首页期刊导航|Combustion and flame
期刊信息/Journal information
Combustion and flame
ButterWorths
Combustion and flame

ButterWorths

0010-2180

Combustion and flame/Journal Combustion and flameSCIISTP
正式出版
收录年代

    An experimental and modeling study of hydrogen/ n -decane blends

    Zhou, ShangkunMohamed, A. Abd El-SaborNagaraja, Shashank S.Wang, Pengzhi...
    1.1-1.9页
    查看更多>>摘要：In this study, a new mechanism is developed to simulate hydrogen/n-decane blends. It is validated in the temperature range 650-1500 K, at p = 30 bar, for equivalence ratios of 0.5, 1.0, and 2.0 in 'air' for 99/1, 95/5 and 80/20 (mol%) blends of hydrogen/n-decane using ignition delay time (IDT) data recorded in both an RCM and in a shock tube. Additionally, the mechanism's performance is assessed against existing literature data for both pure hydrogen and pure n-decane, demonstrating overall satisfactory agreement compared to the experimental measurements. This study also explores the effects of n-decane addition to hydrogen at different temperatures (600 K, 900 K, and 1500 K) at p = 30 bar pressure for a stoichiometric mixture (phi = 1.0). At 600 K, where pure hydrogen fails to ignite, the introduction of 1% n-decane initiates ignition, albeit with considerably extended IDTs. At 900 K, the addition of 1% n-decane enhances reactivity, while at 1500 K, it diminishes reactivity and extends the IDT. The underlying reasons for these observed effects are reported. We provide valuable insights into the reactivity of dual fuel mixtures of hydrogen and n-decane encompassing low (600-800 K), intermediate (800-1200 K), and high (> 1200 K) temperature ranges. At low and intermediate temperatures, the inclusion of n-decane enhances reactivity. Consequently, for application in practical road transport combustion systems, the use of n-decane or extended-chain n-alkanes is recommended as suitable pilot fuels. Conversely, at high-temperature combustion conditions, the utilization of pilot fuels composed of linear alkanes is observed to impede reactivity.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    Fuel mobility dynamics and their influence on applied smouldering systems

    Miry, Seyed ZiaedinZanoni, Marco A. B.Rashwan, Tarek L.Kinsman, Laura...
    1.1-1.16页
    查看更多>>摘要：Many recent environmentally beneficial applications of smouldering treat hazardous organic liquid fuels in inert porous media. In these applications, organic liquid mobilization can affect the treatment process, and the dynamics are poorly understood. Organic liquid mobilization is therefore a key knowledge gap that hinders the optimization of applied smouldering. This is especially the case in large scales where mobilization appears to be more significant. Liquid mobilization inside a porous medium cannot be easily measured directly, therefore numerical modelling is essential to understand the fundamental processes and to clarify the effects and dynamics of the fuel mobilization on the smouldering reaction. Contrasting numerical models with experimental temperature measurements have revealed many aspects of smouldering that cannot be measured. In this study, a previously developed 1D smouldering model was equipped with multiphase flow equations and compared against laboratory column experiments. The combination of model and experiments has served to quantify the dynamics of organic liquid fuel mobility by simulating high (i.e., non-mobile) and low (i.e., mobile) viscous fuels. The findings from this study shed light on the complicated interplay between multiphase flow, heat and mass transfer, and smoulder chemistry common to many applied smouldering systems. Numerical results confirmed that increasing the viscosity results in fuel remaining in the reaction zone and led to an increase in the peak temperature and smouldering front velocities. Lower viscosity fuels mobilized away from the reaction zone, thereby accumulating fuel in the pre-heating zone of the reactor. The fundamental understanding generated from this research will improve the design, implementation, and optimization of smouldering-based technologies for environmentally beneficial applications worldwide.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    Experimental and numerical study of soot formation in laminar n-butylcyclohexane and n-butylbenzene diffusion flames at elevated pressures

