Simultaneous Measurements of Velocity Vector and Temperature in Transonic Flow by Laser-Induced Fluorescence Method

在大型燃气轮机或汽轮机中，叶尖周围的流动变成跨音速流动，在叶片通道中产生激波。这些激波会引起附面层分离和叶片振动，从而降低效率。为了解释这些现象，采用激光诱导荧光(LIF)方法测量了大气压下跨音速流动的速度和温度。所获得的结果概括如下：1.建立了压降式跨声速风洞，并制作了矩形截面喷管来模拟跨声速叶栅内的流场。构建了基于Ar-离子激光的激光诱导荧光诊断系统。将棱镜插入到氩激光器的谐振腔中，实现了对激光器的宽带运转。在此条件下，从理论上证明了激光诱导荧光强度与流场温度成反比。通过使用这一点，三个-。测量了喷管内温度的空间分布。此外，通过在谐振腔中插入可调谐标准具，选择了Ar激光器的垂直模。该标准具被步进电机穿过，以获得荧光的光谱轮廓。根据荧光光谱峰值的多普勒频移计算出喷嘴内的速度。测量的温度和速度与静压测量结果吻合较好。现有研究证明，用激光诱导荧光方法可以高精度地测量大气压附近跨音速流场的温度和速度。

In the large-scale gas or steam turbine, the flow around the blade tip becomes transonic, and the shock waves are generated in the blade passage. These shock waves induce the boundary layer separation and the vibration of blades, which degrade the efficiency. To clarify these phenomena, the laser-induced fluorescence (LIF) method was applied for measuring the velocity and temperature of the transonic flow with atmospheric pressure. The obtained results were summarized as follows.1. The blow-down type transonic wind-tunnel was constructed, and the nozzle with rectangular cross-section was made to simulate the flow field in the transonic cascades. The LIF diagnostic system based on the argon-ion laser was also constructed.2. The prism was inserted into the resonance cavity of the argon laser to operate it with the broad-band mode. Under this condition, it was shown theoretically that the LIF intensity was inversely proportional to the temperature of the flow field. By using this, the three-. dimensional distribution of the temperature in the nozzle was measured. Also, by inserting a tunable etalon into the resonance cavity, the vertical mode of the argon laser was selected. This etalon was traversed by the stepping motor to obtain the spectral profile of the fluorescence. The velocity in the nozzle was calculated from the Doppler shift of the spectral peak of the fluorescence.3. The measured temperature and velocity were shown to agree very well with those obtained from the static pressure measurements.Present research proved that the temperature and velocity in the transonic flow-field near an atmospheric pressure could be measured with high accuracy by the LIF method.