针对固定翼农用飞机所搭载航空喷头施药雾滴分布研究的需要,该文依照低湍流度风洞设计原理设计了 IEA-I型高速风洞。该风洞型式为直流开口式,主要由动力段、过渡段、扩散段、稳定段、收缩段及试验段等部分组成,风洞总体尺寸为 9.8 m×1.2 m×1.8m(长 ×宽×高)；动力段选用离心风机；扩散段为小角度扩散,扩散角 5°；稳定段采用六角形蜂窝器和 9层阻尼网组合设计；收缩段缩比 10.24；试验段截面直径为 300 mm。该文采用热线风速仪,皮托管和高速 PIV系统测定了风洞试验段气流品质,试验结果表明:试验段风速 7.6～98 m/s连续可调,气流紊流度小于 1.0%,试验段风场均匀度小于 0.4%,平均气流偏角小于 0.2°,气流动压稳定系数小于 2.0%,归一化轴向静压梯度小于 0.02。该风洞能模拟固定翼农用飞行器作业飞行条件,为进一步研究航空喷头的参数优化提供试验平台。

Agricultural aerial spray is one of the most efficient methods for large area plant protection.However, it suffersfrom the great loss of pesticide droplets, which is caused by the drift.Besides the impact of external environment (windspeed, flight altitude, relative humidity, and so on), the droplet distribution scope generated by the aerial spray nozzledominates its drift potential.The high speed wind tunnel becomes one of the most important tools for quantitativelyevaluating the aerial spray nozzles, because of its repeatability and stability in providing different test conditions.The IEA I high speed wind tunnel was designed by the authors to estimate the performance of the aerial spray nozzles mounted onthe fixed wing agricultural aircraft.In order to obtain a good flow quality, a low turbulence wind tunnel design principle was used to design this wind tunnel.The IEA I high speed wind tunnel was built up at the National Engineering ResearchCenter of Intelligent Equipment for Agriculture in Beijing in April 2015.It was an open circuit blowing type, andcomposed of power section, flexible section, diffusion section, settling chamber, contraction section and test section.Thetotal length of the wind tunnel was about 7.8 m, the height was about 2 m, and the roughness of the internal faces of thewind tunnel was less than 5 μm.A 75 kW centrifugal blower was used in the power section, which could provide a volume flow rate of 25 161 m3/h at the rated fan speed of 3 000 RPM.A flexible section was used to insulate the wind tunnel bodyfrom the vibration of the power section.The diffusion section had a 5° diffusion angle to avoid flow separation.A speciallydesigned hexagon honeycomb of stainless steel and 9 stainless steel screens with carefully selected mesh size wereembedded inside the settling chamber.These kinds of structures could reconcile the flow and reduce the flow disturbancesin the settling chamber.The contraction section was designed with a 5th power wall surface shape curve, a contraction ratioof 10.24, and an exit diameter of 300 mm.In July 2015, the flow quality of the wind tunnel was tested carefully with hotfilm, pitot tube and high speed PIV (particle image velocimetry), which strictly followed the flow field specification on high speed and low speed wind tunnel (GJB1179-1991).The objective of the test was to determine if the wind tunnel couldreach its standard of design on speed range, turbulence intensity, flow field uniformity, and so on.The hot film was used tomeasure the wind speed and the turbulence intensity of the wind tunnel.It was found that the wind speed of the tunnelvaried from 7.6 to 98 m/s and the turbulence intensity of the flow was less than 1.0%.There were linear relations between the wind speed of the tunnel and the frequency of the centrifugal blower, and the determination coefficient(R2) was 0.967 8.The high speed PIV system was used to measure the instantaneous flow field in the test section of the tunnel.The flow fielduniformity (coefficient of wind speed variation) under different wind speeds was found to be less than 0.4% and the averaged flow inclination angle was no more than 0.2° .The pitot tube was used to measure the static and dynamicpressures of the flow in the test section.The stability coefficient of dynamic pressure was less than 2.0%.The axial lengthof the test section was determined to 460 mm and the normalized axial static pressure gradient was no more than 0.02 inthis range.After being tested comprehensively, the IEA I high speed wind tunnel has achieved the design specification,and it can be a suitable test platform for aerial spray nozzles by providing real flight flow field of the fixed wing agriculturalaircraft.

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植保无人机作业风场测量及雾滴飘移控制技术研究(GJHZ2015-7)；