    Lyu, ZekangYan, TongtongQian, YongCen, Liulin...
    1.1-1.12页
    查看更多>>摘要：The soot formation characteristics of laminar nitrogen-diluted n-butylcyclohexane and n-butylbenzene diffusion flames were experimentally and numerically investigated at pressures from 2 to 7 bar. In the experiment, laser-induced incandescence (LII), time-resolved LII, and color-ratio pyrometry were used to measure soot volume fraction, soot particle diameter, and flame temperature. The results show that n-butylbenzene has a significantly higher soot propensity than n-butylcyclohexane. The soot growth and oxidation in both flames are enhanced with increasing pressure. The difference is that the promotion effect of pressure on the soot formation in the n-butylcyclohexane flame continues to weaken as the pressure increases, while this phenomenon does not occur in n-butylbenzene flames. Within the studied pressure range, the mean particle sizes (Dp(mean)) in n-butylcyclohexane and n-butylbenzene flames show a good linear relationship with pressure. The pressure dependence of Dp(mean) in n-butylbenzene flames is stronger than that of n-butylcyclohexane flames at pressures between 2 and 6 bar. The experiment and simulation results indicate that the enhancement of the promotion effect of pressure on the soot formation in the n-butylbenzene flame may be due to the combined effect of an increase in the soot surface reactivity and an increase in the number density of soot particles. The reaction pathway analysis suggests that the stepwise dehydrogenation reactions of cyclohexene are the main source of benzene formation in n-butylcyclohexane flames and pyrene is mainly formed via the reaction between indenyl and benzyl radicals in n-butylbenzene flames.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    Role of secondary hydrogen injection on flame stabilization of ammonia/air swirling flames

    Wei, XutaoZhang, MengWang, RuixiangWang, Jinhua...
    1.1-1.17页
    查看更多>>摘要：Ammonia is widely recognized as one of the most advanced hydrogen carriers and can be utilized as a fuel in gas turbines. Premixing hydrogen into the ammonia carbon free fuel system can substantially enhance stable limits, but it significantly promotes cross-reactions, leading to increased NO production. Recent findings related to other fuels suggest that the alternative approach for mitigating combustion instabilities involves introducing minimal pure hydrogen at the chamber inlet in a non-premixed mode. This may introduce a novel approach to stabilize ammonia/air swirl flames by extending the stability through a minimal hydrogen via secondary injection, with minimal impact on increasing nitrogen oxide emissions. In the present study, the flame stabilization mechanism and nitrogen oxide emission behaviors of swirl ammonia/air flames by a secondary hydrogen injection were compared with the premixed ammonia/ hydrogen/air flames. OH-/NO-PLIF and PIy techniques were applied to reveal the lean blow-off characteristics and the reacting flow features. The NOx x emissions were measured by the FTIR gas analyzer. The large eddy simulation method with a developed dynamic thickened flame model was employed to further reveal the experimental findings. Experimental results show that the flame stabilization limits are largely depended on the way in which hydrogen is introduced. The secondary hydrogen injection exhibits the stronger enhancement ability for the lean/rich blow-off limits, primarily due to the local diffusion hydrogen flame at the flame root providing more active radicals and higher temperature gases. The NO emission shows an increase with the addition of premixed hydrogen, while in the secondary hydrogen injection, NO emission deteriorates due to higher temperatures, with the NO emission increasing by less than 10% compared with the ammonia flame. In the large eddy simulation analyses, the physical effects of the secondary hydrogen injection enhance the flame stability by increasing the resistance of the flame root to extinction. The heat release rate and the mass fractions of NH and H near the flame root are significantly increased by 2% secondary hydrogen injection. The enhancement of the ammonia decomposition process is stronger with secondary hydrogen injection than with fully premixed hydrogen addition. For 2% secondary hydrogen injection case, the local hydrogen injection to form a non-premixed combustion mode can provide much higher capability to increase the local heat release rate compared to the fully premixed mode. Novelty and significance statement: Introducing small amount of hydrogen to ammonia flame can effectively improving the flame stabilization in a swirl combustor. In this study, it is found that the flame stabilization limits are largely depended on the way in which hydrogen is introduced. Comparing the way of premixing hydrogen in the unburned mixture, a larger effect on blow-off limits extension was found when introducing a separate non-premixed hydrogen at the chamber inlet, which is mentioned as the secondary hydrogen injection. The lean blow-off limits can be extended from about 0.67 to 0.59 when only introducing 2% % secondary hydrogen injection by heat value. The NO emission shows in the secondary hydrogen injection, NO emission deteriorates by less than 10% % compared with the ammonia flame. A thickened flame model for non-premixed combustion was established and verified adequate with velocity field and flame structure.The mechanisms of enhancing flame stabilization by hydrogen introduction including physical and chemical effects for premixing and injection cases were revealed. Furthermore, the difference in the mechanisms of the two cases was emphasized.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    Solid-to-gas phase transition kinetics of diverse potassium occurrence forms during biomass pellet combustion: Time-resolved detection and multi-step modeling

