Combustion and Flame最新文献

{"title":"Numerical analysis of the flame piston-model for acceleration runaway in thin tubes","authors":"Raúl Hernández-Sánchez ,&nbsp;Bruno Denet","doi":"10.1016/j.combustflame.2024.113775","DOIUrl":"10.1016/j.combustflame.2024.113775","url":null,"abstract":"<div><div>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.</div><div><strong>Novelty and significance statement</strong></div><div>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.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113775"},"PeriodicalIF":5.8,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423807","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":"Investigating combustion efficiency and NOx emission reduction in fluidized bed ammonia-coal co-firing","authors":"Tianxin Li ,&nbsp;Lin Li ,&nbsp;Chong Liu ,&nbsp;Heng Liu ,&nbsp;Guang Sun ,&nbsp;Ning Ding ,&nbsp;Dennis Lu ,&nbsp;Lunbo Duan","doi":"10.1016/j.combustflame.2024.113735","DOIUrl":"10.1016/j.combustflame.2024.113735","url":null,"abstract":"<div><div>Ammonia, a carbon-free fuel, can significantly reduce CO₂ emissions when co-fired with coal in power plants. Fluidized bed combustion, known for its excellent gas-solid mixing and low NO_x emissions, is a promising method for ammonia-coal co-firing. However, challenges remain in optimizing ammonia injection and controlling nitrogen oxide emissions. This study investigates these aspects using a lab-scale fluidized bed reactor with flexible ammonia injection points. Key variables, such as ammonia co-firing ratios, injection location, temperature, and outlet oxygen concentration, are examined. The results show that with ammonia injection ratios up to 70 %, NO and N₂O emissions slightly increase, while ammonia escape is maintained below 5 ppm. Air staging effectively controls NO_x emissions, and higher temperatures promote N₂O decomposition, but increase NO_x levels. Ammonia injection does not raise unburned carbon content. Rate of production and sensitivity analyses highlight the role of OH radicals in ammonia conversion and identify the critical reactions affecting NO generation. This study highlights the feasibility of fluidized bed ammonia-coal co-firing technology.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113735"},"PeriodicalIF":5.8,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423810","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":"Strong and weak interactions of a V-shaped premixed swirling flame with outer vortex rings","authors":"Yongzhi Ren,&nbsp;Qiuxiao Wang,&nbsp;Yuqian Peng,&nbsp;Liangliang Xu,&nbsp;Xi Xia,&nbsp;Fei Qi","doi":"10.1016/j.combustflame.2024.113760","DOIUrl":"10.1016/j.combustflame.2024.113760","url":null,"abstract":"<div><div>This paper reports two distinct vortex-flame interaction mechanisms existing in a self-excited V-shaped premixed flame. Time-resolved simultaneous measurements of particle image velocimetry (PIV) and OH* chemiluminescence are employed to capture the mean and coherent flow and flame structures. The qualitative study demonstrates the importance of the outer vortex rings (OVR) in governing the flame front dynamics of two representative lean and near-stoichiometric cases. The interaction of the flame with the OVRs is further analyzed quantitatively during one OVR's entire lifespan. Results suggest that the vortex-flame interaction in the lean case is a weak one as the response of the flame's HRR to OVR's growth is interrupted by the tip extinction. This can be understood as a response to the flow perturbation excited in the Helmholtz mode of the plenum. However, the near-stoichiometric case yields a strong interaction that the peak HRR is synchronized with the OVR's peak circulation, which could contribute to a stronger thermoacoustic coupling that leads to the stronger pressure oscillation and frequency drift away from the Helmholtz mode.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113760"},"PeriodicalIF":5.8,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423853","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":"Three-dimensional simulations of NEPE propellant combustion under depressurization effects","authors":"Kaixuan Chen ,&nbsp;Zhenwei Ye ,&nbsp;Yizhe Yu ,&nbsp;Xiaochun Xue ,&nbsp;Yonggang Yu","doi":"10.1016/j.combustflame.2024.113785","DOIUrl":"10.1016/j.combustflame.2024.113785","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113785"},"PeriodicalIF":5.8,"publicationDate":"2024-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423852","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":"Physiochemical View of Fuel Jet Impingement and Ignition Upon Contact with a Cylindrical Hot Surface","authors":"Sayop Kim ,&nbsp;Tonghun Lee ,&nbsp;Kenneth S. Kim ,&nbsp;Chol-Bum M. Kweon ,&nbsp;Je Ir Ryu","doi":"10.1016/j.combustflame.2024.113784","DOIUrl":"10.1016/j.combustflame.2024.113784","url":null,"abstract":"<div><div>This study delves into ignition and flame dynamics involving a cylindrical hot surface impact. Previous studies have focused on the flat-wall hot surface interacting with fuel spray, leaving gaps in understanding the effects of cylindrical hot surfaces on fuel-air mixing and ignition. Using high-fidelity large-eddy simulations (LES), this study investigates how fluid elements, upon contacting an electronically activated glow plug structure, exhibit mixing and thermochemical properties. The analysis examines how this type of structure enhances fuel-air mixing and subsequently influences the thermochemistry behavior in conjunction with the fuel-specific combustion behavior. The study includes scenarios with free spray and non-thermal deposit cases to assess their mixing impact, alongside testing five different electric voltage inputs to study the thermally assisted ignition process. Results demonstrate that the cylindrical structure hinders flow, reducing its inertia and increasing flow residence time. Moreover, a significant Coandă effect due to the circular wall structure is identified, potentially serving as a mechanism for enhancing flame-holding. Furthermore, varying the input voltage notably affects ignition timing, revealing a non-monotonic ignition delay pattern with lower voltages. Detailed analysis highlights the critical role of negative temperature coefficient (NTC)-driven low-temperature chemistry (LTC) in the ignition process.