橡胶微波加热硫化的有限元分析

运用有限单元法求解Maxwell方程和传热方程,并采用ANSYS有限元软件计算和分析橡胶传统的热量由外向内传递的加热过程和微波加热过程。结果表明:微波加热硫化橡胶加热时间短,效率高;橡胶内的电场强度分布、焦耳热密度分布和温度分布都不均匀;随着微波加热时间的延长,胶料内的温度提高,但处于较高硫化温度的胶料范围几乎无变化。     

波导对橡胶微波加热硫化的影响

采用ANSYS有限元分析软件分别模拟橡胶在圆波导和同轴波导两种模式下的微波加热硫化过程。结果表明:同轴波导模式下胶料的微波加热效率低于圆波导模式,但同轴波导模式下胶料经微波加热后,胶料的最高和最低温度的差值较小,即同轴波导模式下加热胶料内的温度分布较均匀。     

微波电场对高凝原油体系中分子性质的影响

为进一步提高微波作用效果,采用分子动力学模拟方法,重点研究了微波场对高凝模拟油体系的影响.分析了高凝油的性质与其分子之间的内在联系以及微波电场对高凝油性质的影响规律.结果表明,微波电场强度和频率对原油性质有很大影响,在适当电场强度下,电场的加入阻碍了分子运动,抑制了石蜡分子的聚集,使得体系黏度降低.每种物质对微波的响应...     

电场分布对R123沸腾换热的影响

采用6种不同电极布置方式,进行了不同电势和热流密度下的R123池沸腾换热的试验研究。通过数值分析,计算了不同电极布置下换热面上的电场强度及分布。不同的电极布置,会导致换热面上电场强度和电场均匀性两方面的变化。结合试验和电场分布的计算结果,分析了电场均匀性、电场强度、热流密度与沸腾换热效果之间的关系。结果表明,在低热流密度下,电场分布对沸腾换热影响较大;而在高热流密度下,影响较小。电水动力学（EHD）强化换热效果是电场强度和电场均匀性综合作用的结果。     

胶料热物性对微波加热硫化温度场的影响

采用闪光导热分析仪和差示扫描量热仪对异戊橡胶(IR)在硫化过程中的热物性参数进行测量,得出热导率和比热容随温度的变化规律。同时采用ANSYS有限元分析软件对IR进行三维建模,并对其微波加热硫化过程进行数值模拟,得到热导率和比热容恒定或随温度变化等4种情况下胶料内部的焦耳热密度分布和温度分布。结果表明,热导率变化对胶料温度分布影响不大,而比热容变化的影响较大。     

微波电场对甘油水溶液体系中氢键的影响

通过分子动力学模拟考察微波电场对不同水含量甘油溶液中氢键的影响。研究发现：甘油含量高时,甘油分子在溶液中以较大的团簇结构存在,水分子以较小的团簇结构或游离状态存在,电场作用下,大的甘油分子团簇变成较小的团簇并且变得更加有序;随着电场强度继续增加,甘油分子整体结构变化不大,但是团簇结构边缘甘油分子氢键断裂,变成游离状态。对于水分子而言,其较小的团簇结构在电场作用下被打开,团簇结构消失,水分子在电场方向上整齐排布,且电场强度继续增大,其结构变化不大,同样个别水分子氢键断裂变成游离状态。因此,甘油浓度高时,水分子间氢键数减少,甘油分子氢键数先增大后略微减少;甘油浓度低时,水分子氢键数先增大后略有减少,甘油分子间氢键减少。     

微波裂解腔体波导管馈口分布对废旧橡胶裂解的影响

在废旧橡胶的微波裂解腔体上设置4个波源和相应波导管,使用HFSS软件建立微波裂解模型,对裂解腔体上波导管馈口的分布方式和间距进行电场分布和微波能损耗分析。结果发现,微波裂解腔体上相邻波导管馈口中心间距为150 mm且波导管馈口呈正交分布时,相邻波源之间相互干涉最小,废旧橡胶裂解的微波能有效利用率最高,微波能反射损耗最低。本仿真结果可为废旧橡胶微波裂解腔体设计提供依据。     

