Combustion and Flame最新文献

{"title":"Volumetric heat release, fuel-air mixing and turbulent dissipation of vertically-downward turbulent nonpremixed jet flames under sub-atmospheric pressures","authors":"Hongyu Lu , Jiang Lv , Xiaolei Zhang , Jong Moon Lee , Chun Sang Yoo , Suk Ho Chung , Longhua Hu","doi":"10.1016/j.combustflame.2025.114161","DOIUrl":"10.1016/j.combustflame.2025.114161","url":null,"abstract":"<div><div>In this study, volumetric heat release rate (related to flame radiation characteristics), fuel-air mixing, and turbulent dissipation rate of vertically-downward nonpremixed jet flames under standard- and various sub-atmospheric pressures are investigated, which have not been quantified yet. The interaction of downward jet momentum and upward buoyancy influences flow turbulence and fuel-air mixing. Experiments are conducted in a reduced-pressure chamber with controlled ambient pressures from 40 to 101 kPa. The flame volume and volumetric heat release rate are experimentally determined through image processing. Three-dimensional large eddy simulations are performed to further understand fuel-air mixing and flame behaviors. A quantitative agreement is obtained between the measured and calculated flame volumes. Results show that the turbulent dissipation rate <span><math><mrow><mi>ε</mi></mrow></math></span> of vertically-downward jet flame is stronger and distributes more broadly than that of the upward jet flame because of the rapid deceleration of jet momentum by the buoyancy. As the pressure decreases, more intense turbulent kinetic energy and turbulence dissipation rate are observed. The flame volume <em>V</em><sub>f</sub> for the vertically-downward jet flame is found to increase as heat release rate <span><math><mover><mi>Q</mi><mo>˙</mo></mover></math></span> increases and decreases with the increase of ambient pressure. The flame volume has a power relation as <span><math><mrow><msub><mi>V</mi><mi>f</mi></msub><mrow><mspace></mspace><mo>∼</mo><mspace></mspace></mrow><msup><mrow><mover><mi>Q</mi><mo>˙</mo></mover></mrow><mrow><mn>10</mn><mo>/</mo><mn>7</mn></mrow></msup></mrow></math></span> and on ambient pressure <em>P</em><sub>c</sub> as <span><math><mrow><msub><mi>V</mi><mi>f</mi></msub><mo>∼</mo><msubsup><mi>P</mi><mrow><mi>c</mi></mrow><mrow><mo>−</mo><mrow><mn>4</mn><mo>/</mo><mn>7</mn></mrow></mrow></msubsup></mrow></math></span>. Moreover, the volumetric heat release rate scales satisfactorily with <em>P</em><sub>c</sub> as <span><math><mrow><mover><mi>Q</mi><mo>˙</mo></mover><mrow><msup><mrow></mrow><mrow><mo>″</mo><mo>′</mo></mrow></msup><mo>∼</mo></mrow><msubsup><mi>P</mi><mrow><mi>c</mi></mrow><mrow><mn>4</mn><mo>/</mo><mn>7</mn></mrow></msubsup></mrow></math></span>. The differences of <em>V</em><sub>f</sub> (or <span><math><mrow><mover><mi>Q</mi><mo>˙</mo></mover><msup><mrow></mrow><mrow><mo>″</mo><mo>′</mo></mrow></msup></mrow></math></span>) among pool-type flame (purely buoyancy driven), upward jet flame and downward jet flame are revealed and explained by turbulent dissipation rate and fuel-air mixing characteristics. A general global dimensionless model for flame volume of downward jet flame is proposed by taking into account the initial jet momentum, flame buoyancy, and ambient air pressure, in which a new dimensionless heat release rate is defined based on two derived length scales (momentum-buoyancy competitio","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114161"},"PeriodicalIF":5.8,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143835315","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":"Experimental and modeling investigation of nitrogen-containing product formation during N,N-dimethylformamide (DMF) oxidation in a jet-stirred reactor (JSR)","authors":"Su Zhang,&nbsp;Fuheng Xia,&nbsp;Meijun Fan,&nbsp;Yixiang Zhang,&nbsp;Guan Wang,&nbsp;Bin Liu,&nbsp;Yongqiang Chen,&nbsp;Yili Zhang,&nbsp;Renhui Ruan,&nbsp;Xuebin Wang","doi":"10.1016/j.combustflame.2025.114188","DOIUrl":"10.1016/j.combustflame.2025.114188","url":null,"abstract":"<div><div>The oxidation of N, N-dimethylformamide (DMF) was investigated both experimentally and numerically. Experiments were carried out in a fused silica jet-stirred reactor (JSR) under atmospheric pressure covering a temperature range of <em>T</em> = 500–900 °C with different equivalence ratio (φ=0.5, 0.7, 0.9 and 1.2). A detailed analysis of the main nitrogen-containing products and intermediates was performed, and the results were interpreted with an improved kinetic model, describing the oxidation mechanism