【作者】 怀保玲；

【导师】 何存富；

【作者基本信息】 北京工业大学 ， 测试计量技术及仪器， 2007， 硕士

【摘要】 罐体液位检测广泛应用于石油、化工等领域，对液位检测新方法、新原理的研究是近年来该领域的一个研究热点。根据兰姆波中某些模态的特定参数(如衰减因子)对液体存在敏感的特性，提出一种基于兰姆波的罐体液位检测方法，搭建试验系统，并对影响罐体液位检测试验结果的各种主要因素进行试验研究。主要工作内容如下：(1)基于超声导波理论，对能量速度的求解公式进行推导，并指出能量速度和群速度的区别和联系；对单面液体负载薄板中的兰姆波的特征方程进行求解；并对漏兰姆波和兰姆波、周向导波和兰姆波、纵向导波和兰姆波之间的关系进行理论分析和试验验证。(2)对厚度不同板中的兰姆波的各模态的传播特性(主要是衰减因子对液体存在的敏感特性)进行了研究，并对影响液位检测试验结果的主要因素(包括激励信号的周期数，激励信号所加的窗函数，模态的频散特性和衰减因子，传感器的工作频率和入射角度等)进行了试验研究。(3)研制了工作频率为2.5MHz、入射角为50°的超声纵波斜探头和其夹具，实现对壁厚3mm，直径600mm罐体的液位定点和连续检测，并给出液位高度与接收信号幅值之间的拟合曲线。(4)利用Labview语言编写罐体液位检测软件，实现了罐体液位的定点检测以及实时报警。更多还原

【Abstract】 Liquid level detection of tanks is widely used in petroleum, chemical and otherfields. Research on new methods and new principles about liquid level detectionhave become hot interests in these fields. A new method detecting the liquid levelwas presented and implemented, based on the sensitivity of the characteristicparameters, such as, attenuation factor, of some Lamb wave modes to the presenceof liquid. Besides, different kinds of factors influencing the liquid level detectionresults were analysed and verified experimentally. The main contents are as follows:(1) Based on ultrasonic guided wave theory, the energy velocity formula wasderived; The relationship between group velocity and energy velocity was alsoanalysed; The characteristic equations of Lamb waves in solid plate with liquid loadon single side was derived; the relationship among Lamb waves and leak Lambwaves, circumferential guided waves and Lamb waves, longitudinal guided wavesand Lamb waves were also analysed theoretically and verified experimentally.(2) Propagation characteristics of different modes in different-thickness plateswere analysed. Besides, different kinds of factors (cycle number of excitation signal,window function, mode dispersion and attenuation factor, working frequency andincidence angle of transducer, etc.) influencing the liquid level detection results wereanalysed experimentally.(3) The transducer with working frequency 2.5MHz, incident angle 50°andtransducer clamp were developed to implement fixed liquid level detection andliquid level measurement of the tank with 600mm-outer-diameter and3mm-thickness-wall, the fitting curve between liquid level and received signalamplitude was obtained.(4) Programmed real-time liquid level detection software using LabVIEW toimplement fixed liquid level detection and real-time alarm.更多还原