【作者】 王超；

【导师】 刘铁根； 张学智；

【作者基本信息】 天津大学 ， 光学工程， 2020， 博士

【摘要】 光纤干涉微腔传感器具有体小量轻、性能稳定、本质防水、适应复杂恶劣环境等优点,将其与低相干干涉解调法相结合,适用于流体流速的测量。本文针对水利、航空、气象等领域对气流和水流的流速测量需求,开展了基于光纤干涉微腔传感的流速测量方法研究。研究了基于全相位滤波的信号预处理方法,实现了低相干干涉条纹的相位保留提取。提出了基于光纤干涉微腔传感的压差式流速测量方法,并通过气流实验进行了验证。提出了基于低相干干涉单条纹峰追踪和相移法的解调方法,实现了高精度的压力解调与流速测量。研究了流速测量方法的仪器化,并进行了初步的现场实验工作。本文的主要工作如下:1.在对膜片式干涉微腔传感器和低相干干涉解调系统进行理论分析的基础上,研究了基于全相位滤波的信号预处理方法。有效的消除了原始信号中的低频背景和高频噪声,得到了平滑的低相干干涉条纹,并保留了原始信号的相位信息,利于后续基于位置与相位信息的高精度解调计算。2.提出了基于压差原理和光纤干涉微腔传感的湍流流速测量方法。对湍流流场的压力分布进行了理论分析和仿真计算,在此基础上确定了传感器在流场中的最佳位置。设计并制作了由双闭腔式光纤干涉微腔传感器构成的流速测量探头,并通过高速气流实验进行了验证,实现了流速范围为7.9-81m/s的气流流速测量,测量精度为0.69%。3.提出了一种高精度与高适应性的空间域低相干干涉解调方法,适用于压力与温度均实时变化的湍流流场中的流速测量。该方法基于空间扫描型偏振低相干干涉解调系统,利用干涉条纹的质心实现了追踪单条纹的峰位置,并利用七步相移法将解调精度提高到亚像素级。压力实验结果表明,在常温下11-290k Pa的压力范围,解调精度为0.019%。在不同温度下,无需预先调节参数,该方法解调压力的精度保持稳定。流速实验的结果表明,该方法适用于湍流流场中的流速测量。4.研究了基于光纤干涉微腔传感器和低相干干涉解调的流速测量方法的仪器化与现场应用。完成了仪器的硬件和软件系统的设计与调试,实现了仪器计量溯源,并通过了环境适应性和可靠性测试。根据压差原理和光纤干涉微腔传感器的流速测量方法,设计并制作了水流流速传感阵列。在水利枢纽高坝比例模型进行了仪器的现场实验,实现了临底水流的流速测量。更多还原

【Abstract】 The fiber-optic interferometric microcavity sensor has the advantages of small size,light weight,stable performance,water-proof,adapting for the hard environment,etc.Combining with demodulation method of low-coherence interferometry(LCI),it can be employed for fluid flow velocity measurement.In this thesis,the measurement method of flow velocity based on optical fiber sensing with interferometric microcavity is studied for the airflow and water velocity measurement requirements of water conservancy,aviation,meteorology and other fields.A signal preprocessing method based on all-phase filtering is studied to extract the LCI fringe pattern,and the phase signal is retained after filtering.The flow velocity measurement method of differential pressure based on fiber-optic interferometric microcavity sensing is studied and verified by airflow experiments.The demodulation method based on tracing peak position of a single LCI fringe pattern and phase shifting interferometry is studied,therefore,the pressure demodulation and flow velocity measurement of high accuracy are realized.The instrumentation of the velocity measurement method is studied,and preliminary field experiments are carried out.The main work of this thesis includes:1.Based on the theoretical analysis of interferometric microcavity sensor of diaphragm-type and LCI demodulation system,a signal preprocessing method based on all-phase filtering is studied.The low-frequency background intensity and high-frequency noise of the original signal are effectively removed,and the smooth LCI fringe pattern is obtained.The phase information of the original signal is retained,which is conducive to the subsequent high-precision demodulation calculation based on the position and phase information.2.The measurement method of turbulent flow velocity based on principle of differential pressure and fiber-optic interferometric microcavity sensing is proposed.Based on the theoretical analysis and simulating calculation of the pressure distribution in the turbulent flow field,the optimal positions of the sensors in the flow field are determined.The sensor holder for measuring flow velocity composed of dual fiber-optic interferometric microcavity sensors with sealed cavity is designed and fabricated,which is verified by high-speed airflow experiments.The velocity measurement range is 7.9-81m/s,and the measurement accuracy is 0.69%.3.A demodulation method of spatial domain for LCI with high accuracy and adaptability is proposed,and the method is suitable for velocity measurement of turbulent flow field with real-time changes of pressure and temperature.Based on the spatial polarized LCI demodulation system,the proposed method employs the centroid position of the fringe pattern for tracing the peak position of a single fringe,and the seven-step phase shifting interferometry is employed to improve the accuracy to sub-pixel level.At room temperature,it is proved that the demodulation accuracy is0.019% in the pressure range of 11-290 k Pa.Moreover,no parameter needs to be adjusted in advance,and the pressure demodulation accuracy is stable at different temperatures.The experimental results of airflow velocity indicate that the proposed method is suitable for the flow velocity measurement in the turbulent flow field.4.The instrumentation and field application of the flow velocity measurement method based on fiber-optic interferometric microcavity sensor and LCI demodulation are studied.The design and debugging of the hardware and software systems of the instrument are completed,the metrological traceability of the instrument is realized,and the environmental adaptability and reliability tests are passed.According to the flow velocity measurement method of differential pressure and fiber-optic interferometric microcavity sensor,the flow velocity sensor array is designed and fabricated.In the high dam scale model of hydro-junction,the field experiments of the instrument are carried out,and the velocity measurement of the underflow is realized.更多还原