of DMF and the nitrogen conversion path. The measurements suggest that the primary nitrogen-containing products of DMF oxidation are HCN, NO, and N₂O, with HCN identified as a key intermediate. Kinetic analysis shows that higher temperatures promote H₂CN decomposition to stimulates the production of HCN, while increased O₂ levels enhance OH radical production, which facilitates the conversion of HCN to NO and N₂O. At 750 °C, flux analysis elucidated the main conversion pathways for NO and N₂O, providing valuable information for optimizing combustion and emissions control processes. The main conversion pathway of NO is Fuel-N→CH₃N(CH₂)CHO→CH₃NCH₂→CH₂NCH₂→H₂CN→HCN→NCO→HNCO→NH₂→H₂NO→HNO→NO, while the main conversion pathway of N₂O is Fuel-N→CH₃N(CH₂)CHO→CH₃NCH₂→CH₂NCH₂→H₂CN→HCN→NCO→N₂O. The findings offer important implications for reducing nitrogen-based pollutants in industrial applications, contributing to a more sustainable approach to DMF oxidation.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114188"},"PeriodicalIF":5.8,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143839445","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":"Effect of combustor pressure on emissions in flameless combustion mode: An experimental and computational investigation","authors":"Mohammad Kalamuddin Ansari,&nbsp;Rajat Soni,&nbsp;Deepak Prakash,&nbsp;Sudarshan Kumar","doi":"10.1016/j.combustflame.2025.114172","DOIUrl":"10.1016/j.combustflame.2025.114172","url":null,"abstract":"<div><div>Several experimental and numerical studies show complex trends of NO_x formation at elevated pressures. The present study aims to address this aspect through both experimental and computational investigations and reports the combustion characteristics of flameless combustion with gaseous fuel at elevated pressure conditions. The work focuses on understanding the effects of pressure, residence time, and air jet diameter on NO_x and CO emissions from a laboratory-scale flameless burner operating with LPG fuel up to 2 bar absolute pressure. A conical combustor with tangential air injection and central fuel injection is employed to generate strong recirculation of hot combustion products within the combustor volume. Comprehensive CFD analysis reveals the influence of air injection velocity and operating pressure on flow recirculation patterns, temperature uniformity, and residence time distribution within the combustor. The numerical simulations show the formation of significant recirculation zones and thermally uniform regions, measured using the reactant dilution ratio (<span><math><msub><mi>R</mi><mrow><mi>d</mi><mi>i</mi><mi>l</mi></mrow></msub></math></span>) and temperature uniformity index (<span><math><msub><mi>R</mi><mrow><mi>t</mi><mi>u</mi></mrow></msub></math></span>​). All cases exhibit a maximum <span><math><msub><mi>R</mi><mrow><mi>d</mi><mi>i</mi><mi>l</mi></mrow></msub></math></span> ​ greater than 2.5, which ensures the presence of a sufficiently heated and diluted environment conducive for sustaining flameless combustion under high-pressure conditions. A temperature uniformity index, <span><math><msub><mi>R</mi><mrow><mi>t</mi><mi>u</mi></mrow></msub></math></span>, exceeding 0.9 indicates the formation of a uniform thermal field with minimal variation in the combustor volume. This study helps establish a detailed relationship between elevated pressure and its impact on CO and NO_x emissions. Increased combustor pressure is shown to reduce the <span><math><msub><mi>R</mi><mrow><mi>d</mi><mi>i</mi><mi>l</mi></mrow></msub></math></span>, leading to higher NO_x emissions due to reduced flow rate, lower injection velocities, and increased residence time within the combustor volume. This results in a simultaneous reduction of CO emissions OH* chemiluminescence studies revealed an increased homogeneity in OH* species distribution during the flameless combustion mode with a reduction in the maximum combustion intensity.