match the total rotor thrust(lift-offset coaxial rotor's thrust) or the individual rotor thrust(upper and lower rotor thrusts, respectively) in this study. The individual rotor's lift and torque, and effective rotor lift to drag ratio for the total rotor are investigated for various advance ratios and lift-offset values. The two result sets with different trim methods are similar to each other and they are correlated well with the wind-tunnel test results. Therefore, the present study using CAMRAD II validates successfully the aeromechanics modeling and analysis techniques for the lift-offset coaxial rotor.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.10
• /
• pp.875-883
• /
• 2007

The objective of this research was to develop a coaxial rotor MAV which is suitable for a indoor reconnaissance mission. Preliminary design parameters were determined, based on the dimensions of other reference MAVs. The designed rotor performance was estimated by Blade Element Momentum Theory, and the analyses were compared against the measurements. Stability and vibration issues of the prototype were circumvented by making parts of vehicle with NC machine, as well as equipped with teetering rotor and stabilizer. The designed coaxial rotor MAV showed successfully flight equipped with video camera. However, it was founded that further research activities should be focused on efficient rotor design to obtain better performance.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.5
• /
• pp.458-465
• /
• 2011

UAV-UGV teaming concept has been proposed that can compensate for weak points of each platform by providing carrying, launching, recovery and recharging capability for the VTOL-UAV through the host UGV. The teaming concept can expand the observation envelop of the UGV and extend the operational capability of the UAV through mechanical combination of each system. The spherical-shaped coaxial rotorcraft UAV is suggested to provide flexible and precise interface between two systems. Hybrid navigation solution that included vision-based target tracking method for precision landing is investigated and its experimental study is performed. Feasibility study on length-variable rotor to provide the compact configuration of the loaded rotorcraft platform is also described.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.560-562
• /
• 2017

This paper presents the development and test results of a test rig for confirming the hover performance of the coaxial propeller which is applied to the drone in order to carry out the mission that requires high payload such as the development of the courier drones. the performance of each propeller was measured by varying the thrust and torque according to the H/D ratio. the Thrust sensor and torque sensor were used to measure the thrust and torque generated when the propeller rotated, and a photo sensor was used to measure the rpm. it used the data acquisition system to acquire data from each sensor, and used the Labview softwaer to control data storage, monitoring and BLDC motor control. In the test, each propeller meansured the figure of mefit according to the chansge of the interval at the same rpm.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.12
• /
• pp.1011-1018
• /
• 2021

This numerical study conducts the modeling and the hover performance analyses of coaxial co-rotating rotor(or stacked rotor), using a rotorcraft comprehensive analysis code, CAMRAD II. The important design parameters such as the index angle and axial spacing for the coaxial co-rotating rotor are varied in this simulation study. The coaxial co-rotating rotor is trimmed using the torque value of the upper rotor of the previous coaxial counter-rotating rotor or the total thrust value of the previous coaxial counter-rotating rotor in hover. The maximum increases in the rotor thrust is 1.84% for the index angle of -10° when using the torque trim approach. In addition, the maximum decreases in the rotor power is 4.53% for the index angle of 20° with the thrust trim method. Thus, the present study shows that the hover performance of the coaxial co-rotating rotor for e-VTOL aircraft can be changed by the index angle.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2008.11a
• /
• pp.515-516
• /
• 2008