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1 11th European Conferene on Non-Destrutive Testing (ECNDT 14), Otober 6-1, 14, Prague, Czeh Republi Design of portable leak detetor used for manned spaeraft based on More Info at Open Aess Database ultrasoni Yan Rongxin, Sun Wei, Li Weidan Beijing Institute of Spaeraft Environment Engineering Beijing, Mail box: Abstrat: To solve the possibly leak in manned spaeraft, it is neessary to quikly and expediently loate the leak. This paper is written about the researh on the ultrasoni produing, ultrasoni transmitting and ultrasoni detetion through mathematial analysis. The mathematial model of leak diameter, deteting distane and deteting orientation is built, the experimentation of different leak rate, deteting distane and deteting has been done to validate the mathematial analysis result. The priniple prototype of the detetor has been designed and developed, the deteting leak rate ould be 1-1 Pa.m 3 /s, the loating preision is better than mm, the quality of detetor is 1.kg and the power dissipation of the detetor is less than.w. Keywords: leak detetion leak detetor ultrasoni manned spaeraft 1 Introdution To ensure the spaeraft funtion and safety of astronauts, the abin should have good leak tightness. Before emission, leak testing ould hek the tightness. But if the spaeraft is on orbit and fly for long time, omplex environment suh as spae debris and meteoroid ould make the abin start distortion, hurt, perforation and even leak. The sealed abin is installed with abin window, eletri linker and pipeline, whih ontat the abin by airproof way. As the ontat material has been working for deades, it ould be aging, stress relief, whih lead to the deline of airproof tightness, and the rigor spae environment aelerates the aging of airproof whih ould indue the leak. In addition, the abin joint door, joint point, and transition abin need to work many times, whih need reliable airproof tightness to avoid the leak malfuntion. After designing the protetion institution of spaeraft and finishing the leak

2 detetion on ground to avoid the leak, at the same time, we should study the leak detetion tehnology to hek the leak quikly, and then repair the leak to insure the spaeraft work well and the astronaut live safety. Manned spaeraft need to test the sealing performane in orbit, whih inludes: the total leakage rate detetion by pressure hange tehnology [1],, EVA vauum sensor or diretional vauum gauge tehnology [],, abin aousti sensor array tehnology [3],. But the total leakage rate detetion tehnology an only determine the overall rate of sealed abin leak, the leak loation an t be determined, and an t be used alone to loate the leak. The other two method need very omplex equipment, espeially diretional vauum gauge tehnology requires astronauts get out of the abin whih will inrease risk. Therefore, the development of a detetor an be used in abin is very neessary, so we arry the leak detetion by ultrasoni method tehnology and equipment researh. A lot of ountries began early develop and use ultrasoni leak detetor. Many institution developed ultrasoni leak detetion equipment, and some detetors have been applied to the International Spae Station. A ollaboration by NASA and a ompany developed an ultrasoni leak detetor whih is shorten as ULD [4], the United States Kennedy Spae Center has developed a set of ultrasoni leak detetion equipment Ultraprobe9 [5], Frane LEAKSHOOTER latest produed a LKS1 leak detetor [6], Belgium SDT ompany produed a portable ultrasoni leak detetor SDT7 [7], the United States Infion has developed a whisper handheld ultrasound leak detetor[ 8], University of Iowa NDT Centre has done aousti sensor array tehnology researh [9]~[1] In China, Shanghai Jiaotong University [13]~[15], Beijing University of Aeronautis and Aerospae [16], Tsinghua University [17], Xi'an Institute of Tehnology [18] and other institution also utilize aousti theory to do researh, but study little about the spaeraft leak detetion tehnology in orbit. Beijing Institute of Environmental Engineering based on the long and rih experiene in spaeraft leak detetion, do researh work on portable ultrasound leak detetor for spaeraft in orbit [19]~[3].

