Combustion and Flame最新文献_第2页

Kinetic roles of energy transformation during ignition enhancement of NH3/air mixture by non-equilibrium plasma discharge via nanosecond repetitive pulsed discharge

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-02-19 DOI: 10.1016/j.combustflame.2025.114061

Zhencao Zheng, Yong Hu, Ruijiao Cao, Weixin Rong, Feiyang Zhao, Wenbin Yu

In this work, a numerical study and multi-scale process analysis of plasma assisted ammonia ignition with nanosecond repetitive pulse discharge at room temperature and pressure are carried out under varied applied voltages. Analysis of theoretical plasma thermal-chemical instability and Gibbs free energy confidence to ignition spontaneity through plasma intervention are performed. In addition, the present study extends the ability of modelling deposition energy transformation accounted for plasma kinetics interact with vibrational-translational relaxation, electron attachment/detachment. To identify the significant reaction paths on plasma systems reactivity, a plasma-based global pathway analysis (PGPA) was derived from element-flux transfer including repeated nodes within cyclic reaction step (de-excitation to ground state). It is concluded that although a large amount of plasma generated in the pulse discharge causes a rapid but short-lived temperature rise in the system, heat release from chemical reactions during the pulse interval is the primary cause of combustion system heating. Kinetics analysis discloses that oxygen decomposition (O₂=>O) and ammonia dehydrogenation (NH₃=>NH₂) are two key processes stimulating ignition. Furthermore, O₂ is decomposed into O and O(1D) through collisions with electrons and excited state N₂ (N₂(B) and N₂(C)) in the pulse discharge, and O(1D) subsequently relaxes and quenches into O. Ammonia dehydrogenation occurs at the same time as a result of collision dissociation. Provisions on activated radicals and energy transfer at low temperature are made due to plasma participant, thus facilitating to trigger subsequent NH₃ oxidation chain reactions. The present study provides insights and guidance to discover the underlying plasma kinetic roles when performing ignition enhancement of NH₃/air mixture.

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引用次数: 0

Mechanism of liquid oxygen temperature on combustion stability of gas-liquid swirl coaxial injectors 液氧温度对气液漩涡同轴喷射器燃烧稳定性的影响机理

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-02-18 DOI: 10.1016/j.combustflame.2025.114050

Pengjin Cao, Peng Cheng, Xiao Bai, Qinglian Li, Ziguang Li, Jingjing Liao

Deep-throttling variable thrust cryogenic propellants rocket engines are facing the challenge of unstable combustion caused by propellants temperature. To explore the effect of liquid oxygen temperature on the combustion stability of liquid oxygen/methane engine, spray images and CH* chemiluminescence images were obtained synchronously using laser background light imaging. The dynamic characteristics of spray and flame at different liquid oxygen temperatures were studied. The mechanisms of low- and medium-frequency unstable combustion were analyzed. The liquid oxygen temperature has a significant influence on the combustion stability of the gas liquid swirl coaxial injectors. As the liquid oxygen temperature decreases, the frequencies of low- and medium-frequency oscillation combustion modes decrease, and the oscillation intensity increases. Eventually, both the low- and medium- frequency unstable combustion disappear. At the same total mass flow rate, the spray projection area of liquid oxygen decreases with increasing liquid oxygen temperature, while both the flame projection area and flame length increase. The low-frequency oscillation combustion mode results from the interaction between the fluctuating mass flow of liquid oxygen injected into the combustor and the vaporization of liquid oxygen inside the injector. When the liquid oxygen boiling position is near the surface of the gas core, partial vaporization of liquid oxygen inside the injector occurs, leading to the appearance of the medium-frequency oscillation combustion mode in the combustor. However, when the liquid oxygen boiling position exceeds the liquid sheet thickness of the swirl chamber, the liquid oxygen inside the injector remains in a purely liquid phase, resulting in stable combustion. Both low- and medium-frequency combustion instabilities can be effectively suppressed by increasing the combustor pressure or decreasing the liquid oxygen temperature.

