• Title/Summary/Keyword: 단순확장형 소음기

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Analytical Study on Performance Evaluation of Large-Sized Silencer using Geometric Similarity Law (기하상사법을 이용한 대형 소음기의 성능평가에 관한 해석적 연구)

  • Yang, Jun-Hyuk;Lee, Boo-Youn;Kim, Won-Jin
    • Journal of Advanced Marine Engineering and Technology
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    • v.34 no.2
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    • pp.275-281
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    • 2010
  • In this paper, a geometric similarity law is introduced to the performance test of a large-sized silencer used in ship engine or plant system. A test of scale-down model enable to yield the cost and time saving in developing large-sized silencer considerably. Two types of silencer, resonator and expansion chamber, were analyzed by a theoretical method and an acoustical FEM(finite element method) in order to obtain geometric similarity variables. A method is proposed to estimate the transmission loss of prototype model using the test results of scale-down model. Two actual large-sized silencer, which consist of resonator and expansion chamber, were analysed by an acoustical FE analysis. Consequently, the proposed method predicts effectively the performance of prototype silencers using those of scale-down models.

A study on the acoustic performance of a silencer according to the change of properties of absorbing material (흡음재 물성치 변화에 따른 소음기 음향성능 연구)

  • Lee, Yongbeom;Yang, Haesang
    • The Journal of the Acoustical Society of Korea
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    • v.40 no.4
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    • pp.278-289
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    • 2021
  • In this study, the acoustic performance of a dissipative silencer used in the ship with excellent performance compared to its size was predicted and analyzed using a numerical analysis method to reduce the pipe noise. To this end, the performance of the single expansion chamber-shaped silencer was verified using experimental and numerical analysis methods. The acoustic performance of the silencer was expressed using the Transmission Loss (TL), an indicator of its own performance, and the result was derived using the two-load method, which measured by changing the impedance at the end of the pipe. For the numerical analysis method, a general-purpose finite element analysis program was used, and the Delany-Bazley-Miki model with the flow resistivity of the sound absorbing material as an input parameter was applied. Finally, we compared the experimental and simulated results for each of the acoustic performances of the single expansion type and the dissipative silencer to confirm the consistency of the results, and predicted and analyzed the simulation results for four cases according to the properties of the sound absorbing material.

A Modified Simple Acoustic Analysis of Rectangular Simple Expansion Chamber with Consideration of Higher Order Modes (고차모드를 고려한 사각형 단순 확장관의 간편음향해석법의 개선)

  • 김봉준;정의봉;황상문
    • Journal of KSNVE
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    • v.9 no.2
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    • pp.340-347
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    • 1999
  • The acoustic performance of reactive type single expansion chamber can be calculated theoretically by plane wave theory. But higher order model should be considered to widen the frequency range. Mode matching method has been developed to consider higher order modes, but very complicated algebra should be used. Munjal suggested a numerical collocation method, which can overcome the shortcomings of mode matching method, using the compatibility conditions for acoustic pressure and particle velocity at the junctions of area discontinuities. But the restriction of Munjal's method is that the ratio between the area of inlet(or outlet) pipe and that of chamber must be natural number. In this paper, the new method was suggested to overcome the shortcomings of Munjal's method. The predictions by this method was also compared with those by the finite element method and Munjal's method in order to demonstrate the accuracy of the modified method presented here.

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Acoustic Characteristics of Mufflers with an Extended Inlet and Outlet (입출구가 연장된 동심형 소음기의 음향해석)

  • 이준신
    • The Journal of the Acoustical Society of Korea
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    • v.21 no.5
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    • pp.503-509
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    • 2002
  • Cylindrical chamber silencers with an extended inlet and outlet are extensively used in many application fields to reduce the propagated noise in ducts. The basic attenuation effectiveness in the low frequency region can be explained by the reactive wave action inside the expansion chamber associated with the geometric configurations of the inlet and outlet locations, and the area expansion of the jacket. In this study. an acoustic analysis is carried out for a concentric extended pipe inserted into a simple expansion chamber. An algebraic equation is derived by using the eigenfunction expansion and orthogonality principle in which the acoustic pressures and particle velocities defined on each subdivided surface are expressed by the separable coordinates. By using the proposed analytical method, transmission losses are predicted for several configurations of the concentric extended systems and they agree very well with experimental results.

An Acoustic Analysis of Mufflers with a Concentric Extended Pipe (동심 연장관형 소음기의 음향해석)

  • Lee, Jun-Shin;Lee, Jeong-Guon
    • The Journal of the Acoustical Society of Korea
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    • v.14 no.1
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    • pp.108-114
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    • 1995
  • Cylindrical chamber mufflers with an extended inlet or outlet are extensively used in many application fields to reduce the propagated noise in ducts. The basic attenuation effectivencess in the low frequency region can be explained by the reactive wave action inside the expansion chamber associated with the geometric configurations of the inlet and outlet locations, and the area expansion of the jacket. In this study, an acoustic analysis is carried out for a concentric extended pipe inserted into a simple expansion chamber. An algebraic equation is derived by using the eigenfuction expansion and orthogonality principle in which the acoustic pressures and particle velocities defined on each subdivided surface are expressed by the separable coordinates. By using the proposed analytical method, transmission losses are predicted for several configurations of the concentric extended systems and they agree very well with experimental results.

