Search

In order to ensure the reliability of the simulation test on the shelling process of ginkgo nuts, the physical parameters (characteristic dimensions, thousand grain mass, moisture content, density, Poisson’s ratio, elastic modulus, and shear modulus), contact parameters (restitution coefficient, static friction coefficient, and dynamic friction coefficient) and actual stacking angle of the ginkgo nuts were measured by physical test methods. A stacking angle test model was established, and simulation tests were performed. Parameter intervals for the simulation were selected according to the measured parameters. Three factors affecting the stacking angle significantly were determined using the Plackett–Burman test: static and dynamic friction coefficients of ginkgo nut–ginkgo nut and the restitution coefficient of the ginkgo nut–steel plate. Each factor’s range was selected using the steepest climbing test. A quadratic polynomial regression model of the stacking angle considering these factors was obtained using the Box–Behnken test. Taking the actual stacking angle of 39.59° as the optimization objective, the optimal combination was formed: the static and dynamic friction coefficients were 0.5 and 0.36, respectively, and the restitution coefficient was 0.42. This combination was used for the verification test. The stacking angle was found to be 41.12°. The relative error was 3.86%, indicating that the model is reliable and can provide a useful reference for relevant research.

Rapid drying of peanut is very important to maintain quality and reduce the risk of mildew, especially for peanut harvested in high moisture content in China. The modified mixed-flow dryer can dry freshly harvested peanut efficiently and evenly which is not available for traditional fixed-bed drying. However, the performances of energy and exergy of peanut drying using modified mixed-flow dryer are not clear, lacking of relevant data for equipment improvement and process formulation. Therefore the relevant investigation was carried out to evaluate the performance of fresh harvested peanut drying using industrial mixed-flow dryer with heat-pump full power heating and waste heat recovery The results show that the energy consumption is mainly consumed by heat-pump and centrifugal fan, accounting for 73.5% and 24.2% of all energy consumed respectively. The overall specific energy consumption and specific heat consumption are 1494.5 kJ/kg and 4706.1 kJ/kg respectively. The thermal efficiency and the energy efficiency are affected by the change of the temperature of airflow entering the drying chamber, both fluctuate over time, increase earlier then decrease later and rise again until the material temperature reach to a relatively steady temperature. And the energy efficiency of dryer (178.9%) is approximately triple of thermal efficiencies of drying chamber (56.1%) and dryer (59.4%) for the overall drying. The heat utilization ratio decreases gradually over drying time, with the overall value of 50.0% for drying chamber and 52.9% for dryer. The exergy efficiency of drying process earlier increases then decreases in the overall trend with the overall value of 51.3%. The exergy efficiencies of the drying chamber and whole dryer are both increased gradually with the overall value of 34.5% and 31.8% respectively. However, the variation tendencies of energy improvement potential rates are opposite to exergy efficiencies.

A box-type hot-air convection dryer integrated with parallel vertical fans, multiple air deflectors, a rack moving mechanism, and an opening heat pump system was designed and used. The airflow distributions in the inlet surface of the air-inlet chamber and drying chamber under empty-loading conditions were measured and the results showed excellent uniformities. The air temperature distributions at the inlet and outlet surfaces of the drying chamber, wet basis moisture content of the materials, energy consumption, product loss rate, and processing capacity were measured and analyzed as well under the loading of longans, lychees, and shiitake mushrooms. The results indicated that the maximum temperature difference at air-inlet surface of drying chamber was 4 °C. The dehydration rate was fast, and the moisture content of the wet basis decreased slowly in the earlier half stage of drying. However, the dehydration rate was slow, and the moisture content decreased at an accelerated rate in the latter half stage of drying. The higher the initial moisture of the material, the more obvious the above phenomenon. Further, the moisture uniformity of dried products reached 90%, with no products of mildewing and obviously insufficient drying found, which would support technique for the drying of fruits and vegetables.

