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Rice is a major food crop grown widely in south and northeast China, particularly on a total annual production of nearly 210 million tonnes with a high level of consumption. The rice must be dried in time to minimize the loss as a result of sprouting, molding, and bursting waists after harvest. A positive-pressure high-temperature dryer is mostly adopted for hot-air drying in the actual production at present, but it was easy to cause uneven drying and low quality of rice. A negative-pressure dryer can be expected to improve the uniformity of rice drying and further reduce the saturation temperature of materials with a high drying speed in low-temperature drying, while shortening the drying time for energy saving. The mechanism and arrangement of angle tubes determine the airflow in the chamber for the rice drying. In this study, an analytical model was established for the negative-pressure drying of rice in a vertical chamber using irreversible thermodynamics, in order to gain even air distribution for better drying efficiency and quality of the dried product. Combined with the mixed flow drying, a perforated air duct with variable diameter was designed to improve the air distribution in the air duct of the vertical chamber. FLUENT software was used to conduct the numerical simulation and experimental verification for the flow field in the drying chamber under the conditions of no- and full-load. The research results showed that the perforated air duct with variable diameter well improved the wind speed and flow in the pipe of the vertical chamber for the uniform drying of rice. A self-developed 5HSN-1 dryer with a negative-pressure circulation system was used to optimize the drying parameters. In a quadratic orthogonal rotation test with four factors and five levels, the regression model was established with the temperature of hot air, the wind speed, the speed of discharging roller, and the initial moisture content as the experimental factors, while the drying rate, and increment rate of waist burst as the test indices. The optimal combination of working parameters was as follows: the wind speed of 0.75 m/s, the hot air temperature of 40 ℃, the rotation speed of discharging roller of 3.2 r/min, the initial moisture content of 16.9%, the drying rate of 1.407%/h, the increment rate of burst waist of 0.574%. The relative error between the experimental and optimized values was 6.2%-7.4%. The model with excellent fitting can offer practical application for better comprehensive quality of rice drying. [ABSTRACT FROM AUTHOR]

Continuous technological innovation of farmland irrigation is a critical component of the strategy for dealing with the shortage of water resources and arable land resources around the world, and is a key to ensuring food security for a growing population especially in developing countries such as China. In this study, a Concept of Crop Initiate Drawing Water (CIDW) was proposed, and four basic preconditions for its included: 1) soil is always water unsaturated, and planted crops must be upland crops; 2) external water potential outside the soil-root system is maintained less than atmospheric pressure; 3) the distance between external water and crop roots is kept as short as possible; and 4) a high efficiency water permeable interface capable of enduring the matric potential difference and another form opposite potential difference. For CIDW, there is invariably matric potential difference between the external water and soil-root system, and another mainly opposite potential difference which determinates the operation mechanism and its category. According to the literature, three type of CIDW were identified, namely Pressure Potential Difference (P-CIDW), Osmotic Potential Difference (O-CIDW) and Gravitational Potential Difference (G-CIDW). The characteristics and operating conditions of the these three types of potential differences were analyzed and described. At present, the overwhelming majority of published studies of CIDW have focused on P-CIDW, only few studies have explored O-CIDW and G-CIDW. The significant advances in hardware included: 1) the form of negative pressure in the P-CIDW system has gradually changed from water pressure to air pressure; 2) the devices used to maintain negative pressure are now small, light, require no energy and are high precise(volume and weight are only one to ten percent of that of traditional devices); and 3) a new organic negative pressure water seepage material, namely Polyvinyl Formal (PVFM), has been invented and verified to be significantly superior to traditional materials like ceramics. At the same time, a large body of literature investigating the most efficient and suitable way to apply P-CIDW fully showed: 1) compared with traditional irrigation technologies such as flood irrigation, furrow irrigation and drip irrigation, P-CIDW with suitable parameters could significantly improve crop yield or water use