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ACOUSTIC ANALYSIS OF RECTANGULAR SIMPLE EXPANSION CHAMBER WITH CONSIDERATION OF HIGHER ORDER MODE OF INLET/OUTLET (입.출구의 고차모드를 고려한 사각형 단순확장관의 음향해석)

  • 이정환
    • Journal of Advanced Marine Engineering and Technology
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    • v.23 no.6
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    • pp.748-754
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    • 1999
  • The acoustic performance of reactive type single expansion chamber can be calculated theoretically by plane wave theory. But higher order modes should be considered to widen the frequency range. Munjal has suggested the method for analyzing the acoustic properties of simple expansion chamber with taking into consideration of higher order mode of inlet/outlet. But his method cannot predict the acoustic properties exactly when the dimensions of inlet/outlet and expansion chamber have not integer multiples. In this paper the new method was suggested to overcome the shortcomings of Munjal's method The predictions by this method were also compared with those by the finite element method.

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Acoustic Analysis of Circular Simple Expansion Chamber with Arbitrary Location and Cross-Section Area of Inlet/Outlet (원형단순확장관의 입$\cdot$출구 위치와 단면 크기를 고려한 음향해석법)

  • 김봉준;정의봉;황상문
    • Journal of KSNVE
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    • v.9 no.5
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    • pp.914-921
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    • 1999
  • There are many theoretical investigations to analyze higher order mode of reactive type single expansion chambers with offset inlet/outlet locations. But the conventional method has the restriction that the ratio between the area of inlet(or outlet) pipe and that of chamber must be natural number. In the paper, a new method was suggested to apply the Kim's method to silencer with circular cross-section. Not only the offset location but also the magnitude of cross-section area of inlet/outlet pipe can be considered by the suggested method. The predictions by this new method also compared with those by the finite element method and Munjal's method in order to verify the accuracy of the suggested method presented here.

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Acoustical Performance Analysis of Simple Expansion Silencer using Lattice Boltzmann Method (격자 볼츠만법을 이용한 단순 확장형 소음기 음향특성 해석)

  • Lee, Songjune;Lee, Gwang-Se;Cheong, Cheolung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2014.10a
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    • pp.966-972
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    • 2014
  • The Lattice Boltzmann Method (LBM) has attracted attention as an alternative numerical algorithm for solving fluid mechanics, and its intrinsic unsteadiness and weak numerical damping make it more suitable for aeroacoustic problems. In this paper, applicability of the LBM for solving flow noise problems is tested by applying it to predict transmission loss of a simple expansion silencer. The time history of the static pressure is recorded at the inlet and outlet pipes. The transmission loss (TL) of the muffler is computed by using three point method and two source method, respectively. The TL calculated using the LBM is compared with that computed using finite element method (FEM) and measured data. It is found through these comparisons that the LBM is capable of predicting TL of the simple expansion silencer accurately, which it is difficult to predict using the conventional CFD methods based on the RANS solvers.

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Modified Mode Matching Technique for Analyzing Simple Expansion Chamber with Arbitrary Inlet/Outlet Location (임의의 입ㆍ출구 위치를 가지는 소음기 해석을 위한 개선된 모드일치법)

  • Kim, Bong-Jun;Jeong, Ui-Bong;Lee, Jeong-Hwan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.5 s.176
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    • pp.1314-1322
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    • 2000
  • The acoustic property of reactive type single expansion chamber can be analyzed by traditional plane wave theory. This theory can be applied in low frequency range and has good performance. But this theory can't include higher order modes, therefore another method is essential to analyze acoustic filter in high frequency range. Many researcher suggested the method that can concern higher order modes, and their methods are using mode matching technique. But there is no method that can be applied to the analysis of single expansion chamber with arbitrary inlet/outlet duct position and numbers of higher order modes of inlet/outlet duct and middle chamber. In this paper, the method which can analyze single expansion chamber with arbitrary inlet/outlet duct position and numbers of higher order modes of inlet/outlet duct and middle chamber using fundamental mode matching technique, was suggested and the predictions by this method was compared with those by the finite element method, and the influence of inlet/outlet location to acoustic performance of single expansion chamber is investigated and explained by higher order mode effects.

The Application of a Direct Coupled BEM-FEM Model to Predict the TL Characteristics of Simple Expansion Silencers with Vibratory Walls (진동 벽면을 가진 단순 확장형 소음기 모델의 투과손실 특성 해석을 위한 DIRECT BEM-FEM 연성 모델의 적용)

  • Choi, C.H.;Kim, H.Y.
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.6
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    • pp.24-30
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    • 1998
  • A directly coupled Boundary Element and Finite Element Model was applied to the dynamic analysis of a coupled acoustic silencer with vibratory wall. In this cupled BEM-FEM muffler model, the BEM model was used to discretize the acoustic cavity and the FEM model was used to discretize the vibratory wall structure. Then the BEM model was coupled with the FEM model. The results of the coupled BEM-FEM model for the dynamic analysis of the simple expansion type reactive muffler configurations with flexible walls were verified by comparing the predicted results to analytical solutions. In order to investigate the effects of the muffler's structural flexibility on its transmission loss(TL) characteristics, the results of the coupled BEM-FEM model in conjunction with the four-pole parameter theory were utilized. The muffler's TL characteristics using the BEM-FEM coupled model with flexible walls as compared to other muffler configurations was studied. Finally the muffler's TL values with respect to different wall's thickness are predicted and compared.

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