Pub Date : 2024-10-28DOI: 10.1016/j.combustflame.2024.113804
Zhi-Min Wang , Du Wang , Ahmed E. Mansy , Zhen-Yu Tian
<div><div>1-Methoxy-2-propanol (PM, CC(O)COC) is a simple and representative hydroxyl ether that has gained attention as an alternative biofuel. In this study, the pyrolysis of PM was investigated in an atmospheric pressure flow reactor within the temperature range of 573 to 1173 K. Gas chromatographs were utilized to detect the species produced during the pyrolysis experiment. Acetaldehyde, <em>n</em>-butene, <em>i</em>-butene, and acetone were newly identified among the eighteen products and intermediates in PM pyrolysis. <em>Ab initio</em> calculations were employed to investigate the potential energy surface and pressure-dependent rate coefficients of PM unimolecular decomposition. The energetically favored channel for unimolecular initiation reactions is found to be H<sub>2</sub>O elimination. Based on the bond dissociation energies of PM, a detailed kinetic model consisting of 608 species and 3160 reactions was proposed with reasonable predictions against the experimental results. Rate-of-production analysis reveals that the consumption of PM is mainly controlled by H-abstractions involving H and CH<sub>3</sub> radicals at three different carbon sites to generate radicals C<sub>4</sub>H<sub>9</sub>O<sub>2</sub>-1, C<sub>4</sub>H<sub>9</sub>O<sub>2</sub>-2 and C<sub>4</sub>H<sub>9</sub>O<sub>2</sub>-3, respectively. At 1023 K, the conversion rate of PM reaches around 75%, and the reaction 2CH<sub>3</sub> (+M) = C<sub>2</sub>H<sub>6</sub> (+M) exhibits the greatest inhibition effect, while the reaction C<sub>4</sub>H<sub>10</sub>O<sub>2</sub>=C<sub>3</sub>H<sub>6</sub>OH2-1+CH<sub>3</sub>O has the greatest promotion effect on PM consumptions. The results contribute to better understand the pyrolysis behavior, enhancing the utilization of PM as a sustainable energy source.</div></div><div><h3>Novelty and significance statement</h3><div>1-Methoxy-2-propanol (PM) is an alternative biofuel, yet there is a significant lack of research exploring its kinetic behavior. The novelty of this work focuses on the atmospheric-pressure pyrolysis of PM. The PM pyrolysis experiments were carried out with newly detected intermediates and products involved in the process. To further enhance the understanding of PM kinetic behavior, a new kinetic model consisting of 608 species and 3160 reactions was developed. This model was utilized to predict the mole fractions of PM, H<sub>2</sub>, CO and important intermediates and products during the pyrolysis process. Additionally, the ROP and analyses were conducted to shed light on the reaction routes. Before this work, there was a lack of comprehensive investigation into the kinetics of PM pyrolysis, making this study significant in bridging the knowledge gap in this field. The findings of this investigation not only contribute to our understanding of PM pyrolysis kinetics but also serve as a foundation for further exploration of oxygenated additives fuel. By elucidating the mechanisms and pathways involved in the pyro
{"title":"Pyrolysis and kinetic modeling investigation of 1-methoxy-2-propanol","authors":"Zhi-Min Wang , Du Wang , Ahmed E. Mansy , Zhen-Yu Tian","doi":"10.1016/j.combustflame.2024.113804","DOIUrl":"10.1016/j.combustflame.2024.113804","url":null,"abstract":"<div><div>1-Methoxy-2-propanol (PM, CC(O)COC) is a simple and representative hydroxyl ether that has gained attention as an alternative biofuel. In this study, the pyrolysis of PM was investigated in an atmospheric pressure flow reactor within the temperature range of 573 to 1173 K. Gas chromatographs were utilized to detect the species produced during the pyrolysis experiment. Acetaldehyde, <em>n</em>-butene, <em>i</em>-butene, and acetone were newly identified among the eighteen products and intermediates in PM pyrolysis. <em>Ab initio</em> calculations were employed to investigate the potential energy surface and pressure-dependent rate coefficients of PM unimolecular decomposition. The energetically favored channel for unimolecular initiation reactions is found to be H<sub>2</sub>O elimination. Based on the bond dissociation energies of PM, a detailed kinetic model consisting of 608 species and 3160 reactions was proposed with reasonable predictions against the experimental results. Rate-of-production analysis reveals that the consumption of PM is mainly controlled by H-abstractions involving H and CH<sub>3</sub> radicals at three different carbon sites to generate radicals C<sub>4</sub>H<sub>9</sub>O<sub>2</sub>-1, C<sub>4</sub>H<sub>9</sub>O<sub>2</sub>-2 and C<sub>4</sub>H<sub>9</sub>O<sub>2</sub>-3, respectively. At 1023 K, the conversion rate of PM reaches around 75%, and the reaction 2CH<sub>3</sub> (+M) = C<sub>2</sub>H<sub>6</sub> (+M) exhibits the greatest inhibition effect, while the reaction C<sub>4</sub>H<sub>10</sub>O<sub>2</sub>=C<sub>3</sub>H<sub>6</sub>OH2-1+CH<sub>3</sub>O has the greatest promotion effect on PM consumptions. The results contribute to better understand the pyrolysis behavior, enhancing the utilization of PM as a sustainable energy source.</div></div><div><h3>Novelty and significance statement</h3><div>1-Methoxy-2-propanol (PM) is an alternative biofuel, yet there is a significant lack of research exploring its kinetic behavior. The novelty of this work focuses on the atmospheric-pressure pyrolysis of PM. The PM pyrolysis experiments were carried out with newly detected intermediates and products involved in the process. To further enhance the understanding of PM kinetic behavior, a new kinetic model consisting of 608 species and 3160 reactions was developed. This model was utilized to predict the mole fractions of PM, H<sub>2</sub>, CO and important intermediates and products during the pyrolysis process. Additionally, the ROP and analyses were conducted to shed light on the reaction routes. Before this work, there was a lack of comprehensive investigation into the kinetics of PM pyrolysis, making this study significant in bridging the knowledge gap in this field. The findings of this investigation not only contribute to our understanding of PM pyrolysis kinetics but also serve as a foundation for further exploration of oxygenated additives fuel. By elucidating the mechanisms and pathways involved in the pyro","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"271 ","pages":"Article 113804"},"PeriodicalIF":5.8,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528498","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}
