Research On Leak Detection In Sealed Cabin Based On Acoustic Emission Technology

There are a lot of space debris which are mostly concentrated in low-Earth orbit and geosynchronous orbit.The bumber of M/OD over 1mm are more than 35 million and the average running speed of space debris is about 10km/s with a growth rate of 5% per year.With the development of our country's aerospace technology,the numbers of spacecraft launches continue to increase.In general,A space debris collision on the centimeter scale will be enough to geodesically destroy a spacecraft.It can only be avoided by orbital maneuvering and millimeter-scale space debris requires design of protective structures.Millimeter-diameter holes are more common for spacecraft after they collide with space debris.Because of that the gas leakage caused by the collision will lead to the constant drop of pressure inside the cabin,so when a spacecraft in space collides with space debris and then produces small leakage,it should quickly and accurately locate the source of leakage to ensure the safety of the spacecraft and astronauts.Therefore,according to the rapid and accurate positioning requirement,this paper studies the leakage detection technology of the sealed cabin.When space debris collides with the crew capsule,due to the pressure difference between the inside and outside of the sealed cabin,the gas jet is triggered,and the interaction between the gas and the spacecraft bulkhead generates elastic waves,which propagate on the bulkhead.And then the elastic wave signal is detected by a sensor coupled to the bulkhead,and the location of the leak hole is determined by analyzing the signal.So in this paper,the chaos theory is used to identify small signals with different apertures in the background of noise,and DOA estimation and location algorithm is used to introduce wavelet spectrum analysis to locate the gas leakage source,and numerical simulation is used for analysis and research.Firstly,a gas leakage experiment is carried out on the experimental platform to collect leakage AE signals and analyze their signal characteristics,and then the mechanism of leakage AE signal and its propagation characteristics are studied and analyzed.In addition to the above analysis,fluent module,transient dynamics module and fluid-solid coupling module in ANSYS Workbench are used to analyze the relationship between leakage velocity,stress intensity and pore size at different leakage holes.And then the leakage signal generated by simulation is sampled and analyzed.Secondly,by analyzing the characteristics of acoustic emission signals generated by continuous gas leakage in the sealed cabin,and on the basis of studying chaos theory,weak signal detection is carried out by using Duffing vibrator's immunity to noise and sensitivity to parameters.The aim is to identify the weak signals generated by different apertures in the background of noise and verify the validity of chaos theory for the detection of small signals.Finally,the collected AE signals are located by DOA estimation and location algorithm.By selecting the topological structures of different sensor arrays,this paper focuses on optimizing the array spacing and the number of array elements of L-type array to improve the array orientation accuracy.Then the positioning accuracy can be improved by multi-array positioning.The positioning error of sensor array is analyzed,and two kinds of global array models are proposed to reduce the positioning error.By comparing the location precision and location area,the two models are compared and their respective characteristics are analyzed.In a word,this paper improves the accuracy of locating the leakage source by studying the mechanism of the leakage signal generation and propagation,the identification of the leakage signal and the global localization.This research is of great engineering value to the leak location of the sealed cabin.