Combustion and Flame最新文献

{"title":"High-temperature ignition of ammonia/methyl isopropyl ketone: A shock tube experiment and a kinetic model","authors":"Weihao Zeng ,&nbsp;Chun Zou ,&nbsp;Tianci Yan ,&nbsp;Qianjin Lin ,&nbsp;Lingfeng Dai ,&nbsp;Jiacheng Liu ,&nbsp;Yu Song","doi":"10.1016/j.combustflame.2025.114004","DOIUrl":"10.1016/j.combustflame.2025.114004","url":null,"abstract":"<div><div>The ignition delay times (IDTs) of NH₃/methyl isopropyl ketone (MIPK) mixtures with MIPK blending ratios of 5 %, 10 %, and 30 % were measured at pressures of 1.75 and 10 bar, temperatures ranging from 1100 to 2000 K, under stoichiometric condition. The IDTs were found to exhibit a sharp decrease at 5 % MIPK blending ratio and then reduced slowly with further MIPK addition. Increasing pressure could enhance the ignition-promoting effects of MIPK. A detailed MIPK-NH₃ model was constructed including the MIPK sub-model, the NH₃ sub-model, and the cross-reactions between C-containing species and N-containing species which consisted of the prompt NO formation reactions and reburn type reactions, the recombination and oxidation reactions of small amines, H-abstraction reactions, and disproportionation reactions. The predictions calculated by the MIPK-NH₃ model are in good agreement with the measured IDTs. The analysis showed that the cross-reactions evidently inhibit the ignition of NH₃/MIPK, which is mainly attributed to the disproportionation reactions; and the ignition-inhibiting effects decrease with the increasing pressure or MIPK blending ratio. The effects of the MIPK blending ratio and cross-reactions on the ignition of NH₃/MIPK were analyzed in detail. The oxidation pathways of NH₃/MIPK were also discussed.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114004"},"PeriodicalIF":5.8,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143746579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study on the in-flame electron transport behaviors towards early-stage engine knocking detection","authors":"Guangyu Dong ,&nbsp;Yanxiong Zhou ,&nbsp;Zhijun Wu ,&nbsp;Robert Dibble ,&nbsp;Liguang Li ,&nbsp;Ze Wang","doi":"10.1016/j.combustflame.2025.114140","DOIUrl":"10.1016/j.combustflame.2025.114140","url":null,"abstract":"<div><div>In future high-efficiency engines that implement high compression ratios, the occurrence of knock/super knock phenomena, primarily triggered by the end gas auto-ignition (EGAI), will pose a significant challenge. To address this issue, ion sensing technology has emerged as a highly promising approach for real-time detection of knock events. However, the reliability of ion sensing based EGAI detection is still poor due to the electron ambipolar diffusion process. When EGAI occurs at the far end of the engine combustion chamber, the electrons produced in the EGAI zone are bound to positive ions due to electrostatic force. In such case, the electrons can hardly diffuse out of the zone and be collected by the anode of spark plugs (which functioned as the ion probes in production engines), consequently leading to the fault of ion sensing method. To overcome this challenge, the behaviors of electron transport under various external electric field configurations are analyzed by simulating the end gas ignition process in a constant volume combustion chamber (CVCC). The findings demonstrate that an external electric field can surmount the electrostatic force acting on electrons and positive ions. Specifically, when the voltage applied from the DC power source in the ion sensing circuit exceeds 10 kV, numerical analysis suggests a transition from electron ambipolar diffusion to unipolar diffusion. Consequently, electrons can successfully diffuse out of the EGAI zone in the CVCC. This enables the collection of ion current signals by an ion probe positioned outside of that zone. Thus, the potential of early-stage engine knocking detection based on ion sensing is highlighted, particularly since high voltages can be configured by incorporating engine ignition modules into the ion sensing systems.