Intermittency, Secondary Bifurcation and Mixed-Mode Oscillations in a Swirl-Stabilized Annular Combustor: Experiments and Modeling

2020 ◽  
Author(s):  
Samarjeet Singh ◽  
Amitesh Roy ◽  
Reeja K. V. ◽  
Asalatha Nair ◽  
Swetaprovo Chaudhuri ◽  
...  
Keyword(s):  
Mixed Mode ◽  
Equivalence Ratio ◽  
High Amplitude ◽  
The State ◽  
Turbulent Flames ◽  
Bulk Velocity ◽  
Thermoacoustic Instability ◽  
Mixed Mode Oscillations ◽  
Annular Combustor ◽  
Low Amplitude

Abstract We experimentally study thermoacoustic transitions in an annular combustor consisting of sixteen premixed, swirl-stabilized turbulent flames. We show the changes in the characteristics of bifurcations leading to the state of longitudinal thermoacoustic instability (TAI) when equivalence ratio and bulk velocity are systematically varied. Depending upon the bulk velocity, we observe different states of combustor operation when the equivalence ratio is varied. These states include combustion noise, intermittency, low-amplitude TAI, mixed-mode oscillations (MMO), and high-amplitude TAI. We closely examine the special case of MMO that is encountered during the transition from low-amplitude TAI to high-amplitude TAI. We also discuss the global and local flame dynamics observed during the state of MMO. We find that during epochs of low-amplitude oscillations of MMO, all the flames are partially synchronized, while during epochs of high-amplitude oscillations, all the flames are perfectly synchronized. Finally, we replicate the criticalities of bifurcation of the annular combustor in a phenomenological model containing sixth-order nonlinearities.

Intermittency, Secondary Bifurcation and Mixed-Mode Oscillations in a Swirl-Stabilized Annular Combustor: Experiments and Modeling

2020 ◽  
Author(s):  
Samarjeet Singh ◽  
Amitesh Roy ◽  
K. V. Reeja ◽  
Asalatha Nair ◽  
Swetaprovo Chaudhuri ◽  
...  
Keyword(s):  
Mixed Mode ◽  
Equivalence Ratio ◽  
High Amplitude ◽  
The State ◽  
Turbulent Flames ◽  
Bulk Velocity ◽  
Thermoacoustic Instability ◽  
Mixed Mode Oscillations ◽  
Annular Combustor ◽  
Low Amplitude

Abstract We experimentally study thermoacoustic transitions in an annular combustor consisting of sixteen premixed, swirl-stabilized turbulent flames. We show the changes in the characteristics of bifurcations leading to the state of longitudinal thermoacoustic instability (TAI) when equivalence ratio and bulk velocity are systematically varied. Depending upon the bulk velocity, we observe different states of combustor operation when the equivalence ratio is varied. These states include combustion noise, intermittency, low-amplitude TAI, mixed-mode oscillations (MMO), and high-amplitude TAI. We closely examine the special case of MMO that is encountered during the transition from low-amplitude TAI to high-amplitude TAI. We also discuss the global and local flame dynamics observed during the state of MMO. We find that during epochs of low-amplitude oscillations of MMO, all the flames are partially synchronized, while during epochs of high-amplitude oscillations, all the flames are perfectly synchronized. Finally, we replicate the criticalities of bifurcation of the annular combustor in a phenomenological model containing sixth-order nonlinearities.

Intermittency, Secondary Bifurcation and Mixed Mode Oscillations in a Swirl-Stabilized Annular Combustor: Experiments and Modeling

2021 ◽  
Author(s):  
Samarjeet Singh ◽  
Amitesh Roy ◽  
K V Reeja ◽  
Asalatha A. S. Nair ◽  
Swetaprovo Chaudhuri ◽  
...  
Keyword(s):  
Mixed Mode ◽  
Mixed Mode Oscillations ◽  
Annular Combustor ◽  
Secondary Bifurcation

Transient Thermoacoustic Responses of Methane/Hydrogen Flames in a Pressurized Annular Combustor

