Research On Flow In Micro-Device Of Mems And Dry-Gas Seals

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.