Pub Date : 2024-10-28DOI: 10.1016/j.combustflame.2024.113805
Quan-De Wang , Bi-Yao Wang , Qian Yao , Jinhu Liang , Ping Zeng , Jian-Gang Liu , Zu-Xi Xia
Alternative jet fuel from Fischer-Tropsch (FT) synthesis represents an important kind of aviation fuel in the near future. However, the combustion properties of FT jet fuel have not been fully explored yet. Herein, this work reports an experimental and kinetic modeling study on the ignition characteristics of a coal-derived FT jet fuel. To facilitate its usage as a “drop-in” fuel in current aircraft and infrastructure, a blended fuel of the present FT fuel with a traditional RP-3 jet fuel with relatively high aromatic hydrocarbons is also prepared and studied. Specifically, a shock tube facility is employed to measure the ignition delay times (IDTs) of the FT, RP-3, and the blended jet fuels under the combustion conditions, i.e., temperature ranging from 1000–1800 K, pressure at 3 and 10 bar, equivalence ratio at 0.5, 1.0, and 2.0. Two-dimensional gas chromatography (GC × GC) analysis is adopted to determine the chemical compositions of the FT and RP-3 jet fuels, which is then used to aid the development of surrogate models. Most importantly, the contemporary combustion chemical kinetic mechanism via detailed generation, automatic generation, lumping, decoupling and HyChem methods are employed to model the IDTs, and the mechanism reproducibility of these mechanisms are systematically compared. The present work should be valuable to understand the chemical structure effect on alternative jet fuels and also provides important information for the development of different kinds of combustion kinetic mechanisms.
{"title":"An experimental and kinetic modeling study on the ignition property of an alternative gas to liquid jet fuel","authors":"Quan-De Wang , Bi-Yao Wang , Qian Yao , Jinhu Liang , Ping Zeng , Jian-Gang Liu , Zu-Xi Xia","doi":"10.1016/j.combustflame.2024.113805","DOIUrl":"10.1016/j.combustflame.2024.113805","url":null,"abstract":"<div><div>Alternative jet fuel from Fischer-Tropsch (FT) synthesis represents an important kind of aviation fuel in the near future. However, the combustion properties of FT jet fuel have not been fully explored yet. Herein, this work reports an experimental and kinetic modeling study on the ignition characteristics of a coal-derived FT jet fuel. To facilitate its usage as a “drop-in” fuel in current aircraft and infrastructure, a blended fuel of the present FT fuel with a traditional RP-3 jet fuel with relatively high aromatic hydrocarbons is also prepared and studied. Specifically, a shock tube facility is employed to measure the ignition delay times (IDTs) of the FT, RP-3, and the blended jet fuels under the combustion conditions, i.e., temperature ranging from 1000–1800 K, pressure at 3 and 10 bar, equivalence ratio at 0.5, 1.0, and 2.0. Two-dimensional gas chromatography (GC × GC) analysis is adopted to determine the chemical compositions of the FT and RP-3 jet fuels, which is then used to aid the development of surrogate models. Most importantly, the contemporary combustion chemical kinetic mechanism via detailed generation, automatic generation, lumping, decoupling and HyChem methods are employed to model the IDTs, and the mechanism reproducibility of these mechanisms are systematically compared. The present work should be valuable to understand the chemical structure effect on alternative jet fuels and also provides important information for the development of different kinds of combustion kinetic mechanisms.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"271 ","pages":"Article 113805"},"PeriodicalIF":5.8,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528422","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}
Pub Date : 2024-10-26DOI: 10.1016/j.combustflame.2024.113802
Xiaoyong Ding , Yitong Fang , Siqi Wang , Yao Zhou , Qiangqiang Liu , Yingle Liu , Ning Liu
AlH3 is a highly promising additive for energetic materials and has gained considerable attention as a substitute fuel for aluminum in solid propellants. In order to improve its compatibility with energetic materials and oxidants, carbon coating materials are often used. Nitrated graphene oxide (NGO) was prepared and used as a surface modifier of α-AlH3 in our study. Various analytical techniques were utilized to examine its structure and morphology, including Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), particle size distribution (PSD) and X-ray diffraction (XRD). The oxidization, ignition characteristics, flame propagation behavior and heat of combustion of AlH3 and AlH3/NGO powder were investigated using differential thermal analysis (DTA), a laser igniter, a high-speed camera and an oxygen bomb calorimetry. Results show that NGO coating agent catalyzes the thermal decomposition and hydrogenation process of AlH3, and accelerates the oxidation process of AlH3. The addition of 4 % NGO decreases the oxidation activation energy of AlH3 by about 8.94 %. The laser ignition energy of AlH3/NGO is much lower than that of AlH3, and the ignition energy decreases linearly as NGO is added from 1 % to 10 %. The flame development process supports the good thermal conductivity assistance effect of an appropriate amount of NGO in the combustion process of AlH3 in air, which is consistent with the result of oxygen bomb test, indicating that the addition of NGO leads to an improvement in the combustion efficiency of AlH3.This may provide valuable insights for the development of new high-energy solid propellants.
