弹性导热仿生功能表面构建原理及减阻机制

The ships, naval vessels and fluid machinery, they work through fluid medium. Fluid resistance is one of the important reasons to cause efficiency reduced and energy wasted. Some studies shown that some warm-blooded creature active control fluid medium to realize drag reduction through the coupling effect of skin elasticity and temperature. Based on above biological coupling phenomenon, a new type of bionic functional surface which have both elastic and thermal properties is put forward and constructed. This kind of functional surface is composited by base material and filler. The low modulus silicone rubber is adopted as base material, and the high thermal conductivity material such as grapheme, nano silver as filler. The coefficient of thermal conductivity and the modulus of elasticity are as objective function, to optimize the characteristic parameters, particle size of filler and filling quantity. Filler's micro distribution form and structure in the thermal interface affect on the thermal conductivity and mechanical properties will be analysis, and its heat conduction model will be set up. The conversion mechanism among stress- deformation-temperature between functional surface and fluid medium and will be studied, the three-field coupling model of fluent-thermal-solid will be obtained. Drag reduction mechanism between thermal interface of high elastic thermal conductive bionic coupling functional surface and fluid system will be revealed from the perspective of elastic deformation to control the flow state and temperature difference in thermal interface to reduce kinematic viscosity of boundary layer. The purposes of above study are to lay a theoretical foundation for bionic drag reduction technology, provide a new idea for the efficiency enhancement and drag reduction technology for the fluid machinery, the ships and naval vessels.

流体机械及船、舰等以流体为工作介质，流体阻力是阻碍装备工作效率提升、造成能源浪费的重要原因之一；研究表明某些温血生物，可利用其表皮弹性、体表温度对液体介质主动控制实现减阻。本研究基于上述生物耦合现象，构建并制备弹性与导热性能兼备的仿生功能表面；该表面以低模量硅橡胶为基材，以高导热性能的石墨烯等新材料作为填料复合而成；并以导热系数及弹性模量为目标函数，对导热填料的性状参数、粒径及填充量进行优化；分析填料在导热仿生功能表面面微观分布形态、结构特征与导热性能及力学性能的关系，进而建立导热模型；研究其与液体介质系统之间的应力-形变-温度耦合及转化机制，获得功能表面的热-流-固三场耦合模型；从材料弹性、温度控制流体边界层流态及运动黏性的角度出发，揭示弹性导热仿生功能表面/流体介质系统减阻机制；为仿生减阻技术的发展提供新的理论基础，为实现流体机械及船、舰艇等的增效、减阻技术提供新思路。

海豚等温血生物，可利用其表皮弹性、体表温度控制流体介质实现减阻的目的。受上述海豚皮肤控制流体介质原理启发，本项目以硅橡胶为基料，以石墨烯为导热填料，通过机械共混法进行弹性导热性能兼备的仿生功能表面的设计及制备，并以导热性能及弹性模量为目标函数，对导热填料的填充量、填料与基料的配比进行了优化，在石墨烯含量为0.36wt%时，其弹性模量及导热性能使得仿生功能表面的减阻效果最好，据此获得了弹性和导热性能兼备的弹性导热仿生功能表面的设计原理及制备参数。.通过SEM、TEM、DSC、DMA等手段对功能表面微观结构及热机械性能进行了分析，获得弹性导热仿生功能表面的导热模型。通过自行研发的仿生功能表面减阻性能测试系统结合合ANSYS APDL模块，对弹性导热仿生功能表面的生热及温度场进行了试验及计算，通过ANSYS WORKBENCH模块，对具有温度边界的弹性导热表面与流体间进行了耦合计算。.上述研究结果表明：不同石墨烯含量的弹性导热仿生功能表面和弹性表面的生热能力相差不大，但是石墨烯的填充量会显著影响它们的导热性能，石墨烯/硅胶复合材料表面的石墨烯添加量为0.36wt%可同时兼具良好弹性与导热性；弹性导热仿生功能表面是一种黏弹性材料，其在交变应力作用下产生力学滞后并发生损耗生热；仿生功能表面依靠导热填料在其内部形成的导热网链实现热量的传递；流速越大，导热系数越大，减阻效果越好。石墨烯含量为1.34wt%的功能表面在流速1.5m/s达到了最大减阻率8.54%，比在同流速下弹性表面的减阻率高1.17%，试样的厚度也会对减阻效果产生影响。通过上述研究，获得了弹性导热仿生功能表面的减阻机制主要源于弹性变形和良好的导热性能两点，弹性变形降低了边界层的速度梯度，良好的导热性能将动态变形产生的内热传递到流体，使边界层温度升高，降低了流体动力粘度，两种因素耦合作用实现了减阻功能。.本项目的研究对于以流体为工作介质的流体机械、舰、船减阻及效率的提升，提供了重要的理论及技术的支撑。