Combustion and Flame最新文献

{"title":"A comprehensive parametric study on NO and N2O formation in ammonia-methane cofired premixed flames: Spatially resolved measurements and kinetic analysis","authors":"Qing Li ,&nbsp;Liuhao Ma ,&nbsp;Jiwei Zhou ,&nbsp;Jintao Li ,&nbsp;Fuwu Yan ,&nbsp;Jianguo Du ,&nbsp;Yu Wang","doi":"10.1016/j.combustflame.2024.113851","DOIUrl":"10.1016/j.combustflame.2024.113851","url":null,"abstract":"<div><div>Understanding the mechanism of NO<em>x</em> formation and destruction is a prerequisite for the development of effective NO<em>x</em> mitigation techniques in ammonia flames. Laboratory-scale laminar ammonia (NH₃) flames are well suited for such fundamental kinetic studies as the complex interaction between chemistry and fluid flow can be largely decoupled. However, quantitative and spatially resolved NO/N₂O concentration data in canonical laminar ammonia flames are surprisingly scarce. Such data is, on the other hand, crucial for developing and validating kinetic models for NH₃ combustion. In this regard, we developed a novel NO/N₂O measurement method combining microprobe sampling and calibration-free mid-infrared laser absorption spectroscopy and realized spatially-resolved detection with high accuracy and large dynamic ratio. The fidelity of the method has been rigorously tested before being applied to perform a comprehensive parametric study on NO and N₂O formation in NH₃-CH₄ co-fired burner-stabilized premixed flames. The effects of NH₃ fuel ratio, equivalence ratio and flame temperature on NO/N₂O formation have been experimentally determined. Corresponding numerical modelling was also performed using literature-based mechanisms to provide kinetic insights into the experimental observations. It is found that existing mechanisms generally have satisfactory predictions in fuel-lean flames; however, under fuel-rich conditions, these mechanisms overpredict NO formation but underestimate its destruction, leading to significant over-prediction. Such discrepancies were further investigated through sensitivity and reaction pathway analysis. The present study not only provides extensive spatially-resolved NO/N₂O data in ammonia flames that are urgently needed for the development and validation of NH₃ combustion mechanisms, the comparison between neat CH₄ and NH₃-cofired flames also points to the fact that traditional NO<em>x</em> mitigation techniques that are popular in combustion of hydrocarbon fuels may not be appropriate in NH₃ flames. Perhaps most interestingly, the present experimental results show an oxygen-enriched oxidizer can in some cases reduce NO emission from NH₃ flames.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113851"},"PeriodicalIF":5.8,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Elucidating high-pressure chemistry in acetylene oxidation: Jet-stirred reactor experiments, pressure effects, and kinetic interpretation","authors":"Qian-Peng Wang ,&nbsp;Jing Yang ,&nbsp;Yu-Feng Xu ,&nbsp;Zi-Qiang Zhu ,&nbsp;Ling-Nan Wu ,&nbsp;Jiu-Jie Kuang ,&nbsp;Du Wang ,&nbsp;Marina Braun-Unkhoff ,&nbsp;Zhen-Yu Tian","doi":"10.1016/j.combustflame.2024.113835","DOIUrl":"10.1016/j.combustflame.2024.113835","url":null,"abstract":"<div><div>Acetylene plays a crucial role as an intermediate in the combustion of complex hydrocarbons, such as, e.g.<em>,</em> jet fuels. In this study, high-pressure acetylene oxidation has been investigated by a combination of kinetic and experimental methods using a jet-stirred reactor (JSR) in the range of 497–910 K at <em>p</em> = 24 atm. The study covered three fuel-equivalence ratios: <em>φ</em> = 0.5 (fuel-lean), <em>φ</em> = 1.0 (stoichiometric), and <em>φ</em> = 3.0 (fuel-rich). Mole fraction profiles of 10 species, including CO, CO₂, CH₄, C₂H₄, C₂H₆, C₃H₆, C₃H₈, CH₃OH, CH₃CHO, and C₃H₄O, were identified and quantified using gas chromatography (GC) and gas chromatography-mass spectrometry (GC–MS). A kinetic model for describing the high-pressure chemistry of acetylene oxidation is proposed, which well characterizes important experimental findings, such as the fuel oxidation reactivity and the speciation of crucial products. At high pressures (<em>p</em> = 24 atm), acetylene exhibits a higher fuel consumption than at lower pressures (<em>p</em> = 1 and 12 atm) because of the increased sensitivity of dehydrogenation reactions by OH radicals accelerating the oxidation of the fuel at low temperatures. Furthermore, fuel-specific intermediates are observed, including acetaldehyde, propanal, small alkanes, and alkenes. These species mainly result from H-abstraction reactions by OH following