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Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A seed metering device is often equipped with a combination of positive and negative pressure in the planter for rapeseed. The chaotic seeds can be discharged via negative pressure suction seed and positive pressure blowing seed in a uniform and orderly manner. However, the orderly state of seed flow is easy to be broken in the process of seed guiding, resulting in unsuitable seed spacing. It is very necessary to clarify the seed guiding process for the higher seeding quality. This study aims to theoretically analyze the influence of structural seed tubes on the orderly state of seed flow. It was found that the main reason for the damage to the orderly state of seed flow was the random collision between seeds and seed tubes in the seed guiding. The influencing factors on the collision were the curve, inner diameter, and length of the seed tube. A simulation test was then carried out on the movement of seeds in the seed tube. Once the more linear curve of the seed tube was, and the thicker inner diameter was, the smaller number of collisions was, and the shorter time of passing through the seed tube was. Specifically, the coefficient of variation was reduced by 2.1 percentage points for the collision number of seeds through the seed tube with the linear-shaped curve in the same inner diameter and length, compared with the S-shaped curve. The coefficient of variation of time was reduced by 1.8 percentage points on average. Compared with the parabola-shaped curve, the coefficient of variation of collision number was reduced by 0.5 percentage points on average, and the coefficient of variation of time was reduced by 0.5 percentage points on average. The coefficient of variation of collision number of seeds was reduced by 7.2 percentage points through 32 mm seed tube in the same curve and length, compared with 25 mm, and the coefficient of variation of time was reduced by 2.6 percentage points. The simulation test showed that the larger the coefficient of variation of the collision times of seed flow through a seed tube was, the larger the coefficient of variation of time was, the more discrete the seed flow trajectory was, and the worse the orderly state of seed flow was. Therefore, there was less influence on the orderly state of seed flow in the curve of the seed tube, compared with the inner diameter and length. The bench test was consistent with the simulation. Compared with the S-shaped curve, the qualified index of seed spacing of the linear-shaped curve increased by 3.2 percentage points on average, the missing index and the multiple index decreased by 2.0 and 1.2 percentage points, respectively. Compared with the parabola-shaped curve, the qualified index of seed spacing of the linearshaped curve increased by 2.8 percantage points, the missing index and the multiple index decreased by 2.0 and 0.8 percentage points, respectively. Compared with 25 mm, the qualified index of seed spacing of 38 mm seed tube increased by 11.4 percantage points, the missing index and the multiple index decreased by 4.6 and 6.8 percentage points, respectively. Compared with 80 cm, the qualified index of seed spacing of 20 cm seed tube increased by 27.6 percantage points, the missing index and the multiple index decreased by 10.6 and 17.0 percentage points, respectively. In addition, the frequency distribution of the time interval gradually changed from normal distribution with relatively uniform interval to exponential distribution with the increase of the multiple index, when the inner diameter decreased or the length increased. The optimal seed guiding was achieved, where the inner diameter of the seed tube should not be less than 25 mm, whereas, the length should not be more than 40 cm. This finding can provide a strong reference for the subsequent development and optimization design of seed tubes. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A pneumatic seed metering device is required for the high speed and intelligent variable operation in recent years. However, the existing complicated transmission and pneumatic system and mechanical structure cannot fully meet the largescale production of pneumatic supply with the high stability, due mainly to the pressure loss caused by a curved pipe. In this study, the invention problem problem-solving theory (TRIZ) and axiomatic theory design (AD) methods were applied to carry out the innovative design of a pneumatic seeding device for rapeseed. Firstly, the seeding maturity prediction and evolution were used to clarify the development stage, evolution path, and potential of seed metering using TRIZ technology. The existing seeding technology was in a recession recovery period, while the evolution of the technology system was in line with the Scurve evolutionary law and evolutionary model. The future seed metering device was preferred for the integration in the simple, microscopic, controllable, and automated evolutionary path. Secondly, the design process model was established using the integration of TRIZ and AD. TRIZ tools were introduced in the process of