The Diagnosis and Optimization of Scroll Compressor Noise Based on the Theory of Near- Field Acoustical Holography

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1 Purdue Universit Purdue e-pubs International Compressor Engineering Conference chool of Mechanical Engineering 2010 The Diagnosis and Optimiation of croll Compressor oise Based on the Theor of ear- Field Acoustical olograph Zhigang uang Guangdong Meihi Compan Guo ong Guangdong Meihi Compan Zhu Binsheng Guangdong Meihi Compan Canu Qian Guangdong Meihi Compan Follow this and additional wors at: uang, Zhigang; ong, Guo; Binsheng, Zhu; and Qian, Canu, "The Diagnosis and Optimiation of croll Compressor oise Based on the Theor of ear-field Acoustical olograph" (2010. International Compressor Engineering Conference. Paper This document has been made available through Purdue e-pubs, a service of the Purdue Universit Libraries. Please contact epubs@purdue.edu for additional information. Complete proceedings ma be acquired in print and on CD-ROM directl from the Ra W. erric Laboratories at erric/events/orderlit.html

2 1392, Page 1 The Diagnosis and Optimiation of croll Compressor oise Based on the Theor of ear- Field Acoustical olograph Zhigang uang 1 *, ong Guo 2, Binsheng Zhu 3, Canu Qian 4 1 R&D ection,guangdong Meihi Compressor Co. Ltd., Guangdong,P.R.China Tel: ,Fa: , Zghuang@sohu.com 2 R&D ection,guangdong Meihi Compressor Co. Ltd., Guangdong,P.R.China Tel: ,Fa: , Guoh@chinagmcc.com 3 R&D ection,guangdong Meihi Compressor Co. Ltd., Guangdong,P.R.China Tel: ,Fa: , hubs@chinagmcc.com 4 R&D ection,guangdong Meihi Compressor Co. Ltd., Guangdong,P.R.China Tel: ,Fa: , Qianc@chinagmcc.com * P..D & enior engineer Graduated from Zhejiang universit, china ABTRACT Based on the theor and characteristics of the near-field acoustical holograph (A, the scroll compressor acoustic holograph measurement is achieved in this paper. The sound field color image is reconstructed b using the measurement data, and then the noise positions of various frequenc bands are identified and located. Moreover, the effect of mechanical structure on the noise is analed. Then, b optimiation and designing of the relevant structural, the noise of the scroll compressor has been effectivel reduced. This technolog applied successfull to the noise test of the scroll compressor, not onl to mae up the problem of insufficient information of the traditional measurement method, but also greatl improve wor efficienc and shorten the product development ccle. 1. ITRODUCTIO Because of its high efficienc, small vibration, simple structure, etc., the scroll compressor techniques has been rapid development in air-conditioned filed, especiall in the field of commercial air conditioners. With the social development and progress, the requirement of air-conditioned comfort and environmental protection continues to increase. Therefore, the noise and vibration of the compressor as e performance indicators are getting more and more industr attention. The scroll Compressor traditional noise measurement data is usuall indicated b frequenc spectrum, which can accuratel reflect the sie of compressor noise and noise frequenc bands. owever, this method does not locate and identif the sound source locations, often leads the designers not to now what to do. This not onl etended the R&D ccle, but also it is difficult to achieve design goals. The acoustic holograph technolog is a loud reconstruction technique, which reconstruct sound three-dimensional image b using two-dimensional information of the sound pressure field based on the space transform relationship between source surface and the holographic surface and the principles of sound volatilit. The technolog could achieve sound source position and the other wealth of sound source information b sound field visualiation. o, this technolog is essential to actual noise vibration analsis, and is great significance to research radiation characteristics of the source and control the noise [1]. In 1980 s, E.G. Williams and J.D. Manard further put forward the near-field acoustic holograph (A [2]. The technolog can achieve effectivel a low-level radiation acoustic composition, especiall for evanescent wave (evanescent wave b controlling distance between holographic surface and measurement surface less than acoustic wavelength range. Thus, a high sound field reconstruction graphics can be achieved b breaing the drawbacs of the traditional sound field reconstruction is subject to wavelengths. ear-field acoustic holograph (A not onl can identif and locate noise sources more effectivel [3], but also reduces the measurement requirements greatl. International Compressor Engineering Conference at Purdue, Jul 12-15, 2010

