This study was conducted to further classify threshed strips, so as to broaden the usable range of raw material and facilitate the effective utilization of to- bacco resource. During the threshing and redwing process,...This study was conducted to further classify threshed strips, so as to broaden the usable range of raw material and facilitate the effective utilization of to- bacco resource. During the threshing and redwing process, various process param- eters including the rotating speeds of threshing drums of threshing machioe, draught fans and fling drums were scientifically and rationally set according to the actual quality of the raw material. According to the characteristic that strips with close in- herent quality have basically the same specific gravity and leaf thickness, the strips from each discharge hole were accurately evaluated, and classified, followed by redrying and packaging. The results showed that the threshing and separating pro- cedure could improve the separating effect and precision according to tobacco qual- ity, so as to satisfy the separation and classification requirements for tobacco.展开更多
Mechanical threshing used when preparing maize seeds for planting subjects seed to damage and reduces seed quality.The purpose of this study was to assess the effect of mechanical threshing on the quality of maize see...Mechanical threshing used when preparing maize seeds for planting subjects seed to damage and reduces seed quality.The purpose of this study was to assess the effect of mechanical threshing on the quality of maize seed threshed at different moisture contents(MCs).Seeds of dent maize JK968 and flint maize DD2 were threshed at 12,15,18,21,and 24% MC.The damage degree was determined by iodine staining,and seed vigor was assessed by standard germination(SG),cold test germination(CTG),accelerated aging germination(AAG),seedling emergence rate,and seedling root and shoot length.The results showed that the damage percentage increased,and the seed vigor parameters decreased with increasing seed MC during threshing in both cultivars.For obtaining high seed quality,indicated by at least 90,85,and 80% of SG,AAG,and CTG,respectively,JK 968 and DD2 should be threshed at MC lower than 15 and 18%,respectively.Furthermore,the damage mainly occurred in the apical part of seeds,irrespective of the threshing MC in both cultivars.When the embryo was damaged,seedling emergence rates were significantly reduced with great influence on shoot length.Damage to the endosperm resulted in little effect on seedling performance.Flint maize DD2 was more tolerant to mechanical threshing than dent maize JK968.These results provided technical reference for the production and processing of high vigor maize seeds.展开更多
This paper focused on the influence of the shape and size of threshing frames as well as the grades of tobacco leaves on the structure of threshed leaves.The testing tobacco leaves all came from the hilly ecological r...This paper focused on the influence of the shape and size of threshing frames as well as the grades of tobacco leaves on the structure of threshed leaves.The testing tobacco leaves all came from the hilly ecological region of Nanling and belonged to burnt sweet,alcoholic sweet and scent category.The comprehensive evaluating value S was taken as the test index.Results showed that,without considering the influence of tobacco grade on leaf structure,the shapes of first-stage thresher five-link frames were all hexagons,and the combination with the sizes of 3.5,3.0,3.5,3.0,3.0 inches had the highest evaluating value S of 2.49.For tobacco grade C2FH,the shapes of first-stage thresher five-link frames were also hexagons,and the evaluating value S reached the highest value of 3.40 with sizes of 3.5,3.0,3.5,3.0,3.0 inches.Comprehensive analysis showed that:3.0 inch frame performed better in controlling the percentage of large-sized strips than 3.5 inch frame did;rhombic frames were better than hexagon frames in reducing the breakage rate of tobacco leaves;different shapes or sizes of nonadjacent two-link frames can help to improve the threshing quality.展开更多
In this research, the effects of initial moisture content and needed impact energy on threshing of soybean pods were studied. An impact device was built based of pendulum mechanism. In the experiments, threshing perce...In this research, the effects of initial moisture content and needed impact energy on threshing of soybean pods were studied. An impact device was built based of pendulum mechanism. In the experiments, threshing percentage of soybean pod samples were measured at three initial moisture content levels of 16.25% and 35% w.b. and three energy levels of 173,284 and 446 mJ. The results of analysis of variance showed that moisture content and energy have significant effects on the threshing percentage. By increasing impact energy, amount of pod threshing increased. Also in all the energy levels, maximum threshing occurred at minimum moisture. Maximum threshing percentage was 83.4%, which was at 16% moisture content and 446 mJ levels, also minimum threshing percentage was 3.3% which was at 35% moisture content and 174 mJ levels. Soybean pod with higher moisture, contact between its edges of the pod was stronger than lower moisture, so more energy was needed to separate two edges at 35% moisture.展开更多