Unsteady one-dimensional partial differential equations for heat and mass transfer in peanut drying are used in mathematical simulations to compare the drying performance of a barrel-shaped bed in three ventilation modes: bottom up, inside out and outside in. Results obtained using the finite difference scheme show that the mathematical simulation reliably predicts the drying process of peanuts, and that the drying delay of bottom-up ventilation is the most significant at the beginning of drying. This is because the drying enhancement afforded by the high average velocity of air along the ventilation direction is insufficient to offset the drying delay caused by the large ventilation thickness compared with that afforded by the inside-out and outside-in ventilation. Furthermore, as the air volume flow increases, the time consumption and moisture content difference decrease, whereas the productivity, energy consumption, and uniformity increase for all three ventilation modes, consistent with the classical ventilation drying law. Under the same air volume flow, the time and energy consumptions for the bottom-up ventilation are the lowest, followed by those for the outside-in and inside-out ventilation. The productivity afforded by the bottom-up ventilation is the highest, followed by that by the outside-in and inside-out ventilation. The outside-in ventilation indicates the least moisture content difference and the best drying uniformity. Meanwhile, the inside-out ventilation indicates the most significant moisture content difference and the worst drying uniformity.

In order to solve problems such as poor applicability of headers, weak separation ability of threshing mechanisms and poor impurity-removal ability of cleaning devices in the existing seed harvest methods of Chinese milk vetch (Astragalus sinicus L.), a combined Chinese milk vetch seed harvester was designed in this paper. The parameters of the key components, such as the flexible anti pod-dropping seedling-lifting header, the longitudinal rod-teeth-type threshing device and the air-sieve-type layered impurity-controlled cleaning device, were designed and optimized. Aiming at reducing seed loss rate, breakage rate and impurity rate of Chinese milk vetch during the mechanical harvesting process, through multi-parameter optimization, the best combination of working parameters was obtained: machine forward speed was 3 km·h−1, rotation speed of the threshing drum was 550 r·min−1, rotation speed of the cleaning fan was 990 r·min−1 and the scale sieve’s opening was 35 mm. Field tests were performed under these parameters, and the results showed that the seed loss rate of Chinese milk vetch was 2.35%, the breakage rate was 0.22% and the impurity rate was 0.51%, which were better than the technical requirements of loss rate and breakage rate less than 5% and impurity rate less than 3% specified in relevant standards. The research results can solve the shortage problem of efficient seed harvest equipment in large-scale planting areas of Chinese milk vetch, and will further help to carry out seed harvest experiments on different varieties of Chinese milk vetch and other green manure varieties in paddy fields.

To improve the quality and efficiency of peanut half-feed harvesting in clay hilly areas in South China and address problems such as excessive soil clumps, broken branches, and seedlings in pods, difficulty in cleaning impurities, and the need for manual picking owing to the high soil viscosity and easy hardening, a new half-feed peanut cleaning picker suitable for southern clay hilly areas, including its overall structure and transmission system, was designed. The picker can perform the operations of soil removal, clamping and conveying of seedlings, and orderly pod picking and pod gathering. The structural design of key components and the analysis and determination of key parameters were carried out. By adopting a crank rocker mechanism, a soil removal device was designed. A single-side chain clamping conveying device, which consists of a clamping chain, a pretightening spring, and a guide rail, was designed. A phase tangent configuration of opposite rollers was used to design a pod picking device. Thus, the functions of the half-feed peanut picker, such as cleaning and removing soil, smooth and reliable clamping and conveying, and flexible pod picking, were realized. The field test revealed that when the picking rate was greater than 97%, the soil removal pods drop rate was less than 10%, and the soil removal rate was greater than 50%. The performance indicators meet the design requirements. This study provides a technical reference for the research and development of clean picking technology for upright peanuts in the clay hilly areas of southern China. [ABSTRACT FROM AUTHOR]

