| The Mid-lower Yangtze River in China is One of the most significant plating zones of rapeseed,which estimation about 85% planting area of the oil-bearing crops.Because of the areas of Mid-lower Yangtze River is rice-oil rotation and more rain,The combined harvest of rapeseed harvester at one time can effectively save agricultural time,save time and effort.The working performance of rape combine harvester directly impacted by the cleaning performance of cleaning system.To solve the problems of the adaptability to feeding quantity needs to be improved and high loss rate and low cleaning rate of cleaning device for rapeseed combine harvester.Material characteristics and aerodynamic characteristics of rape threshing mixture in suitable harvest period,two cleaning schemes of Brachistochrone cleaning cylinder and diversion type double cylinder are proposed.The calibration and experiment of characteristic parameters and contact parameters of rape threshing mixture were carried out.The characteristic parameters of rape stalk and the contact parameters between different materials were measured and analyzed.Based on calibration parameters,the DEM-CFD simulation analysis of the diversion type double cylinder cyclone separation cleaning device and the Brachistochrone cleaning cylinder was carried out.The motion trajectory of rape threshing mixture and airflow field distribution in cyclone separator cleaning cylinder were obtained.The trajectory is verified based on high-speed photography technology.It gives reference to improvement and optimization of cyclone separation cleaning device for rape combined harvest.This paper mainly research contents as following aspects:(1)Based on the systematic comparative analysis of the research progress of Cyclone separation cleaning technology at home and abroad,the flow characteristics between the rape threshing mixture and the characteristic parameters of rape stalks were tested and analyzed.Provides basic simulation parameters for DEM-CFD coupling simulation.(1)The rapeseed material of “Huayouza 62”’with suitable harvest period was taken as the research object.The radial global compression of rape stalk was carried out.The results showed that the average values of Poisson ’s ratio,elastic modulus and shear modulus are0.45,4.44 MPa and 1.53 MPa,respectively.(2)By using high-speed photography technology,free drop test and slant method,the collision recovery coefficient and static friction coefficient between rapeseed materials and between rapeseed materials and steel plate are tested and analyzed,which provides basic characteristic parameters and contact parameters for rapeseed material particle model.(3)Based on EDEM,the contact parameters of rape stalks were calibrated by repose angle,the repose angle curve is fitted by MATLAB.The regression models of stalk-stalk static friction coefficient,stalk-stalk dynamic friction coefficient and stalk-steel plate dynamic friction coefficient with response angle were obtained by experimental optimization.the optimal combination was 0.707,0.015 and0.012.The relative error of stalk repose angle under the optimal combination parameters was 0.54%.(4)A three-dimensional model of rape stalk,rapeseed pod and rapeseed was established by particle combination in EDEM.Based on the characteristic parameters and contact parameters,DEM-CFD simulation test and bench verification test were carried out.In the gas-solid coupling simulation test and bench test,the relative errors of rapeseed cleaning rate and loss rate were 2.81% and 7.48%,respectively.(2)The adaptability of the feeding quantity of the cyclone separation cleaning device for rape combined harvest needs to be improved,and the loss rate is high and the cleaning rate needs to be improved.Combined with the aerodynamic characteristics of rape threshing mixture,a diversion type double cylinder cyclone separation cleaning device with flow guide effect and secondary settlement of rapeseed in mixture was developed.(1)The key parameters analysis of the diversion type double cylinder cyclone separation cleaning device.Through analysis,the diameter of the impeller in blower is 300 mm,The minimum rotational speed of the blower is 569 r/min.According to the flow requirements in the double-cylinder type of cyclone separation cleaning device and the aerodynamic characteristics of the rape threshing mixture,the diameter of the cleaning cylinder and discharge port and MOG outlet was 400 mm and 150 mm and 160 mm,respectively.The 6-46 Centrifugal fan is selected as the suction fan,the inner diameter of the buffer section and the taper angle of the suction tube are 280 mm and 20 °,respectively,the bending angle of the joint is 90 °.The pitch,height and width of the tapered external extension type shaftless spiral blade are 200 mm,300 mm and 40 mm,respectively.