Photonic Analyses of High Knudsen Number flows

在分析高努森数流动，如微纳器件周围或内部的低密度流型和流场时，必须将流体视为原子或分子的流动。本研究利用分子传感器、数值模拟和动力学理论对高克努森数流动进行了实验研究。压敏涂料(PSP)是一种利用氧猝灭发光进行压力测量的诊断工具，应用于塞式直线喷管。将PSP应用于微纳米流场，基于Langmuir-Blodgett技术研制了压敏分子膜(PSMF)。对许多发光分子进行了评估，以澄清压力敏感性。利用PSMF，得到了微通道和微喷管的压力分布。计算结果与数值模拟结果吻合较好。从机理上考虑，PSP反映的是氧数通量而非分压。为此，从动力学理论和DSMC数值模拟两个方面研究了氧数通量与分压的关系。在高克努森数区域，PSP的发光强度表现为氧分子对表面的冲击压力，而不是氧气的气体压力，分子束经常被用作气体-表面相互作用的探针。采用共振增强多光子电离(REMPI)方法测量了氮分子束的转动能分布。成功地获得了REMPI谱，并且。旋转温度偏离了平移温度。结果还表明，转动分布呈现非玻耳兹曼特征。

In analyses of high Knudsen number flow, such as low density flow regime and flow fields around or in micro-/nano-devices, it is essential to treat the fluid as a flow of atoms or molecules. In this research, high Knudsen number flows have been investigated experimentally using molecular sensors, numerically with the DSMC simulations and theoretically by the kinetic theory.Pressure Sensitive Paint (PSP), which is a diagnostic tool for pressure measurement using oxygen quenching of luminescence, was applied to the linear aerospike nozzle. The effectiveness of the sidewall was evaluated and the sidewall shape was optimized lb apply PSP to micro-/nano-flow fields, Pressure Sensitive Molecular Film (PSMF) has developed based on Langmuir-Blodgett technique. Many luminescent molecules were assessed to clarify the pressure sensitivity. Using the PSMF, pressure distributions of a micro channel and a micro nozzle were obtained. They showed good agreement with numerical results by the DSMC method.PSP is considered to show oxygen number flux rather than partial pressure from its mechanism. Therefore, the relation between oxygen number flux and partial pressure was investigated from the kinetic theory and the DSMC numerical simulation. In high Knudsen number regime, the luminescent intensity of PSP was appeared to show the pressure resulting from the impulse of oxygen molecules to the surface instead of oxygen gas pressure.The molecular beam is often used as a probe for gas-surface interaction. Resonantly Enhanced MultiPhoton Ionization (REMPI) method was applied to measure the rotational energy distribution of nitrogen molecular beam. The REMPI spectrum was successfully obtained, and. the rotational temperature deviated from the translational temperature. It was also suggested that the rotational distribution showed non-Boltzmann feature.