| China,as a large corn planting country,has a lot of straw resources whose nutrients could be edible by livestock.There are many types of corn stalk fodder harvesters.Among them,the tractor-type straw harvester that can complete picking,crushing and throwing operations at one time is more suitable for straw harvesting at most areas in China.However,the overall sand content of soils in western of China is relatively high.In above areas,when the tractor-type straw harvester picked up and crushed straw,it was easy to make the contact between the corn stubble and the soil loose or pull out the corn stubble,resulting in a higher impurity rate of harvested straw.This paper takes the4JS-220 straw forage harvester as the research object,the key factors of the mechanical properties of the root and soil were obtained during straw harvesting.The design of the key components was optimized based on the analysis results.The specific research content and results are as follows:(1)In order to explore the key factors that affect the cutting force of the flail knife,a theoretical analysis of the force after the straw is cut is carried out.The results show that:the soil moisture content,straw diameter,and the angle between the straw and the ground affected the cutting force of the harvester’s flail.(2)Taking soil moisture content,straw diameter,and pulling angle as the influencing factors,the field pulling resistance of corn stalks was studied experimentally.The test results show that the order of the degree of influence of various factors on the straw pulling force was:soil moisture content>pulling angle>straw diameter;The soil moisture content was inversely proportional to the straw pulling force,and the straw diameter was directly proportional to the pulling force.Using the response surface optimal parameter solution method,the minimum pulling force of the straw within the experimental parameter range was determined to be 189.635 N,the corresponding extraction angle was 28.5°,the soil moisture content was 20.47%,and the straw diameter was 22 mm.When the extraction angle was 28.5°,the straw extraction force was the smallest.(3)The physical test and the EDEM discrete element simulation test were combined to calibrate the parameters of the root system and root-soil complex simulation model.The discrete element software was used to establish the root shear model and the root-soil composite shear model.The main factors affecting the root and root-soil composite shear force were obtained through simulation experiments,and the simulation parameters of each influencing factor were determined,among them the root shear modulus was 6.6MPa,the bonding stiffness was 1.139×10~6N/m~3,and the ultimate stress was 1.1885MPa;the root-soil composite static friction factor was 0.7,the bonding stiffness was 6.4×10~6N/m~3,and the ultimate stress was 3.3 MPa.The simulation of the corn root pulling process was carried out under different factors,and the mechanical characteristics of straw pulling process were analyzed from the microscopic point of view,and the disturbance of the corn root system to the soil under different pulling angles was explored.The results showed that the simulation test and the physical test results were basically consistent.(4)According to the above experimental research conclusions,the 4JS-220 straw fodder harvester has been optimized and improved.Designed a segmented rotating front curtain and a new combined flail and applied the harvester.Field test results show that the improved machine effectively reduces the height of the stubble and the disturbance range of the root system to the soil during the operation,the average stubble height of straw was reduced by 6.3%compared with that before the optimization of the machine;the impurity content of the straw after harvest was reduced by 1.3%compared with that before the optimization.The results of this study provide theoretical guidance for the improved design of the traction straw forage harvester. |
PDF Full Text Request