{"title":"Mechanism of liquid oxygen temperature on combustion stability of gas-liquid swirl coaxial injectors","authors":"Pengjin Cao, Peng Cheng, Xiao Bai, Qinglian Li, Ziguang Li, Jingjing Liao","doi":"10.1016/j.combustflame.2025.114050","DOIUrl":"10.1016/j.combustflame.2025.114050","url":null,"abstract":"<div><div>Deep-throttling variable thrust cryogenic propellants rocket engines are facing the challenge of unstable combustion caused by propellants temperature. To explore the effect of liquid oxygen temperature on the combustion stability of liquid oxygen/methane engine, spray images and CH* chemiluminescence images were obtained synchronously using laser background light imaging. The dynamic characteristics of spray and flame at different liquid oxygen temperatures were studied. The mechanisms of low- and medium-frequency unstable combustion were analyzed. The liquid oxygen temperature has a significant influence on the combustion stability of the gas liquid swirl coaxial injectors. As the liquid oxygen temperature decreases, the frequencies of low- and medium-frequency oscillation combustion modes decrease, and the oscillation intensity increases. Eventually, both the low- and medium- frequency unstable combustion disappear. At the same total mass flow rate, the spray projection area of liquid oxygen decreases with increasing liquid oxygen temperature, while both the flame projection area and flame length increase. The low-frequency oscillation combustion mode results from the interaction between the fluctuating mass flow of liquid oxygen injected into the combustor and the vaporization of liquid oxygen inside the injector. When the liquid oxygen boiling position is near the surface of the gas core, partial vaporization of liquid oxygen inside the injector occurs, leading to the appearance of the medium-frequency oscillation combustion mode in the combustor. However, when the liquid oxygen boiling position exceeds the liquid sheet thickness of the swirl chamber, the liquid oxygen inside the injector remains in a purely liquid phase, resulting in stable combustion. Both low- and medium-frequency combustion instabilities can be effectively suppressed by increasing the combustor pressure or decreasing the liquid oxygen temperature.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114050"},"PeriodicalIF":5.8,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143437977","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}

引用次数: 0

Improve energy release of boron by tunable metal-organic frameworks via synergetic micro-explosion and catalysis 通过微爆炸和催化协同作用，利用可调金属有机框架改善硼的能量释放

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-02-18 DOI: 10.1016/j.combustflame.2025.114062

Kang Xue , Huaiyu Li , Lun Pan , Chongjun Li , Minhua Ai , Chengxiang Shi , Xiangwen Zhang , Ji-Jun Zou

Boron is considered as one of the most promising high energy additives to improve the energy density of aerospace propellants and energetic materials. However, the low energy release properties restrict its practical applications. Herein, three kinds of boron-based composite energetic particles (nB@MOF) were prepared by encapsulating nano boron (nB) in metal-organic frameworks (MOFs) by a self-assembly method with Zn, Co and Mo as metal nodes, and 2-methylimidazole and ethylenediamine as organic ligands. The characterization and dynamics results show that the combustion of organic ligands can induce micro-explosion to destroy the surface oxidation layer of agglomeration and promote the oxidation efficiency of boron. Furthermore, the metal oxide catalyst generated in-situ on nB surface by metal nodes can reduce the initial oxidation temperature and improve the mass transfer distance and interface contact of the oxidation reaction. Compared with nB, the maximum pressurization rate of nB@MOF with 2-methylimidazole as the organic ligand is increased by 31.1 times, the initial oxidation temperature of nB@MOF with Mo as the metal node is reduced by 185.9°C, and the combustion heat of all nB@MOF are increased by more than 1.2 times. This work demonstrates that the energy release properties of boron can be effectively improved by synergistic effect of micro-explosion process and interfacial catalysis.

{"title":"Improve energy release of boron by tunable metal-organic frameworks via synergetic micro-explosion and catalysis","authors":"Kang Xue , Huaiyu Li , Lun Pan , Chongjun Li , Minhua Ai , Chengxiang Shi , Xiangwen Zhang , Ji-Jun Zou","doi":"10.1016/j.combustflame.2025.114062","DOIUrl":"10.1016/j.combustflame.2025.114062","url":null,"abstract":"<div><div>Boron is considered as one of the most promising high energy additives to improve the energy density of aerospace propellants and energetic materials. However, the low energy release properties restrict its practical applications. Herein, three kinds of boron-based composite energetic particles (nB@MOF) were prepared by encapsulating nano boron (nB) in metal-organic frameworks (MOFs) by a self-assembly method with Zn, Co and Mo as metal nodes, and 2-methylimidazole and ethylenediamine as organic ligands. The characterization and dynamics results show that the combustion of organic ligands can induce micro-explosion to destroy the surface oxidation layer of agglomeration and promote the oxidation efficiency of boron. Furthermore, the metal oxide catalyst generated <em>in-situ</em> on nB surface by metal nodes can reduce the initial oxidation temperature and improve the mass transfer distance and interface contact of the oxidation reaction. Compared with nB, the maximum pressurization rate of nB@MOF with 2-methylimidazole as the organic ligand is increased by 31.1 times, the initial oxidation temperature of nB@MOF with Mo as the metal node is reduced by 185.9°C, and the combustion heat of all nB@MOF are increased by more than 1.2 times. This work demonstrates that the energy release properties of boron can be effectively improved by synergistic effect of micro-explosion process and interfacial catalysis.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114062"},"PeriodicalIF":5.8,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430118","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}

