A method for modeling perforated tube muffler components. II. Applications

Abstract

This paper is the second of two papers describing a method for modeling muffler components having perforated flow tubes, as for example those found frequently in automotive applications. In the first paper the theoretical model was developed, whereas here the theory is applied to demostrate specifically the utility and potential of the model. The applications are idealized in the sense that effects which occur simultaneously in perforated-tube mufflers are treated separately. These effects are (1) the nonlinear impedance of the perforation due to finite amplitude sound pressure, and (2) the change in impedance of the perforation with mean flow. The first effect is demonstrated with a straight through resonator, and the second with a cross-flow chamber. Predicted results for transmission loss in both cases compared quite well with measurements. Crucial to the success of the modeling was a proper description of the perforate impedance. The confidence instilled by the results prompted an inquiry into the nature of the two muffler components. It was determined by modeling that, contrary to popular opinion, these devices can be very dissipative, even though they contain no recognizable dissipative materials. The controlling mechanism is the high resistivity of the perforation induced by the acoustic/flow environment.

Muffler modeling by transfer matrix method and experimental verification

“…When using perforate tube elements, the transfer matrices depend on the porosity (number of perforations per unit length of pipe axis) and particularly on the normalized partition impedance of the perforate. This impedance can be evaluated by means of empirical expressions given for different flow conditions, such as stationary medium (Sullivan and Crocker, 1978), perforates with cross-flow (Sullivan, 1979), and perforates with grazing flow (Rao and Munjal, 1986).…”

Acoustic Attenuation Performance of Perforated Tube Silencer Based on Computational Fluid Dynamics Results

“…。为了研究温度与气体流动对传递损失的影 响，多年来，国内外学者作了大量的理论与试验工 作 [5][6][7][8] 。近年来随着高性能计算机的快速发展，仿真 软件在声学计算中得到了广泛的应用 [9][10][11][12][13] 。刘晨 等 [14] 使用 GT-POWER 软件分别计算了无气体流动 和有高温气体流动(400 ℃)时消声器的传递损失， 并通过试验进行了验证。董红亮等 [15] 将温度场求解 机 械 工 程 学 报 第 53 卷第 1 期期 80 结果中温度相近(±5 ℃)的单元定义为一个集合，并 应用 SYSNOISE 软件把对应温度下的空气参数赋 给该集合，研究温度对传递损失的影响。 文献 [14][15] …”

Contribución al modelado acústico de la línea de escape en motores de combustión. Aplicación a silenciadores y catalizadores

“…El primer caso, que es el más simple, corresponde a la situación de un elemento perforado en el seno de un medio de propagación en reposo. En las referencias [133,135] puede encontrarse la expresión…”

“…Sullivan [133], basándose en el modelo empírico de Garrison, modificó su modelo de impedancia sin flujo (2.115) para incluir el efecto de la velocidad normal en la componente resistiva. Este efecto es similar al de un conducto perforado cerrado en un extremo donde el flujo es forzado a salir a través de los orificios y la velocidad presenta dos componentes: una componente tangente a la superficie, de valor máximo a la entrada y nula a la salida, y una componente normal o transversalŪ 0 considerada uniforme [40,133] …”

“…Este efecto es similar al de un conducto perforado cerrado en un extremo donde el flujo es forzado a salir a través de los orificios y la velocidad presenta dos componentes: una componente tangente a la superficie, de valor máximo a la entrada y nula a la salida, y una componente normal o transversalŪ 0 considerada uniforme [40,133] …”