Proceedings of the Combustion Institute最新文献

{"title":"Insight into the inner structure of stretched premixed ammonia-air flames","authors":"Alka Karan ,&nbsp;Guillaume Dayma ,&nbsp;Christian Chauveau ,&nbsp;Fabien Halter","doi":"10.1016/j.proci.2022.07.066","DOIUrl":"https://doi.org/10.1016/j.proci.2022.07.066","url":null,"abstract":"<div><p><span>Ammonia as a fuel has sparked significant interest in the combustion community. Although, using ammonia has a lot of advantages including no carbon emissions, ammonia-air flames are characterized as thick flames with low flame speeds. It is important to understand the flame structure to know the combustion process<span> better. Flame thickness is an important property of the flame which characterizes the reactivity of the flame. Identifying the preheat zone is necessary to determine the fresh gas surface which is used to determine flame speed. Also, understanding the behavior of the important species emitted helps to demonstrate the reaction pathway which may be implemented in chemical kinetics schemes. Further, it is interesting to know the effect of curvature on the emission of excited species which gives direct knowledge on the influence of curvature on the flame reactivity. It was seen that the change in reactivity was manifested as a change in thickness of the species. The experiments presented here were performed on a Bunsen burner<span> at atmospheric conditions. The laminar flame speeds have been evaluated over a range of equivalence ratios by choosing the isotherm as specified by the definition of the flame speed which are slightly higher than the values obtained from the literature. Chemiluminescence from NH* and NH</span></span></span>₂* was studied for different equivalence ratios. A 1D simulation performed in Chemkin<em>-Pro-</em>was used to compare the behavior of the counterpart non-excited species. This comparison helps to correlate excited and non-excited species and also to define the structure of the ammonia-air flame. Both NH* and NH₂<span>* have been determined as heat release rate markers.</span></p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 2","pages":"Pages 1743-1752"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3403260","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 sudden reversal of soot formation by oxygen addition in DME flames","authors":"Francisco Cepeda ,&nbsp;Luke Di Liddo ,&nbsp;Marek Serwin ,&nbsp;Ahmet E. Karataş ,&nbsp;Seth B. Dworkin","doi":"10.1016/j.proci.2022.08.048","DOIUrl":"https://doi.org/10.1016/j.proci.2022.08.048","url":null,"abstract":"<div><p><span>Dimethyl ether (DME) is a non-toxic and renewable fuel known for its soot emissions reduction tendencies. In laminar co-flow DME </span>diffusion flames<span><span>, adding oxygen to the fuel stream increases the sooting tendency until a critical point is reached, at which point the trend suddenly reverses. This work unravels the mechanisms behind this reversal process, and characterizes their contribution to controlling soot production. A series of experimental measurements using diffuse-light line-of-sight attenuation and two-colour pyrometry were performed to measure soot volume fraction and soot temperature considering a fixed mass flow rate of DME and variable addition of oxygen. Soot volume fraction increases from 0.095 ppm in the pure DME flame to 0.32 ppm when the added oxygen concentration reaches 33%. When the oxygen concentration is slightly increased to 35%, soot volume fraction is reduced by 60%. To explain the reasons behind the reversal, a series of numerical simulations were performed, which successfully demonstrated the same trend. Results show that the chemical effects of adding oxygen to the fuel stream are exceedingly more important than the thermal and dilution effects. It was found that the reversal occurred when nearly all DME disassociated before exiting the fuel tube, indicating a sudden transition from a partially premixed DME flame, to one which primarily burns C1 fuel fragments. An analysis of soot formation and </span>oxidation rates showed that near the reversal, soot inception is the least affected process; furthermore, soot precursor availability is not significantly affected in magnitude, rather they appear further upstream. It is concluded that the favourable conditions for rapid DME decomposition into soot precursors enhances soot inception while depleting the necessary species for further soot mass growth, dramatically reducing soot concentration.