3 Theory analysis.1 The signal prodution from leak When the abin leak, the air path along the leak from abin to the vauum under gas pressure differene. While passing through the tiny aperture, in the ase of turbulent, the flow veloity is very high and a number of vortex form turbulent. The interation of vortex makes the volume elements push eah other by the equal and opposite fore, ausing the prodution of quadrupole jet. In the early 195s, Lighthill built a mathematial model of jet noise by similarity theory, in the model, left side of the equation has the same expression with lassial aousti wave equation, whih uses the Alembert operator as aousti parameter, and all the items aused by hydrodynami flutuations are moved to the right side as sound soure item. As these sound soure items, people ould aquire by experiment or DNS, LES and even turbulene model. Lighthill expression an be shown as [4] : In the expression: T ij ( t u u i j ) T ij ij ij[( P P ) ( )] (1) is the Lighthill turbulent stress tensor, the first item is the Reynolds stress aused by speed, the seond item is fluid visous stress aused by fluid visousness, the third item is influened by thermal ondutivity. Lighthill equation shows that the quadrupole is the fore by hydrodynami stress, whih indiates that when aousti wave influene little on fluid, we an solve the Lighthill equation by lassial aousti theory and aquire aousti solution. Beause the inhomogeneous term in the right side is a known quantity or alulated quantity, so the solution an be aquired as: p( x, t) R x x i j Tij ( y, t x y / ) dy x y () The solution may also be referred to as the jet noise predition formula, whih shows the sound pressure aused by the jet noise p(x,t) is the summation of quadrupole sound soure T ij (y,τ) whih is transmitted τ and arrived at the same time t.

4 Aording to Lighthill aousti analysis, we an get the sound power PT with the diameter d and the thikness l [4] : 8 Vd l s P l 5 3 T aousti propagation veloity in the abin atmosphere atmospheri density in abin s standard atmospheri density V gas jet veloity at the nozzle As an be seen from (3), when the leak diameter is fixed, the injet power have diret proportion to the power of 8 jet veloity. When the jet veloity and the length of leak is fixed, the bigger the diameter is, the power of jet is bigger. For a losed manned spae abin, its inside abin pressure will hange due to leaks, so we an aquire the pressure equation by leak rate and abin pressure p t t P Poute t Pout V (4) P C V abin volume 3 d C l 4 d leak diameter l leak length P The initial abin pressure P out EVA vauum pressure Usually manned abin volume is 1~1m 3, the probably leak diameter appear between.1~1mm, the ondutane is small. The formula (4) tell us: to the.1mm leak, 1m 3 abin, the pressure deline 1 kpa beause of air leak need 1.5 h. So in the dimension of min time of leak testing, the pressure hange little, the outlet pressure is in vauum, so p p out t is very small, the flow veloity is [5] :

5 V pt p [1 ( 1 p 1 out t ) ] 5 In the formula, C p C V C p, is abin gas thermal apaity at onstant pressure, CV is thermal apaity at onstant volume in abin, Gas density abin Substituting (5) into (3), we have: pt pout [1 ( ) 1 pt P T l ] d 8 s 6 For the leak in large abin, in the min dimension, p t p p t out l hange little, so the injet power have diret proportion to the power of 8 leak diameter. So if the sound power ould be measured, the leak diameter ould be ensured.. Sound propagation hole drain signal The sound signal produed in leak should transmit to the sound sensor so that it ould be tested. Suppose the jet sound power P T as point soure. In that way, the point soure ould be assumed as a monopole soure, shown in Figure 1, whih is the aousti wave equation: ( rp) ( rp) (7) t r In the formula r position of the reeiving point P the sound pressure at the reeiving point the sound pressure at the reeiving point p(r,t) r a origin Fig.1 Pulsating sound field propagation due to point soures

6 Its sound field solution is p ( r, t ) p e A i( wtkr ) (8) In the formula, p A A r is the sound pressure, when transmit to the reeiving point the sound strength is: 1 r Ir P T If the angle between the reeiving surfae and normal of leak is, the reeiving sound strength is: I 1 pt pout [1 ( ) os 1 pt P os rs T 5 7 r r l ] d s (9) (1) Equation (1) shows that: if the manned abin ours a leak whose diameter is d and thikness is l,in partiular measure distane r and diretion, by the sound pressure measurement, we an determine the leak size..3 The enter frequeny of the ultrasoni signal The leak aousti spetrum is omplex, the sensor annot over all wave band in measurement. To measure aousti wave effetively and avoid noise disturbane, we should find the sound pressure frequeny. Aording to the researh, the ultrasoni sound power spetrum is a funtion of Strouhal number fd/v, f is the ultrasoni frequeny, d is the leak diameter, V is the outlet veloity. A lot of experiments shows that [6], the normalized Strouhal number the ordinate is the power level S 1 dw V 1log( W df d fd C V is shown as fig., and the urve is experiene urve. 1, / is the orret oeffiient, C ) db. The normalized power spetrum db ) dwv 1 log( W dfd fd V Fig. the normalized power spetra of leak noise