(2)Based on kinematics and dynamics,simple movement differential equation of the rapeseed in the Diversion type lower cone was constructed,and the major factors affecting the rapeseed movement in the Diversion type lower cone were clarified.(3)Based on DEM-CFD,the material motion trajectory and airflow field distribution in the double-cylinder type of cyclone separation cleaning device were simulated.The results of the simulation indicated that the vegetable grain will flow out or accumulate near the discharge port directly from the discharge port,and the waste will be sucked away by the high-speed airflow in the middle section.The secondary settling cylinder can clean the sucked waste twice.The distribution points were selected at the suction and discharge outlets,and the airflow velocity of the distribution points was measured and analyzed by the thermal airflow velocity meter.The relative difference between the airflow velocity in the physical test and the airflow velocity in the simulation test was 4.17%～9.61%.(4)Analysis of the cleaning performance of the diversion type double cylinder cyclone separation cleaning device based on a single factor experiments and the quadratic rotation-orthogonal combination test.The results of the single factor experiments indicated that when the feeding quantity increased from 0.6 kg/s to 1.0 kg/s,the cleaning rate gradually decreased and the loss rate fluctuated.The optimal range of the rotational speed of the blower and the speed of the suction fan is550 r/min～750 r/min and 1400 r/min～1800 r/min,respectively.In this study,a response surface optimization approach was employed to establish the optimal operating conditions for a diversion type double cyclone separator.Specifically,the feeding quantity of 0.71 kg/s,the blower rotation speed of 616 r/min,and the suction fan speed of 1667 r/min were identified as the optimal parameters for achieving high cleaning rate and low loss rate.The resultant cleaning rate and loss rate were found to be 93.09% and 4.69%,respectively.(5)The results of the field test indicated that the components of the diversion type double cylinder cyclone separation and cleaning device can operate normally and smoothly in the field.The cleaning rate is 92.39 % and the loss rate is 4.80 %.(3)Under the premise of maintaining high cleaning rate and low loss rate,To improve the adaptability of the cyclone separation cleaning device to the feeding quantity,based on the trajectory of the rape threshing mixture in the cyclone separation cylinder,a kind of Brachistochrone cleaning cylinder is designed by principle of Brachistochrone.(1)Based on the high-speed photography technology,the trajectory of the rape threshing mixture in the conical cylinder is analyzed,and a kind of Brachistochrone cleaning cylinder which can improve the adaptability to the feeding amount is designed.The diameter of the cleaning cylinder is determined to be 450 mm,the outlet diameter was240 mm,The diameter of the MOG outlet was 200 mm.its parameter equation is determined.Based on the kinematic analysis of the rape threshing mixture in the Brachistochrone cleaning cylinder,the experimental factors affecting the rape threshing mixture velocity were determined.(2)Based on DEM-CFD,the simulation analysis of the fastest descending cyclone separation cleaning cylinder was carried out.Through the simulation results,it was observed that after the material moved along the inner wall for a period of time,it would gather in the fastest descending cone and fall directly from the material outlet,which shortened the movement time of the material inside the cyclone separation cylinder.(3)Conducted Single factor experiments and mixed-level orthogonal experiments.when the feeding rate increased from 0.6 kg/s to 1.0 kg/s in Brachistochrone cleaning cylinder,When the airflow velocity at the MOG outlet and the airflow velocity at the outlet are 9.19 m/s～13.12 m/s(1400 r/min～1800 r/min)and 4.84 m/s～7.94 m/s(550r/min～750 r/min),respectively,the cleaning performance is better.The orthogonal test results show that: When the feeding quantity is 1.0 kg/s,the airflow velocity of the outlet is 5.68 m/s～5.93 m/s(rotational speed 600 r/min)and the airflow velocity of the MOG outlet is 12.08 m/s～12.41 m/s(rotational speed 1600 r/min),the cleaning performance of the fastest falling cleaning cylinder is the best.The cleaning rate of the cleaning bench test was 93.32 %,and the loss rate was 4.52 %. |
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