Combustion and Flame最新文献

{"title":"Turbulent spray combustion modeling in reduced tabulation parameter space by similarity mapping","authors":"Qun Hu,&nbsp;Lipo Wang","doi":"10.1016/j.combustflame.2024.113749","DOIUrl":"10.1016/j.combustflame.2024.113749","url":null,"abstract":"<div><div>To overcome the modeling challenge from the coupling between liquid vaporization and chemical reaction in turbulent spray combustion, a similarity mapping approach is implemented to reduce the flamelet tabulation parameters. In the framework of Eulerian–Lagrangian multiphase large eddy simulations (LES), such a modeling idea is developed upon the conventional flamelet/progress variable model. The flamelet library is constructed from a series of quasi one-dimensional spray counterflow solutions, integrated with the multiple solution modes. Test cases, including the laminar spray counterflow flame and Sydney turbulent spray flame, indicate that this newly proposed model is in principle favorable to improve the numerical predictability with acceptable computational cost. Overall, the flame structure can be appropriately captured, showing better performance compared with some reported results.</div></div><div><h3>Novelty and significance statement</h3><div>A newly proposed similarity mapping spray flamelet/progress variable (SMFPV) model is implemented for turbulent spray combustion. In SMFPV, the number of entry parameters of the flamelet library is reasonably reduced and two-way coupling between flame and evaporation can be realized. Thus in principle, SMFPV is favorable to improve the numerical predictability with acceptable computational cost. Simulation results of test cases justify the modeling idea.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113749"},"PeriodicalIF":5.8,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142358703","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 of the NO formation characteristics and ammonia-N/coal-N transformation mechanism of ammonia-coal co-combustion in O2/CO2 atmosphere","authors":"Ping Chen ,&nbsp;Huichun Wang ,&nbsp;Longxiang Qiao ,&nbsp;Mingyan Gu ,&nbsp;Kun Luo ,&nbsp;Jianren Fan","doi":"10.1016/j.combustflame.2024.113756","DOIUrl":"10.1016/j.combustflame.2024.113756","url":null,"abstract":"<div><div>Exploring the characteristics of NO formation during ammonia-coal co-combustion is crucial for achieving clean combustion. O₂/CO₂ atmosphere is an effective way to achieve low nitrogen combustion of pulverized coal, but the effect of O₂/CO₂ atmosphere on NO formation characteristics of ammonia-coal co-firing is still unclear. This work used high-temperature furnace experiments to investigate the conversion characteristics of fuel-N in ammonia-coal co-combustion under CO₂ atmosphere and conducted quantum chemistry calculations to investigate the molecular pathways of fuel-N oxidation. The experimental results showed that the higher temperature and oxygen concentration results in earlier occurrence of the peak and completion of NO in ammonia-coal co-combustion. Compared to N₂ atmosphere, CO₂ has an inhibitory effect on NO generation in ammonia-coal co-firing and the degree of CO₂ inhibition on the formation of NO per unit mass gradually decreases with increasing the temperature. The theoretical calculation results showed that CO₂ reduces the energy barrier of the rate determining step for ammonia-N oxidation by about 133.81 kJ/mol, promoting the conversion of ammonia-N to nitrogen oxides. However, CO₂ also has a certain degree of inhibitory effect on the coal-N oxidation, increasing the energy barrier of the rate determining step for NO generation from coal-N oxidation. The kinetic results showed that when the temperature is higher than 1673 K, CO₂ has a more obvious promotion effect on ammonia-N oxidation and inhibition effect on coal-N oxidation, but a more significant inhibitory effect on coal-N oxidation, so that the CO₂ atmosphere can inhibit the generation of nitrogen-containing products in ammonia-coal co-combustion to a certain extent.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113756"},"PeriodicalIF":5.8,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142358701","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":"Oxidation of butane-2,3-dione at high pressure: Implications for ketene chemistry","authors":"Xiaoyuan Zhang ,&nbsp;Maxence Lailliau ,&nbsp;Yuyang Li ,&nbsp;Yumeng Zhu ,&nbsp;Zehua Feng ,&nbsp;Wei Li ,&nbsp;Philippe Dagaut","doi":"10.1016/j.combustflame.2024.113753","DOIUrl":"10.1016/j.combustflame.2024.113753","url":null,"abstract":"<div><div>Ketene (CH₂CO) mechanism is a building block for developing combustion kinetic models of practical fuels. To revisit the combustion chemistry related to ketene, oxidation experiments of butane-2,3‑dione (diacetyl, CH₃COCOCH₃), considered as an effective precursor of CH₂CO, are conducted in a jet-stirred reactor (JSR) at 10 bar and temperatures ranging from 650 to 1160 K. Identification and quantification of intermediates are achieved by Fourier transform infrared spectrometry, gas chromatography, and mass spectrometry. A kinetic model of diacetyl is constructed based on recent theoretical and modeling studies on diacetyl and ketene, which has been validated against the present data and experimental data of diacetyl and CH₂CO in literature. Generally, the present model can adequately predict most of them, and better predict the methyl-related intermediates under wide pyrolysis and combustion conditions than previous models. Based on modeling analyses, the unimolecular decomposition reaction of diacetyl is the dominant reaction pathway for fuel consumption under different equivalence ratio conditions, especially at high temperatures. Under lean conditions, both the H-atom abstraction reactions by methyl (i.e. CH₃COCOCH₃ + CH₃ = CH₄ + CH₂CO + CH₃CO, R3) and by OH (i.e. CH₃COCOCH₃ + OH = H₂O + CH₂CO + CH₃CO, R5) are important for diacetyl consumption, while under rich conditions R5 becomes negligible. As the most important intermediates in diacetyl oxidation, the main consumption pathways of CH₂CO and CH₃ are dependent on the equivalence ratio conditions. Under lean conditions, CH₂CO mainly reacts with OH to produce CH₂OH and CO (i.e. CH₂CO + OH = CH₂OH + CO, R10), while methyl reacts with HO₂ to produce CH₃O and OH (i.e. CH₃ + HO₂ = CH₃O + OH, R20). In contrast, under rich conditions, the addition-elimination reaction between CH₂CO and H becomes competitive with R10, while the CH₃ self-combination producing C₂H₆ plays a more important role than the CH₃ oxidation pathway R20. Sensitivity analysis of CH₂CO shows that not only the reactions of CH₂CO, but also those of CH₃ are sensitive to CH₂CO formation. This is because CH₃ related reactions influence the distribution of radical pool, which determines the oxidation reactivity of the reaction system.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113753"},"PeriodicalIF":5.8,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142327801","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 lean methane flame response to NRP discharges actuation","authors":"N. Barléon ,&nbsp;D.A. Lacoste ,&nbsp;A.M. Alkhalifa ,&nbsp;O. Vermorel ,&nbsp;B. Cuenot","doi":"10.1016/j.combustflame.2024.113745","DOIUrl":"10.1016/j.combustflame.2024.113745","url":null,"abstract":"<div><div>This study investigates the response of a laminar methane-air flame to Nanosecond Repetitively Pulsed (NRP) discharges in a canonical wall-stabilized burner using a combined experimental and numerical approach. The flow and flame behaviors were modeled using Direct Numerical Simulation (DNS) with an Analytically Reduced Chemistry for a precise chemical description. A phenomenological model incorporating detailed plasma kinetics and experimental observations was developed to simulate plasma effects. Zero-dimensional plasma reactor simulations were used to build up a reduced-order model describing discharge energy distribution in the specific conditions studied. Experimental measurements of electrical profiles identified two discharge regimes: a low-energy Corona discharge and a higher-energy Glow discharge, characterized by distinct spatial energy distributions. Experimental flame response analysis revealed three major phases: marginal response up to 100 pulses, a downstream shift of the flame tip, and stabilization after 400 pulses. Numerical simulations indicated that the Corona regime is crucial for explaining initial flame responses, while the Glow regime influences later stages. Adjustments in the Vibrational–Translational (VT) energy relaxation time and energy deposition ratios between fresh and burnt gases were necessary to match experimental observations. Additionally, an accurate modeling of the transient and steady-state flame responses requires integrating both the specificity of the Corona and the Glow discharge regimes. Future work should focus on measuring or theoretically calculating N₂(v) relaxation times in CH₄-H₂O-CO₂ mixtures and analyzing the spatial energy distribution of discharges interacting with flames to enhance plasma-combustion coupled models.</div><div><strong>Novelty and significance</strong></div><div>In this work, a phenomenological plasma-assisted combustion model has been developed, to investigate a laminar premixed stagnation plate burner, focusing on VT energy relaxation time and spatio-temporal energy distribution modeling. For the first time, not only O₂, N₂ and O but also the fuel and combustion intermediates and products have been considered in the VT relaxation model. It revealed their strong influence on the overall flame response in a case where the discharge crosses a flame front, highlighting the strong beneficial effect of energy deposited in vibrational form. The study questions and investigates the energy distribution from fresh to burnt gases, challenging the conventional uniform energy distribution assumption. The experimental identification of two specific plasma regimes was necessary to predict the transient flame response. Additionally, energy deposited downstream of the flame, in fresh gases, was found to more efficient than in hot gases to enhance combustion.