Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Investigation and Optimization of the Acoustic Performance of Exhaust Systems
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

There is a strong competition among automotive manufacturers to reduce the radiated noise levels. One important source is the engine exhaust where the main noise control strategy is by using efficient mufflers. Stricter vehicle noise regulations combined with various exhaust gas cleaning devices, removing space for traditional mufflers, are also creating new challenges. Thus, it is crucial to have efficient models and tools to design vehicle exhaust systems. In addition the need to reduce CO2 emissions puts requirements on the losses and pressure drop in exhaust systems. In this thesis a number of problems relevant for the design of modern exhaust systems for vehicles are addressed. First the modelling of perforated mufflers is investigated. Fifteen different configurations were modeled and compared to measurements using 1D models. The limitations of using 1D models due to 3D or non-plane wave effects are investigated. It is found that for all the cases investigated the 1D model is valid at least up to half the plane wave region. But with flow present, i.e., as in the real application the 3D effects are much less important and then normally a 1D model works well. Another interesting area that is investigated is the acoustic performance of after treatment devices. Diesel engines produce harmful exhaust emissions and high exhaust noise levels. One way of mitigating both exhaust emissions and noise is via the use of after treatment devices such as Catalytic Converters (CC), Selective Catalytic Reducers (SCR), Diesel Oxidation Catalysts (DOC), and Diesel Particulate Filters (DPF). The objective of this investigation is to characterize and simulate the acoustic performance of different types of filters so that maximum benefit can be achieved. A number of after treatment device configurations for trucks were selected and investigated.

Finally, addressing the muffler design constraints, i.e., concerning space and pressure drop, a muffler optimization problem is formulated achieving the optimum muffler design through calculating the acoustic properties using an optimization technique. A shape optimization approach is presented for different muffler configurations, and the acoustic results are compared against optimum designs from the literature obtained using different optimization methods as well as design targets.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , iv, 18 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2012:31
Keyword [en]
Exhaust systems, noise, pressure drop, 1D models, perforated mufflers, after treatment devices, optimization
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-103595OAI: oai:DiVA.org:kth-103595DiVA: diva2:560822
Presentation
2012-10-14, Faculty of Engineering, Ain Shams university, Kairo, Egypt, 09:15 (English)
Opponent
Supervisors
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Note

QC 20121016

Available from: 2012-10-16 Created: 2012-10-16 Last updated: 2013-04-11Bibliographically approved
List of papers
1. Investigation into modeling of multi-perforated mufflers
Open this publication in new window or tab >>Investigation into modeling of multi-perforated mufflers
2009 (English)Conference paper, Published paper (Other academic)
Abstract [en]

There is a strong competition among automotive manufacturers to reduce the radiated noise levels. One main source is the engine where the main noise control strategy is by using efficient mufflers. Resistive mufflers are now widely used to attenuate IC-Engine noise due to its better performance over the reactive ones. Resistive damping can be achieved either by using absorbing material or perforates in the form of tubes or sheets. Perforates mufflers have an increased performance with flow when the acoustic impedance is increased by introducing flow through the perforate holes. On the other hand, perforates can deteriorate the engine performance, if badly designed, by increasing the flow back pressure. Modeling of perforated mufflers started in the seventies when simple geometries were used. There were two approaches to analyze two tubes connected with a perforate (i.e. four-port), segmentation and distributed. Both approaches were limited to a few specified geometries. Recently, the authors published a new technique based on the segmentation approach where four ports can be replaced by a number of two-ports so that it can be used in general two-port codes. This paper investigates the use of these techniques in modeling complex perforated muffler geometries. Fifteen different configurations were modeled and compared to measurements. There are some limitations to the use of these models in some configurations because of strong 3D effects that limits the validity of these models to almost half the plane wave region. These configurations are mainly the double plug flow muffler and the parallel tube mufflers.

National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-103695 (URN)2-s2.0-84871465187 (Scopus ID)
Conference
16th International Congress of Sound and Vibration, Krakow (2009)
Note

QC 20121018

Available from: 2012-10-18 Created: 2012-10-18 Last updated: 2012-10-18Bibliographically approved
2. Investigation of the Acoustic Performance of After Treatment Devices
Open this publication in new window or tab >>Investigation of the Acoustic Performance of After Treatment Devices
2011 (English)In: SAE International Journal of Passenger Cars - Mechanical Systems, ISSN 1946-3995, Vol. 4, no 2, 1068-1075 p.Article in journal (Refereed) Published
Abstract [en]

Diesel engines produce harmful exhaust emissions and high exhaust noise levels. One way of mitigating both exhaust emissions and noise is via the use of after treatment devices such as Catalytic Converters (CC), Selective Catalytic Reducers (SCR), Diesel Oxidation Catalysts (DOC), and Diesel Particulate Filters (DPF). The objective of this investigation is to characterize and simulate the acoustic performance of different types of filters so that maximum benefit can be achieved. A number of after treatment device configurations for trucks were selected and measured. A measurement campaign was conducted to characterize the two-port transfer matrix of these devices. The simulation was performed using the two-port theory where the two-port models are limited to the plane wave range in the filter cavity. These models are implemented in SIDLAB Software for the simulation of low frequency sound propagation in ducts, and SIDLAB was used to predict the transfer matrix of the tested configurations. This paper presents guidelines for dividing these complicated systems into a number of simple 1D elements. Specifically, strategies for modeling the side inlet and outlet end caps are documented. The model takes about 15 minutes to set-up and 15 seconds to solve which demonstrates the power of using two-port techniques in modeling exhaust systems. The comparisons show good agreement between the measured and simulated transmission loss in the plane wave region.

