• Title/Summary/Keyword: Expansion Chamber

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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.

CFD-Based Overpressure Evaluation Inside Expansion Chamber-Applied Protective Tunnels Subjected to Detonation of High Explosives (확장챔버를 적용한 방호터널 내부의 CFD 해석 기반 폭발압력 평가)

  • Shin, Jinwon;Pang, Seungki
    • Journal of Korean Association for Spatial Structures
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    • v.23 no.1
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    • pp.25-34
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    • 2023
  • This paper presents a computational fluid dynamics (CFD) analysis to investiagate the effect of expansion chamber on overpressure reduction in protective tunnels subjected to detonation of high explosives. A commercial CFD code, Viper::Blast, was used to model the blast waves in a protective tunnel with a length of 160 m, width of 8.9 m and height of 7.2 m. Blast scenarios and simulation matrix were establihsed in consideration of the design parameters of expansion chamber, including the chamber lengths of 6.1 m to 12.1 m, widths of 10.7 m to 97 m, length to width ratios of 0.0 to 5.0, heights of 8.0 m and 14.9 m, and ratios of chamber to tunnel width of 1.2 to 10.9 m. A charge weight of TNT of 1000 kg was used. The mesh sizes of the numerical model of the protective tunnel were determined based on a mesh convergence study. A parametric study based on the simulation matrix was performed using the proposed CFD tunnel model and the optimized shape of expansion chamber of the considered tunnel was then proposed based on the numerical results. Design recommendations for the use of expansion chamber in protective tunnel under blast loads to reduce the internal overpressures were finally provided.

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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Optimum Design for Inlet and Outlet Locations of Circular Expansion Chamber for Improving Acoustic Performance (원형 단순 확장소음기의 성능향상을 위한 입.출구 위치의 최적설계)

  • An, Se-Jin;Kim, Bong-Jun;Jeong, Ui-Bong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.10 s.181
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    • pp.2487-2495
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    • 2000
  • The acoustic characteristics of expansion chamber will be changed with the variation of inlet/outlet location due to the higher order acoustic mode in a high frequency in which the plane wave theory is not available. In this paper, the acoustic performance of reactive type expansion chamber with circular cross-section is analyzed by using the modified mode matching theory. The sensitivity analysis of four-pole parameters with respect to the location of inlet and outlet is also suggested to increase the acoustic performance. The acoustic power transmission coefficient is used as cost function, and the location of inlet and outlet is used as design variables. The steepest descent method and SUMT algorithm are used for optimization technique. Several results showed that the expansion chamber with optimally located inlet/outlet had better acoustic performance than concentric expansion chamber.

Pressure Rise in the Thermal Expansion Chamber With Arc (유부하시의 열팽창분사식 소호부내의 상승압력)

  • Park, K.Y.;Song, K.D.;Shin, Y.J.;Chang, K.C.;Kim, K.S.;Kim, J.K.
    • Proceedings of the KIEE Conference
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    • 1995.07c
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    • pp.1344-1346
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    • 1995
  • The interrupting capability of gas circuit breakers(GCB) are critically dependent on the pressure rise of the puffer cylinder or the thermal expansion chamber at current zero. Therefore it's very useful for the designers to know the pressure rise there at the design stage. Much effort has been done to predict the pressure rise in the puffer cylinder or the thermal expansion chamber in no-load condition. Thus, we now calculate it with reasonable accuracy with the simple programs coded by ourselves or with the commercial CFD packages. However, it has been still difficult problem to calculate it under the existence of arc. In this paper, we propose a method which can be used to predict the pressure rise in the thermal expansion chamber of thermal expansion type GCB. The method has been applied to the 25.8kV 25kA thermal expansion type model GCB and the calculated results have been compared with those from experiment.

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A Study on the Development of 25.8kV 25kA Gas Circuit Breaker Using Thermal-Expansion Principle(II) (25.8kV 25kA 열팽창분사식 가스차단기 개발에 관한 연구(II) - 팽창실 용적이 차단성능에 미치는 영향 -)

  • Song, K.D.;Park, K.Y.;Shin, Y.J.;Kim, K.S.;Kim, J.G.
    • Proceedings of the KIEE Conference
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    • 1996.07a
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    • pp.80-82
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    • 1996
  • This paper deals with the effects of the volume of thermal expansion chamber on the interrupting performance in thermal expansion type 25.8kV 25kA gas circuit breaker. Model interrupters with 5 type thermal expansion chamber were designed and manufactured. Short-circuit tests were carried out for those model interrupters with 25kA breaking current. Pressure rise in the expansion chamber were measured and compared with the calculated one which was obtained from a self-developed program in our team. The analysis on the interrupting performance of each model interrupter has been done on the base of the short-circuit test results.

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Numerical Analysis for Linear and Nonlinear Attenuation Characteristics of Exhaust Silencer Systems (배기 소음기의 선형 및 비선형 감쇄 특성에 대한 수치해석)

  • 김종태;김용모;맹주성;류명석;구영곤
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.4
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    • pp.179-189
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    • 1996
  • An unstructured grid finite-volume method has been applied to predict the linear and nonlinear attenuation characteristics of the expansion chamber silencer system. In order to achieve a grid flexibility and a solution adaptation for geometrically silencer system. In order to achieve a grid flexibility and a solution adaptation for geometrically complex flow regions associated with the actual silencers, the unstructured mesh algorithm in context with the node-centered finite volume method has been employed. The present numerical model has been validated by comparison with the analytical solutions and the experimental data for the acoustic field of the concentric expansion chamber with and without pulsating flows, as well as the axisymmetric blast flowfield with open end. Effects of the chamber geometry on the nonlinear wave attenuation characteristics is discussed in detail.

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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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Transmission Loss Analysis of Simple Expansion Chambers with Multiple Inlets and Outlets (다입력/다출력관을 갖는 확장관의 투과손실 해석)

  • 박기춘;김양한
    • Journal of KSNVE
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    • v.8 no.5
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    • pp.807-813
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    • 1998
  • Transmission loss of the simple expansion chamber with multiple inlet and outlet ports is obtained. Transfer matrices which represent the relation between the power variables(pressure and velocity) of inlets and outlets depend on the input relatons as well as the acoustic system parameters(i.e. geometry of the chamber, wall admittance, etc.). The analysis has been performed analytically, including the effects of higher order modes for the 2-inlet/1-outlet, 1-inlet/2-outlet and 2-inlet/2-outlet systems. This study yeilds that phase difference between the inlet ports can significantly increase the transmission loss in low frequency range.

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A Study on the Noise Produced by Unsteady Exhaust Efflux of Engine (기관의 비정상 배기배출에 의해 생성되는 소음에 관한 연구)

  • 이민호;박명규
    • Journal of the Korean Society of Safety
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    • v.12 no.4
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    • pp.191-200
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    • 1997
  • This paper discusses prediction of the sound pressure level produced by simple engine exhaust systems(plain pipe, plain expansion chamber pipe, plain expansion chamber with internally extended inlet and outlet pipe, perforated pipe enclosed in a plain expansion chamber) and a computer program has been developed which predicts the sound pressure level and the frequency spectrum. The program utilizes unsteady flow gas dynamic theory and acoustic theory to predict the pressure-time history in the exhaust system and the mass flow rate-time history at the open end of the system and the sound pressure levels(1/3 Octave band levels) and the frequency spectrum in semi-anechoic room. The predictions are compared with measured levels and show a high degree of correlation.

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