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Research On Key Technology And Supporting Device Of Pressure-Adjustable Waterjet Stubble-Cutting For No-Till Sowing

Posted on:2024-11-15Degree:DoctorType:Dissertation
Country:ChinaCandidate:M H QuFull Text:PDF
GTID:1523307340976529Subject:Agricultural mechanization project
Abstract/Summary:PDF Full Text Request
Frequent farming has led to the overall degradation of black soil resources.The promotion of conservation tillage technology is an important measure in the Northeast black soil protection project.The efficient operation of no-till sowing is of great significance to protect the soil,improve agricultural economy and realize the major strategy of"store grain in the ground".The maize stubble in the black soil area of Northeast China are thick and tough.During the implementation of low-till and no-till sowing in the spring,if it can not be cut off in time by the mechanical opener,it will be blocked in front of the opener as the machine advances,causing great soil disturbance and lower operating efficiency.The waterjet opener continuously sprays water at a high pressure,which will cause excessive consumption of water,excessive moisture in the seed bed,rotten seeds and a great impact on the efficiency and the quality of no-till sowing operations and the germination of seeds.Therefore,this paper proposed a pressure-adjustable waterjet stubble-cutting device based on stubble thickness detection.The Smoothed Particle Hydrodynamics-Finite Element Method(SPH-FEM)coupling algorithm was used for simulation to explore the law of waterjet stubble-cutting and soil disturbance.A pressure-adjustable waterjet stubble-cutting device was developed and the working performance was verified through field experiments.The main research contents and conclusions are as follows:(1)The physical properties of soil and stubbl and the static mechanical performance test of stubble,which provided theoretical basis and parameter support for the simulation test of the process of waterjet stubble-cutting and soil disturbance and the design of the stubble thickness detection device.Field stubble thickness was measured.The difference in moisture content and electrical conductivity of surface stubble and soil at different depths(0-20cm)were analyzed.Through tensile,compression and shear tests,the static mechanical properties of the stubble shell,the stubble pitch and the all stubble under different moisture contents were evaluated,and the mechanical performance parameters of the stubble were obtained.(2)Simulation test of the process of waterjet stubble-cutting and soil disturbance.Accoding to the basic parameters obtained from physical tests,the constitutive equations of stubble,soil and water were established.Based on the SPH-FEM coupling algorithm,a simulation test was conducted on the operation process of waterjet stubble-cutting and soil disturbance to explore the interaction and influence between water-stubble-soil.The accuracy of the simulation test was verified through bin tests and high-speed cameras.The simulation test obtained the influence rules of waterjet pressure,cutting angle and forward speed on stubble cutting and soil disturbance:the greater the waterjet pressure,the faster the water destroyed the sttubble.The cutting with angles caused greater cutting damage,but the cutting depth was weaker than vertical cutting.When the waterjet pressure met the stubble-cutting requirements,the faster the forward speed,the faster the stubble destruction speed.After the waterjet cuts stubble,it still impacted and damaged the soil below.Under the same cutting angle and waterjet pressure,as the forward speed increased from 3km/h to 4km/h and 5km/h,the impact depth of the soil at the same time decreased by 7.4%and 11.11%,respectively,and the soil disturbance width did not change significantly.The bin verification test showed that the correlation coefficient(R~2=93.86%)between the test value of the waterjet stubble-cutting depth obtained in the simulation test and the measured value in the bin test was reasonable,and the simulation model could effectively reflect the stubble-cutting process.As the forward speed increased,the impact soil depth gradually became smaller,and the soil disturbance width did not change significantly as the forward speed increased,the trend of which was consistent with the simulation test.(3)The design and test of the stubble thickness detection device,which provided a test basis for the research on the pressure-adjustable waterjet stubble-cutting for no-till sowing device.Based on the difference in electrical conductivity between soil and stubble,a stubble thickness detection device and software and hardware of the detection system were designed.After calibration,the experiment obtained the influence of soil moisture content,soil solidity and forward speed on the stubble thickness detection error.By analyzing the regression model of the stubble thickness detection error,it could find that when the soil moisture content was 29.91%,the soil solidity was0.84MPa and the forward speed was 3.01km/h,the minimum straw thickness detection error was 3.03%.The stubble thickness detection error was verified through the soil bin test.The actual measured value and the model predicted value was less than 5%,which could provide data support for research on the performance of the stubble thickness detection device.(4)Design and test of pressure-adjustable waterjet stubble-cutting for no-till sowing device based on stubble thickness detection.A pressure-adjustable waterjet stubble-cutting for no-till sowing device based on stubble thickness detection was designed.The waterjet stubble-cutting for no-till sowing device was optimized.The influence of different operating parameters on the stubble cutting rate and water consumption was obtained.Through the response surface analysis test,the regression models of stubble cutting rate and water consumption were obtained:when the jet pressure was 26MPa,the cutting angle was 90.45°and the forward speed was 3.36km/h,the maximum stubble cutting rate was 95.49%and the minimum water consumption was 49.98L/ha.The relative errors between the measured values of stubble cutting rate and water consumption and the values obtained by model optimization were 1.81%and4.98%,respectively,both of which were less than 5%.The stubble cutting performance of waterjet stubble-cutting for no-till sowing device with pressure-adjustable system was evaluated through soil bin test.The results showed that the waterjet stubble-cutting for no-till sowing device with pressure-adjustable system could significantly lower water consumption under the condition that the stubble cutting rate,the degree of blockage and the working resistance had no significant difference.(5)Field verification test.Field verification test was conducted to test the effects of waterjet pressure,cutting angle and forward speed on stubble thickness detection error,stubble cutting rate,clogging degree,water consumption and soil disturbance.The following conclusions were drawn:the stubble thickness detection error increased with the forward speed increased.The difference in stubble cutting rate between pressure-adjustable and constant pressure waterjet stubble-cutting for no-till sowing device was no more than 3%.At any speed,the pressure-adjustable waterjet stubble-cutting for no-till sowing device experienced severe blockage less than 5 times.Compared with constant pressure,pressure-adjustable waterjet stubble-cutting for no-till sowing device could save 6.84%-11.2%in water consumption.The impact soil depth decreased with the increase of forward speed,and the soil disturbance width and soil disturbance coefficient changed little due to the influence of operation speed.The differences in soil impact depth between field tests,soil bin tests and simulation tests were no more than 12.9%and 3.7%.The differences in soil disturbance width between field tests,soil bin tests and simulation tests were no more than 13.3%and 5.5%.In summary,the physical property parameters of soil and stubble were measured in this study.The constitutive equations of water,soil and stubble were established.Based on the SPH-FEM coupling algorithm,the process of soil disturbance and waterjet stubble-cutting was simulated and analyzed.The effects of waterjet pressure,cutting angle and forward speed on stubble cutting and soil disturbance were explored.Based on the difference in electrical conductivity between soil and stubble,a pressure-adjustable waterjet stubble-cutting for no-till sowing device based on stubble thickness was designed.The effects of waterjet pressure,cutting angle and forward speed on stubble thickness detection error,stubble cutting rate,clogging degree,water consumption and soil disturbance in field were evaluated.It provided theoretical and practical support for the further application of waterjet technology in agricultural engineering.
Keywords/Search Tags:waterjet, no-till stubble cutting, SPH-FEM coupling simulation, conservation tillage
PDF Full Text Request
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