Lipika Kabiraj - Academia.edu (original) (raw)

Papers by Lipika Kabiraj

54th AIAA Aerospace Sciences Meeting, 2016

Chaos (Woodbury, N.Y.), 2016

In this paper, it is shown that prior to flashback, small dynamical changes appear in the system.... more In this paper, it is shown that prior to flashback, small dynamical changes appear in the system. These changes appear as a drift in the recurrence plots and are found to be associated with a gradual increase in the determinism and recurrence rate. Thus, this study indicates that precursors to flame flashback exist and can be detected in the multidimensional phase space reconstructed from pressure measurements acquired during flashback. This observation could have broad academic as well as industrial implications.

Physical Review E, 2015

We experimentally investigated the noise-induced dynamics of a prototypical thermoacoustic system... more We experimentally investigated the noise-induced dynamics of a prototypical thermoacoustic system undergoing a subcritical Hopf bifurcation to limit cycle oscillations. The study was performed prior to the bistable regime. Analysis of the characteristics of pressure oscillations in the combustor and fluctuations in the heat release rate from the flame-the two physical entities involved in thermoacoustic coupling-at increasing levels of noise indicated precursors to the Hopf bifurcation. These precursors were further identified to be a result of coherence resonance.

Volume 2: Combustion, Fuels and Emissions, Parts A and B, 2011

ABSTRACT Bifurcation analysis is conducted on experimental data obtained from a simple setup comp... more ABSTRACT Bifurcation analysis is conducted on experimental data obtained from a simple setup comprising of ducted, laminar pre-mixed conical flames to investigate the features of nonlinear thermoacoustic oscillations. It is observed that as the bifurcation parameter is varied, the system undergoes series of bifurcations leading to characteristically different nonlinear oscillations. Through the application of nonlinear time series analysis on pressure and flame (CH* chemiluminescence) intensity time traces, these oscillations are characterised as periodic, aperiodic or chaotic oscillations and subsequently the nature of the obtained bifurcations is explained based on dynamical systems theory. Nonlinear interaction between the flames and the acoustic modes of the duct is clearly reflected in the high speed flame images acquired simultaneously with pressure and flame intensity measurements.

Emission of acoustic perturbations by rod-stabilized turbulent premixed flames at a low Reynolds ... more Emission of acoustic perturbations by rod-stabilized turbulent premixed flames at a low Reynolds number (Re ∼ 4500) is investigated in the present article. Variation of the equivalence ratio gave rise to two different flame configurations which are investigated through a comparative study, also involving the isothermal flow case. Specifically flow and flame dynamics associated with coherent oscillations are the focus here. The study is based on acoustic measurements, flow and flame diagnostics. In addition to commonly employed spectral analysis, nonlinear time series analysis of the acoustic pressure signal is introduced here.

ABSTRACT Emission of acoustic perturbations by rod-stabilized turbulent premixed flames at a low ... more ABSTRACT Emission of acoustic perturbations by rod-stabilized turbulent premixed flames at a low Reynolds number (Re ∼ 4500) is investigated in the present article. Variation of the equivalence ratio gave rise to two different flame configurations which are investigated through a comparative study, also involving the isothermal flow case. Specifically flow and flame dynamics associated with coherent oscillations are the focus here. The study is based on acoustic measurements, flow and flame diagnostics. In addition to commonly employed spectral analysis, nonlinear time series analysis of the acoustic pressure signal is introduced here.

Flame-acoustics interaction results in high amplitude pressure oscillations in most practical com... more Flame-acoustics interaction results in high amplitude pressure oscillations in most practical combustion systems. Experiments were conducted on a thermoacoustic system comprising of ducted, laminar, premixed flames. Bifurcation analysis of the system was conducted with flame location as the control parameter. Several regimes of characteristically different nonlinear oscillations were identified and described in the light of nonlinear dynamical systems theory, applied to the scalar time series of obtained pressure and heat release rate fluctuations.