mapping functional to structural domains. Among them, the "conflict resolution principles" was adopted to solve the contradiction and conflicts of the transmission and pneumatic systems in the existing seed metering device. The invention principles were selected to optimize the structural parameters. Finally, the motor was utilized to directly drive the seeding disk and the built-in air chamber of the fan. The original design matrix was developed using independent design axioms and the minimum entropy. An innovative system was designed to integrate the motor- fan with the pneumatic seed metering device for rape. The trial production and processing were performed on two technical implementation schemes. The motor fan was determined to arrange on the same side after optimization, particularly for the better airtightness and structural stability. The integrated motor drive was used to simplify the transmission, whereas, the integrated fan was to eliminate the gas transmission pipe, in order to reduce the wind pressure loss. As such, the improved transmission and pneumatic system were required only a small space without the additional power. The test results show that the integrated seed metering device was fully meetmet the requirements of single seed metering. A better performance was achieved in the qualified index is more than 90%, even reached reaching up to 99.82%, when the absolute value of suction negative pressure was 1.0-2.0 kPa and the working speed was less than 7 km/h. The required pressure for the qualified index of 90% was lower than before. The innovative design of the pneumatic seed metering device was integrated the power and pneumatic sources, which was were in the line with the technological system evolution path, individual start and stop of the seeding unit without any influence on the rows. More importantly, the mechanical structure and transmission were better matched for the development trend of intelligent variables. This finding can provide an innovative design idea and references for the design of a pneumatic seed device. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Seed metering can be widely used to deliver the seeds or fertilizers from the hopper at selected rates during planting. However, it is still lacking in the quantitative and comprehensive analysis of the current technology of seed metering devices. In this study, a metrological analysis was systematically conducted on the existing literature on seed metering technology, in order to visualize the research trend, in terms of scientific research productivity, influence, and development power. The development of seeding technology was also summarized from the hot topics in recent years. The agricultural products were introduced from the domestic and foreign advanced agricultural machinery enterprises using frontier seed arrangement technology. Finally, the development trend was proposed from the industrialization application at present. The results showed that the seed metering technology was developed in a high-speed steady state. Much more scientific research output and influence in China were close to that in the United States. The high-impact journals included the Biosystems Engineering, Computers and Electronics in Agriculture, Journal of Agricultural Machinery, and Journal of Agricultural Engineering. High-impact scholars and institutions were focused on the seed metering technology for the typical crops in different regions. As such, the seed metering technology was advanced to upgrade the mechanization level. The development trend of seed metering technology was gradually changed from single-topic research on the realization of functions into the in-depth exploration of vertical subdivision topics, such as mechanism optimization, mechanism analysis, and virtual simulation. The current research hotspots of seed metering technology were focused mainly on high-speed simultaneous seeding, seeding uniformity, DEM-CFD coupling simulation, control, and monitoring system. In addition, the high efficiency and performance equipment can be expected to be further developed in the application of seed metering technology, particularly for the new products of seed metering in the running stage. Emerging technologies, interdisciplinary integration, and innovative thinking can be applied to develop with high speed, performance, precise, digital, and intelligent aspects. This review can provide a strong reference to grasp the research status, development trend, and innovation of seeding machines. