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
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
Recurrence networks to study dynamical transitions in a turbulent combustor
TL;DR: It is demonstrated that the measures derived from recurrence network can be used as tools to capture the transitions in the turbulent combustor and also as early warning measures for predicting impending thermoacoustic instability and blowout.
Journal ArticleDOI
Multifractal characteristics of combustor dynamics close to lean blowout
Vishnu R. Unni,R. I. Sujith +1 more
TL;DR: In this article, the authors provide a multifractal description for lean blowout in combustors with turbulent flow and thus introduce a unified framework within which both thermoacoustic instability and blowout can be described.
Journal ArticleDOI
Characterization of Combustion Dynamics, Detection, and Prevention of an Unstable Combustion State Based on a Complex-Network Theory
TL;DR: This study shows how to use a pragmatic, online detection methodology, based on the theory of complex networks, to control unstable combustion in a turbulent thermoacoustic system to avoid blowout conditions and engine shutdown.
Journal ArticleDOI
On interrelations of recurrences and connectivity trends between stock indices
TL;DR: In this article, the authors employ an estimator based on recurrence plots (C P R ) to analyze connections between nine stock indices spread worldwide and suggest a slight modification of the C P R approach in order to get more robust results.