| Maize is one of the main food crops in our country.As a major maize producing region of China,the seeding of maize in Heilongjiang province is mainly direct seeding in the field.In order to improve the quality and yield of maize,the northern cold region began to adopt the method of bowl-seeding.The existing precision seeding device is of high precision,but the structure is more complicated.How to make the seeding device both simple and precise is an important subject.For this,according to the demand of mechanization and planting of maize plant,on the base of the developed maize plant fiber cupulate compartment tray,using theoretical analysis,modeling simulation and experimental research methods.The physical characteristics of maize seeds,improved design of pneumatic cylinder seeding device,the internal flow field of the seeding device and vibration principle of components in the seed box were studied in depth.(1)The physical and mechanical characteristic parameters of maize seeds Zhengdan958 were determined and calibrated.These parameters are the important basis for the structural design and optimization of sowing device.(2)The structure and size of the seeding device were determined according to the physical characteristics of seeds and the requirement of maize plant.The radius of the suction cylinder is 100 mm and the wall thickness of the cylinder is 1 mm.The number of holes on the circumferential direction is 12,the number of holes on the axial direction is 6,the interval of holes is 45.5mm,and the diameter of the suction hole is 5.5mm.(3)The flow field is determined as turbulent flow field according to the actual working conditions by using FLUENT.The ?-? model is adapted as mathematical model of in-core flow field of the hollow shaft.The results show that the pore diameter and the interval of holes have significant influence on the distribution uniformity of internal flow field.The simulation results show that,the adsorption capacity of the cylinder suction hole is the highest when the interface pressure is-12 kpa,and the pore diameter and the interval of holes are 10 mm and 50 mm respectively.(4)The gas nozzle cleaning device was designed;A mathematical model of the clearing process was established and the range of wind pressure for clearing was determined.(5)The isolating pressure roller with adjustable installation angle was designed.The relative rolling mode is adapted to reduce the friction instead of the original relative sliding mode between isolating pressure roller and the inner wall of the cylinder.Zero speed seed dropping can be realized by adjusting the installation angle of isolating pressure roller.It can improve the working performance of seeding device effectively proved by theoretical analysis and comparative experiments.(6)Though mechanical analysis of the seeds filling process of the seeding device,negative pressure,forward velocity and seeds suction angle were carried out as the main factors affecting the performance indexes.Through single factor test,the range of three factors was determined based on the performance index of the seeding qualified index,the miss-seeding index and the reseeding index.(7)The main order of the influence of the seeding qualified index of the forward velocity,negative pressure and seeds suction angle is obtained as negative pressure,forward velocity and seeds suction angle by orthogonal experiment.However,after data optimization,the miss seeding index is relatively high.It is found that the flow characteristics in seeds box has certain effect on seed filling performance by many experiments?(8)The influence mechanism of vibration on seed dispersal is analyzed,the seed motion equation was established,the effect of layer height,vibration frequency and vibration angle on the seeds filling performance were simulated using EDEM.The results showed that the seeds filling performance of seeding device was improved with the increase of population perturbation strength and seeds supply height.(9)The main order of the influence of the seeding qualified index of seeds layer height,vibration angle and vibration frequency is seeds layer height,vibration frequency and vibration angle by quadratic orthogonal rotation combination test method.The optimal seeding performance is obtained as vibration Angle 45°,vibration frequency 116-122 Hz,and seeds layer height 96-117 mm by test data process using DESIGN-EXPERT.In this case,the qualified index is 95.6%,the miss seeding index is 1.5%,and the reseeding index is 2.9%. |
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