| No-tillage maize planting technology has the advantages of labor-saving,time-saving,cost-saving and efficiency-increasing.The "rush-harvest,rush-plant" of summer maize during the stubble cohesion period led to the dominant way of wheat straw smashing and returning to the field in the wheat-maize double cropping rotation system in Huang-Hui-Hai Plain of China.there are several technical problems for the traditional maize no-tillage planter when seeding in the fields covered by heavy wheat straw,such as furrow clogging,seed erection,seed drying,seedling shortage and ridging,low working efficiency,etc.In addition,the soil layer of the soil-straw complex has high firmness,the surface leveling effect of the field without rotary tillage and harrowing is poor,which can not guarantee the consistency of fertilization and sowing depth.At Present,The driven strip crushing or strip rotary tillage anti-blocking device that has been used in in agricultural production,which has large power consumption,large soil disturbance and poor flattening effect after operation,resulting in weak seedling and poor uniformity of emergence.Therefore,in the view of straw cleaning,the blocking soil leveling,and the operation reduction and efficiency increase.The vertical straw-removing anti-blocking device based on bionic vertical spiral serrated blade was designed in this paper.The main research results showed as follows:(1)The contact parameters(elastic/shear modulus,collision recovery coefficient,static/dynamic friction coefficient)of straw-straw,straw-soil and straw-tillage components were measured by direct measurement method(DEM)through analyzing the distribution characteristics of straw mulching and the physical characteristics of Shajiang Black Soil.The discrete element model of straw covered soil was constructed by using EDEM software.The disturbance characteristics,extrusion characteristics and motion characteristics of straw during the action of shovel handle of ditcher were analyzed by simulation and high-definition camera technology.The results showed that the main reasons for particle migration and accumulation in straw layer during tillage components operation were the velocity gradient,pressure gradient and resistance gradient of straw layer and soil layer along the direction of tool movement..(2)The diversion conditions of circular flow around a cylinder and the necessary conditions for the motion of the cosycloid were clarified.Based on the tooth-shaped edge curve of Mantis toes and the idea of sawtooth saw for woodworking,a vertical-axis straw-removing and blockage prevention mechanism of bionic spiral sawtooth blade was designed.With the increase of the velocity ratio of straw particles and soil particles,the transverse(longitudinal)removing of the particles increased and a band-like cleaning zone formed.When the speed of field operation is 4?8 km/h,the speed of cutter shaft is 500 r/min,the turning radius is 120 mm,the working width is 600 mm,the depth of cutter teeth is 10?20 mm,there is no blockage in the operation,and the average straw cleaning rate is 90.21%.(3)Based on the analysis of the movement behavior of tillage soil unit blocks under the action of strip tillage neutral spiral sawtooth blade,a measurement system of tillage soil geomorphological characteristics parameters was designed based on laser triangulation method to quickly and accurately acquire the topography of tillage soil before and after straw-removing and blockage prevention operation.The influence factors of surface smoothness were analyzed by DEM simulation and indoor soil trough test.Field test showed that straw-removing and blockage prevention mechanism could form a flat "U" type seeding belt in shallow tillage on "pitted" uneven surface.The better the effect of seed belt flattening was with the increase of velocity ratio.(4)The 2BMY-4 no-tillage corn seeder with straw-removing was developed,which can realize six synchronization of "straw clearing,ditch fertilization,straw mulching(soil)suppression".The effects of structural parameters(slip angle)and working parameters(rotation speed of blade axis and depth of soil penetration)on straw cleanliness,surface smoothness and power consumption were studied.The optimum combination parameters were as follows:slip angle of vertical helical saw blade was 5.16°,driving speed of blade axis was 564.02 r·min-I,and penetration depth of blade was 12.09 mm.The results showed that there was no obstruction in the seeder.The straw clearance rate was 93.87%,and the power consumption of the anti-blocking monomer was 0.50 kW.Compared with the predicted value of the software,the relative error of the straw clearance rate was 0.51%,the power consumption of the anti-blocking monomer was 0.09kW,the stability coefficient of the operation sowing depth was 93.79%,and the seedling uniformity was 94.68%15 days after sowing.(5)The results showed that strip tillage had a positive regulation effect on yield and yield components.Through the comparative experiments of performance,maize growth characteristics and yield under strip tillage(ST-Z,ST-X),straw mulching tillage(SMT-Y)and subsoiling tillage(SST),from the point of view of power consumption,the equivalent power consumption of strip anti-blocking device is less than that of straw mulching anti-blocking device,and the equivalent power consumption of anti-blocking device rotating around Z axis is lower than that of anti-blocking device rotating around Y axis.From the analysis of operation effect,the surface smoothness,soil disturbance and the depth stability of seed and fertilizer of the straw throwing and blocking device around Y side and the vertical straw shifting and blocking device around Z-axis are better than those of the belt rotary tillage and blocking device around X-axis.From the analysis of Maize Seedling characteristics,the plant height,stem diameter and main root length under strip tillage were better than those under straw mulching tillage and subsoiling tillage.The population uniformity at maize seedling stage decreased with the increase of seedbed surface roughness,and the correlation coefficient between maize seedling uniformity and surface roughness was 0.963.The results showed that the yield of Maize under strip tillage was higher than that under straw mulching tillage and subsoiling tillage,and the increase of ear number and thousand grain weight was the main reason for the increase of maize grain yield. |
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