[Objectives]The paper was to study the occurrence regularity and life history of cigarette beetle Lasioderrma serricorne(Fabricius)in tobacco leaf threshing and redrying workshop.[Methods]With the tobacco leaf threshi...[Objectives]The paper was to study the occurrence regularity and life history of cigarette beetle Lasioderrma serricorne(Fabricius)in tobacco leaf threshing and redrying workshop.[Methods]With the tobacco leaf threshing and redrying workshop as the survey site,the occurrence regularity of L.serricorne was investigated,and the life history table was inferred according to its biological characteristics.The temperature,humidity and duration of tobacco leaf threshing and redrying were simulated in the laboratory to study the survival rate of all states of L.serricorne in this environment.[Results]The lifecycle of L.serricorne in tobacco leaf threshing and redrying workshop was:the overwintering generation pupated in late February;the pupa began to emerge in early March,and reached its peak in late March.The first-generation eggs started hatching in late March,pupated in late May,emerged in early June,and reached the peak eclosion of the first-generation adults in mid-July.The second-generation eggs began to hatch in late July,pupated in mid-August,emerged in late August,and reached the peak eclosion of the second-generation adults in mid-September.The third-generation eggs began to hatch in mid-September;most of the larvae began to overwinter,some pupated in mid-November and survived the winter as pupae,and some pupae emerged to adults.The survival test results of different states of L.serricorne under simulated temperature,humidity and duration in the tobacco leaf threshing and redrying process showed that the mortality rates of eggs in simulated 1,2 and 3 conditions were about 51.22%,90.24% and 100%,and the mortalities of larvae in simulated 1,2 and 3 conditions were about 18.30%,81.25%and 100%,respectively.The mortalities of pupae in simulated 1,2 and 3 conditions were about 69.39%,100% and 100%,and the mortalities of adults in simulated 1,2 and 3 conditions were about 100%,100% and 100%,respectively.[Conclusions]L.serricorne of different states can be killed by appropriately raising the temperature during threshing and redrying.展开更多
Improving the stability of the homogenization process to achieve the homogeneity of tobacco products is one of important targets for the redrying industry.According to the specification for threshing and redrying proc...Improving the stability of the homogenization process to achieve the homogeneity of tobacco products is one of important targets for the redrying industry.According to the specification for threshing and redrying process,a total of 14 indicators in three categories that affect the quality of the threshing and redrying process were selected.Using analytic hierarchy process,combined with expert experiences,a judgment matrix was constructed to conduct consistency test.The weights of indices in production were obtained.This will help in evaluating the actual production quality,finding the weak links of process and adjusting the parameters of the corresponding links in a targeted manner,thereby improving the quality of production process.展开更多
In this paper, we study the threshold result for the initial boundary value problem of non-homogeneous semilinear parabolic equations {μt-△μ=g（μ）＋λf（x）,（x,t）∈Ω×（0,T）,μ=0,（x,t）∈ Ω×[0,T）...In this paper, we study the threshold result for the initial boundary value problem of non-homogeneous semilinear parabolic equations {μt-△μ=g（μ）＋λf（x）,（x,t）∈Ω×（0,T）,μ=0,（x,t）∈ Ω×[0,T）,μ（x,0）=μ0（x）≥0,x∈Ω.By combining a priori estimate of global solution with property of stationary solution set of problem （P）, we prove that the minimal stationary solution Uλ（x） of problem （P） is stable, whereas, any other stationary solution is an initial datum threshold for the existence and nonexistence of global solution to problem （P）.展开更多
To make up for the gap in the research on high water content maize threshing by airflow,this study took high-speed,low flow,low-speed high flow airflow,and high water content maize ear as the research basis.The variat...To make up for the gap in the research on high water content maize threshing by airflow,this study took high-speed,low flow,low-speed high flow airflow,and high water content maize ear as the research basis.The variation of air flow impacted threshing in numerical simulation,and the variation process of smoke visualization in the threshing area was compared.Taking the maize ear direction,the angle between the maize ear and the air pipe,the diameter of the air pipe,and the flow rate of the air compressor as factors,single-factor and quadratic regression orthogonal rotation combination tests were carried out,and the parameters were optimized.Finally,high-speed photography was used to shoot the maize kernels’shelling process,and movement rules were analyzed from both the front and side views.The results showed that the velocity changes of each section under the numerical simulation are consistent with the flow state changes of smoke.The velocity reached its maximum on the circumference of the maize ear surface and presented a symmetrical distribution.Due to the velocity gradient and pressure gradient difference,the high-speed airflow would entrain the phenomena of the low-speed airflow.When the transverse maize ear,the angle between the maize and the airflow tube)was 45°,the diameter of the airflow tube was 7 mm,the flow rate of the airflow tube was 33 m/s,the loose amount was 10 pieces,the threshed amount was 15 pieces,and the damage rate was below 3%.Through high-speed photography,it was found that the cyclic force circle was destroyed after the maize kernel fell off,the motion of the removed maize kernel was similar to the oblique throwing motion,and the threshing process was carried out in the unit of“arrangement unit”.The threshing process followed the“arrangement law”,and the threshing track was“spiral”.The results of this research can provide ideas for the mechanical design and development of high-moisture-content maize threshing by air.展开更多
The existing discrete element model of wheat plants lacks the glume,which hinders the simulation of the entire threshing process.To address this issue,this paper takes wheat at the harvest stage as the research object...The existing discrete element model of wheat plants lacks the glume,which hinders the simulation of the entire threshing process.To address this issue,this paper takes wheat at the harvest stage as the research object and constructs a complete discrete element model of wheat plants with glumes based on the Hertz-Mindlin with bonding model in the EDEM simulation software.The parameter calibration of wheat glumes discrete element model is studied through collision bounce experiments,slope experiments,and accumulation experiments.The results show that the coefficient of restitution,coefficient of static friction,and coefficient of rolling friction between glume and steel are 0.488,0.625,and 0.048,respectively,and the coefficient of restitution,coefficient