Combustion and Flame最新文献

{"title":"Effects of turbulence on variations in early development of hydrogen and iso-octane flame kernels under engine conditions","authors":"Hongchao Chu ,&nbsp;Lukas Berger ,&nbsp;Temistocle Grenga ,&nbsp;Michael Gauding ,&nbsp;Liming Cai ,&nbsp;Heinz Pitsch","doi":"10.1016/j.combustflame.2023.112914","DOIUrl":"https://doi.org/10.1016/j.combustflame.2023.112914","url":null,"abstract":"<div><p><span>The understanding and prediction of the early development of flame kernels are of high practical importance for the robust relight of aviation gas turbines and the control of cycle-to-cycle variations (CCV) of spark-ignition engines. CCV are known to correlate strongly with early flame kernel development and complicate the optimization of such engines in terms of safety, thermal efficiency, and engine emissions. The flame kernel initiated by a spark is initially small, in the very early combustion phase typically smaller than the size of the turbulent </span>integral length scales<span><span><span>. Therefore, the development of the flame kernel is dominated by local, intermittent flow<span> fluctuations and can vary under the same nominal conditions. In this study, the effects of turbulence on the early development of premixed iso-octane and hydrogen turbulent flame kernels under realistic engine conditions are investigated through direct numerical simulations<span>. Multiple realizations were simulated under the same nominal conditions for both fuels. Significant variations in flame kernel interactions with turbulence can be identified among different realizations. The fuel consumption rate varies by a factor of two, which is remarkable considering that only statistical differences in the local flow field are present between different realizations. Effects of different flow features of the initial flow fields on the flame kernel development were analyzed. It was found that the flow motion on the scale of the ignition radius, specifically the fluid deformation, which is characterized by the invariants of the strain </span></span></span>rate tensor<span>, determines the global shape of the kernel, while the variations of the kernel growth rate are mostly driven by the variations of the smallest turbulent scales. In particular, turbulence influences the flame surface area growth mainly through the tangential strain rate at the flame surface, which is shown to result from the small-scale turbulent motion. Due to differential diffusion effects, hydrogen and iso-octane exhibit significantly different flame responses to curvature, which is comprehensively studied for both fuels. The findings in this study will guide the development of combustion models that are capable to capture variations of the early flame kernels based on the </span></span>local turbulence<span> dissipation rate.</span></span></p></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"255 ","pages":"Article 112914"},"PeriodicalIF":4.4,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3450716","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":"Simulation and analysis of low-frequency instability in hot-fire test of a cryogenic hydrogen-oxygen preburner","authors":"Ya Zhang ,&nbsp;Liang Pan ,&nbsp;Qian Liu","doi":"10.1016/j.combustflame.2023.112874","DOIUrl":"https://doi.org/10.1016/j.combustflame.2023.112874","url":null,"abstract":"<div><p><span>Low-frequency chamber pressure oscillation is observed in the hot-fire test of a subscale cryogenic hydrogen-oxygen preburner. A lumped parameter simulation model with bipropellant </span>injector<span> is established by solving differential equations directly. Under the condition of constant inlet pressure<span>, the frequency of oscillation of combustion chamber pressure increases with the decrease of combustion delay, while the variation trend of amplitude of oscillation of chamber pressure is opposite. As the combustion delay decreases to 1.76 ms, the pressure oscillation gradually converges and stabilizes, but its initial oscillation frequency is still about 2.7 Hz lower than that of the test. In addition, the influence of the volume ratio of liquid propellant in the combustion chamber is analyzed. The combustion time delay is set to 1.76 ms, and the frequency and amplitude of the pressure oscillation increase with the increase of the liquid volume ratio. With the liquid volume ratio set at 2.8%, the frequency and amplitude obtained by simulation are in good agreement with the test. In order to reproduce the continuous oscillation of the combustion chamber pressure during the 30 s process in the test, the pre-injection pressure test curve varying with time is used as the inlet condition. The liquid volume ratio and combustion delay are empirically corrected in real time using propellant flow rate and mixture ratio, respectively. The continuous oscillation of the simulated pressure during the 30 s test was obtained, and its frequency value and trend are completely consistent with the test data. It can be inferred that low-frequency unstable combustion related to combustion delay may have occurred in the hot-fire test of the preburner.