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114140"},"PeriodicalIF":5.8,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143746577","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":"Examination of differential diffusion effects in spatially-developing supersonic mixing layer hydrogen flames","authors":"Jieli Wei ,&nbsp;Xu Zhu ,&nbsp;Nana Wang","doi":"10.1016/j.combustflame.2025.114138","DOIUrl":"10.1016/j.combustflame.2025.114138","url":null,"abstract":"<div><div>Differential diffusion (DD) plays a crucial role in the fundamental understanding of combustion process, particular in the context of hydrogen or hydrogen-blended fuel flames. This paper intends to address whether the impact of DD on the flame stabilization in the turbulence-dominant supersonic flow can be negligible and if not, to elucidate its mechanisms. To this end, a spatially-developing supersonic non-premixed mixing layer hydrogen flame is simulated by large eddy simulations. Three distinct flow-chemistry interaction patterns: <em>laminar flow-chemistry, transition-chemistry</em>, and <em>turbulence-chemistry</em> are well designed within the mixing layer to examine the dependence of the DD effect on turbulence and its implications for flame stabilization. Results show that the importance of DD in flame-base zones of <em>transition-chemistry</em> and <em>turbulence-chemistry</em> interaction patterns is more pronounced than in <em>laminar flow-chemistry</em> one, even though their turbulence effects are more significant. The DD effect is observed to shorten the flame lift-off length and shift the leading point dynamic from a low-frequency to a high-frequency mode. Further “budget analysis” of transport- and chemistry- effect of DD shows that although the transport contribution of DD diminishes in turbulence-dominant flow-chemistry interaction patterns, the chemistry contribution of DD, i.e., sensitivity of the ignition delay time (IDT) to DD, is increased due to the low mixture temperature. Specifically, even a minor increase in the concentration of certain radicals, such as H, caused by DD can result in a significant reduction in IDT. This is primarily responsible for DD shortening the flame lift-off length within <em>transition-chemistry</em> and <em>turbulence-chemistry</em> interaction patterns. In <em>laminar flow-chemistry</em> pattern, DD facilitates the reaction to withstand high strain rates and in turn reducing the flame lift-off length.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114138"},"PeriodicalIF":5.8,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143739690","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":"Theoretical study of the real-fluid laminar flame propagation under supercritical conditions by using the virial equation of state and the Enskog transport model","authors":"Junfeng Bai,&nbsp;Xin Zhang,&nbsp;Hao Zhao","doi":"10.1016/j.combustflame.2025.114144","DOIUrl":"10.1016/j.combustflame.2025.114144","url":null,"abstract":"<div><div>A real-fluid computation model using the Virial equation of state and the Enskog transport model was developed in this work to simulate real-fluid laminar flame propagations, and it was also compared with the Redlich-Kwong-Ely-Hanley/Takahashi real-fluid model in literature. The real-fluid effects of equation of state, thermodynamics, chemical potential, thermal conductivity, and mass diffusion have been investigated on the freely propagating flame simulations of different fuels. The contribution and the source of uncertainties by different real-fluid properties are also comprehensively discussed. The overall effects of real-fluid behaviors on the laminar flame speed simulations in H₂O-dilute mixtures can reach 35 % at 100 atm, which reveal that accurate descriptions of real-fluid effects are crucial for flame speed predictions, especially using dilute gas with a high polarization, such as H₂O. The Redlich-Kwong-Ely-Hanley/Takahashi model shows severe over-predictions of the hydrogen laminar flame speeds due to its significant weakness in predictions of thermal conductivities of mixtures by comparing with the NIST data, while the present Virial-Enskog model exhibits more reasonable predictability. The real-fluid simulations of the laminar flame speeds of DME and n-heptane flames by using the Virial-Enskog model and the Redlich-Kwong-Ely-Hanley/Takahashi model are compared with the available experimental data. It shows a crucial real-fluid effect on the simulations of DME and n-heptane flame speeds, up to 8 % discrepancy from the ideal-gas flame speed prediction, even at 20–25 atm. Overall, the Virial-Enskog model provides better estimations of the real-fluid behaviors than the empirical Redlich-Kwong-Ely-Hanley/Takahashi model, especially at high pressures.