of static friction,and coefficient of rolling friction between glume and glume are 0.232,0.966,and 0.059,respectively.The relative errors between the simulation results and the measured values are less than 5%,and the calibration parameters are effective.Based on the structural parameters of the self-developed experiment-bed of tangential axial-flow grain threshing device,a three-dimensional model of the wheat threshing device is established to simulate the whole threshing process of the complete wheat plant,and the bench-scale experiments are carried out with the non-threshing rate as the performance index.The results indicate that the model can completely simulate the separation process of glume and grain and the movement law of different grains,and the relative error of non-threshing rate between the simulation experiments and bench-scale experiments is 4.36%.This further demonstrates that the proposed model can provide a reference for the wheat threshing process research and device performance optimization design.展开更多
Threshing is the most important function of grain harvester.Grain loss and damage in harvesting are significantly related to threshing theory and technology.There are four kinds of threshing principles including impac...Threshing is the most important function of grain harvester.Grain loss and damage in harvesting are significantly related to threshing theory and technology.There are four kinds of threshing principles including impact,rubbing,combing and grinding.Four types of contact models between grain and threshing components have been constructed correspondently.Grain damage can be regarded as a function of peripheral velocity and contact pattern of impacting.Grain loss can be regarded as a function of contact pattern of rasp bars.Grain loss coming from cleaning and separation in the subsequent process of combing threshing was significantly decreased.Tangential and axial threshing technologies have been applied in grain threshing system widely.It showed that in the combined application,tangential rolls are used to accelerate grain flow,and axial rolls are used to increase threshing quality especially lower loss and damage.Conical concave may take the place of the traditional cylindrical one.With the development of sensor technology and communication technology,intelligent harvesting robot and automatic threshing system will be integrated together to improve grain quality and operation comfort.展开更多
Mechanization of field experiments is the only way to improve crop breeding and seed propagation effects.In order to further clarify and improve the working performance of tapered threshing device for plot breeding,an...Mechanization of field experiments is the only way to improve crop breeding and seed propagation effects.In order to further clarify and improve the working performance of tapered threshing device for plot breeding,and reduce the remaining seeds in the device,the numerical simulation was carried out on the motion process of materials in the longitudinal-axial tapered cylinder threshing and transmission device of the plot wheat breeding combine harvester based on CFD-DEM method.Simulation results showed that,threshing and transmission of particles and short stalks at axial direction could be realized under the influence of air flow.Meanwhile,the material transference and distribution rule and stream field distribution rule of air flow in the threshing and transmission device were obtained,the variations of velocity and displacement of particles and short stalks with time were obtained;the motion trajectories and forms of particles in different types of retention were also studied.At rotating speed of 1300-1600 r/min for the tapered threshing cylinder in the verification test,the particle retention rate in the enclosure was 0-0.13%,while in the simulation the particle retention rate in the enclosure was 0-0.11%,only a 0.02%difference between them.The results proved a favorable feasibility to simulate the working performance of the tapered threshing and transmission device for plot breeding through gas-solid coupling method.展开更多
Aiming at the problems of stalks winding and poor threshing performance in the process of mechanical harvesting of oats,a type of threshing and crushing experimental device was designed.The device was composed of a be...Aiming at the problems of stalks winding and poor threshing performance in the process of mechanical harvesting of oats,a type of threshing and crushing experimental device was designed.The device was composed of a belt conveyor,a tangential-flow threshing drum,an axial-flow threshing drum,a high-speed camera and a testing device.According to a regression orthogonal test method,using the rotation speed of the axial-flow drum,the horizontal center distance,and the vertical height difference of the two threshing drums as experimental factors;using the mass fraction of long stalks and the threshing rate as experimental indexes,a mathematical regression model of factors and indexes was established,and combined parameters were analyzed for the threshing quality and crushing ability.Experimental results showed that this device had the best crushing performance when the rotation speed of the axial-flow drum was 850 r/min,the horizontal center distance was 820 mm,and the vertical height difference was 10 mm,and this device had optimal threshing performance when the rotation speed of the axial-flow drum was 760 r/min,the horizontal center distance was 820 mm,and the vertical height difference was 20 mm.The parameters were optimized by Design-Expert 11 to obtain an optimization result that the rotation speed of the axial-flow drum was 800 r/min,the horizontal center distance was 820 mm,and the vertical height difference was 10 mm.A verification experiment was carried out by using a high-speed camera,and the two groups of parameters were selected for a comparative experiment.Images of material movement between the two threshing drums were captured by the high-speed camera.Experimental results showed that the optimized parameters were beneficial to improving the threshing performance and anti-winding performance of the oat threshing process.This study provides a technical basis for the research and development of oat combine harvesters.展开更多