2021 ◽  
Author(s):  
Byeonguk Ahn ◽  
Thomas Indlekofer ◽  
James Dawson ◽  
Nicholas Worth
Keyword(s):  
Equivalence Ratio ◽  
Time History ◽  
High Amplitude ◽  
Transient Growth ◽  
Local Minima ◽  
Driving Mechanisms ◽  
Annular Combustor ◽  
History Of ◽  
Harmonic Components ◽  
Hysteresis Behaviour

Abstract The present article experimentally investigates the triggering and transient growth of azimuthal instabilities in a pressurized laboratory-scale annular combustor featuring twelve methane/hydrogen flames, as the equivalence ratio is ramped up and down. The ramping rate of equivalence ratio is varied to examine its effect on the transient thermoacoustic response and the driving mechanisms, highlighting a number of previously unseen features. As the equivalence ratio is dynamically increased, all cases were observed to feature a distinct modal trajectory, during the onset of high amplitude instabilities. Strongly spinning counter-clockwise modes are first excited before a dynamic transition to strongly spinning clockwise modes occurs. Furthermore, the strength of the spinning mode (quantified through the spin ratio or nature angle) was shown to feature a local minima before the spinning mode stabilized in the system, which corresponds to an almost pure spinning state. Hysteresis behaviour was observed in both the amplitude and nature of the mode, resulting in different thresholds for the onset and decay of the instability, depending on the time history of the combustor. Increasing the ramping rate was found to reduce the amount of hysteresis in the system. Furthermore, the high amplitude of the instability resulted in significant harmonic components. The behaviour of the harmonics generally resembles the fundamental component, albeit with some notable exceptions.

Characterization and Modeling of a Spinning Thermoacoustic Instability in an Annular Combustor Equipped With Multiple Matrix Injectors

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Jean-François Bourgouin ◽  
Daniel Durox ◽  
Jonas P. Moeck ◽  
Thierry Schuller ◽  
Sébastien Candel
Keyword(s):  
High Speed ◽  
Stable Limit Cycle ◽  
Turbulent Flames ◽  
Linear Growth Rate ◽  
Stable Limit ◽  
Acoustic Oscillations ◽  
Describing Function ◽  
Azimuthal Mode ◽  
Thermoacoustic Instability ◽  
Annular Combustor

Oscillations in fully annular systems coupled by azimuthal modes are often observed in gas turbine combustors but not well documented. One objective of the present study is to characterize this type of oscillation in a laboratory scale system, allowing detailed pressure measurements and high speed visualization of the flame motion. The experiment is designed to allow detailed investigations of this process at a stable limit cycle and for an extended period of time. Experiments reported in the present article are carried out in the MICCA facility which was used in our previous work to analyze instabilities arising when the chamber backplane was equipped with multiple swirling injectors (Bourgouin et al., 2013, “Self-Sustained Instabilities in an Annular Combustor Coupled by Azimuthal Acoustic Modes,” ASME Paper No. GT2013-95010). In the present study, these units are replaced by a set of matrix injectors. The annular plenum feeds 16 such devices confined by two cylindrical quartz tubes open to the atmosphere. The multiple flames formed by the matrix injectors are laminar and have a well documented describing function. This constitutes an ideal configuration allowing systematic investigations of thermo-acoustic oscillations coupled by longitudinal or azimuthal modes while avoiding complexities inherent to swirling turbulent flames studied previously. Optical access to the chamber allows high speed imaging of light emission from the flames providing instantaneous flame patterns and indications on the heat release rate fluctuations. Eight waveguide microphones record the pressure signal at the combustor injection plane and in the plenum. Among the unstable modes observed in this setup, this analysis focuses on situations where the system features a spinning azimuthal mode. This mode is observed at a frequency which is close to that associated with the 1A mode of the plenum. A theoretical analysis is then carried out to interpret the angular shift between the nodal lines in the plenum and chamber, and the measured flame describing function (FDF) is used to quantify this shift and determine the linear growth rate.