</span></span></p></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"255 ","pages":"Article 112874"},"PeriodicalIF":4.4,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2700570","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":"Improved reactivity and energy release performance of core-shell structured fuel-rich Si/PTFE energetic composites","authors":"Zhihua Zhuang ,&nbsp;Kedong Xu ,&nbsp;Baozhen Liu ,&nbsp;Yi Shi ,&nbsp;Shukui Li ,&nbsp;Zhaohu Liu ,&nbsp;Chuan He ,&nbsp;Jinxu Liu","doi":"10.1016/j.combustflame.2023.112889","DOIUrl":"https://doi.org/10.1016/j.combustflame.2023.112889","url":null,"abstract":"<div><p><span>Si is an attractive fuel in pyrotechnic applications due to its high gravimetric and </span>volumetric<span><span> energy density. In this article, core-shell structured fuel-rich Si/PTFE (CS-PSi) energetic composites were prepared through high-power ultrasonic mixing. The energy release performance of the CS-PSi composites with different equivalence ratios (ϕ=1.5, 2.5, and 3.5) is characterized, and the magnetic stirring mixed Si/PTFE (MS-PSi, ϕ=3.5) composite is also studied for comparison. For the CS-PSi composites, with the increase in equivalence ratio, the relative intensity and burning rate both increase. Evaluated in a closed vessel, the CS-PSi (ϕ=2.5) exhibits the optimum pressure performance in terms of peak pressure and </span>pressurization<span> rate. By modifying the equivalence ratio, the reactivity, as indicated by the pressurization rate, of the CS-PSi energetic composites can be tuned accordingly. Having the same equivalence ratio (ϕ=3.5), the relative intensity, burning rate, peak pressure, and pressurization rate of the CS-PSi composite are 6.1, 4.3, 1.3, and 4.1 times larger than those of MS-PSi counterpart, respectively, while the apparent activation energy of the CS-PSi composites is reduced by 23.6%. The improved reactivity and superior energy release performance of the CS-PSi composites can be attributed to the higher degree of intimacy between the reactants as a result of core-shell configuration. Our approach provides a facile and efficient way to elevate the performance of the Si/PTFE energetic composites.</span></span></p></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"255 ","pages":"Article 112889"},"PeriodicalIF":4.4,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2700573","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":"Multi-speciation in shock tube experiments using a single laser and deep neural networks","authors":"Mohamed Sy ,&nbsp;Mhanna Mhanna ,&nbsp;Aamir Farooq","doi":"10.1016/j.combustflame.2023.112929","DOIUrl":"https://doi.org/10.1016/j.combustflame.2023.112929","url":null,"abstract":"<div><p><span>Chemical kinetic experiments involving the oxidation<span> or pyrolysis<span> of fuels can be complex, especially when multiple species are formed and consumed simultaneously. Therefore, a diagnostic strategy that enables fast and selective detection of multiple species is highly desirable. In this work, we present a mid-infrared laser diagnostic that can simultaneously detect multiple species in high-temperature shock-tube experiments using a single laser. By tuning the wavelength of the laser over 3038 – 3039.6 cm</span></span></span>⁻¹<span> wavelength range and employing a denoising model based on deep neural networks<span><span> (DNN), we were able to differentiate the absorbance spectra of ethane, ethylene, methane, propane, and propylene. The denoising model is able to clean noisy absorbance spectra, and the denoised spectra are then split these into contributions from evolving species using multidimensional linear regression (MLR). To the best of our knowledge, this work represents the first successful implementation of time-resolved multispecies detection using a single narrow wavelength-tuning laser. To validate our methodology, we conducted pyrolysis experiments of ethane and propane. The results of our experiments showed excellent agreement with previous experimental data and chemical </span>kinetic model simulations. Overall, our diagnostic strategy represents a promising approach for detecting multiple species in high-temperature transient environments.</span></span></p></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"255 ","pages":"Article 112929"},"PeriodicalIF":4.4,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1634670","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":"Investigation of cellularization characteristics of hydrogen-methane-ethanol expanding spherical flame at elevated pressures","authors":"X.R. Wang ,&nbsp;Yan Zhang ,&nbsp;Tong Li ,&nbsp;Yin Ma ,&nbsp;Jiawei Zhang ,&nbsp;Cangsu Xu","doi":"10.1016/j.combustflame.2023.112866","DOIUrl":"https://doi.org/10.1016/j.combustflame.2023.112866","url":null,"abstract":"<div><p>The incorporation of ethanol into hydrocarbon fuels for use is attracting increasing interest and it is necessary to investigate its inherent flame instability for better application in combustion units. The instability of hydrogen-methane-ethanol spherically expanding flame has been investigated at an initial temperature of 