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114172"},"PeriodicalIF":5.8,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834719","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":"Study on the mechanism of polycyclic aromatic hydrocarbons and soot formation in ethylene/hydrogen/ammonia laminar diffusion flames","authors":"Yang Wang ,&nbsp;Ke Liu ,&nbsp;Kun Luo ,&nbsp;Kunzhuo Chang ,&nbsp;Mingyan Gu","doi":"10.1016/j.combustflame.2025.114168","DOIUrl":"10.1016/j.combustflame.2025.114168","url":null,"abstract":"<div><div>Ammonia, as an excellent zero-carbon hydrogen storage energy source, presents a significant research focus in the field of combustion regarding how to achieve efficient and clean combustion. The combustion of hydrocarbon fuels with hydrogen-ammonia addition can enhance ammonia combustion performance, reduce carbon emissions from hydrocarbon fuels, and control soot formation; however, the underlying mechanisms remain unclear. This study uses the CoFlame code to simulate the evolution of soot formation in ethylene/hydrogen/ammonia co-flow laminar diffusion flames and analyzes the mechanisms of polycyclic aromatic hydrocarbons formation and growth influenced by hydrogen-ammonia addition. The study found that the predicted soot volume fraction and average primary particle diameter align well with experimental measurements, indicating that the suppressive effect of hydrogen-ammonia addition increases as the hydrogen/ammonia ratio decreases. The addition of hydrogen-ammonia suppresses the nucleation, surface growth, and agglomeration processes of soot in the ethylene flame. The normalization study indicates that the rates of soot nucleation and surface growth align more closely with the evolution of soot volume fraction, making them the primary contributors to the reduction in soot volume fraction. This is identified as the primary reason for the reduction in soot volume fraction. Reaction pathway analysis indicates that the most significant reaction pathway for the gradual formation of pyrene from A₁ under the influence of small molecular components and free radicals in the ethylene/hydrogen/ammonia flame is as follows: A₁→indene→indenyl→A₂R₅→A₂→A₂⁻→A₃⁻→A₄. Quantitative analysis reveals that the chemical effect of hydrogen-ammonia addition effectively suppresses the hydrogen extraction reaction of A₂ by reducing the concentration of hydrogen radicals, thereby decreasing the formation rate of A₄.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114168"},"PeriodicalIF":5.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834720","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":"On the effect of RDX inclusion in an AP/HTPB composite propellant: A numerical study with detailed kinetics","authors":"Pierre Bernigaud ,&nbsp;Dmitry Davidenko ,&nbsp;Laurent Catoire","doi":"10.1016/j.combustflame.2025.114162","DOIUrl":"10.1016/j.combustflame.2025.114162","url":null,"abstract":"<div><div>In this work, the effect of hexogen (RDX) inclusion in a conventional ammonium perchlorate (AP)/hydroxyl-terminated polybutadiene (HTPB) composite propellant is investigated. To this end, a detailed gas-phase kinetic mechanism for the ternary system AP/HTPB/RDX is proposed. A revised vapour pressure law is used to model RDX evaporation. The combustion model is able to represent the chemical processes within the flame produced by the combustion of pure AP, homogenized AP/HTPB pseudo-propellants, and pure RDX. With this kinetic model, the combustion of a single RDX particle surrounded by a layer of homogenized AP/HTPB binder is simulated in a 2D axisymmetric configuration. It is shown that RDX inclusion significantly alters the combustion of the propellant. A phenomenological description of the flame structure forming above the heterogeneous propellant is proposed. This flame does not conform to the Beckstead–Derr–Price model, usually valid for conventional AP/HTPB propellants. Ambient pressure and RDX particle size are varied to assess the effect of these key parameters on the combustion. Two combustion regimes are identified: the hot and mild regimes. Conditions for the appearance of each combustion regime are determined in terms of ambient pressure and RDX particle size.</div><div><strong>Novelty and Significance</strong></div><div>Composite propellants could include nitramine ingredients such as hexogen (RDX) in their formulation to improve their performance. The effect of RDX inclusion in a conventional ammonium perchlorate (AP) / hydroxyl-terminated polybutadiene (HTPB) propellant was experimentally studied in the past <span><span>[1]</span></span>, <span><span>[2]</span></span>. However, understanding the fine combustion processes at stake remained out of reach. On the other hand, numerical simulation of the combustion was unachievable, as no gas-phase kinetic mechanism for the ternary system AP/HTPB/RDX was available. This paper first proposes such a kinetic model based on previous work by the authors on pure AP <span><span>[3]</span></span> and AP/HTPB combustion <span><span>[4]</span></span>. In doing so, a revised vapour pressure law is proposed for RDX combustion. With this mechanism, the flame structure obtained above an AP/HTPB/RDX propellant is computed. RDX inclusion significantly alters the combustion of the AP/HTPB propellant via specific processes, which are highlighted.