O₂-addition reactions from triple carbon bond moieties in acetylene. The formation of further products, such as carbon monoxide and carbon dioxide, is closely related to the consumption of these fuel-specific species. In particular, the formation of aromatics, such as e.g., benzene and toluene, are detected at trace levels in the current experiments due to the rapid formation and decomposition process occurring at high pressures. By analyzing the distinct kinetic behavior, it was found that acetylene was almost completely depleted at higher system pressure (<em>p</em> = 24 atm). Some intermediates are rather active and can react with O₂ and peroxides. Consequently, the high-pressure oxidation of acetylene mainly proceeds along the pathway of C<img>C → CHCHOH → HOCHO/OCHCHO → CO → CO₂ at the high-pressure chemistry (<em>p</em> = 24 atm). Overall, this study provides valuable insights into the pressure-dependent combustion behavior of acetylene and its implications for optimizing jet fuel combustion processes.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113835"},"PeriodicalIF":5.8,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simultaneous Schlieren and direct photography of detonation diffraction regimes in hydrogen mixtures","authors":"Jacob Klein,&nbsp;Omid Samimi-Abianeh","doi":"10.1016/j.combustflame.2024.113845","DOIUrl":"10.1016/j.combustflame.2024.113845","url":null,"abstract":"<div><div>The diffraction behavior of gaseous detonations through an abrupt area change is investigated using hydrogen-oxygen-nitrogen mixtures at initial pressures of 0.5 and 1.0 bar. Critical conditions are noted and detailed discussion of the differing diffraction behaviors is undertaken, supported by simultaneous Schlieren and direct photography imaging as well as pressure-based velocity measurements. The experiments reveal four distinct diffraction regimes. The subcritical outcome is characterized by transmission failure with the leading shock front decoupling from the reaction zone, seen predominantly at lower oxygen concentrations. At intermediate oxygen levels, reinitiation from reflected shock waves is consistently observed. The critical regime exhibits both subcritical and supercritical outcomes, with detonation reinitiation at the diffraction dome's head leading to localized implosions for the supercritical case. Supercritical outcomes demonstrate successful detonation transmission, maintaining the shock front and reaction zone coupling. The effects of initial conditions on the probability of successful detonation transition and diffraction are highlighted. With the use of simultaneous direct photography and Schlieren imaging techniques, previously unseen details of the detonation and diffraction processes are recorded and explained.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113845"},"PeriodicalIF":5.8,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ab initio intermolecular interactions mediate thermochemically real-fluid effects that affect system reactivity: The first application of high-order Virial EoS and first-principles multi-body potentials in trans-/super-critical autoignition modelling","authors":"Mingrui Wang ,&nbsp;Ruoyue Tang ,&nbsp;Xinrui Ren ,&nbsp;Yanqing Cui ,&nbsp;Molly Meng-Jung Li ,&nbsp;Shao-Yuan Leu ,&nbsp;Carol Sze Ki Lin ,&nbsp;Song Cheng","doi":"10.1016/j.combustflame.2024.113844","DOIUrl":"10.1016/j.combustflame.2024.113844","url":null,"abstract":"<div><div>The properties of supercritical fluids are dictated by intermolecular interactions that involve two or more molecules. Such intermolecular interactions were described via intermolecular potentials in historical supercritical combustion modeling studies, but have been treated empirically and with no consideration of radical interactions or multi-body interactions involving more than two molecules. This approach has been adopted long ago, assuming sufficient characterization of real-fluid effects during supercritical combustion. Here, with data from <em>ab initio</em> multi-body intermolecular potentials, non-empirical high-order Virial Equation of State (EoS), and real-fluid thermochemical and kinetic simulations, we reveal that empirical intermolecular potentials can lead to significant errors in representing supercritical fluids under common combustion situations, which can be impressively described by <em>ab initio</em> intermolecular potentials. These interactions are also found to greatly influence autoignition delay times, a common measure of global reactivity, with significant contributions from radical interactions and multi-body interactions. It is therefore of necessity to incorporate <em>ab initio</em> intermolecular interactions in studying supercritical combustion and various dynamic systems involving supercritical fluids, which has now been enabled through the new framework developed in the present study.