两相流超声编码激励测试方法研究

发布时间：2018-01-28 18:28

本文关键词： 气液两相流参数检测超声波编码激励脉冲压缩测试系统　出处：《天津大学》2014年硕士论文　论文类型：学位论文

【摘要】：超声检测技术广泛应用与医学、流体等的测量中,因超声波在流体中传播,不会破坏流体的流场与造成压力损失,故超声检测技术拥有独特的优势。同时超声传感元件可以安装在管道外壁,也就能够避免与流体相互接触。本文主要针对应用于气液两相流测量的超声检测技术的问题进行研究。在两相流检测中,超声方法的应用仍存在一些问题。主要原因在于,超声波传播过程中,声波路径十分复杂,会产生多次反射造成波形的叠加,使超声波信号频率混杂、测量结果信噪比较低。课题包括以下几方面工作:(1)为满足两相流过程参数的在线检测,通过研究编码信号以及脉冲压缩特性。采用线性调频信号编码激励的方式,结合气液两相介质分布及流动特性实际,分析线性调频信号时宽、带宽对脉冲压缩效果的影响,选择适用于两相流超声测试技术的编码信号形式。(2)设计了基于FPGA的线性调频编码激励和脉冲压缩信号技术结合的两相流超声测试系统,实现编码信号的发生、激励、高速数据采集、数字脉冲压缩算法,以及基于PCI总线的通讯等功能,为进一步研究超声编码测试技术提供硬件平台。(3)搭建实验测试平台,根据两相流测试中的超声衰减法基本原理对气液两相流中气泡的参数进行提取和修正。相关的实验结果表明,使用编码激励信号可以有效测量气液两相流中气泡的参数,并可以在不损失分辨率的基础上提高系统的信噪比。验证了编码激励与脉冲压缩技术应用于气液两相流超声检测中的可行性。
[Abstract]:Ultrasonic testing technology is widely used in medicine and fluid measurement, because ultrasonic wave propagates in the fluid, it will not destroy the fluid flow field and cause pressure loss. Therefore, ultrasonic detection technology has a unique advantage, and ultrasonic sensing elements can be installed in the outer wall of the pipe. In this paper, the ultrasonic detection technology used in gas-liquid two-phase flow measurement is studied. There are still some problems in the application of ultrasonic method. The main reason is that in the process of ultrasonic wave propagation, the sound wave path is very complex, which will produce multiple reflections and cause the superposition of the waveform, which makes the frequency of ultrasonic signal mixed. The SNR of the measured results is low. The research includes the following work: 1) On-line detection to satisfy the parameters of two-phase flow process. By studying the characteristics of coded signal and pulse compression, the time-width of LFM signal is analyzed by using the encoding excitation mode of linear frequency modulation signal, combining with the distribution of gas-liquid two-phase medium and the actual flow characteristics. The effect of bandwidth on pulse compression. A two-phase flow ultrasonic testing system based on FPGA is designed, which combines the linear frequency modulation (LFM) coding excitation and pulse compression signal technology. The functions of coding signal generation, excitation, high-speed data acquisition, digital pulse compression algorithm, and communication based on PCI bus are realized. For the further study of ultrasonic coding testing technology provides a hardware platform. According to the basic principle of ultrasonic attenuation method in two-phase flow measurement, the bubble parameters in gas-liquid two-phase flow are extracted and corrected. The parameters of bubbles in gas-liquid two-phase flow can be effectively measured by using the coded excitation signal. The signal-to-noise ratio of the system can be improved without loss of resolution, and the feasibility of applying the coded excitation and pulse compression techniques to the ultrasonic detection of gas-liquid two-phase flow is verified.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：O359;TB553

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