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114162"},"PeriodicalIF":5.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143828297","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":"Assessment of the Flamelet Generated Manifold method with preferential diffusion modeling for partially premixed hydrogen flames","authors":"E.J. Pérez-Sánchez,&nbsp;E.M. Fortes,&nbsp;D. Mira","doi":"10.1016/j.combustflame.2025.114141","DOIUrl":"10.1016/j.combustflame.2025.114141","url":null,"abstract":"<div><div>This study presents a systematic analysis of the capabilities of a flamelet model based on Flamelet Generated Manifolds (FGM) to reproduce preferential diffusion effects in partially premixed hydrogen flames. Detailed transport effects are accounted for by including a mixture-averaged transport model when building the flamelet database. This approach adds new terms into the diffusive fluxes of the transport equations of the controlling variables coming from a set of coefficients computed from the data contained in the manifold. The manifold is constructed from the solution of a set of unstretched adiabatic one-dimensional premixed flames within the flammability range using mixture-averaged transport. Special attention is given to the numerical aspects related to the construction of the chemical manifold and how to reduce the numerical errors when evaluating the gradients in composition space required for the fluxes. Finally, a systematic application of the method to simulate laminar hydrogen flames in various canonical configurations is presented from premixed to stratified flames, including the case of a triple flame with different mixing lengths. The results demonstrate that the method describes accurately the flame structure and propagation velocities at a low cost, showing a remarkable agreement with the detailed chemistry solutions for flame structure and propagation speed.</div><div><strong>Novelty and significance statement</strong></div><div>The novelty of the paper lies on the presentation of an extended, robust and comprehensive model for tabulated chemistry incorporating mixture-averaged diffusion. The paper demonstrates the suitability of the model to describe stratified flames when preferential diffusion effects are important by simulating a relevant set of canonical flame configurations. The significance of the paper is that it allows to accurately reproduce a complex phenomenon as it is differential diffusion by the application of a tabulated method, without introducing overheads, and allowing to drastically reduce the computational cost of the simulations.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114141"},"PeriodicalIF":5.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143828296","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":"An improved machine learning method for thermochemistry tabulation, with application to LES-PDF simulations of piloted diffusion and swirl-bluff-body stabilised flames with NOx formation","authors":"Tianjie Ding,&nbsp;W.P. Jones,&nbsp;Stelios Rigopoulos","doi":"10.1016/j.combustflame.2025.114130","DOIUrl":"10.1016/j.combustflame.2025.114130","url":null,"abstract":"<div><div>Many turbulent combustion modelling approaches require real-time computation of reaction source terms, which is time-consuming and represents a bottleneck of turbulent combustion simulations. In order to speed up the reaction computation process, an artificial neural network (ANN) thermochemistry tabulation methodology has been proposed and developed in our previous work (Ding et al., 2021). In the present work, this methodology is further developed and applied to thermochemistry that includes NO_x formation, which poses further challenges due to the small concentrations of the N-containing species. In particular, we build on the Multiple Multilayer Perceptrons (MMLP) concept, which aims to improve prediction accuracy by systematically combining multiple ANNs. A new method, MMLP-II, is proposed in this work, which trains different ANNs to predict states with different ranges of initial species concentration, in contrast to the previous MMLP-I method which trains several ANNs with different ranges of output magnitude. Both MMLP methods are applied to tabulate the complete GRI-3.0 mechanism and the resulting ANNs are tested on two different turbulent methane flames: Sandia flame D and Sydney flame SMA2. It is found that MMLP-II method can reduce the ANN error accumulation of minor species, and very accurate results are obtained in both turbulent flames. The successful application to two different turbulent combustion problems is indicative of the capacity for generalisation of the ANN tabulation approach. Finally, the reaction integration step is accelerated by a factor of about 15 with ANNs, thus rendering chemical kinetics no longer the bottleneck of the whole simulation.