引用次数: 0

Distinct evaporation and combustion behaviors of suspended and unsuspended nanodiesel droplets 悬浮和未悬浮纳米odiesel 液滴的蒸发和燃烧行为各不相同

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-02-18 DOI: 10.1016/j.combustflame.2025.114060

Álvaro Muelas, Taha Poonawala, Javier Ballester

This work reports the main evaporation and combustion characteristics of diesel droplets doped with different concentrations of alumina and ceria nanoparticles (NPs) for a range of conditions scarcely explored and relevant for combustion applications: high-temperature and reducing/oxidizing atmospheres (0/10 % O₂). Due to the potential influence of the particular experimental conditions, all tests are performed using two different setups: a free-falling droplet (FFD) rig and a suspended droplet (SD) facility, following a systematic study that is considered especially pertinent for particle-laden fuels. The reported results demonstrate, for the first time, a great influence of the test method on some of the observed behaviors, which can perfectly justify some contradictions and even inconsistencies observed in previous works. Tests on unsuspended nanodiesel droplets provide smooth evaporation curves until the onset of a single and violent microexplosion that shatters the droplets, whereas the testing of suspended droplets yields a fluctuating evaporation process, with a wide range of sequential disruptive phenomena of different intensities (swelling, puffing, weak microexplosions). These clear differences point to the impact of the suspension filaments on disruptive behaviors for the range of conditions explored, even when very thin ceramic fibers are employed. In spite of these differences, some common features have also been identified. Namely, the addition of NPs does not drive significant changes in the droplet evaporation rate, probably due to the small impact of thermal radiation for the tested conditions. However, the onset of disruptive phenomena shortens the liquid conversion times as compared to neat diesel, with an earlier occurrence as the NP concentration increases, especially for FFD tests. Among the two tested nanoparticles, ceria shows significantly stronger disruptive events and also a progressive reduction in evaporation rate for unsuspended droplets, which is consistent with the formation of a less permeable shell for this kind of NP.

{"title":"Distinct evaporation and combustion behaviors of suspended and unsuspended nanodiesel droplets","authors":"Álvaro Muelas, Taha Poonawala, Javier Ballester","doi":"10.1016/j.combustflame.2025.114060","DOIUrl":"10.1016/j.combustflame.2025.114060","url":null,"abstract":"<div><div>This work reports the main evaporation and combustion characteristics of diesel droplets doped with different concentrations of alumina and ceria nanoparticles (NPs) for a range of conditions scarcely explored and relevant for combustion applications: high-temperature and reducing/oxidizing atmospheres (0/10 % O<sub>2</sub>). Due to the potential influence of the particular experimental conditions, all tests are performed using two different setups: a free-falling droplet (FFD) rig and a suspended droplet (SD) facility, following a systematic study that is considered especially pertinent for particle-laden fuels. The reported results demonstrate, for the first time, a great influence of the test method on some of the observed behaviors, which can perfectly justify some contradictions and even inconsistencies observed in previous works. Tests on unsuspended nanodiesel droplets provide smooth evaporation curves until the onset of a single and violent microexplosion that shatters the droplets, whereas the testing of suspended droplets yields a fluctuating evaporation process, with a wide range of sequential disruptive phenomena of different intensities (swelling, puffing, weak microexplosions). These clear differences point to the impact of the suspension filaments on disruptive behaviors for the range of conditions explored, even when very thin ceramic fibers are employed. In spite of these differences, some common features have also been identified. Namely, the addition of NPs does not drive significant changes in the droplet evaporation rate, probably due to the small impact of thermal radiation for the tested conditions. However, the onset of disruptive phenomena shortens the liquid conversion times as compared to neat diesel, with an earlier occurrence as the NP concentration increases, especially for FFD tests. Among the two tested nanoparticles, ceria shows significantly stronger disruptive events and also a progressive reduction in evaporation rate for unsuspended droplets, which is consistent with the formation of a less permeable shell for this kind of NP.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114060"},"PeriodicalIF":5.8,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143437978","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}

引用次数: 0

Development and validation of a framework to predict the linear stability of transverse thermoacoustic modes of a reheat combustor

