Combustion and Flame最新文献

{"title":"Conversion of Al2O3 on micron-sized Al-Si surface to Al-MOFs:Realizing dual-functional regulation of enhanced reactivity and energy release design","authors":"Yuhao Wang ,&nbsp;Shutao Wang ,&nbsp;Shifa Cao ,&nbsp;Zechun Tian ,&nbsp;Jiayi Li ,&nbsp;Henan Chang ,&nbsp;Shuhong Ba","doi":"10.1016/j.combustflame.2026.114811","DOIUrl":"10.1016/j.combustflame.2026.114811","url":null,"abstract":"<div><div>Compared with pure aluminum (Al) particles, aluminum-silicon (Al-Si) particles possess significant advantages, including lower ignition temperature, more thorough oxidation reaction, and more stable combustion process, making them highly promising candidate fuels for composite energetic materials. However, the incorporation of Si into Al results in more severe particle agglomeration, and the native Al₂O₃ layer on the surface impedes energy release. This study adopts a simple one-step method to <em>in situ</em> convert the Al₂O₃ on the surface of micron-sized Al-Si particles into an aluminum-based metal-organic frameworks (Al-MOFs), thus providing an effective approach to solving the above-mentioned problems. The reactivity of the modified samples is significantly enhanced, and the design of energy release can be achieved. The specific manifestations are as follows: Al-Si@Al-MOFs demonstrate a dynamic secondary combustion process accompanied by deflagration. Its combustion peak pressure and pressurization rate are 1.27 and 49.21 times those of pristine Al-Si, respectively. By regulating the coating amount of Al-MOFs, the design of energy release can be achieved. The modified samples show a notable improvement in specific impulse performance, which remains at a high level over a wide oxidizer-to-fuel (O/F) ratio range. Additionally, the static water contact angle of the modified samples increases significantly, indicating enhanced surface hydrophobicity and effectively improved anti-aging performance. This study has successfully constructed bifunctional energetic particles featuring precise design of energy release and high reactivity, providing a new strategy for the development of advanced aerospace fuels.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114811"},"PeriodicalIF":6.2,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146036411","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":"Combustion instabilities of self-excited partially premixed hydrogen flames in a multi-element nozzle array combustor with varying mixing lengths","authors":"Yi Zhou ,&nbsp;Sixu Pu ,&nbsp;Guoyan Liu ,&nbsp;Ranran Xue ,&nbsp;He Su ,&nbsp;Liang Zhang ,&nbsp;Chuanlong Xu","doi":"10.1016/j.combustflame.2026.114850","DOIUrl":"10.1016/j.combustflame.2026.114850","url":null,"abstract":"<div><div>Partially premixed hydrogen combustion technology offers a promising approach to mitigate flashback risks while reducing greenhouse gas emissions in gas turbine applications. However, further research is required to fully comprehend the self-excited instability of partially premixed hydrogen flames, while ensuring safe operation. The combustion instabilities of a self-excited multi-element partially premixed hydrogen flame with varying mixing lengths are investigated by the measurements and diagnostics of acoustic pressure and OH^⁎ chemiluminescence. The distribution characteristics of the self-excited instabilities show that the mixing length exerts a significant effect on the thermoacoustic instabilities, with the widest stable region occurring at the longest mixing length. High-speed OH^⁎ chemiluminescence imaging is used to determine the flame structure and dynamics for varying mixing lengths. Low-amplitude instabilities exhibit periodic fluctuations in the heat release rate (HRR) within the flame, whereas high-amplitude instabilities are also accompanied by complex flame dynamics, including pinch-off, annihilation, and regeneration processes. Data-driven modal decomposition and phase-space HRR distributions reveal the fluctuations in the opposite direction alternating between the upper and lower regions, demonstrating that the self-excited oscillations are dominated by longitudinal modes. Denser and more frequent small-scale structures are observed at high-frequency harmonics, and their morphological transitions trigger weak transverse phase-lag patterns. The combined effects of transverse and longitudinal variations depict the self-excited hydrogen flame dynamics in convective transport. Two-dimensional Rayleigh index distribution indicates that amplitude-dependent thermoacoustic coupling occurs at the flame base. Despite the presence of harmonics in the self-excited oscillations, the thermoacoustic coupling at the dominant frequency governs the self-excited instabilities. The time-lag analysis illustrates that the convection time dominated by mixing length and the chemical reaction time have a significant effect on the self-excited instability in a multi-element partially premixed hydrogen flame.