    Sun, CenWei, XiaolinLiu, HuiminLi, Sen...
    1.1-1.15页
    查看更多>>摘要：The solid-to-gas phase transition of potassium during biomass combustion significantly impacts ash-related issues in bioenergy systems, affecting operational efficiency and equipment longevity. However, the specific mechanisms and kinetics of this transition process remain inadequately understood. This work investigates the timeresolved transition of solid-phase potassium to the gas phase during the combustion of rice husk and wheat straw pellets, combining experimental measurements with theoretical modeling. Tunable diode laser absorption spectroscopy (TDLAS) was employed to measure atomic potassium concentrations 15 mm above burning pellets tray, where gas-phase equilibrium is approached. Key combustion characteristics including thermogravimetric profiles, spectral radiation, and temperature were simultaneously monitored. A novel multi-step model was developed to describe the transition of different forms of solid-phase potassium (organic, exchangeable, and inorganic) to the gas phase. This model integrates TDLAS measurements, observed combustion characteristics, and biomass physicochemical properties. Thermodynamic equilibrium calculations were used to estimate the atomic potassium fraction from total gaseous potassium. The results showed that the solid-to-gas phase transition of organic potassium synchronizes with volatiles release. In contrast, the maximum emission rates of inorganic and exchangeable potassium occurred at the onset of char combustion. The developed model agrees well with the online detection experiments and were further validated by offline ICP analysis of residual ash. While not directly simulating gas-solid interface reactions near the particle surface, this work lays groundwork for future multiscale modeling of particle-laden flows and reactor-scale phenomena in biomass combustion systems.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    Three-dimensional simulations of NEPE propellant combustion under depressurization effects

    Chen, KaixuanYe, ZhenweiYu, YizheXue, Xiaochun...
    1.1-1.14页
    查看更多>>摘要：This study aims to analyze the characteristics of micro-combustion and unsteady flame development in nitrate ester-plasticized polyether (NEPE) propellant when exposed to rapid pressure decay. A three-dimensional NEPE propellant combustion model is firstly established to achieve this goal. The framework consists of two parts. Firstly, we used sequential algorithms to generate a 3D numerical pack satisfying industrial requirements. In the numerically generated propellant pack, Ammonium perchlorate (AP) particles, and Cyclotetramethylene tetranitramine (HMX) particles are assumed as spheres, whereas the void space is Nitroglycerin/1,2,4-Butane triol trinitrate (NG/BTTN) binder. Secondly, a new kinetic model considering the pyrolysis of condensed phase and complicated interaction of gas species in the gas phase is proposed, which has been not reported until now. The accuracy of this framework is verified via comparing with experimental results. Upon simulating the depressurization combustion of NEPE propellant, it is observed that the non-planar surface stimulates the growth of Leading-Edge Flames, leading to intensified burning during the initial stage of depressurization combustion. After 5.2 ms of depressurization combustion, a remarkable increase in bulk heat release in the gas phase is discovered, attributed to the involvement of coarse AP particles, thereby providing a conducive oxidizing burning environment. Examination of the propellant surface temperature reveals that the oxidizer/binder interface exhibits higher temperatures ( 950 K) at 3.4 MPa, while the particle core typically remains cooler ( 850 K) at pressures ranging from 1.0 to 3.5 MPa. The dynamic temperature fluctuations are a result of the heterogeneity of the propellant microstructure, which also serves as the primary cause of oscillations in several globally averaged parameters. The flickering flame behavior during transient combustion, along with the corresponding combustion characteristics, offers theoretical insights for the study of combustion instability in solid rocket motors, warranting further validation through experimental cases.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    Numerical analysis of the flame piston-model for acceleration runaway in thin tubes

