Study On The Leak Detection Of Space Environment Simulator Using Acoustic Emission Technology

With the development of manned space technology and activities, the Spacecraftplays as an important role in space activities to maintain the success of explorationactivities in space. Space Environment Simulator, the Spacecraft’s "cradle", cansimulate the unique characteristics of space like extreme-low temperature and highvacuum, is one of the key facilities to provide Spacecraft space environment testbefore their launch. Space Environment Simulator leak detection technology is theguarantee of the spacecraft environmental testing, the tightness of the simulator isdirectly related to the testing effect of the spacecraft.The existing leak detection methods of Space Environment Simulator in ourcountry are mainly vacuum bubbles based and helium leak detection based. They arelow efficient and detection range limited and could be hardly to meet the needs ofrapid leak detection and localization in case of crisis situations. With the targetedresearch advances in space science, especially in the rapid development of spacecraftenvironmental testing of spacecraft, the leak detection technology of spaceenvironment simulator has become an important topic to be studied and proposedsolutions right now.In this paper, the major needs of the country’s manned aerospace environmentaltesting of space technology is considered and a new method based on acousticemission is studied to address the leak detection problem of the Space EnvironmentSimulator. The generation mechanism of acoustic emission signals in the paper isillustrated combined with the gas power leak. Research ideas are presented based onacoustic emission gas leak detection technology, and attention of the research processare paid to key technologies such as the identification of small leaks, the location ofcontinuous leak source and the topology of acoustic emission sensor array. Finally, incollaboration with Beijing Institute of Spacecraft Environment Engineering, a numberof field experiments were carried out and useful research results were confirmedbased on the principle of acoustic emission leak detection. The main research workare as follows:(1) The mechanism of acoustic emission signals of gas leakage is studied, andthe leakage model of the Space Environment Simulator is established. The flow fieldand sound field numerical simulation of simulator leaks were discussed using finite element method. The correspondence between the leakage hole parameters andacoustic emission signals characteristics were studied such as the flow rate, thepressure. Also, the relationship between diameter and shape of the hole and soundfield were studied.(2) The acoustic emission signals inspired by different diameter holes wereinvestigated. Acoustic emission signals produced owing to continuous leakage are theobjects of the research. A variety of characteristics are selected for the signal analysiscovering the spectral analysis method, wavelet packet decomposition and parameterfeature analysis theory. The intrinsic link between simulator gas leak conditions andacoustic emission signal characteristics were studied and the amplitude spectrum andwavelet packet normalized energy distribution characteristics were analyzed producedby different pore sizes gas leaks.(3) The acoustic properties of the background noise signals and the leakagesignals of space environment simulator were analyzed. The tiny leak detectiontechnique based on chaos theory is studied, and a coupled Duffing chaotic oscillatorbased on a theoretical model ring chaos theory is completed. Combined with theon-site data analysis, the signal to noise ratio of the detection of small leaks wereimproved, the effectiveness of the tiny leak detection technology based on the chaostheory was verified.(4) The limitations of the location of continuous gas leak sources by traditionallocalization algorithms are illustrated combined with the characteristics of the gasleaks of the space environment simulator.The implementation mechanisms anddefects of traditional acoustic emission source localization algorithm were alsodescribed. This paper presents a method based on beamforming algorithm, andcombines the array signal processing theory with sensor array steering vector study.Also, the analyses of the different sensor topology distribution were calculated. Thebest sensor array topology model structure is obtained through the analysis of on-siteexperimental data of gas leak detection. The validity of the algorithm based onacoustic emission for continuous leakage location is confirmed.