Design And Testing Of Agricultural Nozzles Based On Magnetorheological Fluid

At present,the protection of crops in China is mainly done by plant protection machinery.Because old-fashioned plant protection machinery can not adapt to the diversity of terrain and meet the needs of China’s agricultural economic development,the development of agricultural aviation application equipment has been rapidly developed.With the improvement of the flight control system,the market puts forward higher requirements for precise application of drugs.The development of variable spray systems is a necessary condition for precise application of drugs.The development of variable nozzles is a key link.At present,the UAV application nozzle mainly relies on foreign imports or directly uses ordinary ground hydraulic nozzles,which is not conducive to achieving precise spraying.Aiming at the current situation that the flow control method of aviation plant protection nozzles is relatively simple,a variable nozzle based on magnetorheological fluid is designed.The magnetic rheological effect is used to control the flow rate of the nozzle;the structural size of the magneto-rheological fluid nozzle is designed and theoretically analyzed.The MATLAB software was used to visually simulate the generated magnetic field,and the magnetic field distribution was visually observed.The nozzle is tested for the flow rate change caused by factors such as the amount of magnetorheological fluid injection and the coil input voltage.The specific research done in this topic includes:(1)Detecting the droplet size of LU120 series and F110 series hydraulic nozzles under different pressures and spraying heights,calculating their droplet distribution span and droplet size variation coefficient;then,in the field environment,F110,TR80 and IDK120 series nozzles were used to compare the droplet size,deposition amount and effective spray width of aerial spraying on the DJI MG-1 drone.The test results show that the orifice diameter and the spray height have an effect on the droplet size,but the effect of the spray height does not show a linear relationship;the type of the nozzle mainly affect the droplet size and effective spray width during field operations.The amount of deposition is affected by a combination of factors.Finally,the application status and advantages of the existing typical hydraulic nozzles are summarized.The research and improvement direction of spraying equipment in the future was analyzed.(2)The theoretical basis of the new variable nozzle-the magnetorheological fluid was analyzed,and the design idea of the magnetorheological fluid nozzle was formulated according to its characteristics.The structure and size are specifically determined.Then,the motion and rheological properties of the internal magnetorheological fluid under the action of the magnetic field of the magnetic field generating device(circular coil)were numerically analyzed.The designed coils were visually simulated by MATLAB software.Finally,the actual magnetic induction intensity around the coil is tested by a Gauss meter to determine the feasibility of the overall scheme.(3)An indoor spray test platform was built.The effects of magnetorheological fluid injection amount,coil voltage on nozzle spray flow rate and droplet size were tested.The experimental results show that the flow of magnetorheological fluid is smaller with the increase of the amount of magnetorheological fluid injection.When the coil voltage is larger,the flow rate decreases with the magneto-rheological fluid injection amount.As the voltage increases,the flow rate increases and shows a slow-fast-slow trend;The droplet size of the nozzle decreases with the increase of the amount of magnetorheological fluid injection,and increases with the increase of the coil voltage.The influence of the magnetorheological fluid injection amount or the coil voltage on the droplet size and distribution span of the nozzle is much smaller than that of the diaphragm pump,and the overall droplet size of the nozzle is in the middle M range.(4)Install the magnetorheological fluid nozzle and spray system on the unmanned aerial vehicle,select the hydraulic nozzle with similar fog droplet spectrum for outdoor flight comparison test,and analyze the average deposition amount of each nozzle.The results show that the average droplet deposition amount of the magnetorheological fluid jet head under the three coil voltages is between F110-03 and IDK120-02 nozzles,but the average deposition amount on both sides is low,and the effective spraying area is concentrated on the route.Near the midpoint,the effective spray width is narrow.When the voltage is small,the flow rate of the magneto-rheological fluid jet head is less affected,but it still affects the deposition amount of the mist droplets,especially the central position.Since the nature of the magnetorheological fluid tends to be more liquid at this time,it is in a more unstable state in the magnetorheological fluid chamber,and is susceptible to fluctuations due to external vibration.Through the indoor and outdoor comparison test analysis of typical hydraulic nozzles and magnetorheological fluid nozzles,it can be seen that the magneto-rheological fluid nozzle designed by this subject can achieve a certain degree of flow regulation through the national control coil voltage,and its droplet spectrum and each The No.3 nozzle of the hydraulic nozzle is similar,and the effective spray width is narrower in the deposition characteristics,but it has better anti-drift performance similar to the IDK series nozzle.This study can provide reference for the development of precision application equipment for plant protection drones.