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Daniel Durox

Bio: Daniel Durox is an academic researcher from Université Paris-Saclay. The author has contributed to research in topics: Premixed flame & Combustion. The author has an hindex of 46, co-authored 129 publications receiving 6760 citations. Previous affiliations of Daniel Durox include Supélec & Centre national de la recherche scientifique.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors used the flame describing function (FDF) to investigate the nonlinear stability of burners by associating the FDF with a frequency-domain analysis of the burner acoustics.
Abstract: Analysis of combustion instabilities relies in most cases on linear analysis but most observations of these processes are carried out in the nonlinear regime where the system oscillates at a limit cycle. The objective of this paper is to deal with these two manifestations of combustion instabilities in a unified framework. The flame is recognized as the main nonlinear element in the system and its response to perturbations is characterized in terms of generalized transfer functions which assume that the gain and phase depend on the amplitude level of the input. This 'describing function' framework implies that the fundamental frequency is predominant and that the higher harmonics generated in the nonlinear element are weak because the higher frequencies are filtered out by the other components of the system. Based on this idea, a methodology is proposed to investigate the nonlinear stability of burners by associating the flame describing function with a frequency-domain analysis of the burner acoustics. These elements yield a nonlinear dispersion relation which can be solved, yielding growth rates and eigenfrequencies, which depend on the amplitude level of perturbations impinging on the flame. This method is used to investigate the regimes of oscillation of a well-controlled experiment. The system includes a resonant upstream manifold formed by a duct having a continuously adjustable length and a combustion region comprising a large number of flames stabilized on a multipoint injection system. The growth rates and eigenfrequencies are determined for a wide range of duct lengths. For certain values of this parameter we find a positive growth rate for vanishingly small amplitude levels, indicating that the system is linearly unstable. The growth rate then changes as the amplitude is increased and eventually vanishes for a finite amplitude, indicating the existence of a limit cycle. For other values of the length, the growth rate is initially negative, becomes positive for a finite amplitude and drops to zero for a higher value. This indicates that the system is linearly stable but nonlinearly unstable. Using calculated growth rates it is possible to predict amplitudes of oscillation when the system operates on a limit cycle. Mode switching and instability triggering may also be anticipated by comparing the growth rate curves. Theoretical results are found to be in excellent agreement with measurements, indicating that the flame describing function (FDF) methodology constitutes a suitable framework for nonlinear instability analysis.

475 citations

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TL;DR: In this paper, the authors describe the processes that can be involved in the development of combustion instabilities in gas turbine combustors and highlight typical paths to help in the understanding of the multiple links that can exist between elementary processes.
Abstract: Elementary processes that can be involved in the development of combustion instabilities in gas turbine combustors are described. The premixed mode of combustion is considered more specie cally because it is used in most advanced gas turbine systems. The processes envisaged portray the combustion dynamics of real systems, but they are analyzed in simple laboratory cone gurations. Among the many possible interactions, the most relevant mechanisms are those that generate e uctuations in heat release or induce pressure perturbations. Some typical paths are highlighted to help in the understanding of the multiple links that can exist between elementary processes. Processes involving acoustic/e ame coupling, unsteady strain rates, e ame response to inhomogeneities, interactions of e ames with boundaries, and e ame/vortex interactions are specie cally examined. For each process, a driving or a coupling path is proposed relating heat release e uctuations to acoustic variables in certain cases or leading from acoustic variables to heat release e uctuations in other cases. Stress is also put on characteristic time lags, which are key parameters in the triggering and development of instabilities. Well-controlled experiments illustrate the many possibilities and can serve to guide the modeling effort and to validate computational tools for combustion dynamics.

454 citations

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TL;DR: In this paper, convective effects of the flow modulations propagating upstream of a premixed laminar flame are considered and a unified model is derived analytically, based on a linearization of the G-equation for an inclined flame.

446 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the dynamics of premixed confined swirling flames by examining their response to incident velocity perturbations and determined the generalized transfer function designated as the flame describing function (FDF) by sweeping a frequency range extending from 0 to 400 Hz and by changing the root mean square fluctuation level between 0% and 72% of the bulk velocity.

351 citations

Journal ArticleDOI
01 Jan 2000
TL;DR: In this article, the authors investigated the dynamical behavior of laminar premixed flames and derived a transfer function relating the flow velocity modulations and the heat release fluctuations, which can be used to describe the response of the burner to acoustic modulation, knowing its geometry and the flame properties.
Abstract: The dynamical behavior of laminar premixed flames is investigated in this article. The flame response to incident perturbations is characterized with a transfer function relating the flow velocity modulations and the heat release fluctuations. This function is obtained using the assumptions introduced in previous studies by Fleifil et al. , but the model is extended to account for any flame angle (i.e., any operating condition). The modeling shows that phenomena can be described using a single control parameter taking the form of a reduced frequency ω* . This quantity is derived as ωR/S L cos α 0 , where ω is the angular frequency, R is the burner radius S L is the laminar burning velocity, and α 0 is the half-cone angle of the steady flame. this parameter may be used to describe the response of the burner to acoustic modulation, knowing its geometry and the flame properties. Two characteristic times have been determined. The first one defines the cut-off frequency of the low-pass filter associated with the flame response. The second one enables the prediction of the time lag between the velocity modulation at the burner exit and the flame heat release the exact transfer function and an approximation in the form of a first-order model are compared with an extensive set of experimental data corresponding to a range of equivalence ratios and two burner diameters. Good agreement is obtained for low values of the reduced frequency. In an intermediate range of frequencies, the experimental phase exceeds the theoretical values by a significant amount, the difference between theory and experiment is due to the simplifying assumptions used in the model.

