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In an open cycle traveling wave thermoacoustic engine, the hot heat exchanger is replaced by a steady flow of hot gas into the regenerator to provide the thermal energy input to the engine. The steady-state operation of such a device requires that a potentially large mean temperature difference exist between the incoming gas and the solid material at the regenerator's hot side, due in part to isentropic gas oscillations in the open space adjacent to the regenerator. The magnitude of this temperature difference will have a significant effect on the efficiencies of these open cycle devices. To help assess the feasibility of such thermoacoustic engines, a numerical model is developed that predicts the dependence of the mean temperature difference upon the important design and operating parameters of the open cycle thermoacoustic engine, including the acoustic pressure, mean mass flow rate, acoustic phase angles, and conductive heat loss. Using this model, it is also shown that the temperature difference at the regenerator interface is approximately proportional to the sum of the acoustic power output and the conductive heat loss at this location. 相似文献
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A model to modulate acoustic field in a regenerator of a thermoacoustic system by the double loudspeakers method is presented in this paper. The equations are derived for acoustic field modulation. They represent the relations among acoustic field (complex pressure p(0), complex velocity u(0), and acoustic impedance Z(0)), driving parameters of loudspeakers (voltage amplitude and its phase difference), and operating parameters involved in a matrix H (frequency, temperature of regenerator). The range of acoustic field is adjustable and limited by the maximal driving voltages of loudspeakers according to driving parameters. The range is simulated and analyzed in the amplitude-phase and complex coordinate planes for a given or variable H. The simulated results indicate that the range has its intrinsic characteristics. The expected acoustic field in a regenerator can be obtained feasibly by the modulation. 相似文献
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回热器的热声直流模型及其效应研究 总被引:2,自引:0,他引:2
本文由基本的守恒方程出发,获得了能描述回热器存在声直流时的非线性动力学模型及由此而导致的非线性时均热力学效应。根据所得到的模型,考察了声直流对临界声功产生率温度梯度、回热器温度分布以及脉冲管制冷性能的影响。 相似文献
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In a previous paper the authors have shown how it is possible to compute the acoustic pressure due to an axi-symmetric radiator with different boundary conditions. The technique involves the conversion of a double integral to a single integral by means of a geometric transform, and may be applied with the Green's function appropriate to each boundary condition.The present work shows how the form of the single integrals makes it possible to derive and compute both the particle velocity and the wave intensity. It has become apparent that the particle velocity must be described as an elliptic vector. A new concept, the ‘diffraction front’, has been defined as a surface in which there is no net energy transfer, and this has been applied to the evaluation of the magnitude and direction of energy flow. Plots have been made of flow lines and diffraction fronts, and also three-dimensional representations of energy intensity have been made for those acoustic fields in which pressure has already been evaluated. 相似文献
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《Heat Recovery Systems and CHP》1990,10(3):187-211
In the present study a number of expressions determining the irreversible entropy generation in a rotary regenerator are presented. Adding to them formulae: (i) concerning the efficiency of a steam power plant, (ii) describing heat transfer and the pressure losses in a rotary heat exchanger, a computational model has been obtained in order to show how these irreversibilities and the efficiency of a steam power plant depend on the design parameters of a rotary regenerator. Here it was useful to assume an air cycle i-s for flue gas in a steam boiler. The numerical results are presented mainly in graph form making it possible to show the results obtained clearly and to easily draw some conclusions. By first, varying the values of the rotary regenerator matrix height, distribution factor of regenerator flow area on the hot and cold sides, total leakage factor, distribution factor of total leakage on the hot and cold ends and density of gas mass rates flowing through each side of the regenerator, the dependence of the entropy generation rates on the above parameter values is demonstrated. The direct effects of changes in values of the above parameters on a normalized energy measure or irreversibilities and the efficiency of a steam power plant are then evaluated. Having these results presented in juxtaposition, some general and practical conclusions are formulated. 相似文献
