| In order to protect and restore the "giant panda" in the-cultivated land of the black land in northeast China,the state launched the "Northeast Black Land Conservation Farming Action Plan" in 2020.Band-type less tillage and stubble removal is one of the important technical measures of conservation tillage,but the stubble removal operation has high tillage resistance and high energy consumption,and the poor separation effect of soil and straw affects the sowing belt environment,which limits the application of stubble extinguishing machine.Therefore,it is crucial to study the mechanism of reducing resistance and consumption,separation of soil straw casting and improve the environment of sowing belt.With the support of the national key R & D project(2020YFD1000903),By analyzing the research status of stubble machine at home and abroad,combined with the ridge cropping mode of corn in northeast China with straw returning to the field,using soil,straw and root stubble,aiming at reduce resistance and consumption,improve the sowing belt environment and stubble knife design.With the strip-type straight stubble cutting blade as the core component,combined with the technical methods of simulation analysis,image processing and field test.The tillage resistance,the influence of air flow on soil and straw throwing behavior,the relationship between tillage resistance and power consumption and the optimization design of stubble blade were studied.Analysis the shear force,side rotating friction resistance and airflow resistance,establish the mathematical model of the airflow-soil-straw coupling field in the field on soil and straw throwing,and obtain the tillage resistance and energy consumption model to further realize the optimal design of the stubble blade.The main studies are as follows:(1)Design of corn strip-type straight stubble-breaking bladeAiming at the problem of high energy consumption when the traditional stubble-breaking blade was used to cut stubble and broken soil,this part analyzed the stress and sliding principle of the stubble-breaking blade under the working condition,and obtains that the sliding cutting angle of the stubble-breaking blade was greater than or equal to the friction angle of the stubble or soil in contact with it,which could reduce the tillage resistance of the stubble-breaking blade;Combined with the measurement of the sliding friction angle between stubble and soil,the blade edge curve equation was determined;Further,by analyzing the stress state of stubble and measuring the friction angle between stubble and soil,the working radius of stubble-breaking blade was designed to be 230 mm.Finally,the strip-type straight stubble-breaking blade was designed by determining the geometric size of the blade,the cutter shaft and the cutter head.The finite element mode analysis and checking results showed that the strip-type straight stubble-breaking blade met the design requirements.The results of the discrete element simulation comparison test showed that compared with the driving disc cutter group,the tillage resistance of the strip-type straight stubble-breaking blade was reduced by 19.78%,and the number of soil throwing was reduced by13.95%.The field comparative test results showed that compared with the traditional L-type stubble-breaking blade,the power consumption and fuel consumption of the strip-type straight stubble-breaking blade could be reduced by 22.4% and 30% respectively.Therefore,the operation performance and effect of straight stubble-breaking blade were better.(2)Study on the tillage resistance mechanism of strip-type straight stubble-breaking bladeDuring the operation of strip-type straight stubble-breaking blade,its blade and blade rotate to form friction and impact with the air flow;The blade was squeezed laterally by soil,straw and stubble;The cutting edge formed shear with soil,straw and stubble.That constituted the total tillage resistance of the strip-type straight stubble-breaking blade.Based on the incompleteness and imperfection of this tillage resistance theory,this part analyzed the components of tillage resistance and its relationship with operation parameters in the process of straight stubble-breaking blade operation according to the field operation condition of straight stubble-breaking blade,and summarized the total tillage resistance of straight stubble-breaking blade into three parts: air flow resistance,lateral rotation friction resistance(divided into horizontal resistance and vertical resistance)and shear force.The theoretical analysis showed that the airflow resistance was affected by air parameters and operation parameters of straight stubble-breaking blade;Using the discrete element simulation test,the relationship between the horizontal resistance,vertical resistance and shear force produced by the lateral extrusion of the straight stubble-breaking blade in the operation process and the operation parameters(angular velocity and contact area)of the straight stubble-breaking blade was analyzed.It was obtained that the horizontal resistance decreased linearly with the increase of angular velocity,increased linearly with the increase of contact area,and the vertical resistance increased linearly with the increase of angular velocity,The shear force increased significantly with the increase of angular velocity,and the shear force was the main component of the three.Finally,the air-soil-straw(stubble)coupling field of discrete element method and finite element method(adding the air flow effect in the simulation)was established.Through this coupling field,the air flow resistance was 0.0883 N(the air flow resistance was 0.0815 N by theoretical calculation,with a difference of 7.7%),accounting for0.01% of the total tillage resistance;The lateral rotational friction was 97.21 N,accounting for9.81% of the total tillage resistance;The shear force was 893.496 N,accounting for 90.18% of the total tillage resistance.