During the threshing process of rice,the grains fall off the head of the rice ear due to the impact of the threshing bar.At the same time,the impact force of the threshing element causes a certain degree of damage to ...During the threshing process of rice,the grains fall off the head of the rice ear due to the impact of the threshing bar.At the same time,the impact force of the threshing element causes a certain degree of damage to the grain.However,there are relatively few methods to analyze the internal damage of rice grains during the threshing process.In this study,the connection force between rice grains and stalks and the compressive bearing capacity of the grains were tested on a push-pull test machine,and then the critical impact force and velocity of rice grains during plastic deformation and brittle fracture were obtained by Hertz theory.On this basis,the quantitative evaluation model of grain internal damage was established through the extraction and calculation of the damaged area inside the grain,and the damage degrees inside the grain under different loading times and loading forces were analyzed.The results showed that the average threshing force required for rice grains is 1.57 N(variance is 0.0529),and the critical impact forces for plastic deformation and brittle fracture of the grains during threshing are 138.79 N and 145.77 N.Since the threshing force during the threshing process was 43.9-71.9 N,it could be known from the internal damage model that the grain is in the safe loading area.Under the same load,the vertical pressure causes the most damage,the lateral pressure takes second place,and the positive pressure was the least.The results of this study can provide a basis for the development of combine harvester and rice grains damage evaluation.展开更多
In order to further reduce the damage rate in threshing seed corn,a seed corn threshing testbed with variable diameter and spacing that can realize dynamic adjustment of parameters,such as feed quantity,rotating speed...In order to further reduce the damage rate in threshing seed corn,a seed corn threshing testbed with variable diameter and spacing that can realize dynamic adjustment of parameters,such as feed quantity,rotating speed of the threshing device,threshing spacing of the threshing units,was designed in this research.The software of finite element analysis ANSYS Workbench was applied to do modal analysis on the threshing axis designed for variable diameter and spacing of seed corn.The first 8 orders of natural frequencies were distributed in 201.12-1640.20 Hz,with corresponding vibration amplitude in 5.86-27.04 mm,showing reasonable structural design of the threshing axis,which could realize effective seed corn threshing and conveying.Discrete element method was applied to do simulation analysis on the seed corn threshing and conveying process with variable diameter and spacing.Under the condition of different feed quantity,different rotating speed of the thresher,the moving speed of corn clusters and contact force among clusters were measured through simulation,and the working characteristics of the threshing testbed for low-damage and dynamic threshing and conveying of seed corn with variable diameter and spacing were revealed.Working performance test results of the testbed of seed corn with variable diameter and spacing showed that,when the rotating speed of the threshing axis was 190-290 r/min,feed quantity was 1.80-3.80 kg/s,the damage rate of seed corn was 0.32%-0.63%,threshing rate was 99.20%-99.82%,and content impurity rate was 4.23%-5.86%,the mass of threshed corn grains first increased and then decreased along the axial direction.The test verification process was in line with the simulation results;thus,the test results could satisfy the requirements in design and actual operation.展开更多
In order to further clarify and improve the working performance of separating cleaning device of flax threshing material,and study the motion law and characteristics of components of flax threshing material,in this pa...In order to further clarify and improve the working performance of separating cleaning device of flax threshing material,and study the motion law and characteristics of components of flax threshing material,in this paper,numerical simulation was carried out on the separating cleaning process of flax threshing material based on CFD-DEM method.Simulation results showed that the components of flax threshing material were separated and cleaned under the influence of airflow field,meanwhile,variation curves of quantity and mean velocity of flax seeds in the separating cleaning system were obtained.By referring to streamline distribution of gas-solid coupling,the quantity variation law of components of flax threshing material with time was explored and their motion curves and variation tendency of average velocity were studied.Verification test results showed that the cleaning rate of separating cleaning device for flax threshing material was 92.66%with 1.58%of total separation loss.Compared with simulation results,the test results were 1.34%and 0.93%lower,showing that it is feasible to apply the gas-solid coupling theory and method to simulate the separating and cleaning operation of flax threshing material.展开更多
文摘This study was conducted to further classify threshed strips, so as to broaden the usable range of raw material and facilitate the effective utilization of to- bacco resource. During the threshing and redwing process, various process param- eters including the rotating speeds of threshing drums of threshing machioe, draught fans and fling drums were scientifically and rationally set according to the actual quality of the raw material. According to the characteristic that strips with close in- herent quality have basically the same specific gravity and leaf thickness, the strips from each discharge hole were accurately evaluated, and classified, followed by redrying and packaging. The results showed that the threshing and separating pro- cedure could improve the separating effect and precision according to tobacco qual- ity, so as to satisfy the separation and classification requirements for tobacco.