efficiency, nutrient uptake, fertilizer utilization efficiency, enzyme activity, microbial diversity in the soil rhizosphere, and a coupling effect of water and fertilizer; 2) P-CIDW could significantly affect crop physiological and biochemical indexes and soil nutrient availability and spatial distribution, and whether those effects were beneficial or not depended on different research conditions; 3) soil texture and its profile configuration significantly affected soil water and salt transport and distribution under P-CIDW; and 4) by integrating initial soil moisture content and matrix potential, hydraulic conductivity of emitter, head of water supply and time, the cumulative infiltration under P-CIDW could be semi-theoretically and semi-empirically estimated. Finally, the future of CIDW was speculated on, and it concluded: 1) there was an urgent need to develop a basic theory explaining the soil moisture to crop relationship, 2) development of high efficient potential difference interface materials for CIDW was key; 3) the technical standards for P-CIDW should be formulated as soon as possible; and 4) the revolutionary innovation for methods of maintaining pressure in P-CIDW system was needed. [ABSTRACT FROM AUTHOR]

Large-scale grain drying technology has a nearly 50 years of development history in China. There are concurrent flow dryer, countercurrent dryer, cross flow dryer and mixed flow dryer, which meet the actual needs in various fields. But compared with the similar foreign products, there are many defects on our grain dryer, such as low manufacturing technology, low level of automation and high energy consumption. The co-current flow dryer has the characteristics of dry uniformity, low unit heat consumption and high productivity. But there are some defects, such as poor control of drying quality, high cost of drying and environmental pollution. These shortcomings are not conducive to the sustainable development of agricultural production and ecological environment. Therefore, from the perspectives of the structure and the process of the high temperature grain dryer, combining energy saving with conservation of grain quality is the key to the development of modern grain drying technology. Generally, the form of air supply in large-scale grain dryer is positive pressure, with easy maintenance and adjustment. The negative pressure air supply technology is only used for small cycle dryers. In this paper, the negative pressure technology in the large-scale grain drying system was applied for the first time. Negative pressure drying can effectively solve the internal control problems of the drying process based on the theory of micro pressure. Negative pressure is beneficial to collect the grain dust, create excellent production environment and realize safe production. The losses of static pressure and dynamic pressure are relatively small in the process of negative pressure drying, and this technology can reduce power consumption, and is easier to realize intelligent control of air volume and air medium parameters. In order to reduce primary energy consumption and improve corn drying process capacity, combined with grain drying characteristics in cold region, 5HFS-10 type negative pressure grain dryer was designed based on the principle of negative pressure drying. This drying technology combined the multi-stage concurrent flow and countercurrent flow, and a set of advanced structure and control system were applied in this drier. The parallel dilated fan was combined with variable diameter cornute duct, the cold air quota regulation agencies were coordinated, online work parameters were real-time collected with multi sensors, the adaptive control system was adopted, and all of these completed the intelligent quality-guaranteeing drying production of the staple food crop. In this paper the calculation of drying parameters and structure parameters was carried out providing the theory basis for the comprehensive evaluation and the design of negative pressure dryer. Production test shows that the machine’s work performance is good, its energy saving is significant, and it has good drying quality, unit mass of low cost, high degree of automation, and so on. The deviation of the moisture of discharged grain is less than ±0.5% w.b. Compared with the traditional positive pressure air supply dryer, this dryer saves the power by more than 20%, and reduces the production cost by more than 12%. The operating performance can perfectly meet the requirements of farm drying and large-scale drying technique. It provides the theoretical basis for the development of energy-saving intelligent grain dryer. [ABSTRACT FROM AUTHOR]

