Wang Xiaochan

Motion analysis and system response of fertilizer feed apparatus for paddy Variable-Rate fertilizer spreader

Abstract Precision agriculture and variable-rate technology have gained increasing public interest. To improve the rapid response ability of the control system of a variable-rate fertilization and reduce the errors corresponding to the feed fertilizer system in a centrifugal variable-rate spreader, three devices that could adjust the application rate using different actuators were developed; these involved the gear and rack structure A, electric handspike structure B, and screw slider structure C. Mechanism motion analysis models were established based on vector equations, the response analysis of system delay was performed according to the model of lag fertilization, and subsequently, performance tests were executed to calibrate the lag distance of falling fertilizer, as well as the response time of actuators and the error of feed fertilization flow. The test results indicated that for actuators A, B, and C, the average lag distance of falling fertilization was in the order LA > LC > LB, with the respective values being 3.56, 2.72, and 1.85 m; the corresponding lag correction times were 1.99, 1.74, and 1.48 s, respectively. A positive proportional relation was noted between the application increment and response time of apparatus execution, and TBi > TCi > TAi (i denotes the corresponding feed fertilization flow). Furthermore, the error of fertilization flow first decreased and then increased with the increasing application rate; the extremum appeared between 250g/s and 380g/s, and γBi > γAi > γCi. The feed fertilizer with structure C was optimized and integrated field validation tests, and incorporating the corresponding correction time of lagging response Tlag = 1.74 s into the control system, the mean error of variable-rate fertilization system was determined as 9.67%, and the average lag distance of fertilization was 0.37 m. This indicated that the control system of variable-rate fertilization with correction response time alleviated the problem of lag falling fertilizing, improved the response speed of variable-rate fertilization for rice, and helped achieved better fertilization accuracy.

Numerical simulation of spreading performance and distribution pattern of centrifugal variable-rate fertilizer applicator based on DEM software

Abstract Farmers in China have been concerned with the efficiency and utilization rate of fertilizers, because of the rigorous implementation of China’s “dual-reduction” plan, which calls for reducing fertilizer and pesticide usage. This study was aimed to improve the spreading performance and fertilizer distribution uniformity of an independently developed centrifugal variable-rate fertilizer applicator. The spreading performance was evaluated by conducting discrete-element-simulation tests, and the relationship between the variations in the fertilizer particle distribution and the working parameters of the fertilizer spreader was analyzed. The quality of the particles was evaluated using a two-dimensional matrix, and the coefficient of variation of the transverse distribution of the fertilizer particles was determined. The results show that the shape of the distribution varies irregularly with the increase in the vane pitch angle, and the coefficient of variation decreases with the increase in the spreader disc height. Further, when the application flow rate is increased gradually, the coefficient of variation decreases rapidly first but gradually thereafter. In addition, with an increase in the rotational speed of the disc, the distribution gradually changes from a triangular shape to a W shape and ultimately to an M shape. The average coefficient of variation was the lowest (14.39%) for a single-row application flow rate of 300 g/s, a vane pitch angle of 15°, a spreader disc height of 95 cm, and a rotational speed of 600 r/min, with a good spreading uniformity. Field validation tests show that the average coefficient of variation with respect to the effective spreading swath width of the applicator was 16.74%. The relative error was 10.66% with respect to the simulation results, thus validating the simulation model and confirming its accuracy. The results show that the coefficient of variation for the developed variable-rate spreader is reduced, exhibiting a high spreading performance. The results serve as a theoretical basis for farmers for altering their traditional empirical fertilization techniques and should aid design and optimization of centrifugal variable-rate fertilizer applicators.

Development and Prototype Experiment of Environmental Self-Propelled and OrderlyHarvester for Artemisia selengensis Turcz

We developed an environmental and self-propelled harvester with the aim of overcoming the problem of low efficiency, high cost, and complex processing in Artemisia selengensis mechanization harvesting; the developed harvester can complete cutting, conveying, and collecting for selengensis harvesting in an orderly manner. The basic structure and working principle of the machine were determined, including the structure design and parameter analysis of the key components such as the clamping conveyor, steering device, and cutting device. Through theoretical research and a prototype test, we confirmed the machine battery capacity to be 48 V/100 Ah, the conveyor angle θ to be 30°, the adjustable range of the stubble height to be 100-400 mm and the drive motor model, etc. The field experiments indicated that the orderly harvester structure was reasonably designed, easily operated, and helped realize orderly harvesting for selengensis. The mean working velocity, the forward speed, the feeding rate, and the efficiency of the machine can be up to 0.84 m/s, 6 m/s, 0.62 kg/s, and 0.2 hm2/h respectively. The swath quality meets the industry standards and the subsequent production requirements, which contriAgricultural mechanization developmentbutes to facility agricultural mechanization development.

The Randomness of the Wind and Its Impact on Greenhouse CFD Simulation

This paper established the three-dimensional Computational Fluid Dynamics(CFD) simulation modeling for a physical model of Venlo greenhouse. The model used actual wind speed of characteristic Gaussian distribution in the boundary condition entrance, by 500 Monte Carlo experiments to analysis relationship between wind speed and flow field parameters, results indicate that flow field parameters display stochastic characteristic from time domain and probability distribution, and the correlation coefficient are bigger than 0.8 can be considered strong correlation between flow field parameters and input wind speed, so speed entry with a constant value is not accurate during greenhouse CFD simulation, if used wind speed of stochastic numerical characteristic will more realistic.