| Rice is one of the most important food crops in China.Appropriate and effective application of fertilizers during rice growth is an important measure to increase rice yield and reduce environmental pollution.At present,the fertilization of rice in China is basically completed by artificial application.The backward fertilization method not only reduces the utilization rate of fertilizers,resulting in increased fertilization without increasing production,and fertilizers that have not been absorbed by crops can also lead to a series of ecological and environmental problems such as eutrophication,soil compaction,and acidification.Therefore,in the rice production,it is necessary to study scientific and reasonable fertilization techniques to achieve the effects of fertilizer saving,production increase,and environmental protection.Deep application of fertilizers to the roots of rice can increase the concentration of nutrients near the root zone,reduce nutrient supply time,and increase fertilizer utilization.The existing deep fertilization techniques for rice are mostly concentrated on deeper fertilization in the plug(sowing)side,and are mainly based on solid fertilizers.However,the viscosity of solid fertilizers becomes larger after moisture,which can easily block equipment,causing unequal fertility and can’t even row fertilizers.Compared with solid fertilizer,liquid fertilizer has the advantages of high absorption and utilization,good fertilizer efficiency,precise distribution ratio,and easy mechanical application.Therefore,in order to solve the problem of blockage of fertilizer applicators,this paper combines the advantages of liquid fertilizers to develop a pneumatic injection type deep application device for liquid fertilizers,and carries out theoretical research,structural design and experimental analysis of its key components and overall devices.The main research contents are as follows:(1)According to the operating characteristics of paddy fields and the technical requirements of mechanical fertilization,the structure of the pneumatic injection deepliquid fertilizer application device was designed.Set up a multi-functional soil test bench to imitate the working environment of paddy fields.According to the agronomic requirements of rice mechanical fertilization,combined with the rheological properties of paddy soil,the structural design of the pneumatic injection deep liquid fertilizer application device was completed,mainly including the pneumatic injection type fertiliser and the imitating slide knife type opener.The fertilizing device is installed on a rice transplanter or a paddy field tiller and weeding machine can simultaneously perform deep side fertilization and top dressing operations.Set up a multi-functional movable soil trough test platform driven by a stepper motor,which can easily imitate the paddy field environment and provide the basis for experimental research of openers.(2)According to the working principle of the ejector,the inner cavity structure of the fertiliser device is designed,and the performance test platform for the pneumatic ejector fertiliser is constructed.In combination with the requirement of rice fertilization,the structural parameters of the fertilizer are optimized.Design the inner structure of the fertiliser and determine its relevant structural parameters.The full factor test method was used to test the throat distance,outlet diameter and system working pressure of the fertilizer applicator,and the fertilizer applicator work performance test was conducted with the amount of fertilizer and air consumption as experimental indicators.The results showed that when the throat distance is 1mm,the outlet diameter is 3.5mm,and the gas pressure is 0.3Mpa,the fertilizer was maximally 11.26g/s,and the gas consumption was 26L/min,which satisfied the agronomic requirements for rice.The throttle valve calibration test was conducted to fit the relationship between the number of throttling valve rotations and the amount of fertilizer applied to the fertiliser is:y=-1.71x+14.1,which can provide parameter support for the fertilization of the guide variable.(3)A discrete element parametric model of paddy soil was established,and the law of the dynamic process interaction between opener and paddy soil was studied.The parameters of the opener structure were optimized through experimental analysis.By analyzing the advantages,disadvantages and applicability of the traditional opener,an imitated skid opener suitable for paddy field environment was designed.A paddy soil model was established by the discrete element simulation software EDEM,and the physical parameters and mechanical parameters of the paddy soil model were calibrated.The discrete element simulation analysis method was used to simulate the working process of different structure openers,and the comprehensive score of each factor combination was calculated according to the weighted scoring algorithm.The results show that when the sliding angle is 32.5° and the cutting angle is 45°,the opener has better performance.Taking the opener optimized by simulation analysis as the research object,the depth of the opener and the advancement speed of the opener are taken as experimental factors,and the opener traction resistance is taken as the experimental index to carry out simulation verification and operation performance test.The results show that when the depth of entry is 30 mm,the forward speed is 1.2m/s,the depth of entry is 50 mm,and the forward speed is0.6m/s,the relative error of opener test results and simulation results is 22% and 15%.It is basically consistent with the simulation results.The opener traction resistance increases with the depth of soil penetration and the forward speed.The effect of depth of soil penetration and forward speed on traction resistance of the opener is extremely significant.Therefore,when the actual fertilization operation is performed,a shallower fertilization depth should be selected under the condition of satisfying the agronomic requirements of rice fertilization in order to ensure the opener’s working performance.In summary,the research work on the deep application of liquid fertilizer in this paper has provided theoretical basis and technical support for the deep application of fertilizers in paddy fields.Compared with the traditional deep fertilizing equipment for paddy field,it reduces the blocking phenomenon and improves the reliability of machine tools. |
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