Numerical And Experimental Investigation Of The Counter-Rotating Straw Returning Device Based On DEM

Straw returning to the field plays an important role in cultivating soil fertility,storing water and preserving moisture,saving time and energy.Counter-rotating straw returning device has the advantages of straw returning,good effect of stubble crushing and high quality of land preparation.But currently on the market,the counter-rotating straw returning device has some disadvantages such as obvious heaping soil,serious winding grass,high energy consumption.From the actual,the traditional returning device was improved through theoretical analysis and simulation experiment.The rotary tillage blade was optimized based on the prototype rotary tillage blade,and a kind of the anti-heaping soil component and anti-winding grass component were designed.The reliability of structure optimization and simulation results was verified by the field test,which provided a reference for the structure design of the counter-rotating straw returning device.Main works were summarized as follows:(1)According to the counter-rotating straw returning device has some problems such as high energy consumption,obvious heaping soil,severe winding grass,analyzed the working principle of the counter-rotating straw returning device,the trajectory of rotary tillage blade and structural parameters,and determined the main factors affecting the quality of work and power consumption and the knife roller speed,rotation speed,single blade working width and bending angle.(2)According to the characteristics of reverse rotation mode,the herringbone pattern which suitable for reverse rotation stubble was adopted.In view of the serious problems of heaping soil in front of the knife roll and winding grass on the knife shafts and the knife seats,a kind of anti-heaping soil component was designed under the soil retaining cover and a kind of sliding cutting knifes were installed on the knife seats.According to the designed parameters such as working width and the advantages of side drive,the side drive was selected as the power drive mode of the counter-rotating straw returning device,and the supporting power was determined by calculating the transmission ratio.(3)Based on discrete element software EDEM,a virtual simulation model of the counter-rotating straw returning device was established,and the field returning operation was simulated.The torque value of the counter-rotating straw returning device and the quality of work after tillage were analyzed through the post-processing module.Working in the knife roller speed,rotation speed,single blade working width and bending angle for factors,in straw burial rate and power consumption for assessment indicators,the orthogonal experiment design method was used to carry out the optimization simulation experiment with 4 factors and 3 levels,and using the range analysis and variance analysis,the best combination of parameters were single blade working width 65 mm,bending angle 120°,knife roller speed 1.1 m/s,rotation speed 230 r/min.(4)The field operation comparison test of the counter-rotating straw returning device was carried out,the power consumption and the operation quality data of the machine were measured and compared.Test results showed that the average power consumption of the optimized knife roller B with the anti-heaping soil component and the prototype blade and the optimized knife roller C with the anti-heaping soil component and the optimized blade than the prototype knife roller A with prototype blade and no anti-heaping soil component were reduced by 9.34%and 14.0%respectively,which shows the anti-heaping soil components and optimized blade were the effective in reducing energy consumption.It can be known from the analysis of winding grass of knife roller that half of the roller installed with slide cutting knifes has almost no winding grass,while the other half without slide cutting knifes has very serious winding grass.In terms of operation quality,the qualified rate of tillage depth(92%,92%and 96%),straw burial rate(85.43%,89.06%and 90.02%)and soil crushing rate(85.08%,86.44%and 85.77%)of the three groups of A,B and C all meet the test requirements and national industry standards,and the operation quality of optimized knife roller B and C is obviously better than that of prototype knife roller A.