(3)Establishment of relationship model between tillage resistance and energy consumption of strip-type straight stubble-breaking bladeBased on the tillage resistance of straight stubble-breaking blade in Chapter 3,the relationship between the simulation test results of air flow-soil-straw(stubble)coupling field and the actual field operation energy consumption model of stubble-breaking blade was established,and the reliability of the coupling simulation model was further verified.Firstly,the tillage resistance,torque and power consumption of straight stubble-breaking blade operation in the coupling simulation model were extracted in the whole process,and the mathematical relationship model between tillage resistance,torque and power consumption in the coupling simulation model was established.The results showed that it was basically consistent with the relationship model of tillage resistance,torque and power consumption in theory.Secondly,the power consumption of the straight stubble-breaking blade in the field test was tested.The power consumption range of the field test was 14 k W-30 k W,and the power consumption range of the coupling simulation was 15.8k W-24 k W.The average power consumption of the straight stubble-breaking blade in the coupling simulation was 20.14 kw,and the average power consumption of the straight stubble-breaking blade in the field test was 22.28 k W.Compared with the coupling simulation test,the power consumption of the field test was increased by 10.63%.Finally,the oil consumption of the straight stubble-breaking blade in the field test was tested,and the output results of the oil consumption were processed in units of 0.01 s,which corresponded to the tillage resistance and power consumption in the coupling simulation test.The mathematical relationship model between the tillage resistance and torque of the straight stubble-breaking blade in the coupling simulation test and the oil consumption in the field test was established.(4)Study on throwing behavior of soil and strawAir flow was very important to the throwing behavior of soil and straw,but the field experiment could not explore its micro behavior.Based on the vacuum state(no airflow was added to the simulation)of the existing discrete element simulation research,this part used the coupling field model in the study of tillage resistance mechanism(considering the influence of air flow)to study the throwing behavior of soil and straw during the operation of strip-type straight stubble-breaking blade.The velocity and displacement(lateral,vertical and longitudinal)of surface straw and soil particles at different depths under different angular velocity,vacuum and air flow conditions were analyzed respectively.The simulation results showed that with the increase of the angular velocity of the straight stubble-breaking blade,the lateral displacement,lateral velocity,longitudinal displacement and longitudinal velocity of soil and straw would increase significantly.Increasing the angular velocity of the straight stubble-breaking blade could significantly increase the disturbance and scattering of soil and straw;With the increase of soil depth,the lateral displacement and lateral velocity of soil would decrease significantly;The air flow could significantly increase the lateral displacement of soil and straw,and with the increase of the angular velocity of the straight stubble-breaking blade,the air flow increased,which could further increase the lateral displacement of soil.During the operation of straight stubble-breaking blade,the shallow soil particles would fall and the deep soil particles would rise,forming the exchange of deep and shallow soil and realizing the change of soil layer.The field high-speed camera verification test showed that when the angular velocity of the strip-type straight stubble-breaking blade was 75.36 rad/s,the difference between the field verification test and the coupling simulation test in the displacement and velocity(longitudinal)of soil and straw was 7.3%,7.6%,17.9% and 17.7% respectively.The optimal working condition was that the angular velocity of the straight stubble cutter was 56.52 rad/s,with the effect of air flow,and the optimal sowing belt width was 204.92 mm.(5)Optimum design of strip-type straight stubble-breaking bladeBased on the research on the farming resistance mechanism of strip-type straight stubble-breaking blade in chapter 3 and the research on the throwing behavior of soil and straw during the operation of strip-type straight stubble-breaking blade in chapter 4,the parameters of strip-type straight stubble-breaking blade were optimized,so as to realize the low consumption and high-quality operation effect of strip-type straight stubble-breaking blade.The test factors affecting strip-type straight stubble-breaking blade operation were determined as stubble-breaking blade speed,soil penetration depth and forward speed.The factor levels were determined as 28-84rad/s,80-120 mm,0.5-0.86 m/s,respectively.Taking the power consumption of strip-type straight stubble-breaking blade,soil disturbance,lateral disturbance of straw and stubble breaking rate as the experimental indexes,the coupling simulation test of 3 factors and 5 levels orthogonal rotation combination of straight stubble-breaking blade was carried out.The test results showed that when the rotating speed of the straight stubble-breaking blade was 43.47 rad/s,the soil depth was 101.1mm and the working speed was 0.57 m/s,the power consumption was 16.98 k W,the amount of soil disturbance was 293.09,the lateral disturbance of straw was 173.84,and the stubble breaking rate was 93.76%.The results of normal test and independent sample T-test showed that under this operation parameter,the power consumption of strip-type straight stubble-breaking blade obtained in the field verification test was 17.22 k W and the stubble removal rate was 93.19%,which were not significantly different from the results of coupling simulation test,so the modeling of coupling simulation test was reasonable.Compared with rotary tillage cutter,the power consumption of strip-type straight stubble-breaking blade was reduced by 17.8%,the oil consumption was reduced by 19%,the soil disturbance was reduced by 70.2%,the lateral disturbance of straw was reduced by 1.5%,and the stubble breaking rate was reduced by 2%;Compared with L-type stubble-breaking blade,the power consumption of strip-type straight stubble-breaking blade was reduced by 31.6%,the oil consumption was reduced by 32.3%,the soil disturbance was reduced by82%,the lateral disturbance of straw was reduced by 2.9%,and the stubble breaking rate was reduced by 2.8%.However,the results of one-way ANOVA showed that although the power consumption,oil consumption and soil disturbance of strip-type straight stubble-breaking blade were significantly reduced compared with rotary tillage cutter and L-type stubble-breaking blade,there were significant differences among them,there was no significant difference in straw lateral disturbance and stubble breaking rate among strip-type straight stubble-breaking blade,rotary tillage cutter and L-type stubble-breaking blade.And the lateral disturbance and stubble breaking rate of straw were basically the same.Therefore,the optimized strip-type straight stubble-breaking blade could not only improve the operation performance,but also ensured better operation effect and met the requirements of agricultural operation. |
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