Binsheng, Zhu

Hong, Guo

Huang, Zhigang

Qian, Canyu

English

Purdue E-Pubs

Purdue UniversityPurdue e-PubsInternational Compressor Engineering Conference School of Mechanical Engineering2010The Diagnosis and Optimization of ScrollCompressor Noise Based on the Theory of Near-Field Acoustical HolographyZhigang HuangGuangdong Meizhi CompanyGuo HongGuangdong Meizhi CompanyZhu BinshengGuangdong Meizhi CompanyCanyu QianGuangdong Meizhi CompanyFollow this and additional works at: https://docs.lib.purdue.edu/icecThis document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu foradditional information.Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at https://engineering.purdue.edu/Herrick/Events/orderlit.htmlHuang, Zhigang; Hong, Guo; Binsheng, Zhu; and Qian, Canyu, "The Diagnosis and Optimization of Scroll Compressor Noise Basedon the Theory of Near-Field Acoustical Holography" (2010). International Compressor Engineering Conference. Paper 2016.https://docs.lib.purdue.edu/icec/2016 1392, Page 1 International Compressor Engineering Conference at Purdue, July 12-15, 2010  The Diagnosis and Optimization of Scroll Compressor Noise Based on the Theory of Near-Field Acoustical Holography Zhigang Huang 1*, Hong Guo 2, Binsheng Zhu3, Canyu Qian41R&D Section,Guangdong Meizhi Compressor Co. Ltd., Guangdong,P.R.China Tel:86-757-22329129,Fax:86-757-22297554,E-mail:Zghuang@sohu.com 2R&D Section,Guangdong Meizhi Compressor Co. Ltd., Guangdong,P.R.China Tel:86-757-22329038,Fax:86-757-22297554,E-mail:Guoh@chinagmcc.com 3R&D Section,Guangdong Meizhi Compressor Co. Ltd., Guangdong,P.R.China Tel:86-757-22329411,Fax:86-757-22297554,E-mail:zhubs@chinagmcc.com4 R&D Section,Guangdong Meizhi Compressor Co. Ltd., Guangdong,P.R.China Tel:86-757-22329053,Fax:86-757-22297554,E-mail:Qiancy@chinagmcc.com* P.H.D & Senior engineer  Graduated from Zhejiang university, china ABSTRACT Based on the theory and characteristics of the near-field acoustical holography (NAH), the scroll compressor acoustic holography measurement is achieved in this paper. The sound field color image is reconstructed by using the measurement data, and then the noise positions of various frequency bands are identified and located. Moreover, the effect of mechanical structure on the noise is analyzed. Then, by optimization and designing of the relevant structural, the noise of the scroll compressor has been effectively reduced. This technology applied successfully to the noise test of the scroll compressor, not only to make up the problem of insufficient information of the traditional measurement method, but also greatly improve work efficiency and shorten the product development cycle. 1. INTRODUCTION Because of its high efficiency, small vibration, simple structure, etc., the scroll compressor techniques has been rapid development in air-conditioned filed, especially 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 key performance indicators are getting more and more industry attention.  The scroll Compressor traditional noise measurement data is usually indicated by frequency spectrum, which can accurately reflect the size of compressor noise and noise frequency bands. However, this method does not locate and identify the sound source locations, often leads the designers not to know what to do. This not only extended the R&D cycle, but also it is difficult to achieve design goals.  The acoustic holography technology is a loud reconstruction technique, which reconstruct sound three-dimensional image by 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 volatility. The technology could achieve sound source position and the other wealth of sound source information by sound field visualization. So, this technology is essential to actual noise vibration analysis, 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. Maynard further put forward the near-field acoustic holography (NAH) [2]. The technology can achieve effectively a low-level radiation acoustic composition, especially for evanescent wave (evanescent wave) by controlling distance between holographic surface and measurement surface less than acoustic wavelength range. Thus, a high sound field reconstruction graphics can be achieved by breaking the drawbacks of the traditional sound field reconstruction is subject to wavelengths. Near-field acoustic holography (NAH) not only can identify and locate noise sources more effectively [3], but also reduces the measurement requirements greatly.  1392, Page 2 International Compressor Engineering Conference at Purdue, July 12-15, 2010 At present, this method have been widely used in the aircraft cabin interior, automotive interior sound field, the noise positioning inside the machine [4] [5 ].  Based on the study of near-field acoustic holography (NAH) theory and characteristics, the holographic sound pressure measurements of the scroll compressor is realized, and then the 3D sound field image is reconstructed.  According to the sound field visualization graphics, the noise positions of various frequency bands are identified and located, so as to the optimization of the related structures is finished. The successful applications of NAH in the noise measurements of scroll compressor, not only quantify the effect of different structural on the noise, but also greatly shorten the development cycle. 