Pub Date : 2025-01-01DOI: 10.1016/j.proci.2025.105892
Vaibhav Mysore Natesh, Ivan Langella
Electromagnetic fields influence flame behavior by altering the transport of paramagnetic species such as oxygen and OH radicals in hydrogen flames, affecting reaction pathways and combustion dynamics. This study presents a numerical investigation of the effects of magnetic fields on a premixed swirl-stabilized hydrogen flame using a modified combustion solver in OpenFOAM. Additional body force and diffusion terms were incorporated into the governing equations to model interactions with paramagnetic species, and the solver was validated against experimental data and simulations from the literature. The study focuses on analyzing flame structure, species redistribution, and mixture fraction variations under magnetic conditioning. Large Eddy Simulations (LES) with the Eulerian Stochastic Fields (ESF) method were employed to capture turbulence-chemistry interactions. The results indicate that the presence of a magnetic field induces an upstream-directed force on oxygen, leading to localized changes in mixture fraction and combustion characteristics. A reduction in temperature, heat release rate, and OH concentration was observed, with peak reductions of approximately 2%, 5%, and 6%, respectively. These effects are attributed to the redistribution of oxygen, which makes the flame locally leaner. This study extends the understanding of hydrogen combustion under electromagnetic influence and demonstrates the potential of magnetic fields for controlling the flame behavior. The findings provide new insights into magnetic field-assisted combustion strategies, offering a framework for further research in advanced propulsion and energy applications.
{"title":"Influence of magnetic field on flame dynamics in hydrogen flames: A numerical study","authors":"Vaibhav Mysore Natesh, Ivan Langella","doi":"10.1016/j.proci.2025.105892","DOIUrl":"10.1016/j.proci.2025.105892","url":null,"abstract":"<div><div>Electromagnetic fields influence flame behavior by altering the transport of paramagnetic species such as oxygen and OH radicals in hydrogen flames, affecting reaction pathways and combustion dynamics. This study presents a numerical investigation of the effects of magnetic fields on a premixed swirl-stabilized hydrogen flame using a modified combustion solver in OpenFOAM. Additional body force and diffusion terms were incorporated into the governing equations to model interactions with paramagnetic species, and the solver was validated against experimental data and simulations from the literature. The study focuses on analyzing flame structure, species redistribution, and mixture fraction variations under magnetic conditioning. Large Eddy Simulations (LES) with the Eulerian Stochastic Fields (ESF) method were employed to capture turbulence-chemistry interactions. The results indicate that the presence of a magnetic field induces an upstream-directed force on oxygen, leading to localized changes in mixture fraction and combustion characteristics. A reduction in temperature, heat release rate, and OH concentration was observed, with peak reductions of approximately 2%, 5%, and 6%, respectively. These effects are attributed to the redistribution of oxygen, which makes the flame locally leaner. This study extends the understanding of hydrogen combustion under electromagnetic influence and demonstrates the potential of magnetic fields for controlling the flame behavior. The findings provide new insights into magnetic field-assisted combustion strategies, offering a framework for further research in advanced propulsion and energy applications.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105892"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262549","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 : 2025-01-01DOI: 10.1016/j.proci.2025.105864
Hanzhang Cao, Wang Han, Yihao Tang, Lijun Yang
Accurate modeling of transcritical combustion is of critical importance for the development of high-efficiency rocket engines. While the one-dimensional flamelet theory has been extensively used in transcritical and supercritical combustion simulations, a comprehensive analysis of multi-dimensional flamelet effects remains scarce. To this end, a priori analysis of multi-dimensional flamelet effects in a transcritical LOX/GH2 jet flame is performed in this work by comparing 1D flamelet solutions with multi-dimensional flamelets extracted from DNS solutions. The results show that while conventional 1D flamelet solutions can provide a good approximation of the jet flame structure, incorporating differential diffusion helps to accurately predict the flame front position. Furthermore, asymptotic scaling analysis and budget analysis of generalized flamelet equations are conducted for the extracted flamelets. It is found that multi-dimensional flamelet effects do have a substantial impact on the jet flame. Nevertheless, flame-normal diffusion is dominant over flame-tangential diffusion. These findings suggest that the 1D flamelet assumption is reasonable for the transcritical LOX/GH2 jet flame and that attention should be paid to incorporating differential diffusion effects in the modeling of transcritical LOX/GH2 jet flames.
