Research on Temperature/Velocity Measurement Technique Utilizing Laser-Doppler Velocimetory with Fluorescent Seed Particles

为了从微观角度研究非均质换热介质(如气固两相流)中的换热机理，迫切需要发展局部同时测量介质温度和速度的技术。在本研究项目中，提出了一种基于激光多普勒测速(LDV)的荧光种子颗粒温度/速度测量技术的概念，并对其可行性进行了实验验证。为了验证该技术的可行性，利用Ar~+离子激光器(可见光)或He-Cd气体激光器(紫外光)构建了LDV的光学装置，分散在传热介质中的荧光种子颗粒使我们能够测量荧光光，由此估算介质的温度，以及用于速度测量的散射光。1.在同一种子颗粒的温度和速度的同时测量中，利用单色仪可以有效地分离荧光光和散射光。通过单色仪测量荧光光将提高温度测量的准确性，因为荧光的寿命取决于荧光灯的波长。为荧光灯和/或CRT显示器开发的荧光颗粒适合作为种子颗粒，因为该颗粒在可见光波长范围内发射相对较强的荧光。然而，激发后这些粒子的荧光衰减比上升慢得多，因此这些粒子的荧光寿命与温度的关系不是作为相移而是作为对多普勒猝发信号的平滑效应的变化来观察的。

In order to examine the mechanism of heat transfer in heterogeneous heat transfer media, e.g.gas-solid two-phase flow, from microscopic view point, it is keenly required to develop the technique for simultaneous measurement of temperature and velocity of the media in local basis. In this research project, the concept of a temperature/velocity measurement technique utilizing Laser-Doppler Velocimetory (LDV) with fluorescent seed particles was proposed, and its feasibility was experimentally examined. To examine the feasibility of the technique, an optical setup of LDV was constructed by using an Ar^+ ion laser (visible light) or a He-Cd gas laser (UV light), and the fluorescent seed particles dispersed in the heat transfer medium enable us to measure the fluorescent light, from which the temperature of medium was evaluated, as well as the scattered light for the velocity measurement. Obtained results can be summarized as follows :1. In the simultaneous measurement for the temperature and velocity of the same seed particle, fluorescent light and scattered light can be effectively separated by using a monochromator. The measurement of fluorescent light through the monochromator would improve the accuracy of temperature measurement, since the lifetime of fluorescence depends upon the wavelength of the fluorescent light.2. The fluorescent particles developed for the fluorescent lamps and/or CRT display are suitable as the seed particles, since the particles emit relatively strong fluorescent light in visible wavelength range. However the decay of fluorescence of these particles after the excitation is quite slower than the rising, and thus the temperature dependence of fluorescent lifetime of these particles can be observed not as the phase shift but as the change of smoothing effect on the Doppler burst signal.