Optimization Design Of Cavity Size And Waveguide Arrangement Of Tunnel Microwave Oven

At present,the design of cavity size and waveguide arrangement of tunnel microwave oven is based on the pattern of "Imitation-Trial-Optimization-Improvement".However,it has some defects,such as less mode number,uneven distribution of electromagnetic field,a long design cycle and high cost.Aimed at above issues,the cavity size,waveguide arrangement and control system of tunnel microwave oven has been designed in this paper,the results obtained are listed as followings:(1)The design method of cavity size has been proposed.According to the conventional process requirements of the tunnel microwave oven,the steps of design of the cavity size are put forward,got the range of the cavity size.Using matlab2008a to solve the resonant frequency of cavity,got the identification of the resonant mode,the number of TEmnp and TMmnp,the total of mode,natural quality factor,resonant frequency,the ratio of odd and even,the ratio of power and volume and other parameters.And also used weighted method to analyze the parameters,finally,the optimum cavity size has been determined base on the analytic results.(2)The influence of waveguide arrangement on electromagnetic has been explored.Using HFSS13.0 to optimize design the waveguide arrangement,through the analysis of the electromagnetic field distribution at the bottom of the cavity,electromagnetic field strength and VSWR,the following conclusions are listed:? In one cavity,the adjacent waveguide should be orthogonal arrangement on the same surface,which could improve the electromagnetic field strength.? In one cavity,the ratio of rows and columns should not higher than 2,less than 0.5 or not equal 1,which could be effectively avoided hot and cold zones or symmetry of the electromagnetic field distribution.The method of increasing the number of waveguides by the number of rows or columns can increase the electromagnetic field strength,but reduce the efficiency of microwave transmission.? If the electromagnetic field distribution of single cavity is uniform,the waveguide of adjacent cavity should be orthogonal,otherwise it should be same.(3)The control system has been designed.Using expert system and fuzzy control to realize the closed-loop control of the temperature of the coix seed pest and mildew control microwave oven.After the expert system acquires the speed of the conveyor belt,through invoking the knowledge base and inference engine,the knowledge is acquired,and then,the total output power of microwave oven is determined,so that the the temperature could reach the set range.Fuzzy control is single-input single-output,the single-input is the difference between the detected values and set values of temperature,the single-output is output power of microwave oven.Through invoking the fuzzy-control rule table to adjust the total output power of microwave oven,and then the temperature steady near the set value.(4)Using above-mentioned method,this paper designed a 81kW rice microwave insecticidal machine which is composed of 7 section cavities.The single cavity is provided with 12 or 15 waveguides,and 90waveguides are provided in total.The optimum size of single cavity is a=146.0cm,b=115.0cm,c=51.0cm,when the number of waveguide of single cavity is 15,the corresponding total of mode,resonant frequency,ratio of power and volume,ratio of odd and even,natural quality factor and optimal thickness are 96,2449MHz,15.63kW/cm3,0.714,1665 and 1.35-2.03cm.When the number of waveguide of single cavity is 12,the corresponding ratio of power and volume is 12.50kW/cm3.The optimum waveguide arrangement was 3x4 and 3x5.The waveguide arrangement of the single cavity and the adjacent cavity adopt the orthogonal.Test shows that the distribution of electromagnetic field and materiel temperature field of the rice microwave insecticidal machine is uniform,the distributed deviating value of materiel temperature field is less than 3?.The material temperature can reach and stable at setting temperature rapidly,and the deviation of temperature fluctuations less than 2?,when the frequency converter operating frequency in 12Hz-16Hz.The temperature setting range is 55??65?.