| China has a vast agricultural area and a large amount of straw.The burning or idle straw has caused serious environmental pollution and huge economic losses annual.In recent years,the application of straw returning technology has greatly alleviated the problem of straw burning and promoted the sustainable development of agriculture in China.At present,straw returning machinery has been widely used,but there are still some problems in straw returning operation,such as low mechanization level,high power consumption,poor operation and the operation mechanism is not clear quality.Aiming at the existing problems of straw returning machine in paddy field,a multi-phase coupling simulation model of rotary roller-straw-soil was established,the interaction process among straw returning roller,soil and straw was deeply analyzed by the Finite Element Method(FEM)and Discrete Element Method(DEM)co-simulation method.Four factors and three levels orthogonal test was carried out,and the regression analysis of numerical simulation test results was carried out,and the simulation test results were verified by soil trough test.The main research contents and results are as follows:(1)The biomechanical properties of wheat straw were studied.The shear stress-displacement curve and tensile strength-strain curve of wheat straw with different cross-sectional area and moisture content were measured,and the shear strength,tensile strength and tensile modulus of wheat straw were obtained.The experiment of wheat straw slicing was carried out.The results showed that the ratio of Sclerenchyma thickness had a significant effect on the tensile modulus of wheat straw.The rheological properties of soil slurries with different water content were tested and analyzed.The results showed that the viscosity of soil slurries with 25%,30%,35%and 40% water content were 2724.79Pa·s,1448.39Pa·s,518.26Pa·s and 35.89Pa·s,respectively.(2)Dynamic analysis of straw returning roller.The kinematics model of straw returning roller was established,and the relationship between working resistance and working parameters was analyzed.The force model of rotary tiller blade was established,and the power consumption model of straw returning roller was established and analyzed.Rotary speed,tool bending angle,soil viscosity and rotary depth were selected as the influencing factor.(3)Simulation analysis and optimization of the operating performance of the straw returning roller.Based on the FEM and DEM co-simulation method,a multi-phase coupling simulation model of rotary roller-straw-soil was established,the parameters of straw returning roller were optimized.Four factors and three levels orthogonal test were carried out.The range analysis,variance analysis and regression analysis were used to obtain the optimal parameter combination of straw returning roller: the rotary speed was 280.39m/s,the rotary depth was 15cm,the bending angle was 70° and the soil viscosity was 30Pa·s.Under this condition of the optimal parameter combination,the blade torque was 11.47N·m,the soil disturbance rate was 73.21%,and the straw coverage rate was 81.18%.(4)Soil trough verification test of working performance of straw returning roller was performed.According to the optimal combination of parameters,the soil trough test was carried out to test the rotary blade roller torque,surface roughness,broken soil rate and straw coverage rate.The results show that the error of the average torque between soil trough test and simulation test is 4.65%;the error of the straw coverage rate between soil trough test and simulation test is 5.49%,which means that the simulation results are basically consistent with the soil trough test result. |
PDF Full Text Request