【作者】 何翔；

【导师】 黄卡玛；

【作者基本信息】 四川大学 ， 无线电物理， 2005， 硕士

【摘要】 微波化学是研究微波在化学中应用的一门新兴的前沿交叉学科,而微波化学反应器作为微波发生和作用的器件,则是整个微波化学反应系统中的关键部位,掌握反应器内部的电磁场分布情况和被加热物质内部的温度分布情况就可以很好的指导微波化学反应器的设计与改造,可以控制微波化学反应的速度,改善其内部电磁场分布,使之形成较均匀的电磁场分布和温度分布,防止由于物质的局部过热而导致废品率的升高,由此可以提高化工产品的成品率与转化率。但在实际的应用中,对于谐振腔内部的电磁场分布和温度分布的测量是比较困难的,需要将多个感应探头放置于反应场中进行感应测量,而感应器本身的介入对电磁场分布和温度分布就产生了改变,并且宏观的感应器是不可能测试出微观中存在的局部点的过热现象。因此,寻找一种快捷、高效、准确的反映微波化学反应器内部电磁场分布和温度分布情况的方法就成为了化工界面临的一个重要的问题。 随着计算机运算速度的飞跃提升和各种数值计算方法的不断改进与完善,用计算机来数值模拟复杂环境下的电磁场分布和温度分布就成为了可能。本文就是采用时域有限差分方法(FDTD:Finite-Difference Time-Domain)求解Maxwell方程与热传导方程(Fourier方程)的耦合来计算微波化学反应器内部的电磁场分布和温度分布。为了实现Maxwell方程与热传导方程二者的耦合求解,在空间上,使求解Maxwell方程而划分的Yee氏网格与求解热传导方程而划分的有限容积网格在体积和界面上重合,从而实现空间步长上的耦合;在时间上,更多还原

【Abstract】 Microwave chemistry is one of the fastest growing scientific fields. Microwave chemical reactor plays an important role in microwave chemical engineering. Distribution of the electromagnetic field and the temperature distribution in resonant cavity can guide the design and improvement of the microwave chemical reactor. Improving the uniformity of the electromagnetic field and the temperature distribution can reduce the number of wasted products in chemical industry. However, it is difficult to measure the distribution of the electromagnetic field and the temperature inside the reactor in practice. Some sensors are necessary in the electromagnetic field. However, usually, these sensors will inevitably change the distribution of the electromagnetic field and the temperature distribution. As a result, the measurement of the distribution of the electromagnetic field and the temperature is not exact. Because the sensors in the electromagnetic field are large, the temperature of the micro hot spot cannot be measured. Therefore, we urgently need a good method to measure the distribution of the electromagnetic field and the temperature inside the microwave chemical reactor.With the rapidly increase of the computer speed and the improvement of numerical calculation method, it is possible to calculate the distribution of the electromagnetic field and the temperature under the complex condition. In this thesis, the FDTD (Finite-Difference Time-Domain) method is used to calculate the coupled Maxwell’s equations and Fourier’s heat transport equation. By the aid of this method,the distribution of the electromagnetic field and the temperature can be calculated. In order to solve the coupled Maxwell’s equations and Fourier’s heat transport equation, the Yee’s grid is used. Because the solution is dispersive medium, the permittivity of the solution varies with the temperature. The calculation procedures of the temperature follow the iterative steps: 1. electromagnetic field, 2. power density, 3. temperature rising, 4. permittivity update, 5. electromagnetic field. In this way, two microwave chemical reactors are studied. One is high power microwave chemical reactor with two general magnetrons. The distribution of electromagnetic field inside the microwave chemical reactor is uniform and is in good agreement with the measured results. Another is general microwave oven with only one general magnetron, which is used to heat the reaction to produce CaSO4. The calculated distribution of electromagnetic field in the oven and the temperature distribution in the solution are not uniform, but are in good agreement with the calculated results obtained from FEM (Finite-Element Method) method and the measured results respectively.Based on the above results we can draw a conclusion that the designed "LanTian" microwave chemical reactor is satisfied in the application of microwave chemistry.更多还原