基金supported by the earmarked fund for China Agriculture Research System(CARS-02-10)the Special Fund for Agro-scientific Research in the Public Interest,China(201303002)the National Natural Science Foundation of China(31771891)
文摘Mechanical threshing used when preparing maize seeds for planting subjects seed to damage and reduces seed quality.The purpose of this study was to assess the effect of mechanical threshing on the quality of maize seed threshed at different moisture contents(MCs).Seeds of dent maize JK968 and flint maize DD2 were threshed at 12,15,18,21,and 24% MC.The damage degree was determined by iodine staining,and seed vigor was assessed by standard germination(SG),cold test germination(CTG),accelerated aging germination(AAG),seedling emergence rate,and seedling root and shoot length.The results showed that the damage percentage increased,and the seed vigor parameters decreased with increasing seed MC during threshing in both cultivars.For obtaining high seed quality,indicated by at least 90,85,and 80% of SG,AAG,and CTG,respectively,JK 968 and DD2 should be threshed at MC lower than 15 and 18%,respectively.Furthermore,the damage mainly occurred in the apical part of seeds,irrespective of the threshing MC in both cultivars.When the embryo was damaged,seedling emergence rates were significantly reduced with great influence on shoot length.Damage to the endosperm resulted in little effect on seedling performance.Flint maize DD2 was more tolerant to mechanical threshing than dent maize JK968.These results provided technical reference for the production and processing of high vigor maize seeds.
文摘This paper focused on the influence of the shape and size of threshing frames as well as the grades of tobacco leaves on the structure of threshed leaves.The testing tobacco leaves all came from the hilly ecological region of Nanling and belonged to burnt sweet,alcoholic sweet and scent category.The comprehensive evaluating value S was taken as the test index.Results showed that,without considering the influence of tobacco grade on leaf structure,the shapes of first-stage thresher five-link frames were all hexagons,and the combination with the sizes of 3.5,3.0,3.5,3.0,3.0 inches had the highest evaluating value S of 2.49.For tobacco grade C2FH,the shapes of first-stage thresher five-link frames were also hexagons,and the evaluating value S reached the highest value of 3.40 with sizes of 3.5,3.0,3.5,3.0,3.0 inches.Comprehensive analysis showed that:3.0 inch frame performed better in controlling the percentage of large-sized strips than 3.5 inch frame did;rhombic frames were better than hexagon frames in reducing the breakage rate of tobacco leaves;different shapes or sizes of nonadjacent two-link frames can help to improve the threshing quality.
文摘In this research, the effects of initial moisture content and needed impact energy on threshing of soybean pods were studied. An impact device was built based of pendulum mechanism. In the experiments, threshing percentage of soybean pod samples were measured at three initial moisture content levels of 16.25% and 35% w.b. and three energy levels of 173,284 and 446 mJ. The results of analysis of variance showed that moisture content and energy have significant effects on the threshing percentage. By increasing impact energy, amount of pod threshing increased. Also in all the energy levels, maximum threshing occurred at minimum moisture. Maximum threshing percentage was 83.4%, which was at 16% moisture content and 446 mJ levels, also minimum threshing percentage was 3.3% which was at 35% moisture content and 174 mJ levels. Soybean pod with higher moisture, contact between its edges of the pod was stronger than lower moisture, so more energy was needed to separate two edges at 35% moisture.