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113844"},"PeriodicalIF":5.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Bayesian approach to estimate flame spread model parameters over the cylindrical PMMA samples under various gravity conditions","authors":"Shinji Nakaya ,&nbsp;Taro Takemata ,&nbsp;Yuxuan Ma ,&nbsp;Fangsi Ren ,&nbsp;Mitsuhiro Tsue","doi":"10.1016/j.combustflame.2024.113828","DOIUrl":"10.1016/j.combustflame.2024.113828","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The flammability limit of cylindrical polymethyl-methacrylate (PMMA) samples in an opposed-flow was observed experimentally under various gravity levels at 1&lt;span&gt;&lt;math&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; or more utilizing a centrifuge. Flame spread on the sample was observed, and the limiting oxygen concentration (LOC) was measured in various opposed-flow velocities ranging from 5 to 30 cm/s. Two rotating radii of the centrifuge were tested to assess the effects of Coriolis force on the LOC. A scale analysis model, based on an energy balance equation, was evaluated for thermally thick cylindrical samples. The buoyancy-induced flow was modeled in the analytical model. Model parameters were evaluated with a Bayesian approach: The Metropolis Hasting (a Markov Chain Monte Carlo) method. The results indicated that flames were tilted by the Coriolis force when the oxygen concentration was sufficiently rich from the LOC in 4&lt;span&gt;&lt;math&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;. However, the effects were negligible under the oxygen concentration conditions near LOC. No significant difference in the LOC was also observed even when the rotating radius of the centrifuge changed. At 1&lt;span&gt;&lt;math&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; or higher, the LOC approached to a certain value asymptotically with decreasing the opposed-flow velocity. The LOC also increased with increasing the gravity level and sample diameter. The measured LOCs were used to sample model parameters using MCMC methods. Consequently, a suitable fitting curve of the model to the experimental LOC was obtained. Using the predicted model parameters, the LOC under microgravity, Moon, and Mars conditions were predicted as a function of the opposed-flow velocity. In microgravity, the LOC increased greatly with decreasing the forced flow velocity (the radiative extinction regime), and the minimum LOC (MLOC) was recognized. On Moon, the credible interval of LOC was rather large in the low-velocity region, and the MLOC was also recognized. Moreover, it was possible that the cylindrical PMMA sample exhibited the highest flammability not under microgravity but a partial gravity condition.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and Significance&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;From observing the limiting oxygen concentration of the flammability limit for cylindrical polymethyl-methacrylate (PMMA) samples in opposed-flows under various gravity conditions, we developed a model of limiting oxygen concentration (LOC) for thick cylindrical samples with the buoyancy induced flow was developed, and we estimated difficult-to-predict parameters using Bayesian statistical methods. Using this model, we can estimate the flammability limits under various gravity conditions of manned space exploration, including Moon and Mars. In addition, the present study shows that the minimum limiting oxygen concentration (MLOC) is the lowest in partial gravity. These results open a new research field for partial gravity combustions, apart from the normal gravity and microgravity and c","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113828"},"PeriodicalIF":5.