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113745"},"PeriodicalIF":5.8,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142327735","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 study on the pretreatment of ammonia by nanosecond pulsed discharge for combustion enhancement: Effects of pretreatment uniformity","authors":"Juntao Ao,&nbsp;Chengdong Kong,&nbsp;Yu Wang,&nbsp;Xiaojiang Wu,&nbsp;Zhongxiao Zhang","doi":"10.1016/j.combustflame.2024.113752","DOIUrl":"10.1016/j.combustflame.2024.113752","url":null,"abstract":"<div><div>The nanosecond (NS) pulsed discharge for ammonia combustion assistance is numerically investigated with a special focus on the effects of discharge pretreatment uniformity. A method to mimic spatially non-uniform discharge pretreatment is established. Using NH₃/O₂/He and NH₃/O₂/N₂ mixtures as examples, the ignition delay time (IDT), the laminar burning velocity (LBV), and the extinction strain rate (ESR) of mixtures pretreated by different discharge pretreatment methods were analyzed under a wide range of pretreatment uniformity. The results indicate that for the premixed NH₃/O₂/He (or N₂) pretreated by NS discharge pulses, with the increase of the pretreatment non-uniformity, the IDT initially increases slightly, reaching a maximum and then decreases rapidly by 80 %, while the LBV and the ESR first decreases slowly, reaching a minimum and then increases rapidly by 10 %. The initial increment of IDT with the non-uniformity can be attributed to the deterioration of discharge-induced chemical effect but the rapid decrease of IDT as the discharge pretreatment becomes highly non-uniform is largely determined by the combustion-related chemical effect. The effects of pretreatment uniformity on LBV and ESR can be largely due to the thermal effect. When the oxidant is pretreated by the NS discharge, the minimal IDT, the maximal LBV and ESR can be observed under uniform conditions owing to the chemical effects and thus a uniform discharge pretreatment is preferred. Furthermore, a comparative analysis of the three pretreatment methods under identical energy input reveals that under uniform pretreatment, the direct pretreatment of pure NH₃ is optimal, since it can generate more H₂ to enhance the combustion. However, under highly non-uniform conditions, the discharge pretreatment of premixed fuel/oxidant mixtures is the most efficient for combustion enhancement.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113752"},"PeriodicalIF":5.8,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142358700","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":"Ignition and combustion characteristics of boron particles under reduced pressure","authors":"Ying Feng ,&nbsp;Yong Tang ,&nbsp;Dingjiang Xie ,&nbsp;Wei Dong ,&nbsp;Majie Zhao ,&nbsp;Zhiwen Wu ,&nbsp;Baolu Shi","doi":"10.1016/j.combustflame.2024.113733","DOIUrl":"10.1016/j.combustflame.2024.113733","url":null,"abstract":"<div><div>The ignition and combustion processes of boron particles are crucial to achieving high combustion efficiency in solid-fuel ramjet engines, particularly under reduced static pressure conditions in the secondary combustion chamber. This study carried out ignition and combustion experiments on amorphous boron particles with an average size of ∼3 µm, using a Hencken multi-diffusion flat flame burner under controlled pressures (0.3–1 atm) and temperatures (1900–2200 K). Optical measurements were utilized to qualify the ignition time, which increases with decreasing pressure. Then, the ignition and combustion models of small-size boron particles under reduced pressure were established, for which the Langmuir layer was introduced to calculate heat and mass transfer between particles and surrounding gases in the transition regime. Results showed that the Langmuir layer significantly lowered heat transfer rate, increasing the ignition time. A comparison of the heat fluxes of evaporation, heterogeneous reaction, and heat convection for the ∼3 µm boron particle demonstrated that the ignition process was limited by heat convection, while the combustion process is dominated by the heterogeneous reaction near the particle surface.