Finite Element Analysis of Mode Stirrer Impact on Electric Field Uniformity in a Microwave Applicator

Nonuniformity of the electromagnetic field in microwave ovens is assumed to be one of the reasons for nonuniform drying of materials. There are several approaches that are partly able to eliminate such a negative phenomenon. One of them is a placement of mode stirrers in the microwave (MW) applicator. Therefore, the goal of this study was to numerically investigate the influence of a proposed fan-like mode stirrer on the uniformity of the electric field (EF) in an experimental MW device. This was done with the help of 3D harmonic high-frequency finite element (FE) simulation of the EF distribution in the MW applicator. Within the work, two FE models of the MW device were built, analyzed, and compared to each other. The first FE model does not incorporate the mode stirrers. The other one has two mode stirrers, each placed in front of two waveguide ports. In both models, the EF uniformity is studied in 10 height levels and in two mutually perpendicular directions. Change of the EF uniformity was analyzed in terms of coefficients of variation (CoVs) of the electric vector sum across the applicator. Results of simulations show that the mode stirrers decrease CoVs (EF uniformity) in 8 of 10 studied height levels ranging from 2 to 20% and increase them in two topmost levels ranging from 3 to 7.3%. With respect to the fact that the simulations did not consider the mode stirrers’ rotation, the calculated effect might be lower than the actual effect. However, harmonic FE analysis was shown to be an efficient way for investigating, to a degree, the mode stirrer influence on the EF uniformity in a microwave applicator.