{"title":"Ignition and combustion properties of NGO coated AlH3","authors":"Xiaoyong Ding , Yitong Fang , Siqi Wang , Yao Zhou , Qiangqiang Liu , Yingle Liu , Ning Liu","doi":"10.1016/j.combustflame.2024.113802","DOIUrl":"10.1016/j.combustflame.2024.113802","url":null,"abstract":"<div><div>AlH<sub>3</sub> is a highly promising additive for energetic materials and has gained considerable attention as a substitute fuel for aluminum in solid propellants. In order to improve its compatibility with energetic materials and oxidants, carbon coating materials are often used. Nitrated graphene oxide (NGO) was prepared and used as a surface modifier of <em>α</em>-AlH<sub>3</sub> in our study. Various analytical techniques were utilized to examine its structure and morphology, including Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), particle size distribution (PSD) and X-ray diffraction (XRD). The oxidization, ignition characteristics, flame propagation behavior and heat of combustion of AlH<sub>3</sub> and AlH<sub>3</sub>/NGO powder were investigated using differential thermal analysis (DTA), a laser igniter, a high-speed camera and an oxygen bomb calorimetry. Results show that NGO coating agent catalyzes the thermal decomposition and hydrogenation process of AlH<sub>3</sub>, and accelerates the oxidation process of AlH<sub>3</sub>. The addition of 4 % NGO decreases the oxidation activation energy of AlH<sub>3</sub> by about 8.94 %. The laser ignition energy of AlH<sub>3</sub>/NGO is much lower than that of AlH<sub>3</sub>, and the ignition energy decreases linearly as NGO is added from 1 % to 10 %. The flame development process supports the good thermal conductivity assistance effect of an appropriate amount of NGO in the combustion process of AlH<sub>3</sub> in air, which is consistent with the result of oxygen bomb test, indicating that the addition of NGO leads to an improvement in the combustion efficiency of AlH<sub>3</sub>.This may provide valuable insights for the development of new high-energy solid propellants.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"271 ","pages":"Article 113802"},"PeriodicalIF":5.8,"publicationDate":"2024-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528421","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}
Pub Date : 2024-10-24DOI: 10.1016/j.combustflame.2024.113750
Sun Cen , Wei Xiaolin , Liu Huimin , Li Sen , Li Fei , Li Teng
The solid-to-gas phase transition of potassium during biomass combustion significantly impacts ash-related issues in bioenergy systems, affecting operational efficiency and equipment longevity. However, the specific mechanisms and kinetics of this transition process remain inadequately understood. This work investigates the time-resolved transition of solid-phase potassium to the gas phase during the combustion of rice husk and wheat straw pellets, combining experimental measurements with theoretical modeling. Tunable diode laser absorption spectroscopy (TDLAS) was employed to measure atomic potassium concentrations 15 mm above burning pellets tray, where gas-phase equilibrium is approached. Key combustion characteristics including thermogravimetric profiles, spectral radiation, and temperature were simultaneously monitored. A novel multi-step model was developed to describe the transition of different forms of solid-phase potassium (organic, exchangeable, and inorganic) to the gas phase. This model integrates TDLAS measurements, observed combustion characteristics, and biomass physicochemical properties. Thermodynamic equilibrium calculations were used to estimate the atomic potassium fraction from total gaseous potassium. The results showed that the solid-to-gas phase transition of organic potassium synchronizes with volatiles release. In contrast, the maximum emission rates of inorganic and exchangeable potassium occurred at the onset of char combustion. The developed model agrees well with the online detection experiments and were further validated by offline ICP analysis of residual ash. While not directly simulating gas-solid interface reactions near the particle surface, this work lays groundwork for future multi-scale modeling of particle-laden flows and reactor-scale phenomena in biomass combustion systems.