{"title":"A priori analysis of multi-dimensional flamelet effects in a transcritical LOX/GH2 jet flame","authors":"Hanzhang Cao, Wang Han, Yihao Tang, Lijun Yang","doi":"10.1016/j.proci.2025.105864","DOIUrl":"10.1016/j.proci.2025.105864","url":null,"abstract":"<div><div>Accurate modeling of transcritical combustion is of critical importance for the development of high-efficiency rocket engines. While the one-dimensional flamelet theory has been extensively used in transcritical and supercritical combustion simulations, a comprehensive analysis of multi-dimensional flamelet effects remains scarce. To this end, <em>a priori</em> analysis of multi-dimensional flamelet effects in a transcritical LOX/GH2 jet flame is performed in this work by comparing 1D flamelet solutions with multi-dimensional flamelets extracted from DNS solutions. The results show that while conventional 1D flamelet solutions can provide a good approximation of the jet flame structure, incorporating differential diffusion helps to accurately predict the flame front position. Furthermore, asymptotic scaling analysis and budget analysis of generalized flamelet equations are conducted for the extracted flamelets. It is found that multi-dimensional flamelet effects do have a substantial impact on the jet flame. Nevertheless, flame-normal diffusion is dominant over flame-tangential diffusion. These findings suggest that the 1D flamelet assumption is reasonable for the transcritical LOX/GH2 jet flame and that attention should be paid to incorporating differential diffusion effects in the modeling of transcritical LOX/GH2 jet flames.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105864"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145216399","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 : 2025-01-01DOI: 10.1016/j.proci.2025.105827
Christoph D.K. Schumann , James C. Massey , Caleb J. Li , Nedunchezhian Swaminathan
A lifted turbulent jet flame involves partial premixing and exhibits a tribrachial flame structure at its leading edge (LE). Its propagation from the initial sparking location towards the final stabilisation height has rich physics. Large eddy simulation (LES) with flamelet-based reaction rate closure for partially premixed combustion is employed to study this propagation. The initial kernel grows radially in the rich region, and it is skewed by the oncoming flow as it is convected downstream. An LE is formed as the flame propagates radially into lean mixtures with low streamwise velocities. This LE encounters the lean limit, while a core flame continues to develop closer to the jet centreline, where the mixture reactivity and flow velocity are significantly large. Eventually, this core flame overtakes the LE in the lean mixture and upstream propagation ensues. The LE propagates mostly in the lean mixture, as the streamwise velocity in the vicinity of the jet core is high, although occasional rapid propagation is observed as the core flame encounters highly reactive mixture due to turbulence. Hence, the two flame branches are competing to form the LE. This behaviour is quite different to propagation in a lifted methane jet flame due to the increased reactivity and wider flammability limits of hydrogen. Turbulence plays a fundamental role during propagation for the formation of new upstream flame kernels, which evolve from pockets of hot reactants and fresh mixture. These kernels may be convected downstream causing the LE to recede. Eventually, the LE reaches a stationary state, and the flame root stabilises at a position where the burning mass flux is balanced by the flame normal advective mass flux. The LE does not encounter the value of the extinction dissipation rate for the mixture fraction during its evolution towards the stabilisation and at this location.