7 The urve in Figure an approximate the urve equation: In the formula 1 dw V y W df d 4 1 y 1 ( x ) x 5 fd C x. V C (11) In order to improve the detetion sensitivity, and the peak power at the enter frequeny has maximum sensitivity, so take the formula (11) derivative as, we have: y (1 ) 1 3 ( x ) x x (1) When x 1, y ould get the maximum value, so the sound power get peak value when 5 fd C 1, the flow veloity in the leak is about 3m/s. And if we C V ignore the temperature orretion /, the relevant frequeny is enter frequeny, whih is shown in table.1. Table 1 No fix eah leak leak under ideal onditions ultrasound data sheet Leak (mm) diameter Center frequeny khz) As shown in Table 1, the frequeny orresponding max sound power is all bigger than khz,whih means that all the signal is ultrasoni. The noise sound in the abin an be avoided by detetor, whih an only hek out ultrasoni signal. 3 Experimental verifiation Design an ultrasoni leak detetion system as fig.3, try to verify the relationship between jet sound power and leak loation, detetor and reeiving diretion. Using the subsistent environment simulation system, we build a test system of ultrasoni. As the leak is the sound soure, the dimension based on the sound soure as origin is shown in fig.3, and the assistant oordinate system is shown in fig.4. Set the ultrasoni sensor and amplifier iruit as reeiver in the 3-dimension equipment. The fig.5 is the ultrasoni leak detetion test verifiation devie

8 shemati. z y The vauum simulation system Aousti soure x Fig.3 Ultrasoni leak detetion system tests indiate Fig.4 Ultrasoni leak deteting three-dimensional equipment vauum gauge leak ultrasoni sensor amplifier iruit + flapper valve AD flapper valve vauum ontainer vauum pump 3-dimension equipment Fig.5 Ultrasoni leak detetion test verifiation devie shemati In the test, open the vauum pump and evauate the ontainer as vauum state. After ensure the flapper valve losed, hange the appropriate leak and open the flapper valve, simulate the leak on orbit to produe ultrasoni. Put the ultrasoni test system on the 3-dimension braket, aommodate appropriate oordinate, aquire ultrasoni and reord spetrum (done by the PC software), 3 data olleted at eah loation, alulate the average, then get the maximum value and take along further analysis. 3.1 The distane test and result analysis The formula (1) shows that, if the sound signal from the leak do not attenuate,

9 the sound pressure reeived by sensor is inverse proportion to the square of reeiving distane. During the test, the detetion reeiver is plaed on the x shaft, moving on the axis at different distanes and reord the spetrum. Control the distane between sensor and leak by hanging the distane from mm to 5 mm. Measure the sound pressure L hanging from the distane and different diameter of.8mm, 1.5mm and.mm different leak. Speifi operations: open the vauum pump and pumped to balane state, hange the required leak and unsrew the flapper valve, regulate the sensor to an appropriate loation, measure 3 times at eah loation, take the maximum value at enter frequeny and then take the average value as table 3 shows. Table 3 Sound pressure test results hange with distane The distane between sensor and leak d/mm Sound pressure of different diameter leak P /mv.8mm 1.5mm.mm Under the same boundary onditions, the leak pressure is only the funtion of distane, the sound pressure dereases with the distane inreases. Paint the data of table 3 in a two-dimensional hart, fit the data to a polynomial equation and get the urve of 3 different leaks as fig.6 shows m m 1 y = -8E-6x x x y = -E-6x 3 +.8x x y = -1E-6x x x Fig.6 Aousti pressure urve with distane of different leaks