3 1392, Page 2 At present, this method have been widel used in the aircraft cabin interior, automotive interior sound field, the noise positioning inside the machine [4] [5 ]. Based on the stud of near-field acoustic holograph (A theor and characteristics, the holographic sound pressure measurements of the scroll compressor is realied, and then the 3D sound field image is reconstructed. According to the sound field visualiation graphics, the noise positions of various frequenc bands are identified and located, so as to the optimiation of the related structures is finished. The successful applications of A in the noise measurements of scroll compressor, not onl quantif the effect of different structural on the noise, but also greatl shorten the development ccle. 2. EAR-FIELD ACOUTIC OLOGRAPY TEORY AD CARACTERITIC According to the small amplitude acoustic wave equation for ideal fluid medium [6] [7], the elmholt stead-state sound field equation can be epressed as: 2 2 p (,, p(,, 0 (1 where, p (,, is space comple sound pressure and a function of Cartesian coordinates, w c 2 is acoustic number, c is the speed of sound, is the characteried wavelength. The boundar conditions of equation (1, p D (, and p (, are Dirichlet boundar conditions and eumann boundar conditions of flat 0 respectivel. When the situation 0, the space is the free field, that is to sa, all sound sources are located below the flat 0. According to the Green's formula, the solution of equation (1, that is, the sound pressure at an point of space as follows: 3 3 p(,, p (, g (,, d d (2 D, D, Where, indicated that the integral carried out in the infinite boundar plane, D is Green's function on the infinite plane. ir 3 g D (,, (1 ir e / 2 r (3 ir 3 g (,, e / 2 r (4 Where, r If the two-dimensional continuous Fourier transform along the direction is defined as follows: i( P(, f (, e dd (5 The two-dimensional Fourier transform on both sides of the equation (2 is carried out, and then two-dimensional convolution theorem is used to calculate, then: P(, PD, ( GD, (, (6 where, P(,, PD, (, are the two-dimensional continuous Fourier transform of sound pressure p (,, and the boundar conditions P D, (, respectivel. And GD, (, is the twodimensional Fourier transform of g D,. o, the analtical epression as follows: i GD (, e (7 i G (, e / (8 When 2 2 2, then ( (9 When 2 2 2, then i ( (10 The eumann boundar conditions as follow: P (,, i p(,, / 0 (11 g, International Compressor Engineering Conference at Purdue, Jul 12-15, 2010

4 1392, Page 3 The relationship between the two-dimensional Fourier transform P ( of the boundar conditions and the two-dimensional Fourier transform V ( of the normal vibration velocit of the particle on plane 0 as follows: P ( V ( c (12 Where, is the average densit of the acoustic medium. The equation (7, (8 and (12 are taen into equation (6, so equation (6 can be written separatel: i P (, PD ( e (13 i P(, c( e / (14 At the time 0, the formula (13 and (14, denote respectivel the relationship between the sound pressure of the plane and the sound pressure and the vibration velocit of particle for boundar condition 0. For an two-plane and ( 0, a more general relationship can established b equation (13 and (14. i ( P(, P( e (15 i ( P(, c( e / (16 According to formula (15 and (16, and the sound pressure or the particle vibration velocit of flat are nown, the sound pressure situation of a more distant plane can be predicted. Through the Euler formula, the particle vibration velocit of the plane can be easil achieved. Known the sound pressure data of the plane (holographic surface, the sound pressure and the particle vibration velocit of a more nearsurface (reconstruction surface can also be inversed. At this point, the basic reconstruction formula about planar near-field acoustic holograph can be setup: i ( P(, P( e (17 V (, P( i ( e / c (18 3. EXPERIMETAL MEAUREMET According to the above principle, the acoustic holograph measurements are carried out on a scroll compressor. This eperiment was finished in semi-anechoic chamber, where the silencer bod noise of chamber is below 30dB. Test equipment include in 27w gas load test-bed, 24-channel data transmission sstem, 10 microphones, test rac, data Fig.1 Microphones vertical laout Fig.2 Measurement arras International Compressor Engineering Conference at Purdue, Jul 12-15, 2010

