Optimum Design And Experimental Research Of Pneumatic Cylinder Seed Metering With Airflow Disturbance

In the modern soybean agricultural planting process,mechanized precision planting technology can not only reduce the labor intensity of farmers and improve operating efficiency,but also increase crop yield.The quality of the precision seeding device directly determines the quality of planting.The pneumatic seed metering device with the advantages of good seed particle size adaptability and high-speed operation is the development direction of precision seed metering devices.Most of the current pneumatic seed metering devices are single row seeding devices,which cannot be adapted to the promotion in the northern cold areas in recent years.The applied three-row planting model on the big ridge,which has the advantages of high land utilization rate,conducive to plant root distribution and improved drought and waterlogging resistance compared with the traditional soybean planting model,has been widely promoted and applied in the northern cold regions,but it is currently used The parallel arrangement of the single row seeding device will cause problems such as complex seeding structure and poor pass ability,which reduces the seeding quality.At the same time,the internal resistance of the population has a great impact on the charging performance of the pneumatic seeding device.Reduce the internal resistance of the population,increase the fluidity of the population,and improve the seed suction ability of the seed meter.Generally,methods such as setting vibrating elements and using seed disturbing teeth are used to physically disturb the population.To this end,an air-suction seed metering device for three-row planting mode on a large ridge in a cold area in the north is designed.The drum-type seed metering device is used to simplify the structure of the seed metering device to meet the needs of multi-row operations;Disturb the population,reduce the resistance of seed movement during seed filling,and improve seed filling performance.Through the combination of theoretical analysis,computer simulation analysis and experiment,the design of seed metering device and the trial production of prototype are completed.The main contents and results of the research are as follows:（1）The overall design scheme and principle of the drum seed metering device with airflow disturbanceThrough the analysis of the existing precision seeding technology combined with the requirements of three rows of agronomic planting in the big ridge,the overall design of the drum-type seeding device using positive pressure air flow disturbance was determined,and its working process and principles were described.（2）Study on the disturbance characteristics of positive pressure airflowAiming at the airflow seeding technology,the mechanical model of the population in the process of seed filling was established under the condition of the traditional closed bottom seed box structure and the seed bed screen using positive pressure airflow.factor.（3）Design of key parts of seed metering deviceAccording to the actual use and agronomic requirements,the structural parameters of the seed strainer drum were determined,and the structure of the seed box assembly with positive pressure cavity was designed.According to the proportion of seed adsorption,the seed clearing process was analyzed,and the structure was determined as the seed clearing device.（4）Analysis of the characteristics of the flow field inside the positive pressure cavityBased on the computer-aided calculation method,using Fluent numerical simulation software,a numerical simulation analysis of the flow field characteristics inside the positive pressure chamber is carried out.By numerical simulation calculation of the number and arrangement of different air inlets,the air velocity of the seed bed screen and the cavity The characteristics of the uniformity of the airflow velocity are analyzed and found that when the double inlets are arranged symmetrically on both sides of the central disturbing area,the disturbing airflow velocity through the seed bed screen is relatively uniform,which meets the conditions of providing uniform disturbing.（5）Bench performance experiment of seed metering device with airflow disturbanceBench performance experiment was carried out on the seed metering device with airflow disturbance.The influence of suction negative pressure,disturbance positive pressure and operating speed on working performance was explored.Taking the pass index,missed broadcast index and replay index as evaluation indexes,the quadratic regression orthogonal rotation combined test method was used to study the optimal working parameter combination of the airflow disturbance seed metering device,and the negative pressure of suction and positive pressure of disturbance were established 1.The operating speed is a mathematical regression model between the test factors and the evaluation index,and the influence law of each test factor on the evaluation index is obtained.The mathematical regression model is optimized and analyzed.When the negative pressure is 5 k Pa,the disturbance positive pressure is 0.7～0.8 k Pa,the operating speed is7.4～10.4 km·h^-1,the theoretical seed meter qualified index≥94.9%,and the missing seed index≤3%,the multiple index≤3.1%.