Research On Ultrasonic Testing Principle And Application Of Low Concentration Of Impurities In The Fluid

It is urgent to develop technologies without secondary pollution to protect the human living environment. With the special application, this dissertation develops several key techniques to solve pollution problems, such as online acoustic detection monitoring for the leakage of harmful gas SF6, ultrasonic electronics equipments for sewage treatment, transformer water-in-oil detection with acoustic and electronic methods. The contributions of the dissertation are summarized as follows:The ultrasonic testing principle for the low concentration of impurities in the fluid is researched in both experimental and theoretical fields. We simplify the related conditions in conventional methods reasonably. The novel theoretical formulas are concluded for the practical engineering application. With the experiments, it demonstrates that our formulas are more suitable in the ultrasonic detection for the low concentration of different material contents, such as SF6 content in the air, cavitation bubble content in the water, water content in the transformer oil.The dissertation also develops several ultrasonic equipments of sewage treatment in three aspects. The scheme of the ultrasonic power circuit for water treatment based on actual water test is proposed. It shows that the conversion of electrical power to acoustic power is effectively improved compared with the conventional method. Meanwhile, the enhanced match equipment between the ultrasonic power and ultrasonic reactor for water treatment is realized by using advanced communication circuit. This equipment can obtain adaptive conjugate match impedance transformation in wide frequency range, which only comprises transmission line transformers, smart chips and variable inductors. It shows that this equipment can obviously promote electric power which ultrasonic power supply circuit output to ultrasonic reactor for water treatment. At last, the ultrasonic detection method of cavitation bubble content and the narrow pulse measure method of high strength sound intensity are presented respectively. These methods provide a novel tool to measure acoustic related parameters and enhance the reliability of the experiment results.In the research of the online monitoring of SF6 leakage, ultrasonic centralized detection method is proposed to deal with the problem of cumbersome installation. We also improve the detecting precision and reduce the misinformation condition possibility by the difference and compensation method. Finally, this dissertation focuses on the water content test in transformer oil. The framework is established for the ultrasonic detection of water content in transformer oils. Some research workes is also done in the phacoemulsification and signal acquisition sections.The main research in this dissertation has achieved the prize in the third rank by Chinese Institute of Electronics and Information Science Technology in 2009. Some achievements are now in the process of the actual application.