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inhibition of the oblique detonation wave detachment in two-phase n-heptane/air mixtures","authors":"Hongbo Guo ,&nbsp;Yue Sun ,&nbsp;Ruixuan Zhu ,&nbsp;Shuo Wang ,&nbsp;Majie Zhao ,&nbsp;Baolu Shi ,&nbsp;Xiao Hou","doi":"10.1016/j.combustflame.2024.113843","DOIUrl":"10.1016/j.combustflame.2024.113843","url":null,"abstract":"<div><div>In this work, oblique detonation wave propagations in <em>n</em>-heptane droplet/vapor/air mixtures induced by a wedge at high altitude and Mach number are simulated by the Eulerian-Lagrangian method with a skeletal chemical mechanism. This work is a first attempt to inhibit the detachment of oblique detonation wave (ODW) and expand the operation range of thrusters based on oblique detonation combustion in partially pre-vaporized <em>n</em>-heptane/air mixtures. Effects of gas/liquid equivalence ratios and droplet diameters are considered, and the ODW morphology is analyzed. Standing windows, ODW characteristics and predictability of detachment inhibition are discussed. First, the detonation theoretical calculation is performed at 25–40 km operation conditions for pure gas <em>n</em>-heptane/air mixtures. The results show that the wedge angle range for successful ignition, <em>i.e.</em>, standing window, increases with the increase of flight altitude and Mach number. The internal energy and kinetic energy of mixtures are affected by the wedge angle and flight Mach number, so that the maximum angle of ODW with flight conditions presents an opposite trend over or below Mach 10. The two-dimensional (2D) ODWs in our simulation scope, which are triggered by the collision of the initiation zones formed from the wedge, show a multi-wave head structure similar to normal detonation. Detachment is inhibited in partially pre-vaporized <em>n</em>-heptane/air mixtures, due to the non-explosive mixtures near triple-point and the post-ODW inter-phase mass and energy transfers by the latent heat absorption and vapor addition from droplet evaporation. Moreover, the predictability of pre-vaporized <em>n</em>-heptane on inhibiting ODW detachment is explored through the relationship of chemical and evaporation timescales. It is demonstrated that the excitation time is very small approaching the detachment condition where an abrupt ODW tends to form. Accordingly, when the ratio of droplet heat absorption time to evaporation time is relatively high, <em>i.e., τ_h</em> / (<em>τ_ev</em>)^1/2 &gt; 0.01, the ODW detachment is more likely to be inhibited.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113843"},"PeriodicalIF":5.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of the inflow total temperature on the non-premixed rotating detonation engine performances","authors":"Zhenyi Chen ,&nbsp;Sihang Rao ,&nbsp;Jian Peng ,&nbsp;Xu Xu","doi":"10.1016/j.combustflame.2024.113726","DOIUrl":"10.1016/j.combustflame.2024.113726","url":null,"abstract":"<div><div>As a promising propulsion system, air-breathing rotating detonation engines (RDEs) are investigated with significant interest recently. However, simulations of air-breathing RDE with real flight condition are limited, and performance of RDEs with high inflow total temperature, as well as the influence of inflow total temperature on RDEs, needs further exploration. In this paper, simulations with four inflow total temperatures (300 K, 500 K, 700 K and 900 K) were conducted to analyze the propagation features of rotating detonation waves (RDWs) and operation modes in the RDE at low and high inflow total temperatures. Additionally, injection and mixing, as well as combustion characteristics and propulsion performance of the RDE were researched. It is found that with low inflow total temperature, single wave propagates in the combustor, which degenerates into shock wave at the outer wall due to insufficient mixing. When inflow total temperature is high, the RDE is in multi-wave operation mode and detonative combustion only occurs around the outer wall. With increase of inflow total temperature, mixability of reactants initially improves but then deteriorates slightly. Moreover, RDW propagation velocity and specific impulse of the RDE decrease. Though fuel utilization rate improves, detonation fraction drops dramatically and parasitic combustion fraction rises significantly, resulting from intensification of pre-combustion. Particularly, the detonation fraction is only 16.7 % and parasitic combustion fraction reaches up to 56.35 % at inflow total temperature of 900 K. Furthermore, regardless of the variation of inflow total temperature, detonative combustion is prominent in the premixed combustion mode, and the peak fraction of detonation appears at the off-stoichiometric ratio.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113726"},"PeriodicalIF":5.