Structure And Ventilation Process Optimization Of Grain Storage Ventilation System

China is a big agricultural country,among which wheat,the second largest crop in China,has a long planting history and a vast planting area,and a large number of wheat is harvested every year for storage.During the storage process of wheat,its respiration will release heat continuously,which will promote the temperature and moisture in the granary to rise gradually.When the internal temperature reaches a critical value and is in a suitable temperature range,harmful bacteria in the wheat will multiply in large numbers,which will eventually lead to the quality deterioration and rot of wheat in a short time.In order to reduce the mildew rate of grain and the loss of grain during storage,after years of exploration,ventilation technology was combined with grain storage,and low-temperature and low-humidity air was regularly introduced into the granary by mechanical ventilation,so as to reduce the temperature and moisture of grain in the granary.Finally,the storage time of grain was prolonged and the quality of stored grain was guaranteed.In recent years,due to the spread of the epidemic in COVID-19,the problem of food security has become particularly severe,so higher requirements have been put forward for the mechanical ventilation technology of grain storage.In this paper,wheat is selected as the research object.Starting from the ventilation process,combined with the basic theory and application research of mechanical ventilation,the ventilation structure,process scheme and control link of stored grain ventilation are optimized by combining computer simulation and platform experiment,so as to ensure the quality and safety of grain under the optimal energy consumption expenditure,and finally achieve the goal of safe,qualityguaranteed and energy-saving green stored grain ventilation control.The specific contents are as follows:(1)Structural optimization of grain storage ventilation systemAccording to the disadvantages of the existing granary ventilation structure,the ventilation system structure is improved,and the corresponding mathematical model is constructed.With the help of simulation software,the ventilation effects of three ventilation system structures are simulated and analyzed.Using the uniformity of moisture and temperature distribution in granary as the evaluation index of ventilation effect,it is verified that the improved ventilation system has superior structural performance.(2)Optimization of process parameters of grain storage ventilation systemIn order to shorten the time of mechanical ventilation of wheat in the granary and reduce the energy consumption in this process,the multiple nonlinear regression method was used to fit the functional relationship between air temperature and relative humidity at the vent,initial moisture and temperature of wheat and ventilation time,and the particle swarmgenetic hybrid optimization algorithm was used to optimize the ventilation time of wheat,and finally the optimal technological scheme was obtained.(3)Research on Water Activity Characteristics of Wheat Mechanical VentilationBecause the water activity of wheat can reflect the growth of microorganisms in the granary,the quality of wheat in the granary can be obtained.Therefore,through a series of single-factor experimental analysis,the effect law of various ventilation parameters on wheat water activity is obtained,and the ventilation conditions to reduce wheat water activity are obtained,and the correctness of the optimal ventilation parameter combination obtained above is verified.(4)Research on Temperature and Humidity Control of Stored Grain VentilationIn order to realize the automatic control of temperature and humidity in the process of stored grain ventilation,the PID control mechanism was introduced to establish the corresponding objective optimization function of the granary,and the classical PID control algorithm and fuzzy PID control algorithm were selected for simulation analysis in MATLAB environment.By comparing the two evaluation indexes of overshoot and response time,it was verified that the fuzzy PID control algorithm could achieve the requirements of fast,efficient and stable stored grain ventilation control.