2. NEAR-FIELD ACOUSTIC HOLOGRAPHY THEORY AND CHARACTERISTICS According to the small amplitude acoustic wave equation for ideal fluid medium [6] [7], the Helmholtz steady-state sound field equation can be expressed as:                                                     0),,(),,( 22 ??? zyxpkzyxp                                                                         (1) where, ),,( zyxp  is space complex sound pressure and a function of Cartesian coordinates zyx ?? ,??2?? cwk  is acoustic number, c  is the speed of sound, ?  is the characterized wavelength. The boundary conditions of equation (1), ),( yxpD  and ),( yxpN  are Dirichlet boundary conditions and Neumann boundary conditions of flat 0?z respectively. When the situation 0?z , the space is the free field, that is to say, all sound sources are located below the flat 0?z . According to the Green's formula, the solution of equation (1), that is, the sound pressure at any point of space as follows:  33,, ),,(),(),,( dydxzzyyxxgyxpzyxp NDSND ????????? ?                                (2) Where, S indicated that the integral carried out in the infinite boundary plane, NDg , is Green's function on the infinite plane.  32/)1(),,( reikrzzyxg ikrD ???                                                            (3)  32/),,( rezyxg ikrN ??                                                                             (4)  Where, 222 zyxr ???If the two-dimensional continuous Fourier transform along the direction yx?  is defined as follows: dxdyeyxfkkP ykxkiyx yx)(),(),( ????????? ??                                                        (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:  ),,(),(),,( ,, zkkGkkPzkkP yxNDyxNDyx ?                                                     (6)  where, ),,( zkkP yx , ),(, yxND kkP are the two-dimensional continuous Fourier transform of sound pressure ),,( zyxp  and the boundary conditions ),(, yxP ND  respectively. And ),,(, zkkG yxND  is the two-dimensional Fourier transform of NDg , . So, the analytical expression as follows:  zikyxDzezkkG ?),,(                                                                                (7) xzikyxN kezkkG z /),,( ?                                                                        (8) When k 222 ?? yx kk , then )( 222 yxz kkkk ???                                                                            (9) When k 222 ?? yx kk , then  222 )( kkkik yxz ???                                                                         (10) The Neumann boundary conditions as follow:  0/),,(),,( ???? zzzyxpizyxPN                                                               (11)   1392, Page 3 International Compressor Engineering Conference at Purdue, July 12-15, 2010 The relationship between the two-dimensional Fourier transform ),(PN yx kk  of the boundary conditions and the two-dimensional Fourier transform ),( yx kkV  of the normal vibration velocity of the particle on plane 0?z  as follows:  ckkkVkkP yxyxN ?),(),( ?                                                                         (12)  Where, ? is the average density of the acoustic medium.  The equation (7), (8) and (12) are taken into equation (6), so equation (6) can be written separately:  zikyxDyxzekkPzkkP ),(),,( ?                                                                         (13) zzikyxyx kekkckzkkP z /),(),,( ??                                                                (14)  At the time 0?? Hzz , the formula (13) and (14), denote respectively the relationship between the sound pressure of the plane Hzz ? and the sound pressure and the vibration velocity of particle for boundary condition 0?? Szz . For any two-plane Hzz ? and Szz ?  ( 0?? SH zz ) , a more general relationship can established by equation (13) and (14).  )(),,(),,( SHz zzikSyxHyx ekkkPzkkP??                                                        (15) zzzikSyxHyx kekkkckzkkP SHz /),,(),,()( ?? ?                                            (16)  According to formula (15) and (16), and the sound pressure or the particle vibration velocity of flat Szz ? are known, the sound pressure situation of a more distant plane Hzz ? can be predicted. Through the Euler formula, the particle vibration velocity of the plane Hzz ?  can be easily achieved. Known the sound pressure data of the plane Hzz ?  (holographic surface), the sound pressure and the particle vibration velocity of a more near-surface Szz ? (reconstruction surface) can also be inversed. At this point, the basic reconstruction formula about planar near-field acoustic holography can be setup:  )(),,(),,( SHz zzikHyxSyx ekkkPzkkP??                                                            (17) ckekkkPkzkkV SHz zzikHyxzSyx ?/),,(),,( )( ???                                           (18) 3. EXPERIMENTAL MEASUREMENT According to the above principle, the acoustic holography measurements are carried out on a scroll compressor. This experiment was finished in semi-anechoic chamber, where the silencer body noise of chamber is below 30dB. Test equipment include in 27kw gas load test-bed, 24-channel data transmission system, 10 microphones, test rack, data ??????????????????????????????????Fig.1 Microphones vertical layout Fig.2 Measurement arrays  1392, Page 4 International Compressor Engineering Conference at Purdue, July 12-15, 2010 acquisition and processing system, as well as a scroll compressor that the capacity is 15kw.  