Downwash distribution of single-rotor unmanned agricultural helicopter on hovering state

Zhang Songchao, Xue Xinyu, Sun Zhu, Zhou Lixin, Jin Yongkui

Abstract


The effective coverage and velocity of downwash are directly related to the assemblage of spraying system and spraying effect. The downwash of the unmanned agricultural helicopter (UAH) N-3 was discussed in the paper. The computational fluid dynamics (CFD) methods were used to simulate and analyze the distribution of the downwash, and a wind field measurement device had been designed to test the downwash of UAH N-3. In the tests, the UAH N-3 was raised up to 5.0 m, 6.0 m and 7.0 m from the ground, “annular-radial-distribution- point” method was introduced, 8 directions separated by an angle of 45° (the radial direction) with the intersection point of the main rotor shaft and the ground plane as the center, 0.5 m as the step length for the longitudinal (to 2.5 m) and radial (to 4.0 m) direction to set the sample points, considering the range of the rotor rotating circular area mainly. The 5 m height results of N-3 were fully discussed to describe the downwash distribution with the longitudinal altitude increased and the radial distance increased. The standard deviations of five test altitudes for eight directions were comparatively analyzed, the results showed that the total standard deviation was not greater than 0.6 m/s. The overall relative maximum margin of error calculated from the simulation and measurement data was between 0.6 and 0.7, which verified the credibility of the simulation data. High-order polynomials were used to fitting the simulation and measurement data, the fitting results showed that the polynomial coefficient of determination R2 met or exceeded 0.75 when the altitudes were more than 1 m, indicating the fit equation having the reference values. When the altitudes equal or less than 0.5 m, the polynomial coefficient of determination R2 was smaller, ranging during 0.3 to 0.7. The study would provide some foundations for the optimization of the assemblage of spraying system on the single-rotor UAH, which would promote China aviation plant protection.
Keywords: unmanned agricultural helicopter, single rotor, CFD simulation, downwash distribution, spraying effect
DOI: 10.25165/j.ijabe.20171005.3079

Citation: Zhang S C, Xue X Y, Sun Z, Zhou L X, Jin Y K. Downwash distribution of single-rotor unmanned agricultural helicopter on hovering state. Int J Agric & Biol Eng, 2017; 10(5): 14–24.

Keywords


unmanned agricultural helicopter, single rotor, CFD simulation, downwash distribution, spraying effect

References


Xue X Y, Liang J, Fu X M. Prospect of aviation plant protection in China. Chinese Agricultural Mechanization, 2008; 5: 72–74. (in Chinese)

Xue X Y, Qin W C, Sun Z, Zhang S C, Zhou L X, Wu P. Effect of N-3UAV spraying methods on the efficiency of insecticides against plant hoppers and Cnaphalocrocis medinalis. Acta Phytophyl Acica Sinca, 2013; 40(3): 273–278. (in Chinese)

An J L, Xiang W L, Han Z W, Xiao K T, Wang Z F, Wang X H, et al. Validation of the Institute of Atmospheric Physics emergency response model with the meteorological towers measurements and SF6 diffusion and pool fire experiments. Atmospheric Environment, 2013; 81: 60–67.

Yang F B, Xue X Y, Zhang L, Sun Z. Numerical simulation and experimental verification on downwash air flow of six-rotor agricultural unmanned aerial vehicle in hover. Int J Agric & Biol Eng, 2017; 10(4): 41–53.

Qin W C, Xue X Y, Zhou L X, Zhang S C, Sun Z, Kong W, Wang B K. Effects of spraying parameters of unmanned aerial vehicle on droplets deposition distribution of maize canopies. Transactions of the CSAE, 2014; 30(5): 50–56. (in Chinese)

Xue X, Lan Y, Sun Z, Chang C, Hoffmann W C. Develop an unmanned aerial vehicle based automatic aerial spraying system. Computers and Electronics in Agriculture, 2016; 128: 58-66.

Xue X Y, Tu K, Qin W C. Drift and deposition of ultra-low altitude and low volume application in paddy field. Int J Agric & Biol Eng, 2014; 7(4): 23–28.

Zhang S C, Xue X Y, Qin W C, Sun Z, Ding S M, Zhou L X. Simulation and experimental verification of aerial spraying drift on N-3 unmanned spraying helicopter. Transactions of the CSAE, 2015; 31(3): 87–93. (in Chinese)

Johnson W. Helicopter theory. Princeton University Press, 1980.

Gessow A, Myers G C Jr. Aerodynmics of the helicopter. New York: Frederick Ungar Publishing Co., 1985.

Wang S C, Xu Z. The simplified calculation methods of rotor aerodynamic load. Acta Aeronautica ET Astronautica Sinica, 1982; 3(2): 1–17. (in Chinese)

Miller R H. A simplified approach to the free wake analysis of a hovering rotor, Proceedings of 7th European Rotorcraft Forum, 1981.

Wang S C, Xu G H. Process of helicopter rotor aerodynamics. Journal of Nanjing University Aeronautics and Astronautics, 2001; 33(3): 203–211. (in Chinese)

Zhao Q J, Xu G H. Numerical simulations for the downwash flowfield of helicopter rotors. Journal of Nanjing University of Science and Technology, 2005; 29(6): 669–678. (in Chinese)

Ren L F, Zhang J Z, Shan Y. Effect of helicopter rotor downwash air flow on exhaust plume flow. Journal of Aerospace Power, 2015; 29(1): 51–58. (in Chinese)

Xue X Y, Lan Y B. Agricultural aviation application in USA. Transactions of the CSAM, 2013; 44(5): 194–201. (in Chinese)

Lee Y. On overset grids connectivity and automated vortex tracking in rotorcraft CFD. Maryland: Department of Aerospace Engineering, University of Maryland at College Park, 2008.

Lee T E. Design and performance of a ducted coaxial rotor in hoer and forward flight. Maryland: Department of Aerospace Engineering, University of Maryland, 2011.

Thomson S J, Womac A R, Mulrooney J E. Reducing pesticide drift by considering propeller rotation effects from aerial application near buffer zones. Sustainable Agriculture Research, 2013: 2(3): 41–51

Li J Y, Zhou Z Y, Hu L, Zang Y, Xu S, Liu A M, et al. Optimization of operation parameters for supplementary pollination in hybrid rice breeding using round multi-axis multi-rotor electric unmanned helicopter. Transactions of the CSAE, 2014; 30(11): 1–9. (in Chinese)

Wang P, Hu L, Zhou Z Y, Yang W S, Liu A M, Luo X W, et al. Wind field measurement for supplementary pollination in hybrid rice breeding using unmanned gasoline engine single-rotor helicopter. Transactions of the CSAE, 2013; 29(3): 54–61. (in Chinese)

Hu L, Zhou Z Y, Luo X W, Wang P, Yan Y A, Li J Y. Development and experiment of a wireless wind speed sensor network measurement system for unmanned helicopter. Transactions of the CSAM, 2014; 45(5): 194–201. (in Chinese)

Zhang B, Tang Q, Chen L P, Xu M. Numerical simulation of wake vortices of crop spraying aircraft close to the ground. Biosystems Engineering, 2016; 145: 52–64.

Molari G, Benini L, Ade G. Design of a recycling tunnel sprayer using CFD simulations. Trans. ASAE, 2005; 48(2): 463–468.

Tsay J, Ozkan H E, Brazee R D, Fox R D. CFD simulation of moving spray shields. Trans. ASAE, 2002; 45(1): 21–26.


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