AIAA Journal, 2015

ABSTRACT Recurrence analysis of phase space trajectories reconstructed from scalar time series—a ... more ABSTRACT Recurrence analysis of phase space trajectories reconstructed from scalar time series—a relatively new technique in the field of combustion dynamics—is proposed for analyzing combustion noise data. A demonstration based on the implementation of this analysis on combustion noise data acquired in experiments on an open bluff-body stabilized turbulent premixed flame is presented in this article. A combined analysis methodology involving conventional techniques: spectral analysis and proper orthogonal decomposition, together with recurrence analysis is found to be effective in identifying features embedded in combustion noise signals. In particular, the new perspective provides insights into the temporal transitions of pressure fluctuations between noise and periodic dynamics. The recurrence analysis technique, which is found to be instrumental in extracting the dynamical makeup of combustion noise signals in this work, is foreseen to be greatly beneficial for the analysis of experimental and numerical results on turbulent flows and turbulent combustion—processes that often involve an interplay between noise and deterministic dynamics. Read More: http://arc.aiaa.org/doi/abs/10.2514/1.J053285

ABSTRACT To study the nonlinear behavior of thermoacoustic instability, experiments were conducte... more ABSTRACT To study the nonlinear behavior of thermoacoustic instability, experiments were conducted on a setup comprising of laminar premixed flames confined in a duct. The observed oscillations in pressure and heat release rate during the instability were studied in the framework of dynamical systems theory. It was found that as the flame location relative to the duct was gradually varied, the oscillations underwent transitions in their qualitative behavior. Periodic, quasi-periodic and chaotic oscillations were observed at different flame locations in the duct.

19th AIAA/CEAS Aeroacoustics Conference, 2013

50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2012

52nd Aerospace Sciences Meeting, 2014

Volume 2: Combustion, Fuels and Emissions, Parts A and B, 2011

ABSTRACT An experimental investigation of the bistable region of instability in a thermoacoustic ... more ABSTRACT An experimental investigation of the bistable region of instability in a thermoacoustic system comprising of ducted, pre-mixed laminar flames has been performed. The stability diagram of the system is obtained and the bistable region for a range of flame locations at different fuel-air mixture equivalence ratios is identified. Subsequently, threshold amplitudes for triggering instability in the system using sinusoidal acoustic forcing, introduced externally, is obtained. It is observed that depending on how close the system is to the Hopf point and the nature of oscillations at the Hopf point, the triggered oscillations can exhibit different dynamical behavior.

Volume 2: Combustion, Fuels and Emissions, Parts A and B, 2012

ABSTRACT Lean flame blowout induced by thermoacoustic oscillations is a serious problem faced by ... more ABSTRACT Lean flame blowout induced by thermoacoustic oscillations is a serious problem faced by the power and propulsion industry. We analyze a prototypical thermoacoustic system through systematic bifurcation analysis and find that starting from a steady state, this system exhibits successive bifurcations resulting in complex nonlinear oscillation states, eventually leading to flame blowout. To understand the observed bifurcations, we analyze the oscillation states using nonlinear time series analysis, particularly through the representation of pressure oscillations on a reconstructed phase space. Prior to flame blowout, a bursting phenomenon is observed in pressure oscillations. These burst oscillations are found to exhibit similarities with the phenomenon known as intermittency in the dynamical systems theory. This investigation based on nonlinear analysis of experimentally acquired data from a thermoacoustic system sheds light on how thermoacoustic oscillations lead to flame blowout.

Journal of Fluid Mechanics, 2012

Nonlinear self-excited thermoacoustic oscillations appear in systems involving confined combustio... more Nonlinear self-excited thermoacoustic oscillations appear in systems involving confined combustion in the form of coupled acoustic pressure oscillations and unsteady heat release rate. In this paper, we investigate the nonlinear transition undergone by thermoacoustic oscillations to flame blowout via intermittency, in response to variation in the location of the combustion source with respect to the acoustic field of the confinement. A ducted laminar premixed conical flame, stabilized on a circular jet exit with a fully developed exit velocity profile, was investigated. Transition to limit cycle oscillations from a non-oscillatory state was observed to occur via a subcritical Hopf bifurcation. Limit cycle oscillations underwent a further bifurcation to quasi-periodic oscillations characterized by the repeated formation of elongated necks in the flame that pinch off as pockets of unburned fuel-air mixture. The quasi-periodic state loses stability, resulting in an intermittent state identified as type II through recurrence analysis of phase space trajectories reconstructed from the acoustic pressure time trace. In this state, the flame undergoes repeated lift-off and reattachment. Instantaneous flame images suggest that the intermittent flame behaviour is influenced by jet flow dynamics.