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114850"},"PeriodicalIF":6.2,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146184817","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":"Influence of ethanol and OME3 on ethylene laminar premixed flames: experimental and numerical study","authors":"Vincenzo Esposito ,&nbsp;Ferdinando Stanzione ,&nbsp;Barbara Apicella ,&nbsp;Mariano Sirignano ,&nbsp;Carmela Russo","doi":"10.1016/j.combustflame.2026.114860","DOIUrl":"10.1016/j.combustflame.2026.114860","url":null,"abstract":"<div><div>The urgent transition from fossil fuels to sustainable alternatives has intensified interest in oxygenated fuels, whose inherent oxygen content alters gas-phase chemistry and suppresses the formation of soot precursors and particulate matter (PM) in internal combustion engines. Among these, ethanol (EtOH) and oxymethylene ether-3 (OME₃) have emerged as promising candidates for lowering soot and Diesel Particulate Matter (DPM) emissions. Although oxygenated fuels are known to reduce particulate mass emissions, their impact on ultrafine particles (UFPs) and nanoparticles (NPs) – which pose significant health risks – remains ambiguous, with literature showing conflicting results. The physicochemical properties and functional groups of oxygenated compounds, beyond mere oxygen content, play a crucial role in shaping particle formation dynamics and toxicity. This study investigates ethylene (C₂H₄)/air premixed flames doped with EtOH or OME₃. These oxygenated fuels, accounting for 20% (<em>α</em>) of the total carbon fed, were introduced into the fuel stream in flames with equivalence ratios (Φ) ranging from 2.01 to 2.46, encompassing near- and highly sooting conditions. A combined experimental and numerical approach is employed to assess variations in soot and NP emissions, offering new insights into the influence of oxygenated fuel structure on combustion and particulate behavior.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114860"},"PeriodicalIF":6.2,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146184816","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":"Critical condition for spark ignition in homogeneous and stratified partially cracked ammonia","authors":"Jinzhou Li ,&nbsp;Shumeng Xie ,&nbsp;Peng Ma ,&nbsp;Samir Boset Rojas Chavez ,&nbsp;Huangwei Zhang","doi":"10.1016/j.combustflame.2026.114853","DOIUrl":"10.1016/j.combustflame.2026.114853","url":null,"abstract":"<div><div>Ignition of partially cracked ammonia (PCA) is critical for ammonia-based combustion systems, yet the roles of cracking ratio and cracking-ratio stratification in governing ignition behavior remain insufficiently understood. In this study, one-dimensional numerical simulations with detailed chemical kinetics are performed to investigate the minimum ignition energy (MIE) and ignition-kernel development in both homogeneous and cracking-ratio-stratified PCA mixtures over a wide range of equivalence ratios and cracking ratios. For homogeneous mixtures, inclusion of thermal radiation significantly increases the predicted MIE near the lean and rich ignition limits, leading to improved agreement with experimental measurements. At higher cracking ratios (≥ 0.4), a consistent scaling between MIE and the cube of the minimum ignition radius is identified across different effective Lewis numbers, indicating a robust ignition scaling behavior in hydrogen-rich PCA mixtures. For stratified mixtures, a critical stratification radius is identified, beyond which further stratification no longer enhances or suppresses ignition. This critical radius increases as the cracking ratio of the lower-reactivity region decreases. In addition, pressure effects on MIE are found to be non-universal and strongly conditioned by both mixture stratification and cracking ratio. These findings provide new physical insight into PCA ignition and highlight the importance of critical ignition length scales under gas-turbine-relevant conditions.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114853"},"PeriodicalIF":6.2,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146185197","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":"Normalization reveals the role of thermodiffusive effects in turbulent premixed hydrogen–methane flames","authors":"Oussama Chaib ,&nbsp;Jinhyun Bae ,&nbsp;Lee Weller ,&nbsp;A.J. Aspden ,&nbsp;Simone Hochgreb","doi":"10.1016/j.combustflame.2026.114852","DOIUrl":"10.1016/j.combustflame.2026.114852","url":null,"abstract":"<div><div>This paper investigates the interaction between turbulence and thermodiffusive instabilities experimentally using a large Mie-scatter imaging data set of hydrogen-enriched methane–air flames (46 different conditions) at constant flow field conditions and variable blending ratios and equivalence ratios. In methane–air lean premixed flames with unity Lewis numbers, turbulence has a strong effect on the overall flame morphology and global consumption speed. Conversely, turbulence is found to have less of an effect on the overall morphology and consumption speed of lean hydrogen–methane flames at sufficiently low (sub-unity) Lewis numbers for the conditions examined herein. The results of the present work provide experimental support to the suggestion that one-dimensional laminar flame characteristics obtained from freely-propagating flame simulations are unsuitable normalization factors when comparing thermodiffusively unstable flames of variable blending and equivalence ratios. It is demonstrated how characteristic scaling laws based on the DNS-based consumption speed parameterized by an instability parameter <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mi>T</mi><mi>D</mi></mrow></msub></math></span> paint a more consistent picture of the turbulence-instability interactions in the present regimes.