Research Papers

Modeling perforates in mufflers using two-ports

[+] Author and Article Information
T. Elnady

ASU Sound & Vibration Laboratory, Faculty of Engineering, Ain Shams University, 1 Elsarayat Street, Abbaseya, 11517 Cairo, Egypttamer@asugards.net

M. Åbom

The Marcus Wallenberg Laboratory for Sound and Vibration Research, AVE, KTH, SE-10044 Stockholm, Sweden

S. Allam

Department of Automotive Technology, Faculty of Industrial Education, Helwan University, Elsawah Street-Elkoba, 11282 Cairo, Egypt

J. Vib. Acoust 132(6), 061010 (Oct 08, 2010) (11 pages) doi:10.1115/1.4001510 History: Received July 06, 2009; Revised March 04, 2010; Published October 08, 2010; Online October 08, 2010

One of the main sources of noise of a vehicle is the engine where its noise is usually damped by means of acoustic mufflers. A very common problem in the modeling of automotive mufflers is that of two flow ducts coupled through a perforate. A new segmentation approach is developed here based on two-port analysis techniques, in order to model perforated pipes using general two-port codes, which are widely available. Examples are given for simple muffler configurations and the convergence of the technique is investigated based on the number of segments used. The results are compared with closed form solutions form the literature. Finally, an analysis of a complicated multichamber perforated muffler system is presented. The two-port simulation results show good agreement with both the measurements, and the simulations using the classical four-port elements.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

A segment of the perforated wall

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Figure 2

The representation of a two-port element relating two pairs of state variables (p and U)

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Figure 3

Location of the lumped elements. Note: A lumped element is put at the beginning and end. From the figure, it follows that Δx=L/(N−1), where N is the number of lumped elements.

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Figure 4

The resonator muffler test case

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Figure 5

Different networks for different cases

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Figure 6

Convergence analysis for the test case (long resonator). d1=57, d2=144, and L=144 mm.

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Figure 7

Convergence analysis for the short resonator. d1=50, d2=75, and L=65 mm.

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Figure 8

Sketch of the muffler internal scheme (dimensions are in mm). The encircled numbers refer to the inlet/outlet pipe (1–2), the four baffles (3–6) and the sleeve (7).

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Figure 9

A detailed drawing of the perforated baffle 3 (50 holes)

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Figure 10

A detailed drawing of the perforated baffles 4 and 5 (72 holes)

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Figure 11

A detailed drawing of the perforated baffle 6 (42 holes)

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Figure 12

Flow resistances inside the muffler considered as 1D flow network. The pressure drop or flow loss across each resistance is Δp=RQ|Q|, where Q is the volume flow.

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Figure 13

The equivalent electric circuit

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Figure 14

The breakdown of the muffler into a network of two- and four-ports

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Figure 15

The simplified muffler network, with positive flow directions defined

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Figure 16

The muffler network model in SIDLAB . The circuit symbols are defined in Fig. 1 and Table 1

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Figure 17

Comparison between the two simulations without flow

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Figure 18

Comparison between the two simulations at Mach 0.15

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Figure 19

Comparison with the FEM simulations without flow

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Figure 20

Comparison with the FEM simulations at Mach 0.15




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