{"title":"Large eddy simulation of transient leading edge propagation in a turbulent lifted hydrogen jet flame","authors":"Christoph D.K. Schumann , James C. Massey , Caleb J. Li , Nedunchezhian Swaminathan","doi":"10.1016/j.proci.2025.105827","DOIUrl":"10.1016/j.proci.2025.105827","url":null,"abstract":"<div><div>A lifted turbulent jet flame involves partial premixing and exhibits a tribrachial flame structure at its leading edge (LE). Its propagation from the initial sparking location towards the final stabilisation height has rich physics. Large eddy simulation (LES) with flamelet-based reaction rate closure for partially premixed combustion is employed to study this propagation. The initial kernel grows radially in the rich region, and it is skewed by the oncoming flow as it is convected downstream. An LE is formed as the flame propagates radially into lean mixtures with low streamwise velocities. This LE encounters the lean limit, while a core flame continues to develop closer to the jet centreline, where the mixture reactivity and flow velocity are significantly large. Eventually, this core flame overtakes the LE in the lean mixture and upstream propagation ensues. The LE propagates mostly in the lean mixture, as the streamwise velocity in the vicinity of the jet core is high, although occasional rapid propagation is observed as the core flame encounters highly reactive mixture due to turbulence. Hence, the two flame branches are competing to form the LE. This behaviour is quite different to propagation in a lifted methane jet flame due to the increased reactivity and wider flammability limits of hydrogen. Turbulence plays a fundamental role during propagation for the formation of new upstream flame kernels, which evolve from pockets of hot reactants and fresh mixture. These kernels may be convected downstream causing the LE to recede. Eventually, the LE reaches a stationary state, and the flame root stabilises at a position where the burning mass flux is balanced by the flame normal advective mass flux. The LE does not encounter the value of the extinction dissipation rate for the mixture fraction during its evolution towards the stabilisation and at this location.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105827"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262368","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 : 2025-01-01DOI: 10.1016/j.proci.2025.105928
Sarah N. Elliott , Maristella Di Teodoro , Simone Vari , Luna Pratali Maffei , Zeynep Serinyel , Océane Clement , Claire Grégoire , Eric L. Petersen , Olivier Mathieu , Guillaume Dayma , Carlo Cavallotti
A mechanistic understanding of alcohol pyrolysis and oxidation is critical to their effective integration into the fuel industry. 1-propanol (1-C3H7OH) is a promising biofuel and, moreover, its mechanism is a foundation for that of larger alcohols. As part of a combined modeling-experimental-theoretical investigation into 1-C3H7OH, we explore the H abstractions from 1-C3H7OH with ab initio transition state theory-based master equation (AI-TST-ME) evaluations for the two abstractors, OH and H, that are influential during 1-C3H7OH combustion. We report branching fractions between the resulting C3H7O radicals (i.e., at 1500 K, for the OH abstractor: 0.40, 0.27, 0.24, and 0.09 to α-, β−, γ−, and ο−C3H7O; for the H abstractor: 0.80, 0.14, 0.06, and 0.00). The sensitivity to level of theory as well as the influence of multidimensional torsional effects are evaluated for the abstractions by OH. Notably, the correction for torsional coupling for the α−C3H7O is about half of that as for the β−C3H7O – fully neglecting the multidimensional effect, then, would lead to significantly different branching fractions. The subsequent dissociation of the C3H7O radicals to nine products, including CH3, OH, ethene, ethyl radical, and H is also reported with AI-TST-ME computations. We find, however, that at relevant temperatures and pressures, very little 1-C3H7OH + OH collisionally stabilizes to thermalized C3H7O radicals (i.e., 7 % at 1 atm and 1500 K). Instead, the abundant, rovibrationally excited populations of C3H7O radicals promptly dissociate to the products. In the first exploration of the influence of non-thermal effects on the branching fractions to dissociation products, we find that H production enhances significantly (i.e., more than a factor of 2) at the cost of OH production.