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The Acoustic Energy Flow Boundary Element Method (AEFBEM) is developed to predict the acoustic energy density and intensity of an engineering system. Up to now, the acoustic energy flow model has been used only for analysis of high frequencies or radiation noise because of plane wave and far-field assumptions. In this research, a new energy flow governing equation that can consider the near field acoustic energy term and spherical wave characteristics is derived successfully to predict the acoustic energy density and intensity of a system in the medium-to-high frequency range. A near field term of acoustic energy in spherical coordinate is added to the relationship between energy density and energy flow. But with the far-field assumption, this term vanishes, so the relationship between energy density and energy flow becomes the same as that of the plane wave. By considering the near field energy term without far-field assumption, the energy density at medium frequencies can be estimated. However, the governing equation has to be numerically manipulated for use in the analysis of complex structures; therefore, the Boundary Element Method (BEM) is implemented. AEFBEM is a numerical analysis method formulated by applying the boundary element method to an acoustic energy flow governing equation. It is very powerful in predicting the acoustic energy density and intensity of complex structures in medium-to-high frequency ranges, and can analyze interior noise and radiating sound. To verify its validity, several numerical results are provided. BEM and AEFBEM were compared with respect to energy density, and the results from both methods were similar. 相似文献
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Aramini R Caviglia G Piana M 《The Journal of the Acoustical Society of America》2012,131(4):2866-2872
In time-harmonic acoustic fields, energy streamlines are defined as the integral curves of the power-flux density vector, averaged over a period. They provide a tool to visualize the details of propagation of energy. After reviewing the role of energy streamlines in the linear sampling method for acoustic inverse scattering, this work formulates a physical interpretation of the same qualitative method in the case of an isotropic homogeneous solid matrix. Specifically, it is shown that the linear sampling method results from conservation of energy along streamline tubes of energy flow associated with elastic waves. 相似文献
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Chappell DJ Giani S Tanner G 《The Journal of the Acoustical Society of America》2011,130(3):1420-1429
Standard methods for describing the intensity distribution of mechanical and acoustic wave fields in the high frequency asymptotic limit are often based on flow transport equations. Common techniques are statistical energy analysis, employed mostly in the context of vibro-acoustics, and ray tracing, a popular tool in architectural acoustics. Dynamical energy analysis makes it possible to interpolate between standard statistical energy analysis and full ray tracing, containing both of these methods as limiting cases. In this work a version of dynamical energy analysis based on a Chebyshev basis expansion of the Perron-Frobenius operator governing the ray dynamics is introduced. It is shown that the technique can efficiently deal with multi-component systems overcoming typical geometrical limitations present in statistical energy analysis. Results are compared with state-of-the-art hp-adaptive discontinuous Galerkin finite element simulations. 相似文献
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This work presents an application of principle velocity patterns in the analysis of the structural acoustic design optimization of an eight ply composite cylindrical shell. The approach consists of performing structural acoustic optimizations of a composite cylindrical shell subject to external harmonic monopole excitation. The ply angles are used as the design variables in the optimization. The results of the ply angle design variable formulation are interpreted using the singular value decomposition of the interior acoustic potential energy. The decomposition of the acoustic potential energy provides surface velocity patterns associated with lower levels of interior noise. These surface velocity patterns are shown to correspond to those from the structural acoustic optimization results. Thus, it is demonstrated that the capacity to design multi-ply composite cylinders for quiet interiors is determined by how well the cylinder be can designed to exhibit particular surface velocity patterns associated with lower noise levels. 相似文献
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Acoustic energy in non-uniform flows 总被引:1,自引:0,他引:1
The concept of acoustic energy is extended to non-uniform fluid flows. In general, the resulting energy balance equation exhibits acoustic energy production or dissipation within the flow, but in an important special case the production term is zero, implying conservation of acoustic energy. The acoustic energy equations used in classical and geometric acoustics are recovered from the general formulation by making the appropriate assumptions. 相似文献
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A model is developed for thermoacoustic devices that have neither stack nor regenerator. These "no-stack" devices have heat exchangers placed close together in an acoustic standing wave of sufficient amplitude to allow individual parcels of gas to enter both exchangers. The assumption of perfect heat transfer in the exchangers facilitates the construction of a simple model similar to the "moving parcel picture" that is used as a first approach to stack-based engines and refrigerators. The model no-stack cycle is shown to have potentially greater inviscid efficiency than a comparable stack model. However, losses from flow through the heat exchangers and on the walls of the enclosure are greater than those in a stack-based device due to the increased acoustic pressure amplitude. Estimates of these losses in refrigerators are used to compare the possible efficiencies of real refrigerators made with or without a stack. The model predicts that no-stack refrigerators can exceed stack-based refrigerators in efficiency, but only for particular enclosure geometries. 相似文献