Swirl effects on harmonically excited, premixed flame kinematics

Acharya, Vishal; Shreekrishna,; Shin, Dong-Hyuk; Lieuwen, Tim

doi:10.1016/j.combustflame.2011.09.015

Cited by 67 publications

(34 citation statements)

References 54 publications

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“…Doing so, we assume that the azimuthal, acoustic velocity u does not affect the response. This last point is proved theoretically in the linear limit for axisymmetric premixed flames in Acharya et al (2012). This influence is experimentally verified to be small at low amplitudes of transverse forcing for the cases of a burner positioned at pressure/velocity nodes and for the case where it is swept by a spinning wave, where both u and v are excited at the same time (Saurabh et al 2014).…”

Section: Flame Responsementioning

confidence: 89%

Weakly nonlinear analysis of thermoacoustic instabilities in annular combustors

2016

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Rotationally symmetric annular combustors are of practical importance because they generically resemble combustion chambers in gas turbines, in which thermoacoustically driven oscillations are a major concern. We focus on azimuthal thermoacoustic oscillations and model the fluctuating heat release rate as being dependent only on the local pressure in the combustion chamber. We study the dynamics of the annular combustor with a finite number of compact flames equispaced around the annulus, and characterize the flames' response with a describing function. We discuss the existence, amplitude and the stability of standing and spinning waves, as a function of: (i) the number of the burners; (ii) the acoustic damping in the chamber; (iii) the flame response. We present the implications for industrial applications and the future direction of investigations. We then present as an example the first theoretical study of thermoacoustic triggering in annular combustors, which shows that rotationally symmetric annular chambers that are thermoacoustically unstable do not experience only stable spinning solutions, but can also experience stable standing solutions. We finally test the theory on one experiment with good agreement.

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Section: Flame Responsementioning

confidence: 89%

Weakly nonlinear analysis of thermoacoustic instabilities in annular combustors

2016

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“…This self-induced vorticity has been superimposed on the acoustic forcing for the computation of Eq. (37). The forcing has been taken as a periodic acoustic wave with a fixed frequency; a vorticity sheet is generated on the wall at the injection plane.…”

Section: Implementation Of the G-equationmentioning

confidence: 99%

“…The way perturbations are produced and transported by or propagating through the flow is also complex to model, in particular, when these disturbances interact with shear layers. [33][34][35][36][37] One explored possibility has been to couple the level-set description of the flame reaction sheet with the Navier-Stokes equations and then compute the response of this flow to excitations. [38][39][40][41] This type of approach, relying on direct simulations of the Navier-Stokes equations, only differs by the way combustion is modeled.…”

Section: Introductionmentioning

confidence: 99%

Response analysis of a laminar premixed M-flame to flow perturbations using a linearized compressible Navier-Stokes solver

Blanchard

Schuller

Sipp³

et al. 2015

Physics of Fluids

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International audienceThe response of a laminar premixed methane-air flame subjected to flow perturbations around a steady state is examined experimentally and using a linearized compressible Navier-Stokes solver with a one-step chemistry mechanism to describe combustion. The unperturbed flame takes an M-shape stabilized both by a central bluff body and by the external rim of a cylindrical nozzle. This base flow is computed by a nonlinear direct simulation of the steady reacting flow, and the flame topology is shown to qualitatively correspond to experiments conducted under comparable conditions. The flame is then subjected to acoustic disturbances produced at different locations in the numerical domain, and its response is examined using the linearized solver. This linear numerical model then allows the componentwise investigation of the effects of flow disturbances on unsteady combustion and the feedback from the flame on the unsteady flow field. It is shown that a wrinkled reaction layer produces hydrodynamic disturbances in the fresh reactant flow field that superimpose on the acoustic field. This phenomenon, observed in several experiments, is fully interpreted here. The additional perturbations convected by the mean flow stem from the feedback of the perturbed flame sheet dynamics onto the flow field by a mechanism similar to that of a perturbed vortex sheet. The different regimes where this mechanism prevails are investigated by examining the phase and group velocities of flow disturbances along an axis oriented along the main direction of the flow in the fresh reactant flow field. It is shown that this mechanism dominates the low-frequency response of the wrinkled shape taken by the flame and, in particular, that it fully determines the dynamics of the flame tip from where the bulk of noise is radiated

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“…Recent work has shown that several paths exist through which a transverse mode may excite a flame [23][24][25][26]. As shown in Figure 2, transverse modes can directly excite the flame, they can excite hydrodynamic flow instabilities, and they can also lead to axial acoustic flow oscillations in the nozzle.…”

Section: Figurementioning

confidence: 99%

Transverse to Longitudinal Acoustic Coupling Processes in Annular Combustion Chambers

Blimbaum

Zanchetta

Akin

et al. 2012

International Journal of Spray and Combustion Dynamics

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Combustion instability is a major issue facing lean, premixed combustion approaches in modern gas turbine applications. This paper specifically focuses on instabilities that excite transverse acoustic modes of the combustion chamber. Recent simulation and experimental studies have shown that much of the flame response during transverse instabilities is due to the longitudinal fluid motions induced by the fluctuating pressure field above a nozzle. In this study, we analyze the multi-dimensional acoustic field excited by transverse acoustic disturbances interacting with an annular side branch, emulating a fuel/air mixing nozzle. Key findings of this work show that the resultant velocity fields are critically dependent upon the structure of the transverse acoustic field and the nozzle impedance. Significantly, we also show that certain cases can be understood from relatively simple quasi one-dimensional considerations, but that other cases are intrinsically three-dimensional.

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Swirl effects on harmonically excited, premixed flame kinematics

Cited by 67 publications

References 54 publications

Weakly nonlinear analysis of thermoacoustic instabilities in annular combustors

Weakly nonlinear analysis of thermoacoustic instabilities in annular combustors

Response analysis of a laminar premixed M-flame to flow perturbations using a linearized compressible Navier-Stokes solver

Transverse to Longitudinal Acoustic Coupling Processes in Annular Combustion Chambers

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