熔体静电纺丝的电场分布及其对PET纤维成形的影响

借助ANSYS软件模拟聚对苯二甲酸乙二酯(PET)熔体静电纺丝在不同参数(纺丝电压、接收距离、接收板面积)条件下的电场分布,探讨电场分布对熔体静电纺丝PET射流运动与纤维形貌的影响。结果表明,在单喷嘴–平板结构模型中,提高纺丝电压将增强整体空间电场强度,使电场对PET熔体射流的控制力加强,PET熔体射流的摆动半径减小,当纺丝电压由24 k V升高到30 k V时,摆动半径由11.7 mm减至9.9 mm,而摆动角增大,由10.1°增至11.2°,PET纤维直径显著减小,由3.275μm减至2.202μm;接收距离的改变对接收板表面电场的影响显著,随着接收距离的增加,PET射流的直线段比例明显下降,当接收距离由50 mm增加至90 mm时,PET熔体射流的直线段比例由68.0%减至54.0%,PET纤维直径在适中接收距离(70 mm)下表现较细,可达2.184μm;接收板面积的减小加强了对PET熔体射流的控制,使PET熔体射流直线段比例显著增加,当接收板面积由15 cm×15 cm减小至10 cm×10 cm时,PET熔体射流直线段比例由68.0%增加至82.6%,摆动半径减小,由9.9 mm减至4.2 mm,沉积角因PET熔体射流贴服接收板而减小,由12.2°减至9.1°,PET纤维直径稍有增加,由2.202μm增加至2.537μm。     

吸波剂协助低阶煤微波热解能量场分布数值模拟研究

吸波剂协助煤微波热解技术可实现煤的清洁高效转化,吸波剂协助煤微波热解技术与数值模拟技术相结合,可进一步优化微波热解产物特性。将电磁场能量守恒方程、固体热传导方程和几何模型耦合,运用COMSOL软件建立了适用于吸波剂协助低阶煤微波热解反应的电磁-传热模型,考察了兰炭(BC)、Fe₂O₃和Fe₂O₃/BC三种不同种类吸波剂协助煤微波热解的微波腔体电场和煤样温度场的分布特性和强度变化,并与煤微波热解实验进行了对比验证。结果表明：吸波剂种类对微波腔体的电场和煤样的温度场的分布位置和分布区域形状没有显著影响,而对两者的分布区域面积和强度存在较大影响。吸波剂按对电场的分布区域面积和强度的影响从大到小依次为Fe₂O₃/BC、兰炭和Fe₂O₃,煤样的温度场呈现出右高左低的分布趋势,且高温区域形状呈羽状。三种吸波剂中,Fe₂O₃/BC吸波剂的电场强度最大,约为9.79×10^4<...     

铝合金棱角部位阳极氧化膜形貌分析

对铝合金进行阳极氧化,并进行化学浸泡试验和点滴试验,用电子探针观察棱角部位氧化膜的形貌。结果表明,试样表面部位氧化膜化学浸泡试验180min无氢气泡逸出,点滴试验时间大于30min没有观察到腐蚀迹象,达到了航空工业部标准（HB5055-1993）,耐蚀性能优异。然而,试样的棱、外角和内角观察到氢气泡逸出,该处氧化膜产生破损,导致基体金属遭受腐蚀。电子探针分析发现,铝合金棱角部位氧化膜产生裂纹。其原因是棱角部位氧化膜存在边缘效应,阻止了氧化膜在三维方向连续生长,与表面部位相比,棱角部位氧化膜变薄,导致基体金属棱角部位优先遭受腐蚀。     

Effect of the Inside Placement of Electrically Conductive Beads on Electric Field Uniformity in a Microwave Applicator

Non-uniform heating is a major issue in microwave applications, mainly due to inherently uneven distribution of electromagnetic energy in the microwave applicator. In this work, our aim is to improve electric field distribution uniformity by utilizing microwave reflection from electrically conductive beads placed in the microwave oven. The effects of position, size, and number of electrically conductive beads on the electric field distribution were numerically investigated, and validated through water-load experiments in the cavity. It is found that uniform electric field distribution was realized to some extent by appropriate placement of electrically conductive beads; meanwhile, average electric field intensity in the microwave oven was increased.     