</div><div><strong>Novelty and significance</strong></div><div>A new ANN thermochemistry tabulation methodology is developed, aimed at providing the higher accuracy needed for predicting species with small concentrations, as encountered in NO_x chemistry. The methodology is applied to two different turbulent flames with NO_x formation: a piloted diffusion flame (Sandia D) and a swirl-bluff-body stabilised flame (Sydney SMA2). The results demonstrate that the method provides both high accuracy and capacity for generalisation. The LES-PDF method is employed here, but the method is applicable to any method that involves real-time calculation of thermochemistry.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114130"},"PeriodicalIF":5.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143829666","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":"Direct measurement of the NH3+OH reaction rate behind incident and reflected shock waves","authors":"Luke T. Zaczek,&nbsp;Sean Clees,&nbsp;Ronald K. Hanson","doi":"10.1016/j.combustflame.2025.114174","DOIUrl":"10.1016/j.combustflame.2025.114174","url":null,"abstract":"<div><div>A novel method was used to directly measure the reaction rate, <em>k₁</em>, of NH₃+OH&lt;=&gt;NH₂+H₂O in shock tube experiments behind incident and reflected shock waves from 910–2474 K and 0.23–3.59 atm. NH₃ concentration of test gases was measured prior to each shock with a scanned laser absorption NH₃ diagnostic near 10.36 µm. OH was produced via thermal decomposition of <em>tert</em>‑butyl hydroperoxide behind incident and reflected shock waves, and post-shock OH time-histories were measured via laser absorption at 308.6 nm. Measured OH profiles were fit with a detailed chemical kinetic model to find best-fit values for <em>k₁</em> at each experimental condition, and results are compared to previous data, calculations, and recommendations for the NH₃+OH reaction rate. To the authors’ knowledge, this is the first direct measurement of the NH₃+OH reaction rate above 1425 K and significantly reduces the uncertainty of <em>k₁</em> compared to previous indirect determinations at high temperatures. A recommendation is made for continued use of the NH₃+OH rate expression <em>k₁</em> = 10^6.31 T[K]^2.04 exp(-285/T[K]) cm³/ mol/s suggested by Salimian et al. from 230 &lt; <em>T</em> &lt; 2474 K, which agrees well with the current data and prior low-temperature measurements. The technique used in this work also provides a new strategy for direct measurement of +OH reaction rates at reflected-shock temperatures above ∼1450 K, which has previously been a practical high-temperature limit when using <em>tert</em>‑butyl hydroperoxide as a source of OH radicals.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114174"},"PeriodicalIF":5.8,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143828295","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 computational fluid dynamics model of combustion of nanoaluminum–water propellant strands","authors":"Prasanna Kulkarni,&nbsp;Ganeshkumar Venukumar,&nbsp;Dilip Sundaram","doi":"10.1016/j.combustflame.2025.114143","DOIUrl":"10.1016/j.combustflame.2025.114143","url":null,"abstract":"<div><div>A computational fluid dynamics model of combustion of nanoaluminum–water propellants is developed. An unsteady and axisymmetric model of strand combustion is developed to mimic the experimental setup and conditions. The entire time evolution of strand combustion from ignition until steady-state flame propagation through the strand is simulated. A multiphase Eulerian modeling approach is adopted to handle multiple phases and the associated transport processes. The mass, momentum, species, and energy conservation equations are discretized using the Finite Volume Method. A rigorous computational framework with superior accuracy and stability characteristics is developed and implemented. The theoretical and computational framework is first verified and validated by running standard test cases such as Stefan problem, fluidized bed, and constant-volume