基金Supported by Science and Technology Project of China Tobacco Guizhou Provincial Corporation(201918)Guizhou Province Academic Pioneer and Academic Pioneer Construction。
文摘[Objectives]The paper was to study the occurrence regularity and life history of cigarette beetle Lasioderrma serricorne(Fabricius)in tobacco leaf threshing and redrying workshop.[Methods]With the tobacco leaf threshing and redrying workshop as the survey site,the occurrence regularity of L.serricorne was investigated,and the life history table was inferred according to its biological characteristics.The temperature,humidity and duration of tobacco leaf threshing and redrying were simulated in the laboratory to study the survival rate of all states of L.serricorne in this environment.[Results]The lifecycle of L.serricorne in tobacco leaf threshing and redrying workshop was:the overwintering generation pupated in late February;the pupa began to emerge in early March,and reached its peak in late March.The first-generation eggs started hatching in late March,pupated in late May,emerged in early June,and reached the peak eclosion of the first-generation adults in mid-July.The second-generation eggs began to hatch in late July,pupated in mid-August,emerged in late August,and reached the peak eclosion of the second-generation adults in mid-September.The third-generation eggs began to hatch in mid-September;most of the larvae began to overwinter,some pupated in mid-November and survived the winter as pupae,and some pupae emerged to adults.The survival test results of different states of L.serricorne under simulated temperature,humidity and duration in the tobacco leaf threshing and redrying process showed that the mortality rates of eggs in simulated 1,2 and 3 conditions were about 51.22%,90.24% and 100%,and the mortalities of larvae in simulated 1,2 and 3 conditions were about 18.30%,81.25%and 100%,respectively.The mortalities of pupae in simulated 1,2 and 3 conditions were about 69.39%,100% and 100%,and the mortalities of adults in simulated 1,2 and 3 conditions were about 100%,100% and 100%,respectively.[Conclusions]L.serricorne of different states can be killed by appropriately raising the temperature during threshing and redrying.
基金Science and Technology Foundation of Hunan Branch of China National Tobacco Corporation(HN2020KJ14,HN2020KJ17).
文摘Improving the stability of the homogenization process to achieve the homogeneity of tobacco products is one of important targets for the redrying industry.According to the specification for threshing and redrying process,a total of 14 indicators in three categories that affect the quality of the threshing and redrying process were selected.Using analytic hierarchy process,combined with expert experiences,a judgment matrix was constructed to conduct consistency test.The weights of indices in production were obtained.This will help in evaluating the actual production quality,finding the weak links of process and adjusting the parameters of the corresponding links in a targeted manner,thereby improving the quality of production process.
基金supported by Natural Science Foundation of China(10971061)Hunan Provincial Innovation Foundation For Postgraduate(CX2010B209)
文摘In this paper, we study the threshold result for the initial boundary value problem of non-homogeneous semilinear parabolic equations {μt-△μ=g（μ）＋λf（x）,（x,t）∈Ω×（0,T）,μ=0,（x,t）∈ Ω×[0,T）,μ（x,0）=μ0（x）≥0,x∈Ω.By combining a priori estimate of global solution with property of stationary solution set of problem （P）, we prove that the minimal stationary solution Uλ（x） of problem （P） is stable, whereas, any other stationary solution is an initial datum threshold for the existence and nonexistence of global solution to problem （P）.
基金funded by the National Natural Science Foundation of China(Grant No.52275245)the Henan Science and Technology Research Project(Grant No.222103810041)。
文摘To make up for the gap in the research on high water content maize threshing by airflow,this study took high-speed,low flow,low-speed high flow airflow,and high water content maize ear as the research basis.The variation of air flow impacted threshing in numerical simulation,and the variation process of smoke visualization in the threshing area was compared.Taking the maize ear direction,the angle between the maize ear and the air pipe,the diameter of the air pipe,and the flow rate of the air compressor as factors,single-factor and quadratic regression orthogonal rotation combination tests were carried out,and the parameters were optimized.Finally,high-speed photography was used to shoot the maize kernels’shelling process,and movement rules were analyzed from both the front and side views.The results showed that the velocity changes of each section under the numerical simulation are consistent with the flow state changes of smoke.The velocity reached its maximum on the circumference of the maize ear surface and presented a symmetrical distribution.Due to the velocity gradient and pressure gradient difference,the high-speed airflow would entrain the phenomena of the low-speed airflow.When the transverse maize ear,the angle between the maize and the airflow tube)was 45°,the diameter of the airflow tube was 7 mm,the flow rate of the airflow tube was 33 m/s,the loose amount was 10 pieces,the threshed amount was 15 pieces,and the damage rate was below 3%.Through high-speed photography,it was found that the cyclic force circle was destroyed after the maize kernel fell off,the motion of the removed maize kernel was similar to the oblique throwing motion,and the threshing process was carried out in the unit of“arrangement unit”.The threshing process followed the“arrangement law”,and the threshing track was“spiral”.The results of this research can provide ideas for the mechanical design and development of high-moisture-content maize threshing by air.
基金supported by the Major Scientific and Technological Project of Henan Province(Grant No.231100110200)the Open Subject of State Key Laboratory of Intelligent Agricultural Power Equipment(Grant No.SKLIAPE2023015)the Open Subject of Key Laboratory of Agricultural Equipment Technology for Hilly and Mountainous Areas(Grant No.2023KLOP03).