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shenyang Agricultural University is the property of Journal of Shenyang Agricultural University Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to solve the problems that the surface unevenness leads to the tilt of the seed feeding device of centralized metering device in rapeseed mechanized seeding, which causes insufficient seeding stability, the seed feeding device of centralized metering device was taken as the research object, the working process of the seed feeding device was analysied and the mechanical models between rapeseed and the type hole of the seed feeding device were built at different lateral tilt angle during the seed filling, seed carrying and seed dropping process. The effects of lateral tilt angle perpendicular to work direction and rotating speed of seed feeding device on seeds quantity in type hole and seeds migration trajectory during seeding process were analyzed by EDEM simulation. The simulation results showed that with the increase of the tilt angle within 0°-5°, the average increase of seed quantity in type hole of the tilt side relative to the no tilt increased within 0-36.55%, and the average decrease of seed quantity in type hole on the other side relative to the no tilt decreased within 0-26.68% during seed filling and seed carrying process. The ratio ranged from 1.02 to 2.70 between the highest seed quantity of type hole 1 and the lowest seed quantity of type hole 4. During the process of seed dropping, when the rotating speed of seed feeding device was fixed, with the increase of lateral tilt angle ranged from 0° to 5°, relative to the no tilt state, the average seed quantity increase of seed dropping port I was 0-86.82% and the average seed quantity decrease of seed dropping port II was 0-75.65%, respectively As the rotating speed of the seed feeding device was 20 r/min and 40 r/min, the ratio of seed quantity of seed dropping port I to that of seed dropping port II was 14.4 and 5.29, respectively. The intelligent test platform of planting machines was used to test the effects of different lateral tilt and swing on seeding performance of the seed feeding device. The experimental results indicated that the average error of seed quantity between the bench test and simulation test was 3.86%, which showed that the simulation results were reasonable and credible. With the increase of the absolute value of the lateral tilt angle, the increase of the total seeding rate was 0.76%-8.72% compared with the total seeding rate without tilt. With the increase of the absolute value of the lateral swing angle, the change of the seeding rate of the seed dropping port I and II was 0-55.61% compared with the no tilt state, and the increase of the total seeding rate was 0.65%-4.23%. With the increase of lateral reciprocating swing, the increase of total seeding rate was 1.12%-9.02% compared with that of no tilt state. The test results showed that lateral tilt, lateral swing and lateral reciprocating swing had significant influence on seeding stability. The effects of lateral tilt and swing on seeding performance could be reduced by increasing the rotating speed of the seed feeding device. The results can provide reference for promoting the structure improvement and performance improvement of the seed feeding device. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Rapeseed and wheat are sown in autumn after rice is harvested in the Yangtze River basin and their seeding processes are similar. Seeding uniformity is a key index to evaluate a planter’s seeding performance. The air-assisted centralized seed-metering device which can be widely used in seeding is capable of handling a wide range of seeds with different sizes and shapes with high sowing speed and large width. The typical characteristics of air-assisted centralized seed-metering device were mechanical seed feeding and uniform air-seed flow distribution. The seeding performance was affected by many key parts, such as seed-feeding device, distribution head and seed tube. The long seed tube and airflow in seed tube were typical characteristics in air-assisted centralized seed-metering device. The longer seed tube and airflow affected seed migration trajectory and seeding performance. In order to improve the seeding performance of air-assisted centralized metering device for rapeseed and wheat, the structural parameters of seed tube and working parameters affecting the seeding performance were optimized by mechanics analysis. It revealed that the drag force and gravity promoted seeds’ movement and the seed dropping process was affected by airflow. The seed velocity and accelerated velocity increased under the function of drag force. The collision between seed and seed tube was enhanced when the angle between the seed tube and horizontal plane decreased. Furthermore, the airflow uniformity among different seed tubes was the basis of apiece row consistency. The impact factors included seed tube material, structure, arrangement and working parameters of air-assisted centralized seed-metering device. The structure optimization and seeding performance experiments were performed in bench test. The effects of seed tube material, diameter, length combination, and angle, seed-feeding rotational speed and airflow pressure upon seeding performance were investigated. The seeding performance evaluation indices included variation coefficient of total seeding quantity, apiece row consistency variation coefficient of seeding quantity, variation coefficient of seeding uniformity, and seed damage rate. The seeding uniformity was tested on JPS-12 test bench to simulate seeding in the field. Moreover, the seeding field experiments were carried out to verify the sowing quality of air-assisted centralized seed-metering