摘要:
以激光Doppler效应为原理,结合可调谐半导体激光吸收光谱技术的窄线宽、可调谐优势,可实现高速气流流速的实时在线检测.介绍了流速测量的基本原理和方法,搭建了双光路流速测量系统,利用DFB激光器位于1398 nm处的水汽吸收线进行10 kHz快速扫描,获得高速气流的实时光谱信息,并根据两路吸光度曲线之间的Doppler频移来反演气流流速.介绍了频率标定和Doppler频移测量的方法.在风洞上进行了流速测量验证实验,将流速测量结果与理论计算结果进行了对比,二者之间符合得较好,初步证明了该方法的可行性.分析了系统的性能及可能引起流速测量误差的因素,以便系统进一步优化
Abstract:
Based on the laser Doppler effect,real-time and on-line measurements of velocity in high-speed flows can be realized using tunable diode laser absorption spectra（TDLAS）.The fundamental theory and the method to measure the velocity are presented.A dual-beam system used in the experiments is described.The water vapor absorption feature at 1398 nra is utilized to detect the flows generated within a wind tunnel.The DFB laser is quickly tuned at a rate of 10 kHz to obtain the spectra of the transient flows by using scanned-wavelength direct absorption spectroscopy.The ways to calibrate the frequency and calculate the Doppler shift（DS） are also introduced.The measured velocity is compared with the calculated velocity,and they are in good agreement with each other,which proves that the way combining DS with TDLAS to measure the velocity in high-speed flows is reasonable.The system capability and possible factors to induce measurement deviations are analyzed to improve the system performance in the future.
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