Journal of Engineering for Gas Turbines and Power, 2012

ABSTRACT Bifurcation analysis is performed on experimental data obtained from a simple setup comp... more ABSTRACT Bifurcation analysis is performed on experimental data obtained from a simple setup comprising ducted laminar premixed conical flames in order to investigate the features of nonlinear thermoacoustic oscillations. It is observed that as the bifurcation parameter is varied, the system undergoes a series of bifurcations leading to characteristically different nonlinear oscillations. Through the application of nonlinear time series analysis to pressure and flame (CH* chemiluminescence) intensity time traces, these oscillations are characterized as periodic, aperiodic, or chaotic oscillations, and subsequently the nature of the obtained bifurcations is explained based on dynamical systems theory. Nonlinear interaction between the flames and the acoustic modes of the duct is clearly reflected in the high speed flame images acquired simultaneously with pressure time series. [DOI: 10.1115/1.4004402]

Fluid Dynamics Research, 2012

The dynamics of combustion-driven thermoacoustic oscillations for a ducted laminar premixed flame... more The dynamics of combustion-driven thermoacoustic oscillations for a ducted laminar premixed flame has been investigated in lean equivalence ratio conditions. Combustion instability appears in the system as acoustic pressure and flame surface oscillations following a Hopf bifurcation. Further change in the control parameter leads to subsequent bifurcations, causing a rich dynamical behavior such as quasi-periodic and intermittent burst oscillations to appear in the system. During the burst oscillation phase, the system dynamics resembles the flame blowout phenomenon, which is of interest in practical combustion applications.

Chaos: An Interdisciplinary Journal of Nonlinear Science, 2012

Chaos: An Interdisciplinary Journal of Nonlinear Science, 2015

This article reports nonlinear bifurcations observed in a laboratory scale, turbulent combustor o... more This article reports nonlinear bifurcations observed in a laboratory scale, turbulent combustor operating under imperfectly premixed mode with global equivalence ratio as the control parameter. The results indicate that the dynamics of thermoacoustic instability correspond to quasi-periodic bifurcation to low-dimensional, deterministic chaos, a route that is common to a variety of dissipative nonlinear systems. The results support the recent identification of bifurcation scenarios in a laminar premixed flame combustor (Kabiraj et al., Chaos: Interdiscip. J. Nonlinear Sci. 22, 023129 (2012)) and extend the observation to a practically relevant combustor configuration.

54th AIAA Aerospace Sciences Meeting, 2016

Chaos (Woodbury, N.Y.), 2016

In this paper, it is shown that prior to flashback, small dynamical changes appear in the system.... more In this paper, it is shown that prior to flashback, small dynamical changes appear in the system. These changes appear as a drift in the recurrence plots and are found to be associated with a gradual increase in the determinism and recurrence rate. Thus, this study indicates that precursors to flame flashback exist and can be detected in the multidimensional phase space reconstructed from pressure measurements acquired during flashback. This observation could have broad academic as well as industrial implications.

Physical Review E, 2015

We experimentally investigated the noise-induced dynamics of a prototypical thermoacoustic system... more We experimentally investigated the noise-induced dynamics of a prototypical thermoacoustic system undergoing a subcritical Hopf bifurcation to limit cycle oscillations. The study was performed prior to the bistable regime. Analysis of the characteristics of pressure oscillations in the combustor and fluctuations in the heat release rate from the flame-the two physical entities involved in thermoacoustic coupling-at increasing levels of noise indicated precursors to the Hopf bifurcation. These precursors were further identified to be a result of coherence resonance.

Volume 2: Combustion, Fuels and Emissions, Parts A and B, 2011

ABSTRACT Bifurcation analysis is conducted on experimental data obtained from a simple setup comp... more ABSTRACT Bifurcation analysis is conducted on experimental data obtained from a simple setup comprising of ducted, laminar pre-mixed conical flames to investigate the features of nonlinear thermoacoustic oscillations. It is observed that as the bifurcation parameter is varied, the system undergoes series of bifurcations leading to characteristically different nonlinear oscillations. Through the application of nonlinear time series analysis on pressure and flame (CH* chemiluminescence) intensity time traces, these oscillations are characterised as periodic, aperiodic or chaotic oscillations and subsequently the nature of the obtained bifurcations is explained based on dynamical systems theory. Nonlinear interaction between the flames and the acoustic modes of the duct is clearly reflected in the high speed flame images acquired simultaneously with pressure and flame intensity measurements.