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113733"},"PeriodicalIF":5.8,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142358698","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":"Mach reflection of detonation waves with velocity deficits","authors":"Zhen-Yang Zhou ,&nbsp;Hong-Hao Ma ,&nbsp;Lu-Qing Wang","doi":"10.1016/j.combustflame.2024.113754","DOIUrl":"10.1016/j.combustflame.2024.113754","url":null,"abstract":"<div><div>Velocity deficits, which exist universally in the process of detonation propagation, were not considered in the problem of detonation Mach reflection in previous studies. Thus, an experimental study of the Mach reflections of gaseous detonations with velocity deficits is reported in this paper. Remarkable velocity deficits were achieved by a porous wall channel. The soot foil technique was utilized to monitor the cellular pattern variation and the evolution of triple-point trajectory. Two detonable mixtures, i.e., 2H₂+O₂+3Ar and 2H₂+O₂, were used to obtain stable detonation and unstable detonation. The results show that along with velocity deficits, the detonation tends to be unstable and the cell size increases. The induction length must be taken into consideration since the specific heat ratio could be different from that of a Chapman-Jouguet (CJ) detonation. Therefore, three modes of self-similarity were determined, i.e., non-self-similarity with significant velocity deficits (<em>mode 1</em>), global self-similarity with moderate velocity deficits (<em>mode 2)</em> and localized self-similarity with slight velocity deficits (<em>mode 3</em>). The Mach stem height of <em>mode 1</em> is higher than the non-reactive three-shock theory. The triple-point trajectory of <em>mode 2</em> corresponds to that of an inert shock. In the case of <em>mode 3</em>, the well-known frozen and equilibrium limits in detonation Mach reflections can be found. Considering the measured cell size (<span><math><mi>λ</mi></math></span>) as the length scale, the required transition distance for the occurrence of the equilibrium limit was found to be approximately (8–10)<span><math><mi>λ</mi></math></span>. A threshold value <span><math><msub><mi>α</mi><mi>i</mi></msub></math></span>=0.95 was found above which the Mach reflection characteristics of a detonation agree well with those of a CJ detonation (<span><math><msub><mi>α</mi><mi>i</mi></msub></math></span> is the overdrive degree of the incident wave). Below the threshold value, the triple-point trajectory angle decreases linearly with the increase of <span><math><msub><mi>α</mi><mi>i</mi></msub></math></span>, and the Mach stem overdrive degree is a constant.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113754"},"PeriodicalIF":5.8,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142358699","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":"Spray combustion characteristics of boron slurry fuel in high particle loading conditions","authors":"P. Prabhudeva,&nbsp;Srinibas Karmakar","doi":"10.1016/j.combustflame.2024.113739","DOIUrl":"10.1016/j.combustflame.2024.113739","url":null,"abstract":"<div><div>Enhancing the energy density of hydrocarbon fuels is indeed crucial, especially in the context of addressing energy needs. Incorporating energetic particles as additives into conventional liquid fuels garners increased attention due to its potential to enhance energy density. Due to its high energy potential, boron is the most promising additive in several energetic particles. However, the study focusing on the boron-loaded slurry fuels are limited. Therefore, the present work focuses on the effect of boron loading on the spray combustion of boron-loaded slurry fuel, especially at higher loadings (10%, 20% &amp; 30% boron + Jet A-1 fuel) using a swirl-stabilized spray combustor. The research scrutinizes the feed and exhaust particles' surface morphology, chemical composition and active boron content through diverse particle characterization techniques. Furthermore, the study investigates the influence of boron loading on the combustion characteristics of slurry fuel using methods such as colour flame imaging, spectroscopy, and BO₂* Chemiluminescence imaging. The impact of boron loading on the positive thermal contribution of the slurry was examined by analyzing temperature measurements at various locations within the combustor. The BO₂* chemiluminescence imaging and spectroscopy results indicate that the intensity of BO₂ emission increases with a rise in particle loading. The temperature results reveal an increase in temperature compared to pure Jet A-1 for all the boron-loaded cases. In particular, JB10 and JB20 achieved nearly 90% and 85% of the theoretical temperature increase. The diffractogram and thermogravimetric results of the burnt particles collected show that the particles were burnt thoroughly for the boron-loaded cases.