Corn Kernel Damage Test And Analysis Of Corn Threshing Process

Corn is an important food crop,industrial raw material and animal husbandry feed in China.At present,most areas of our country in the process of changing from ear harvest to grain harvest.Due to corn variety and the special agricultural requirements in China,especially in wheat-corn rotation areas,the corn grain moisture content at harvest is generally higher,which leads to the problem of large mechanical damage to the grain.High grain broken rate is an important limiting factor for the development of mechanical corn harvesting technology.Therefore,it’s particularly important to study the characteristics of corn ear,the process of corn threshing and the forms of corn damage.In this paper,based on the research on the basic characteristics and threshing characteristics of high moisture content corn in grain harvest,combined with the situation of grain harvest in field,designed and manufactured the corn threshing test bench.Used the high speed camera system to study and analyze the process of grain threshing and separation in different threshing components,at the same time,analyzed the grain damage in different conditions.Preliminarily understood the motion process and damage of grains in the threshing interval.On the test prototype installed a combined threshing element,analyzed the corn damage under this threshing device in the field grain harvesting,the results provided reference for the development of a threshing and separating device suitable for Chinese corn with high moisture content.The main work and conclusions as follows:(1)Tested and analyzed the basic morphological parameters of high moisture content of corn ear in grain harvesting,mainly including corn length,corn diameter,corn diameter of cob and the grain number and grain number,on the basis of corn testing the change of the grain moisture content in the different harvest period,analyzed the characteristics of corn grain moisture content changes.The results showed that the moisture content in the middle part of corn ear could represent the moisture content of corn during the harvest period,and the moisture content of corn cob decreased with the decrease of moisture content,and showed a trend of accelerating dehydration.(2)The static pressure mechanical characteristics of corn seeds with high moisture content under different placement methods and the threshing force of grains in the middle part of the ear were tested with a physical property tester.The results showed that the minimum damage force of corn seeds in horizontal placement was much greater than that in lateral placement and vertical placement.When the moisture content of maize was higher than 25%,the characteristics of maize were more plastic deformation.The threshing force of tangential single-grain without support was the smallest;the threshing force under different number of supported grains was equal to the product of the threshing force of single-grain under the same number of supported grains and the number of supported grains;when the number of supported grains was the same,the acting force of single-grain bearing changed little,and decreased with the increase of the number of supported grains.(3)Based on the basic physical characteristics of corn ear and the characteristics of grain harvesting machine,developed a corn threshing test-bed.The threshing and separation processes of corn under different threshing components were recorded and analyzed by highspeed photography.The results showed that the threshing effect and separation effect of punching concave plate were lower than that of round steel concave plate;the preliminary threshing adaptability of tooth plate elements to intact ear was poor,but the threshing was more sufficient and the adaptability to broken ears was higher.the initial threshing adaptability of tooth plate element to intact ear was lower than that of round steel concave plate.The threshing process of rigid ripple rod element and polyurethane ripple rod element is similar,the threshing effect is relatively soft,and the initial threshing adaptability of intact ear is strong,which can thresh the ear while reducing the degree of damage.(4)The experiment of grain damage of single maize threshing was carried out.The analysis on maize damage of corn kernels under different conditions showed that the moisture content had a significant effect on the damage rate and the damage morphology;when the moisture content level of the grain was high,the different types of threshing elements had a significant impact on the damage rate of the grain;the tooth plate and polyurethane ripple rod elements had a significant impact on the damage rate of the grain.The damage rate increases with the increase of drum speed,and decreases with the increase of concave clearance.(5)The field experiments were carried out with installing ripple rod,polyurethane ripple rod and rigid tooth plate on the test prototype.The results showed that in the test range,the minimum damage rate of maize grain was 2.93%,the corresponding crack rate was 0.87%,the defect rate was 0.61%,the breakage rate was 1.45%,the minimum impurity rate was 0.98%,and the minimum uncleaned rate was 0.068%.Comprehensive analysis showed that the damage rate and impurity content showed a positive correlation trend,and the uncleaned rate showed a negative correlation trend within a certain range.The damaged forms of corn cob are complex and diverse.The length of damaged cob is mainly 20-40 mm,and the cross-section is mainly 1/4.In the test range,the optimum factors is the threshing speed of shear flow drum at 350r/min,the threshing clearance at the entrance of shear concave plate at 30 mm and the forward speed of machine at 0.68m/s.