Emission of acoustic perturbations by rod-stabilized turbulent premixed flames at a low Reynolds ... more Emission of acoustic perturbations by rod-stabilized turbulent premixed flames at a low Reynolds number (Re ∼ 4500) is investigated in the present article. Variation of the equivalence ratio gave rise to two different flame configurations which are investigated through a comparative study, also involving the isothermal flow case. Specifically flow and flame dynamics associated with coherent oscillations are the focus here. The study is based on acoustic measurements, flow and flame diagnostics. In addition to commonly employed spectral analysis, nonlinear time series analysis of the acoustic pressure signal is introduced here.

ABSTRACT Emission of acoustic perturbations by rod-stabilized turbulent premixed flames at a low ... more ABSTRACT Emission of acoustic perturbations by rod-stabilized turbulent premixed flames at a low Reynolds number (Re ∼ 4500) is investigated in the present article. Variation of the equivalence ratio gave rise to two different flame configurations which are investigated through a comparative study, also involving the isothermal flow case. Specifically flow and flame dynamics associated with coherent oscillations are the focus here. The study is based on acoustic measurements, flow and flame diagnostics. In addition to commonly employed spectral analysis, nonlinear time series analysis of the acoustic pressure signal is introduced here.

Flame-acoustics interaction results in high amplitude pressure oscillations in most practical com... more Flame-acoustics interaction results in high amplitude pressure oscillations in most practical combustion systems. Experiments were conducted on a thermoacoustic system comprising of ducted, laminar, premixed flames. Bifurcation analysis of the system was conducted with flame location as the control parameter. Several regimes of characteristically different nonlinear oscillations were identified and described in the light of nonlinear dynamical systems theory, applied to the scalar time series of obtained pressure and heat release rate fluctuations.

AIAA Journal, 2015

ABSTRACT Recurrence analysis of phase space trajectories reconstructed from scalar time series—a ... more ABSTRACT Recurrence analysis of phase space trajectories reconstructed from scalar time series—a relatively new technique in the field of combustion dynamics—is proposed for analyzing combustion noise data. A demonstration based on the implementation of this analysis on combustion noise data acquired in experiments on an open bluff-body stabilized turbulent premixed flame is presented in this article. A combined analysis methodology involving conventional techniques: spectral analysis and proper orthogonal decomposition, together with recurrence analysis is found to be effective in identifying features embedded in combustion noise signals. In particular, the new perspective provides insights into the temporal transitions of pressure fluctuations between noise and periodic dynamics. The recurrence analysis technique, which is found to be instrumental in extracting the dynamical makeup of combustion noise signals in this work, is foreseen to be greatly beneficial for the analysis of experimental and numerical results on turbulent flows and turbulent combustion—processes that often involve an interplay between noise and deterministic dynamics. Read More: http://arc.aiaa.org/doi/abs/10.2514/1.J053285

ABSTRACT To study the nonlinear behavior of thermoacoustic instability, experiments were conducte... more ABSTRACT To study the nonlinear behavior of thermoacoustic instability, experiments were conducted on a setup comprising of laminar premixed flames confined in a duct. The observed oscillations in pressure and heat release rate during the instability were studied in the framework of dynamical systems theory. It was found that as the flame location relative to the duct was gradually varied, the oscillations underwent transitions in their qualitative behavior. Periodic, quasi-periodic and chaotic oscillations were observed at different flame locations in the duct.

19th AIAA/CEAS Aeroacoustics Conference, 2013

50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2012

52nd Aerospace Sciences Meeting, 2014

Volume 2: Combustion, Fuels and Emissions, Parts A and B, 2011

ABSTRACT An experimental investigation of the bistable region of instability in a thermoacoustic ... more ABSTRACT An experimental investigation of the bistable region of instability in a thermoacoustic system comprising of ducted, pre-mixed laminar flames has been performed. The stability diagram of the system is obtained and the bistable region for a range of flame locations at different fuel-air mixture equivalence ratios is identified. Subsequently, threshold amplitudes for triggering instability in the system using sinusoidal acoustic forcing, introduced externally, is obtained. It is observed that depending on how close the system is to the Hopf point and the nature of oscillations at the Hopf point, the triggered oscillations can exhibit different dynamical behavior.