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114144"},"PeriodicalIF":5.8,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143746576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental and modeling study on the high-temperature ignition of ammonia/diethyl ketone","authors":"Tianci Yan,&nbsp;Chun Zou,&nbsp;Qianjin Lin,&nbsp;Yi Yuan,&nbsp;Lingfeng Dai,&nbsp;Jiacheng Liu","doi":"10.1016/j.combustflame.2025.114069","DOIUrl":"10.1016/j.combustflame.2025.114069","url":null,"abstract":"<div><div>The ignition delay times (IDTs) of NH₃/diethyl ketone (DEK) mixtures at DEK blending ratios (<em>X</em>_DEK) of 0.05, 0.1, and 0.5 were measured in a shock tube at equivalence ratios (φ) of 0.5, 1.0 and 2.0, pressures of 1.75 and 10 bar, and temperatures from 1200 to 1900 K. The addition of DEK with <em>X</em>_DEK = 0.05 significantly improves the combustion performance of ammonia. A detailed DEK-NH₃ model was proposed including the NH₃ sub-model, the DEK sub-model, and the cross-reactions between hydrocarbon/oxygenated species and nitrogen-containing species. The model well predicts the IDTs of NH₃/DEK mixtures measured in this study, and the IDTs of pure NH₃ reported in the literature. The cross-reactions consist of the prompt NO and reburn reactions (reaction-class 1), the recombination reactions and the oxidation reactions of small amines (reaction-class 2), the H-atom abstraction reactions (reaction-class 3), and the disproportionation reactions (reaction-class 4). The comparison of the model predictions shows that the reaction-class 1 and 2 have negligible effects on the ignition. The reaction-class 3 slightly promotes the ignition and the reaction-class 4 significantly inhibits the ignition. The dependence of the effects of the cross-reactions on the blending ratio and pressure are discussed in detail. The NH₃/DEK oxidation pathway is also analyzed.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114069"},"PeriodicalIF":5.8,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143746578","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 methanol flash boiling combustion under direct injection conditions","authors":"Mingli Cui ,&nbsp;Mohamed Nour ,&nbsp;Jinhong Fu ,&nbsp;Weixuan Zhang ,&nbsp;Guodong Wang ,&nbsp;Hongchang Xu ,&nbsp;Bowei Yao ,&nbsp;Xuesong Li","doi":"10.1016/j.combustflame.2025.114147","DOIUrl":"10.1016/j.combustflame.2025.114147","url":null,"abstract":"<div><div>The task of reducing carbon emissions has become a primary goal for energy utilization purposes via combustion. The use of e-fuels/alternative fuels is a viable solution to enable zero carbon emission during the life cycle. However, the combustion of such fuels, such as methanol, is somehow different from combusting gasoline or diesel in the aspects of fuel atomization/evaporation and combustion mechanisms, etc. Flash boiling atomization is a promising atomization approach for improving the atomization and evaporation of alcohol fuels. The use of flash boiling atomization has been validated in optical gasoline direct injection (GDI) engines. However, the fundamental understanding of the impact of flash boiling on fuel combustion is still missing. This investigation focuses on the combustion of methanol fuel in a constant volume combustion chamber in a GDI fuel-air mixing fashion. The spray and flame propagation characteristics are obtained via high-speed imaging. Furthermore, detailed combustion product analysis is carried out using an online Fourier transform infrared (FTIR) device to distinguish the fundamental difference when combusting the fuel under sub-cooled and flash boiling conditions. Soot produced during the combustion is collected by mesh grids and analyzed via a transmission electron microscope (TEM). The results show that flash boiling promotes combustion efficiency under rich combustion conditions. Compared to sub-cooled combustion, methanol flash boiling combustion increases CO/CO2 emissions by 11.8 % and aldehydes emissions by 19.3 %, while reducing unburned hydrocarbons by approximately 30 %. NOx and aromatics emissions are decreased under methanol flash boiling combustion by 49.7 % and 55.1 %, respectively. Compared to n-heptane, methanol sub-cooled combustion reduces the production of soot particles. The stronger oxidation effect of methanol suppresses nuclei-mode soot generation, and the soot particles from methanol combustion feature shorter, more compact, and orderly stacked graphene layers. Moreover, flash boiling atomization further inhibits soot formation from methanol combustion.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114147"},"PeriodicalIF":5.8,"publicationDate":"2025-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143740084","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 general formalism for determining the unburnt composition in multi-stream species transport-based CFD simulations","authors":"Simone Castellani ,&nbsp;Gianmarco Lemmi ,&nbsp;Pier Carlo Nassini ,&nbsp;Roberto Meloni ,&nbsp;Antonio Andreini","doi":"10.1016/j.combustflame.2025.114128","DOIUrl":"10.1016/j.combustflame.2025.114128","url":null,"abstract":"<div><div>The imperative to decarbonise combustion necessitates technical solutions that increasingly rely on the concurrent utilisation of different fuels and/or oxidisers. The complexity of the reactive mixture compositions in such scenarios poses additional challenges from a