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Micro-scale Analysis of High Knudsen Number Flows

高努森数流动的微观分析

基本信息

批准号：
15206020
负责人：
NIIMI Tomohide
金额：
$ 30.78万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

To describe the degree of rarefaction, Knudsen number (Kn) is defined by the ratio of the mean free path (λ) divided by the characteristic dimension (L) of the flow. Provided that the Kn exceeds 0.01, we cannot approximate the flow as a continuum one, but have to perceive the flow as an atomic or molecular one. We call these flows with large Kn "High Knudsen number flows," which correspond not only to low density gas flows with large λ, but also to gas flows in micro- or nano-systems with small L. In the case of large λ, there appear the strong non-equilibrium phenomena because of few intermolecular collisions. For extremely small L, on the other hand, the flow field is strongly influenced by interaction of molecules with a solid boundary rather than intermolecular collisions. Experimental analyses of thermo-fluid phenomena related to the high Knudsen number flows need the optical measurement techniques based on atoms or molecules, such as their emission and absorption of photons. Howe … More ver, the experimental techniques are behind in development compared with the molecular simulation techniques.In this study, I introduce a resonantly enhanced multiphoton ionization (REMPI) method and a pressure sensitive molecular film (PSMF). We established the 2R+2 N_2-REMPI technique, in which nitrogen molecules are ionized by two steps, i.e., the first step from the ground state to the resonance state (2 photons) and the second step from the resonance state to the ionization state (2 photons). The nitrogen ions are detected as a signal and its spectra depending on the wavelength of an irradiated laser beam are analyzed to measure the rotational temperature through the Boltzmann plot. The 2R+2 N_2-REMPI technique is applied to measure the rotational population in supersonic free molecular nitrogen flows and obtain the non-Boltzmann rotational distribution for P_0・D=15 Torr mm (where P_0 is the source pressure and D is the nozzle diameter). The pressure-sensitive paint (PSP) has potential as a diagnostic tool for pressure measurement in the high Knudsen number regime because the principle of the pressure sensitive paint (PSP) technique is based on oxygen quenching of luminescence. Aiming to apply the PSP to micro devices, we have adopted Langmuir-Blodgett (LB) technique to fabricate pressure sensitive molecular films (PSMFs) using PdOEP and PdMP, and have tested these PSMFs to evaluate the feasibility of the pressure measurement around micro devices. Less

为了描述稀疏程度，Knudsen数（Kn）由平均自由程（λ）除以流动的特征尺寸（L）的比值定义。如果Kn超过0.01，我们就不能把流动近似为连续流，而必须把流动看作是原子或分子的流动。我们称这些具有大Kn的流动为“高努森数流动”，这不仅对应于具有大λ的低密度气体流动，而且对应于具有小L的微米或纳米系统中的气体流动。当λ较大时，由于分子间碰撞较少，出现了较强的非平衡现象。另一方面，对于极小的L，流场强烈地受分子与固体边界的相互作用而不是分子间碰撞的影响。高Knudsen数流动的热流体现象的实验分析需要基于原子或分子的光学测量技术，如它们的光子发射和吸收。豪 ...更多信息本文介绍了共振增强多光子电离（REMPI）方法和压敏分子膜（PSMF）技术。我们建立了2 R +2N_2-REMPI技术。从基态到共振态的第一步（2个光子）和从共振态到电离态的第二步（2个光子）。氮离子被检测为信号，并且其光谱取决于照射的激光束的波长被分析以通过玻尔兹曼图测量旋转温度。用2 R +2N_2-REMPI技术测量了超音速自由氮分子流中的转动粒子数，得到了P_0·D=15 Torr mm（P_0为源压，D为喷嘴直径）时的非Boltzmann转动分布。压敏涂料（PSP）具有作为高努森数区域中的压力测量的诊断工具的潜力，因为压敏涂料（PSP）技术的原理是基于发光的氧猝灭。为了将该技术应用于微器件，我们采用LB技术制备了PdOEP和PdMP压敏分子膜，并对制备的PSMFs进行了测试，以评估其用于微器件周围压力测量的可行性。少