为了找出多旋翼无人机喷洒农药时影响农药沉积的因素及其影响程度,提高雾滴在靶标上的沉积水平,并通过试验制定相应的试验方法和规范,在单因素试验的基础上,采用Box-Benhnken的中心组合试验设计理论对施药机具的喷雾参数进行研究.以飞...为了找出多旋翼无人机喷洒农药时影响农药沉积的因素及其影响程度,提高雾滴在靶标上的沉积水平,并通过试验制定相应的试验方法和规范,在单因素试验的基础上,采用Box-Benhnken的中心组合试验设计理论对施药机具的喷雾参数进行研究.以飞行高度、飞行速度、喷头流量等工作参数为影响因素,以雾滴在靶标上的沉积水平为目标函数,建立雾滴沉积水平的二次多项式数学模型,并分析模型的有效性与因子间的交互作用.利用Design-Expert 8.0.5软件的回归分析法和响应面分析法对模型进行优化分析,得到施药机最优喷洒参数组合.结果表明,对雾滴沉积水平影响大小依次为飞行高度、飞行速度、喷头流量;最优喷洒参数组合为飞行高度2.0 m,飞行速度3.7m·s^(-1),喷头流量430 m L·min^(-1),此条件下的雾滴在靶标上的最大沉积水平为68.69%,且与模型预测值相比相对误差为±5%以内.展开更多
In recent times,the use of vertical take-off and landing(VTOL)multi-rotor Unmanned Aerial Vehicle(UAVs)for spraying chemical pesticides against weeds and pests has recently become popular.The current aerial spray appl...In recent times,the use of vertical take-off and landing(VTOL)multi-rotor Unmanned Aerial Vehicle(UAVs)for spraying chemical pesticides against weeds and pests has recently become popular.The current aerial spray application research is primarily focused on examining the influence of UAV spraying parameters such as flight height,travel speed,rotor configuration,droplet size,payload and wind velocity.The downwash airflow velocity generated by the UAV rotor propeller has a significant impact on the droplet deposition process.A test rig was developed to measure the downwash airflow pattern generated by the rotor propeller of a UAV.In this investigation,a six-rotor electric autonomous UAV sprayer was used to investigate the parameters and distribution laws of downwash airflow velocity.The downwash airflow velocity was measured using portable anemometers mounted on the test rig at radial positions viz.,0 m,0.5 m,1 m,1.5 m and 2 m,perpendicular to(X)and parallel to the UAV’s flight direction(Y).The experiment was conducted at three levels of hover height,viz.,1 m,2 m and 3 m(Z)and three levels of payload,viz.,0 kg,5 kg,and 10 kg.The special downwash airflow distribution pattern was analysed using the Python programming language(Version 3.7).Results show that the downwash airflow velocity generated by the radial position of the UAV rotor is evenly distributed on the rotating loop and the standard deviation of the downwash airflow velocity is less than 0.5 m/s.The maximum downwash airflow velocity of 13.8 m/s was observed below the rotor at 10 kg payload capacity,1 m hover height(Z),and 0.5 m in the X-direction.The minimum downwash wind field of 0.3 m/s was observed at 0 kg pay load capacity,1 m height,and 2 m in the X-direction.The downwash airflow velocity along each position in the radial direction of the rotor increases initially and then decreases.This downwash airflow distribution results helps in mounting of spray nozzle configuration to drone sprayer which helps to understanding spray liquid distribution and ot展开更多
空中加油吊仓多采用"涵道式冲压空气涡轮"(Ducted Ram Air Turbine,以下简称DRAT)作为动力装置。空气涡轮性能的优劣直接影响DRAT的工作性能。为了对吊仓飞行高度以及飞行表速对空气涡轮性能影响进行研究,找到减少涡轮流动损...空中加油吊仓多采用"涵道式冲压空气涡轮"(Ducted Ram Air Turbine,以下简称DRAT)作为动力装置。空气涡轮性能的优劣直接影响DRAT的工作性能。为了对吊仓飞行高度以及飞行表速对空气涡轮性能影响进行研究,找到减少涡轮流动损失,提高系统的输出功率和效率的方法。采用NUMECA软件对涡轮流动进行叶轮机械数值仿真,对涡轮飞行包线内性能变化进行分析,得到了涡轮在飞行包线内的最小功率点和对应的最小功率,并通过对空气涡轮性能分析,建立一套关于空气涡轮性能的可行和实用的数值仿真方法。展开更多
Gurney Flaps(GFs) are used for improving the performance of variable speed tail rotors. A validated analytical helicopter model able to predict the main and tail rotor power is utilized. The fixed height GF has substa...Gurney Flaps(GFs) are used for improving the performance of variable speed tail rotors. A validated analytical helicopter model able to predict the main and tail rotor power is utilized. The fixed height GF has substantially small influence on the tail rotor power in hover and low to medium speed forward flight, and can obtain significant power reduction in high speed flight.This ability can be enhanced by decreasing the tail rotor speed. With the deployment of GF, the collective pitch of the tail rotor decreases, and the maximum tail rotor thrust increases. The GF can compensate the reduction of the maximum thrust by the decrease in the tail rotor speed. The GF with a height of 5% of the chord length can almost remedy 50% of the thrust reduction introduced by decreasing 10% of the tail rotor speed. With the increase of GF height, the maximum thrust generated by the tail rotor increases. The GF with larger height can cause the increase in the tail rotor power in hover and low to medium speed flight. The retractable GF can obtain more power savings than the fixed height GF. However, the benefit is substantially small even in high speed flight. Considering the side effects introduced by the active GF, the fixed height GF may be more preferable. The mechanism for the retractable GF to generate more tail rotor thrust is to increase the lift in advancing side due to the higher dynamic pressure.展开更多
文摘为了找出多旋翼无人机喷洒农药时影响农药沉积的因素及其影响程度,提高雾滴在靶标上的沉积水平,并通过试验制定相应的试验方法和规范,在单因素试验的基础上,采用Box-Benhnken的中心组合试验设计理论对施药机具的喷雾参数进行研究.以飞行高度、飞行速度、喷头流量等工作参数为影响因素,以雾滴在靶标上的沉积水平为目标函数,建立雾滴沉积水平的二次多项式数学模型,并分析模型的有效性与因子间的交互作用.利用Design-Expert 8.0.5软件的回归分析法和响应面分析法对模型进行优化分析,得到施药机最优喷洒参数组合.结果表明,对雾滴沉积水平影响大小依次为飞行高度、飞行速度、喷头流量;最优喷洒参数组合为飞行高度2.0 m,飞行速度3.7m·s^(-1),喷头流量430 m L·min^(-1),此条件下的雾滴在靶标上的最大沉积水平为68.69%,且与模型预测值相比相对误差为±5%以内.
