Ultrasonic Liquid Level Detection Frequency Of The Selected Theoretical Calculations And Experimental Studies

Non-invasive ultrasonic liquid level testing is an important ultrasonic technology. It has a wide range of applications in the petroleum industry and the chemical production, especially in the storage and transportation process. It is very important for the production process control and security. The liquid-Level such as the flammable, volatile, toxic and corrosive liquid can be highly accurately measured. For the airtight containers and the large pressure vessels, in order to avoid the occurrence of major accidents, the non-invasive ultrasonic liquid level testing is very important.Since the majority of flammable and toxic liquid also have a strong corrosive, it is necessary to add anti-corrosion material lining in the tank wall. And the pressure vessels wall also have a certain thickness, which is usually from the tens of millimeters to a few millimeters, such as the solid rocket motor fuel tanks, all kinds of acid, alkali and salt liquid storage tank. In the non-intervention ultrasonic liquid level detection, the reflection and transmission of acoustic wave happen in the tank wall at the each interface of the multilayered medium. Because of the complexity of the storage tank structure and the multilayered medium, the reflection and transmission of acoustic wave will be very complex. Finally the acoustic energy, which can reach the internal liquid, is very small. The echo signal contain useful information and various noise signal, and sometimes the useful information is polluted by the noise signal, especially be drowned. All of these things will affect the signal recognition and processing, and also increase the difficulty of study.The propagation of acoustic wave in the multilayer medium, due to the reflection and transmission at many different sectors surfaces, the internal acoustic attenuation energy is larger. Studies have shown that, through the periodic multi-media system, the sound waves show the pass frequency band and the band gap characteristics, that some of the acoustic waves can be fully adopted, and some are much more difficult to get through these periodic multilayered medium.The non-intervention ultrasonic liquid level detection, for the high-pressure reaction vessels and the tank containing strong corrosive, dangerous or volatile liquid, is studied in this paper. According to the transfer matrix method, the transmission expression of acoustic wave's energy across multilayered medium in the non-intrusive ultrasonic liquid level testing is investigated. It is found that the acoustic echo energy have an important relationship with the acoustic frequency, the characteristic impedance of the material and the thickness of the middle layer media. The function relationship between the acoustic echo energy and the sound frequency is studied, and the best acoustic frequency for the incidence is calculated in one storage structure. The result, which is validated by an experiment, shows that the reflex echo intensity is obviously influenced by both the frequency and the interlayer media. In order to obtaining the obvious reflection echo signal, the incidence frequency selection is indispensable. Ultrasonic testing system (including the transmitter and amplifier, transceiver transducers, signal analysis and processing module, etc.) is designed. For the different structure and thickness of the liquid storage tank, the selection of appropriate acoustic emission frequencies is essential to achieve better ultrasonic testing results. Experimental results are agreeing with the theoretical calculations. It provides an effective way in the frequency selection of non-intervention ultrasonic liquid level detection.