A Reduced-order Model for Lock-on via Vortex-combustion-acoustic Closed-loop Coupling in A Step Combustor

The lock-on of the frequency of acoustic oscillations to the frequency of the vortex shedding in a reacting flow in a backward-facing step combustor is demonstrated using a reduced-order model. Individual models for the flow, flame and acoustic models are developed. A two-dimensional flow field with...

Full description

Saved in:
Bibliographic Details
Published in:Combustion science and technology 2022-11, Vol.194 (15), p.3109-3131
Main Authors: Vasanth, Joel V., Chakravarthy, Satyanarayanan R.
Format: Article
Language:English
Subjects:
Acoustic mapping
Acoustics
Backward facing steps
Combustion
Combustion chambers
combustion instability
Conformal mapping
Fluctuations
Fluid flow
Galerkin method
Heat release rate
Heat transfer
Oscillators
Potential flow
Reacting flow
Reduced order models
reduced-order modeling
Reynolds number
Two dimensional flow
Vortex shedding
Vortex-acoustic lock-on
Vortices
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The lock-on of the frequency of acoustic oscillations to the frequency of the vortex shedding in a reacting flow in a backward-facing step combustor is demonstrated using a reduced-order model. Individual models for the flow, flame and acoustic models are developed. A two-dimensional flow field with growth and shedding of vortices is modeled using a potential flow model derived via a conformal mapping of the step geometry. Combustion and acoustic models are derived using thermo-diffusive equations and the one-dimensional Galerkin method, respectively. A modulation of heat release rate fluctuations is thus enabled by vortices advecting past the flame, overcoming the time and space-localized assumptions in vortex kicked oscillator models. Comparisons with results from kicked oscillator models show a better prediction of the dominant frequencies during stable and unstable operations. A Reynolds number sweep is performed to reveal the transition from stable to unstable operation and thus the onset of instability. A shift in the dominant frequency of pressure fluctuations from the natural duct acoustic mode to the natural vortex shedding mode is observed, indicative of a lock-on. The results compare well with past experimental and computational data for similar geometry and flow conditions.
ISSN:0010-2202
1563-521X
DOI:10.1080/00102202.2021.1909578