| Rice is a very important food for the word. Over half of the human being & 60% of the total population in China live on it. The present mechanization of paddy production (4.43%) is low in China comparatively with corn (35.1%) and wheat (72.9%). There is great room for catching up with the world level. As for transplanting and direct-seeding in rice production mechanization, more efforts have been put on direct seeding but less on the study of the machines for direct seeding. Therefore, it is urgent to develop a new seed-metering device which can fit to rice seed character and satisfy direct seeding in agriculture. The air seed-metering is comparatively a good device in sowing crops. It has a good adaptability, a nice reliability, a lower damaged-seed ratio and can fit to higher working speed. So, this paper takes the air seed-metering as the investigation object. Based on the current state and appliance of rice-planting mechanization summarized, the status and research issues of air seed-metering technology, this paper establishes foundation between seeding performance and parameters by uniform design method, simulate and analyze the fluid field of air seed-metering through hydro-engineering simulation software FLUENT. We study the working process and discuss the theory of air seed-metering device via high speed video camera system technique. The major points are as follows: 1. Study the rice bud-sowing characteristics,these parameters could be used as the basis of designing seeding machines and the form of seed-metering device: The physical characteristics, the cutting intensity of rice bud-sowing and rice bud seed are tested, for three types of rich bud which are good for Jilin Province. The ratio of continued-growing for rice bud-sowing began declining evidently with increasing load when the static force exceeds 4.5N. The average cutting force is 1.20N for the three rice bud. 2. Studied the seeding performance of air seed-metering device by uniform design method: The dynamics analysis of filling area and taking area are carried out for air seed-metering. Critical vacuum's formula is made. According to the vacuum's formula, the result of calculating is fitting better with experimental data. The seeding performance is tested under four factors with six levels for rice bud-sowing. Establish the mathematical models of the seeding performance of air seed-metering device, and opened out internal laws of the seeding process for air seed-metering device. The uniform design and experimental results can be referenced in development of seed-metering device and other similar products. Found the main factors by experiment: Vacuum pressure is the most important factor for the seeding performance. Quality of seed index, multiples index, missing index are mainly influenced by vacuum pressure. There is great influence to the quality of seed index by vacuum pressure & the counter affection between vacuum pressure the rotation speed. Rotational speed effects quality of seed index and missing index, but has almost no influence on multiples index. Diameter of bore effects multiples index and missing index, but has less influence on quality of seed index. Quantity of bore effects multiples index, but has little influence on quality of seed index and missing index. The optimal parameters are diameter of bore by 2.2-2.4mm, 54 bores and vacuum pressure by 2.8-3.6kPa. With this condition the working requirement for direct drilling rice bud-sowing can be demanded in operating speed of 6-8km/h. 3. Resulted the formula of diameter suction bore is as d = (0.64~0.66)b, and the formula of distance with two suction bores is as L = (1 .2?1.3)l. The result develops the design theory of air seed-metering. 4. For the first time, simulate and analyze the fluid field of air seed-metering through hydro-engineering simulation software FLUENT. According to the characteristic of fluid field for air seed-metering device, the analyses have been carried on the non compressible formula of Navier-stokes's from the constant temperaturesystem. Then 2D-model and 3D-model are established for vacuum chamber of air seed-metering device. 1) The clearly characteristic of the whole vacuum chamber fluid field can be obtained for air seed-metering device by numerical values analyses. The results show that the method of simulation is reliable, visual and directly than the machine experiments. This study establishes a foundation for the systematic design theory and optimized design of air seed-metering device with rice bud-sowing. 2) There is great effect for the uniform of vacuum chamber by diameter of bore. The results of simulate and experimental analyses show that there is better seeding performance and the fluid field's distributing uniformity at bore diameter between 2.2-2.4mm. Intervene phenomena occurs between two bores when the quantity of bore exceeds 60. This phenomena severity influences the uniformity of fluid field. 5. For the first time, we analyses the working process and research on the theory of seed filling and dropping for air seed-metering device via high speed video camera system technique. Based on the seed dropping images from high speed video camera, analyses the effect for seed spacing uniformity with the gesture of seeds. With the filling images from high speed video camera, analyses the theory of filling for air seed-metering device. The path and velocity of seed in filling area are simulated by FLUENT software. By the seed cleaning images from high speed video camera, find the reason that seed fly out the seeding room, and improve the structure of seeding room accordingly. 1) Find three gestures of seed on the seeding plate. A. Seed is absorbed on a bore long axle. B. Seed is absorbed at end. C. One bore absorbs two seeds, one seed at bore long axle one at its ends. The seed dropping paths of three gestures are analyzed by FLUENT software. The effect for seed spacing uniformity is analyzed with the seed's gestures. And the effect factors are discovered for the seed's gestures. 2) Prove the seed filling process on the surface of seeding room. According to the seed filling images from high speed video camera, prove the seed filling process on the surface of seeding room. The path and velocity of seed in filling area are simulated by FLUENT software, and the theory of seed filling is discussed for air seed-metering device.3) The error factors of seed spacing after seed dropping are analyzed. The reason, cost seed rotation &dropping time difference by seed gravity and the deviation of the bore center when seed was absorbed, was found out with analyzing of the seed dropping motion. 4) Find the reason that seed fly out the seeding room, and improve the structure of seeding room accordingly. 5) We discovered the limit of linear velocity can get to 0.56m/s. It raises 40% of the traditional velocity (0.35m/s). 6. Develop the new air seed-metering device of double seed plates which can fit to rice seed character and satisfy direct seeding in agriculture. Forward speeds can only get 3-4km/h for single plate with single row bores. But the performance cannot demand direct seeding in agriculture for single plate with double rows bores. Based on the research of single seed plate, we developed the new air seed-metering device of double seed plates. Design the clearing part with rubber cover which reduce the impact on the ice bud, and prolong the open site of seed falling to guarantee the dropping seed back to the seed room, and install two seed plate on the axis with keys in order to ensure 10cm row spacing, 2cm seed spacing with Z forms to meet the requirement in direct seeding. The experiment is carried out for the new air seed-metering device of double seed plates. The results show that this structure of seed-metering device is well-knit; this device can demand of high speed planting with small seed spacing.
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