Acoustic characteristics of annular cavities with locally non-uniform media

Choi, Hyun-Ki; Yoo, Sung Woo; Jeong, Ji Deok; Lee, Jang Moo

doi:10.1016/s0022-460x(02)01383-4

Cited by 4 publications

(3 citation statements)

References 11 publications

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“…Chen et al [29] put forward a new calculation method combining the Helmholtz internal integral equation to study the acoustic characteristics of circular and rectangular acoustic cavities. Choi et al [30] proposed a theoretical method for studying natural frequencies and modal shapes of the annular cavity in local heterogeneous media. By solving the homogeneous wave equation in the elliptical cylindrical coordinate system, Hong and Kim [31] obtained the analytical solution of natural frequencies and mode shapes of elliptical cylinder acoustic cavities.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Acoustic Characteristics of Arbitrary Triangular Prism and Quadrangular Prism Acoustic Cavities

Shi

Zhang

2019

Shock and Vibration

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This paper proposes a method for the analysis of acoustic modals and steady-state responses of arbitrary triangular prism and quadrangular prism acoustic cavities based on the three-dimensional improved Fourier series. First, the geometric models of arbitrary triangular prism and quadrangular prism acoustic cavities are established. To facilitate the calculation, the bottom and top surfaces of the irregular cavity are converted into the unit square domain by a coordinate transformation. Internal sound pressure-admissible functions are constructed, and energy expressions are derived after coordinate transformation based on the three-dimensional improved Fourier series. The acoustic modals of arbitrary triangular prism and quadrangular prism acoustic cavities are obtained by the Rayleigh–Ritz technique. At the same time, a point sound source excitation is introduced into the cavity to further study the steady-state responses of prismatic acoustic cavities with different acoustic impedance boundary conditions. The reliability and universality of the method are verified by comparing with the finite element results. The method and results can provide some references and benchmarks for future research and application.

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Section: Introductionmentioning

confidence: 99%

Analysis of Acoustic Characteristics of Arbitrary Triangular Prism and Quadrangular Prism Acoustic Cavities

Shi

Zhang

2019

Shock and Vibration

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“…This will make the acoustic behavior more complex and increase the acoustic modal density. The finite element technique applied in this thesis can nevertheless include these effects [16].…”

Section: Annular Combustorsmentioning

confidence: 99%

“…The relation between heat release and temperature is then given by: dq = c v dT , (B. 16) in which c v is the specific heat at constant volume. Using the equation of state for an ideal gas, the partial derivative can be written as:…”

Section: B2 Unsteady Heat Release Rate As Sourcementioning

confidence: 99%

Acousto-elastic interaction in combustion chambers

Huls¹

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The subject of the Desire project is the combustion chamber, as depicted in figure 1.2. One of the combustion chamber designs currently used in gas turbines is the so-called annular combustor (figure 1.3). In this design the combustion chamber is shaped as an annulus in which multiple burners (for instance 24) cause multiple swirling flames. It is very expensive to build a full annulus as a test rig, and therefore one section, containing one burner, is taken from the annulus. The interaction between flames from different burners is Combustion, acoustics and vibrationThis section introduces the basic phenomenology, which is schematically depicted in figure 1.4, starting with the flame. The most characteristic influence of the flame is that it generates a temperature field (1), which strongly influences the acoustics of the system. This is mostly a static influence. The steady state temperature field created by the flame determines the steady state temperature field for the acoustics of the system. Unsteady combustion can give time-dependent temperature differences. When the flame moves, the local temperature field in the flame zone changes, but these perturbations have no global influence. When the amount of fuel that comes to the flame changes, the temperature of the total flame changes. These perturbations propagate through the combustion chamber with the flow velocity and are called entropy waves [78]. These are not taken into account in this thesis. Besides the steady influence, the flame also has unsteady components. Because the combustion is turbulent, the combustion speed constantly changes around the mean value. These changes generate an acoustic volume source (2), which gives an acoustic field in the combustor (this is commonly called combustion roar ). This acoustic field in turn generates perturbations in the fuel and air flow to the burner and to the mixture coming to the flame (3), which again generates perturbations in the speed of combustion. This loop can become unstable, which is known as a combustion instability. This behavior is studied extensively in the literature [23,62,69]. Another well-known example of an unstable feedback loop between heat and acoustics is the so-called Rijke tube [82].Vibration of the structure is influenced directly by the flame through the temperature field (1). This is again a steady phenomenon, the steady flame determines the temperature of the liner and therefore its material properties. Changes in operating conditions cause changes in thermal expansion of components and therefore cyclic thermal stresses, which can directly lead to relatively low cycle fatigue [95]. The interaction between acoustics and vibration is similar to that between combustion and acoustics. The acoustic field acts as a pressure load on the structure (4), which vibrates in response. This vibration imposes a velocity boundary condition on the acoustic domain (5), which generates an acoustic field. This loop does not become unstable, because there Table A.1: Coefficients of the c p polynomial, g...

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