The Experiment And Numerical Simulation On Bilateral Suction Oblique Airflow Ventilation Of Grain Warehouse

Grain is a vital strategic resource for survival and development of a country.Our country will confront a series of factors affecting grain production and safety in the future time,such as the reduction of cultivated land area,the increase of population by years,the high frequency of climate disasters and the high rate of grain wastage.As a result,food security is always a hot issue that concerned by our country,academic circles and the masses.Grain storage plays an important role in regulation and control,such as the reduction of grain supply,the improvement of people's livelihood and the safety of social security.In order to create an excellent environment for grain reserving,it is necessary to select and apply a kind of reasonable and appropriate mechanical ventilation technology to reduce temperature and moisture content of the grain.This is because temperature and moisture content are two indicators in the process of grain storage.Based on the theory of grain storage and mechanical ventilation technology studied by previous researchers,a new way of mechanical ventilation of grain storage was introduced in this paper,bilateral suction oblique airflow ventilation.And then,the variation of temperature and moisture content in the grain bulk during the mechanical ventilation is studied by using computational fluid dynamics and the theory of heat and mass transfer in porous media.The main research contents are as follows:1)The problems of food security our country faced and the importance of grain storage to a country were analyzed;the contributions of predecessors in grain storage and the research progresses of mechanical storage ventilation field at home and abroad are summarized;the mechanical ventilation technology and the research methods used in this paper were introduced.2)This paper analyzed the theoretical basis of mechanical ventilation of grain storage.The theory of heat and mass transfer in porous media,computational fluid dynamics and a series of related physical parameters were introduced.According to these basic theories,a mathematical model of heat transfer and mass migration during mechanical ventilation was proposed.A warehouse experiment was tested in Huzhu,Qinghai Province to verify the mathematical model.And then,the mathematical model was verified with the method of experiment and numerical simulation.3)With controlling variables,a series of simulation experiments of typical grain warehouse were carried out on the bilateral suction oblique airflow mechanical ventilation process.These experiments simulated the ventilation conditions under different kinds of uncovering width,air supply temperature and air supply humidity.Then the data obtained from the simulation experiments was processed to get temperature field maps,moisture content maps and line graphs of temperature and moisture content as a function of time.Hence the effects of different influencing factors on temperature and moisture content of stored-grain bulk were summarized.4)Finally,the summarization and evaluation of the mechanical ventilation were elaborated,the advantages and disadvantages of the ventilation technology were analyzed,and a series of development suggestions and prospects were put found.