400 K, initial pressures of (2–4 bar), ethanol fraction of (20%, 50%, 80%), and equivalence ratios (<em>Ф</em><span>) of (0.7–1.4) using the constant volume combustion chamber<span><span> (CVCC). High-speed schlieren technology was used to record flame propagation images. The effects of </span>hydrodynamic<span> and thermal-diffusion effect on the inherent instability of the flame were investigated. As the ethanol ratio increased, the hydrodynamic effect was enhanced. The thermal-diffusion effect was discovered to stabilize the flame surface under all conditions, as judged jointly by the effective Lewis number and the critical Lewis number. The critical conditions (critical radius and Peclet number) at the onset of unstability were evaluated, and it was found that the flames were more prone to flame instability at higher pressures. The critical Peclet number increased with the increase in the equivalence ratio when the ethanol ratio was 20%, and showed the opposite trend when the ethanol ratio was 50% and 80%. In addition, as the ethanol ratio increases, the stability of the lean mixtures flame increases, while the rich mixtures flame suffers from early onset of instability. The theoretical and experimental results were consistent, with some differences at </span></span></span><em>Ф =</em> 1.4. An empirical correlation formula for the critical Peclet number (<span><math><mrow><mi>P</mi><msub><mi>e</mi><mi>c</mi></msub></mrow></math></span><span>) and Markstein number (</span><em>M_b</em>) was further proposed (<span><math><mrow><mi>P</mi><msub><mi>e</mi><mi>c</mi></msub></mrow></math></span>= 18.03<em>M_b</em>+214.78). Finally, the Karlovitz number was used to study the instability behavior of the flame. The critical Karlovitz number (<em>Ka</em>_c) decreased with increasing <em>M_b</em> and the tendency of the flame to suffer from instability diminished, and the following correlation was obtained <span><math><mrow><mi>K</mi><msub><mi>a</mi><mi>c</mi></msub><mo>=</mo><mn>0.05635</mn><mo>×</mo><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo><mn>0.13852</mn><msub><mi>M</mi><mi>b</mi></msub></mrow></msup></mrow></math></span>. Furthermore, the flame was more unstable in rich mixtures, this was consistent with the conclusion of instability derived from the critical radius.</p></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"255 ","pages":"Article 112866"},"PeriodicalIF":4.4,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1885324","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":"Numerical investigation of NOx production from premixed hydrogen/methane fuel blends","authors":"B. Breer ,&nbsp;H. Rajagopalan ,&nbsp;C. Godbold ,&nbsp;H. Johnson II ,&nbsp;B. Emerson ,&nbsp;V. Acharya ,&nbsp;W. Sun ,&nbsp;D. Noble ,&nbsp;T. Lieuwen","doi":"10.1016/j.combustflame.2023.112920","DOIUrl":"https://doi.org/10.1016/j.combustflame.2023.112920","url":null,"abstract":"<div><p>Hydrogen (H₂) fuel is a promising means for long duration energy storage and dispatchable utilization of intermittent renewable power, which can be combusted without CO₂ emissions. Several recent studies have noted that hydrogen blended systems have elevated NO_x emissions relative to natural gas, prompting significant concerns about the air quality impacts of a hydrogen economy. However, many of these results are for nonpremixed systems and it is not entirely clear what is being held constant for these comparisons (temperature, power, etc.). Given the strong temperature sensitivity of NO_x production, these results cannot be applied more generally to understand NO_x emissions tendencies. This study reports calculations of NO emissions of perfectly premixed H₂/CH₄ blends at constant flame temperatures, presenting results as a function of residence time, over a range of pressure and temperature conditions. Four major findings are presented: (1) At constant temperature, NO emissions, quantified as mass per energy input, via ng/J, actually decrease with the addition of H₂ for NO measurements taken at typical gas turbine residence times (10–20 ms). This effect is less pronounced at elevated temperatures/pressures; (2) NO volume concentrations, when measured in a dried sample and corrected to 15% O₂, do not increase by the same amount as emissions quantified in ng/J over the same conditions. This demonstrates that one cannot directly compare volume concentration-based NO values when H₂ composition is varied; (3) the post-flame NO production rate negligibly increases with addition of H₂ at most conditions, especially at high power; (4) for realistic gas turbine combustor residence times, the dominant NO production under atmospheric pressure conditions occurs in the flame itself, while they occur post-flame via thermal-NO at practical high pressure conditions. In other words, atmospheric pressure fuel sensitivity NO_x studies will not capture the controlling NO production physics that are present in practical applications, such as gas turbines.