Research On Microwave Oven Simulation And Performance Improvement

The innovation of science and technology has improved people's quality of life.Microwave ovens are important household appliances in daily life,flat-panel microwave ovens quickly occupy the market with better cavity cleanliness and higher space utilization.However,the poor homogeneity of flat-plate microwave ovens has always plagued the entire industry.In addition,the simulation and experimentation of the uniformity of microwave oven heating are performed using water.The fluidity of water is relatively strong,which can only reflect the temperature of limited point in the microwave cavity,it can not completely reflect the flat microwave oven heating uniformity.This paper presents a method to measure the uniformity of microwave heating by using food.A modeling method to determine the complex permittivity of food materials has been introduced according to the classical Debye model and the relationship between conductivity and total dissolved solids.The mixed expression of complex dielectric constant was established by using the water content and dry part of food,and then the complex dielectric constant of food was measured by comparison of the vector network analyzer.This modeling principle is validated as the modeling results have good agreements with measurements.When using solutions and food stuff for which the water and salt content are well controlled,such as standard saline and mashed potato,the error of complex permittivity is smaller than 3 and those of the heating results are smaller than 4? compared to measurements.The food model showed good consistency in the results of simulated heating and actual heating.Beef has a complex composition and contains more inorganic salts,so it is difficult to reflect the complex permittivity by measuring its TDS value.However,it was found that these contents could contribute to the complex permittivity significantly.To make this modeling method applicable to real food materials,methods to accurately determine the complex permittivity of the dry part of the food needs to be developed.The analysis in this paper shows that,the standing wave formed by the electromagnetic wave in the cavity of the flat microwave oven is the main reason of uneven heating.Changing the cavity configuration of the flat microwave oven can improve the uniformity of the standing wave distribution,but the uniform electromagnetic field distribution cannot be obtained.Though the electromagnetic stirrer will reflect more microwave energy back to the magnetron under no-load conditions,it can continuously change the standing wave position of the electromagnetic wave to form a statistically uniform electromagnetic field.This paper proposes an electromagnetic stirrer structure which can moves in the vertical direction based on this conclusion.The new electromagnetic stirrer will not significantly increase the manufacturing cost and difficulty of flat-plate microwave oven.Different from the traditional electromagnetic stirrer,the new can enhance the uniformity of heating of flat microwave oven.Finally,mashed potato model was established in software to simulate the heating process.It was found that,new electromagnetic stirrer can make positive effects on heating uniformity.