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Na, Wei, PHD studentORCID iD iconorcid.org/0000-0001-5757-3668
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Publikationer (3 of 3) Visa alla publikationer
Na, W., Boij, S. & Efraimsson, G. (2016). Acoustic characterization of a hybrid liner consisting of porous material by using a unified linearized navier-stokes approach. In: 22nd AIAA/CEAS Aeroacoustics Conference, 2016: . Paper presented at 22nd AIAA/CEAS Aeroacoustics Conference, 2016, 30 May 2016 through 1 June 2016. American Institute of Aeronautics and Astronautics
Öppna denna publikation i ny flik eller fönster >>Acoustic characterization of a hybrid liner consisting of porous material by using a unified linearized navier-stokes approach
2016 (Engelska)Ingår i: 22nd AIAA/CEAS Aeroacoustics Conference, 2016, American Institute of Aeronautics and Astronautics, 2016Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

In this paper, the acoustic properties of a hybrid liner placed at the end of an impedance tube are investigated using numerical simulations. The hybrid liner constitutes of three components, a perforated plate, a porous layer and a rectangular back cavity. The presence of the porous layer is to enhance the absorptive performance of a liner. The main objective of the paper is to verify the proposed numerical methodology - a unified linearized Navier-Stokes Equations (LNSE) approach. In the unified LNSE approach, the combination of the Helmholtz Equation, LNSE as well as the equivalent fluid model are solved in different regions of the impedance tube. To achieve this, the continuity of the coupling condition between the LNSE and the Helmholtz equation is examined. Another objective is to analyze the effectiveness of the porous material to the acoustic performance of the liner. Acoustic liner simulations with and without porous material, porous material with different flow resistivity are carried out. A good agreement is found between the numerical results and the measurements previously performed at KTH MWL.1 Compared to previous work234, several improvements have been made in the numerical methodology, such as that the energy equation has been added in order to include the damping due to viscous dissipation as well as the thermal dissipation in the vicinity of the perforated plate.

Ort, förlag, år, upplaga, sidor
American Institute of Aeronautics and Astronautics, 2016
Nyckelord
Acoustic impedance, Acoustic properties, Aeroacoustics, Characterization, Helmholtz equation, Linearization, Numerical methods, Oil well casings, Perforated plates, Porous materials, Viscous flow, Acoustic characterization, Acoustic performance, Coupling condition, Linearized Navier-Stokes, Linearized navier-stokes equations, Numerical methodologies, Thermal dissipation, Viscous dissipation, Navier Stokes equations
Nationell ämneskategori
Maskinteknik
Identifikatorer
urn:nbn:se:kth:diva-194621 (URN)10.2514/6.2016-2980 (DOI)2-s2.0-84982871151 (Scopus ID)978-1-62410-386-5 (ISBN)
Konferens
22nd AIAA/CEAS Aeroacoustics Conference, 2016, 30 May 2016 through 1 June 2016
Anmärkning

Conference Paper. QC 20161101

Tillgänglig från: 2016-11-01 Skapad: 2016-10-31 Senast uppdaterad: 2019-03-19Bibliografiskt granskad
Na, W., Efraimsson, G. & Boij, S. (2016). Numerical prediction of thermoacoustic instabilities with a V-Flame. In: 23rd International Congress on Sound and Vibration 2016 (ICSV 23), Athens, Greece 10-14 July 2016, Volume 1 of 6: From Ancient to Modern Acoustics. Paper presented at 23rd International Congress on Sound and Vibration 2016 (ICSV 23), Athens, Greece 10-14 July 2016. International Institute of Acoustics and Vibrations, 1
Öppna denna publikation i ny flik eller fönster >>Numerical prediction of thermoacoustic instabilities with a V-Flame
2016 (Engelska)Ingår i: 23rd International Congress on Sound and Vibration 2016 (ICSV 23), Athens, Greece 10-14 July 2016, Volume 1 of 6: From Ancient to Modern Acoustics, International Institute of Acoustics and Vibrations , 2016, Vol. 1Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

In this paper, results from a numerical solver for the Helmholtz equation using the Finite Element Method (FEM) for predicting thermoacoustic instabilities are presented. The one-dimensional n-τ flame model, which is governed by an interaction index n and a time-delay τ as well as a Flame transfer function (FTF) is used for flame source term. We show results for the validation of the numerical solver for the Rijke tube benchmark case with the variation of n and τ in the one-dimensional n-τ model. Thereafter, thermoacoustic instabilities for a V-flame are predicted, for a typical configuration of a dump combustor - a tube with an area expansion. This is a more realistic test case, since a bluff-body flame holder is often used in combustors, where a V-flame will be generated and anchored to the rod. Usually, the V-flame is more susceptible to thermoacoustic instabilities. In the paper, the eigenfrequencies, as well as the acoustic pressure perturbations are presented as numerical results.