文摘The existing discrete element model of wheat plants lacks the glume,which hinders the simulation of the entire threshing process.To address this issue,this paper takes wheat at the harvest stage as the research object and constructs a complete discrete element model of wheat plants with glumes based on the Hertz-Mindlin with bonding model in the EDEM simulation software.The parameter calibration of wheat glumes discrete element model is studied through collision bounce experiments,slope experiments,and accumulation experiments.The results show that the coefficient of restitution,coefficient of static friction,and coefficient of rolling friction between glume and steel are 0.488,0.625,and 0.048,respectively,and the coefficient of restitution,coefficient of static friction,and coefficient of rolling friction between glume and glume are 0.232,0.966,and 0.059,respectively.The relative errors between the simulation results and the measured values are less than 5%,and the calibration parameters are effective.Based on the structural parameters of the self-developed experiment-bed of tangential axial-flow grain threshing device,a three-dimensional model of the wheat threshing device is established to simulate the whole threshing process of the complete wheat plant,and the bench-scale experiments are carried out with the non-threshing rate as the performance index.The results indicate that the model can completely simulate the separation process of glume and grain and the movement law of different grains,and the relative error of non-threshing rate between the simulation experiments and bench-scale experiments is 4.36%.This further demonstrates that the proposed model can provide a reference for the wheat threshing process research and device performance optimization design.
基金This work was supported by the National Natural Science Foundation of China(51705193)National Key Research and Development Project(2017YFD0700302)the Science and Technology Development Project of Jilin Province(20170204016NY).
文摘Threshing is the most important function of grain harvester.Grain loss and damage in harvesting are significantly related to threshing theory and technology.There are four kinds of threshing principles including impact,rubbing,combing and grinding.Four types of contact models between grain and threshing components have been constructed correspondently.Grain damage can be regarded as a function of peripheral velocity and contact pattern of impacting.Grain loss can be regarded as a function of contact pattern of rasp bars.Grain loss coming from cleaning and separation in the subsequent process of combing threshing was significantly decreased.Tangential and axial threshing technologies have been applied in grain threshing system widely.It showed that in the combined application,tangential rolls are used to accelerate grain flow,and axial rolls are used to increase threshing quality especially lower loss and damage.Conical concave may take the place of the traditional cylindrical one.With the development of sensor technology and communication technology,intelligent harvesting robot and automatic threshing system will be integrated together to improve grain quality and operation comfort.
基金The authors acknowledge that this work was financially supported by China Agriculture Research System(CARS-14-1-28)Discipline construction fund project of Gansu Agricultural University(GAU-XKJS-2018-189)National Natural Science Foundation of China(Grant No.51365003).
文摘Mechanization of field experiments is the only way to improve crop breeding and seed propagation effects.In order to further clarify and improve the working performance of tapered threshing device for plot breeding,and reduce the remaining seeds in the device,the numerical simulation was carried out on the motion process of materials in the longitudinal-axial tapered cylinder threshing and transmission device of the plot wheat breeding combine harvester based on CFD-DEM method.Simulation results showed that,threshing and transmission of particles and short stalks at axial direction could be realized under the influence of air flow.Meanwhile,the material transference and distribution rule and stream field distribution rule of air flow in the threshing and transmission device were obtained,the variations of velocity and displacement of particles and short stalks with time were obtained;the motion trajectories and forms of particles in different types of retention were also studied.At rotating speed of 1300-1600 r/min for the tapered threshing cylinder in the verification test,the particle retention rate in the enclosure was 0-0.13%,while in the simulation the particle retention rate in the enclosure was 0-0.11%,only a 0.02%difference between them.The results proved a favorable feasibility to simulate the working performance of the tapered threshing and transmission device for plot breeding through gas-solid coupling method.
基金supported by the National Key Research and Development Program of China(Grant No.2016YFD0701802)the Subject of Educational Science Planning in Henan Province(Grant No.2020YB0265).
文摘Aiming at the problems of stalks winding and poor threshing performance in the process of mechanical harvesting of oats,a type of threshing and crushing experimental device was designed.The device was composed of a belt conveyor,a tangential-flow threshing drum,an axial-flow threshing drum,a high-speed camera and a testing device.According to a regression orthogonal test method,using the rotation speed of the axial-flow drum,the horizontal center distance,and the vertical height difference of the two threshing drums as experimental factors;using the mass fraction of long stalks and the threshing rate as experimental indexes,a mathematical regression model of factors and indexes was established,and combined parameters were analyzed for the threshing quality and crushing ability.Experimental results showed that this device had the best crushing performance when the rotation speed of the axial-flow drum was 850 r/min,the horizontal center distance was 820 mm,and the vertical height difference was 10 mm,and this device had optimal threshing performance when the rotation speed of the axial-flow drum was 760 r/min,the horizontal center distance was 820 mm,and the vertical height difference was 20 mm.The parameters were optimized by Design-Expert 11 to obtain an optimization result that the rotation speed of the axial-flow drum was 800 r/min,the horizontal center distance was 820 mm,and the vertical height difference was 10 mm.A verification experiment was carried out by using a high-speed camera,and the two groups of parameters were selected for a comparative experiment.Images of material movement between the two threshing drums were captured by the high-speed camera.Experimental results showed that the optimized parameters were beneficial to improving the threshing performance and anti-winding performance of the oat threshing process.This study provides a technical basis for the research and development of oat combine harvesters.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51705212)Jiangsu Province“Six Talents Peak”High-level Talent Project(GDZB-085)+2 种基金Natural Science Foundation of Jiangsu Province(BK20170553)Open Fund of Jiangsu Key Laboratory of Agricultural Equipment and Intelligent High Technology(JNZ201912)and Jiangsu Province Postgraduate Research and Innovation Project(KYCX20_3086).
