Reseach On The Effects Of Dielectric Materials For Microwave Cavity Matching

The microwave oven has experienced great development especially in exterior design and functional improvements since its invention more than 60 years ago. Also materials’ using of microwave ovens have made a lot of improvements. Microwave oven cavity materials involving metals, ceramics, organic materials and inorganic coating materials, glass materials and so on. The dielectric materials will not only serve as decoration, anticorrosion and bearing place, but influence the microwave matching largely. Heating uniformity of microwave oven is a key problem for microwave heating. Turntable,mode stirrer and so on are designed for improving the heating uniformity of microwave oven, and the improvement on this is still needs a lot of researches.This thesis did part of the work mainly using electromagnetic field simulation method for dielectric materials in the microwave oven and microwave oven heating uniformity:1. Analyzed the differences between the ceramic bearing material plate and glass type plate in the microwave oven energy efficiency, microwave heating uniformity, no-load test, infrared thermal image distribution, cold matching by experiment and simulation. We get the conclusion: The heating uniformity of M23 L platform including ceramic plate cavity can be higher 20% than glass plate cavity. To guide the actual bearing plate matching: when the electromagnetic parameters and the thickness of the content medium plate in a quarter of impedance matching layer are more conducive to the microwave performance improvement. Medium plate with bigger relative permittivity can gather electric field and raise the utilization ratio of the microwave; Medium plate with bigger loss tangent value can be used for heating, such as microwave thawing.2. Analyzed the differences between high temperature oil coating, enamel coating and uncoated stainless steel materials in the microwave efficiency, heating uniformity, light and heat as the difference of distribution, etc. The existence of the oil coating does not affect the M23 L platform energy efficiency and heating uniformity of microwave oven and has nothing to do with matching. The existence of the enamel coating reduces the microwave heating efficiency about 2% of 25 L platform; coating thickness differences as well as the sintering process and so on will have slight differences on microwave heating uniformity. Also we analyzed the efficiency by water load with different quality basing on the evaluation standard. The study contains the actual energy efficiency test, matching of cold test and simulation of electromagnetic field. Finally we conclude: with little environmental impact, water load changes 900g-1100 g, which difference of energy efficiency is about 1%, will not affect M23 L platform microwave energy efficiency evaluation.3. Using Eigen mode to solve electromagnetic field simulation and applying this to the existing model to improve microwave heating uniformity. Comparing electric field energy and magnetic energy after the microwave cavity structure optimization; this method adds inside electromagnetic wave mode can be set up and increased heating uniformity about 24.6%.