</div><div><strong>Novelty and Significance Statement</strong></div><div>The work herein constitutes the first application of Mie scattering for the measurement of turbulent flame characteristics (consumption speed, area, and curvature) in premixed hydrogen-enriched methane–air flames across the <em>full range of lean conditions</em>, providing one of the <em>largest</em> experimental data sets for the purpose of validation. The design of experiments involved a Karlovitz number <span><math><msub><mrow><mi>Ka</mi></mrow><mrow><mi>L</mi></mrow></msub></math></span> sweep at constant flow conditions, by varying the equivalence ratio of the flame. This approach is original and differs from traditional designs (i.e., Troiani et al. (2024)) which have so far relied on modifying flow turbulence characteristics (e.g., bulk flow or turbulent rms velocity) at fixed equivalence ratio. Moreover, this work provides the first experimental evidence in favor of using characteristic normalizations which account for thermodiffusive instabilities in hydrogen-containing flames, and its importance. This has not been evidenced in past studies investigating turbulence and thermodiffusive instability interplay given turbulence was varied at constant equivalence ratio, and thus constant laminar flame characteristics (i.e., laminar flame speed and thickness).</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114852"},"PeriodicalIF":6.2,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146184677","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":"Gliding arc plasma-assisted conversion of gas mixture from efficient porous media combustion","authors":"Huaming Dai,&nbsp;Shan Chen","doi":"10.1016/j.combustflame.2026.114849","DOIUrl":"10.1016/j.combustflame.2026.114849","url":null,"abstract":"<div><div>Non-thermal plasma (NTP) technology demonstrates considerable potential for the modulation of gas components under mild conditions. To effectively utilize the CH₄ and CO₂ in porous media combustion products, this study constructed a synergistic system integrating a porous media burner with a gliding arc discharge (GAD) plasma reactor. The effects of porous media structural parameters, fuel additives, plasma parameters, and process enhancement strategies on combustion characteristics and plasma conversion were investigated. The results reveal that the alumina pellet structures produce higher syngas concentrations in Structure II (8 mm) with 14.1% H₂ and 57.8% energy efficiency at <em>φ</em>=1.5. Conversely, the silicon carbide foam structures achieve higher flame temperatures and more complete methane conversion in Structure V (20 PPI) with 96% CH₄ conversion at <em>φ</em>=1.6. Furthermore, the input voltage significantly influences the GAD plasma conversion and the optimal CH₄ and CO₂ conversion efficiencies of 37.5% and 32.1% are obtained at 6 kV. For a larger nozzle-to-blade distance (<em>D</em> = 20 mm) and blade curvature (R200), the gas reforming is significantly enhanced. And secondary methane addition and gas recirculation proved to be effective for process intensification, gaining a final H₂ concentration of 21.7% after three cycles. The findings establish a theoretical foundation for the production of syngas from combustion gases using a synergistically coupled porous media and plasma system.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114849"},"PeriodicalIF":6.2,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146184815","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":"Shear-layer effects on the dynamics of unsteady premixed laminar counterflow flames","authors":"Jose G. Rivera Lizarralde,&nbsp;Aditya Potnis ,&nbsp;Abhishek Saha","doi":"10.1016/j.combustflame.2026.114872","DOIUrl":"10.1016/j.combustflame.2026.114872","url":null,"abstract":"<div><div>The influence of flow non-uniformity and unsteadiness on premixed flames is of considerable interest due to its relevance to practical combustion systems. The steady counterflow flame has long served as a canonical configuration for investigating flame dynamics under controlled, spatially non-uniform conditions. A commonly studied variation, referred to as the unsteady counterflow, introduces a temporal perturbation to the otherwise steady flow from the nozzles, thereby enabling the systematic examination of the coupled effects of unsteadiness and non-uniformity. Prior investigations have focused on flame dynamics along the line of symmetry, where the reduced dimensionality of the problem facilitates analysis. In the present study, we extend this perspective by experimentally examining flame behavior at off-center locations, where multi-dimensional effects of non-uniformity and unsteadiness are more pronounced. Results reveal markedly different dynamics away from the centerline, characterized by a dominant contribution from higher harmonic responses. Further analysis of the associated vortex dynamics in the shear layer demonstrates that the radial variations in the intensity of these vortical structures directly govern the variations in the strength of the observed higher harmonics, and thereby the altered flame behavior.