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coupling regimes of premixed laminar flames with thermal radiation absorption in fresh gases. Application to H2O-/CO2-diluted mixtures","authors":"J. Ben Zenou,&nbsp;R. Vicquelin","doi":"10.1016/j.combustflame.2024.113830","DOIUrl":"10.1016/j.combustflame.2024.113830","url":null,"abstract":"&lt;div&gt;&lt;div&gt;In the context of decarbonizing industry and transportation, the combustion of hydrogen and oxycombustion of methane play a pivotal role. Hydrogen combustion can use steam (H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;O) to mitigate pollutant emissions, while methane’s oxycombustion involves recirculating burnt gases (EGR or Exhaust Gas Recirculation process), particularly CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;. This paper investigates the complex role of thermal radiation in premixed laminar flames, in particular in such H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; &lt;img&gt;Air&lt;img&gt;H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;O and CH&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; &lt;img&gt;O&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; &lt;img&gt;CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; mixtures. It highlights how radiation assumes a significant role in flames diluted with radiative participating gases, through both emission and reabsorption. The main objective is to achieve a comprehensive physical understanding of the coupling between thermal radiation and combustion, examining its effects on flame structure and burning velocity and how it varies with different parameters (equivalence ratio, dilution level, pressure, and domain size). The study employs detailed 1D premixed laminar flame simulations by coupling a fluid and a radiative solver. Both a grey gas approximation for preliminary understanding and realistic radiative gas properties (CK model) are considered. Coupling numbers derived from characteristic time ratios for convection, chemistry, and radiation, are presented. These metrics facilitate the classification of radiation-combustion coupling into three distinct regimes that represent distinct qualitative physical phenomena. The regimes are defined as follows: &lt;em&gt;WeakAbs&lt;/em&gt;, where the effects of thermal radiation absorption are minor; &lt;em&gt;RadConv&lt;/em&gt;, where thermal radiation competes with convection in the fresh and burnt gases but does not interact directly with chemistry within the flame front; and &lt;em&gt;RadChem&lt;/em&gt;, where thermal radiation also competes with chemistry within the flame front. For the investigated conditions in both H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and CH&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; flames, thermal radiation also quantitatively alters the flame speed, with an acceleration that can be significant. Furthermore, the paper presents an iterative two-layer model to efficiently estimate the impact of thermal radiation on flames, which shows high accuracy except in the &lt;em&gt;RadChem&lt;/em&gt; regime. Lastly, it introduces a predictive model that quickly determines a flame’s coupling regime using only an adiabatic simul","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"271 ","pages":"Article 113830"},"PeriodicalIF":5.8,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Real-fluid effects on laminar premixed hydrogen flames under cryogenic and high-pressure conditions","authors":"Ziting Lv ,&nbsp;Hanzhang Cao ,&nbsp;Wang Han ,&nbsp;Lijun Yang","doi":"10.1016/j.combustflame.2024.113837","DOIUrl":"10.1016/j.combustflame.2024.113837","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The combustion of hydrogen (H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) under cryogenic and high-pressure conditions has the potential to increase the volume-based energy density of H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and combustion efficiency. Predictive modeling of cryogenic H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; premixed flames at high pressures requires a clear understanding of real-fluid effects. While substantial effort has been made to study the real-fluid effects in nonpremixed flames, comparatively fewer investigations have been performed to explore real-fluid effects on premixed flames, especially at cryogenic and high-pressure conditions. This work aims to fill a part of this gap by conducting a series of laminar premixed H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; flame simulations at cryogenic and high-pressure conditions (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;u&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;50&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;–350&lt;!--&gt; &lt;!--&gt;K and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mn&gt;20&lt;/mn&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mn&gt;40&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; &lt;!--&gt; &lt;!