{"title":"Solid-to-gas phase transition kinetics of diverse potassium occurrence forms during biomass pellet combustion: Time-resolved detection and multi-step modeling","authors":"Sun Cen , Wei Xiaolin , Liu Huimin , Li Sen , Li Fei , Li Teng","doi":"10.1016/j.combustflame.2024.113750","DOIUrl":"10.1016/j.combustflame.2024.113750","url":null,"abstract":"<div><div>The solid-to-gas phase transition of potassium during biomass combustion significantly impacts ash-related issues in bioenergy systems, affecting operational efficiency and equipment longevity. However, the specific mechanisms and kinetics of this transition process remain inadequately understood. This work investigates the time-resolved transition of solid-phase potassium to the gas phase during the combustion of rice husk and wheat straw pellets, combining experimental measurements with theoretical modeling. Tunable diode laser absorption spectroscopy (TDLAS) was employed to measure atomic potassium concentrations 15 mm above burning pellets tray, where gas-phase equilibrium is approached. Key combustion characteristics including thermogravimetric profiles, spectral radiation, and temperature were simultaneously monitored. A novel multi-step model was developed to describe the transition of different forms of solid-phase potassium (organic, exchangeable, and inorganic) to the gas phase. This model integrates TDLAS measurements, observed combustion characteristics, and biomass physicochemical properties. Thermodynamic equilibrium calculations were used to estimate the atomic potassium fraction from total gaseous potassium. The results showed that the solid-to-gas phase transition of organic potassium synchronizes with volatiles release. In contrast, the maximum emission rates of inorganic and exchangeable potassium occurred at the onset of char combustion. The developed model agrees well with the online detection experiments and were further validated by offline ICP analysis of residual ash. While not directly simulating gas-solid interface reactions near the particle surface, this work lays groundwork for future multi-scale modeling of particle-laden flows and reactor-scale phenomena in biomass combustion systems.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113750"},"PeriodicalIF":5.8,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534773","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}
Pub Date : 2024-10-23DOI: 10.1016/j.combustflame.2024.113792
Shangkun Zhou , A. Abd El-Sabor Mohamed , Shashank S. Nagaraja , Pengzhi Wang , Yuki Murakami , Jiaxin Liu , Peter K. Senecal , Henry J. Curran
In this study, a new mechanism is developed to simulate hydrogen/n-decane blends. It is validated in the temperature range 650–1500 K, at p = 30 bar, for equivalence ratios of 0.5, 1.0, and 2.0 in ‘air’ for 99/1, 95/5 and 80/20 (mol%) blends of hydrogen/n-decane using ignition delay time (IDT) data recorded in both an RCM and in a shock tube. Additionally, the mechanism's performance is assessed against existing literature data for both pure hydrogen and pure n-decane, demonstrating overall satisfactory agreement compared to the experimental measurements.
This study also explores the effects of n-decane addition to hydrogen at different temperatures (600 K, 900 K, and 1500 K) at p = 30 bar pressure for a stoichiometric mixture (φ = 1.0). At 600 K, where pure hydrogen fails to ignite, the introduction of 1% n-decane initiates ignition, albeit with considerably extended IDTs. At 900 K, the addition of 1% n-decane enhances reactivity, while at 1500 K, it diminishes reactivity and extends the IDT. The underlying reasons for these observed effects are reported.
We provide valuable insights into the reactivity of dual fuel mixtures of hydrogen and n-decane encompassing low (600–800 K), intermediate (800–1200 K), and high (> 1200 K) temperature ranges. At low and intermediate temperatures, the inclusion of n-decane enhances reactivity. Consequently, for application in practical road transport combustion systems, the use of n-decane or extended-chain n-alkanes is recommended as suitable pilot fuels. Conversely, at high-temperature combustion conditions, the utilization of pilot fuels composed of linear alkanes is observed to impede reactivity.
{"title":"An experimental and modeling study of hydrogen/n-decane blends","authors":"Shangkun Zhou , A. Abd El-Sabor Mohamed , Shashank S. Nagaraja , Pengzhi Wang , Yuki Murakami , Jiaxin Liu , Peter K. Senecal , Henry J. Curran","doi":"10.1016/j.combustflame.2024.113792","DOIUrl":"10.1016/j.combustflame.2024.113792","url":null,"abstract":"<div><div>In this study, a new mechanism is developed to simulate hydrogen/<em>n</em>-decane blends. It is validated in the temperature range 650–1500 K, at <em>p</em> = 30 bar, for equivalence ratios of 0.5, 1.0, and 2.0 in ‘air’ for 99/1, 95/5 and 80/20 (mol%) blends of hydrogen/<em>n</em>-decane using ignition delay time (IDT) data recorded in both an RCM and in a shock tube. Additionally, the mechanism's performance is assessed against existing literature data for both pure hydrogen and pure <em>n</em>-decane, demonstrating overall satisfactory agreement compared to the experimental measurements.</div><div>This study also explores the effects of <em>n</em>-decane addition to hydrogen at different temperatures (600 K, 900 K, and 1500 K) at <em>p</em> = 30 bar pressure for a stoichiometric mixture (<em>φ</em> = 1.0). At 600 K, where pure hydrogen fails to ignite, the introduction of 1% <em>n</em>-decane initiates ignition, albeit with considerably extended IDTs. At 900 K, the addition of 1% <em>n</em>-decane enhances reactivity, while at 1500 K, it diminishes reactivity and extends the IDT. The underlying reasons for these observed effects are reported.</div><div>We provide valuable insights into the reactivity of dual fuel mixtures of hydrogen and <em>n</em>-decane encompassing low (600–800 K), intermediate (800–1200 K), and high (> 1200 K) temperature ranges. At low and intermediate temperatures, the inclusion of <em>n</em>-decane enhances reactivity. Consequently, for application in practical road transport combustion systems, the use of <em>n</em>-decane or extended-chain <em>n</em>-alkanes is recommended as suitable pilot fuels. Conversely, at high-temperature combustion conditions, the utilization of pilot fuels composed of linear alkanes is observed to impede reactivity.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113792"},"PeriodicalIF":5.8,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535225","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}