5 1392, Page 4 acquisition and processing sstem, as well as a scroll compressor that the capacit is 15w. ear-field acoustical holograph technolog measure generall comple sound pressure or particle vibration vectors of surface through the sensor arras, and then the sound pressure particle velocit vector and three-dimensional sound intensit vector can be achieved b using some algorithm to reconstruct the sound field to be an point on the object surface tested. Figure 1 is a microphone vertical laout, in which nine microphones verticall rigid connections in the test rac with the spacing of 60mm, and to ensure that it is vertical to holographic surface, while the tenth microphone as a reference. The minimum distance between measuring tangent plane and measured compressor is less than 100mm. After measurements startup, the arra of microphones gradual move from left to right, each moving distance is 30mm. Once the test rac is stable, the test data can be collected, until the completion of all data collection. Figure 2 is the microphones arra used in practical test, which is a total of eight rows. B 8 rows 9 arras tests, the complete coverage of the local oscillator is achieved. In the testing process, the reference microphone is alwas immovabilit. When the data acquisition is completed, the signal processing equipment deal with all arra data collected according to the reference microphone information. Moreover, the pressure holographic data is restored. And then, the vertical holographic plane is tested according as aforementioned. This method can reduce effectivel the test equipment requirements and reduce cost of test. 4. TET REULT AD AALYIT 4.1 Measurement data analsis The traditional test approach of the noise indicates usuall the sie and band of noise occurred b frequenc spectrum, seen from Fig.4. owever, this method can not reveal the location of noise sources, so that designers have become blind in the noise optimiation, and is difficult to achieve first-class design production. (a 1000 (b 1600 (c 2000 (d 4000 Fig.3 The holographic color image International Compressor Engineering Conference at Purdue, Jul 12-15, 2010

6 1392, Page 5 In this paper, the focus of the frequenc bands are determined based on frequenc spectrum data, seen from Fig.4 and table 1, is 1600, 2000 and 4000 respectivel. In order to ensure information integrit and etends the measuring range, the holographic test data of 500, 1000 and 8000 is added. According to above-mentioned measurement principle and method, the holographic image can be gotten. Figure 3 (a ~ (d is the holographic color image corresponding to frequenc of 1000, 1600, 2000 and Then, the location of the noise source can be determined based on the holographic test data of the two planes, the results are written in Table 1. Table.1 The relationship between sound source and noise sie 4.2 oise optimiation From Figure 3 and Table 1, the maimum noise occurred in 1600, 2000 and 4000, and the noise sources are located nearb the discharge pipe and bottom case. The problem caused b balance weight is ecluded according to Fig.4 oise frequenc spectrum before optimiation Fig.5 oise frequenc spectrum after optimiation balance principle and the vibration sie of main frame. Moreover, it is preliminar judged the cause is induced b International Compressor Engineering Conference at Purdue, Jul 12-15, 2010

7 1392, Page 6 high speed gas flow. Figure 5 is the noise frequenc spectrum b adopting traditional measurements method after structural optimiation. It can be seen from this picture, the noise sies lower than Fig.4 about 8 9dB, and the maimum effective pressure noise is 66.6dB. This performance improves significantl and basicall meets design requirement. 5. COCLUIO In this paper, a scroll compressor acoustic holograph test is achieved based on theoretical research of near-field acoustic holographic technolog. Through the visualiation technolog, the sound source location of the different frequenc bands are identified and located. Furthermore, the cause of problem is analed depending on the location of sound source, as well as scroll compressors structural features. The value of the compressor noise is reduced successfull through structural optimiation design. The application of ear-field full-noiselessl holograph technolog successful in the development of scroll compressor, not onl provides the quantitative and significant eperimental data for designers to improve the speed and effectiveness of the development, but also is significance for further understanding of different structure effect on the noise. REFERECE [1] Yang Chao Chen Jin etc. The Research Progress of Localied near-field acoustical holograph [J], Journal of Agricultural Machiner, 2008, 39 (4: 180 ~ 186 [2] E.G. Williams and J.D. Manard. umerical Evaluation of the Raleigh Integral for Planar Radiators Using the FFT[J]. Journal Acoustic ociet of America, December, 1982, 72(6: [3] Chen Xinhao, BI Chuaning, Li Weibin. ear-field Acoustic olograph and Its Application in the oise ource Identification [J]. vibration and noise of modern technolog, 2005 (4: 1 ~ 13. [4] K. B. Ginn, J. ald Engine oise: ound ource Location Using the TF Technique, E-A931307,1993. [5] Williams EG, ouston B, erdic PC, et al. Interior ear-field Acoustical olograph in Flight. J. Acoust. oc. Am, 2000,108(4: [6] E.G. Williams and J.D. Manard. olographic Imaging Without the Wavelength Resolution Limit, Phsics Review Letters, 1980, Vol. 45, [7] Wang and. F. Wu, elmholt Equation-least-squares Method for the Reconstructing the Acoustic Pressure Field, Journal of the Acoustical ociet of America, 1997, Vol. 102: International Compressor Engineering Conference at Purdue, Jul 12-15, 2010