Temperature uniformity optimization with power-frequency coordinated variation in multi-source microwave based on sequential quadratic programming

The focus of this study is to regulate the variation in the input parameters of multiple microwave sources in a high-frequency multimode resonant heating system to achieve uniform heating. First, this study deeply expands the theoretical process of frequency change and proposes a frequency-shifting strategy with hot spot alternation to ensure that the temperature difference range of each hot spot does not continuously expand during the heating process. Then, a sequential quadratic programming algorithm is introduced to reconstruct the input power values to improve the heating efficiency according to the different microwave absorption efficiencies of the heated material at different frequencies. Finally, a numerical calculation model for multi-source microwave power-frequency cooperative heating is established based on the finite-element method, and the temperature uniformity index is effectively calculated. Numerical calculations show that the proposed method can improve the uniformity in single-material heating and multi-material heating cases by 56.8-94.3% and 44.4-76.6%, respectively, over that of fixed-frequency heating while achieving improved heating efficiency on the basis of frequency conversion.