Research On The Method Of Liquid Level Detection Of Tanks Based On Lamb Waves

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.