device using the Huayouza 62 and Zhengmai 9023 as materials. The results showed that: The seed tube material, diameter, the interaction between seed tube material and diameter, and seed tube length combination affected the average seeding quantity and apiece row consistency variation coefficient of seeding quantity significantly. It suggested that the PVC (polyvinyl chloride) material and the diameter of 20 mm with the consistent seed tube length were the optimal. The seed-feeding rotation speed and airflow pressure affected the piece row consistency variation coefficient of seeding quantity remarkably. When seed-feeding rotational speed was within the range of 20-40 r/min, with the airflow pressure of 1 200 Pa of rapeseed and 1 600 Pa of wheat, respectively, variation coefficient of total seeding quantity and apiece row consistency variation coefficient of seeding quantity were less than 1.0% and 4.0% for rapeseed and wheat, respectively. Moreover, variation coefficient of seeding uniformity was 19.0% and 12.5%, respectively, and the seed damage rate was less than 0.1%. Field experiments indicated that the plant density was 40-68 plants per square meter with the variation coefficient of stability less than 20% for rapeseed; and when the plant density was 129 and 252 plants per square meter, the variation coefficient of stability was 8.34% and 8.12% for wheat, respectively. It showed that the plant density and growth characteristics could meet the agronomic requirements for both rapeseed and wheat. The results provide the basis for the structure optimization of air-assisted centralized seed-metering system and improvement of seeding performance. [ABSTRACT FROM AUTHOR]

Seeding uniformity is a very important index in the air-assisted centralized metering device. Gas-solid two-phase flow including seeds and airflow exists in seed feeding device, seed delivering tube, pressurized tube and distributor. In order to study effects of pressurized tube’s structure on seed distribution uniformity in the air-assisted centralized metering device, a numerical study of gas-solid flow in pressurized tube was carried out by the coupling approach of discrete element method (DEM) and computational fluid dynamics (CFD). Effects of structural parameters including dimple depth, dimple pitch and pressurized tube’s length on seed motion, distribution uniformity and airflow field were studied. The variation coefficient of seed distribution and variation coefficient of seeds' distribution uniformity were utilized to evaluate seed distribution. The mathematical models were set to describe structural parameters and seed distribution uniformity by means of the design of the regression-orthogonal combination. Besides, effects of pressurized tube’s length and airflow pressure on seed distribution uniformity were analyzed using bench experiments. Results showed that: 1) The air-assisted centralized metering device with pressurized tube increased variation coefficient of seed distribution and decreased seed velocity and variation coefficient of seeds' distribution uniformity. Pressurized tube’s length, dimple depth, interaction between dimple depth and pressurized tube’s length affected variation coefficient of seeds' distribution uniformity significantly. The optimum parameters combination was dimple depth of 4.2 mm, dimple pitch of 15 mm and pressurized tube’s length of 180 mm, which was achieved by the method of multi-objective programming problem function. Under the superior combination of structural parameters, the variation coefficient of seed distribution and the variation coefficient of seeds' distribution uniformity were 91.17% and 4.91%, respectively. 2) Airflow velocity field in pressurized tube and seed motion characteristics were obtained by analyzing gas-solid flow status. Airflow velocity and pressure in peak of pressurized tube had the minimum value and the maximum value, respectively. Otherwise, airflow velocity and pressure in trough of pressurized tube was the maximum and the minimum, respectively. The peak surface of pressurized tube was located in high pressure and low airflow velocity zone and trough surface of pressurized tube was located in high airflow velocity and low pressure zone. The alternate high and low airflow pressure in pressurized tube changed airflow field distribution. Seed velocity and force in pressurized tube had the trend of sine. 3) Bench experiments indicated that the ranking order of the factors affecting variation coefficient of seeds' distribution uniformity was: airflow pressure > pressurized tube’s length for rapeseed and pressurized tube’s length > airflow pressure for wheat. Based on the optimized structural parameters and airflow pressure of 1 200 Pa for rapeseed and 1 600 Pa for wheat, variation coefficients of seeds' distribution uniformity were 2.84% and 2.89%, respectively. Results suggest that the optimization of structural and working parameters of pressurized tube can improve seed distribution uniformity. The investigation of airflow field, seed movement and seed distribution uniformity involved in this research may contribute to optimizing pressurized tube’s structure and analyzing seed movement mechanism. [ABSTRACT FROM AUTHOR]

