Search

The suspension characteristics of the threshed materials of foxtail millet are the basic characteristics for the research of cleaning working parameter optimization and improved design for the cleaning equipment, and the foxtail millet was harvested by the whole-feeding combine harvester. The threshed materials to be cleaned of foxtail millet include the grains, spikelets, stalks and leaves. Based on the requirements of the Chinese national standard test methods for forage seed suspension velocity, using the suspension velocity testing device for agricultural materials, we designed and conducted the staged suspension experiments to measure the suspension velocities of the 4 kinds of threshed materials of foxtail millet respectively, and we also measured the suspension velocities of the threshed materials with different moisture contents, and then we researched the relations between the suspension velocity of each part of threshed materials and its moisture content. Based on the differences among the measured suspension velocities of threshed materials, we estimated the suitable range of cleaning air velocity and conducted the cleaning experiment via cleaning experimental device to verify our estimation. We got the threshed materials with different moisture contents by means of rehydrating and drying. We immersed the threshed materials harvested into the water for 6 h to make their moisture contents saturate, and then we put the saturate threshed materials into the thermostatic drier box to dry for different times at 100 ℃. The drying times were 10, 20, 30 and 40 min respectively, and thus we got other 4 kinds of threshed materials with different moisture contents from the harvested threshed materials’, and so we totally measured 5 kinds of threshed materials with different moisture contents. The staged suspension experiments included 3 stages. When there were one third of the materials to be measured suspending in the tapered observed pipe at some height, one suspending stage was reached. We measured the suspension velocity of the suspended materials via DP2000-11 type intelligent pressure air-volume anemometer in every stage, and there were 6 measure points in every stage, and we calculated the average value of the 6 measured values. We used the suspended height ruler to measure the suspension height range of the suspended materials, and we used the average value and the suspension height range to calculate the suspension velocity range of the suspended materials based on the flow consistency principle. Synthesizing the 3 suspension velocity ranges, we got one suspension velocity range of this kind of material with a certain moisture content. There were 6 repeats of suspension velocity measurement for every kind of material with a certain moisture content. Synthesizing the 6 suspension velocity ranges of a kind of material with a certain moisture content, we finally got the suspension velocity ranges of this kind of material. The experimental results showed that the suspension velocities of grains, spikelets, stalks and leaves of threshed materials of foxtail millet harvested by combine harvester were respectively 4.29-8.88, 1.03-5.48, 1.71-5.33 and 1.03-3.09 m/s. There was no overlapping numerical interval between the grains’ suspension velocity range and the leaves’, while there were some overlapping numerical intervals between the grains’ suspension velocity range and the spikelets’ or the stalks’. With the decrease of moisture content of foxtail millet, the overlapping numerical intervals were all reducing between the grains’ suspension velocity range and the spikelets’ or the stalks’ or the leaves’. We used the maximum of the suspension velocity range of every kind of material with a certain moisture content to carry out a statistical analysis. The moisture content affected the suspension velocity of every component of the threshed materials significantly, and the significance level P values were all less than or equal to 0.048 8. With the decrease of moisture content, the suspension velocities of grains, spikelets, stalks and leaves were all decreasing, and there were quadratic function relations between the moisture content and the grains’ suspension velocity or the spikelets’ or the stalks’ or the leaves’, and the fitting precisions were all greater than or equal to 0.951 2. The results of cleaning experiment proved that the estimation was rational. The suitable range of cleaning air velocity for the threshed materials of foxtail millet was 4.29-5.48 m/s, and the optimal air velocity at air outlet was 4.47 m/s. Under the action of airflow with optimal air velocity, the loss ratio of grain was 4.68%, and the cleanliness of grain was 98.83%. The research results can provide reference for the determination of the timely harvest time and the optimal cleaning working parameters. [ABSTRACT FROM AUTHOR]