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113739"},"PeriodicalIF":5.8,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142327800","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":"Analysis of the nanostructure evolution of soot in n-heptane/iso-octane with 2,5-dimethylfuran addition: A combined experimental study and ReaxFF MD simulations","authors":"Wenlong Dong,&nbsp;Run Hong,&nbsp;Yuhang Yang,&nbsp;Dongyang Wang,&nbsp;Bingbing Qiu,&nbsp;Huaqiang Chu","doi":"10.1016/j.combustflame.2024.113751","DOIUrl":"10.1016/j.combustflame.2024.113751","url":null,"abstract":"<div><div>The soot formation of <em>n-</em>heptane/iso-octane doped 2,5-dimethylfuran (DMF) with different ratios was experimentally investigated through laminar diffusion flame and numerically simulated by using the pyrolysis simulations method of reactive force field molecular dynamics (ReaxFF MD). The results showed that the laminar diffusion flame height of <em>n-</em>heptane/iso-octane increased with increasing DMF doping ratio. At a consistent sampling height, the primary soot particle sampling numbers collected were first decreasing and then increasing, and the size of the primary soot particle was first increasing and then decreasing accompanied by the DMF doping ratio increasing. Furthermore, the transmission electron microscope (TEM) analysis provided that DMF initially inhibited and subsequently promoted the primary soot particle growth in the <em>n-</em>heptane/iso-octane flame. The core-shell ratio increased and then decreased with the increase of the DMF doping ratio, which indicated that the maturity of soot decreased and then increased. In <em>n-</em>heptane/iso-octane doped with DMF ReaxFF MD pyrolysis simulation, it was divided into three stages 0–0.5 ns (the first stage), 0.5–3 ns (the second stage), and 3–4.5 ns (the third stage). Fuel decomposed in the first stage and reacted violently in the second stage. The soot precursors continued to react, molecule size kept to increase, and the polycyclic aromatic hydrocarbons (PAHs) continued to grow. In the third stage, the carbon number of the largest molecules were slowly increasing, and the development of soot entered mature stage, where the H/C ratio was slowly decreasing. Through ReaxFF MD simulations, it was found that the maturity of soot exhibited decreasing and then increasing trend with the increase of DMF doping ratio. The graphene-like structures were mainly concentrated around the H/C ratio of 0.297 region.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113751"},"PeriodicalIF":5.8,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142322577","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 phenomenological understanding of the multimodal low-frequency oscillating combustion of ammonia induced by filamentary plasma discharge","authors":"Yu Wang,&nbsp;Chengdong Kong,&nbsp;Juntao Ao,&nbsp;Hongshen Li,&nbsp;Chengyi Wang,&nbsp;Xiaojiang Wu,&nbsp;Zhongxiao Zhang","doi":"10.1016/j.combustflame.2024.113748","DOIUrl":"10.1016/j.combustflame.2024.113748","url":null,"abstract":"<div><div>This work finds that with the assistance of filamentary plasma discharge, the ammonia combustion becomes very complicated with multiple modes, especially including a low-frequency (&lt;2 Hz) oscillating combustion mode. This flame oscillation, which is sensitive to the discharge characteristics and the flow/fuel/boundary conditions, can be further categorized as three sub-modes denoted as Mode C1, C2 and C3. Their transitions occur depending on the flow rate (<em>Q</em>_tot), the equivalence ratio (<em>ϕ</em>) and the temperature of the chamber wall. Detailed dynamic characteristics of flame kernels and flow fields during the oscillating process are further acquired to confirm the changing recirculation zone and the Karlovitz (Ka) number. A phenomenological mechanism based on recirculated energy feedback is thus proposed to explain the oscillating flame. In addition, the <em>S</em>-curve is used to elucidate the plasma impacts on the complicated combustion characteristics, especially the oscillating combustion modes and their transitions. It is found that the folded <em>S</em>-curve can be stretched with the help of plasma discharge. By considering the energy feedback effects, the <em>S</em>-curve can become more stretched with the Da number for extinction (i.e. <span><math><mrow><mi>D</mi><msub><mi>a</mi><msup><mi>E</mi><mo>′</mo></msup></msub></mrow></math></span>) being larger than that for ignition (i.e. <span><math><mrow><mi>D</mi><msub><mi>a</mi><msup><mi>I</mi><mo>′</mo></msup></msub></mrow></math></span>). Meanwhile, the branch with the Da number between <span><math><mrow><mi>D</mi><msub><mi>a</mi><msup><mi>I</mi><mo>′</mo></msup></msub></mrow></math></span> and <span><math><mrow><mi>D</mi><msub><mi>a</mi><msup><mi>E</mi><mo>′</mo></msup></msub></mrow></math></span> is unstable and the multiple oscillating combustion modes (i.e. Mode C1-C3) can be categorized on the unstable branch of the stretched <em>S</em>-curve.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113748"},"PeriodicalIF":5.8,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142318790","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}