In recent years, under the dual pressures of labor and mechanization, the demand for gardening equipment in the facility is increasing in China. Especially the nursery pait has the heavy workload, and there is the most urgent demand for automatic production equipment. Pick-up mechanism is a key part of most nursery production equipment, the pneumatic pick-up is a flexible clamping technology, and it is developed for the seedling clamping job in recent years, but the existing flexible pneumatic pick-up method is based on a rigid platform to pick up seedlings. Because there are individual differences of seedlings, the existing pick-up mechanism is difficult to adapt to the changes of seedlings size and morphology, which results in the stationary adsorption distance that makes it difficult to adsorb all the seedlings on the rigid platform. In the pick-up operation, the negative pressure sucker is set to contact with the seedlings, but the seedlings with true leaves on the rigid platform are not kept at the horizontal state, which will lead to the problems of being difficult of adsorbing seedlings, long operating time, and consuming energy. To solve the above problems, based on vacuum adsorption principle, the study comes up with a flexible pneumatic pick-up method for seedlings. The method is constituted by the negative pressure pick-up finger and flexible seedling seat. The flexible seedling seat designed in this study consists of the pl&te to put seedling, the buffering steel cable and the fixing plate. The eggplant seedlings are manually placed on the plate with the V-notch. so the eggplant seedlings are limited by the V-notch in the diameter direction. The flexible seedling seat has a certain height and the seedlings is in the horizontal state on the buffering steel cable, thus solving the problem that the pick-up operation is unstable because it is one end high and one end low for the seedlings due to the existence of the true leaves. At the same time the seedlings are supported by the buffering steel cable. The seedlings on buffering steel cable can avoid rigid extrusion when they are on the rigid platform, by the stress analysis, buttering steel cable diameter is calculated to be 0.32 mm Because the maximum leaf span is 100.3 mm the height of seedling seat is designed as 50 mm. hi summary, the flexible seedling seat is better than the rigid platform on locating seedlings. The flexible seedling seat can correct the seedling place position. Because of the buffering effect of the flexible seedling seat, it can resolve the problem that the rigid platform is difficult to adapt to the size and morphology of seedlings. On this basis, the experiment is performed to optimize the structural parameter of flexible seedling seat. And the comparison test of the pick-up performance between the rigid platform and the flexible seedling seat is earned out. Test shows that: The support spacing between 2 buffering steel cables of the flexible seedling seat is 9 mm. the notch depth to holding seedling is 6 mm and the side distance between the fixation point of buffering steel cable and the plate is 4 mm. At the above conditions, the adsorption pick-up success rate can be guaranteed to be over 90% within 2.8-5.1 nun range for eggplant seedlings. On the base of absorbing eggplant seedlings scion successfully with the diameter of the seedling of 4 mm (the diameter of the seedling between 3.8 to 4.2 mm also is classified as the diameter 4 mm), when it is on the rigid platform, the average seedling injury rate is 21%. the average response time for the adsorption is 0.08 s: when it is on the flexible seedling seat with the best combination of structural parameters, the average seedling injury rate is 5%. which is decreased by 16% compared with the rigid platform, the average adsorption response time reduces to 0.03 s. and the productivity increases by 62.5% compared with that on the rigid platform. The findings will provide an important reference for the development of picking device for agricultural robot. [ABSTRACT FROM AUTHOR]

In order to test the flow field of the mill, the project group proposed a new method based on virtual instrument technology, and constructed a set of test system according to the method, which coverd the design of the instrument selection, data acquisition, data analysis and processing. In the program design process, we designed an integrated virtual digital filter using the powerful data and signal analysis tools in Lab VIEW, which covers 6 kinds of commonly used digital filters. Taking a new type of mill prototype as the experimental object, the project group carried out many test experiments on the single air flow field and the air and solid two-phase flow field in the chamber. Firstly, the pressure and velocity of the air flow field in A section were tested by 2 kinds of test methods and the single flow field of the whole chamber was simulated and analyzed. Through the comparison, the result showed that the error was in the 5% and the 3 ones were consistent with each other. Secondly, when the speed was constant, the pressure distribution of the flow field near the wall under the condition of no load and load was consistent with that of the flow field near the wall. Thirdly, the influence of material concentration on the flow field near the wall was not obvious at the 1000, 1500, 2000 and 2500 r/min rotating speed of the air flow field, the effective value of the pressure decreased with the increase of the speed, and the air-solid two-phase flow had the same law. The effective value of the pressure in the corresponding test point was reduced. In air flow field, the pressure value of less than or equal to 1500 r/min was positive. This showed that in the work, the low speed of the pressure field was small, and the negative pressure of the back was small. Besides, rotation speed of the mill had a great influence on negative pressure, when the speed changed from 1000 to 2500 r/min, and the maximum negative pressure of test was from-20.35 to-411.15 Pa. The negative pressure calculated by back propagation(BP) neural network algorithm was from-37.24 to-678.42 Pa. The effect of material on the flow field near the wall was not much, but it would weaken the negative pressure in the center area. The sealing performance of the mill had great influence on the internal flow field. Under the 2500 r/min work condition, so the theoretical maximum negative pressure was-2.5 KPa, and the test maximum negative pressure was only-411.15 Pa. Therefore, the method and the measuring system provide the technical support for the following study on the relationship between the pressure and the structural parameters of the mill, and provide the theoretical basis for the optimization design of the new type of mill. [ABSTRACT FROM AUTHOR]

At present, dimension-positioning method is adopted as the main method for grasping tissue culture seedlings in tissue culture transplanting equipments. But the majority of gripper structure based on dimension-positioning is complex, which causes that the precision of the operation can not be improved. Meanwhile, young tissue culture seedlings will certain be damaged by the gripper in the process of clipping, which affects the survival rate of the transplanted tissue culture seedlings. To solve such problems, this study designed a force-positioning pickup system based on vacuum adsorption, which can transplant banding tissue culture seedlings. The pickup system for tissue culture seedlings mainly consists of three parts, including vacuum production part, negative pressure detection part and the suction nozzle part. The suction nozzle part is the key part, which decides the holding effect of tissue culture seedlings. The core of suction nozzle is inner soft tube made of silicone rubber with a metal shaping pipe sleeved outside. To increasing the adsorption area, the suction nozzle lip is shaped as oblong. In this paper, design and experiments are both mainly focused on the structure and parameter of suction nozzle. The process that suction nozzle picks up a tissue culture seedling can be divided into two phases: adsorption phase and holding phase. In adsorption phase, negative pressure flow field in the suction nozzle, which is generated by the vacuum generator, will help the seedling overcome its gravity, so that the seedling can be absorbed and adhered to the suction nozzle lip closely. In holding phase, the suction nozzle lip and the stem of tissue culture seedling joint closely, and a vacuum cavity emerges with less leakage in the suction nozzle, then the vacuum cavity generates the force for holding the tissue culture seedling. In adsorption phase, there are two schemes about negative pressure inner cavity of suction nozzle, and they are deformed cavity and parallel cavity. To get the average velocity of flow field near suction nozzle lip, simulation analysis have been carried out based on each of the two cavity with CFD (computational fluid dynamic) software in adsorption phase. The corresponding verification test also have been done, and the results supported that deformed cavity will be used in the pickup hand system because the suction nozzle using deformed cavity can produce flow field with higher velocity, and hold tissue culture seedling more steadily. In holding phase, a series of orthogonal experiment, single factor experiment and interaction experiment were carried out, to test the impact factor about tissue culture seedling holding strength, including thickness of suction nozzle tube, diameter of suction nozzle tube, radius of oblong suction nozzle lip and height of suction nozzle lip. The experiments results show that the optimum parameters for the tissue culture seedlings of suction nozzle are 0.5 mm thickness of suction nozzle tube, 6 mm diameter of suction nozzle tube, 0.7 mm radius of oblong suction nozzle lip and 1.5 mm height of oblong suction nozzle lip in experiments. With these optimum impact factors, suction nozzle can hold banding tissue culture seedlings steadily whose diameters range from 1.2 to 2 mm. It is noteworthy that overall success rate of negative pressure pickup system for banding tissue culture seedling can reach up to 98%, which successfully meets the requirements of insertion in next operation for transplantation. [ABSTRACT FROM AUTHOR]