{"title":"A theoretical study of 1-propanol H-abstractions and successive reactivity","authors":"Sarah N. Elliott , Maristella Di Teodoro , Simone Vari , Luna Pratali Maffei , Zeynep Serinyel , Océane Clement , Claire Grégoire , Eric L. Petersen , Olivier Mathieu , Guillaume Dayma , Carlo Cavallotti","doi":"10.1016/j.proci.2025.105928","DOIUrl":"10.1016/j.proci.2025.105928","url":null,"abstract":"<div><div>A mechanistic understanding of alcohol pyrolysis and oxidation is critical to their effective integration into the fuel industry. 1-propanol (1-C<sub>3</sub>H<sub>7</sub>OH) is a promising biofuel and, moreover, its mechanism is a foundation for that of larger alcohols. As part of a combined modeling-experimental-theoretical investigation into 1-C<sub>3</sub>H<sub>7</sub>OH, we explore the H abstractions from 1-C<sub>3</sub>H<sub>7</sub>OH with ab initio transition state theory-based master equation (AI-TST-ME) evaluations for the two abstractors, OH and H, that are influential during 1-C<sub>3</sub>H<sub>7</sub>OH combustion. We report branching fractions between the resulting C<sub>3</sub>H<sub>7</sub>O radicals (i.e., at 1500 K, for the OH abstractor: 0.40, 0.27, 0.24, and 0.09 to α-, β−, γ−, and ο−C<sub>3</sub>H<sub>7</sub>O; for the H abstractor: 0.80, 0.14, 0.06, and 0.00). The sensitivity to level of theory as well as the influence of multidimensional torsional effects are evaluated for the abstractions by OH. Notably, the correction for torsional coupling for the α−C<sub>3</sub>H<sub>7</sub>O is about half of that as for the β−C<sub>3</sub>H<sub>7</sub>O – fully neglecting the multidimensional effect, then, would lead to significantly different branching fractions. The subsequent dissociation of the C<sub>3</sub>H<sub>7</sub>O radicals to nine products, including CH<sub>3</sub>, OH, ethene, ethyl radical, and H is also reported with AI-TST-ME computations. We find, however, that at relevant temperatures and pressures, very little 1-C<sub>3</sub>H<sub>7</sub>OH + OH collisionally stabilizes to thermalized C<sub>3</sub>H<sub>7</sub>O radicals (i.e., 7 % at 1 atm and 1500 K). Instead, the abundant, rovibrationally excited populations of C<sub>3</sub>H<sub>7</sub>O radicals promptly dissociate to the products. In the first exploration of the influence of non-thermal effects on the branching fractions to dissociation products, we find that H production enhances significantly (i.e., more than a factor of 2) at the cost of OH production.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105928"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145412611","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 : 2025-01-01DOI: 10.1016/j.proci.2025.105932
D. Golc , S. Esposito , M. Khosravi , J. Beeckmann , H. Pitsch
The transition of the transport sector towards more sustainable propulsion requires the adoption of alternative fuels. Methanol and hydrogen are promising options because of their possible renewable production pathways, low to zero carbon content, low pollutant emission, and potential for reaching higher thermal efficiencies. A drawback is that hydrogen and methanol are more prone to hot-spot-induced pre-ignition (PI) due to their lower minimum ignition energy compared to conventional fuels. Hot-spot-induced PI can occur in engines due to hot surfaces acting as ignition points, which is a limiting factor for operation, safety and efficiency. Although undesirable in spark ignition engines (SI), hot-spot-induced ignition can facilitate the use of low-cetane fuels such as methanol and hydrogen in compression ignition engines (CI). Understanding the effects leading to hot-spot-induced pre-ignition is essential for both suppressing the phenomenon in SI engines and leveraging it in CI engines. This study investigates hot-spot-induced PI phenomena using an SI single-cylinder research engine featuring a prototype glow-plug equipped with an integrated thermocouple in order to create a controlled hot spot inside the combustion chamber. Methanol has been introduced in the combustion chamber with a direct injection (DI), while hydrogen with a port fuel injector (PFI). A parametric study was conducted using methanol and hydrogen to identify dependencies of PI events linked to certain engine operating parameters. A comprehensive data analysis featuring 3D Reynolds averaged Navier Stokes (RANS) and chemical kinetics simulations were conducted to explain the main mechanisms responsible for PI. Generally, hydrogen requires a higher hot-spot temperature to achieve pre-ignition compared to methanol. For