Quentin Malé

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Malé

First Name

Quentin

ORCID

0000-0002-1890-808X

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Publications 1 - 6 of 6

Numerical Study of Ignition and Combustion of Hydrogen-Enriched Methane in a Sequential Combustor
Impagnatiello, Matteo; Malé, Quentin; Noiray, Nicolas (2024)
Flow, Turbulence and Combustion
gnition and combustion behavior in the second stage of a sequential combustor are investigated numerically at atmospheric pressure for pure CH₄ fueling and for two CH₄-H₂ fuel blends in 24:1 and 49:1 mass ratios , respectively, using Large Eddy Simulation (LES). Pure CH₄ fueling results in a turbulent propagating flame anchored by the hot gas recirculation zones developed near the inlet of the sequential combustion chamber. As the H₂ content increases, the combustion process changes drastically, with multiple auto-ignition kernels produced upstream of the main flame brush. Analysis of the explosive modes indicates that, for the highest H₂ amount investigated, flame stabilization in the combustion chamber is strongly supported by auto-ignition chemistry. The analysis of fuel decomposition pathways highlights that radicals advected from the first stage flame, in particular OH, induce a rapid fuel decomposition and cause the reactivity enhancement that leads to auto-ignition upstream of the sequential flame. This behavior is promoted by the relatively large mass fraction of OH radicals found in the flow reaching the second stage, which is approximately one order of magnitude greater than it would be at chemical equilibrium. The importance of the out-of-equilibrium vitiated air on the ignition behavior is proven via an additional LES that features weak auto-ignition kernel formation when equilibrium is artificially imposed. It is therefore concluded that parameters affecting the relaxation towards chemical equilibrium of the vitiated flow can have an important influence on the operability of sequential combustors fueled with varying fractions of H₂ blending.
Acoustic scattering of a sequential combustor controlled with non-equilibrium plasma: A numerical study
Impagnatiello, Matteo; Malé, Quentin; Noiray, Nicolas (2024)
Proceedings of the Combustion Institute
This study aims to investigate the impact of Nanosecond Repetitively Pulsed Discharges (NRPDs) on the acoustic scattering properties of the second stage of a Constant Pressure Sequential Combustor (CPSC). Despite the proven capability of NRPDs to stabilize such systems, a comprehensive understanding of the NRPDs-flame-acoustic interaction is lacking. To address this knowledge gap, Large Eddy Simulations (LESs) with state-of-the-art plasma modeling are combined with methods from system identification to characterize the system's acoustic response both in the absence and presence of NRPDs. The results demonstrate that NRPDs initiate reacting kernels upstream of the second stage combustion chamber, which interact with the acoustic field and with the main flame brush, thereby significantly impacting the scattering matrix coefficients. An analysis of the system's acoustic power amplification characteristics in absence of NRPDs underscores the system's capability to amplify the incident acoustic power between 300 and 450 Hz, up to a maximum of +160%. This highlights the potential of the second stage to drive system destabilization. In contrast, with NRPDs, the system's response is more balanced, with maximum amplification factor consistently below +25% across the entire spectrum. To shed light on this behavior, the relation between heat release rate and pressure fluctuations is examined at 327 Hz. As opposed to the main flame brush, plasma-induced kernels generate heat release fluctuations that are out-of-phase with the pressure fluctuations. Hence, NRPDs induce a drastic reduction in the component of the sequential stage heat release fluctuations that is coherent with the acoustic field and participates to the acoustic power amplification, thanks to the change in the flame morphology they induce.
Hydrogen reaction rate modeling based on convolutional neural network for large eddy simulation
Malé, Quentin; Lapeyre, Corentin J.; Noiray, Nicolas (2025)
Data-Centric Engineering
This article establishes a data-driven modeling framework for lean hydrogen (H2)-air reaction rates for the Large Eddy Simulation (LES) of turbulent reactive flows. This is particularly challenging since H2 molecules diffuse much faster than heat, leading to large variations in burning rates, thermodiffusive instabilities at the subfilter scale, and complex turbulence-chemistry interactions. Our data-driven approach leverages a Convolutional Neural Network (CNN), trained to approximate filtered burning rates from emulated LES data. First, five different lean premixed turbulent H2-air flame Direct Numerical Simulations (DNSs) are computed each with a unique global equivalence ratio. Second, DNS snapshots are filtered and downsampled to emulate LES data. Third, a CNN is trained to approximate the filtered burning rates as a function of LES scalar quantities: progress variable, local equivalence ratio, and flame thickening due to filtering. Finally, the performances of the CNN model are assessed on test solutions never seen during training. The model retrieves burning rates with very high accuracy. It is also tested on two filter and downsampling parameters and two global equivalence ratios between those used during training. For these interpolation cases, the model approximates burning rates with low error even though the cases were not included in the training dataset. This a priori study shows that the proposed data-driven machine learning framework is able to address the challenge of modeling lean premixed H2-air burning rates. It paves the way for a new modeling paradigm for the simulation of carbon-free hydrogen combustion systems.
