| Rice is one of the main food crops in China,but rice pests and diseases are serious.Pests and diseases occur at all stages of development during the whole growth period,and there are many types of pests and diseases.The two most common pests and diseases(rice planthopper and sheath blight)in rice plant occur mainly in the middle and lower canopies of rice.At present,most of the commonly used plant protection machines are trapped by the dense upper canopy of rice,and the liquid droplets are difficult to reach the middle and lower parts of the dense canopy of rice.High annual rice yield loss due to poor pest control in the country.Choosing the appropriate application method and working parameters to solve the problem of rice application in the middle and lower canopy of rice has important significance for ensuring stable yield and high yield of rice.Based on the existing researches domestic and foreign,taking rice plant as research object.The research on the movement law of rice plant under the action of canopy opener and the motion law of air flow under the action of rice canopy were studied.This study provides a theoretical basis for the optimal design of rice plant protection machinery and the optimization of field work parameters.The specific research contents are as follows:1.Experimental study on elastic modulus of rice.The elastic modulus of rice stalks was tested by three-point bending test method.The SMS texture analyzer was used in this experiment.Field sampling was carried out on the heading stage of rice plant growth.Five clusters of rice with different sizes were selected at different planting positions,and the sheaths coated on the outer surface of the stem were removed.The stems of each section of rice were intercepted,and the numbers were IN1,IN2,IN3,and IN4 from bottom to top.The length of each stem was cut to 9.5cm according to the testing requirements of the SMS texture analyzer.The prepared samples were classified,and the outer diameter D and the wall thickness t of eachstem of the rice were measured with a digital vernier caliper.Then,the stems of each section of the rice plant were placed on the SMS texture analyzer table and obtained by the three-point bending method.The displacement curve of the force of each stem.Based on the calculation method,the elastic modulus of each stem of rice plant was calculated.The causes of the errors in the test results were analyzed,and the elastic modulus values of the various sections of rice stems at the heading stage were finally determined.Provide a parameter basis for rice plant simulation analysis.The specifically determined elastic modulus values ??are IN1: 8.47 Gpa,IN2: 6.25 Gpa,IN3: 4.71 Gpa,IN4: 2.95Gpa2.Simulation of rice transient dynamics based on canopy opener.Firstly,a three-dimensional simulation model of rice plant was established.The parameters of the three-dimensional model of rice plants were determined by field parameter measurement and laboratory parameter measurement.The main characteristic parameters include: plant height,rice leaf number,rice leaf area,rice leaf width,rice stem length,rice stem diameter,rice stem wall thickness and rice elastic modulus.The finite element model required for the simulation is established by meshing and parameter setting the 3D model.Different heights of the canopy opener were set,and the transient dynamics simulation of rice plant was carried out to analyze and study the force-deformation characteristics of rice plant.And based on different canopy opener heights,establish the corresponding mathematical relationship.At the same time,the reliability of the simulation was verified by high-speed photography experiments.3.Research on the drag coefficient of rice crop.Set up the drag coefficient test device.The whole test bench is divided into three parts,namely the air inlet,the air outlet and the test zone.The test bench has a height of 1.2m and a width of 1.5m.A fan is placed in front of the air inlet.The height of the fan is basically the same as the height of the test bench.The test bench is equipped with a 4m front and rear airflow stabilization section,the length of the intermediate test zone is set.It is 3m.Using the built test platform,the parameters of the drag coefficient of the rice canopy were determined through a series of tests.The fan is set to different frequencies,and thecanopy density of the rice canopy can be set by the anemometer,pressure sensor and thermometer.The wind speed before and after the test zone at different frequencies and different canopy densities V1,V2,pressure P and temperature T data collection.Through the theoretical calculation formula,the drag coefficient under different canopy densities is calculated.The drag coefficient under different canopy densities and the drag coefficient under different wind speeds are analyzed.And analyze the reasons for the fluctuation of the drag coefficient.The drag coefficient of rice was finally determined to be 0.51.In order to verify the reliability of the results of this study,the results obtained in this study were tested and verified.Through the determined drag coefficient Cd value,?P' under each leaf area density is calculated and compared with the measured ?P to verify the reliability of the Cd value.4.Based on the wind speed,the simulation study of rice CFD airflow field.Firstly,a three-dimensional simulation model of rice was established.The parameters of the three-dimensional model of rice plants were determined by field parameter measurement and laboratory parameter measurement.The main characteristic parameters include: plant height,rice leaf number,rice leaf area,rice leaf width,rice stem length,rice stem diameter,rice stem wall thickness and so on.The finite element model required for the simulation is established by meshing and parameter setting the3 D model.CFD simulation was carried out on rice under different wind speeds,and the airflow velocity at various points in the canopy of rice was analyzed and studied.And determine the corresponding test plan to verify the simulation results to ensure the reliability of the simulation results.5.Based on different working parameters,the distribution characteristics of rice canopy droplet deposition.Based on potted rice and water sensitive paper,the field of fog deposition distribution was tested.In the previous experiment,the leaf width of rice was measured,and the leaf width of different rice was different.The width of rice leaves was about 0.7cm-1.5cm.Therefore,in order to match rice leaf width and water sensitive paper,the width of the water sensitive paper was cut to 1.5 cm.Test points were selected on each rice plant and water sensitive paper was placed.The water sensitive paper was subjected to droplet deposition treatment by image processingmethod,and the droplet deposition rate under various working conditions was statistically analyzed.From the analysis,it can be seen that combined with the canopy opener type and the air assistance type(compared with the separate mechanical canopy opener type and the air assistance type),the droplet deposition rate can be effectively increased,and the relative mist uniformity is ensured,but different working parameters have different applications.Therefore,in the actual situation,it is necessary to adjust each parameter according to the actual situation to achieve the optimal effect of the spray.When different pests occur in rice pests and diseases,the corresponding working methods and parameters should be adjusted to apply the target to effectively solve the pests and diseases in different canopy positions. |
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