</span></p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 2","pages":"Pages 1997-2005"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3403265","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 kinetic modeling studies of low- to moderate-temperature oxidation of 2-furfuryl alcohol in a jet-stirred reactor","authors":"Jinglan Wang ,&nbsp;Xuezhi Gao ,&nbsp;Weimeng Ding ,&nbsp;Pengpeng Luan ,&nbsp;Wang Li ,&nbsp;Tenglong Lv ,&nbsp;Zhanjun Cheng ,&nbsp;Lixia Wei ,&nbsp;Jiuzhong Yang ,&nbsp;Long Zhao ,&nbsp;Beibei Yan ,&nbsp;Guanyi Chen","doi":"10.1016/j.proci.2022.07.105","DOIUrl":"https://doi.org/10.1016/j.proci.2022.07.105","url":null,"abstract":"<div><p><span>2-Furfuryl alcohol, a promising platform chemical, and alternative fuels<span> or additives, is produced from the hydrogenation of furfural. However, the low- to moderate-temperature </span></span>oxidation<span><span> study of 2-furfuryl alcohol is scarce up to now. The present study first performed the oxidation experiments in a jet-stirred reactor at the equivalence ratios of 0.5, 1.0, and 2.0. The oxidation species were identified and measured by the synchrotron vacuum ultraviolet photoionization mass spectrometry. No negative-temperature-coefficient behavior was observed. A detailed </span>kinetic model<span> was developed to better understand the consumption of 2-furfuryl alcohol and the formation of oxidation products. The present model can well reproduce the experimental results. Based on the rate of production analysis, H-abstraction reactions on hydroxymethyl group forming hydroxyl(2-furyl)methyl radical are the dominant pathways. Besides, the formation and consumption of main products, such as furfural, furan, acrolein, acetaldehyde, etc., are also discussed. Fuel radicals control the formation of furfural. Furan has multiple formation sources, such as the H-addition reactions on 2-furfuryl alcohol, furfural, and 2-hydroxyfuran. Acrolein is produced by the H-addition reaction on 2-hydroxyfuran and OH-addition reactions on furan. Also, the present work compares and discusses peak concentration for major oxidation products of 2-furfuryl alcohol and 2-methyl furan under the same simulated condition. 2-Furfuryl alcohol oxidation produces a higher concentration of furfural, furan, and acrolein than that of 2-methyl furan. OH on hydroxymethyl group promotes the H-abstraction reactions on the side chain and inhibits the OH-addition reaction on the furan ring.</span></span></p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 1","pages":"Pages 455-465"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3403861","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":"Understanding the low-temperature chemistry of 1,2,4-trimethylbenzene","authors":"Shijun Dong ,&nbsp;Goutham Kukkadapu ,&nbsp;Jinhu Liang ,&nbsp;Xiaobei Cheng ,&nbsp;Scott W. Wagnon ,&nbsp;William J. Pitz ,&nbsp;Henry J. Curran","doi":"10.1016/j.proci.2022.08.106","DOIUrl":"https://doi.org/10.1016/j.proci.2022.08.106","url":null,"abstract":"<div><p><span>1,2,4-trimethylbenzene is an important representative aromatic component of gasoline/diesel/jet fuels and thus it is necessary to understand its low-temperature chemistry. In this paper, ignition delay times (IDTs) of both 1,2,4-trimethylbenzene (124TMB) and its blends with </span><em>n</em><span>-heptane were measured at engine-like conditions using both a high-pressure shock tube and a rapid compression machine for fuel in ‘air’ mixtures at pressures of 10 and 30 atm and at temperatures in the range 600 – 1100 K. The experiments in this study show for the first time that 124TMB presents a two-stage ignition behavior at engine relevant conditions. Blending </span><em>n</em>-heptane with 124TMB can significantly increase mixture reactivity at temperatures below 1000 K. A new detailed mechanism has been developed to simulate the experimentally measured IDT data. The mechanism can capture well the two-stage ignition behavior as well as the ignition delays at different pressures, equivalence ratios over a wide temperature range, for both pure fuels and their blended mixtures. Flux analyses show that the benzylic radicals (formed via H-atom abstraction from the methyl groups ortho-sites on 124TMB) can add to O₂ forming RȮ₂ radicals, which can isomerize to <span><math><mover><mi>Q</mi><mo>˙</mo></mover></math></span>OOH by intramolecular H-atom transfer from the ortho- methyl group and these <span><math><mover><mi>Q</mi><mo>˙</mo></mover></math></span>OOH radicals undergo a second addition to O₂<span><span>. This is analogous to the chain branching reaction pathways of alkanes. The chain branching reaction pathways are responsible for the first-stage heat release of 124TMB. The competitions between chain branching and both chain propagating and chain termination reaction pathways lead to a less pronounced negative temperature coefficient (NTC) behavior for 124TMB </span>oxidation, compared to two-stage ignition behavior observed for alkanes and other fuels.