Numerical study of nitrogen oxides chemistry during plasma assisted combustion in a sequential combustor
Malé, Quentin; Barléon, Nicolas; Shcherbanev, Sergey; et al. (2024)
Combustion and Flame
Plasma Assisted Combustion (PAC) is a promising technology to enhance the combustion of lean mixtures prone to instabilities and flame blow-off. Although many PAC experiments demonstrated combustion enhancement, several studies report an increase in NOx emissions. The aim of this study is to determine the kinetic pathways leading to NOx formation in the second stage of a sequential combustor assisted by Nanosecond Repetitively Pulsed Discharges (NRPDs). For this purpose, Large Eddy Simulation (LES) associated with an accurate description of the combustion/NOx chemistry and a phenomenological model of the plasma kinetics is used. Detailed kinetics 0-Dimensional reactors complement the study. First, the LES setup is validated by comparison with experiments. Then, the NOx chemistry is analyzed. For the conditions of operation studied, it is shown that the production of atomic nitrogen in the plasma by direct electron impact on nitrogen molecules increases the formation of NO. Then, the NO molecules are transported through the turbulent flame without being strongly affected. This study illustrates the need to limit the diatomic nitrogen dissociation process in order to mitigate harmful emissions. More generally, the very good agreement with experimental measurements demonstrates the capability of LES combined with accurate models to predict the NRPD effects on both turbulent combustion and NOx emissions.
Stabilization of a thermoacoustically unstable sequential combustor using non-equilibrium plasma: Large eddy simulation and experiments
Malé, Quentin; Shcherbanev, Sergey; Impagnatiello, Matteo; et al. (2024)
Proceedings of the Combustion Institute
Plasma-assisted combustion using Nanosecond Repetitively Pulsed Discharges (NRPDs) is an emerging technology that enhances the reactivity of fuel–air mixtures, offering significant improvements in operational and fuel flexibility—two crucial features for future sustainable gas turbines. The mechanisms that enable the stabilization of thermoacoustically unstable burners, however, remain unclear. Thus, to investigate the physical phenomena involved, we performed a massively parallel Large Eddy Simulation (LES) of the stabilization of a thermoacoustically unstable sequential combustor by NRPDs at atmospheric pressure. LES is combined with an accurate description of the combustion chemistry and a state-of-the-art phenomenological model for the non-equilibrium plasma effects. In this work, we have validated the simulation framework by comparison with experimental data including acoustic pressure and Heat Release Rate (HRR) signals in both stages of the sequential combustor, and OH-planar laser-induced fluorescence images in the second stage combustion chamber. Hence, this study provides a robust LES framework to study the effects of NRPDs on Thermoacoustic Instabilities (TIs). In addition, the analysis of the LES data reveals a significant decrease of the acoustic energy production in the sequential combustor thanks to the NRPDs. Surprisingly, the steady NRPD actuation generates HRR fluctuations upstream of the combustion chamber, which are in phase opposition to the acoustic pressure, inducing locally a sink term in the acoustic energy balance equation. Moreover, an analysis of the acoustic energy production during the onset of the TI reveals the predominant role of the second stage in developing and sustaining the self-excited TI. The effect of plasma is therefore very effective in stabilizing the system by reducing the acoustic energy production in the sequential stage.
The LEAF concept operated with hydrogen: Flame topology and NOₓ formation
Malé, Quentin; Pandey, Khushboo; Noiray, Nicolas (2024)
Proceedings of the Combustion Institute
The development of low NOₓ hydrogen (H₂) burners is crucial for the sustainability target of the power/propulsion sector. However, the technical difficulty of burning H₂ at low NOₓ emissions is challenging for the combustion community. Recently, the concept of LEan Azimuthal Flame (LEAF) has demonstrated promising results for low NOₓ kerosene/hydrogen combustion by rapidly diluting the reactants with burnt gas and fresh oxidizer. However, there is a lack of understanding of the flame dynamics and the NOₓ formation routes for H₂ LEAF. We therefore carried out a joint experimental and numerical study of the LEAF combustor at atmospheric pressure fueled with H₂. Experiments are based on OH-planar laser-induced fluorescence and exhaust gas analysis. Numerical results are based on massively parallel Large Eddy Simulation (LES) with an accurate description of the combustion and NOₓ chemistry. This study focuses on understanding the effects of the Air Ratio (AR), which defines the distribution of the air injected from the top and the bottom of the LEAF combustor. The LES results are in excellent agreement with the experimental data in terms of flame topology and exhaust emissions. A dual flame structure is observed when rich premixed gas is injected from the bottom together with air from the top, leading to the coexistence of premixed and non-premixed combustion regimes. An optimum AR is identified to minimize NOₓ emissions. It is attributed to the enhancement of the azimuthal whirling flow by the air injected from the bottom, having higher momentum than pure H₂ injection only.

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Quentin Malé

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