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Research Papers

Flow and Pressure Drop Calculation Using Two-Ports

[+] Author and Article Information
T. Elnady

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

S. Elsaadany

ASU Sound and Vibration Laboratory, Faculty of Engineering, Ain Shams University, 1 Elsarayat Street, Abbaseya, Cairo 11517, Egypt

M. Åbom

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

J. Vib. Acoust 133(4), 041016 (Apr 12, 2011) (8 pages) doi:10.1115/1.4003593 History: Received May 27, 2010; Revised December 21, 2010; Published April 12, 2011; Online April 12, 2011

Exhaust systems should be carefully designed for different applications. The main objective of an exhaust system is to reduce the engine noise. Maximum noise reduction is usually desired to the limit of a certain backpressure, which is set by the engine manufacturer in order not to deteriorate the engine efficiency. Therefore, a parallel calculation of the flow and pressure drop must be performed. The amount of flow flowing through each element will also affect its acoustic properties. Usually, acoustic and flow calculations are done separately on two different software. This paper describes a new technique that enables both calculations to be done using the same input data on the same platform. Acoustic calculations are usually performed in the frequency domain in the plane wave region using the two-port theory and then the acoustic pressure in the system is solved for using well-known algorithms to handle arbitrary connected two-ports. The stagnation pressure and volume flow can also be calculated using the same algorithm by deriving a flow two-port for each element using the stagnation pressure and the volume flow velocity as the state variables. The proposed theory is first discussed listing the flow matrices for common elements in exhaust elements, and then different systems are analyzed and compared with the measurements.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

A flow network model of a duct system. The network consists of five two-ports and four nodes (●). The network symbols used are defined in the next subsection. The arrows describe an assumed flow direction over the network.

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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 16

Case 3: Pressure-flow curve of the after treatment device

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Figure 7

Case 1: Schematic diagram of the through flow muffler

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Figure 8

Case 1: SIDLAB network of the through flow muffler

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Figure 9

Case 1: Pressure-flow curve of the through flow muffler

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Figure 10

Case 2: Schematic diagram of the plug-flow muffler

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Figure 11

Case 2: SIDLAB network of the plug-flow muffler

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Figure 12

Case 2: Pressure-flow curve of the plug-flow muffler—porosity of 7%

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Figure 13

Case 2: Pressure-flow curve of the plug-flow muffler—porosity of 28%

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Figure 14

Case 3: Schematic diagram of the after treatment device

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Figure 15

Case 3: SIDLAB network of the after treatment device

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Figure 3

Circuit representation of a one-port assuming a constant pressure source. pn is the total pressure in node n

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Figure 4

An example of a perforated tube configuration and the associated two-port network

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