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-02-16 DOI: 10.1016/j.combustflame.2025.114010

Simon M. Heinzmann , Harish S. Gopalakrishnan , Francesco Gant , Mirko R. Bothien

To achieve fully carbon-neutral, fuel-flexible and on-demand grid power delivery, gas turbines featuring constant pressure sequential combustion architecture show great potential. A sequential combustor is comprised of two axially-staged combustion chambers with the first stage typically being a swirl-stabilised propagating flame. Post first stage combustion, the exhaust stream is first diluted with air and later enriched with additional fuel in the second stage resulting in a vitiated product mixture at high temperatures leading to auto-ignition. Thermoacoustically-stable combustion stages are critical to ensure low emissions, high reliability and ensure mechanical integrity. The second stage firing under auto-ignition conditions can be subject to transversal instabilities. This article presents a finite element coupled method to model the thermoacoustic behaviour of a second stage reheat flame in an efficient, cost-effective approach. To do so, prior techniques to model the response of autoignition-stabilised flames to longitudinal acoustic perturbations is leveraged to quantify the auto-ignition flame’s heat release rate response to transverse acoustic waves. Subsequently, the framework is used to compute the stability of transverse eigenmodes for an atmospheric reheat combustor. Validation is performed by comparison to experimentally obtained pressure sensor measurements and chemiluminescence imaging of the flame. It is observed that the framework can correctly predict the combustor’s unstable first transverse mode and also capture the dynamic flame response qualitatively. Consequently, the framework presented in this work can be leveraged to get reliable and time-efficient stability estimates of the transverse thermoacoustic modes in experimental reheat burners.

{"title":"Development and validation of a framework to predict the linear stability of transverse thermoacoustic modes of a reheat combustor","authors":"Simon M. Heinzmann , Harish S. Gopalakrishnan , Francesco Gant , Mirko R. Bothien","doi":"10.1016/j.combustflame.2025.114010","DOIUrl":"10.1016/j.combustflame.2025.114010","url":null,"abstract":"<div><div>To achieve fully carbon-neutral, fuel-flexible and on-demand grid power delivery, gas turbines featuring constant pressure sequential combustion architecture show great potential. A sequential combustor is comprised of two axially-staged combustion chambers with the first stage typically being a swirl-stabilised propagating flame. Post first stage combustion, the exhaust stream is first diluted with air and later enriched with additional fuel in the second stage resulting in a vitiated product mixture at high temperatures leading to auto-ignition. Thermoacoustically-stable combustion stages are critical to ensure low emissions, high reliability and ensure mechanical integrity. The second stage firing under auto-ignition conditions can be subject to transversal instabilities. This article presents a finite element coupled method to model the thermoacoustic behaviour of a second stage reheat flame in an efficient, cost-effective approach. To do so, prior techniques to model the response of autoignition-stabilised flames to longitudinal acoustic perturbations is leveraged to quantify the auto-ignition flame’s heat release rate response to transverse acoustic waves. Subsequently, the framework is used to compute the stability of transverse eigenmodes for an atmospheric reheat combustor. Validation is performed by comparison to experimentally obtained pressure sensor measurements and chemiluminescence imaging of the flame. It is observed that the framework can correctly predict the combustor’s unstable first transverse mode and also capture the dynamic flame response qualitatively. Consequently, the framework presented in this work can be leveraged to get reliable and time-efficient stability estimates of the transverse thermoacoustic modes in experimental reheat burners.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114010"},"PeriodicalIF":5.8,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143421777","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}

引用次数: 0

Ab initio kinetics for H-atom abstraction from nitroethane

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-02-16 DOI: 10.1016/j.combustflame.2025.114033

Yinjun Chen , Siyu Cheng , Longfei Li , Jiaming Li , Wenlong Li , Frederick Nii Ofei Bruce , Yiheng Tong , Wei Lin , Fang Wang , Yang Li