scholarly journals Transient Thermoacoustic Responses of Methane/Hydrogen Flames in a Pressurized Annular Combustor

2021 ◽  
Author(s):  
Byeonguk Ahn ◽  
Thomas Indlekofer ◽  
James Dawson ◽  
Nicholas Worth
Keyword(s):  
Equivalence Ratio ◽  
Time History ◽  
High Amplitude ◽  
Transient Growth ◽  
Local Minima ◽  
Driving Mechanisms ◽  
Annular Combustor ◽  
History Of ◽  
Harmonic Components ◽  
Hysteresis Behaviour

Abstract The present article experimentally investigates the triggering and transient growth of azimuthal instabilities in a pressurized laboratory-scale annular combustor featuring twelve methane/hydrogen flames, as the equivalence ratio is ramped up and down. The ramping rate of equivalence ratio is varied to examine its effect on the transient thermoacoustic response and the driving mechanisms, highlighting a number of previously unseen features. As the equivalence ratio is dynamically increased, all cases were observed to feature a distinct modal trajectory, during the onset of high amplitude instabilities. Strongly spinning counter-clockwise modes are first excited before a dynamic transition to strongly spinning clockwise modes occurs. Furthermore, the strength of the spinning mode (quantified through the spin ratio or nature angle) was shown to feature a local minima before the spinning mode stabilized in the system, which corresponds to an almost pure spinning state. Hysteresis behaviour was observed in both the amplitude and nature of the mode, resulting in different thresholds for the onset and decay of the instability, depending on the time history of the combustor. Increasing the ramping rate was found to reduce the amount of hysteresis in the system. Furthermore, the high amplitude of the instability resulted in significant harmonic components. The behaviour of the harmonics generally resembles the fundamental component, albeit with some notable exceptions.

scholarly journals Complexity of a Peroxidase-Oxidase Reaction Model

2021 ◽  
Author(s):  
Jason Gallas ◽  
Marcus Hauser ◽  
Lars Folke Olsen
Keyword(s):  
Chemical Reaction ◽  
Mixed Mode ◽  
Period Doubling ◽  
Reaction Model ◽  
Chaotic Behaviour ◽  
Mixed Mode Oscillations ◽  
Oscillating Reaction ◽  
Oxidase Reaction

The peroxidase-oxidase oscillating reaction was the first (bio)chemical reaction to show chaotic behaviour. The reaction is rich in bifurcation scenarios, from period-doubling to peak-adding mixed mode oscillations. Here, we study...

Bursting patterns and mixed-mode oscillations in reduced Purkinje model

2018 ◽  
Vol 32 (05) ◽  
pp. 1850043 ◽  
Author(s):  
Feibiao Zhan ◽  
Shenquan Liu ◽  
Jing Wang ◽  
Bo Lu
Keyword(s):  
Purkinje Cell ◽  
Mixed Mode ◽  
Cell Model ◽  
Dynamical Behavior ◽  
Characteristic Index ◽  
Mixed Mode Oscillations ◽  
Codimension One ◽  
Bifurcation Phenomenon ◽  
Lyapunov Coefficient ◽  
Potential Link

Bursting discharge is a ubiquitous behavior in neurons, and abundant bursting patterns imply many physiological information. There exists a closely potential link between bifurcation phenomenon and the number of spikes per burst as well as mixed-mode oscillations (MMOs). In this paper, we have mainly explored the dynamical behavior of the reduced Purkinje cell and the existence of MMOs. First, we adopted the codimension-one bifurcation to illustrate the generation mechanism of bursting in the reduced Purkinje cell model via slow–fast dynamics analysis and demonstrate the process of spike-adding. Furthermore, we have computed the first Lyapunov coefficient of Hopf bifurcation to determine whether it is subcritical or supercritical and depicted the diagrams of inter-spike intervals (ISIs) to examine the chaos. Moreover, the bifurcation diagram near the cusp point is obtained by making the codimension-two bifurcation analysis for the fast subsystem. Finally, we have a discussion on mixed-mode oscillations and it is further investigated using the characteristic index that is Devil’s staircase.

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