| China is a large country in potato production and consumption.With the increasing of demand,the planting area and scale of potato are increasing dramatically,so it is particularly important to improve the level of potato mechanization.Mechanization of potato harvesting is a key link in the whole process of mechanization of potatoes,which can improve labor efficiency and increase yield and income.At present,the mechanized harvesting forms of potato are mainly divided into joint harvesting and sectional harvesting.Most of the developed count ries adopt potato combine harvester for harvest operation.The machine has multiple and multi-stage transporting and separating devices,and the separation effect of potato soil is better.However,it is not suitable for clay loam operations and small plot operations in northern China.Domestically,the harvesting form of segmental harvesting is mainly used,and there are many types of harvesting machinery under the condition of clay loam in northern China.At the same time,the quality of harvesting machinery varies greatly,generally there are some problems such as poor separation effect of potato soil,and the decrease of transportation capacity of transportation and separation device,which results in secondary burial after excavation,and then leads to the low rate of tuber of machinery and tools.In view of the above problems,this study carried out the design research on the rod conveyor chain conveyor separation device,The main contents are as follows:(1)the specific harvest conditions of potato harvest period,including soil physical characteristics(soil type,moisture content,firmness,etc.),potato planting information(variety,ridge height,ridge spacing,plant spacing),the growth state of potato(depth of tuber,density of tuber,size and mass of potato block)provided key basic parameters for theoretical analysis and design of transportation and separation device.(2)According to the determination and analysis of the specific potato harvesting conditions,understood the overall structure,composition and conveying separation principle of the potato digger separation and transportation device widely used at home and abroad at present,combined with its advantages and disadvantages and harvesting requirements.The overall scheme of the transport separation device and the structural design of the key components are determined,including lift bar spacing,bar diameter,bar configuration and jitter.(3)Theoretically explore the movement laws of the elevator chain and the mixture of potato and soil moving on the elevator chain,including the movement of the transporting separation device and the movement separation of the potato and soil mixture on the device,soil fragmentation and soil screening.The main factors affecting the separation effec t of potato soil and the range of working parameters of the key components were determined.(4)Combined with the actual harvesting process,the discrete element numerical simulation of the designed transport separation device is carried out by using the E DEM software to determine the optimum working face length of the second stage lift and transport chain,and the rationality of the structural parameters determined by the theoretical analysis institute is verified at the same time.(5)Conduct field trials in accordance with the test methods specified in relevant national standards,test evaluation index based on exposed potato rate and broken skin rate.According to the theoretical analysis of the main factors affecting the separation effect of the potato soil and the level range of the factors,the field actual experiment research was carried on.On the one hand,the influence of various factors on the separation performance of the separation unit was explored,and the best combination of parameters is sought.The mathematical model of the relationship between the evaluation index and the factors was established.The experimental results were analyzed and the structural parameters of the plant were optimized to obtain a more reasonable device structure which could meet the requirements of enhancing the separation effect of potato soil.On the other hand,the verification test was carried out to carry out large-area operations,and the harvesting effect was measured to verify whether the device satisfied the operation requirements of the northern clay loam.The results are as follows:(1)Through the measurement and analysis of the growth characteristics of the potato field and the basic physical characteristics of the soil,considered the application range,a dvantages and disadvantages and working principle of the existing transporting separation device,combined with the design requirements and operation requirements of the potato digger transporting separation device,determine The overall scheme of the conveying and separating device is a two-stage bar lifting chain type,adopting a structure with a rod type lifting chain,and the double-row lifting chain has a working width of 1700 mm,and the first-stage lifting bar spacing is 48 mm.The second-stage lifting bar has a spacing of 44 mm and the bar diameter is 11 mm.The straight-bend-bend-straight bar configuration is designed.The curved bar and the straight bar form a groove depth of 18 mm,which is used to enhance the separation of the conveying separation device.Capability,design of the active double-roller type shaker,and finally determined that the maximum amplitude of the shaker operation is 60 mm,the setting roller diameter is 80 mm,and the working circumference radius is 100 mm.(2)The key motion parameters were determined by analyzing the movement of the chain conveyer in the working process,and the frequency of the jitter is determined to be 4~8Hz,and the main factors affecting the separation effect of potato soil were determined.In addition to t he physical properties of the soil itself,include the working line velocity of the lift ing chain,the forward speed of the device,the amplitude of the jitter and the frequency of the jitter.The above results provided a theoretical reference for the nume rical simulation and experimental research of discrete element.(3)The discrete element simulation analysis of the transport separation device was carried out,and the simulation was carried out by using EDEM software.The three-dimensional solid model,soil particle model and potato model of the transport separation device were established,and the particle factory and boundary conditions were set to simulate the harvest of the ridge in the field.Taking a certain normal working condition as an example,the simulation determined that the optimal working length of the second-stage elevator chain was 1.2m.The results showed that the designed elevator chain transport separation device had good working performance.(4)Through the field experiment,it is verified that the lifting chain potato digger transport separation device can solve the problem of poor separation effect of potato soil.The field experiment determined the best working parameters,the jitter frequency was 5.2 Hz,the shaker amplitude was 52 mm,the machine forward speed was 1.2 m/s,and the lifting chain speed was 1.6 m/s.The corresponding optimized test indicators included the exposed potato rate is 98.0% and the skin breaking rate is 1.3%,which is obviously better than the national standa rd.The separation effect of the potato soil was improved and the operation requirements was satisfied by the chain transportation separation device adjusted by the optimized parameters.The lifting chain potato digger transport separation device designed can effectively improve the separation effect of potato soil in the northern China,which provides technical reference and theoretical support for the design and optimization of the lift ing chain transport separation device. |
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