The tractor load keeps varying randomly during the tractor - pneumatic planter unit working. It could cause the air pressure in pneumatic precision seed-metering system to become not as constant as the design due to the working speed fluctuation of air pump on the planter led by the variation in rotation velocity of the tractor's power output shaft. Consequently, it would deteriorate the distribution uniformity of seeds in the field and worsen the growth and final yield of crops. To solve this problem, an effective air pressure stabilizing method of pneumatic seed-metering system was proposed based on spring-loaded air pressure relief valve. The first step was to measure the rotation velocity of the tractor's power output shaft in the field. After that, the relationships of the speed of the air pump and the air pressure of the pipeline and the seed-metering device were determined through the bench test. Then, the predetermined control point value of air pressure relief valve was estimated, and the structure and working parameters of air pressure relief valve spring were calculated and selected. Additionally, theoretical analysis and experiments were performed to demonstrate the efficiency of the selected relief valve. A practical engineering in precision combined rapeseed planter, called 2BFQ-6, was used to demonstrate the application of proposed air pressure stabilizing method. A field test was conducted to determine the working speed of the air pump and a laboratory test was implemented to confirm the relationships of the air pump working speed, air pressure in the pipes and air pressure in the chamber of seed-metering device. The test results showed that the coefficient of variation of working speed of the air pump was less than 4.38% when the tractor was working with the same gear, and the coefficient of variation was less than 9.2% as the tractor was working with different gear. To ensure persistent seeding of the seed-metering device, the working speed of the air pump should be in the range of 2 020-2 620 r/min. In order to stabilize air pressure of the pneumatic seed-metering system, the predetermined point value of relief valves were 1 000 and -5 500 Pa with positive and negative air pressure respectively. A type of spring-loaded air pressure relief valve was selected and its construction and working parameters were calculated and analyzed. Carbon steel wire cylindrical spiral spring was employed in the valve. The intermediate diameter and the pitch of the spring were 30 and 10 mm respectively. The number of active coils of the spring was 8. The line diameter of the spring was 1.0 mm for positive pressure relief and 1.5 mm for negative pressure relief. The precompression distance of adjustment bolts were 6.7 and 7.8 mm for positive and negative pressure relief respectively. Theoretical analysis based on air pressure - flow rate characteristics verified that the relief valve used in this pneumatic seed-metering system could be used for air pressure adjusting. Furthermore, air pressure and seeding quantity experiments were performed to evaluate the performance of the selected valve as well as to confirm the feasibility of the proposed stabilizing method. The results showed that the positive and negative air pressure of the seed-metering device could range from 200 to 350 Pa and from -3 900 to -3 000 Pa respectively by employing the relief valves, under which the pneumatic seed-metering system could work stably, showing a contrast to the speed fluctuation of the air pump. The air pressure stabilizing system decreased the deviation rate of the positive and negative air pressure in the air chamber of seed-metering device by 45% and 110%, respectively, which facilitated the pressure-regulating response sensitivity and stability to satisfy the requirement. With the increase of the air pump working speed from 2 000 to 2 700 r/min, the coefficient of variation of seeding quantity was 3.84% without the air pressure stabilizing. [ABSTRACT FROM AUTHOR]

In China, the rape harvesting mechanization level is low and traditional manual harvesting is so poor, so it is necessary to develop rape windrower to improve productivity and reduce cost. The pros and cons of the frame design play an important role on the comfort and working reliability of the windrower machine manipulation. The frame of 4SY-2.9 rape windrower is the base and bears the load of whole assembly, and during the rape windrower working, the exciting vibrations from cutter and the conveyor belt spring tooth will cause the rape windrower to vibrate. Because those excitation frequencies were closed to or overlapped the natural frequencies of the rape windrower, the frame of 4SY-2.9 rape windrower will produce resonance seriously. To improve the quality of laying, reducing the vibration amplitude of the frame of rape windrower is a feasible way, and the finite element method will solve this problem by using structural modal analysis to get the dynamic characteristics of the frame structure. In order to solve the problem of the large amplitude of the rack caused by the random exciting