</div><div><strong>Novelty and significance statement</strong></div><div>While the counterflow configuration is a widely used canonical model for studying flames subjected to unsteady strain rates, prior investigations have primarily focused on centerline or symmetry-plane behavior. This study expands that framework by systematically examining both centerline and off-center flame dynamics, revealing pronounced spatial variations in the spectral response. In particular, the results uncover distinct spectral signatures associated with the coupling between imposed unsteadiness and vortex shedding in off-center regions, which are not observable from centerline analyses alone. These off-center perspectives extend the relevance of counterflow studies to other canonical flame configurations, such as bluff-body-stabilized and jet flames, where flame-vortex interactions play a central role in stabilization. The explored unsteady dynamics of off-center locations are also relevant for practical combustors, where flames are often asymmetric and highly unsteady.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114872"},"PeriodicalIF":6.2,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146184841","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 fuel-staging and reburning on NOx emissions from NH3/CH4/air swirling flames","authors":"Shixing Wang ,&nbsp;Jingye Chen ,&nbsp;Ayman M. Elbaz ,&nbsp;Zhihua Wang ,&nbsp;William L. Roberts","doi":"10.1016/j.combustflame.2026.114816","DOIUrl":"10.1016/j.combustflame.2026.114816","url":null,"abstract":"<div><div>Advanced reburning (AR) is a method utilizes the fuel-staging and thermal de-NO_x to reduce the NO_x emissions in modern coal fired boilers or gas turbines. Ammonia (NH₃) is considered a promising carbon-free fuel in the context of carbon neutrality. However, the emission characteristics of NH₃ swirling flames respond strongly to the influence of reburning and fuel staging. This study investigated the NO_x and unburnt ammonia emissions of NH₃/CH₄/air mixtures in a fuel-staging swirling combustor. The ammonia mole fractions range from X_NH3 = 0.3, 0.6 to 1.0, with the overall equivalence ratios ranging from <em>ϕ</em> = 0.6 to 1.0. Secondary fuel injection ratio, η ranges from 0 to the X_NH3 until the blow-off of primary flame. Three different secondary fuel injection locations (H1/D = 1.7, H2/D = 2.5 and H3/D = 3.4 where D is diamter of burner exit) were adopted to represent different flame temperatures. The secondary fuel injection prevails with a thermal de-NO_x effect for X_NH3 = 0.3 for all <em>η</em> while at X_NH3 = 0.6, secondary fuel injection first reduces NO emissions and then increases the NO emissions <em>η</em> as increases. As the fuel injection height increases, NO reduction is more favored while N₂O emissions and unburnt ammonia gradually appears due to the lower flame temperature and shorter residence time. The comparison of fuel-staging by methane and ammonia is also conducted which shows ammonia-staging is more efficient in reducing NO emissions. NO-PLIF measurements shows a first decrease then increase trend at the highest injection location which is consistent with NO emission measurements. Chemical reactor networks (CRN) analyses indicate that increasing the residence time in the primary reaction zone and decrease the temperature in the secondary reaction zone can efficiently reduce the NO and N₂O emissions. But too low secondary reaction zone temperature can breed large amount of N₂O emission and unburnt ammonia slip. Combining fuel-staging and reburning may be a promising way to achieve very low NO_x and unburnt ammonia emissions in the future.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114816"},"PeriodicalIF":6.2,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146185136","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":"Impact of product gas composition on vibrational excitation and relaxation of N2, O2, and CO2 in pulsed microwave flame plasmas","authors":"Sarang Bidwai ,&nbsp;Fynn Reinbacher ,&nbsp;Ryan J. Thompson ,&nbsp;Chloe E. Dedic ,&nbsp;James B. Michael","doi":"10.1016/j.combustflame.2026.114856","DOIUrl":"10.1016/j.combustflame.2026.114856","url":null,"abstract":"<div><div>The impact of product gas composition on the relaxation timescales of multiple species in lean hydrogen flames excited by pulsed microwave radiation is investigated in this study. Temporally-resolved vibrational temperature measurements using hybrid fs/ps CARS of multiple species (N₂, O₂, and CO₂), along with emission spectroscopy and direct electric field measurements, are obtained in pulsed microwave flame plasmas. The pulsed microwave system consists of a resonant microwave cavity and a 30 kW magnetron capable of producing 3.05 GHz, 2 microsecond-duration microwave pulses. Quantitative electric field measurements were also conducted in situ using waveguide-mounted electric field probes. Reduced electric field strengths up to 200<!