针对水利枢纽高速气流的流速测量需求,提出了一种基于光纤法布里-珀罗(F-P)传感技术的湍流流速测量系统。该系统由风速测量探头和偏振低相干干涉解调单元组成,利用两支F-P传感器检测流场的压力和温度变化,以实现流速的计算。通过追踪单个条纹的峰位置和七步相移法,对低成本线阵CCD采集到的干涉信号进行高精度解调。在温度为20~40 ℃和压力为98~110 kPa的环境下对两支传感器进行标定,用于滞止压力测量的传感器的压力绝对误差小于0.018 kPa,用于流场温度测量的传感器的温度绝对误差小于0.08 ℃。利用该系统进行了速度为9.3~93 m/s的气流检测,流速绝对误差小于0.49 m/s。实验结果表明,该系统可以实现高速湍流的流速测量,成本低,有广泛的应用前景。

In this study, we propose a turbulent flow-velocity measurement system based on the optical fiber Fabry-Perot (F-P) sensing technology, which can be used to monitor the high-speed airflow velocity at hydrojunctions. The proposed system comprises an airflow sensor holder and a polarized low-coherence interferometry demodulation section. The flow-velocity is calculated using two F-P sensors, which can be used to measure the pressure and temperature variation of the airflow field. Further, the interference signal obtained using a low-cost linear CCD can be accurately demodulated by tracing the peak position of a single fringe pattern and using the seven-step phase shifting method. The two F-P sensors are calibrated in the temperature range of 20-40 ℃ and the pressure range of 98-110 kPa. The pressure absolute error of the sensor used to measure the stagnation pressure is less than 0.018 kPa, while that with respect to the temperature of the sensor used to measure the airflow field temperature is less than 0.08 ℃. The proposed system is used to measure the airflow velocities ranging from 9.3 to 93 m/s, and the absolute error of the flow-velocity is less than 0.49 m/s. The experimental results indicate that the proposed system can be employed to measure the flow-velocity of high-speed turbulence with a low cost and possesses a wide application prospect.