Near-field acoustical holography technology measure generally complex sound pressure or particle vibration vectors of surface through the sensor arrays, and then the sound pressure particle velocity vector and three-dimensional sound intensity vector can be achieved by using some algorithm to reconstruct the sound field to be any point on the object surface tested.  Figure 1 is a microphone vertical layout, in which nine microphones vertically rigid connections in the test rack 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 array of microphones gradual move from left to right, each moving distance is 30mm. Once the test rack is stable, the test data can be collected, until the completion of all data collection. Figure 2 is the microphones array used in practical test, which is a total of eight rows. By 8 rows 9 arrays tests, the complete coverage of the local oscillator is achieved. In the testing process, the reference microphone is always immovability. When the data acquisition is completed, the signal processing equipment deal with all array 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 effectively the test equipment requirements and reduce cost of test.  4. TEST RESULTS AND ANALYSIST4.1 Measurement data analysisThe traditional test approach of the noise indicates usually the size and band of noise occurred by frequency spectrum, seen from Fig.4. However, this method can not reveal the location of noise sources, so that designers have become blind in the noise optimization, and is difficult to achieve first-class design production. (a) 1000Hz                                             (b) 1600Hz (c) 2000Hz                                            (d) 4000Hz Fig.3 The holographic color image  1392, Page 5 International Compressor Engineering Conference at Purdue, July 12-15, 2010 In this paper, the focus of the frequency bands are determined based on frequency spectrum data, seen from Fig.4 and table 1, is 1600Hz, 2000Hz and 4000Hz respectively. In order to ensure information integrity and extends the measuring range, the holographic test data of 500Hz, 1000Hz and 8000Hz 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 frequency of 1000Hz, 1600Hz, 2000Hz and 8000Hz. 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 size ?????????????? ????????????? ??????????????????????????????? ????????????????????????????? ???????? ???????????? ???????? ????????????? ???????? ?????????????????????????????? ???????? ??????????????? ???????? ????????????????????????????????? ???4.2 Noise optimization  From Figure 3 and Table 1, the maximum noise occurred in 1600Hz, 2000Hz and 4000Hz, and the noise sources are located nearby the discharge pipe and bottom case. The problem caused by balance weight is excluded according to  Fig.4 Noise frequency spectrum before optimization Fig.5 Noise frequency spectrum after optimization balance principle and the vibration size of main frame. Moreover, it is preliminary judged the cause is induced by  1392, Page 6 International Compressor Engineering Conference at Purdue, July 12-15, 2010 high speed gas flow. Figure 5 is the noise frequency spectrum by adopting traditional measurements method after structural optimization. It can be seen from this picture, the noise sizes lower than Fig.4 about 8¬9dB, and the maximum effective pressure noise is 66.6dB. This performance improves significantly and basically meets design requirement. 5. CONCLUSIONS In this paper, a scroll compressor acoustic holography test is achieved based on theoretical research of near-field acoustic holographic technology. Through the visualization technology, the sound source location of the different frequency bands are identified and located. Furthermore, the cause of problem is analyzed depending on the location of sound source, as well as scroll compressors structural features. The value of the compressor noise is reduced successfully through structural optimization design.  The application of Near-field full-noiselessly holography technology successful in the development of scroll compressor, not only provides the quantitative and significant experimental 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.  REFERENCES [1] Yang Chao Chen Jin etc. The Research Progress of Localized near-field acoustical holography [J], Journal of Agricultural Machinery, 2008, 39 (4): 180 ~ 186  [2] E.G. Williams and J.D. Maynard. Numerical Evaluation of the Rayleigh Integral for Planar Radiators Using the FFT[J]. Journal Acoustic Society of America, December, 1982, 72(6):2020¬2030. [3] Chen Xinzhao, BI Chuanxing, Li Weibin. Near-field Acoustic Holography and Its Application in the Noise Source Identification [J]. vibration and noise of modern technology, 2005 (4): 1 ~ 13. [4] K. B. Ginn, J. Hald Engine Noise: Sound Source Location Using the STSF Technique, SE-A931307,1993. [5] Williams EG, Houston BH, Herdic PC, et al. Interior Near-field Acoustical Holography in Flight. J. Acoust. Soc. Am, 2000,108(4):1451¬1463. [6] E.G. Williams and J.D. Maynard. Holographic Imaging Without the Wavelength Resolution Limit, Physics Review Letters, 1980, Vol. 45, 554¬557 [7] Wang and S. F. Wu, Helmholtz Equation-least-squares Method for the Reconstructing the Acoustic Pressure Field, Journal of the Acoustical Society of America, 1997, Vol. 102: 2020¬2032 

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

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

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