Suspension velocity of agricultural material is important basic data for the research of technology and equipment for mechanical cleaning. Given the characteristics of threshed materials to be cleaned of crops harvested by combine harvester, based on the suspension principle of material and the characteristics of mechanical cleaning working condition, we designed a kind of vertical air sweeping suspension velocity testing device for agricultural material. This device mainly consists of 3 kinds of components, including the air force and its controlling components, the flow field structural components and the measuring components. The air force and its controlling components are directly connected with the flow field structural components by flanges in vertical direction, and the measuring components are installed on the flow field structural components. The structure is compact. The air force and its controlling components consist of the centrifugal fan, the frequency converter, the conduit coupler between fan and pipelines, and the protecting net. The flow field structural components consist of the grille tube, the airflow-smoothing grille, flanges, holding net for materials, entrance gate of materials, collecting board for materials, lower airflow-stablizing pipe, tapered observation pipe, upper airflow-stablizing pipe, obstructive net for materials, and so on. The measuring components consist of the L type Pitot tube, bracket of Pitot tube, intelligent pressure air-volume anemometer, air conduit, suspended height ruler, observation platform, and so on. The overall size of this device (length × width × height) is 1.8 m × 1.1 m × 4.2 m. The motor power of fan is 7.5 kW. The airflow velocity can reach 40 m/s in this device. The flow field structural components are mainly formed by the grille tube, lower airflow-stablizing pipe, tapered observation pipe and upper airflow-stablizing pipe connected successively via flange connections in vertical direction. The 4 pipes are all welded with flanges at both ends and made of polymethyl methacrylate. The lengths of the 3 pipes except the grille tube are all 1 m. The inner diameters of the grille tube, lower airflow-stablizing pipe and the small end of the tapered observation pipe are all 240 mm. The dip angle of tapered observation pipe is 4° and its inner diameter of big end is 380 mm. We designed a circular airflow-smoothing grille installed in this device to avoid generating eddy at the outlet of fan, and its height is 100 mm, the side length of its square hole is 30 mm, and the thickness of grille plate is 2 mm. The anemometer can display the temperature, humidity, pressure, airflow velocity and flow rate in real time in the measurement. We designed and conducted staged suspension experiments to measure the suspension velocity of each component of the threshed materials to be cleaned by combine harvester during the harvesting time of foxtail millet, buckwheat and oat, respectively. The results show that the range of suspension velocity of grains, spikelets, stalks and leaves of threshed materials to be cleaned of foxtail millet is respectively 4.29-8.88, 1.03-6.48, 1.71-6.09 and 1.03-3.09 m/s. The range of suspension velocity of grains, ramulus, stalks and leaves of threshed materials to be cleaned of buckwheat is respectively 4.47-10.18, 1.85-5.18, 2.80-8.37 and 0.76-2.99 m/s. The range of suspension velocity of grains, testas, ramulus, stalks, leaves and unpeeled grains of threshed materials to be cleaned of oat is respectively 4.35-11.01, 0.62-1.71, 1.62-4.52, 1.14-6.28, 0.91-3.56 and 3.24-9.48 m/s. The grains’ suspension velocities of foxtail millet and oat are both different from their most light impurities’, the grains’ suspension velocity of oat is similar to its unpeeled grains’, and the grains’ suspension velocity of buckwheat is different from its minor light impurities’. This study can provide reference for the research and development of cleaning technology and equipment for agricultural materials. [ABSTRACT FROM AUTHOR]

Foxtail millet is a kind of minor coarse cereal. It is not one of the main grain crops, and is a kind of rainfed crop. So, it is mainly planted in the hilly and mountainous areas in northern China. Foxtail millet is becoming more and more popular in congee because of its mellow taste and abundant nutritional value. Given the characteristics of small and scattered planting plots for foxtail millet in northern hilly and mountainous areas, small seeder is more suitable for this kind of plot. According to the agronomic requirements of fine and small-amount sowing for foxtail millet, we design and manufacture the 2BZ-2 type fine and small-amount seeder for foxtail millet. This seeder consists of 2 sowing units, transmission system, ground wheels and body frame. Every unit is mainly made up of seed-metering device, furrow opener, soil coverer and press wheel. We use the tilt dise-type fine and small-amount seed-metering device for foxtail millet that was designed previously, and its working angle is 45°, and it has 36 filling holes and 36 seeding grooves. This device has got the national invention patent in China, and we have published an academic paper about it on Transactions of the Chinese Society of Agricultural Engineering. We design a kind of ship-shaped shovel type furrow opener, and its penetrating angle is 60°, its soil-cutting angle is 30°, its trenching width is 30 mm, and its height is 100 mm. We design a kind of scraper type soil coverer, and it mainly consists of 2 covering boards, connecting board and pull rod. The covering board is trapezoid-shaped, and its length is 100 mm, its front width is 80 mm, its back width is 40 mm, and its thickness is 3 mm. The included angle between the 2 covering boards is 50°, the inclined angle of the covering board toward the ground is 70°, and the width of the back opening between the 2 covering boards is 30 mm. We push the seeder and provide the driving force. The ground wheels pass the driving force to the seed-metering device via the transmission system. The transmission system is composed of two-stage chain drive and one-stage bevel gear drive. The chain