Journal ArticleDOI
Coupled interaction between unsteady flame dynamics and acoustic field in a turbulent combustor
Vedasri Godavarthi,Samadhan A. Pawar,Vishnu R. Unni,R. I. Sujith,Norbert Marwan,Jürgen Kurths,Jürgen Kurths,Jürgen Kurths +7 more
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TLDR
A possible asymmetric bidirectional coupling between q ˙ ' and p ' is observed to exert a stronger influence on p ' than vice versa, and the directional property of the network measure, namely, cross transitivity is used to analyze the type of coupling existing between the acoustic field and the heat release rate fluctuations.Abstract:
Thermoacoustic instability is a result of the positive feedback between the acoustic pressure and the unsteady heat release rate fluctuations in a combustor. We apply the framework of the synchronization theory to study the coupled behavior of these oscillations during the transition to thermoacoustic instability in a turbulent bluff-body stabilized gas-fired combustor. Furthermore, we characterize this complex behavior using recurrence plots and recurrence networks. We mainly found that the correlation of probability of recurrence ( C P R), the joint probability of recurrence ( J P R), the determinism ( D E T), and the recurrence rate ( R R) of the joint recurrence matrix aid in detecting the synchronization transitions in this thermoacoustic system. We noticed that C P R and D E T can uncover the occurrence of phase synchronization state, whereas J P R and R R can be used as indices to identify the occurrence of generalized synchronization (GS) state in the system. We applied measures derived from joint and cross recurrence networks and observed that the joint recurrence network measures, transitivity ratio, and joint transitivity are useful to detect GS. Furthermore, we use the directional property of the network measure, namely, cross transitivity to analyze the type of coupling existing between the acoustic field ( p ′) and the heat release rate ( q ˙ ′) fluctuations. We discover a possible asymmetric bidirectional coupling between q ˙ ′ and p ′, wherein q ˙ ′ is observed to exert a stronger influence on p ′ than vice versa.Thermoacoustic instability is a result of the positive feedback between the acoustic pressure and the unsteady heat release rate fluctuations in a combustor. We apply the framework of the synchronization theory to study the coupled behavior of these oscillations during the transition to thermoacoustic instability in a turbulent bluff-body stabilized gas-fired combustor. Furthermore, we characterize this complex behavior using recurrence plots and recurrence networks. We mainly found that the correlation of probability of recurrence ( C P R), the joint probability of recurrence ( J P R), the determinism ( D E T), and the recurrence rate ( R R) of the joint recurrence matrix aid in detecting the synchronization transitions in this thermoacoustic system. We noticed that C P R and D E T can uncover the occurrence of phase synchronization state, whereas J P R and R R can be used as indices to identify the occurrence of generalized synchronization (GS) state in the system. We applied measures derive...read more
Citations
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Journal ArticleDOI
Complex system approach to investigate and mitigate thermoacoustic instability in turbulent combustors
R. I. Sujith,Vishnu R. Unni +1 more
TL;DR: In this article, the authors discuss various prognosis and mitigation strategies for thermo-acoustic instability based on complex system theory in turbulent combustors, where the authors view the thermoacoustic system in a turbulent combustor as a complex system and the dynamics exhibited by the system is perceived as emergent behaviors of this complex system.
Journal ArticleDOI
Early Detection of Thermoacoustic Combustion Instability Using a Methodology Combining Complex Networks and Machine Learning
TL;DR: A feature space consisting of the principal component plane estimated from the probability distribution of the transition patterns, which is obtained by a support vector machine, allows the early detection of thermoacoustic combustion instability.
Journal ArticleDOI
Dynamical systems and complex systems theory to study unsteady combustion
R. I. Sujith,Vishnu R. Unni +1 more
TL;DR: In this article, a range of problems involving unsteady combustion such as thermoacoustic instability, flame blowout, fire propagation, reaction chemistry and flow flame interaction are discussed. But the focus is not on the effects of these processes on the actual combustion system.
Journal ArticleDOI
Spatiotemporal dynamics and early detection of thermoacoustic combustion instability in a model rocket combustor
TL;DR: The turbulence network, which consists of nodes and vertexes in weighted networks between vortices, can characterize the complex spatiotemporal structure of a flow field during thermoacoustic combustion instability.
Journal ArticleDOI
Dynamical systems approach to study thermoacoustic transitions in a liquid rocket combustor
Praveen Kasthuri,Induja Pavithran,Samadhan A. Pawar,R. I. Sujith,Rohan Gejji,William E. Anderson +5 more
TL;DR: This paper adopts tools from dynamical systems and complex systems theory to understand the dynamical transitions from a state of stable operation to thermoacoustic instability in a self-excited model multielement liquid rocket combustor based on an oxidizer rich staged combustion cycle.
References
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Journal ArticleDOI
Combustion noise is scale-free: transition from scale-free to order at the onset of thermoacoustic instability
TL;DR: In this paper, the scale invariance of combustion noise generated from turbulent reacting flows in a confined environment using complex networks is investigated and the scale-free properties of complex networks obtained from low-amplitude, aperiodic pressure fluctuations during combustion noise have been investigated.
Journal ArticleDOI
Impact of Linear Coupling on the Design of Active Controllers for the Thermoacoustic Instability
TL;DR: In this paper, the effect of linear coupling on the resonance and anliresonance properties of a benchlop premised combuslor in the presence of external excitation is investigated.
Journal ArticleDOI
Bifurcations of Self-Excited Ducted Laminar Premixed Flames
TL;DR: In this article, a simple setup consisting of ducted laminar premixed conical flames was used to investigate the features of nonlinear thermoacoustic oscillations, and it was observed that the system undergoes a series of bifurcations leading to characteristically different nonlinear oscillations.
Journal ArticleDOI
Acoustic radiation from turbulent premixed flames
Rajesh Rajaram,Tim Lieuwen +1 more
TL;DR: In this article, the authors used the spatiotemporal coherence of a flame's chemiluminescence emissions to determine the heat release spectrum, spatial distribution and spatial coherence characteristics.
Journal ArticleDOI
A Model-Based Active Control Design for Thermoacoustic Instability
TL;DR: In this article, the authors present an alternative design methodology based on the underlying physical model of the combustor and modern control theory, and show that using this methodology, one can avoid the generation of secondary peaks and achieve short settling time using small control energy.