Pub Date : 2024-10-23DOI: 10.1016/j.combustflame.2024.113709
Victorien P. Blanchard, Yacine Bechane, Nicolas Q. Minesi, Stéphane Q.E. Wang, Benoît Fiorina, Christophe O. Laux
This paper presents quantitative experimental data generated for the validation of plasma-assisted combustion (PAC) simulations. These data are then used to validate the phenomenological model of Castela et al. They are also useful to test other PAC models. In the experiment presented here, Nanosecond Repetitively Pulsed (NRP) discharges are applied to a lean-premixed turbulent methane-air flame initially near the lean blow-off limit. The discharges significantly enhance the combustion and stabilize the flame after a few pulses. Electrical and optical diagnostics are employed to extensively quantify the transient and steady state of the plasma-stabilization process. The flame shape is characterized by OH* chemiluminescence imaging. In the discharge region, OH density profiles are obtained by 1D laser-induced fluorescence, and the gas temperature is measured by optical emission spectroscopy measurements. The local gas temperature increases by 1250 K, and the OH number density rises sevenfold when NRP discharges are applied. These results evidence the cumulative thermal and chemical effects of NRP discharges, which are especially challenging to replicate numerically. A Large Eddy Simulation (LES) of the experiment is performed. Combustion chemistry is modeled by an analytically reduced mechanism, while the plasma discharge is described by the low-CPU cost phenomenological model of Castela et al., which aims to capture the main thermal and chemical effects induced by the discharges. The model of Castela et al. is validated in the burnt gases by the remarkable agreement between the simulations and the experiments regarding the flame shape, the local gas temperature, and the OH number density. More generally, this work demonstrates the relevance of simplified plasma models in LES solvers to simulate complex plasma-assisted burners.
{"title":"Experimental characterization and 3D simulations of turbulent flames assisted by nanosecond plasma discharges","authors":"Victorien P. Blanchard, Yacine Bechane, Nicolas Q. Minesi, Stéphane Q.E. Wang, Benoît Fiorina, Christophe O. Laux","doi":"10.1016/j.combustflame.2024.113709","DOIUrl":"10.1016/j.combustflame.2024.113709","url":null,"abstract":"<div><div>This paper presents quantitative experimental data generated for the validation of plasma-assisted combustion (PAC) simulations. These data are then used to validate the phenomenological model of Castela et al. They are also useful to test other PAC models. In the experiment presented here, Nanosecond Repetitively Pulsed (NRP) discharges are applied to a lean-premixed turbulent methane-air flame initially near the lean blow-off limit. The discharges significantly enhance the combustion and stabilize the flame after a few pulses. Electrical and optical diagnostics are employed to extensively quantify the transient and steady state of the plasma-stabilization process. The flame shape is characterized by OH* chemiluminescence imaging. In the discharge region, OH density profiles are obtained by 1D laser-induced fluorescence, and the gas temperature is measured by optical emission spectroscopy measurements. The local gas temperature increases by 1250 K, and the OH number density rises sevenfold when NRP discharges are applied. These results evidence the cumulative thermal and chemical effects of NRP discharges, which are especially challenging to replicate numerically. A Large Eddy Simulation (LES) of the experiment is performed. Combustion chemistry is modeled by an analytically reduced mechanism, while the plasma discharge is described by the low-CPU cost phenomenological model of Castela et al., which aims to capture the main thermal and chemical effects induced by the discharges. The model of Castela et al. is validated in the burnt gases by the remarkable agreement between the simulations and the experiments regarding the flame shape, the local gas temperature, and the OH number density. More generally, this work demonstrates the relevance of simplified plasma models in LES solvers to simulate complex plasma-assisted burners.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113709"},"PeriodicalIF":5.8,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534774","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}
Pub Date : 2024-10-23DOI: 10.1016/j.combustflame.2024.113800
Yu Xie, Junfeng Yang, Pervez Ahmed, Benjamin John Alexander Thorne, Xiaojun Gu
The 3D swinging laser sheet technique was employed to study the development and morphological characteristics of premixed hydrogen-air unstable flames in a spherical explosion vessel. Pressure dependencies for laminar flame propagation were sought to exploit the role of the Darrieus-Landau (DL) and Thermal-diffusive (TD) instabilities in the unstable self-accelerating flame regime. A sufficiently low Markstein number, as a consequence of the increased pressure, leads to more cracking and smaller cells over the flame surface. The degree of wrinkling on the flame surface is proportional to the increase in flame burning velocity, a relationship that holds true for low pressures but is not applicable under high pressures. External turbulence can significantly alter the extent of flame surface wrinkling even at low root mean square velocities, producing a more wrinkled flame surface compared to intrinsic cellularity, and distinctly affecting flame dynamics. The increased wrinkling and flame speed due to external turbulence can be attributed to the synergistic effects between thermo-diffusive instabilities and turbulence, resulting in higher fuel consumption rates per flame surface area and the formation of finger-like structures that enhance flame displacement speed in curved segments. The parameters, , deviation of the Lewis number from a critical value, and , obtained through classical linear stability analysis, display a clear linear relationship with the ratio of the wrinkled surface area observed in planar flames. This study enhances the understanding of hydrogen flame instabilities, which is crucial for preventing explosions in hydrogen storage and utilization, and provides valuable insights into flame dynamics, supporting the design of safer and more efficient hydrogen-fueled engines and turbines.