</p></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"255 ","pages":"Article 112920"},"PeriodicalIF":4.4,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1886104","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":"Structure and propagation of spherical turbulent iron-methane hybrid flame at elevated pressure","authors":"Xiao Cai ,&nbsp;Shouguo Su ,&nbsp;Limin Su ,&nbsp;Jinhua Wang ,&nbsp;Marcus Alden ,&nbsp;Zhongshan Li ,&nbsp;Zuohua Huang","doi":"10.1016/j.combustflame.2023.112918","DOIUrl":"https://doi.org/10.1016/j.combustflame.2023.112918","url":null,"abstract":"<div><p><span>In this communication we demonstrate the role of turbulence intensity in the dual-front structure and self-similar propagation of spherical turbulent iron-methane hybrid flames. We first show that iron-methane hybrid mixture, whose iron concentration is below a critical threshold for the formation of a dust flame front in laminar or weak turbulent environment, can be burned strongly with both separated dual-front and merged single-front structures in intense turbulence. It is suggested that the formation of iron flame front would be attributed to local iron concentration accumulation by preferential sampling with near-unity Stocks number (</span><em>St</em><span>), heat transfer enhancement of iron particles to fluid and mixing promotion of iron particles with oxidants by strong turbulence. The propagation of iron front falls behind the methane front in the leading segments which is promoted by flame stretch for sub-unity Lewis number (</span><em>Le</em>), thus the separated dual-front structure occurs. Furthermore, the strong self-similar propagation of spherical turbulent iron-methane hybrid flame was observed under different turbulence intensities (<em>u_rms</em>). Mechanistically, such strong self-similar propagation of the hybrid flame is the consequence of the couple effects of flame mode transition at high <em>u_rms</em> with near-unity <em>St</em> and differential diffusion for sub-unity <em>Le</em>.</p></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"255 ","pages":"Article 112918"},"PeriodicalIF":4.4,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1886105","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":"OH-PLIF study on the mechanism regulating flame-wall interaction with catalytically active CeO2-ZrO2 coatings","authors":"Fan Li ,&nbsp;Haolin Yang ,&nbsp;Runjie Deng ,&nbsp;Li Guo ,&nbsp;Yue Ye ,&nbsp;Yuxuan Wu ,&nbsp;Kangwei Xu ,&nbsp;Liqiao Jiang ,&nbsp;Xiaohan Wang","doi":"10.1016/j.combustflame.2023.112917","DOIUrl":"https://doi.org/10.1016/j.combustflame.2023.112917","url":null,"abstract":"<div><p>Technically, using catalytically active coatings regulate flame-wall interactions to enhance flame stability in small-scale burners, such as the common ZrO₂-based ceramics with doping CeO₂<span> which benefit to improve the high-temperature mobility and reactivity of lattice oxygen as an oxygen source to promote gas phase combustion. Probing by OH-PLIF laser diagnosis, the aim of this study was to investigate the dopant content effect (0–20 wt.% CeO</span>₂) on the flame characteristics of methane-air mixtures of varying equivalence ratio (0.9, 1.0, and 1.2) in an adjustable-gap narrow channel (2–12 mm) at a wall temperature range of 373 K to 973 K, including the dynamic flame morphology, flame quenching performance, and near-wall spatial distribution of OH radicals. Results show that the flame-wall distances are strongly correlated with wall temperature, equivalence ratio, and channel scale. After doping CeO₂, the measured quenching distances can significantly drop, but do not show a linear downward trend with increasing CeO₂ content. The case of 5%CeO₂-ZrO₂<span> coating demonstrates a small critical quenching Peclet number<span> at high wall temperatures. The maximum OH fluorescence intensity in flame core areas increases with CeO</span></span>₂ doping into CeO₂-ZrO₂ at 973 K when the channel clearance is less than 4 mm. However, the absolute concentration of near-wall surviving OH radicals in the presence of 20%CeO₂-ZrO₂ coating is substantially lower than in the 5%CeO₂-ZrO₂ case due to differences in the redox properties. <em>In situ</em><span> diffuse reflectance infrared Fourier transformations spectroscopy tests further indicate that the adsorption quantities of C</span>₂H₄ and C₂H₆<span> species on the coating surface also show a non-monotonous CeO</span>₂ dependence, as they are important intermediates in the low-temperature C2 chain reaction of methane.