CFD modelling perspective. While species transport models can generally describe multi-stream combustion problems directly, the definition of turbulence-chemistry interaction closures or the proper comprehension of combustion regimes often requires the reconstruction of the non-reactive mixing field. This work proposes a general comprehensive formalism for determining the unburnt composition in multi-stream combustion environments. The method relies on the elemental mass fraction conservation for the definition of a linear system that can be solved at runtime to retrieve the local unburnt mixture composition. The introduced formalism allows to assess the number of auxiliary stream-tracking scalars <span><math><mrow><mi>a</mi><mo>−</mo><mi>p</mi><mi>r</mi><mi>i</mi><mi>o</mi><mi>r</mi><mi>i</mi></mrow></math></span>, thereby minimising computational efforts and effectively enabling the use of the inherent information within the set of transported species. The study presents an application example where a dual-fuel turbulent combustion scenario is numerically investigated. In this context, the consistency of the method with respect to the use of passive scalars has been discussed with and without the species equi-diffusivity assumption. A procedure for the <span><math><mrow><mi>a</mi><mo>−</mo><mi>p</mi><mi>r</mi><mi>i</mi><mi>o</mi><mi>r</mi><mi>i</mi></mrow></math></span> estimation of the error introduced by the species preferential diffusion has been proposed, providing insights about the expected uncertainty on the predicted mixture composition and the respective flame properties.</div><div><strong>Novelty and Significance Statement</strong></div><div>The determination of the non-reactive mixing field is crucial for understanding reactive CFD simulations based on species transport. Additionally, in turbulent combustion models, knowing the unburnt composition is often a pivotal requirement for the model closure. While recalculated mixture fractions can determine the unburnt composition in dual-stream problems, this approach is inappropriate for multi-stream problems. This research introduces a novel generalised method for determining unburnt mixture composition in multi-stream combustion scenarios using CFD calculations based on species transport. The proposed method minimises the need for additional passive scalars by efficiently utilising existing information from the solved equations and boundary conditions, leveraging elemental mass fraction conservation.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114128"},"PeriodicalIF":5.8,"publicationDate":"2025-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143725034","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":"N-containing pollutant formation in pyrrole counterflow diffusion flames","authors":"Bingjie Chen ,&nbsp;Sebastian Faller ,&nbsp;Luna Pratali Maffei ,&nbsp;Andrea Nobili ,&nbsp;Matteo Pelucchi ,&nbsp;Xingcai Lu ,&nbsp;Heinz Pitsch","doi":"10.1016/j.combustflame.2025.114136","DOIUrl":"10.1016/j.combustflame.2025.114136","url":null,"abstract":"<div><div>Biomass conversion through direct combustion (energy production) or pyrolysis (bio-oil production) are novel concepts to reduce CO₂ emission in the energy sector. However, the nitrogen content in biomass feedstocks may result in elevated N-containing pollutants, e.g., NO_x, NH₃, HCN, and nitriles, yet their formation chemistry remains unclear. In this work, we studied N-containing pollutant formation in counterflow diffusion flames fuelled by pyrrole, a biomass tar surrogate component that accounts for the majority of fuel nitrogen. 27 species, including 8 N-containing species, were identified and measured in three flames with designed boundary conditions to reveal the influence of flame temperature and methane addition. Species mole fraction comparisons showed that methane addition and higher flame temperature promoted C₂–C₆ hydrocarbon formation, but mole fractions of N-containing species did not change much, reflecting less dependence on flame temperature or hydrocarbons in the species pool. An existing kinetic model for pyrrole pyrolysis and combustion was developed by updating the formation reactions of N-containing species based on recent literature studies. Numerical simulations using the kinetic model well reproduced mole fractions of most species except for NO and NO₂. Model analyses illustrated the nitrogen conversion pathways from pyrrole to individual N-containing pollutant species, and indicated the possible reactions for underestimated mole fractions of NO and NO₂. This work contributes to a better understanding of the combustion properties of N-containing fuels and N-containing pollutants in the context of biomass energy clean utilization.