{"title":"Three-dimensional dynamics of unstable lean premixed hydrogen-air flames: Intrinsic instabilities and morphological characteristics","authors":"Yu Xie, Junfeng Yang, Pervez Ahmed, Benjamin John Alexander Thorne, Xiaojun Gu","doi":"10.1016/j.combustflame.2024.113800","DOIUrl":"10.1016/j.combustflame.2024.113800","url":null,"abstract":"<div><div>The 3D swinging laser sheet technique was employed to study the development and morphological characteristics of premixed hydrogen-air unstable flames in a spherical explosion vessel. Pressure dependencies for laminar flame propagation were sought to exploit the role of the Darrieus-Landau (DL) and Thermal-diffusive (TD) instabilities in the unstable self-accelerating flame regime. A sufficiently low Markstein number, as a consequence of the increased pressure, leads to more cracking and smaller cells over the flame surface. The degree of wrinkling on the flame surface is proportional to the increase in flame burning velocity, a relationship that holds true for low pressures but is not applicable under high pressures. External turbulence can significantly alter the extent of flame surface wrinkling even at low root mean square velocities, producing a more wrinkled flame surface compared to intrinsic cellularity, and distinctly affecting flame dynamics. The increased wrinkling and flame speed due to external turbulence can be attributed to the synergistic effects between thermo-diffusive instabilities and turbulence, resulting in higher fuel consumption rates per flame surface area and the formation of finger-like structures that enhance flame displacement speed in curved segments. The parameters, <span><math><mi>ϵ</mi></math></span>, deviation of the Lewis number from a critical value, and <span><math><msub><mi>ω</mi><mn>2</mn></msub></math></span>, obtained through classical linear stability analysis, display a clear linear relationship with the ratio of the wrinkled surface area observed in planar flames. This study enhances the understanding of hydrogen flame instabilities, which is crucial for preventing explosions in hydrogen storage and utilization, and provides valuable insights into flame dynamics, supporting the design of safer and more efficient hydrogen-fueled engines and turbines.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"271 ","pages":"Article 113800"},"PeriodicalIF":5.8,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528496","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}
Pub Date : 2024-10-22DOI: 10.1016/j.combustflame.2024.113782
Véranika Latour, Daniel Durox, Antoine Renaud, Sébastien Candel
At a stage where new architectures and alternative fuels are being proposed to tackle the environmental challenges, it is important to be able to deal with combustion dynamics issues that may arise in these new developments. Reduced order models are generally considered for that purpose but their capacity to predict combustion instabilities is still not fully demonstrated. One advantage of these models is that they mainly rely on flame transfer or describing functions (FTFs or FDFs) representing the flames’ response to incoming disturbances. Recent measurements indicate that FDFs exhibit gain and phase variations with fuels, fuel blends, injector characteristics, but also with operating conditions. However, FTFs and FDFs are generally documented only for a few operating points and do not cover the entire domain of operation, limiting the scope of the analysis. The logical step taken in the present investigation is to collect FDFs for a large number of flow conditions of the laboratory-scale annular combustor MICCA-Spray. This is achieved using a single-injector system, SICCA-Spray, representing one sector of MICCA-Spray and that allows external flame modulation. The collected FDF data correspond to injectors of two types, characterized by different combustion dynamics in MICCA-Spray. This FDF database, in combination with an analytical framework derived from acoustic energy balance equations, serves to determine growth rates and define a theoretical instability domain. A comparison with the stability maps obtained in the annular combustor indicates that the general layout of these maps can be retrieved for the two injector types, validating the relevance of this data-driven model-based analysis of thermo-acoustic instabilities.
Novelty and significance statement
The novelty of this work lies in the reported flame describing function (FDF) database, measured in the single-injector setup SICCA-Spray, for a wide range of operating conditions corresponding to the operation domain of the MICCA-Spray annular combustor, and for two types of injectors leading to different flame dynamics (stable and unstable). An analytical framework is then used to determine growth rates of oscillation based on the FDF data, enabling to perform a stability analysis and interpret the observations in MICCA-Spray: the differences in flame dynamics observed between the two injectors are successfully retrieved, and for the unstable injector, stable and unstable regions of the operating domain can also be distinguished.
This work is significant because it provides an analytical framework of interest from a theoretical standpoint and for practical applications that is validated against a broad experimental dataset.