reactor. Upon verification and validation, the framework is applied to simulate combustion of stoichiometric nanoaluminum–water propellant strands. The particle size is chosen to be 80 nm and pressure range is taken as 1–10 MPa. The temporal evolutions of flow, temperature, and species composition fields are computed and insights into the underlying physicochemical processes are provided. Measurable quantities such as the burning rate and pressure exponent are computed. Both fixed bed and moving bed combustion scenarios are simulated and the effects of particle retainment in the propellant bed and particle agglomeration are studied. It is found that the multiphase flow dynamics strongly affect the burning rate and its pressure exponent. The present study suggests that the combustion of nano-aluminum and water propellants is diffusion-controlled due to agglomeration of particles.</div><div><strong>Novelty and significance statement</strong></div><div>A novel theoretical and computational framework is developed to simulate nano-aluminum and water propellant strand combustion. In a paradigm shift in the modeling and simulation approach, a Computational Fluid Dynamics (CFD) approach is adopted to simulate strand burning experiments as closely as possible. A comprehensive multiphase model is developed to resolve all underlying physiochemical processes including boiling of liquid water, multiphase flow dynamics, chemical reactions, and thermal transport. The entire time evolution from ignition until steady-state flame propagation is simulated for an axisymmetric propellant strand. The study provides new insights on the underlying processes that occur during the entire time history of propellant combustion. The simulations demonstrate the importance of multiphase flow dynamics and its impact on propellant combustion. It is discovered that the pressure dependence of burning rate of nano-aluminum and water propellant is primarily due to multiphase flow dynamics and that the combustion of nano-aluminum and water propellants is diffusion-controlled due to agglomeration of particles.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114143"},"PeriodicalIF":5.8,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143823206","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":"Radiative characterization detection and mechanism analysis of soot generation and oxidation during coal combustion based on hyperspectral and mid-wave infrared imaging techniques","authors":"Ke Chang,&nbsp;Meng Liu,&nbsp;Zixue Luo,&nbsp;Qiang Cheng","doi":"10.1016/j.combustflame.2025.114177","DOIUrl":"10.1016/j.combustflame.2025.114177","url":null,"abstract":"<div><div>The generation of soot during coal combustion is closely related to tar, and the incomplete combustion product soot competes with the complete oxidation product CO₂ during the combustion process. In this study, the light volatiles of coal particles are experimentally precipitated to obtain tar coal, and the simultaneous measurement of soot and CO₂ radiation characteristics is achieved by combining hyperspectral (HSI) and mid-wave infrared (MWIR) imaging technologies. Furthermore, the inherent competitive mechanism between the generation and oxidation of polycyclic aromatic hydrocarbons (PAHs) is revealed through mechanistic analysis. As the core structure of soot, PAHs have complex and diverse generation pathways. A1 is formed through both the C3 pathway involving odd-carbon atoms and the C2+C4 pathway involving even-carbon atoms. The generation of A2 to A4 is closely related to direct addition reactions on the benzene ring, and tar coal combustion corresponds to a higher generation rate of PAHs. The generation of soot and CO₂ during coal combustion is not sequential, but exists as a competitive relationship throughout the whole process. The experimental validation results show that the soot volume fraction from coal combustion ranges from 5 ppm to 20 ppm, and the CO₂ concentration ranges from 10 % to 25 %, with tar coal combustion corresponding to a higher content of soot and CO₂. Although the mole fraction of soot is much smaller than that of CO₂, solid soot particles have a more significant radiative capacity in terms of emission and absorption, with the spectral radiative intensity of soot being an order of magnitude higher than that of CO₂ during the stable combustion stage.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114177"},"PeriodicalIF":5.8,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143816677","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}