| The air tightness of pressure vessels is one of the important indicators of product quality and safety performance,so the leak detection of pressure vessels is of great significance in industrial safety production.The traditional detection techniques for pressure vessels,such as pressure change leak detection and bubble leak detection,are inefficient and low in accuracy,which cannot meet the requirements of modern industrial production for pressure vessel leakage measurement.Therefore,this paper proposes a leakage ultrasonic detection technology,whose principle is to use the acoustic signal generated during leakage to reflect the leakage of the container.This technology has the advantages of high sensitivity,fast response speed,wide measurement range and so on.On the basis of the previous research,this paper summarizes three key technologies of ultrasonic leakage detection: one is the design of tapered sound concentrator,which is used to amplify the weak ultrasonic leakage signal;The second is the leakage ultrasonic signal processing circuit to complete the pre-processing of the leakage signal;The third is the design of the identification algorithm of the leak aperture to complete the characterization of the leak aperture.Based on the above key technologies,based on the aero-acoustics theory and combined with the leakage mechanism of pressure vessels,a small leakage model of pressure vessels was established in this paper.The finite element simulation software was used to conduct numerical simulation of the acoustic field during the leakage process of pressure vessels,and the distribution of the leakage turbulent flow rate and pressure field was obtained.Secondly,according to the characteristics of weak leakage ultrasonic signal,a tapered sound concentrator is designed according to Webster’s theory to amplify the weak signal.At the same time,considering the influence of materials on amplifying the leakage signal,the finite element method is used to simulate the sound loss of four kinds of materials,and the selection of the optimal material is solved.In addition,for the acquisition and processing of ultrasonic leakage signal,the hardware circuit and software module of ultrasonic leakage detection system are built in this paper.The hardware circuit includes impedance matching circuit,infinite gain bandpass filter,adjustable gain amplifier circuit and leakage ultrasonic data acquisition circuit.The leakage detection software system takes LabVIEW as the development platform,which can realize the real-time display,data storage,signal processing and other functions of leakage ultrasonic signal.Finally,the system focuses on the precise measurement of the leak aperture,and puts forward the eigenvalue based Euclidean distance algorithm to identify the aperture,which completes the characterization of the leak aperture of the pressure vessel.Through the experimental measurement,the leakage ultrasonic detection system designed in this paper realizes the three key technologies proposed in the paper.The system can realize the real-time display of the pressure vessel leakage ultrasonic signal.Under the vessel pressure of 40 k Pa,it can complete the accurate measurement of 0.3mm～1.0mm,and can be 4500 mm away from the leakage source.A leak signal with a 0.7mm aperture was detected. |
