基于拓扑优化和场协同原理变空隙率多孔介质的等温容器研究

Isothermal process is the ideal process for gas state change in the pneumatic system, and at present it could achieve approximately only with isothermal chamber which stuffed fine wire. Isothermal chamber is used in the testing and control in pneumatic system, and its temperature characteristics are effect by stuffer amount of wire and mass flow of compressed air, which is directly decide the accuracy of test and control. In this project, the fine wire in isothermal chamber is looked as porous media with large porosity, and under the fixed stuffer density conditions the law between its distribution and effective heat transfer coefficient will be studied in order to strengthen heat exchange during discharge process and improve temperature characteristics of isothermal chamber to achieve the isothermal process. At first, topological method would be adopted to optimize the distribution of porous media in order to minimize the thermal resistance from chamber wall to the center and strengthen the outward heat transfer from heat source; The distribution of porous media would be improve further based on field coordination principle to strengthen the convective heat transfer during isothermal chamber discharge process; Numerical simulation would be used to predict the temperature characteristics of isothermal chamber optimized, which would be used to test the flow characteristics of pneumatic components in order to improve the accuracy of test results. The proposed method, which topology method combined with field coordination principle to optimize the distribution of porous media in order to change the effective heat transfer coefficient of the porous medium, can be used to strengthen or weaken the heat exchange, and the results would enrich the artificial porous media heat transfer theory.

等温过程是气动系统中理想的气体状态变化过程，目前唯一借助填充细金属丝形成的等温容器来近似实现。等温容器应用于气动系统的测试和控制中，其温度特性受到金属丝填充量和压缩空气质量流量共同影响，并直接关系到测试和控制精度。本项目把等温容器内的金属丝看作大空隙率的多孔介质，研究在定密度条件下其分布对有效换热系数的影响规律，以强化放气过程中的热交换，改善等温容器的温度特性，实现等温过程。首先采用拓扑方法优化多孔介质分布，使容器壁到中心的热阻最小，强化热源向外传热；并基于场协同原理进一步改进多孔介质分布，来强化等温容器放气过程的对流换热；优化后的等温容器采用数值仿真来预测其温度特性，并用它来测试气动元件的流量特性，提高测试结果精度。本项目所提出的拓扑优化和场协同原理相结合来优化多孔介质分布改变多孔介质有效换热系数，可用来强化或削弱换热，该成果将丰富人造多孔介质的换热理论。

等温过程是气动系统中理想的气体状态变化过程，目前唯一借助填充细金属丝形成的等温容器来近似实现。等温容器应用于气动系统的测试和控制中，其温度特性受到金属丝填充量和压缩空气质量流量共同影响，并直接关系到测试和控制精度。我们把等温容器内的金属丝看作大空隙率的多孔介质，研究了在定填充密度条件下其分布对放气过程热交换的影响规律。首先基于多孔介质理论，以容器中心到容器壁的热阻最小来确定铜丝分层填充，研究了铜丝分层变密度分布对非稳态导热的影响；接着采用拓扑优化方法，进一步改进铜丝分布，来强化等温容器放气过程的容器壁向中心的导热；最后，基于放气热力学模型和压力曲线，得到等温容器放气过程中与孔隙率有关的对流换热经验关系式，为进一步研究铜丝分布对放气过程中对流换热的影响奠定基础。该研究成果不仅能够提高等温容器的等温特性，并且可以应用于研究人造多孔介质的结构分布对强化换热的影响规律。