Nitroethane (NTH) is nitro-containing energetic fuel for detonation engine. The study of the kinetic mechanism of nitroethane combustion is helpful for the development of models of nitrogen-containing energetic materials and provides theoretical support for CFD simulation of detonation engines. H-atom abstraction reactions play a crucial role as chain initiation processes in the detailed chemical kinetic modeling of NTH combustion. Therefore, high-level quantum chemical calculations were performed to determine the rate coefficients for eighteen abstraction reactions, as well as the thermodynamic properties of the species involved. M06–2X/6–311++G(d, p) level of theory was employed for geometry optimization, vibrational frequency calculation, Intrinsic Reaction Coordinate (IRC) analysis, and dihedral angle scans. The QCISD(T)/cc-pVXZ (X=D and T) MP2/cc-pVXZ (X=D, T and Q) and CCSD(T)/cc-pVXZ (X=T and Q) methods with two complete basis set extrapolations are employed for determining the single-point energy (SPE) for all species. The bond dissociation energies (BDEs) of all C-H, C–C, and C-N bonds in NTH were calculated at QCISD(T)//MP2//M06–2X/6–311++G(d, p) level. Rate constants and thermochemistry were carried out based on transition state theory (TST) and statistic thermodynamic theory using Multiwell software. The Master Equation System Solver (MESS) program suite was employed here to calculate the reaction rate constants for complex-forming reactions for ȮH and O₂ system. The reaction energy barriers and reaction rate constants calculated using two methods—QCISD(T)/cc-pVXZ (with X as D and T) and MP2/cc-pVXZ (with X as D, T, and Q), as well as CCSD(T)/cc-pVXZ (with X as T and Q)—show little difference. All results were then incorporated into the PLUG model, which significantly improved predictions for ignition delay time (IDT) as well as the speciation profile in both premixed flames and flow reactors. Sensitivity and flux analyses were conducted to identify the essential reactions controlling reactivity, revealing that H-atom abstraction by ȮH, Ḣ, CḢ₃, and O₂ are the critical reactions.

{"title":"Ab initio kinetics for H-atom abstraction from nitroethane","authors":"Yinjun Chen , Siyu Cheng , Longfei Li , Jiaming Li , Wenlong Li , Frederick Nii Ofei Bruce , Yiheng Tong , Wei Lin , Fang Wang , Yang Li","doi":"10.1016/j.combustflame.2025.114033","DOIUrl":"10.1016/j.combustflame.2025.114033","url":null,"abstract":"<div><div>Nitroethane (NTH) is nitro-containing energetic fuel for detonation engine. The study of the kinetic mechanism of nitroethane combustion is helpful for the development of models of nitrogen-containing energetic materials and provides theoretical support for CFD simulation of detonation engines. H-atom abstraction reactions play a crucial role as chain initiation processes in the detailed chemical kinetic modeling of NTH combustion. Therefore, high-level quantum chemical calculations were performed to determine the rate coefficients for eighteen abstraction reactions, as well as the thermodynamic properties of the species involved. M06–2X/6–311++G(d, p) level of theory was employed for geometry optimization, vibrational frequency calculation, Intrinsic Reaction Coordinate (IRC) analysis, and dihedral angle scans. The QCISD(T)/cc-pVXZ (X=D and T) MP2/cc-pVXZ (X=D, T and Q) and CCSD(T)/cc-pVXZ (X=T and Q) methods with two complete basis set extrapolations are employed for determining the single-point energy (SPE) for all species. The bond dissociation energies (BDEs) of all C-H, C–C, and C-N bonds in NTH were calculated at QCISD(T)//MP2//M06–2X/6–311++G(d, p) level. Rate constants and thermochemistry were carried out based on transition state theory (TST) and statistic thermodynamic theory using Multiwell software. The Master Equation System Solver (MESS) program suite was employed here to calculate the reaction rate constants for complex-forming reactions for ȮH and O<sub>2</sub> system. The reaction energy barriers and reaction rate constants calculated using two methods—QCISD(T)/cc-pVXZ (with X as D and T) and MP2/cc-pVXZ (with X as D, T, and Q), as well as CCSD(T)/cc-pVXZ (with X as T and Q)—show little difference. All results were then incorporated into the PLUG model, which significantly improved predictions for ignition delay time (IDT) as well as the speciation profile in both premixed flames and flow reactors. Sensitivity and flux analyses were conducted to identify the essential reactions controlling reactivity, revealing that H-atom abstraction by ȮH, Ḣ, CḢ<sub>3</sub>, and O<sub>2</sub> are the critical reactions.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 114033"},"PeriodicalIF":5.8,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422137","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}

引用次数: 0

Exploring the two-stage ignition of n-butylcyclohexane: A comprehensive experimental and modeling study

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-02-16 DOI: 10.1016/j.combustflame.2025.114047