文摘During the threshing process of rice,the grains fall off the head of the rice ear due to the impact of the threshing bar.At the same time,the impact force of the threshing element causes a certain degree of damage to the grain.However,there are relatively few methods to analyze the internal damage of rice grains during the threshing process.In this study,the connection force between rice grains and stalks and the compressive bearing capacity of the grains were tested on a push-pull test machine,and then the critical impact force and velocity of rice grains during plastic deformation and brittle fracture were obtained by Hertz theory.On this basis,the quantitative evaluation model of grain internal damage was established through the extraction and calculation of the damaged area inside the grain,and the damage degrees inside the grain under different loading times and loading forces were analyzed.The results showed that the average threshing force required for rice grains is 1.57 N(variance is 0.0529),and the critical impact forces for plastic deformation and brittle fracture of the grains during threshing are 138.79 N and 145.77 N.Since the threshing force during the threshing process was 43.9-71.9 N,it could be known from the internal damage model that the grain is in the safe loading area.Under the same load,the vertical pressure causes the most damage,the lateral pressure takes second place,and the positive pressure was the least.The results of this study can provide a basis for the development of combine harvester and rice grains damage evaluation.
基金financially supported by Key Science and Technology Project of Gansu Province(Grant No.21ZD10NF003-4-01)Department of Agriculture and Rural Areas of Gansu Province Agricultural Machinery Equipment Remediation Project(Grant No.niyf2022-02)+1 种基金Fuxi Young Talents Fund of Gansu Agricultural University(Grant No.Gaufx-03Y01)Youth Tutor Fund of Gansu Agricultural University(Grant No.GAU-QDFC-2021-08).
文摘In order to further reduce the damage rate in threshing seed corn,a seed corn threshing testbed with variable diameter and spacing that can realize dynamic adjustment of parameters,such as feed quantity,rotating speed of the threshing device,threshing spacing of the threshing units,was designed in this research.The software of finite element analysis ANSYS Workbench was applied to do modal analysis on the threshing axis designed for variable diameter and spacing of seed corn.The first 8 orders of natural frequencies were distributed in 201.12-1640.20 Hz,with corresponding vibration amplitude in 5.86-27.04 mm,showing reasonable structural design of the threshing axis,which could realize effective seed corn threshing and conveying.Discrete element method was applied to do simulation analysis on the seed corn threshing and conveying process with variable diameter and spacing.Under the condition of different feed quantity,different rotating speed of the thresher,the moving speed of corn clusters and contact force among clusters were measured through simulation,and the working characteristics of the threshing testbed for low-damage and dynamic threshing and conveying of seed corn with variable diameter and spacing were revealed.Working performance test results of the testbed of seed corn with variable diameter and spacing showed that,when the rotating speed of the threshing axis was 190-290 r/min,feed quantity was 1.80-3.80 kg/s,the damage rate of seed corn was 0.32%-0.63%,threshing rate was 99.20%-99.82%,and content impurity rate was 4.23%-5.86%,the mass of threshed corn grains first increased and then decreased along the axial direction.The test verification process was in line with the simulation results;thus,the test results could satisfy the requirements in design and actual operation.
基金The authors acknowledge that this work was financially supported by China Agriculture Research System(CARS-14-1-28)Discipline construction fund project of Gansu Agricultural University(GAU-XKJS-2018-189).
文摘In order to further clarify and improve the working performance of separating cleaning device of flax threshing material,and study the motion law and characteristics of components of flax threshing material,in this paper,numerical simulation was carried out on the separating cleaning process of flax threshing material based on CFD-DEM method.Simulation results showed that the components of flax threshing material were separated and cleaned under the influence of airflow field,meanwhile,variation curves of quantity and mean velocity of flax seeds in the separating cleaning system were obtained.By referring to streamline distribution of gas-solid coupling,the quantity variation law of components of flax threshing material with time was explored and their motion curves and variation tendency of average velocity were studied.Verification test results showed that the cleaning rate of separating cleaning device for flax threshing material was 92.66%with 1.58%of total separation loss.Compared with simulation results,the test results were 1.34%and 0.93%lower,showing that it is feasible to apply the gas-solid coupling theory and method to simulate the separating and cleaning operation of flax threshing material.