</span></p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 1","pages":"Pages 673-684"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3403864","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 experimental and modeling study on autoignition of 2-phenylethanol and its blends with n-heptane","authors":"Ruozhou Fang ,&nbsp;Goutham Kukkadapu ,&nbsp;Scott W. Wagnon ,&nbsp;William J. Pitz ,&nbsp;Chih-Jen Sung","doi":"10.1016/j.proci.2022.08.121","DOIUrl":"https://doi.org/10.1016/j.proci.2022.08.121","url":null,"abstract":"<div><p><span><span><span><span>2-Phenylethanol (2-PE) is an aromatic alcohol with high research octane number, high octane sensitivity, and a potential to be produced using biomass. Considering that 2-PE can be used as a fuel additive for boosting the anti-knocking quality of gasoline in spark-ignition engines and as the low reactivity fuel or fuel component in dual-fuel </span>reactivity controlled compression ignition (RCCI) engines, it is of fundamental and practical interest to understand the </span>autoignition chemistry of 2-PE, especially at low-to-intermediate temperatures (&lt;1000 K). Based upon the experimental </span>ignition delay<span> time (IDT) results of neat 2-PE obtained from our previous rapid compression machine (RCM) investigation and the literature shock tube study, a detailed chemical </span></span>kinetic model<span> of 2-PE is developed herein, covering low-to-high temperature regimes. Besides, RCM experiments using binary fuel blends of 2-PE and n-heptane (nC7) are conducted in this work to investigate the nC7/2-PE blending effects, as they represent a dual-fuel system for RCCI operations. Furthermore, the newly developed 2-PE model is merged with a well-validated nC7 kinetic model to generate the current nC7/2-PE binary blend model. Overall, the consolidated model reasonably predicts the experimental IDT data of neat 2-PE and nC7/2-PE blends, as well as captures the experimental effects of pressure, equivalence ratio, and blending ratio on autoignition. Finally, model-based chemical kinetic analyses are carried out to understand and identify the controlling chemistry accounting for the observed blending effects in RCM experiments. The analyses reveal that nC7 enhances 2-PE autoignition via providing extra ȮH radicals to the shared radical pool, while the diminished nC7 promoting effect on 2-PE autoignition with increasing temperature is due to the negative temperature coefficient characteristics of nC7.</span></p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 1","pages":"Pages 785-794"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3403866","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":"Laminar flame speed of methane/air stratified flames under elevated temperature and pressure","authors":"Takuya Tomidokoro ,&nbsp;Takeshi Yokomori ,&nbsp;Hong G. Im","doi":"10.1016/j.proci.2022.07.082","DOIUrl":"https://doi.org/10.1016/j.proci.2022.07.082","url":null,"abstract":"<div><p><span><span><span><span>Flame propagation under mixture stratification is relevant to a wide range of applications including gas turbine combustors and </span>internal combustion engines<span>. One of the local stratification effects is known as the back-support effect, where the laminar flame speed is modified when a </span></span>premixed flame<span><span> propagates into gradually richer or leaner mixtures. A majority of previous studies have focused on the propagation of methane/air stratified flames under standard temperature and pressure. However, stratified combustion often occurs under elevated temperature and pressure in practical applications, which may influence the characteristics of the back support effect through modified reaction pathways. This study performs numerical simulations of stratified laminar </span>counterflow flames under an Atmospheric Temperature and Pressure (ATP) condition and an Elevated Temperature and Pressure (ETP) condition and examines the influence of elevated temperature and pressure on the back-support effect. Reaction flow analyses were extensively conducted to elucidate the difference in the primary reaction pathway between the two conditions. When scaled by the stratification </span></span>Damköhler number, the back-support effect on the rich-to-lean stratified flame is weaker under the ETP condition than the ATP condition in the stoichiometric to lean region. This is due to increased contribution from reactions involved with OH radicals under the ETP condition, which leads to lower H</span>₂ reproduction in the reaction zone than under the ATP condition. The contribution from OH radicals is increased under the ETP condition because the conversion of H into OH is enhanced. These results suggest that the back-support effect may become negligibly small in practical combustors operating under elevated temperature and pressure due to (1) the flame being less sensitive to stratification because of the thinner flame, and (2) the lower H₂ reproduction that deteriorates the radical production that drives the back-support effect.