    Hernandez-Sanchez, RaulDenet, Bruno
    1.1-1.11页
    查看更多>>摘要：A one-dimensional model is developed and studied to explore the flame acceleration runaway mechanism for deflagration-to-detonation transition in thin tubes. This mechanism relies solely on the thermal feedback between the compression waves ahead of the flame and the temperature-sensitive laminar velocity of the flame. Within this model, the primary driver of the flame acceleration and compressive heating enhancement is the gas flow caused by the increased flame surface area. Results from the numerical integration of the reactive Navier-Stokes equations for perfect gases with a single-step chemical-kinetics model are compared with the solutions obtained when considering the flame as a steady-state discontinuity. The numerical results illustrate the flame acceleration runaway in finite time caused by a double feedback loop established in this model. The evolution of the flame acceleration towards a finite-time singularity eventually leads to the formation of a shock wave within the flame structure, triggering the onset of a detonation. Novelty and significance statement This paper presents numerical results obtained using an approach recently proposed to study the effect of flame acceleration on the one-dimensional internal structure of the flame. Unlike previous studies on flame acceleration leading to DDT based on one-dimensional models in which the flame acceleration due to the increase of its surface area is modeled by accelerating chemical kinetics, the present approach consists in the introduction of a backflow of burned gases pushing the flame tip from behind as a piston. The numerical analysis performed in this work allows considering finite reaction rates in this model obtaining results that compare favorably with those obtained when the flame is considered as a discontinuity. The results of this numerical study support previous analytical studies on the flame acceleration runaway mechanism for DDT and illustrate the acceleration process of a flame propagating over a gas flow with a markedly subsonic velocity which leads to the onset of a detonation.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    A theoretical and kinetic study of key reactions between ammonia and fuel molecules, part III: H-atom abstraction from esters by (N) over dotH 2 radicals

    Sun, JingwuYang, LijunWen, DongshengCurran, Henry J....
    1.1-1.12页
    查看更多>>摘要：Hydrogen atom abstraction reactions by (N) over dotH(2) radicals play a crucial role in determining the reactivity of ammonia/fuel binary blends. Esters are a typical component of environmentally friendly and economically promising biofuels. The feasibility of the ammonia/biofuel dual-fuel approach has been proven in practical engines. [Energy and Fuels 22 (2008) 2963] and [Int. J. Energy Res. 2023 (2023) 9920670]. (N) over dotH(2) radicals play a critical role in the combustion and pyrolysis chemistry of ammonia and N-containing-rich fuels. In ammonia/biofuels hybrid combustion, (N) over dotH(2) radicals can react with biofuel molecules in a reaction class that is particularly important especially when sufficient ammonia is blended in order to eliminate NOx emissions. To help unravel the chemistry of ammonia/biofuel blends, a systematic theoretical kinetic study of H-atom abstraction from eleven alky esters of CnH2n+1COOCH3 (n = 1-4), CH3COOCmH2m+1 (m = 1-4), and C2H5COOC2H5, by (N) over dotH(2) radicals is performed in this work. The geometry optimization, frequency, and zero-point energy calculations for all related species, as well as the hindrance potential energy surface for low frequency torsional modes in the reactants and transition states, were performed at the M06-2X/6-311++G(d,p) level of theory. Intrinsic reaction coordinate calculations were performed to validate the connections between the transition states and expected minima energy species. The energies of all of the species involved were calculated at the QCISD(T)/cc-pVXZ (X = D, T, Q) and MP2/cc-pVYZ (Y = T, Q) levels of theory and then extrapolated to the complete basis set. Rate constants of 39 reactions were calculated using the Master Equation System Solver (MESS) program in the temperature range of 500 - 2000 K. These rate constants for different H-atom abstraction sites are provided and can be extrapolated to larger esters. The kinetic effects from the functional group are also illustrated by performing detailed comparisons with the previous studies of (N) over dotH(2) radical reactions with alkanes, alcohols and ethers.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    ReaxFF molecular dynamics study of N-containing PAHs formation in the pyrolysis of C 2 H 4 /NH 3 mixtures

