Journal: Combustion and Flame

Abbreviation

Comb Flame

Publisher

Elsevier

Journal Volumes

ISSN

0010-2180
1556-2921

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Publications 1 - 10 of 70
  • Flame dynamics in lean premixed CO/H2/air combustion in a mesoscale channel
    Item type: Journal Article
    Brambilla, Andrea; Frouzakis, Christos E.; Mantzaras, John; et al. (2014)
    Combustion and Flame
    The dynamics and stabilization of fuel lean premixed CO / H2/air atmospheric pressure flames in meso-scale channels were investigated numerically, using detailed gas phase chemistry and transport. Experiments in a channel flow reactor by means of chemiluminescence detection of the excited OH radical allowed for model validation at steady conditions and identification of the conditions at which unsteady flame dynamics were present. A detailed parametric study of the influence of wall temperature and CO : H2 ratio on the ensuing flame dynamics was performed. The numerical results revealed different flame modes which included oscillatory ignition, random ignition spots, as well as steady weak and V-shaped flames. The wall temperature stability intervals of these modes changed with the CO : H2 ratio. The richest variety was found for molar CO : H2 ratios between 4 and 10, while at lower ratios the random and the weak modes were absent. At higher ratios all the dynamic modes were suppressed. The Computational Singular Perturbation (CSP) method was used to obtain insights into the physicochemical processes responsible for the weak flames, which were found at relatively high inflow velocities compared to previous studies, and V-shaped flames. A kinetic explanation of the phenomena was supported by the CSP analysis.
  • Reactive Parametrized Scalar Profile (R-PSP) Mixing Model for Partially Premixed Combustion
    Item type: Journal Article
    Hegetschweiler, Michael; Zoller, Benjamin; Jenny, Patrick (2012)
    Combustion and Flame
  • Direct measurement of entrainment during nanoparticle synthesis in spray flames
    Item type: Journal Article
    Pratsinis, Sotiris E.; Heine, Martin C.; Maedler, Lutz; et al. (2006)
    Combustion and Flame
  • Intrinsic thermoacoustic modes in an annular combustion chamber
    Item type: Journal Article
    Buschmann, Philip E.; Mensah, Georg A.; Moeck, Jonas P. (2020)
    Combustion and Flame
  • Surface growth, coagulation and oxidation of soot by a monodisperse population balance model
    Item type: Journal Article
    Kholghy, M.Reza; Kelesidis, Georgios A. (2021)
    Combustion and Flame
    A monodisperse population balance model (MPBM) is developed here that capitalizes on the rapid attainment of the self-preserving size distribution and asymptotic fractal-like structure of agglomerates by coagulation to simulate their evolution with only three equations. Total agglomerate carbon molar, , number () and area () concentrations are tracked. The model accounts for the polydispersity of agglomerates by enhancing their collision frequency by that of their self-preserving size distribution based on the radius of gyration in the free molecular regime. Scaling laws from detailed discrete element modeling (DEM) simulations are used to describe the fractal-like morphology of the agglomerates. The MPBM predicts the evolution of soot , and average mobility and primary particle diameters during surface growth and agglomeration in laminar premixed ethylene flames as well as soot oxidation in a tube reactor within 30% of detailed DEM, sectional population balance simulations and measurements. Thus, when self-preserving size distribution and asymptotic structure of agglomerates are attained, this simple MPBM has unprecedented accuracy and can be readily interfaced with computational fluid dynamic (CFD) to model soot formation in combustion devices or process design and optimization for the synthesis of carbonaceous agglomerate nanoparticles.
  • Numerical study of nitrogen oxides chemistry during plasma assisted combustion in a sequential combustor
    Item type: Journal Article
    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.
  • Morphology, composition and optical properties of jet engine-like soot made by a spray flame
    Item type: Journal Article
    Kholghy, M. Reza; DeRosa, Valentina G. (2021)
    Combustion and Flame
    Particulate matter (PM) and soot emissions from aviation are a major source of pollution. Reference soot is needed for calibration of optical instruments used for measurements of non-volatile PM (nvPM) from jet engines with average mobility, d¯ , and primary particle, d¯ , diameters less than 70 and 20 nm, respectively, mass mobility exponent (D ) of 2.5±0.15, elemental to total carbon ratio (EC/TC) larger than 0.8, and mass absorption cross section (MAC) of 7.46±0.27m /g at 532 nm. Such particles are difficult to make with gas-fueled soot generators using laminar flames with high temperature particle residence times quite different from those of jet engine combustors. Here, a flame spray pyrolysis (FSP) burner is used to generate soot agglomerates from turbulent flames made by spraying liquid jet fuel. The d¯ of FSP-made soot agglomerates is modified from less than 13 to more than 91 nm by changing common process parameters while agglomerates maintain EC/TC > 0.8. The FSP-made soot agglomerates with D ~ 2.52±0.2 have effective densities similar to emissions from turbofan and turboshaft engines and MAC=8.23 and 5.21(m /g) at 532 and 870 nm, respectively, in excellent agreement with recent measurements of nvPM emissions from jet engine turbines.
  • The mechanism by which CH2O and H2O2 additives affect the autoignition of CH4/air mixtures
    Item type: Journal Article
    Manias, Dimitris M.; Tingas, Efstathios A.; Frouzakis, Christos E.; et al. (2015)
    Combustion and Flame
  • Air-blast atomization and ignition of a kerosene spray in hot vitiated crossflow
    Item type: Journal Article
    Miniero, Luigi; Pandey, Khushboo; Fredrich, Daniel; et al. (2023)
    Combustion and Flame
    Increasingly stringent regulations of pollutant emissions from aviation require rapid implementation of novel combustion technologies. Promising concepts based on moderate or intense low-oxygen dilution (MILD) combustion have been investigated in academia and industry. This MILD regime can be obtained from the recirculation of the hot vitiated combustion products to raise the temperature of the reactants, resulting in distributed reaction regions and lower flame temperatures. In the present work, we consider the air-blast atomization of a kerosene spray in crossflow, which enables efficient mixing between fuel and oxidizer. We investigate experimentally and numerically the effect of the spray air-to-liquid mass-flow ratio (ALR) variation on the reaction front and flame topology of a kerosene spray flame. The spray is injected transversely into a turbulent vitiated crossflow composed of the products of a lean CH4-H2 flame. The spray flame thermal power is varied between 2.5 and 5 kW, along with the atomizer ALR between 2 and 6. The experimental characterization of the reaction zone is performed using OH* chemiluminescence and OH and fuel planar laser-induced fluorescence (PLIF). The Large Eddy Simulations (LES) of the multiphase reactive flow provide good agreement with the experimental observations. Experiments and simulations show that the ALR governs mixing, resulting in different flame stabilization mechanisms and combustion regimes. Low ALR results in a relatively small jet-to-crossflow momentum ratio and a large spray Sauter mean diameter (SMD). A thick windward reaction region is formed due to inefficient shear layer mixing between the fuel spray and the crossflow. Meanwhile, the correspondingly large spray SMD leads to isolated penetration and localized combustion of fuel clusters. At high ALR, the higher penetration and the faster droplet evaporation due to the lower spray SMD result in an efficient entrainment-induced mixing between the two streams, forming more distributed reaction regions.
  • The Role of Ferrocene in Flame Synthesis of Silica
    Item type: Journal Article
    Fotou, George P.; Scott, Steven J.; Pratsinis, Sotiris E. (1995)
    Combustion and Flame
Publications 1 - 10 of 70