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113784"},"PeriodicalIF":5.8,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423829","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":"Liquid fuel cloud detonation and droplet lifetime","authors":"Taylor Brown,&nbsp;Rachel Hytovick,&nbsp;Anthony Morales,&nbsp;Joshua Berson,&nbsp;Sheikh Salauddin,&nbsp;Khaoula Chougag,&nbsp;Kareem Ahmed","doi":"10.1016/j.combustflame.2024.113786","DOIUrl":"10.1016/j.combustflame.2024.113786","url":null,"abstract":"<div><div>The structures and mechanisms of aerosolized liquid-fuel cloud detonations are studied in a detonation facility using simultaneous high-speed optical diagnostics. The characteristic length scale of the droplet lifetime in liquid fuel detonations is not well predicted by established breakup and evaporation models, whereas it captured by calculations of the evaporation time of the droplet cloud.</div></div><div><h3>Novelty and significance statement</h3><div>Detonation research has mostly focused on gaseous fuels with limited investigations of purely liquid fueled detonations. This research explores the characteristic length scales of aerosolized liquid fuel droplets’ lifetime showing it does not scale with established breakup and evaporation models. It scales well with the evaporation time of child droplet clouds, highlighting the significance.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113786"},"PeriodicalIF":5.8,"publicationDate":"2024-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423830","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":"Direct numerical simulations of turbulent premixed cool flames: Global and local flame dynamics analysis","authors":"Yiqing Wang ,&nbsp;Chao Xu ,&nbsp;Cheng Chi ,&nbsp;Zheng Chen","doi":"10.1016/j.combustflame.2024.113759","DOIUrl":"10.1016/j.combustflame.2024.113759","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The cool flame dynamics, especially in turbulent flows, is of great interest for both practical application and fundamental research. In this study, a series of direct numerical simulations of turbulent premixed &lt;em&gt;n&lt;/em&gt;-C&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;7&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;H&lt;sub&gt;16&lt;/sub&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;/O&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;/N&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; cool flames are performed, with the focus on the influence of turbulence intensity (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;u&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;/&lt;/mo&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;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, where &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; is the laminar flame speed) on the flame structure as well as the global and local cool flame dynamics. It is found that the cool flame front is considerably wrinkled by turbulence at high &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;u&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;/&lt;/mo&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;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, leading to significantly thickened turbulent cool flame brush and largely altered local reactivity compared with the reference laminar flame. However, the turbulent flame structure in the temperature space is found to be insensitive to &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;u&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;/&lt;/mo&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;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. Besides, with increasing &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;u&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;/&lt;/mo&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;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, the normalized turbulent cool flame speed (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;/&lt;/mo&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;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) is monotonically increased, attributed to substantial augmentation on the flame surface area (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;A&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;A&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;), while the stretching factor (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;I&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) remains almost constant and is smaller than 1. The underlying mechanisms for such variations are revealed through local flame dynamics analysis. Specifically, the local flame displacement 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;d&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; is found to be strongly negatively correlated with flame curvature; meanwhile, such negative correlation and the probability distribution function (PDF) of flame curvature are barely influenced by &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;u&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;/mrow&gt;&lt;/ms","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113759"},"PeriodicalIF":5.8,"publicationDate":"2024-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423851","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":"The universal gaseous detonation dynamics","authors":"Qiang Xiao ,&nbsp;Qibin Zhang ,&nbsp;Ashwin Chinnayya","doi":"10.1016/j.combustflame.2024.113757","DOIUrl":"10.1016/j.combustflame.2024.113757","url":null,"abstract":"<div><div>The present communication proposes a new scaling approach to unify the dynamics of gaseous detonations subject to wall losses in both the narrow channels and small tubes, by compiling the published experimental data of detonations in 23 different mixtures with a very large range of cellular instabilities. A kinetic induction length <span><math><msub><mrow><mi>Δ</mi></mrow><mrow><mi>i</mi><mo>,</mo><mi>l</mi><mi>o</mi><mi>s</mi><mi>s</mi></mrow></msub></math></span> can be determined from the detonation velocity deficit and detailed chemistry. In order to take into account the sensitivity of the latter length to post-shock temperature fluctuations (through the reduced activation energy <span><math><mi>θ</mi></math></span>), which is a partial and indirect marker of the cellular structure, and to bring out energetics (through the Chapman–Jouguet detonation Mach number <span><math><msub><mrow><mi>M</mi></mrow><mrow><mi>C</mi><mi>J</mi></mrow></msub></math></span>), an effective kinetic length of <span><math><mrow><msub><mrow><mi>Δ</mi></mrow><mrow><mi>i</mi><mo>,</mo><mi>l</mi><mi>o</mi><mi>s</mi><mi>s</mi></mrow></msub><mspace></mspace><mrow><mo>(</mo><msubsup><mrow><mi>M</mi></mrow><mrow><mi>C</mi><mi>J</mi></mrow><mrow><mn>4</mn></mrow></msubsup><mo>/</mo><msup><mrow><mi>θ</mi></mrow><mrow><mn>3</mn></mrow></msup><mo>)</mo></mrow></mrow></math></span> was built and has been shown to collapse the different detonation dynamics of various gaseous mixtures, subjected to wall losses, into a single universal curve for detonation velocity deficits.</div><div><strong>Novelty and Significance:</strong> Scaling analysis of large sets of published data of gaseous detonation experiments in narrow channels and small tubes has been made for 23 different mixtures with varied cellular instabilities and activation energies. The universal dynamics of gaseous detonations subject to wall losses in different mixtures has been achieved, for the first time, by adopting an effective kinetic length by taking into account the effect of both the activation energy and the energetics.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113757"},"PeriodicalIF":5.8,"publicationDate":"2024-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423811","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":"Investigating the oxidation characteristic of a hydro-processed bio-jet fuel: Experimental and modeling study","authors":"Yilun Liang ,&nbsp;Xuantong Liu ,&nbsp;Mo Yang ,&nbsp;Xin Hui ,&nbsp;Juan Wang","doi":"10.1016/j.combustflame.2024.113778","DOIUrl":"10.1016/j.combustflame.2024.113778","url":null,"abstract":"<div><div>A rapid transition from conventional jet fuels to sustainable aviation fuels (SAFs) is imperative in order to reduce carbon emissions. Hydro-processed esters and fatty acids synthetic paraffinic kerosene (HEFA-SPK), as a type of SAF, exhibits broad applications. In this study, a new HEFA-SPK named ZH-HEFA was investigated. The fuel comprises 14% n-alkanes, 85% iso-alkanes and only 1% cycloalkanes by weight, with the majority of alkanes ranging from C₉ to C₁₇. Oxidation experiments of the fuel were conducted using an atmospheric pressure flow reactor at temperatures ranging from 550 K to 1075 K under three equivalence ratios (0.5, 1.0 and 1.5). Species mole fraction profiles were measured by an on-line gas chromatographic (GC). For comparison purposes, an experiment was also performed on RP-3, a conventional jet fuel commonly used in China, under the equivalence of 0.5. Compared to RP-3, ZH-HEFA exhibited significantly stronger low temperature reactivity and higher combustion conversion rates while demonstrating considerably lower yields of aromatics at high temperatures. The kinetic simulation of ZH-HEFA was achieved by proposing two surrogates and their corresponding kinetic models. Surrogate S-1 consisted solely of n-dodecane, while S-2 comprised 35% n-dodecane and 65% 2,6,10-trimethyl dodecane by weight. Both surrogate models were validated by the experimental data. S-1 exhibited a closer resemblance to the global oxidation characteristics of ZH-HEFA, whereas S-2 demonstrated improved accuracy in predicting the formation of small hydrocarbon intermediates during the fuel oxidation. Rate of production analysis revealed that the branched alkane component in S-2 possessed more pathways and greater capability than S-1 in generating C₃ intermediates, which are important for the generation of aromatics. Furthermore, both models displayed good predictive performance for the auto-ignition properties of HEFA-SPK fuels.-</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113778"},"PeriodicalIF":5.8,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423828","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":"ReaxFF molecular dynamics study of N-containing PAHs formation in the pyrolysis of C2H4/NH3 mixtures","authors":"Kai Zhang ,&nbsp;Yishu Xu ,&nbsp;Ronghao Yu ,&nbsp;Hui Wu ,&nbsp;Xiaowei Liu ,&nbsp;Xiaobei Cheng","doi":"10.1016/j.combustflame.2024.113774","DOIUrl":"10.1016/j.combustflame.2024.113774","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113774"},"PeriodicalIF":5.8,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423831","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}