force produced by the movement of various parts of the machine, in this paper, we modeled the rack and imported the model in ANSYS Workbench to work out the frequency and vibration mode of the rack under the free modal, and we verified the accuracy of the finite element model through the contrast of the modal test and the simulation analysis results. It was found that the relative error between the 2 results was in a reasonable range, so the rationality of frame modal analysis was verified. Based on the analysis of the characteristics of the external excitation frequency of the frame and the simulation results, the design scheme was put forward, which was increasing the frame arch structure, and the simulation experiment on the pipe thickness and installation position of arch was carried out. The optimized rack's first-order modal frequency was adjusted to 15.339 Hz, so that it avoided the excitation frequency of the conveyor belt spring tooth and the cutter effectively which could cause the frame resonance. Through the finite element statistics analysis on the optimized model of the frame, the result showed that the strength of the frame met the requirements. Windrower on no-load condition collected acceleration time-domain signal of the biggest deformation point of longitudinal beam, and obtained the fast fourier transform power spectral analysis diagram under the condition with and without the installation of the arch. The test results showed that the amplitude along X direction at the largest peak point of test point decreased by 71.47%, the amplitude along Y direction was reduced by 70.60%, and the amplitude along Z direction was reduced by 70.21%. Field experiments showed that 4SY-2.9 rape windrower had a good operation performance with a good throughput capacity and a high work efficiency, and achieved an orderly intermediate strip paving. The paving width met the requirement of the working width of the collecting sheller. After cut down and dried, the average paving width of rapeseed stalks was 1 674 mm, the average stubble height of rapeseed stalks was 330 mm, and the average stack height of rapeseed stalks was 603 mm. The optimized rape windrower frame had a good dynamic performance, and the field operation effect could meet the requirement of the actual production. This research may provide references for the design and improvement of the similar broad frames. [ABSTRACT FROM AUTHOR]

Seed filling performance plays an important role in seed feeding quantity and uniformity in air-assisted centralized metering system. Wheat seed's filling performance in seed feeding device is not good due to its poor mobility and large repose angle. In order to improve wheat seeds' filling performance, seed churning device as a part of seed feeding device was designed. The major components of seed churning device which was installed in seed filling room included churning tooth and shaft. It transported seeds to seed filling zone and increased seeds' compressive force. The main factors affecting seed filling performance included the seed churning tooth's shape, length and its arrangement, the diameter of churning shaft, and the ratio of rotational speed between seed churning device and feeding mechanism. Seed churning tooth's shape included cylinder and cuboid and its arrangement consisted of double helix, line arrangement and cross arrangement. Mechanical models were established to estimate the seed filling process under the effect of seed churning device. It demonstrated that seed filling performance was correlated with lateral force of seeds related to seed churning device's force. In EDEM(engineering discrete element method)simulation, the effects of installation location of churning device on seeds' compressive force, tangential force, number of seeds in shaping hole and its coefficient variation were studied. The seed filling performance of churning device was investigated in bench test. Two shapes and three arrangements of seed churning tooth were evaluated for filling angle, which was measured by high speed camera using pco.dimax HD system, number of seeds in each shaping hole and seed filling failure rate at 3 lengths of churning tooth (4, 6, and 8 mm). The effects of number of conical-hole wheels, rotational speed ratio between seed churning device and feeding mechanism, and rotational speed were evaluated by examining the mean seed feeding rate, coefficient of variation of seed feeding rate and seed damage rate using three-factor full factorial test. Results showed that: 1) Seed feeding device with churning device gave superior filling performance at all treatments by increasing seeds' compressive force, tangential force, number of seeds in shaping hole, filling angle and seed filling rate. Higher compressive force, tangential force and number of seeds in each shaping hole were observed at larger lateral distance and lower longitudinal distance. The seed feeding device with a location of churning device (-65, 5) produced superior results with 1.92 seeds in each shaping hole and a coefficient of variation of 4.05. 