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114136"},"PeriodicalIF":5.8,"publicationDate":"2025-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143725033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A data-driven method to optimize soot kinetics based on uncertainty quantification and the active subspace approach","authors":"Xingyu Su ,&nbsp;Andrea Nobili ,&nbsp;Feixue Cai ,&nbsp;Alberto Cuoci ,&nbsp;Alessio Frassoldati ,&nbsp;Hua Zhou ,&nbsp;Matthew J. Cleary ,&nbsp;Zhuyin Ren ,&nbsp;Assaad R. Masri ,&nbsp;Tiziano Faravelli","doi":"10.1016/j.combustflame.2025.114137","DOIUrl":"10.1016/j.combustflame.2025.114137","url":null,"abstract":"<div><div>This paper introduces a novel approach integrating uncertainty quantification (UQ) and data-driven techniques that aim to optimize soot particle size distributions (PSDs) using an existing soot kinetic model. Leveraging the active subspace (AS) method, the influential parameters governing the overall soot production and several representative PSDs are identified. Gradient descent techniques are employed to optimize the kinetic parameters simultaneously with reference to experimental measurements of burner stabilized stagnation (BSS) flames. The optimization process is rigorously validated against experimental data and the response surface predictions, demonstrating robustness and generalization capabilities across different cases. It is found that while the soot volume fraction was adequately predicted, the iterative UQ-assisted gradient descent technique can improve the prediction of PSDs but fails to fully reproduce the experimentally observed bimodality. This confirms the need for future improvements in the sectional kinetics model. In this regard, the analysis performed points at the need of distinguishing the coagulation kinetics of liquid-like and solid primary particles. With such future improvements, whose implementation is guided by the combined UQ and data-driven approach, soot modeling may advance into a data-driven era, minimizing reliance on expert knowledge alone.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114137"},"PeriodicalIF":5.8,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143714497","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 combustion instability caused by different fuels combustion induced backpressure in a scramjet engine","authors":"Guangming Du ,&nbsp;Erda Chen ,&nbsp;Changchun Yan ,&nbsp;Yitong Zhao ,&nbsp;Yueqian Zhou ,&nbsp;Ye Tian ,&nbsp;Jialing Le","doi":"10.1016/j.combustflame.2025.114142","DOIUrl":"10.1016/j.combustflame.2025.114142","url":null,"abstract":"<div><div>The study examines the influence of kerosene and ethylene fuels on combustion instability characteristics at various equivalence ratios, with the objective of investigating supersonic combustion instability induced by combustion-induced backpressure. It was revealed that flow separation, triggered by this backpressure, plays a crucial role in combustion instability. The propagation of flow separation upstream can be classified into three typical flow states, with the timing between these states dependent on the fuel type and equivalence ratio. Hysteresis effects were noted during the flow separation propagation in both upstream and downstream directions. Different fuels and equivalence ratios have a direct impact on the magnitude of combustion-induced backpressure. Lower backpressure is linked to decreased combustion intensity and a flame front position closer to the upstream region, resulting in distinct combustion instability characteristics. Spectral analysis indicated that low-frequency oscillations (100–200 Hz) are associated with flame flashback and blowoff, while mid-to-low frequency oscillations (300–1000 Hz) originate from oscillations between the upstream and downstream regions of the combustor and the cavity shear layer. High-frequency oscillations (1000–3000 Hz) are connected to acoustic self-excited oscillations within the cavity. Correlation analysis was performed between the flame luminosity intensity in different combustor regions and the total luminosity intensity to clarify the oscillation characteristics of the cavity recirculation zone and the cavity shear layer. A method was developed using a weighted Damköhler number to evaluate combustion stability, taking into account the contributions of the cavity recirculation zone stabilized mode and the cavity shear layer stabilized mode. The results of this method regarding flame stability are in good agreement with the experimental observations.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114142"},"PeriodicalIF":5.8,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143714499","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}