Congjie Hong , Yuyang Zhang , Xin Zhang , Wuchuan Sun , Qianqian Li , Zuohua Huang , Janardhanraj Subburaj , Aamir Farooq , Zeimin Tian , Yingwen Yan , Jintao Wang , Yuanhao Deng , Shilin Zhong , Yingjia Zhang

n-Butylcyclohexane (NBCH) serves as a representative surrogate fuel in investigations concerning the combustion characteristics of both jet fuels and sustainable aviation fuels. Understanding its combustion behavior and developing high-fidelity chemical reaction kinetic models are crucial for fuel performance optimization. In this study, a comprehensive investigation of the oxidation kinetics of NBCH under low-temperature conditions was conducted and a novel experimental dataset including both total and first-stage ignition delay times was proposed. A broad range of experimental conditions was investigated, spanning temperatures from 675 - 1300 K and pressures from 5 - 20 atm, under pure oxygen and air conditions, thereby providing valuable data for numerical validation. An updated chemical kinetic model was developed by integrating the comprehensive core mechanism of NUIGMech 1.3 and 30 fuel layer reaction classes. The proposed model corrected errors in the rate coefficients of key reaction classes identified in previous literature and incorporated the latest rate coefficients from theoretical calculations for specific reaction classes, demonstrating superior performance compared to literature models in accurately predicting the first-stage and total ignition delay times under various operating conditions. Additionally, the model performance was assessed through comparisons with various datasets sourced from the literature. The results showed that the updated model provides accurate predictions across a wide range of parameters. The integration of experimental results and kinetic modeling offers deep insights into the combustion processes of n-butylcyclohexane. This comprehensive approach aids in developing more efficient combustion systems and contributes to the broader understanding of fuel behavior under varied operational conditions.

{"title":"Exploring the two-stage ignition of n-butylcyclohexane: A comprehensive experimental and modeling study","authors":"Congjie Hong , Yuyang Zhang , Xin Zhang , Wuchuan Sun , Qianqian Li , Zuohua Huang , Janardhanraj Subburaj , Aamir Farooq , Zeimin Tian , Yingwen Yan , Jintao Wang , Yuanhao Deng , Shilin Zhong , Yingjia Zhang","doi":"10.1016/j.combustflame.2025.114047","DOIUrl":"10.1016/j.combustflame.2025.114047","url":null,"abstract":"<div><div><em>n</em>-Butylcyclohexane (NBCH) serves as a representative surrogate fuel in investigations concerning the combustion characteristics of both jet fuels and sustainable aviation fuels. Understanding its combustion behavior and developing high-fidelity chemical reaction kinetic models are crucial for fuel performance optimization. In <em>this study</em>, a comprehensive investigation of the oxidation kinetics of NBCH under low-temperature conditions was conducted and a novel experimental dataset including both total and first-stage ignition delay times was proposed. A broad range of experimental conditions was investigated, spanning temperatures from 675 - 1300 K and pressures from 5 - 20 atm, under pure oxygen and air conditions, thereby providing valuable data for numerical validation. An updated chemical kinetic model was developed by integrating the comprehensive core mechanism of NUIGMech 1.3 and 30 fuel layer reaction classes. The proposed model corrected errors in the rate coefficients of key reaction classes identified in previous literature and incorporated the latest rate coefficients from theoretical calculations for specific reaction classes, demonstrating superior performance compared to literature models in accurately predicting the first-stage and total ignition delay times under various operating conditions. Additionally, the model performance was assessed through comparisons with various datasets sourced from the literature. The results showed that the updated model provides accurate predictions across a wide range of parameters. The integration of experimental results and kinetic modeling offers deep insights into the combustion processes of <em>n</em>-butylcyclohexane. This comprehensive approach aids in developing more efficient combustion systems and contributes to the broader understanding of fuel behavior under varied operational conditions.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 114047"},"PeriodicalIF":5.8,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422138","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}

引用次数: 0

Thermal oxidation and combustion characteristics of single particle AlH3 单颗粒 AlH3 的热氧化和燃烧特性

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-02-14 DOI: 10.1016/j.combustflame.2025.114038

