Research Of Theory And Experiment On Air Suction Cylinder Device For Tray Nursing Seedling Of Super-Rice

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. Super rice is the new rice varieties and combinations that varieties through an ideal shape and the advantages of the use of hybrid combination of selective breeding which yield significant improvement in quality and strong resistance. China has now identified nearly 61 super rice varieties and combinations. Super hybrid rice planting area accounted for about 15% of rice planting area in China. And the acreage of super hybrid rice planted area will account for more than 30% in 2010, which is about 8 million hectares. There is a greater difference between the cultivation of super hybrid rice and conventional rice. Precision seeding of existing can only be applied to meet the needs of conventional seedling of rice which 3~5 seeds per hole and seedling qualified rate more than 85%,and it is difficult to meet the precise demands of super hybrid rice planting which 1~3 seeds per hole. At present, the mechanized cultivation model of super hybrid rice is still at an exploratory stage. There is no technology and supporting equipment in mechanized cultivation of super hybrid rice at home and abroad .Therefore the research of the key technology and equipment of super precision planting rice seedling is urgently needed. To study the key technologies and main difficulties in precision plug seedling of super rice, a new air-suction cylinder precision seeder for plug seedling of super rice was designed. The method combining with numerical simulation and high-speed camera and experimental research was used in this paper which combined with the agronomic requirements in mechanized cultivation and aimed at the seedling device performance evaluation index of super hybrid rice. The main contents and conclusions of the paper are following:1. Study the super hybrid rice characteristics based on the agronomic requirements in mechanized cultivation: The physical characteristics and the cutting intensity with three types of super hybrid rice are tested. The ratio of continued-growing for super hybrid rice began declining evidently with increasing load when the static force exceeds 180N. As static load is less than 120N, the ratio of continued-growing is above 95%. These parameters could be used as the basis of designing seedling device for super hybrid rice.2. A new air-suction cylinder precision seeder used the combinations of vibrating-plate and air-suction cylinder for plug seedling of super rice was designed on the basis of kinetic analysis with it. The seedling performance was studied by uniform design method. Establish the mathematical models of quality index of air-suction cylinder precision seeder, and acquire the appropriate range of parameters influencing factors.1) The seedling performance was studied by uniform design method, and establishes the mathematical models of the seeding performance of air-suction cylinder precision seeder, acquires the appropriate range of parameters influencing factors and opens out internal laws of the seeding process for air seed-metering device. Results by experiment show that: rotational speed is the most important factor for the quality index of absorption,then is vacuum pressure and Diameter of sucker followed. Other factors affect the passing rate is not significantly, but the law is complex.2) Establish the mathematical models between the quality index and multiples index and missing index with the influence factors of air-suction cylinder precision seeder, and acquire the appropriate range of parameters influencing factors. The optimal parameters are diameter of sucker by 1.4-1.6mm, and vacuum pressure by 3.0-3.5kPa, and rotational speed by 12～15rpm, and vibrating frequency by 45～95Hz, and sucker spacing by 2.6～3.0 mm. The regular percentage of the quality index comes to 90.92% and the regular percentage of missing index comes to 2.85% under these optimal parameters.3. For the first time, simulate and analyze the fluid field of air seed-metering with Euler-Lagrange and RSM through hydro-engineering simulation software FLUENT.According to the characteristic of fluid field for dual air-suction cylinder device, the flow field simulating and comparative test are carried under the conditions of different operating parameters of the positive and negative pressure.1) The clearly characteristic of the whole fluid field can be obtained for dual air-suction cylinder 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-suction cylinder device with super rice seedling.2) There is great effect for the uniform of vacuum chamber by diameter of sucker. The results of simulate and experimental analyses show that there is better seeding performance and the fluid field's distributing uniformity at sucker diameter between 1.4-1.6mm. Intervene phenomena occurs between two sucker when the spacing of sucker smaller than 2mm. This phenomena severity influences the uniformity of fluid field. It also shows that there is better blowing performance at cylinder thickness between 5~ 8mm.4. For the first time, comprehensive analysis the process of vibration seed-plate work with the theory of vibration mode, reveal the filling mechanism of air suction cylinder device. 1)Build vibration model of the seed-plate and supply seed areas based on small deflection elastic theory, vibration location tests show that excitation source location affect qualification rate of seed suction significantly; excitation source under rear seed-plate is favorable for maintaining the accuracy sowing of steady-state; excitation frequency is an important factor that affect process of seed suction by the air-suction vibrating cylinder device, the best range of frequencies with using air-suction and vibrating frequency is between 90 ~ 100Hz.2)For the first time, build seed layer viscous damping mechanical model and thickness model with Modal analysis theory. Study seed layer and other working parameters on absorption properties through quadratic orthogonal tests, build regression equation between the factors of seed layer thickness, double-hole spacing and vibration frequency. Results show that seed layer thickness affect seed suction significantly in the vibration frequency range of 90 ~ 100Hz. seed Suction performance of sowing parts changes with the seed layer thickness. in productivity for the 450/ h, optimal parameters are seed layer thickness is 7 mm, vibration frequency is 98 Hz, qualification rate of seed suction is 93.12%.3)Analyze seed buds adhesion phenomenon in supply ways of the existing seed box, study vibration mechanism on impurity removal in seed-plate sieve area. The results show that impurities adsorbed to the suckers is caused by accumulation of water in the bottom of seed box, lower surface tension of the liquid can effectively reduce impurities adsorbed to the suckers. The numbers of plug the suckers is reduced with the vibration frequency increases when vibration frequency is low; But the numbers of plug the suckers is reduced unconspicuous with the vibration frequency increases when seed box at top of the cylinder.5. Analyze adsorption process of the air suction cylinder super rice seedling device via High-speed video camera system technique. Based on the high-speed camera images, analyze three stages of adsorption process and the seeds fall off phenomenon in supply seed area, analyze the reason of the seeds fall off carry seed area, find causes of qualified rate instability on seed suction and the best sucker hole spacing, provide the basis for the vibration seed-plate improvement.6.The new air-suction cylinder precision seeder with a vibrating-plate was developed for plug seedling of super rice, based on the above results,achieve precise control of suction seed. The performance of seedling which can satisfy the agronomic requirements in mechanized cultivation reached the technical requirements of precision seedling for super rice tray seedling.