2) Seed churning tooth's length affected filling angle and number of seeds in each shaping hole significantly and number of seeds in each shaping hole was different significantly among different arrangements of churning tooth. The ranking order of the factors affecting filling angle and number of seeds in each shaping hole was: churning tooth's length > arrangements of churning tooth > churning tooth's shape. The seed feeding device with a churning tooth's shape of cylinder, a churning tooth's length of 6 mm, and an arrangements of churning tooth of double helix produced superior results with a filling angle of 78.20°, and a number of seeds in each shaping hole of 1.73 and its coefficient of variation of 0.69%. 3) Seed feeding rate increased with the increasing of number of conical-hole wheels, rotational speed ratio between seed churning device and feeding mechanism, and rotational speed. Optimization of the regression equations incorporating number of conical-hole wheels and rotation ratio through multi-objective programming revealed that the rotational speed ratio between seed churning device and feeding mechanism was 1.154 and the number of conical-hole wheels was 6. Based on the optimized operational parameters, seed feeding rate and its coefficient of variation were 690-1340 g/min and 0.23%-0.80% with rotational speed of 20-40 r/min, respectively. Results suggest that seed churning device can improve seed filling and feeding performance. Through the investigation of seed churning device involved in this research, it may contribute to optimizing the structure of seed feeding device and improving the filling performance. [ABSTRACT FROM AUTHOR]

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Seed feeding device determines the seeding performance of the air-assisted centralized metering system. Seed filling performance is the key parameter to affect feeding quality of seed feeding device. As seeds′ flow properties and compressive force significantly affect seed filling performance, the effects of seed layer thickness on filling performance for rapeseed and wheat were studied in this research. EDEM(engineering discrete element method) software was used for simulating the filling performance and high speed camera technology was used for executing the experiment. Adjustable regulating plate was adjusted for seed layer thickness under different treatments. In EDEM simulation, the experimental factors were inclined angle of adjustable regulating plate with 3 levels(ranging from 50° to 70°), longitudinal distance of regulating plate with 6 levels(ranging from 0 to 25 mm), lateral distance with 3 levels(ranging from 42 to 50 mm) and rotational speed with 5 levels(ranging from 10 to 50 r/min) in single-factor test. Seeds′ compressive force, tangential force and number of seeds in model-hole were used as test indices in simulation. Bench test was performed on test rig by using Huayouza 62 and Zhengmai 9023 as materials, while field experiment was carried out in the modern agriculture science park of Huazhong Agricultural University in 2015. The 3 inclined angles of adjustable regulating plate, 2 longitudinal distances and 3 lateral distances were evaluated for seed filling performance at 5 rotational speeds (10, 20, 30, 40 and 50 r/min). Angles of adjustable regulating plate were 50°, 60° and 70° using complete randomized design (one-factor), longitudinal distances were 15 and 20 mm and lateral distances were 42, 46 and 50 mm with two-factor full factorial test. Seeds′ initial filling angle, filling angle which was measured by high speed camera using pco. dimax HD system, seed feeding rate, coefficient of variation of seed feeding rate and damage rate were dependent variables in bench experiments. The relationships between seed feeding rate, coefficient of variation of seed feeding rate and seeds′ compressive force, tangential force, filling angle were analyzed. Results showed that: 1) Seeds′ compressive force, seed filling angle and feeding performance of regulating plate with the angle of 60° were better than other parameters. Seeds′ compressive and tangential force increased with the increase of longitudinal distance and the decrease of lateral distance. Coefficient of variance of seeds′ number decreased and then rose up. Seeds′ compressive force was generally stable and tangential force increased with the increase of rotational speed. The number of seeds in each model-hole decreased by 5% with the rotational speed increasing of 10 r/min. 2) When rotational speed was within the range of 10~50 r/min, seed initial filling angle, filling angle and seed feeding rate rose with the increasing of longitudinal distance and the decreasing of lateral distance. In addition, the coefficient of variation of seed feeding rate decreased and then rose up with the increasing of longitudinal distance and the decreasing of lateral distance. Seeds′ compressive force, tangential force and seed filling angle were positively and significantly correlated with seed feeding rate. Effects of seed layer thickness and rotational speed on seed filling angle mainly resulted from compressive force and tangential force, respectively. Regarding the agronomic requirements, the ideal parameters were longitudinal distance of 15 and 20 mm for rapeseed and wheat, and lateral distance of 46 mm. Under the combination condition of optimum seed layer thickness, the coefficient of variation of seed feeding rate and the damage rate for the seed feeding device were less than 1.0% and 0.1%, respectively. 