</p></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"255 ","pages":"Article 112917"},"PeriodicalIF":4.4,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2700576","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 LES-FGM framework for capturing stable and unstable modes in a hydrogen / methane fuelled premixed combustor","authors":"Jen Zen Ho ,&nbsp;Sandeep Jella ,&nbsp;Mohsen Talei ,&nbsp;Gilles Bourque ,&nbsp;Thomas Indlekofer ,&nbsp;James Dawson","doi":"10.1016/j.combustflame.2023.112904","DOIUrl":"https://doi.org/10.1016/j.combustflame.2023.112904","url":null,"abstract":"<div><p>The main objective of this paper is to assess the capability of compressible Large Eddy Simulations<span><span> (LES) to capture azimuthal combustion instability. The thickened flame model coupled with </span>Flamelet<span> Generated Manifold (FGM) tabulated chemistry is used as the combustion model. LES of an annular combustor<span> is performed for five cases featuring stable and unstable combustion of hydrogen-methane mixtures. The unstable modes feature azimuthal instabilities and this annular combustor is used to test the LES-FGM framework. A consistent methodology is applied across all cases. It is found that LES predicts azimuthal modes for stable cases but these modes are weak and intermittent with pressure fluctuation amplitudes within the order of experimental noise. In addition, the unstable cases capture azimuthal modes that have approximately the same frequency as that of the experiment though the amplitudes of the modes are over-predicted. This suggests that the described LES-FGM framework is able to predict the onset of thermoacoustic instabilities and their qualitative changes with addition of hydrogen.</span></span></span></p></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"255 ","pages":"Article 112904"},"PeriodicalIF":4.4,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"1634666","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 flame speed enhancement in turbulent premixed hydrogen-air flames during local flame-flame interaction","authors":"Yuvraj ,&nbsp;Yazdan Naderzadeh Ardebili ,&nbsp;Wonsik Song ,&nbsp;Hong G. Im ,&nbsp;Chung K. Law ,&nbsp;Swetaprovo Chaudhuri","doi":"10.1016/j.combustflame.2023.113017","DOIUrl":"https://doi.org/10.1016/j.combustflame.2023.113017","url":null,"abstract":"&lt;div&gt;&lt;p&gt;Local flame displacement speed &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;&lt;span&gt; of a turbulent premixed flame is of fundamental and practical interest. For H&lt;/span&gt;&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;&lt;span&gt;-air flames, the interest is further accentuated given the recent drive towards the development of zero-carbon combustors&lt;span&gt; for both power and aircraft engine applications. The present study investigates several three-dimensional Direct Numerical Simulation (3D DNS) cases of premixed H&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;-air turbulent flames to theoretically model the &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;&lt;span&gt; at negative curvatures, building upon recent works. Two of the four DNS cases presented are simulated at atmospheric pressure and two at elevated pressure. The DNS cases at different turbulence Reynolds numbers (&lt;/span&gt;&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;mi&gt;t&lt;/mi&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) and Karlovitz numbers (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) are generated using detailed chemistry. It has been shown in the previous studies that at atmospheric pressure, the density-weighted flame displacement speed &lt;span&gt;&lt;math&gt;&lt;mover&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;mo&gt;˜&lt;/mo&gt;&lt;/mover&gt;&lt;/math&gt;&lt;/span&gt; is enhanced significantly over its laminar value (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) at large negative curvature &lt;span&gt;&lt;math&gt;&lt;mi&gt;κ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;&lt;span&gt; due to flame-flame interactions. The current work justifiably employs an imploding cylindrical laminar flame configuration to represent the local flame surfaces undergoing flame-flame interaction in a 3D turbulent flame. Therefore, to acquire a deep understanding of the interacting flame dynamics at large negative curvatures, one-dimensional (1D) simulations of an inwardly propagating cylindrical H&lt;/span&gt;&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;-air laminar premixed flame, with detailed chemistry at the corresponding atmospheric and elevated pressure conditions are performed. In particular, the 1D simulations emphasized the transient nature of the flame structure during these interactions. Based on the insights from the 1D simulations, we utilize an analytical approach to model the &lt;span&gt;&lt;math&gt;&lt;mover&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;mo&gt;˜&lt;/mo&gt;&lt;/mover&gt;&lt;/math&gt;&lt;/span&gt; at these regions of extreme negative &lt;span&gt;&lt;math&gt;&lt;mi&gt;κ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;&lt;span&gt; of the 3D DNS. The analytical approach is formulated to include the effect of variable density, convection and the inner reaction zone motion. The joint probability density function (JPDF) of &lt;/span&gt;&lt;span&gt;&lt;math&gt;&lt;mover&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;mo&gt;˜&lt;/mo&gt;&lt;/mover&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mi&gt;κ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; and the corresponding conditional averages obtained from 3D DNS showed clear negative correlation between &lt;","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"257 ","pages":"Article 113017"},"PeriodicalIF":4.4,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2824638","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}