{"title":"Data-driven model-based instability prediction in an annular combustor relying on a flame response mapping of the operating domain","authors":"Véranika Latour, Daniel Durox, Antoine Renaud, Sébastien Candel","doi":"10.1016/j.combustflame.2024.113782","DOIUrl":"10.1016/j.combustflame.2024.113782","url":null,"abstract":"<div><div>At a stage where new architectures and alternative fuels are being proposed to tackle the environmental challenges, it is important to be able to deal with combustion dynamics issues that may arise in these new developments. Reduced order models are generally considered for that purpose but their capacity to predict combustion instabilities is still not fully demonstrated. One advantage of these models is that they mainly rely on flame transfer or describing functions (FTFs or FDFs) representing the flames’ response to incoming disturbances. Recent measurements indicate that FDFs exhibit gain and phase variations with fuels, fuel blends, injector characteristics, but also with operating conditions. However, FTFs and FDFs are generally documented only for a few operating points and do not cover the entire domain of operation, limiting the scope of the analysis. The logical step taken in the present investigation is to collect FDFs for a large number of flow conditions of the laboratory-scale annular combustor MICCA-Spray. This is achieved using a single-injector system, SICCA-Spray, representing one sector of MICCA-Spray and that allows external flame modulation. The collected FDF data correspond to injectors of two types, characterized by different combustion dynamics in MICCA-Spray. This FDF database, in combination with an analytical framework derived from acoustic energy balance equations, serves to determine growth rates and define a theoretical instability domain. A comparison with the stability maps obtained in the annular combustor indicates that the general layout of these maps can be retrieved for the two injector types, validating the relevance of this data-driven model-based analysis of thermo-acoustic instabilities.</div><div><strong>Novelty and significance statement</strong></div><div>The novelty of this work lies in the reported flame describing function (FDF) database, measured in the single-injector setup SICCA-Spray, for a wide range of operating conditions corresponding to the operation domain of the MICCA-Spray annular combustor, and for two types of injectors leading to different flame dynamics (stable and unstable). An analytical framework is then used to determine growth rates of oscillation based on the FDF data, enabling to perform a stability analysis and interpret the observations in MICCA-Spray: the differences in flame dynamics observed between the two injectors are successfully retrieved, and for the unstable injector, stable and unstable regions of the operating domain can also be distinguished.</div><div>This work is significant because it provides an analytical framework of interest from a theoretical standpoint and for practical applications that is validated against a broad experimental dataset.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113782"},"PeriodicalIF":5.8,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534775","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}
Pub Date : 2024-10-22DOI: 10.1016/j.combustflame.2024.113776
Abel Faure-Beaulieu , Bayu Dharmaputra , Bruno Schuermans , Guoqing Wang , Stephan Caruso , Maximilian Zahn , Nicolas Noiray
<div><div>Destructive thermoacoustic instabilities may potentially slow down significantly the ongoing development of hydrogen combustors for decarbonizing aviation. Their early prediction requires the knowledge of the heat release rate response of individual flames to acoustic perturbations. Obtaining this response at engine conditions is very challenging as it requires the development of sophisticated acoustic actuation and sensing techniques for harsh temperature and pressure environment. To date, experimental measurements of the response of single-flames to upstream and downstream acoustic excitation have been limited to academic burners operated at atmospheric condition. Moreover, to the authors knowledge, the response of turbulent non-premixed H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>/air flames has not been experimentally investigated yet, not even at atmospheric pressure. Our experiments address this challenge by determining the acoustic transfer matrix of rich-quench-lean H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> flames anchored on an industrial prototype burner at engine-relevant conditions, including high-altitude flight. The response of the flame is measured up to 2 kHz by using the multi microphone method (MMM). It is shown that the MMM becomes more sensitive to temperature estimations at high frequency and we outline a strategy to improve the method. It is found that the acoustic response of these H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>/air non-premixed flames exhibit large gains with non-monotonic trends over a wide frequency range. Different fuel-to-air ratios and flow velocities are considered up to nearly 7 bar. We show that the equivalence ratio and operating pressure do not alter significantly the acoustic flame response, while the flow velocity does, although the flame shape is nearly unchanged when the latter parameter is varied. Furthermore, we extend the classic model of low-Mach-number flame transfer matrices to the relevant case of RQL combustors.</div><div><strong>Novelty and Significance</strong></div><div>The ability to accurately measure, at relevant mean pressure, the transfer matrix linking acoustic pressure and velocity across a single burner and its turbulent H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>/air flame is key for the development of H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> powered medium-range civil aircrafts. This is because such measurement enables predictions of potential thermoacoustic instabilities in the full annular combustor featuring a large number of burners and flames, and therefore it offers possibilities for burner prototype selection and optimization before full engine tests. The present study is the first demonstration of such challenging measurement, revealing the peculiar acoustic response of non-premixed H<span><m