10 Aording to the experimental and the third-order polynomial fit to the data, we an obtain onsistent urve, the sound pressure hange from distane fit to the formula: 3 F ( x) y Ax Bx Cx D (13) From the data in table, the fitted urve and the oeffiients of the polynomial equation, we an find that the model of sound pressure hange with distane is aord with the 3-order Taylor polynomial of. Aording to the sound strength formula (1) and redution as the relationship between sound pressure and distane: P( r) I rs A1 f ( r) A'(1 ( r 1)) f ( x) (14) r Evolve 3-order Taylor polynomial equation of formula (14), we an get: 1 3 f ( x) A' ax + bx - x + d (15) 1 x In the formula (15): A', a, b,, d are positive; Test result formula (13) is math well with the theoretial analysis (15) 3. Reeiving angle test and results analysis The formula (1) shows that, if the angle between aousti soure of leak and the reeiving plane exists, the reeiving sound pressure has osine result. y soure x P(5,-,) Fig.7 A shemati view of the sound pressure test on leak detetion diretion Figure 7 shows a test devie we established to loate the ultrasoni signal reeiver. R is the radius, is the rotation angle, L is the distane between detetor entral axis to the leak entral axis, L 1 is the distane between detetor and leak plane, S is the area of reeiver, S is the effiieny reeiving area, a is the angle between reeiver normal to the onnet line of leak and reeiver enter. So we an aquire the formula (16):

11 (16) We tested sound pressure of sensor at the angle of º, 3 º, 6 º, 9 º and the results are shown in Table 4 Table 4 Sound pressure test results at point P hange by angle Sound soure angle between the surfae and the reeiving surfae α Sound pressure of different diameters leak ase L /mv.8mm 1.mm 1.5mm.mm The sound pressure hange by angle of different leaks an be drawn in the Fig.8, in whih the y oordinate is sound pressure and the x oordinate is the angle between sound soure and reeiver surfae mm 1.mm 1.5mm.mm Fig8 Sound pressure test results at reeiving point P with angle hanges As shown in the test data, at the angle of 3, the reeiving signal inreases largely, and at the angle of 6 the sound pressure get the peak value, but at the angle of 9º, the signal dereases rapidly. We an onlude that: the orresponding value of α is 88.6 º, 5 º, 4 º, 47 º when the test angle is º, 3º, 6º, 9º, and the effetive test area is orrelation with osine α, the orresponding value is , the biggest signal in the test are aquired at the angle of 6º, whih is the same with theoretial value. 4 The design of ultrasoni leak detetor Based on the theoretial analysis and test researh, aording to the inside test of

abin, hoose the high signal to noise spetrum as the leak harater signal, and amplified by a four-lass amplifier iruit, extrat the faint ultrasoni signal from the environment noise bakground, send the

The theoretial detetor an show the result in LCD sreen, and the sound pressure onnets with distane measurement by laser.

12 abin, hoose the high signal to noise spetrum as the leak harater signal, and amplified by a four-lass amplifier iruit, extrat the faint ultrasoni signal from the environment noise bakground, send the analog signal to DSP iruit with embedded ontrol preision of 3M 16bit AD, FFT transformation, harater spetrum aumulation, harater signal ontrast and leak estimation. The theoretial detetor an show the result in LCD sreen, and the sound pressure onnets with distane measurement by laser. The detetor is portable to be used in onveniene, whih is shown in figure 9, and the tehnial indiator of the detetor is shown in Table5. Fig. 9 Portable ultrasoni leak detetor for spaeraft abin Table 5 Tehnial indiators No. Tehnial indiators 1 1) air vauum, leak,leak rate equivalent to.8pa m 3 /s; atmospheri side measurement, ).MPa air, leak, Leak rate equivalent to.8pa m 3 /s; vauum side measurement, 3).MPa air,better than leak, air vauum,sensing range up to 1mm 1mm with a.3mm leak, and the position auray is better than mm 3 Measured weight 1.kg 4 Working power onsumption:.w 5 Conlusion This artile has provided for the development of manned spaeraft portable leak detetor with theoretial support, analyzed the priniple of ultrasoni from leak, verified the rationality of theory analysis, developed a portable ultrasoni leak detetor with high sensitivity used in abin, whih provides tehnology support for spaeraft leak detetion in orbit.