--&gt;MPa). Four cases are considered to examine the role of corrections of the equation of state (EOS), thermodynamic properties, and transport properties in predicting flame structure and properties. It is found that the real-fluid effects mainly occur in the fresh/preheat regions and that the correction of EOS plays a critical role in the prediction of flame structure and the laminar flame speed (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;), while the correction of transport properties is critical for predicting flame thickness. Each correction could contribute to the predictions of the mass burning rate and the flame thickness but hardly affect the flame temperature (less than 1% relative difference). A scaling law of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;Real&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;Ideal&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;Z&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;u&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;Z&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;u&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; is the compressibility factor of the unburned mixture) is proposed, which can be used to readily predict &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; of real fluid from the speed evaluated by the ideal gas model. In addition, the Monte Carlo sampling method is used to perform uncertainty quantification of S&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; due to the uncertainty of the real-fluid model parameters. The results show that the critical properties of H&lt;span&gt;&lt;","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113837"},"PeriodicalIF":5.8,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A framework for obtaining frequency-dependent stability maps to mitigate thermoacoustic instabilities","authors":"Hamed F. Ganji ,&nbsp;Viktor Kornilov ,&nbsp;Ines Lopez Arteaga ,&nbsp;Philip de Goey ,&nbsp;Jeroen van Oijen","doi":"10.1016/j.combustflame.2024.113836","DOIUrl":"10.1016/j.combustflame.2024.113836","url":null,"abstract":"<div><div>This paper utilizes Cauchy’s argument principle in the frequency domain to develop novel stability maps, providing guidelines for measures which can be taken to mitigate thermoacoustic instabilities in combustion appliances. The existing approaches mainly concentrate on identifying the onset of thermoacoustic instabilities by calculating unstable frequencies and growth rates. However, they provide limited practical guidance for modifying system characteristics, especially those dependent on frequency, to achieve flame stabilization. In the present contribution, several thermoacoustic stability criteria are introduced that leverage the Cauchy’s argument principle and direct evaluation of the dispersion relation’s argument. These criteria offer deeper insights and facilitate a systematic flame stabilization process by enabling modifications to both the (passive) acoustic subsystems and/or the (active) subsystem containing the combustion processes. This approach allows for a construction and comprehensive understanding of the stability map for a given thermoacoustic system, leading to more effective guidelines to elaborate and implement the combustion system stabilization strategies. To demonstrate the practical application of this framework, two illustrative thermoacoustic systems are discussed.</div><div><strong>Novelty and significance statement</strong> This study introduces a novel framework for assessing thermoacoustic stability. <ul><li><span>•</span><span><div>It provides a method for detecting the onset of thermoacoustic instability and offers valuable insights into critical frequency ranges. This approach facilitates the identification of necessary modifications in flame and acoustic subsystems across different frequencies to achieve system stabilization.</div></span></li><li><span>•</span><span><div>This framework allows for the selection of the most suitable stability criterion based on the available combustion system’s characteristics. For example, by knowing acoustic properties in both upstream and downstream components, either the DDS or DCS criterion can generate a comprehensive, frequency-dependent stability map for flame transfer function values. This approach eliminates the need for iterative integration, differential equations, or direct solutions to dispersion relations.</div></span></li></ul></div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113836"},"PeriodicalIF":5.8,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653974","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}