文摘In recent times,the use of vertical take-off and landing(VTOL)multi-rotor Unmanned Aerial Vehicle(UAVs)for spraying chemical pesticides against weeds and pests has recently become popular.The current aerial spray application research is primarily focused on examining the influence of UAV spraying parameters such as flight height,travel speed,rotor configuration,droplet size,payload and wind velocity.The downwash airflow velocity generated by the UAV rotor propeller has a significant impact on the droplet deposition process.A test rig was developed to measure the downwash airflow pattern generated by the rotor propeller of a UAV.In this investigation,a six-rotor electric autonomous UAV sprayer was used to investigate the parameters and distribution laws of downwash airflow velocity.The downwash airflow velocity was measured using portable anemometers mounted on the test rig at radial positions viz.,0 m,0.5 m,1 m,1.5 m and 2 m,perpendicular to(X)and parallel to the UAV’s flight direction(Y).The experiment was conducted at three levels of hover height,viz.,1 m,2 m and 3 m(Z)and three levels of payload,viz.,0 kg,5 kg,and 10 kg.The special downwash airflow distribution pattern was analysed using the Python programming language(Version 3.7).Results show that the downwash airflow velocity generated by the radial position of the UAV rotor is evenly distributed on the rotating loop and the standard deviation of the downwash airflow velocity is less than 0.5 m/s.The maximum downwash airflow velocity of 13.8 m/s was observed below the rotor at 10 kg payload capacity,1 m hover height(Z),and 0.5 m in the X-direction.The minimum downwash wind field of 0.3 m/s was observed at 0 kg pay load capacity,1 m height,and 2 m in the X-direction.The downwash airflow velocity along each position in the radial direction of the rotor increases initially and then decreases.This downwash airflow distribution results helps in mounting of spray nozzle configuration to drone sprayer which helps to understanding spray liquid distribution and ot
文摘空中加油吊仓多采用"涵道式冲压空气涡轮"(Ducted Ram Air Turbine,以下简称DRAT)作为动力装置。空气涡轮性能的优劣直接影响DRAT的工作性能。为了对吊仓飞行高度以及飞行表速对空气涡轮性能影响进行研究,找到减少涡轮流动损失,提高系统的输出功率和效率的方法。采用NUMECA软件对涡轮流动进行叶轮机械数值仿真,对涡轮飞行包线内性能变化进行分析,得到了涡轮在飞行包线内的最小功率点和对应的最小功率,并通过对空气涡轮性能分析,建立一套关于空气涡轮性能的可行和实用的数值仿真方法。
基金supported from the National Natural Science Foundation of China (No. 11472129)the Science and Technology on Rotorcraft Aeromechanics Laboratory Foundation of China (No. 6142220050416220002)+2 种基金the Foundation of Graduate Innovation Center in NUAA of China. (No. KFJJ20170102)the Fundamental Research Funds for the Central Universities of Chinaa project funded by the Priority Academic Program Development of Jiangsu Higher Educational Institution of China
文摘Gurney Flaps(GFs) are used for improving the performance of variable speed tail rotors. A validated analytical helicopter model able to predict the main and tail rotor power is utilized. The fixed height GF has substantially small influence on the tail rotor power in hover and low to medium speed forward flight, and can obtain significant power reduction in high speed flight.This ability can be enhanced by decreasing the tail rotor speed. With the deployment of GF, the collective pitch of the tail rotor decreases, and the maximum tail rotor thrust increases. The GF can compensate the reduction of the maximum thrust by the decrease in the tail rotor speed. The GF with a height of 5% of the chord length can almost remedy 50% of the thrust reduction introduced by decreasing 10% of the tail rotor speed. With the increase of GF height, the maximum thrust generated by the tail rotor increases. The GF with larger height can cause the increase in the tail rotor power in hover and low to medium speed flight. The retractable GF can obtain more power savings than the fixed height GF. However, the benefit is substantially small even in high speed flight. Considering the side effects introduced by the active GF, the fixed height GF may be more preferable. The mechanism for the retractable GF to generate more tail rotor thrust is to increase the lift in advancing side due to the higher dynamic pressure.
