Downwash Distribution of the Single-rotor Umanned Agricultural Helicopter on Hovering State
Umanned agricultural helicopter(UAH)has been applied for a certain scale in China aviation plant protection because its flexibilities,no need of special landing site and low demand for airspace.Experiments from relevant literatures have proved that single-rotor UAH aerial spraying application on pest and disease preventions of rice,corn and other crops has higher liquid deposition and penetration rates with the the assistant of rotor downwash,especially during the tillering period for rice and pregnancy period(closure line period)for corn,the control efficiency is much better than the convertional(ground machines).The effective coverage and velocity of downwash are directly related to the assemblage of spraying system and spraying effect.The downwash of the UAH N-3 was dissused in the paper.The computational fluid dynamics(CFD)methods were used to simulate and analyse 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 5,6 and 7m 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,0.5m as the step length for the longitudianl(to 2.5m)and radial(to 4.0m)direction to set the sample points,considering the the range of the rotor rotating ciecular area mainly.The 5m height results of N-3 were fully discussed to describe the downwash distribution.With the longitudinal altitude increased,the downwash velocity varied from big to small,the became bigger quickly on the same logitudinal section,the minimun occurred at the altitude about 1m while the maximum occurred at the altutide about 2m.With the radial distance increased,the downwash velocity varied from small to big thenbig to small,the velocity value which relatively bigger were almost during the radial distance 0.5m to 1.5m,which the maximum value was 11.37m/s.The downwash variation close to the ground(the altitude less than 0.5m)was not obvious.The standard deviations of five test altitudes for eight directions were comparatively analysed,the results showed that the tota l standard debiation was not greater than 0.6m/s.The overrall relative maximum margin of error calculated from the simulation data and measurement data which was as the basis were between 0.6 and 0.7,which verified the credibility of the simulation data.Highorder polynomials were used to fitting the simulation and measurement data,the fitting results showed that the polynomial coefficient of determination R2 met or exceed 0.75 when the altitudes more than 1m,indicating the fit equation having the reference values.When the altitudes equal or less than 0.5m,the polynomial coefficient of determination R2 were 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.
single rotor unmanned agricultural helicopter CFDsimulation downwash
Zhang Songchao Xue Xinyu Sun Zhu Chang Chun Zhou Lixin Jin Yongkui
Nanjing Research Institutes for Agricultural Mechanisation,Ministry of Agriculture,Nanjing 210014,China
国内会议
广州
英文
101-114
2016-11-12（万方平台首次上网日期，不代表论文的发表时间）