13 Referenes: [1] Yu Xinfa, Yan Rongxin. The study of spae station leak detetion tehnology on orbit. Spaeraft Environment Engineering, 8, 5(): 177~18. [] Yan Rongxin. Monitoring Leak of Spae Station with Diretion Vauum Gauge. Spaeraft Environment Engineering, 6, 3(): 57~67. [3] R.Reusser, S.D.Holland, R.A.Roberts, and D.E.Chimenti, Array-based Aousti Leak Loation in Spaeraft Strutures, in: AIP Conferene Proeedings, 7, vol. 894, [4] A.Hoover. Maryland Company Expanding Tehnology in Spae - NASA Won't Leave Earth Without the CTRL UL11. In: CTRL Systems, In,,1. [5] NASA. Low Level Leaks. Spinoff. 1998, 96. [6] [7] [8] [9] S. D. Holland, R. Roberts, D. E. Chimenti, and M. Strei, Two-Sensor Ultrasoni Spaeraft LeakDetetion Using Struture-Borne Noise, Aoustis Researh Letters Online, 5, 6(), [1] S. D. Holland, R. Roberts, D. E. Chimenti, and M. Strei, Leak Detetion in Spaeraft Using Struture-Borne Noise with Distributed Sensors. Applied Physis Letters, 5,8(6), 1-3. [11] Juoho Song, Stephen D. Holland, and D.E.Chimenti, A Spherially Foused Capaitive-film Air-oupled Transduer,AIP onferene,6:98~915. [1] S. D. Holland, R. Roberts, D. E. Chimenti, and J. H. Song, An Ultrasoni Array Sensor for SpaeraftLeak Diretion Finding, Ultrasonis, 6, vol. 45, [13] Gong Qihun, Ye Qian, Liu Chengliang Wang Yonghong. Study and Design of a New Leak-detet System Based on Ultrasoni Appliation of Eletroni Tehnique, 5, 3, 36~39. [14] Wang Yonghong. Appliation and researh of DSP in the portable air-leakage detetor, Mahinery. 5, 3(3): 56~59. [15] Yang Jiang, Gong Qihun, Ye Jian, Liu Chengliang. The Theoretial Analysis and Experiments of Using Ultrasoni to Inspet the Leak Amount. Journal of Shanghai Jiaotong University. 6, 4(): 4~6. [16] Liao Pingping, Cai Maolin. High auray method of ultrasoni gas leak diretion detetion based on time delay estimation. Journal of Beijing University of Aeronautis and Astronautis, 13, 39(3). [17] Zhan-Hu Liu,Xiao-Dong Niu. Method for aousti leak detetion of fast reator steam generator using maximum modulus based on wavelet transform. In:Proeedings of the Fourth International Conferene on Mahine Learning and Cybernetis.Guang Zhou, 5, 8 [18] Shang Dewei. The Tehniques Study of Pipeline Leak Detetion Based on Ultrasoni Cross-Correlation, Xi an Industry University. 3.

14 [19] Guo Xin, Yan Rongxin Ultrasoni leak testing method and its appliation. Spaeraft Environment Engineering, 1, 7(6): 739~741 [] Meng Donghui, Yan Rongxin, GuoXin. Leak detetion method for in-orbit spaeraft using irular ultrasoni sensor array. Spaeraft Environment Engineering, 11,8(3): 74~76 [1] Guo Xin, Yan Rongxin. Improvement of sensitivity of ultrasoni leak testing for spaeraft. Spaeraft Environment Engineering, 11, 8(4): 37~374 [] Yan Rongxin, Li Weidan, Study on the leak test tehnology of spaeraft using ultrasoni,13,june,19-1.th Singapore International Non Destrutive Testing Conferene and Exhibition, Singapore. [3] Li Weidan, Yan Rongxin, Sun Wei, Qi Lei. The leak ultrasoni detetion test for manned spaeraft. Spaeraft Environment Engineering, 14, 31(): 178~181. [4] Zhang Qiang. Aeroaoustis. 1:1~11. [5] Chen Zhuoru, Jin Zhaoming. Fluid Dynamis, 4: 41~411. [6] Ma Dayou. Aoustis. 1983

Study on the leak test technology of spacecraft using ultrasonic

Study on the leak test technology of spacecraft using ultrasonic SINCE2013 Singapore International NDT Conferene & Exhibition 2013, 19-20 July 2013 Study on the test tehnology of spaeraft using ultrasoni Yan Rongxin, Li Weidan Beijing Institute of Spaeraft Environment