Analysis And Experiment Of Cavitation In Dry And Wet Soil Environments

The natural talent of the mountainous area of Southwest China is poor,it is difficult to implement the mechanized transplanting operation of small seedlings.It has become an urgent need for the development of seedling transplanting technology to develop a small seedling transplant machine suitable for hilly and mountainous areas.On the basis of deep analysis of the mechanism of soil cavitation,combining with the agricultural requirements of Guizhou tobacco and chili,using the theory of circular hole expansion and compaction forming,the method and technology of soil cavitation,and aiming at two kinds of dry and wet soil conditions,we develop the well cella making machine and the large nest hole making machine,and carry on the virtual simulation and experimental research on two kinds of machines.This paper is innovative in terms of structure improvement of well cellar hole forming device,structure design of large hole forming machine,analysis of the soil cavitation process based on EDEM.The main research work and achievements of the paper are as follows:(1)Based on the technical requirements of the hole forming technology of large nests planting and well cellar planting,the experiment of well cellar forming was conducted for different soil moisture conditions to explore the effect of soil moisture on cavitation,and obtains 45%~75% soil moisture content is suitable for making well cellar.When the soil moisture content is lower than 45%,the transplanting of small seedlings can be completed by using the technology of large nests deep planting.(2)Improvement of structure of well cellar hole forming device and Structure design of large nests making machine.the radius of the compacted soil body is 12.7cm when the cavities are formed by using the theory of the circular hole expansion and the compaction molding theory.Analyzing of damage of the actual use of the well cellar hole forming device,the structure improvement scheme of hole forming device is put forward.According to different application situations,three different structural forms of well cellar hole forming device are creatively designed.Based on the analysis of the motion behavior and the stress situation of the soil particle in the large nest forming,using theoretical calculations and empirical formulas,and combining the agronomic requirements of large nests making,the transmission system and the cavity head structure design of the largenests making were completed.(3)Usingthe coupling simulation technology of EDEM and ANSYS,the force analysis of the hole head in the well cellar before and after the improvement is carried out,and the equivalent stress cloud map affected by the soil was obtained.The contrast analysis shows that the improved head into the maximum equivalent stress is reduced by 0.22 MPa.Based on the theory of vibration drag reduction,the modal analysis of the forming device of nylon-steel and steel two kinds of materials is carried out,and the amplitude,vibration frequency and vibration deformation of each order are investigated.It can be seen that the nylon-steel forming device can enhance the potential of reducing soil adsorption and reducing resistance in the production of the well cellar,enhance the strength of the wall and enhance the ability of penetrating ability.(4)Based on the EDEM discrete element software,we completed the simulation analysis of the large nest cave process.The numerical simulations of axial force,torque power consumption and soil particle flow pattern of the cavitation head under different rotational speeds were carried out.It was found that the cavitation head had good cavitation performance when the rotation speed was 500 r/min.the lifting angle of the head of the hole is changed and the result shows that the lead of the head of the hole should be150 mm.The simulation analysis of the different lead angle cavitation heads showed that the best lead should be 150 mm.(5)Field experiment and analysis of well cellar making machine and 2 generation large nest making machines were completed.The well cellar hole making machine test results showed that 3 kinds of wells production can meet the requirements of well cella head.The field experiment of two generations of large nests making machine showed that:The mean value of the diameter and the mean value of the depth from the ridge side of nest produced by the first generation of prototypes have reached the agronomic requirements,but there is a lack of deep turbidity and deep dust in the burrows and ridges.But there is a problem of deep inadequacy in the side of the nest and the larger flying dust.The test results of the second generation prototype are good.the results of field experiments show that the mean value of the depth from ridge top of the den was 15.5cm,the mean value of the depth from the ridge side reached 14.5cm,the mean value of the diameter of the nest reached 31 cm.All indicators meet the agronomic requirements.And the machine has been popularized and applied in some tobacco areas in Guizhou.The research results of the thesis have academic value and practical significance to promote the theoretical research of the seedling forming of transplanting seedlings and toimprove the research and development level of the nest production machine.The popularization and application of the product developed by the project can better solve the problems such as labor intensity,low efficiency,difficulty in meeting the agronomic requirement of the quality of the pits.This will improve the mechanization level of seedling transplanting,realize the reduction of the work,improve the quality and increase the efficiency,and promote the healthy and orderly development of the economic crops such as tobacco and chili in mountainous areas.