Keyword
Acoustic performance, After treatment devices, Complicated systems, Diesel oxidation catalyst, Diesel particulate filters, Exhaust emission, Exhaust noise, Low-frequency sounds, Measurement campaign, Plane wave, Transfer matrixes, Transmission loss, Two-port models
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-103696 (URN)10.4271/2011-01-1562 (DOI)2-s2.0-84859310639 (Scopus ID)
Note

QC 20121018

Available from: 2012-10-18 Created: 2012-10-18 Last updated: 2014-04-14Bibliographically approved
3. Insight into exhaust systems optimization techniques
Open this publication in new window or tab >>Insight into exhaust systems optimization techniques
2010 (English)Conference paper, Published paper (Other academic)
Abstract [en]

Exhaust system mufflers should be carefully designed for different applications. The main objective of an exhaust system is to reduce the engine noise. Maximum acoustic performance is usually desired under the limit of space constraints. Therefore obtaining the muffler optimum design is very crucial. In this paper, the muffler optimization problem is formulated allowing getting the optimum muffler design through calculating the acoustic properties conjugated with the optimization technique using a function "fmincon" from the MATLAB optimization tool-box that finds the minimum of a constrained nonlinear multivariable function. There are several possibilities to evaluate the acoustic performance of a muffler such as the sound transmission loss, the insertion loss, and the acoustic pressure measured by a receiver outside the exhaust system opening. By selecting one of these design targets, the optimum design of a specific muffler configuration in the frequency range of interest can be obtained. In this paper, a shape optimization approach is presented for different mufflers configurations, and the results of transmission loss, insertion loss, and the outside acoustic pressure are compared against optimum designs from the literature obtained using different optimization methods as well as design targets.

National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-103697 (URN)2-s2.0-84871449120 (Scopus ID)
Conference
17th International Congress of Sound and Vibration, Cairo (2010)
Note

QC 20121018

Available from: 2012-10-18 Created: 2012-10-18 Last updated: 2016-09-20Bibliographically approved
4. Optimization of exhaust systems to meet the acoustic regulations and the enginespecifications
Open this publication in new window or tab >>Optimization of exhaust systems to meet the acoustic regulations and the enginespecifications
2011 (English)Conference paper, Published paper (Other academic)
Abstract [en]

Mufflers for internal combustion engines should be carefully designed. The main objective of a muffler is to reduce the engine noise while maintaining the back pressure below a certain limit. A specific target acoustic performance has to be met under space constraints and allowable engine back pressure limit. Usually, the insertion loss of the exhaust system is required to satisfy a certain target performance curve. The insertion loss is most appropriate to describe the exhaust system acoustic performance since it is dependent on the engine acoustic impedance, which varies with the engine loading and rotational speed. In this paper, a muffler optimization problem is formulated so that several shape parameters are optimized under some space constraints with flow. Any combination of linear space constraints can be imposed. The allowable engine back pressure is introduced as a non-linear constraint so that the optimum shape design will meet the engine back pressure specifications. The interior point optimization algorithm, which is available as a built-in MATLAB function "fmincon", is used in this paper. The formulated problem is applied to a real case study, where a truck exhau stsystem consists of a diesel engine, two mufflers, intermediate pipes, and a tailpipe. The first muffler is a typical EU-regulation compliant. The dimensions and location of the second muffler are to be optimized. A limit for the system back pressure is imposed by the engine manufacturer. An optimum design was investigated for different engine speeds and loadings. It was found that using the suggested formulation in this paper; one can obtain an applicable design of a muffler to meet both the acoustic regulations and the engine specifications.

National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-103698 (URN)2-s2.0-84871490374 (Scopus ID)
Conference
18th International Congressof Sound and Vibration, Rio De Janeiro (2011)
Note

QC 20121018

Available from: 2012-10-18 Created: 2012-10-18 Last updated: 2016-09-20Bibliographically approved

Open Access in DiVA

fulltext(714 kB)3474 downloads
File information
File name FULLTEXT01.pdfFile size 714 kBChecksum SHA-512
2257e3e7a09590c8781da791b491fc67dde9eabf9d2901234d130a11744549b62c5b2827ce1b14dc9f575ee232b63a32609bbbfcadd705f5c66c2b1d33e9f410
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Elsaadany, Sara
By organisation
Marcus Wallenberg Laboratory MWL
Fluid Mechanics and Acoustics

Search outside of DiVA

GoogleGoogle Scholar
Total: 3474 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

urn-nbn

Altmetric score

urn-nbn
Total: 438 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf