Flame sheet dynamics of bluff-body stabilized flames during longitudinal acoustic forcing

2009 ◽  
Vol 32 (2) ◽  
pp. 1787-1794 ◽  
Author(s):  
Santosh Shanbhogue ◽  
Dong-Hyuk Shin ◽  
Santosh Hemchandra ◽  
Dmitriy Plaks ◽  
Tim Lieuwen
Keyword(s):  
Bluff Body ◽  
Longitudinal Acoustic ◽  
Acoustic Forcing ◽  
Stabilized Flames ◽  
Flame Sheet

Response of a Rod Stabilized, Premixed Flame to Longitudinal Acoustic Forcing

2006 ◽  
Author(s):  
Santosh J. Shanbhogue ◽  
Tim C. Lieuwen
Keyword(s):  
Experimental Investigation ◽  
Flame Front ◽  
Coherent Structures ◽  
Large Scale ◽  
Bluff Body ◽  
Premixed Flame ◽  
Longitudinal Acoustic ◽  
Harmonic Response ◽  
Flame Sheet ◽  
Bluff Body Wake

This paper describes an experimental investigation of the flame sheet dynamics of an acoustically forced bluff body flame over a range of perturbation frequencies and amplitudes. When acoustically excited, the flame sheet displays well defined, periodic corrugations, presumably due to flame sheet perturbations created at its attachment point that convect downstream, as well as the rollup of shear layer instabilities into large scale coherent structures. The dynamics of the flame front response, such as its growth and decay in the bluff body wake, disturbance convection velocity, sub-harmonic response, and total flame area is discussed.

Impact of Precessing Vortex Core Dynamics on Shear Layer Response in a Swirling Jet

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Mark Frederick ◽  
Kiran Manoharan ◽  
Joshua Dudash ◽  
Brian Brubaker ◽  
Santosh Hemchandra ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Shear Layer ◽  
Linear Stability ◽  
Linear Stability Analysis ◽  
Vortex Core ◽  
Combustion Instability ◽  
Forced Response ◽  
Longitudinal Acoustic ◽  
Precessing Vortex Core ◽  
Acoustic Forcing

Combustion instability, the coupling between flame heat release rate oscillations and combustor acoustics, is a significant issue in the operation of gas turbine combustors. This coupling is often driven by oscillations in the flow field. Shear layer roll-up, in particular, has been shown to drive longitudinal combustion instability in a number of systems, including both laboratory and industrial combustors. One method for suppressing combustion instability would be to suppress the receptivity of the shear layer to acoustic oscillations, severing the coupling mechanism between the acoustics and the flame. Previous work suggested that the existence of a precessing vortex core (PVC) may suppress the receptivity of the shear layer, and the goal of this study is to first, confirm that this suppression is occurring, and second, understand the mechanism by which the PVC suppresses the shear layer receptivity. In this paper, we couple experiment with linear stability analysis to determine whether a PVC can suppress shear layer receptivity to longitudinal acoustic modes in a nonreacting swirling flow at a range of swirl numbers. The shear layer response to the longitudinal acoustic forcing manifests as an m = 0 mode since the acoustic field is axisymmetric. The PVC has been shown both in experiment and linear stability analysis to have m = 1 and m = −1 modal content. By comparing the relative magnitude of the m = 0 and m = −1,1 modes, we quantify the impact that the PVC has on the shear layer response. The mechanism for shear layer response is determined using companion forced response analysis, where the shear layer disturbance growth rates mirror the experimental results. Differences in shear layer thickness and azimuthal velocity profiles drive the suppression of the shear layer receptivity to acoustic forcing.

Extinction Conditions of Low-Speed Ballistic Bluff-Body Stabilized Flames

2017 ◽  
Author(s):  
Christian Engelmann ◽  
Marissa K. Geikie ◽  
Anthony J. Morales ◽  
Kareem Ahmed
Keyword(s):  
Bluff Body ◽  
Low Speed ◽  
Stabilized Flames

Review and Analysis of Bluff Body Flame Stabilization Data

2008 ◽  
Author(s):  
Sajjad A. Husain ◽  
Ganesh Nair ◽  
Santosh Shanbhogue ◽  
Tim C. Lieuwen
Keyword(s):  
Activation Energy ◽  
Kinetic Modeling ◽  
First Principles ◽  
Bluff Body ◽  
Large Range ◽  
Flame Stabilization ◽  
Local Extinction ◽  
Data Set ◽  
Flame Sheet ◽  
Semi Empirical

This paper compiles and analyzes bluff body stabilized flame blowoff data from the literature. Many of these studies contain semi-empirical blowoff correlations that are, in essence, Damko¨hler number correlations of their data. This paper re-analyzes these data, utilizing various Damko¨hler number correlations based upon detailed kinetic modeling for determining chemical time scales. While the results from this compilation are similar to that deduced from many earlier studies, it demonstrates that a rather comprehensive data set taken over a large range of conditions can be correlated from “first-principles” based calculations that do not rely on empirical fits or adjustable constants (e.g., global activation energy or pressure exponents). The paper then discusses the implications of these results on understanding of blowoff. Near blowoff flames experience local extinction of the flame sheet, manifested as “holes” that form and convect downstream. However, local extinction is distinct from blowoff — in fact, under certain conditions the flame can apparently persist indefinitely with certain levels of local extinction. We hypothesize that simple Damko¨hler number correlations contain the essential physics describing this first stage of blowoff; i.e., they are correlations for the conditions where local extinction on the flame begins, but do not fundamentally describe the ultimate blowoff condition itself. However, such correlations are reasonably successful in correlating blowoff limits because the ultimate blowoff event appears to be correlated to some extent to the onset of this first stage.

scholarly journals Joint Scalar versus Joint Velocity-Scalar PDF Simulations of Bluff-Body Stabilized Flames with REDIM

2008 ◽  
Vol 82 (2) ◽  
pp. 185-209 ◽  
Author(s):  
B. Merci ◽  
B. Naud ◽  
D. Roekaerts ◽  
U. Maas
Keyword(s):  
Bluff Body ◽  
Stabilized Flames ◽  
Joint Velocity
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