射频加热系统辐射泄漏量与上极板电压研究

发布时间：2018-06-19 01:14

本文选题：射频 + 泄漏电磁辐射　；参考：《西北农林科技大学》2015年硕士论文

【摘要】：射频(Radiofrequency,RF)加热是一种电磁介电加热技术,因其具有整体快速的加热特性而被广泛应用于木材的干燥胶合、塑料焊接、农产品及食品的生产加工业中。在射频加热技术大规模应用于农产品、食品加工领域的发展进程中,对加工工艺和加工设备的优化改进着重要的工业化发展意义。论文主要从射频加热系统的辐射泄漏量和上极板电压两方面入手,对射频加热系统的设备特性进行研究,为该技术的工业化应用和优化提供技术参考和理论依据。安全和稳定的系统运行条件对射频加热技术的工业化发展意义重大,然而关于射频加热系统辐射泄漏安全的研究却很缺乏。研究针对实验室内两台27.12MHz射频加热系统进行了电磁辐射泄漏量检测,并根据国际标准对系统的操作安全性进行了评估,并给出了相关优化改进建议。在射频加热技术的工业化应用研究中,有限元模拟以其具有方便、快速的特点而作为一项主要的研究手段。在对射频加热的模拟过程中,上极板电压值是一项重要的输入参数,而且难以快速并准确确定。论文基于分析、模拟和实际测量的方法,建立了极板电压估算模型,实现了上极板电压的精准、快速估算,提高了计算机模拟研究效率。具体研究内容和结论如下:(1)在辐射泄漏量研究试验中,利用高频电磁场强探测仪分别对不同测量距离、极板间距、加载状况、屏蔽情况下的电场强度、磁场强度进行测量,并根据测量值计算功率密度,最后对射频加热系统物料出、入口屏蔽门帘的效果进行了分析。结果表明电场、磁场强度随测量距离、极板间距的减小而增加。以1kg自来水作为射频加热负载,在加载情况下,随着射频输出功率的增大,泄漏电场强度减小。Jiyuan射频加热系统的物料出口和入口处屏蔽门帘对电磁泄漏有明显效果,泄漏电场强度和功率密度有显著的减小。(2)极板间距130mm处泄漏电场、磁场强度的测量平均值均低于国际非电离辐射保护委员会(ICNIRP)和电气与电子工程师协会(IEEE)的标准规定。为进一步减少操作人员在日常射频加热系统操作中受到的电磁辐射,建议在射频加热系统物料出入口增加屏蔽门帘、避免系统空载运行、减少操作人员在辐射区域的作业时间。(3)在5种不同的极板间距下分别对3kg黄豆的进行了射频加热试验。基于试验结果建立了计算机模拟模型,得出模拟电压。根据分压和整流原理制作了上极板电压检测装置来实际测量射频加热系统的上极板电压。根据红外热像仪、光纤传感器和热电偶对物料实际加热速率进行测量并通过分析计算法来计算上极板电压。(4)电压研究结果表明电压值随极板间距的减小、加热速率的增加而增加。选择物料三层平均温度的计算电压值和阳极、实测电流的回归模型作为最佳电压估算模型,并应用于计算机模拟分析。
[Abstract]:RF heating is a kind of electromagnetic dielectric heating technology, which is widely used in wood drying bonding, plastic welding, agricultural products and food production and processing industry because of its integral and rapid heating characteristics. In the development process of large-scale application of RF heating technology in the field of agricultural products and food processing, it is of great significance to optimize and improve the processing technology and processing equipment. In this paper, the characteristics of RF heating system are studied from the aspects of radiation leakage and upper plate voltage, which provide a technical reference and theoretical basis for the industrial application and optimization of this technology. The safe and stable operating conditions of the system are of great significance to the industrial development of radio-frequency heating technology, but the research on the radiation leakage safety of the radio-frequency heating system is lacking. In this paper, the leakage of electromagnetic radiation is measured for two 27.12MHz RF heating systems in laboratory. The operating safety of the system is evaluated according to international standards, and some suggestions for optimization and improvement are given. In the industrial application of RF heating technology, finite element simulation is one of the main research methods because of its convenient and fast characteristics. In the simulation of RF heating, the voltage value of the upper pole is an important input parameter, and it is difficult to determine quickly and accurately. Based on the methods of analysis, simulation and actual measurement, a voltage estimation model of the electrode plate is established in this paper, which realizes the accurate and fast estimation of the voltage of the upper plate and improves the efficiency of computer simulation research. The specific research contents and conclusions are as follows: (1) in the radiation leakage research experiment, the high frequency electromagnetic field strong detector is used to measure the different measuring distance, the distance between the polar plates, the loading condition, the electric field intensity and the magnetic field intensity under the condition of shielding, respectively. The power density is calculated according to the measured value. Finally, the effect of shielding the door curtain at the entrance of the RF heating system is analyzed. The results show that the electric field and the magnetic field intensity increase with the decrease of the distance and the distance between the poles. Using 1kg tap water as RF heating load, with the increase of RF output power, the leakage electric field intensity decreases. Jiyuan RF heating system has obvious effect on electromagnetic leakage by shielding door curtain at the outlet and entrance of RF heating system. The leakage electric field intensity and power density are significantly reduced. The average magnetic field intensity is lower than the standard of ICNIRP (International Committee for the Protection of Non-ionizing radiation) and IEEE (Institute of Electrical and Electronic Engineers). In order to further reduce the electromagnetic radiation of operators in the daily operation of radio-frequency heating system, it is suggested that the screen curtain should be added at the material entrance of the RF heating system so as to avoid the system running without load. The radiofrequency heating experiments of 3kg soybeans were carried out under five different polar plate spacing to reduce the working time of operators in the radiation area. Based on the experimental results, a computer simulation model is established and the simulated voltage is obtained. According to the principle of partial voltage and rectifier, a device for measuring the upper plate voltage of RF heating system is made. According to the infrared thermal imager, optical fiber sensor and thermocouple, the actual heating rate of the material is measured and the voltage of the upper plate is calculated by the method of analysis and calculation. The results show that the voltage value decreases with the distance between the poles. The heating rate increases with the increase of heating rate. The calculated voltage and anode of the three-layer average temperature of the material are selected, and the regression model of the measured current is used as the best voltage estimation model, and applied to the computer simulation analysis.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O441.4

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