methanol, this study provides insights into the dependencies of various parameters on the ignition timing in CI applications, allowing potentially to achieve a controllable CI combustion with glow-plug assistance. An important finding is that while methanol combustion can be effectively controlled through glow-plug temperature, the study demonstrates that such controllability is more challenging for hydrogen. Indeed, numerous parameters influencing hot-spot-induced ignition were identified. In particular, the local mixture composition near the glow-plug and elevated pressures were found to significantly impact the onset of PI, with higher pressures effectively suppressing pre-ignition. This counterintuitive behavior is explained by the inverse pressure dependence of ignition delay times for hydrogen and analyzed with reaction pathway analysis. Overall, it was observed that by adjusting the operating parameters, the potential hot-spot temperature required to trigger PI could be optimized, allowing for an increase of up to . These insights are essential for developing s
{"title":"Investigation of hot-spot-induced pre-ignition in methanol- and hydrogen-fueled spark-ignition engines","authors":"D. Golc , S. Esposito , M. Khosravi , J. Beeckmann , H. Pitsch","doi":"10.1016/j.proci.2025.105932","DOIUrl":"10.1016/j.proci.2025.105932","url":null,"abstract":"<div><div>The transition of the transport sector towards more sustainable propulsion requires the adoption of alternative fuels. Methanol and hydrogen are promising options because of their possible renewable production pathways, low to zero carbon content, low pollutant emission, and potential for reaching higher thermal efficiencies. A drawback is that hydrogen and methanol are more prone to hot-spot-induced pre-ignition (PI) due to their lower minimum ignition energy compared to conventional fuels. Hot-spot-induced PI can occur in engines due to hot surfaces acting as ignition points, which is a limiting factor for operation, safety and efficiency. Although undesirable in spark ignition engines (SI), hot-spot-induced ignition can facilitate the use of low-cetane fuels such as methanol and hydrogen in compression ignition engines (CI). Understanding the effects leading to hot-spot-induced pre-ignition is essential for both suppressing the phenomenon in SI engines and leveraging it in CI engines. This study investigates hot-spot-induced PI phenomena using an SI single-cylinder research engine featuring a prototype glow-plug equipped with an integrated thermocouple in order to create a controlled hot spot inside the combustion chamber. Methanol has been introduced in the combustion chamber with a direct injection (DI), while hydrogen with a port fuel injector (PFI). A parametric study was conducted using methanol and hydrogen to identify dependencies of PI events linked to certain engine operating parameters. A comprehensive data analysis featuring 3D Reynolds averaged Navier Stokes (RANS) and chemical kinetics simulations were conducted to explain the main mechanisms responsible for PI. Generally, hydrogen requires a higher hot-spot temperature to achieve pre-ignition compared to methanol. For methanol, this study provides insights into the dependencies of various parameters on the ignition timing in CI applications, allowing potentially to achieve a controllable CI combustion with glow-plug assistance. An important finding is that while methanol combustion can be effectively controlled through glow-plug temperature, the study demonstrates that such controllability is more challenging for hydrogen. Indeed, numerous parameters influencing hot-spot-induced ignition were identified. In particular, the local mixture composition near the glow-plug and elevated pressures were found to significantly impact the onset of PI, with higher pressures effectively suppressing pre-ignition. This counterintuitive behavior is explained by the inverse pressure dependence of ignition delay times for hydrogen and analyzed with reaction pathway analysis. Overall, it was observed that by adjusting the operating parameters, the potential hot-spot temperature required to trigger PI could be optimized, allowing for an increase of up to <span><math><mrow><mtext>100</mtext><mspace></mspace><mtext>K</mtext></mrow></math></span>. These insights are essential for developing s","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105932"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145412614","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 : 2025-01-01DOI: 10.1016/j.proci.2025.105982
A. