Numerical Simulation And Experiment On Paddy Ventilation Resistance

In our country, the production, storage and consumption of rice is more, the importance of regulating quality and ventilation, drying, reduce moisture and moisture-proof can not be ignored during the storage of rice. Because of experimental error, the different climate, geographical conditions and different planting varieties at home and abroad, the empirical formula calculation results about the rice ventilation resistance is not accurate, it is necessary to carry out further research on change law of ventilation resistance and ventilation resistance of rice.In this paper, based on the discrete element method and the theory of fluid mechanics, rice ventilation resistance numerical simulation model is established, the CFD- DEM coupling simulate the vertical pipe constraint of rice particle group in the different wind speed and the change rule of ventilation resistance layer depth.Through constructing rice ventilation resistance test bench, the experiments have been carried out to verify the results of numerical simulation, and analyzed the two varieties of rice under different factors affect the change of ventilation resistance. The main content of this paper is as follows:(1) Based on CFD- DEM solving theory and mathematical modelBased on the discrete element method and the theory of fluid mechanics, the application of discrete element method software EDEM and the application of computational fluid dynamics software Fluent solving method is introduced and analyzed, and build a mathematical model suitable for numerical simulation of the ventilation resistance of rice.(2) Based on the different grain type ventilation resistance numerical simulationThe CFD- DEM coupling to simulate the three grain types in the vertical pipe constraint by different wind speed and depth of ventilation resistance change law. The results showed that: the range of depth is 0~2m, the grain resistance of the material barrel is gradient, and the ventilation resistance of the rice is related to the density of the accumulation of the grain. The resistance of different varieties of rice in the same condition had the same trend, and the resistance value increased firstly and then decreased with the increase of spherical degree.(3) Numerical simulation results by test verificationBy building ventilation resistance test bench of rice, based on CFD- DEM ventilation resistance test carried out to verify the results of numerical simulation. The results showed that with the grain depth and the change of the apparent wind speed, there is a certain error between the results of numerical simulation and test, but the grain layer the change trend of resistance as a whole are the same, illustrates the feasibility of numerical simulation of ventilation resistance in rice based on CFD-DEM method, the result has a certain reference value.(4) Study on the characteristics of paddy ventilation resistanceLayer depth, the apparent wind speed, the rice moisture content as the test factors, the ventilation resistance of rice as the test index, adopting quadratic regression orthogonal rotation combination test method was carried out on the rice ventilation resistance test, according to the results, building the Regression equation between the ventilation resistance and the three test index.The results showed that: for the ventilation resistance factors of rice varieties Dongnong 8006, Nuo 418 contribution rate followed by the superficial velocity, the grain depth and moisture content.This paper through to rice ventilation resistance and ventilation resistance change law were studied, the reasonable for matching fan ventilated storehouse, design the structure of the ventilation pipe, as well as the equipment is important guiding significance for design optimization and practical significance.