</p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 2","pages":"Pages 1669-1677"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3457312","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":"Design and evaluation of surrogate mixtures for diesel based on the isolated droplet configuration","authors":"Álvaro Muelas,&nbsp;Diego Aranda,&nbsp;Javier Ballester","doi":"10.1016/j.proci.2022.07.099","DOIUrl":"https://doi.org/10.1016/j.proci.2022.07.099","url":null,"abstract":"<div><p>The development of simplified surrogate mixtures able to replicate combustion-related behaviors of chemically complex fuels is essential for their simulation with computational tools, a key step towards the design of high-efficiency and low-emission combustion applications. This work proposes to use the isolated droplet configuration as a benchmark to formulate and validate surrogates that capture the vaporization and soot production characteristics of a first-fill diesel and a diesel-biodiesel mixture. To that end, droplet vaporization experiments and a multicomponent model were coupled to produce blends matching the evaporation behavior, whereas the soot tendency was incorporated through tests at the ASTM <span>D1322</span><svg><path></path></svg> smoke point lamp and the Oxygen Extended Sooting Index (OESI). The so-obtained surrogate blends were subsequently validated for both characteristics. Their evaporation curves proved to match remarkably well those obtained for the target fuels, with noticeable improvements when increasing the number of compounds in the mixture. As for the sooting behavior, the proposed blends achieved a good emulation in terms of the design parameter (OESI), confirming the validity of the proposed methodology. On the other hand, an additional and independent validation of the sooting propensity through the quantification of the mass of soot produced by isolated droplets under a high-temperature and reducing atmosphere revealed significantly higher soot yields for the surrogates when compared to the target fuels. These results highlight the relevance of the configuration used when designing and validating surrogates, since the same blends can provide substantial differences when evaluated through different sooting indices.</p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 2","pages":"Pages 2483-2492"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3458037","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":"Novel insights into mild combustion processes through analyses of hysteresis behavior","authors":"Pino Sabia ,&nbsp;Maria Virginia Manna ,&nbsp;Giovanni Battista Ariemma ,&nbsp;Giancarlo Sorrentino ,&nbsp;Raffaele Ragucci ,&nbsp;Mara de Joannon","doi":"10.1016/j.proci.2022.08.011","DOIUrl":"https://doi.org/10.1016/j.proci.2022.08.011","url":null,"abstract":"<div><p>In many numerical scientific papers, MILD combustion is defined on the basis of the disappearance of extinction phenomena while varying mixture dilution levels, through the identification of the condition where ignition and extinction collapse in an unique event. Albeit with numerous contributions in elementary reactor configurations (Continuous Stirred Flow Reactors, Opposed-Diffusion flames), operating conditions to achieve this noticeable circumstance do not properly match with experimental evidences, since they lead to extreme mixture dilution levels (higher than 99% for CH₄). In addition, many works suggest the occurrence of extinctions phenomena or instabilities under MILD conditions, symptomatic of extinction/re-ignition phenomena. Simulations in an adiabatic CSTR for CH₄/O₂/N₂ mixtures, varying the N₂<span> content, were realized with the focus to analyze the system behavior through hysteresis<span>. Results show different hysteresis behaviors from “air” to diluted conditions, demonstrating the occurrence of the condition </span></span><em>T</em>_ext=<em>T</em>_ign<span><span> is not a strict constraint for MILD combustion systems<span>. In addition, the “unstable” branch has characteristic temperatures lower than the ones related to both the ignition and extinction events, enlarging the opportunity to stabilize MILD combustion processes. These results pave the way to the </span></span>reconsideration of peculiar aspects of MILD combustion processes.