| With the adjustment of China’s grain industrial structure,the cultivation of grain corn is gradually reduced,and it is transformed into fresh corn with higher economic value.At the same time,the good taste and unique flavor of fresh corn are deeply loved by the majority of people.Therefore,the research on mechanized planting of fresh corn has become an important subject of agricultural research.With the expansion of fresh corn planting area,the mechanization of fresh corn ear harvest is imminent.There are some applications of fres h corn ear harvester at home and abroad,but there are some problems such as poor cleanliness in the ears after harvest,which make the storage and transportation and subsequent deep processing of fresh corn ears inconvenient,so it is very important to study the impurity removal device.In view of the problems existing in the operation of the existing fresh corn harvester at home and abroad,such as the pulling of the stem,the inability to pick up the corn ears on the broken stem,the high damage rate of the grain and the high impurity content of the ear in the existing fresh corn harvesting and impurity removal device,a positive pressure air flow impurity removal device for the fresh corn ears harvesting is designed,that is,the combination of the posit ive pressure air flow and the impurity removal roller is used for the fresh food harvesting It can effectively remove the long stalks and leaves contained in the ear when the fresh corn ear is harvested,greatly reduce the miscellaneous rate of the ear,and remove the ear on the pulled stem to avoid the waste of the ear.Compared with the traditional fresh corn ear combine harvester,the device has the advantages of low power consumption,clean impurity removal,low noise and low damage to grains.The main research contents and conclusions are as follows:(1)Through consulting the literature and materials of fresh corn ear harvesting machinery at home and abroad,this paper analyzes the advantages,disadvantages and working performance of various models,summarizes the shortcomings and limitations of the existing models in the field of fresh corn impurity removal,and studies and develops a scheme of impurity removal combining positive pressure air flow and impurity removal roller.According to the requireme nts of the ear impurity removal device of fresh corn and the characteristics of fresh corn harvest,a positive pressure roller impurity removal device was designed.(2)According to the main operation purpose of the device,the parameters of fresh corn pla nts were measured.According to the needs of this paper,the shape and size of fresh corn plants were measured.The biggest difference between fresh corn and grain corn is the difference of water content,so the water content of fresh corn plants is measur ed,and the water content of fresh corn in the harvest time is about 65%.When designing the key components of the device,the mechanical properties of fresh corn plant are very important.According to the shear,bending and torsion tests of fresh corn stalk,the maximum shear stress of fresh corn stalk is 2100n,the mean value of shear modulus is 4.89mpa,the mean value of shear modulus is 2.41gpa,the modulus of elasticity is 3.67mpa,Poisson’s ratioμ=0.32.It provides the basis for the parameter design of the device.(3)The flow field of the fan is simulated by ANSYS FLUENT software,and the velocity vector diagram of the flow field is obtained.Through the analysis of the velocity vector diagram of the flow field,the streamline of the flow field is obtained.In order to meet the installation requirements of the device and not affect the impurity removal performance of the device,the angle between the fan outlet and the water plane is 30°.Through the dynamic analysis of the fan to the hybrid leaves,the equation is solved by the Euler trapezoid method using MATLAB software,and the air flow velocity is optimized to be 2.3～4.0m/s.When the feeding velocity is4m/s,the effect of removing the hybrid leaves is the best.In order to ensure the smoot h discharge of the leaves,the range of fan speed is 300r/min<n_w<688r/min.Based on the mechanism analysis of the surface roughness of the impurity removal roller,using the similar amplification theory and considering the characteristics of fresh corn,the surface of the impurity removal roller is designed to be corrugated.In order to ensure the smooth operation of the device,it is combined with the spiral roller to achieve the purpose of removing residual stalks.According to the formula,the length and diameter of the impurity removal roller are 995mm and 75mm,and the speed range of the impurity removal roller is 597r/min～985r/min through the dynamic analysis and speed analysis of the residual straw.The static analysis of the impurity re moval roller is carried out by ANSYS,and the equivalent stress nephogram and the equivalent displacement nephogram of the impurity removal roller are obtained.In order to ensure that the mechanism will not have resonance and ensure the stability of key components during operation,the modal analysis of the key transmission structure in the device is carried out.The high-order mode has little significance to the device.The first six low-order modes are selected to analyze the mechanism,with the lowest natural frequency of 92.184Hz and displacement of 0.257mm.The working frequency of the device is far less than the natural frequency of vibration,so there is no resonance phenomenon.(4)Based on the theoretical analysis of the structure parameters and working parameters of the impurity removal device of the fresh corn ear harvester,the entity of the device is developed and processed.According to the design requirements of the test-bed,a multi parameter adjustable test device is manufactured.According to the national standard,the test indexes were determined as ear impurity content and grain breaking rate,and the bench test was carried out.It can be seen from the theoretical analysis above that the speed of fan,the speed of impurity removal roller a nd the gap between rollers have a great influence on the operation performance of the device.Therefore,the speed of fan,the speed of impurity removal roller and the gap between rollers are determined as the test factors.The design scheme of three factors and five levels quadratic regression orthogonal rotation combined test is adopted to determine the level of each test factor.The design expert software is used to determine the level of each test factor and index The data were processed,and the influence of interaction items on test indexes was analyzed.By analyzing the contribution rate of each test factor to the test index,it can be concluded that the contribution rate of each factor to the impurity content of the ear is in the order of roll gap,f an speed,impurity removal roller speed;the contribution rate to the grain crushing rate is in the order of impurity removal roller speed,roll gap,fan speed.The optimization module of design expert is used to optimize the test results.The results show that when the speed of the impurity removal roller is671r/min,the speed of the fan is 688r/min,and the gap between the rollers is 12mm,the corresponding test indexes are 1.16%of the ear impurity content and 0.49%of the grain crushing rate.The results showed that under the same experimental conditions,the hybrid percentage of ear and the broken percentage of grain were 1.19%and 0.51%,respectively.Basically consistent with the optimization results,and in line with the relevant technical requi rements. |
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