Mengxia Sun , Fang Wang , Yukun Chen , Xueqin Liao , Jianzhong Liu

The oxygen content is a key factor influencing the ignition and combustion performance of AlH₃ particles. This study investigated the thermal decomposition and oxidation characteristics of AlH₃ under different oxygen concentrations using thermogravimetric analysis and differential scanning calorimetry. A tube furnace was used to collect reaction products at various temperatures, and their microstructures and crystal transformations were analyzed to explore the hydrogen release and oxidation mechanisms. Additionally, a settling furnace ignition experimental system was established to study the combustion characteristics and flame morphology of single AlH₃ particles under different oxygen content. The thermogravimetric results indicated that the thermal decomposition and oxidation reactions of AlH₃ under different oxygen concentrations could be divided into one weight loss stage and two weight gain stages. Although the amount and rate of reaction varied among the stages, there was little difference in the degree of oxidation at 1200 °C. The oxidation layer undergoes phase transformations from amorphous Al₂O₃ to γ-Al₂O₃ and finally to α-Al₂O₃, with needle-like structures appearing at 1000 °C. The combustion results showed that when the oxygen concentration is high, particles are prone to micro explosions. Simultaneously observed phenomena such as diffusion flames, growth of oxidation caps, and gas emission. The combustion time of AlH₃ was found to be slightly lower than the empirical values for aluminum, and the ignition delay time was also lower compared to aluminum. Both the ignition delay time and combustion time of the particles decreased with increasing environmental oxygen content.

{"title":"Thermal oxidation and combustion characteristics of single particle AlH3","authors":"Mengxia Sun , Fang Wang , Yukun Chen , Xueqin Liao , Jianzhong Liu","doi":"10.1016/j.combustflame.2025.114038","DOIUrl":"10.1016/j.combustflame.2025.114038","url":null,"abstract":"<div><div>The oxygen content is a key factor influencing the ignition and combustion performance of AlH<sub>3</sub> particles. This study investigated the thermal decomposition and oxidation characteristics of AlH<sub>3</sub> under different oxygen concentrations using thermogravimetric analysis and differential scanning calorimetry. A tube furnace was used to collect reaction products at various temperatures, and their microstructures and crystal transformations were analyzed to explore the hydrogen release and oxidation mechanisms. Additionally, a settling furnace ignition experimental system was established to study the combustion characteristics and flame morphology of single AlH<sub>3</sub> particles under different oxygen content. The thermogravimetric results indicated that the thermal decomposition and oxidation reactions of AlH<sub>3</sub> under different oxygen concentrations could be divided into one weight loss stage and two weight gain stages. Although the amount and rate of reaction varied among the stages, there was little difference in the degree of oxidation at 1200 °C. The oxidation layer undergoes phase transformations from amorphous Al<sub>2</sub>O<sub>3</sub> to γ-Al<sub>2</sub>O<sub>3</sub> and finally to α-Al<sub>2</sub>O<sub>3</sub>, with needle-like structures appearing at 1000 °C. The combustion results showed that when the oxygen concentration is high, particles are prone to micro explosions. Simultaneously observed phenomena such as diffusion flames, growth of oxidation caps, and gas emission. The combustion time of AlH<sub>3</sub> was found to be slightly lower than the empirical values for aluminum, and the ignition delay time was also lower compared to aluminum. Both the ignition delay time and combustion time of the particles decreased with increasing environmental oxygen content.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 114038"},"PeriodicalIF":5.8,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422136","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}

引用次数: 0

A computational study of differential diffusion characteristics in NH3/H2/N2-air non-premixed jet flames

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-02-14 DOI: 10.1016/j.combustflame.2025.114046

Junjun Guo, Francisco E. Hernández-Pérez, Takuya Tomidokoro, Hong G. Im

Partial cracking of ammonia presents a practical solution to the challenges posed by the low laminar burning velocity and high autoignition energy of pure ammonia. On the other hand, the presence of hydrogen in the fuel can induce significant differential mass diffusion in turbulent non-premixed flames. In this study, a direct numerical simulation (DNS) of a temporally evolving planar jet NH₃/H₂/N₂-air non-premixed flame was conducted to investigate the characteristics of differential diffusion in partially cracked ammonia flames. A recently proposed extended mixture fraction definition was employed to consider the effect of nitrogen element. The results indicate that the conditional mean temperature and mass fractions of major species consistently fall between those predicted by the two laminar flamelets, calculated using the mixture-averaged diffusion model and the unity Lewis number. Differential diffusion was quantitatively characterized by the difference in the mixture fractions of hydrogen and nitrogen elements. In the turbulent non-premixed flame with a high Reynolds number of 23,000, the extent of differential diffusion still reaches 60% of that observed in laminar condition. Moreover, a spatial filtering analysis in the context of large eddy simulation (LES) confirmed that differential diffusion is not reflected in the subgrid species flux, as it arises from the convection term rather than the diffusion term.