    Zhang, KaiXu, YishuYu, RonghaoWu, Hui...
    1.1-1.10页
    查看更多>>摘要：The reactive force field molecular dynamics (ReaxFF MD) simulations are performed to depict the whole process including fuel pyrolysis, the formation and growth of PAHs/NPAHs and soot formation in the pyrolysis of C2H4 and C2H4/NH3 mixtures. NH3 doping increases the concentration of H radicals through the decomposition of NH3. These H radicals then promote the consumption of C2H4 by participating in H-abstraction reactions. The formation of C-N species (mainly HCN, H2CN, C2N, CH3CN, NCCN, and HC3N) removes the C atoms participating in the formation of PAHs and soot, thus inhibiting the formation of soot. And such inhibitory effect is strengthened with increasing temperature due to the promoted formation of C-N species. Most importantly, the structure, formation and evolution paths of N-containing PAHs (NPAHs) are identified based on the experimental and simulation results for the first time, revealing that N atoms in the NPAHs are almost always present in the carbon chains attached to the aromatic rings while barely enter the rings to form heterocyclic structure. The simulations further reveal that when the temperature is less than 2500 K, the first N-containing aromatic ring is formed through the reaction of phenyl with small C-N species (such as HCN and CN radicals), followed by the increase of new rings primarily via the HACA mechanism. At temperatures greater than 2500 K, the formation and growth of NPAHs are dominated by the continuous attachment of N-containing carbon chains and cyclic polycondensation-cyclization reactions. The identification of new C-N species especially NPAHs would help improve the kinetic mechanisms for ammonia blending combustion.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    Numerical investigation of lean methane flame response to NRP discharges actuation

    Barleon, N.Lacoste, D. A.Alkhalifa, A. M.Vermorel, O....
    1.1-1.12页
    查看更多>>摘要：This study investigates the response of a laminar methane-air flame to Nanosecond Repetitively Pulsed (NRP) discharges in a canonical wall-stabilized burner using a combined experimental and numerical approach. The flow and flame behaviors were modeled using Direct Numerical Simulation (DNS) with an Analytically Reduced Chemistry for a precise chemical description. A phenomenological model incorporating detailed plasma kinetics and experimental observations was developed to simulate plasma effects. Zero-dimensional plasma reactor simulations were used to build up a reduced-order model describing discharge energy distribution in the specific conditions studied. Experimental measurements of electrical profiles identified two discharge regimes: a low-energy Corona discharge and a higher-energy Glow discharge, characterized by distinct spatial energy distributions. Experimental flame response analysis revealed three major phases: marginal response up to 100 pulses, a downstream shift of the flame tip, and stabilization after 400 pulses. Numerical simulations indicated that the Corona regime is crucial for explaining initial flame responses, while the Glow regime influences later stages. Adjustments in the Vibrational-Translational (VT) energy relaxation time and energy deposition ratios between fresh and burnt gases were necessary to match experimental observations. Additionally, an accurate modeling of the transient and steady-state flame responses requires integrating both the specificity of the Corona and the Glow discharge regimes. Future work should focus on measuring or theoretically calculating N-2(v) relaxation times in CH4-H2O-CO2 mixtures and analyzing the spatial energy distribution of discharges interacting with flames to enhance plasma-combustion coupled models.
      原文链接:
    • NETL
    • NSTL
    • Elsevier