电场对汽液平衡的影响

利用电场的极化效应对物质分子间力的影响 ,研究了电场对乙醇 水、丙醇 水、醋酸 水体系汽液平衡的影响。结果表明 ,外加电场对这三个体系的汽液平衡均有影响 ,但不能明显改变共沸物系的共沸温度和共沸组成 ,即不能明显使共沸点漂移。电场使体系中介电常数大的组分在汽相中的含量增大 ,介电常数小的组分在汽相中的含量则减小。介电常数相差越大 ,越有利于电场的极化分离     

The Effect of Electric Field on Heat and Mass Transfer

The process of evaporation from flat and cylindrical surfaces into an air stream flowing tangentially to them has been experimentally investigated. An electric field has been induced in the system from an emitting electrode in the form of needles arranged in a plate placed above the grounded water surface. A decisive effect of the ion-drag force on the evaporation process has been confirmed in the experiments proving that the ionic wind had intensified the process. About 8-fold increase in the average values of the heat and mass transfer coeficients caused by an electric field of an intensity 5 kV/cm in comparison with those obtained without the field has been observed. General correlations relating the evaporation rate to the process parameters have been suggested.

The system under consideration can be treated as a model one for a solid dried at a constant rate period. The drying experiments with a kaolin plate have been carried out under conditions corresponding to those applied in water evaporation from a flat surface to provide the same values of the heat and mass transfer coefficients. Intensification of the drying process by the electric field, similar to that of water evaporation, has been recorded.     

微波单模腔反应器外场中磷石膏碳热还原反应研究

采用微波单模腔反应系统,研究了以石墨既作为吸波材料,又作为还原剂的磷石膏碳热还原反应。结果显示,n(C)/n(S)为44～46,反应温度为1 100℃以上,反应时间为15 min,硫酸钙的分解率可达87%。微波场中硫酸钙的反应速率高于普通碳热还原反应。     

Electric Field Effect on Dielectric Constant of Glycine Phosphite

Study of the effect of an external electric field on the dielectric constant in the paraelectric phase of ferroelectric glycine phosphite crystals has been performed. The dielectric constant behavior under the bias external field has been analyzed in the framework of Landau theory. It is shown that the ferroelectric phase transition is of the first order very close to a tricritical point and the calculated value of the thermal hysteresis is ΔT ≅0.1 K.     

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.     

Effect of Electric Field/Current on Liquid Phase Sintering

The sintering behavior of alumina containing different amounts of calcium–aluminum–silicate glass as sintering aid was analyzed under AC electric fields between 0 and 150 V/cm. Liquid phase sintering was enhanced by the electric field, and “flash sintering” behavior depending on the current density and power dissipation within the specimen could be observed. Current flowed only through the liquid phase at high temperature and enhanced the densification process by two effects: Joule heating and athermal response of the viscous liquid under the electric field. Joule heating increased the temperature within the specimen, whereas the applied electric field reduced the viscosity of the liquid phase promoting a more effective matter transport.     

微波加热多层橡胶复合材料的温度场分布及界面特性研究

针对不同波源下微波加热多层橡胶复合材料,建立基于Maxwell方程的一维非稳态有源加热偏微分方程(PDE)模型,以丁苯橡胶材料和丁腈橡胶材料复合为例,采用时域有限差分法进行模拟仿真,研究多层(两层)橡胶复合材料在单/双波源下材料厚度和微波功率对加热温度场和界面特性的影响。结果表明:微波功率变化会影响多层橡胶复合材料加热温度分布;在叠加橡胶材料的交界面处,微波振幅会有微小变化;将介电损耗小的橡胶材料直接暴露于微波源,有利于微波穿过介电损耗小的橡胶材料向深处传播,且各层橡胶材料厚度宜控制在临界穿透深度以下;相对于单波源加热,多波源加热能改善多层橡胶复合材料加热的均匀性。与传统有限元模型的分析结果进行比较,验证了本研究模型的有效性。