Aeroacoustics of rectangular T-junctions subject to combined grazing and bias flows – An experimental investigation

Holmberg, Andreas; Karlsson, Mikael; Åbom, Mats

doi:10.1016/j.jsv.2014.11.040

Cited by 14 publications

(2 citation statements)

References 30 publications

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“…Karlsson and Åbom 14 and Holmberg et al 15 introduced a technique, where a 3-port can be evaluated with a 3 × 3 scattering matrix (SM) representing the reflection and transmission coefficients of the system R and T for the selected state variables. With the application to thermoacoustics in RQL combustors in mind it is convenient to introduce the acoustic Riemann invariants f = 1 / 2 false( p ′ / ρ ¯ c + u normal′ false) and g = 1 / 2 false( p ′ / ρ ¯ c − u normal′ false) as state variables to describe the network elements in terms of harmonic acoustic disturbances that propagate in co-flow and counter-flow direction.…”

Section: The Lean Secondary Zone As a Thermoacoustic 3-portmentioning

confidence: 99%

Flame Transfer Functions of the Lean Burnout Zone of an RQL Combustion Chamber - Dynamic Response to Primary Zone and Mixing Port Velocity Fluctuations

Renner

March

et al. 2023

International Journal of Spray and Combustion Dynamics

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This article describes an experimental investigation of thermoacoustic flame transfer functions of the lean burnout zone of an rich–quench–lean combustion chamber. With spatial separation of the rich primary from the lean secondary dilution zone, the latter is independently examined. The multi-microphone-method was employed to characterize the combustor acoustic velocity response to acoustic forcing coming from the primary zone and the mixing ports. The lean secondary zone is then treated as a pure acoustic 3-port network element connected to a 2-port Rankine-Hugoniot flame element. Focusing only on heat release fluctuations due to velocity fluctuations, the former are described by two linear superimposed flame transfer functions as a function of the velocity fluctuations coming from the primary zone and the mixing ports, respectively. Based on a non-reacting and a reacting measurement the two flame transfer functions could be extracted from the experimental data. Within this research, flame transfer functions from the new acoustical approach are presented and compared with ones measured using chemiluminescence and a photomultiplier tube. It is found that the inverse diffusion flame in the burnout zone reacts to velocity fluctuations from the primary zone in the low frequency range and a clear low pass behavior is observed. The mixing port velocity fluctuations create a more broadband response. In the presented cases, the flame transfer functions calculated from chemiluminescence match those from the acoustic method very well.

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Section: The Lean Secondary Zone As a Thermoacoustic 3-portmentioning

confidence: 99%

Flame Transfer Functions of the Lean Burnout Zone of an RQL Combustion Chamber - Dynamic Response to Primary Zone and Mixing Port Velocity Fluctuations

Renner

March

et al. 2023

International Journal of Spray and Combustion Dynamics

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“…The basic technique for the network treatment of 3-ports was proposed by Karlsson and Åbom 14 and Holmberg et al 15 . They describe the 3-port by a 3 × 3 matrix which can be determined by three acoustically independent measurements, which provide the equations for the 9 unknown complex matrix elements.…”

Section: Thermoacoustic Theory Of Rql Combustorsmentioning

confidence: 99%

Flame dynamics in the lean burnout zone of an RQL combustion chamber - response to primary zone velocity fluctuations

Renner

March

Hirsch

et al. 2022

International Journal of Spray and Combustion Dynamics

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This study focuses on elucidating the flame dynamics of the lean burnout zone of an Rich-Quench-Lean (RQL) combustion chamber. With a new experimental approach of spatially separating the rich primary zone from the lean burnout zone, the latter can be investigated independently in terms of velocity fluctuations. Acoustically stiff mixing air ports in the lean burnout zone are ensured to prevent any acoustic interaction of the primary crossflow with the secondary mixing air jets. Therefore, defined boundary conditions at the mixing air inlets are used. Resulting no thermoacoustic interaction and additional flame dynamics are generated. In this specific case the lean burnout zone can be treated as a 2-port system allowing the application of existing evaluation methods e.g. acoustic determination of flame-transfer-functions (FTF) from the Rankine-Hugoniot (RH) equation or quantification of the heat release with chemiluminescence in combination with the Multi-Microphone-Method (MMM). Within this research, FTFs acoustically measured with the RH approach are presented and serve as a baseline for comparison with ones measured via a photomultiplier tube (PMT). It is found that the inverse diffusion flame in the burnout zone only reacts to fluctuations in the low frequency range and a clear low pass behavior is observed. The FTFs, calculated via the PMT match those from RH very well. Amplitude weighted phase images, recorded with a high-speed camera setup, visualize changes during excitation which complement and confirm the findings from the FTF.

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Numerical Study on the Sound Amplification of a T-Junction with Bias Flow

Du¹,

Karlsson²,

Åbom³

2016

Springer Proceedings in Physics

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Aeroacoustics of rectangular T-junctions subject to combined grazing and bias flows – An experimental investigation

Cited by 14 publications

References 30 publications

Flame Transfer Functions of the Lean Burnout Zone of an RQL Combustion Chamber - Dynamic Response to Primary Zone and Mixing Port Velocity Fluctuations

Flame Transfer Functions of the Lean Burnout Zone of an RQL Combustion Chamber - Dynamic Response to Primary Zone and Mixing Port Velocity Fluctuations

Flame dynamics in the lean burnout zone of an RQL combustion chamber - response to primary zone velocity fluctuations

Numerical Study on the Sound Amplification of a T-Junction with Bias Flow

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