Research And Test On Air-assisted Spraying Technology Based On Single Hanging Track In Solar Greenhouse

Spraying operation in greenhouse is one of the most important means to effectively control pests and diseases to ensure the yield and quality of vegetable products.The complex facility structure and high-density planting pattern severely restrict the development of automated sprayer equipment for greenhouse.Researching spraying strategies and developing high-efficiency and low-cost greenhouse autonomous sprayers are of great significance for improving the timeliness of the prevention and control of greenhouse pests and diseases,and reducing labor intensity and health risks of pesticide application operations.In this thesis,an autonomous air-assisted sprayer based on a single hanging rail and penetrating three-dimensional spray pattern was developed in accordance with the structural characteristics of the solar greenhouse in northern China.The key structure and parameters of the sprayer are determined through theoretical analysis and simulation research.The influence of key technologies such as nozzle configuration of spray boom,spray pattern,tilt angle correction of the boom,electrostatic air-assisted spray and other key technologies on the spray deposition quality has been studied through laboratory or field tests.The specific research content and main conclusions are as follows:1)The autonomous air-assisted sprayer based on a single hanging track,include track travelling device and the lifting device suitable for the greenhouse spray were designed;The air volume of the greenhouse air-delivered spray was calculated by The momentum displacement method;an air-assisted spray device with malposed nozzles was designed;A waist electrode was designed for flat fan nozzle,and the effect of applied voltage on the charging capacity of the waist electrode was studied.The results show that the inductive capacity of the waist electrode increases with the increase of applied voltage and then decreases steadily.The maximum charge-to-mass ratio is 4.4 m C kg^-1 at 6 k V,which is 1.9times that of the circular electrode.The synchronization between the spray system and the mechanical system was studied2)A simplified motion model of the droplet was established in a circular free jet,which was verified by detecting the motion boundary of droplets under multiple working conditions.The results show that the average prediction error of the moving boundary of large droplets is-0.24 m and the relative error is-4.9%under different positions and airflow speed conditions,indicating that the motion model accurately predicts the movement of droplets in the mid-plane.The numerical simulation results show that with the increase of flow velocity by 30%,the maximum range of big and medium droplets increases by 10%and 13.2%,respectively,and the deposition areas of them move downstream by 0.5 m and 0.9 m respectively;The size of the droplet is also an important factor affecting the movement.The smaller the droplet,the larger the range,but the smaller the deposition range.The droplet release position also affects the movement,increasing the height by 0.3 m and moving forward by 0.3 m,and the range of medium and big droplets is increased by 0.4 m and 0.28 m,respectively.3)Static deposition distribution test of the air-assisted spray device with different air volume,nozzle type&model and installation position shows that the influence of each factor on the spray deposition distribution is consistent with the numerical simulation results;With the increase of air volume by 28.5%,the effective range and the ratios of spray range to coefficient of variation(R_RCV)of fan-shaped nozzle（FSN）increase by 44.7%and 17.5%respectively,which are better than hollow cone nozzles（HCN）,and the FSN with a small flow rate is particularly protruding.The installation height of the nozzle and the front-out distance affects the spray distribution.The increase of the installation position within a certain range was little effect on the spray range,but the coefficient of variation（CV）of the axial distribution decreases rapidly and then slightly increases.With the increase of the front-out distance of the nozzle axial installation,the more uniform the spray distribution and the increase of the spray range,but the upstream blind area increases.Compared with a single nozzle（FSN 02）with the same flow rate,the double nozzle（FSN01）stacking arrangement boom obtains a larger spray range and a more uniform spray distribution,and the ratios of spray range to CV(R_RCV)are 10.2 and 18.6,respectively.the width index of the double nozzle stacking boom that of the three nozzles at 16.9.In addition,theR_RCVof double nozzle（FSN 01）stacking arrangement boom is slightly higher than that of three nozzles（FSN 01）stacking arrangement.4)The field test on cucumber and tomato crops showed that the spraying rate of automatic operation of the sprayer is 154 L·hm^-2,and the operating efficiency is 130min·hm^-2 which is about 4.4 times that of knapsack spraying.The spray pattern of the boom has a significant effect on the spray distribution.Compared with the Pattern 2（P2:down&translate spray）,Pattern 1（P1:lift&translate spray）obtains a more uniform spray deposition distribution with a comparable average coverage.The overall average coverage rate(C_{a T}),overall coefficient of variation（CV_T）of spraying Patterns P1 were16.6%,69.5%for cucumber crops,and 21.5%,82.8%and for tomato crops,respectively,while P2 were21.6%,103.9%,and 21.8%,94.0%,respectively.but the C_{a T} was slightly lower than the latter.The results also show that the laboratory static deposition distribution is strongly correlated with the equivalent static deposition distribution in the field test,especially in the spray pattern P1（R=0.920）.5)The effects of the spray avertence angle（θ_C）and the moving speed（V_x,V_y）of the spray device on the deposition distribution were studied.The test results showed thatθ_Caffected the difference in average coverage（Er）between the left and right canopy significantly,and Er decreased with the increase ofθ_C;The moving speed of the spray device also affects Er,the horizontal speed V_x increases and the vertical speed V_y decreases,and Er increases accordingly.The cumulative equivalent of deviation spray duration was proposed,and a regression model of Er onθ_C,V_x,V_y was constructed with R² 0.913.θ_Cwas predicted by the regression model in three moving speed conditions,and two of them were verified by tests.The results showed that Er was reduced from 8.6%and 10.4%to-2.3%and 2.9%,respectively;the C_{a T} was increased from 20%and 20.5%to 25.3%and24.3%,respectively;and the CV_T was reduced from 63.5%and 71.1%to 59.7%and 55.8%.It was shown that the avertence angle correction of spray significantly improved the uniformity of deposition and also contributed to the improvement of C_{a T} and C_VT.The field test on tomato crops showed that Er was reduced from 11.7%to 4.0%;the C_{a T} and CV_TBefore and after avertence angle correction,the C_{a T} increased from 20.6%to 25.6%,while the CV_T decreased from 83.7%to 62.0%,which was consistent with the results of the validation test.6)Field tests on tomato crops shows that the intervention of electrostatic spray has a significant positive effect on spray quality.The average coverage rate of the population sample under electrostatic spray was 28.7%,a slight increase compared to non-electrostatic spray.The CV of coverage rate of the population sample was 48.3%,which was significantly better than that of non-electrostatic spray 62.0%.The CV of the radial coverage distribution(CV_{a G})has been greatly improved,from 33.7%of non-electrostatic spraying to 17.9%of electrostatic spraying.