【作者】 徐洁；

【导师】 谷传纲；

【作者基本信息】 上海交通大学 ， 流体机械及工程， 2007， 博士

【摘要】 微尺度器件内部流动的研究是微机电系统研究领域中不可或缺的一部分,是近年来国内外学者关注的研究前沿。本方面国内外研究水平很不平衡,国内起步较晚,相关研究最早开始于上世纪九十年代,近十几年来逐渐成为研究热点,受到广泛的关注。微尺度通道是微尺度器件的重要组成部分,本文通过实验与数值计算,对静止与旋转的、尺度在10-50微米左右的微通道内部流体流动现象与规律进行了详细的研究,主要包括以下几个部分的内容:第一部分:微管道内流体流动特性研究对公称直径为20微米和50微米的微圆管道内的压力驱动氮气流动进行了定量实验研究,得到了微尺度圆管道内的压力-流量曲线。试验结果表明,当Ma数小于0.3时,微管道内气体流动必须按可压缩流动考虑。开发了二维微通道内有边界滑移的流体流动的数值计算程序,其中压力与速度的耦合采用SIMPLE算法。数值计算结果表明,稀薄效应使微通道内的流体流量较宏观理论值为大,同时流量也受流动的Kn数及微通道的切向动量调节系数所影响。通过三维数值计算与实验结果的比较和分析,Ma数小于0.3,低Kn数范围内,气体的可压缩效应与边界滑移效应均存在,并可求得微管道的切向动量调节系数。数值分析表明可压缩效应对流动的影响占主导地位,而边界滑移效应对流动的影响很小,从工程应用的角度考虑,可忽略不计。第二部分:微射流放大器内流体流动特性研究对液体偏向型微射流放大器内部流场进行三维数值计算进行了有益的尝试,得到了平均流量增益曲线。计算结果与分析表明,在液体微尺度流动理论尚不完善的情况下,求解N-S方程可对微射流放大器内部流动进行预估,将其内部流场分析与外部运行特性分析有机地结合起来,为今后的实际应用和优化设计提供了较为可靠的依据。第三部分:干气密封微间隙内流体流动特性研究提出了旋转螺旋槽气体密封内部流动的近似解析算法,并在旋转状况下微间隙流动的三维流场数值模拟方面进行了尝试和探索,提出虑及气体的可压缩性与物性参数变化的修正方法,并经与经典文献中试验结果比较表明,上述的方法是可靠有效的。更多还原

【Abstract】 The study of fluid flow in Mirco-device is one of main aspects faced in MEMS and gets more attention from more domestic and foreign researchers. There is much difference in this field between domestic and foreign research. The domestic study of micro-fluid starts at nineteen’s in the last century and gets more focus in recent years. Mirco channel is one of main parts in MEMS. In this paper, the detailed investigation by experimental and numerical method is given to the fluid flow in static and rotary micro channel with characteristic dimension 10-50 um. The main contributions of this paper are as follows:The first part is for study of fluid flow in micro channels.The pressure-driven Nitrogen gas flow in micro pipe with nominal diameter 20 and 50 um is studied by experimental method, and pressure-flow rate curve in micro pipes is obtained accordingly. The experimental results show that the compression effect should be considered when addressing the fluid flow in micro pipes.The numerical program to analyze the flow in 2D micro-channel with slip boundary is developed in which the SIMPLE scheme has been adopted to coupling the velocity and pressure. The numerical results show when the rarefaction effect is being considered the flow rate is large than the theoretical value. In the meantime, the Kn number and tangential-momentum-accommodation coefficient also have some effects on the flow rate.The 3D calculation is also used to address the flow in micro pipes. The comparison between numerical value and experimental data shows that when Mach number is less than 0.3 while Kn is in lower range, the effects of gaseous compressibility and slip are both present. The tangential-momentum-accommodation coefficient (TMAC) also can be deduced. It is found that the compressibility effect plays main role to the flow while slip effect is small. From point of engineering, the slip effect can be neglected.The second part is for the study of fluid flow in microfluidic amplifiers.The 3D numerical calculation for flow in liquid jet-deflection type microfluidic amplifiers is conducted, and the average flow gain is obtained. The numerical results show that the solving N-S equation is the reasonable way to address the flow in microfluidic amplifiers, for the micro flow theory for liquid has not been constructed. Combination of flow field analysis and external running characteristic will be the practical solution for optimum design and possible application. The third part is for the study of fluid flow in dry gas seals.An approximation algorithm to investigate the flow in the spiral dry gas seal is developed. The 3D flowfield within micro gap in the spiral dry gas seal is studied numerically. A modified method is presented, in which gas compressibility and the variety of fluid physical properties is to be considered. The comparison with the experimental data in classic literature shows that this method is reliable.更多还原