</span></p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 4","pages":"Pages 4501-4507"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3458627","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":"Swirling spray flames dynamical blow out induced by transverse acoustic oscillations","authors":"Clément Patat ,&nbsp;Françoise Baillot ,&nbsp;Jean-Bernard Blaisot ,&nbsp;Éric Domingues ,&nbsp;Guillaume Vignat ,&nbsp;Preethi Rajendram Soundararajan ,&nbsp;Antoine Renaud ,&nbsp;Daniel Durox ,&nbsp;Sébastien Candel","doi":"10.1016/j.proci.2022.08.029","DOIUrl":"https://doi.org/10.1016/j.proci.2022.08.029","url":null,"abstract":"<div><p>Recent experiments on a laboratory scale annular system comprising multiple injectors<span><span><span> (namely, MICCA-Spray), indicate that combustion instabilities coupled with azimuthal modes may induce large amplitude oscillations, which under certain conditions, lead to blow out of some of the flames established in the system, a phenomenon designated as dynamical blow out (DBO). An attempt is made in the present investigation to reproduce this phenomenon in a linear array of injectors (namely, TACC-Spray), where the acoustic field is externally applied to flames established by injector units that are identical to those used in the </span>annular combustor. The acoustic field is generated by driver units placed on the lateral sides of a </span>rectangular cavity. The pressure level induced in TACC-Spray can reach a peak value of 1700 Pa in a frequency range extending from 680 to 780 Hz, which corresponds to the typical frequency of azimuthal instabilities observed in the annular system. A theoretical model based on dimensional analysis serves to guide the choice of operating conditions that may lead to the DBO phenomenon. Experiments carried out in TACC-Spray and MICCA-Spray are then used to determine the DBO boundary, define the conditions that need to be fulfilled to observe this phenomenon, and gather high-speed visualizations providing some insights on the mechanisms that induce blow out.</span></p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 4","pages":"Pages 4651-4659"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3458632","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":"Attenuation of combustion instability in a fuel-staged dual-nozzle gas turbine combustor with asymmetric hydrogen composition","authors":"Sanghyeok Kwak ,&nbsp;Jaehong Choi ,&nbsp;Min Chul Lee ,&nbsp;Youngbin Yoon","doi":"10.1016/j.proci.2022.08.039","DOIUrl":"https://doi.org/10.1016/j.proci.2022.08.039","url":null,"abstract":"<div><p>The instability attenuation mechanism of fuel staging was investigated in a CH₄/H₂<span><span><span> fueled dual-nozzle gas turbine combustor. Fuel staging was implemented using an asymmetry in fuel composition between the two nozzles. The fuel composition of the upper nozzle was varied while keeping that of the lower nozzle constant. Under these conditions, the self-excited and forced responses of fuel-staged flames were analyzed using OH* </span>chemiluminescence imaging, OH planar laser-induced fluorescence, and </span>particle image velocimetry<span>. In the self-excited measurements, although strong combustion instability was exhibited in the symmetric condition<span>, it weakened gradually with increasing asymmetry in fuel composition. The symmetric flame exhibited significant fluctuations in the heat release rate around the flame tip, which acted as the primary cause of driving combustion instability. However, in asymmetric flames, the H</span></span></span>₂<span><span> addition induced phase leads in heat release rate fluctuations at the upper region, which damped combustion instability. Thus, our observations revealed a high correlation between the phase leads and the attenuation of combustion instability. Analyses of the forced responses showed that the heat release rate fluctuations were induced by interactions between the flame and the shedding vortex released from the </span>nozzle tip into the downstream. Although these characteristics of shedding vortices did not depend on the H</span>₂ addition, the change in the axial position of the flame caused by the H₂<span> addition induced the relocation of the site, at which the flame interacted with the vortex. Subsequently, it induced phase leads in the heat release rate fluctuations. The phase difference of heat release rate fluctuations between the two flames due to this phase leads enlarged progressively with increasing asymmetry in fuel composition, leading to the attenuation of combustion instability in asymmetric conditions.</span></p></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"39 4","pages":"Pages 4681-4690"},"PeriodicalIF":3.4,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3459245","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}