| Artemisia selengensis is a special health vegetable in China.It is very popular among consumers because of its fresh taste and crisp taste.However,the mechanization level of Artemisia selengensis production is low,and the key links such as planting,harvesting and leaf removal are still dominated by manual operation.The cost of production remains high,which seriously restricts the development of Artemisia selengensis industry.The defoliation of Artemisia selengensis is the most labor intensive link in its production process,with labor time accounting for 60% ～ 70%,and the labor cost accounts for more than 50% of the total income of Artemisia annua cultivation.In order to solve the above problems,this paper tests and analyzes the geometric and mechanical physical characteristics of Artemisia selengensis plant,compares and analyzes the process schemes of mechanical leaf removal and pneumatic mechanical combined leaf removal,develops a pneumatic mechanical combined Artemisia selengensis leaf removal machine,optimizes the structural parameters of the separation drum assembly based on CFD simulation,and carries out the research on the rotation speed of the separation drum,the rotation speed of the leaf removal roll,the height of the counter roll The operation parameters of Artemisia selengensis leaf remover were optimized by single factor test and orthogonal test of feeding speed.The work of this paper is as follows:(1)The geometric and mechanical properties of Artemisia selengensis in the suitable harvest period were tested and analyzed.On the basis of an analysis of the research status of stem leaf separation technology and equipment at home and abroad,taking Artemisia selengensis at the suitable harvest stage as the research object,the geometric characteristics of Artemisia selengensis plant,the sliding friction characteristics of leaves,the connecting force between stems and leaves and other mechanical and physical characteristics were statistically analyzed.The distribution range of the total number of leaves,the number of leaves to be removed,the plant height,the height of leaves left,the diameter of root tip,the diameter of leaves left and leaf are [12,18],[7,14],[363,492]mm,[290,421]mm,[4.52,6.81]mm,[2.78,4.10]mm and [12.6,36.92]cm~2 respectively;The mechanical and physical characteristics show that the the bending strength of Artemisia selengensis stem is11.23 MPa,the minimum radial pressure resistance of the stem is 10.5N,the reverse stem leaf connection force of Artemisia selengensis is the smallest,and the reverse pulling is easier to remove the leaves of Artemisia selengensis.(2)The mechanical blade removal process is compared with the mechanical blade removal process.Combined with the geometric parameters and mechanical and physical characteristics of Artemisia selengensis,two mechanical leaf removal schemes and one pneumatic mechanical combined leaf removal scheme were proposed,and the feasibility experiment was carried out on the bench.It is found that:(1)The roller comb type leaf removal method can initially realize the leaf removal function of Artemisia selengensis.When the Pu rod is used as the brush tooth,the stem damage of Artemisia selengensis is small,but the leaf removal effect of the device is poor,and the leaf removal rate is less than20%.When the brush is used as the brush tooth,the leaf removal rate has been significantly improved,but the brush will cause partial damage to the stem and leaf of Artemisia selengensis;(2)Combing brush and pulling combined Artemisia selengensis leaf removal method combines combing brush separation with pulling leaves.The leaf removal effect of Artemisia selengensis has been significantly improved.The leaf removal rate of the device is more than 80% and the stem damage rate is less than 5%.However,this method still has the phenomenon of missing leaves and leaf fracture.After repeated combing and brushing,the water is discharged from the surface of the missing leaves;(3)The results of the combined pneumatic and mechanical leaf removal scheme of Artemisia selengensis show that the method of pneumatic blade guidance and mechanical leaf removal solves the problems of unstable blade pulling and water from combing and brushing,and the stem damage rate of Artemisia selengensis is 0,and the leaf removal rate is more than 90%.The device meets the leaf removal requirements of Artemisia selengensis.Comprehensive analysis of the above three experimental conditions,it is determined to select the pneumatic mechanical combined leaf removal scheme of Artemisia selengensis.(3)A pneumatic mechanical combined Artemisia selengensis leaf remover and its supporting key components have been developed.According to the working principle of the machine and the leaf removal requirements of Artemisia selengensis,it is clear that the minimum working efficiency of the leaf removal machine is 10 kg / h,the reciproc ating stroke of the feeding device is 30 mm,and the minimum clamping length is 82 mm.On this basis,a pneumatic mechanical combined Artemisia selengensis leaf remover is developed.Through test and analysis,it is determined that the air chamber structure of wrapped shaft is selected for the separation drum assembly;Combined with the geometric and mechanical physical characteristics of Artemisia selengensis,the theoretical analysis and structural design of separation drum assembly,defoliation roller assembly and auxiliary feeding device are carried out.Determine that the diameter of the separation drum is 133 mm,and the length of the ventilation hole of the separation drum is 270 mm,the circumferential distribution of vent is 36,and the axial spacing is 10mm;The stripping roller is provided with a strip-shaped protrusion structure to reduce blade adhesion.Through theoretical analysis,it is concluded that the relative installation height of the opposite roller is less than49 mm.In order to reduce the influence of subjective factors during feeding,a feeding device with adjustable parameters is designed,which can realize the reciprocating feeding and horizontal turnover of Artemisia selengensis.(4)Based on Fluent software,the flow field inside the separation drum assembly is simulated and analyzed.The effects of three different shapes of vent holes: straight hole,conical hole and slotted hole on the wind pressure,wind speed and its distribution uniformity of the air flow field are simulated.The simulation results show that it is better that the ventilation holes of the separation drum are straight holes;Taking the diameter,number and depth of vent holes of the separation drum as the influencing factors,and taking the single hole adsorption capacity and flow rate of vent holes as the experiment indexes,the simulation experiment is carried out.Through the analysis of variance,it is determined that the size of vent holes of the separation drum is 4mm,the depth of vent holes is 4mm and the number of vent holes is 121.The simulation experiment of turbulent energy dissipation of airflow field is carried out on three forms of air chamber end caps.It is found that the turbulent energy dissipation of single pipe straight end cap is the smallest.Therefore,the connection mode of single pipe straight end cap is selected between the separation drum air chamber and the fan.To meet the strength requirements of the separation drum end cover,the single pipe straight end cap is statically verified.(5)The performance experiment of Artemisia selengensis leaf remover was carried out.Taking the rotating speed of separation drum,the rotating speed of defoliation roller,the feeding speed and the relative height of opposite roller as the experiment factors,and taking the defoliation rate and blade fracture rate as the experiment indexes,the single factor test was carried out.The test results showed that with the increase of rotating speed of separation drum,the leaf removal rate showed a trend of increasing and then tending to be stable,and the leaf breakage first decreased and then increased;With the increase of the rotating speed of the defoliation roller,the defoliation first rises and then tends to be stable,and the blade fracture first decreases and then rises;As the relative height between the separation drum and deleafling roller shafts increases,the leaf removal rate continued to decline,and the blade fracture decreased first and then increased;With the increase of feeding speed,the defoliation first decreased slowly and then decreased rapidly,and the blade fracture rate continued to rise slowly.The single factor experiment indexes determines the optimal parameter range of separation drum speed,defoliation roller speed and feeding speed.On this basis,taking the maximum leaf removal rate,minimum blade fracture rate and maximum working efficiency as indexes,the BBD orthogonal test was carried out.It is concluded that the optimal combination of operating parameters of the whole machine is separation drum speed 78.2r/min,defoliation roller speed 64.9r/min and feeding speed 41.6mm/s,The leaf removal rate and leaf breaking rate of Artemisia selengensis are 94.6% and 13.3% respectively. |
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