{"title":"A computational study of differential diffusion characteristics in NH3/H2/N2-air non-premixed jet flames","authors":"Junjun Guo, Francisco E. Hernández-Pérez, Takuya Tomidokoro, Hong G. Im","doi":"10.1016/j.combustflame.2025.114046","DOIUrl":"10.1016/j.combustflame.2025.114046","url":null,"abstract":"<div><div>Partial cracking of ammonia presents a practical solution to the challenges posed by the low laminar burning velocity and high autoignition energy of pure ammonia. On the other hand, the presence of hydrogen in the fuel can induce significant differential mass diffusion in turbulent non-premixed flames. In this study, a direct numerical simulation (DNS) of a temporally evolving planar jet NH<sub>3</sub>/H<sub>2</sub>/N<sub>2</sub>-air non-premixed flame was conducted to investigate the characteristics of differential diffusion in partially cracked ammonia flames. A recently proposed extended mixture fraction definition was employed to consider the effect of nitrogen element. The results indicate that the conditional mean temperature and mass fractions of major species consistently fall between those predicted by the two laminar flamelets, calculated using the mixture-averaged diffusion model and the unity Lewis number. Differential diffusion was quantitatively characterized by the difference in the mixture fractions of hydrogen and nitrogen elements. In the turbulent non-premixed flame with a high Reynolds number of 23,000, the extent of differential diffusion still reaches 60% of that observed in laminar condition. Moreover, a spatial filtering analysis in the context of large eddy simulation (LES) confirmed that differential diffusion is not reflected in the subgrid species flux, as it arises from the convection term rather than the diffusion term.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 114046"},"PeriodicalIF":5.8,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422135","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}

引用次数: 0

Asymptotic analysis of a planar reaction front in gasless combustion: Higher order effects and the influence of the large but finite Lewis number on the propagation velocity

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-02-14 DOI: 10.1016/j.combustflame.2025.114032

Mario Napieralski , Cesar Huete , Vadim N. Kurdyumov

An asymptotic analysis of a planar combustion front in a condensed phase with an arbitrary temperature dependence of thermal conductivity has been carried out by the method of matched asymptotic expansions. The Zel’dovich number is used as a large parameter, and three expansion terms are obtained for the flame velocity. The asymptotic results are compared with direct numerical calculations, and very good agreement is obtained even at low Zel’dovich numbers.

The effect of a large but finite Lewis number on the flame propagation velocity are also examined. It is shown that even at Lewis numbers of the order of the Zel’dovich number, the effect of fuel diffusion becomes significant. The presented asymptotic analysis allows us to write a uniformly valid expression for the propagation velocity that can be used both for large Lewis numbers and for Lewis numbers of order unity.

Novelty and significance statement

For the first time an analytical expression for the velocity of a planar combustion front in the condensed (gasless) phase was obtained up to third-order terms in the inverse Zel’dovich number, taking into account the arbitrary dependence of the thermal conductivity coefficient on temperature. For the first time, the influence of a small but finite reactant diffusion coefficient on the propagation velocity of a planar combustion front was analytically studied. The result allows us to write a uniformly valid formula for the flame velocity applicable in both the solid and gaseous phases.

{"title":"Asymptotic analysis of a planar reaction front in gasless combustion: Higher order effects and the influence of the large but finite Lewis number on the propagation velocity","authors":"Mario Napieralski , Cesar Huete , Vadim N. Kurdyumov","doi":"10.1016/j.combustflame.2025.114032","DOIUrl":"10.1016/j.combustflame.2025.114032","url":null,"abstract":"<div><div>An asymptotic analysis of a planar combustion front in a condensed phase with an arbitrary temperature dependence of thermal conductivity has been carried out by the method of matched asymptotic expansions. The Zel’dovich number is used as a large parameter, and three expansion terms are obtained for the flame velocity. The asymptotic results are compared with direct numerical calculations, and very good agreement is obtained even at low Zel’dovich numbers.</div><div>The effect of a large but finite Lewis number on the flame propagation velocity are also examined. It is shown that even at Lewis numbers of the order of the Zel’dovich number, the effect of fuel diffusion becomes significant. The presented asymptotic analysis allows us to write a uniformly valid expression for the propagation velocity that can be used both for large Lewis numbers and for Lewis numbers of order unity.</div><div><strong>Novelty and significance statement</strong></div><div>For the first time an analytical expression for the velocity of a planar combustion front in the condensed (gasless) phase was obtained up to third-order terms in the inverse Zel’dovich number, taking into account the arbitrary dependence of the thermal conductivity coefficient on temperature. For the first time, the influence of a small but finite reactant diffusion coefficient on the propagation velocity of a planar combustion front was analytically studied. The result allows us to write a uniformly valid formula for the flame velocity applicable in both the solid and gaseous phases.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114032"},"PeriodicalIF":5.8,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143421774","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}

引用次数: 0