329 citations


Cited by
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TL;DR: A comprehensive review of the advances made over the past two decades in this area is provided in this article, where various swirl injector configurations and related flow characteristics, including vortex breakdown, precessing vortex core, large-scale coherent structures, and liquid fuel atomization and spray formation are discussed.

1,048 citations

Journal ArticleDOI
TL;DR: The history and basic formulation of WENO schemes are reviewed, the main ideas in using WenO schemes to solve various hyperbolic PDEs and other convection dominated problems are outlined, and a collection of applications in areas including computational fluid dynamics, computational astronomy and astrophysics, semiconductor device simulation, traffic flow models, computational biology, and some non-PDE applications are presented.
Abstract: High order accurate weighted essentially nonoscillatory (WENO) schemes are relatively new but have gained rapid popularity in numerical solutions of hyperbolic partial differential equations (PDEs) and other convection dominated problems. The main advantage of such schemes is their capability to achieve arbitrarily high order formal accuracy in smooth regions while maintaining stable, nonoscillatory, and sharp discontinuity transitions. The schemes are thus especially suitable for problems containing both strong discontinuities and complex smooth solution features. WENO schemes are robust and do not require the user to tune parameters. At the heart of the WENO schemes is actually an approximation procedure not directly related to PDEs, hence the WENO procedure can also be used in many non-PDE applications. In this paper we review the history and basic formulation of WENO schemes, outline the main ideas in using WENO schemes to solve various hyperbolic PDEs and other convection dominated problems, and present a collection of applications in areas including computational fluid dynamics, computational astronomy and astrophysics, semiconductor device simulation, traffic flow models, computational biology, and some non-PDE applications. Finally, we mention a few topics concerning WENO schemes that are currently under investigation.

831 citations

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TL;DR: A comprehensive overview of the progress and the gap in the knowledge of plasma assisted combustion in applications, chemistry, ignition and flame dynamics, experimental methods, diagnostics, kinetic modeling, and discharge control is provided in this paper.

812 citations

Journal ArticleDOI
01 Jan 2002
TL;DR: A broad survey of combustion research can be found in this article, where a number of closed loop feedback concepts are used to improve the combustion process as demonstrated by applications to automotive engines.
Abstract: Combustion dynamics constitutes one of the most challenging areas in combustion research. Many facets of this subject have been investigated over the past few decades for their fundamental and practical implications. Substantial progress has been accomplished in understanding analysis, modeling, and simulation. Detailed laboratory experiments and numerical computations have provided a wealth of information on elementary dynamical processes such as the response of flames to variable strain, vortex rollup, coupling between flames and acoustic modulations, and perturbed flame collisions with boundaries. Much recent work has concerned the mechanisms driving instabilities in premixed combustion and the coupling between pressure waves and combustion with application to the problem of instability in modern low NO x heavyduty gas turbine combustors. Progress in numerical modeling has allowed simulations of dynamical flames interacting with pressure waves. On this basis, it has been possible to devise predictive methods for instabilities. Important efforts have also been directed at the development of the related subject of combustion control. Research has focused on methods, sensors, actuators, control algorithms, and systems integration. In recent years, scaling from laboratory experiments to practical devices has been achieved with some successebut limitations have also been revealed. Active control of combustion has also evolved in various directions. A number of experiments on laboratory-scale combustors have shown that the amplitude of combustion instabilities could be reduced by applying control principles. Full-scale terrestrial application to gas turbine systems have allowed an increase of the stability margin of these machines. Feedback principles are also being explored to control the point of operation of combustors and engines. Operating point control has special importance in the gas turbine field since it can be used to avoid operation in unstable regions near the lean blowoff limits. More generally, closed loop feedback concepts are useful if one wishes to improve the combustion process as demonstrated by applications to automotive engines. Many future developments of combustion will use such concepts for tuning, optimization, and emissions reduction. This article proposes a broad survey of these fast-moving areas of research.

726 citations

Journal ArticleDOI
TL;DR: In this article, the authors used direct numerical simulation (DNS) to predict the flamelet structure and the burning velocity of premixed turbulent combustion and showed that the results were valid even for highly turbulent flames.

703 citations