--> <!-->Td were recorded in hydrogen flames diluted with N₂, O₂, and CO₂. Long-lived electronically-excited states of N₂ impact the vibrational relaxation of <figure><img></figure> . Also, the vibrational temperatures of <figure><img></figure> and <figure><img></figure> states were found to be significantly higher than ground state temperatures during the microwave pulse. The ground state vibrational temperature of N₂ rises during the microwave pulse and reaches a maximum around 10 <span><math><mi>μ</mi></math></span>s after the microwave pulse, then decreases to a steady temperature which persists for milliseconds. The presence of CO₂ leads to faster vibrational relaxation of N₂. In flames with O₂ as the primary diluent, a secondary rise in the vibrational temperature of O₂ occurs approximately 100 microseconds after the microwave pulse, indicating relaxation dynamics in such flames are dominated by large degrees of O₂ dissociation.</div><div><strong>Novelty and significance statement</strong> This work presents the measurement of ground state vibrational thermometry of three major species (N₂, O₂, and CO₂) in microwave-enhanced hydrogen flames using hybrid fs/ps CARS, excited state thermometry conducted using emission spectroscopy, and electric field strength measurements conducted in the microwave cavity. These measurements represent a novel, multi-species characterization of vibrational temperature evolution following excitation. The presence of diluents is significant, leading to large discrepancies in the vibrational temperature of species (e.g. N₂ and O₂) in the same mixture which persists for milliseconds, which is attributed to O atom recombination following the microwave plasma excitation.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114856"},"PeriodicalIF":6.2,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146185195","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":"Fundamental investigation of the effects of turbulent jet velocity and reactivity in the pre-chamber on ammonia combustion","authors":"Zongkuan Liu ,&nbsp;Lijia Zhong ,&nbsp;Wanhui Zhao ,&nbsp;Haiqiao Wei ,&nbsp;Wenming Yang ,&nbsp;Gequn Shu ,&nbsp;Lei Zhou","doi":"10.1016/j.combustflame.2026.114822","DOIUrl":"10.1016/j.combustflame.2026.114822","url":null,"abstract":"<div><div>Pre-chamber (PC) turbulent jet ignition (TJI) offers an effective solution to the challenges of difficult ignition and slow flame propagation in ammonia combustion. This study delves into the ignition and combustion characteristics of ammonia/air mixture under the TJI mode. A reactivity-controlled TJI (RCTJI) mode is achieved through a self-designed PC equipped with a scavenging system, which supports three operating modes: reactivity-controlled PC, scavenged PC, and passive PC. The reactivity-controlled PC is achieved by adjusting the hydrogen and air injection amounts to regulate the PC mixture reactivity. Various PC operating modes and PC nozzle diameters (d_noz) are investigated to elucidate the underlying ignition mechanisms of ammonia/air mixture and to reveal the effects of the TJI method on extending the rich limit in the presence of turbulent heat dissipation. First, the rich limit and combustion characteristics of ammonia were analyzed under three PC operating modes. Subsequently, the rich limit of the ammonia/air mixture was investigated through adjustments of PC mixture reactivity and d_noz using the reactivity-controlled PC. The results suggest that hot jet ignition occurs under reactivity-controlled PC conditions, which is induced by the high-velocity turbulent jet produced by PC hydrogen combustion, then it leads to the intense turbulent flame and the improved burning rate in the main chamber (MC). Conversely, a reduction in turbulent jet velocity, caused either by a low-reactivity PC mixture or an increased d_noz, leads to the hot jet ignition switch to flame ignition, and different combustion modes, including the outward, forward, backward, and head-on collision propagating flames, are observed. The rich limit of ammonia combustion is influenced simultaneously by d_noz, PC mixture reactivity, and MC mixture concentration. By optimizing both d_noz and PC mixture reactivity to achieve an appropriate balance of reduced turbulent jet velocity and enhanced jet intensity, the rich limit of ammonia combustion can be extended to Φ =1.8.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114822"},"PeriodicalIF":6.2,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146184671","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}