drive uses the 08B roller chains and the matched chain wheels to drive down. The bevel gear drive uses 45° straight bevel gears to realize constant speed drive. According to the experimental requirements of Chinese National Standards, we design and conduct the seeding performance experiments and the field sowing experiments to test the working performance of this seeder. The seeding performance experiments include the tests of the consistency of every row's seeding quantity, the steadiness of total seeding quantity and the percentage of damaged millet. The field sowing experiments include the tests of the uniformity of sowing quantity and the consistency of sowing depth. The results of the seeding performance experiments indicate that, the coefficient of variation of consistency of every row's seeding quantity is less than or equal to 1.10%, the coefficient of variation of steadiness of total seeding quantity is less than or equal to 0.66%, and the percentage of damaged millet is less than or equal to 0.05%. The results of the field sowing experiments indicate that, the qualified index of hill spacing is greater than 83%, the replay index is less than 7%, the miss-seeding index is less than 12%, the coefficient of variation of qualified hill spacing is less than 10%, and the coefficient of variation of sowing depth is less than 1.5%. All the 8 indices meet the requirements of Chinese machinery industry standards. This study can provide a theoretical reference for the design and analysis of the fine and small-amount seeding equipment for foxtail millet suitable for the hilly and mountainous areas. [ABSTRACT FROM AUTHOR]

In order to solve the difficulties of sowing for small grain seeds, such as foxtail millet, we firstly study the agricultural requirements of precision drill of millet without thinning out seedlings. After analyzing the advantages and disadvantages of different seeding devices, we design a kind of tilt dise-type fine and small-amount seed-metering device for foxtail millet. We measure the shape and dimension of the millets with the microscope using the projection method, and the friction coefficient of millet with different materials as requested by the national standard of China. We analyze the motor process of millet, which helps us design the structure of this device. It is mainly made up of filling dise, shell, discharging dise, elastic flipping device and drill shaft. It has many advantages. Its structure is simple, and its working principle is reliable. Its working position tilt is from 45° to horizontal direction. The overflowing seeds from filling holes are flexibly cleaned under the action of gravity, so they will not be damaged. There are 36 filling holes in the filling dise, and they are uniformly distributed on the circumference of filling dise. Matched with filling holes, there are 36 seeding grooves in the discharging dise, which are uniformly distributed on the circumference of discharging dise. The filling dise is above the shell, and the discharging dise is below the shell, both of which synchronously rotate. There is a passing hole between them in the shell. The millets fall in the filling holes, and revolved around the drill shaft together with filling holes. When they arrive at the passing hole, the millets leave the filling holes, then pass through the passing hole and enter the seeding grooves. The millets continue to revolve around the shaft together with the grooves. There is a dropping hole at the bottom of the shell. Before they arrive at it, the millets move to the end of the grooves. When they arrive at the dropping hole, the millets leave the groove, pass through the dropping hole, and fall into the seeding tube. According to the movement characteristics of millets, on the premise of not damaging them, we design the shapes and dimensions of the filling hole, seeding groove, passing hole and dropping hole. This device is expected to seed 2-3 millets from every seeding groove, and the intervals of millets are kept steady on the soil. We especially design an elastic flipping device to flip the millet stuck in the filling hole out of it, which is installed on the upper boss above the passing hole of the shell. We design the fit clearance of 0.2 mm between filling dise, discharging dise and shell simultaneously, thus eliminating the friction between them. In order to test the performance of this device, we use 6 indices from the national standards of China. They include the percentage of damaged seeds, variability coefficient of steadiness of total seeding quantity, qualified index of hill spacing, repeated sowing index, miss-seeding index and variability coefficient of qualified hill spacing. We design and conduct the experiments of the steadiness of total seeding quantity and the uniformity of seeding rate with this device. We also measure the percentage of damaged seeds discharged from this device. The results show that the variability coefficient of steadiness of total seeding quantity is less than 0.7%, the qualified index of hill spacing is greater than 86%, the repeated sowing index is less than 12%, the miss-seeding index is less than 7%, the variability coefficient of qualified hill spacing is less than 5%, and the percentage of damaged millet is less than 0.05%. All the indices meet the requirements of the industrial standards of China. It will provide a theoretical reference for the design and analysis of fine and small-amount seed-metering device for small grain seeds. [ABSTRACT FROM AUTHOR]