Volume 2: Combustion, Fuels and Emissions, Parts A and B, 2012

ABSTRACT Lean flame blowout induced by thermoacoustic oscillations is a serious problem faced by ... more ABSTRACT Lean flame blowout induced by thermoacoustic oscillations is a serious problem faced by the power and propulsion industry. We analyze a prototypical thermoacoustic system through systematic bifurcation analysis and find that starting from a steady state, this system exhibits successive bifurcations resulting in complex nonlinear oscillation states, eventually leading to flame blowout. To understand the observed bifurcations, we analyze the oscillation states using nonlinear time series analysis, particularly through the representation of pressure oscillations on a reconstructed phase space. Prior to flame blowout, a bursting phenomenon is observed in pressure oscillations. These burst oscillations are found to exhibit similarities with the phenomenon known as intermittency in the dynamical systems theory. This investigation based on nonlinear analysis of experimentally acquired data from a thermoacoustic system sheds light on how thermoacoustic oscillations lead to flame blowout.

Journal of Fluid Mechanics, 2012

Nonlinear self-excited thermoacoustic oscillations appear in systems involving confined combustio... more Nonlinear self-excited thermoacoustic oscillations appear in systems involving confined combustion in the form of coupled acoustic pressure oscillations and unsteady heat release rate. In this paper, we investigate the nonlinear transition undergone by thermoacoustic oscillations to flame blowout via intermittency, in response to variation in the location of the combustion source with respect to the acoustic field of the confinement. A ducted laminar premixed conical flame, stabilized on a circular jet exit with a fully developed exit velocity profile, was investigated. Transition to limit cycle oscillations from a non-oscillatory state was observed to occur via a subcritical Hopf bifurcation. Limit cycle oscillations underwent a further bifurcation to quasi-periodic oscillations characterized by the repeated formation of elongated necks in the flame that pinch off as pockets of unburned fuel-air mixture. The quasi-periodic state loses stability, resulting in an intermittent state identified as type II through recurrence analysis of phase space trajectories reconstructed from the acoustic pressure time trace. In this state, the flame undergoes repeated lift-off and reattachment. Instantaneous flame images suggest that the intermittent flame behaviour is influenced by jet flow dynamics.

Journal of Engineering for Gas Turbines and Power, 2012

ABSTRACT Bifurcation analysis is performed on experimental data obtained from a simple setup comp... more ABSTRACT Bifurcation analysis is performed on experimental data obtained from a simple setup comprising ducted laminar premixed conical flames in order to investigate the features of nonlinear thermoacoustic oscillations. It is observed that as the bifurcation parameter is varied, the system undergoes a series of bifurcations leading to characteristically different nonlinear oscillations. Through the application of nonlinear time series analysis to pressure and flame (CH* chemiluminescence) intensity time traces, these oscillations are characterized as periodic, aperiodic, or chaotic oscillations, and subsequently the nature of the obtained bifurcations is explained based on dynamical systems theory. Nonlinear interaction between the flames and the acoustic modes of the duct is clearly reflected in the high speed flame images acquired simultaneously with pressure time series. [DOI: 10.1115/1.4004402]

Fluid Dynamics Research, 2012

The dynamics of combustion-driven thermoacoustic oscillations for a ducted laminar premixed flame... more The dynamics of combustion-driven thermoacoustic oscillations for a ducted laminar premixed flame has been investigated in lean equivalence ratio conditions. Combustion instability appears in the system as acoustic pressure and flame surface oscillations following a Hopf bifurcation. Further change in the control parameter leads to subsequent bifurcations, causing a rich dynamical behavior such as quasi-periodic and intermittent burst oscillations to appear in the system. During the burst oscillation phase, the system dynamics resembles the flame blowout phenomenon, which is of interest in practical combustion applications.

Chaos: An Interdisciplinary Journal of Nonlinear Science, 2012

Chaos: An Interdisciplinary Journal of Nonlinear Science, 2015

This article reports nonlinear bifurcations observed in a laboratory scale, turbulent combustor o... more This article reports nonlinear bifurcations observed in a laboratory scale, turbulent combustor operating under imperfectly premixed mode with global equivalence ratio as the control parameter. The results indicate that the dynamics of thermoacoustic instability correspond to quasi-periodic bifurcation to low-dimensional, deterministic chaos, a route that is common to a variety of dissipative nonlinear systems. The results support the recent identification of bifurcation scenarios in a laminar premixed flame combustor (Kabiraj et al., Chaos: Interdiscip. J. Nonlinear Sci. 22, 023129 (2012)) and extend the observation to a practically relevant combustor configuration.