3)Field experiments demonstrated that planting density was 38~50 plants per square meter and their coefficient of variation was 10. 64% using the air-assisted centralized metering device under the condition of optimum seed layer thickness. Results showed that the use of this metering device made the emergence performance of rapeseed meet the agronomic requirements. This study investigated the mechanism of seed layer thickness which affected seed filling performance in seed feeding device for rapeseed and wheat. The investigation of seed layer thickness in this research can provide the basis for optimizing the structure of regulating plate and improving the feeding performance. [ABSTRACT FROM AUTHOR]

Wheat and rapeseed are the major grain and oil crop in China and their sowing dates are closer. Seed feeding device is the core component of air-assisted centralized metering device which is capable of handling a wide range of seeds with different sizes and shapes. In order to improve the versatility and use efficiency of air-assisted centralized metering device and adjust the feeding rate accurately, the seed feeding device for rapeseed and wheat with staggered arrangement shape hole and combined conical-hole unit was designed. The problems of pulsing phenomenon due to outer grooved wheel metering device of the centralized pneumatic planter and high damage rate of mechanical metering device for rapeseed needed to be solved, and the structure of staggered arrangement shape hole could keep seeding consciously and uniformly. The seed feeding operation included seed filling, carrying and feeding process. The main structural parameters of shape hole and conical-hole unit were determined in this research. These included length, width, depth and cone angle of shape hole which were 8.0 mm, 5.0 mm, 4.0 mm and 14°, respectively. The diameter and number of shape holes in each conical-hole unit were 80 mm and 60, respectively. Mechanical models were established to estimate the seed filling and feeding process. It demonstrated that seed filling and throwing performance were better under the inclined angle of 13.75°-21.20°. Bench experiments were carried out in the seed metering laboratory of Huazhong Agricultural University in 2015 by using Huayouza 62 and Zhengmai 9023 as materials. The experimental factors were inclined angle (0°-30°) with 4 levels and rotational speed (10-60 r/min) with 6 levels in single-factor test. Two-factor full factorial test was designed with number of conical-hole unit (1-6) and rotational speed. The objective values were seed feeding rate, coefficient variation of seed feeding rate and damage rate. The results showed that: 1) The conical shape hole with inclined angle resulted in a better seed feeding performance. When the rotational speed of seed feeding device was 10-30 r/min, the seed feeding performance of conical shape hole with 20° inclined angle was better than that of others. The coefficients of variation of seed feeding rate for rapeseed and wheat were not more than 1.0% and 1.1%, respectively, and their damage rates were both less than 0.1%. 2) With the increase of rotational speed in the range of 10-60 r/min, the seed feeding rate increased gradually, while the coefficient of variation of seed feeding rate decreased first and then rose up. The lowest coefficients of variation of seed feeding rate for rapeseed and wheat were recorded at 20 and 30 r/min, respectively. Thus, the optimum rotational speeds which resulted in the coefficient of variation less than 1.0% for rapeseed and wheat were 10-40 and 20-50 r/min, respectively. 3) The ranges of seed feeding rate for rapeseed and wheat were 28-450 and 95-770 g/min, respectively when number of conical-hole unit and rotational speed changed. The wide range of seed feeding rate could be adjusted to meet the requirements of different sowing width and high operating speed. The quadratic regression prediction models were established to describe different seed feeding rate for rapeseed and wheat. The models were verified with different forward velocity of Dongfanghong-LX854 tractor. The relative errors between experimental and simulated results in seed feeding rate were smaller than 5%. It indicates that the models can predict seed feeding rate and calculate the number of conical-hole unit and rotational speed accurately. The staggered arrangement shape hole and combined conical-hole unit can realize the adjustment of seed feeding rate in wide range for rapeseed and wheat and the damage rate is reduced significantly. The results provide technical support for the adjustment of different sowing width of air-assisted centralized metering device for rapeseed and wheat. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Oil Crop Sciences is the property of Oil Crops Research Institute of Chinese Academy of Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)