Ort, förlag, år, upplaga, sidor
International Institute of Acoustics and Vibrations, 2016
Nyckelord
Acoustics, Combustors, Numerical methods, Thermoacoustics, Time delay, Acoustic pressures, Eigen frequencies, Flame transfer functions, Interaction index, Numerical predictions, Numerical results, Numerical solvers, Thermoacoustic instability, Finite element method
Nationell ämneskategori
Strömningsmekanik och akustik
Identifikatorer
urn:nbn:se:kth:diva-195437 (URN)2-s2.0-84987864236 (Scopus ID)978-1-5108-2716-5 (ISBN)
Konferens
23rd International Congress on Sound and Vibration 2016 (ICSV 23), Athens, Greece 10-14 July 2016
Anmärkning

Funding Details: FP7-PEOPLE-ITN-2012, EC, European Commission

QC 20161128

Tillgänglig från: 2016-11-28 Skapad: 2016-11-03 Senast uppdaterad: 2019-02-28Bibliografiskt granskad
Na, W. (2015). Frequency Domain Linearized Navier-Stokes Equations Methodology for Aero-Acoustic and Thermoacoustic Simulations. (Licentiate dissertation). Stockholm: KTH Royal Institute of Technology
Öppna denna publikation i ny flik eller fönster >>Frequency Domain Linearized Navier-Stokes Equations Methodology for Aero-Acoustic and Thermoacoustic Simulations
2015 (Engelska)Licentiatavhandling, monografi (Övrigt vetenskapligt)
Abstract [en]

The first part of the thesis focuses on developing a numerical methodology to simulate the acoustic properties of a hybrid liner consisting of a perforated plate, a porous layer and a Helmholtz cavity. Liners are always a standard way to reduce noise in today’s aeroengines, e.g. the fan noise can be reduced effectively through the installation of acoustic liners as wall treatments in the ducts. In order to optimize a liner in the design phase, an accurate and efficient prediction tool is of interests. Hence, a unified Linearized Navier-Stokes equations(LNSE) approach has been implemented in the thesis, combining the LNSE in frequency domain with the fluid equivalent model. The LNSE is applied in the vicinity of the perforated plate to simulate sound propagation including viscous damping effect, and the fluid equivalent model is used to model the sound propagation in the porous material including absorption.

The second part of the thesis focuses on the prediction of thermoacoustic instabilities. Thermoacoustic instabilities arise when positive coupling occurs between the flame and the acoustics in the feedback loop, i.e. the flame acts as an amplifier of the disturbances (acoustic or fluid) at a natural frequency of the combustion system. Once the thermoacoustic instabilities occur, it will lead to extremely high noise levels within a relatively narrow frequency range, resulting in a huge damage to the structure of the combustors. Hence, a solution must be found, which breaks the link between the combustion process and the structural acoustics. The numerical prediction of thermoacoustic instabilities in the thesis is performed by two different numerical methodologies. One solves the Helmholtz equation in combination of the flame n − tau model with the low Mach number assumptions, and the other solves the Linearized Navier-Stokes equations in frequency domain with mean flow. The result show that the mean flow has a significant effect on the thermoacoustic instabilities, which is non-negligible when the Mach number reaches to 0.15.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2015. s. 69
Serie
TRITA-AVE, ISSN 1651-7660 ; 2015:98
Nyckelord
Linearized Navier-Stokes Equations, frequency domain, fluid equivalent model, hybrid liner, thermoacoustic instabilities, Rijke-tube
Nationell ämneskategori
Maskinteknik
Forskningsämne
Teknisk mekanik
Identifikatorer
urn:nbn:se:kth:diva-179677 (URN)978-91-7595-800-2 (ISBN)
Presentation
2015-12-15, D2, Lindstedtsvägen 5, KTH, Stockholm, 10:00 (Engelska)
Opponent
Handledare
Projekt
TANGO
Forskningsfinansiär
EU, FP7, Sjunde ramprogrammet, 26766
Anmärkning

QC 20151221

Tillgänglig från: 2015-12-21 Skapad: 2015-12-18 Senast uppdaterad: 2018-09-21Bibliografiskt granskad
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ORCID-id: ORCID iD iconorcid.org/0000-0001-5757-3668

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