To solve the problems of excessive soil lumps, broken branches and seedlings in pods and difficulty in removing impurities in the harvested pods of peanuts in the hilly areas of southern China, which is due to the high soil viscosity and easy hardening, and to improve the soil removal effect of the peanut half-feed pod picker in hilly areas of China, this article designed a half-feed peanut-cleaning picker suitable for southern clay hilly areas and provided a detailed introduction to the overall structure, working principle, and adjustment methods of various operating parameters. Through field measurement experiments, the influencing factors and laws of soil removal performance indicators, such as the comprehensive soil removal rate and POD drop rate, were studied. The results showed that the comprehensive soil removal rate gradually increased with increasing soil patting frequency, soil patting amplitude, and picking roller speed, first increased and then decreased with increasing picking roller gap and gradually decreased with increasing soil patting plate gap and clamping conveyor chain speed. The comprehensive soil removal rate of the soil patting plate using the opposite patting method was greater than that of the swinging patting method. The soil removal pod drop rate increased gradually with increasing soil patting frequency and amplitude and decreased with increasing soil patting plate gap and clamping conveyor chain speed. The soil removal pod drop rate of the soil patting plate using swing patting was lower than that using the opposite patting method. The speed and gap of the picking roller had no effect on the soil removal pod drop rate. The frequency, amplitude, form, and gap of the soil patting plate had extremely significant impacts on the rate of decrease in the number of soil removal pod drop rate. The clamping conveyor chain speed had a significant impact, while the speed and gap of the picking roller had no significant impact. The influence of all factors on the comprehensive soil removal rate was extremely significant. This study provides a theoretical basis and technical reference for parameter optimization research on peanut-cleaning picking machines in the clay hilly areas of southern China. [ABSTRACT FROM AUTHOR]

To improve the automation level and operation quality of China's beet harvester and reduce the loss due to damaged and missed excavation, this study used a self-developed sugar beet combine harvester and field simulation experiment platform, based on the single-factor bench test of the automatic row following system in the early stage, taking hydraulic flow A, spring preload B, and forward speed C which have significant influence on performance indices as test factors, and taking the missed excavation rate, breakage rate and reaction time as performance indices, the orthogonal experimental study on the parameter optimization of the three-factor and three-level automatic row following system with the first-order interaction of various factors was carried out. The results of the orthogonal experiments were analyzed using range analysis and variance analysis. The results showed that there were differences in the influence degree, factor priority order and first-order interaction, and the optimal parameter combination on each performance index. A weighted comprehensive scoring method was used to optimize and analyze each index. The optimal parameter combination of the overall operating performance of the automatic row following system was A2B2C1, that is, the hydraulic flow was 25 L/min, the forward speed was 0.8 m/s, and the spring preload was 198 N. Under this combination, the response time was 0.496 s, the missed excavation rate was 2.35%, the breakage rate was 3.65%, and the operation quality was relatively good, which can meet the harvest requirements. The comprehensive optimization results were verified by field experiments with different ridge shapes and different planting patterns. The results showed that the mean values of the missed excavation rate of different planting patterns of conventional straight ridges and extremely large "S" ridges were 2.23% and 2.69%, respectively, and the maximum values were 2.39% and 2.98%, respectively; the average damage rates were 3.38% and 4.14%, and the maximum values were 3.58% and 4.48%, which meet the industry standards of sugar beet harvester operation quality. The overall adaptability of the automatic row following system is good. This study can provide a reference for research on automatic row following harvesting systems of sugar beets and other subsoil crop harvesters. [ABSTRACT FROM AUTHOR]

To obtain the optimal operation parameters of fixed-bed reversing ventilation drying of peanuts, a set of partial differential equations indicating the heat and mass transfer relationships between the peanut pods and air during drying was proposed. Then, a series of discretized models were established for simulation, and the time consumed, unevenness, and energy consumption for batch drying were calculated. The results showed that reversing ventilation and segmented drying was helpful to these issues for high drying ability. The optimal operation parameters were determined by uniform design experimentation of mathematical simulation. The result showed that when the moisture content (wet basis) was above 22%, a ventilation velocity of 0.46 m/s was optimal; when the moisture content was between 8% and 22%, a ventilation velocity of 0.20 m/s was optimal. Using the optimal parameters, the computer simulating result was compared with the experimental results. The correlation coefficients between the simulating and the experimental values for the temperature and moisture content were all above 0.98 and the quality of dried peanuts was close to that of natural sun-dried ones, which indicates that the optimization results of the drying parameters are highly reliable. [ABSTRACT FROM AUTHOR]