{"title":"Measuring acoustic transfer matrices of high-pressure hydrogen/air flames for aircraft propulsion","authors":"Abel Faure-Beaulieu , Bayu Dharmaputra , Bruno Schuermans , Guoqing Wang , Stephan Caruso , Maximilian Zahn , Nicolas Noiray","doi":"10.1016/j.combustflame.2024.113776","DOIUrl":"10.1016/j.combustflame.2024.113776","url":null,"abstract":"<div><div>Destructive thermoacoustic instabilities may potentially slow down significantly the ongoing development of hydrogen combustors for decarbonizing aviation. Their early prediction requires the knowledge of the heat release rate response of individual flames to acoustic perturbations. Obtaining this response at engine conditions is very challenging as it requires the development of sophisticated acoustic actuation and sensing techniques for harsh temperature and pressure environment. To date, experimental measurements of the response of single-flames to upstream and downstream acoustic excitation have been limited to academic burners operated at atmospheric condition. Moreover, to the authors knowledge, the response of turbulent non-premixed H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>/air flames has not been experimentally investigated yet, not even at atmospheric pressure. Our experiments address this challenge by determining the acoustic transfer matrix of rich-quench-lean H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> flames anchored on an industrial prototype burner at engine-relevant conditions, including high-altitude flight. The response of the flame is measured up to 2 kHz by using the multi microphone method (MMM). It is shown that the MMM becomes more sensitive to temperature estimations at high frequency and we outline a strategy to improve the method. It is found that the acoustic response of these H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>/air non-premixed flames exhibit large gains with non-monotonic trends over a wide frequency range. Different fuel-to-air ratios and flow velocities are considered up to nearly 7 bar. We show that the equivalence ratio and operating pressure do not alter significantly the acoustic flame response, while the flow velocity does, although the flame shape is nearly unchanged when the latter parameter is varied. Furthermore, we extend the classic model of low-Mach-number flame transfer matrices to the relevant case of RQL combustors.</div><div><strong>Novelty and Significance</strong></div><div>The ability to accurately measure, at relevant mean pressure, the transfer matrix linking acoustic pressure and velocity across a single burner and its turbulent H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>/air flame is key for the development of H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> powered medium-range civil aircrafts. This is because such measurement enables predictions of potential thermoacoustic instabilities in the full annular combustor featuring a large number of burners and flames, and therefore it offers possibilities for burner prototype selection and optimization before full engine tests. The present study is the first demonstration of such challenging measurement, revealing the peculiar acoustic response of non-premixed H<span><m","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113776"},"PeriodicalIF":5.8,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534776","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}
Pub Date : 2024-10-17DOI: 10.1016/j.combustflame.2024.113794
Qilong Fang , Jun Fang , Wei Li , Tianyou Lian , Long Zhao , Wang Li , Lili Ye , Yuyang Li
Ethoxysilanes are a family of precursors widely used in flame synthesis of silica nanoparticles. The existence of a silicon atom greatly amplifies the complexity of ethoxysilane combustion reactions, especially the detection of silicon-containing products and exploration of the specific reaction pathways, which hinders the unambiguous understanding of the combustion chemistry of ethoxysilanes. As the first part of a serial work on the combustion of dimethyldiethoxysilane (DMDEOS), a representative ethoxysilane precursor, reports a theoretical, experimental, and kinetic modeling investigation on its pyrolysis. The potential energy surface and rate constants show that the four-membered ethylene elimination dominates the decomposition of DMDEOS. Pyrolysis products in the micro-flow reactor pyrolysis of DMDEOS are detected using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS), including six silicon-containing products and an abundant of hydrocarbon molecules and radicals. Novel insight is provided into the unclear ethanol formation mechanism in previous pyrolysis investigations of ethoxysilanes. Previously proposed one-step mechanisms are found to be less efficient based on theoretical exploration and experimental evidence. A new multi-step mechanism initiated from the ethanol elimination of HOSi(CH3)2OC2H5 is concluded to be energy-favorable, which is supported by the identification of relevant products in the micro-flow reactor pyrolysis experiment. Based on the product information detected by SVUV-PIMS and the exploration of ethanol formation mechanism, a kinetic model of DMDEOS pyrolysis is constructed and validated against the new data that flow reactor pyrolysis of DMDEOS at 1.05 atm and 849–1113 K using gas chromatography. The model can effectively reproduce the formation of observed products and successfully address the substantial underprediction of ethanol caused by previously proposed one-step mechanisms. Modeling analyses, including rate of production analysis and sensitivity analysis, are performed to provide insight into the key pathways of DMDEOS decomposition and product formation.
{"title":"Unraveling combustion chemistry of dimethyldiethoxysilane. I. A comprehensive pyrolysis investigation with insight into ethanol formation mechanism in combustion of ethoxysilane flame synthesis precursors","authors":"Qilong Fang , Jun Fang , Wei Li , Tianyou Lian , Long Zhao , Wang Li , Lili Ye , Yuyang Li","doi":"10.1016/j.combustflame.2024.113794","DOIUrl":"10.1016/j.combustflame.2024.113794","url":null,"abstract":"<div><div>Ethoxysilanes are a family of precursors widely used in flame synthesis of silica nanoparticles. The existence of a silicon atom greatly amplifies the complexity of ethoxysilane combustion reactions, especially the detection of silicon-containing products and exploration of the specific reaction pathways, which hinders the unambiguous understanding of the combustion chemistry of ethoxysilanes. As the first part of a serial work on the combustion of dimethyldiethoxysilane (DMDEOS), a representative ethoxysilane precursor, reports a theoretical, experimental, and kinetic modeling investigation on its pyrolysis. The potential energy surface and rate constants show that the four-membered ethylene elimination dominates the decomposition of DMDEOS. Pyrolysis products in the micro-flow reactor pyrolysis of DMDEOS are detected using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS), including six silicon-containing products and an abundant of hydrocarbon molecules and radicals. Novel insight is provided into the unclear ethanol formation mechanism in previous pyrolysis investigations of ethoxysilanes. Previously proposed one-step mechanisms are found to be less efficient based on theoretical exploration and experimental evidence. A new multi-step mechanism initiated from the ethanol elimination of HOSi(CH<sub>3</sub>)<sub>2</sub>OC<sub>2</sub>H<sub>5</sub> is concluded to be energy-favorable, which is supported by the identification of relevant products in the micro-flow reactor pyrolysis experiment. Based on the product information detected by SVUV-PIMS and the exploration of ethanol formation mechanism, a kinetic model of DMDEOS pyrolysis is constructed and validated against the new data that flow reactor pyrolysis of DMDEOS at 1.05 atm and 849–1113 K using gas chromatography. The model can effectively reproduce the formation of observed products and successfully address the substantial underprediction of ethanol caused by previously proposed one-step mechanisms. Modeling analyses, including rate of production analysis and sensitivity analysis, are performed to provide insight into the key pathways of DMDEOS decomposition and product formation.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113794"},"PeriodicalIF":5.8,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142445588","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}
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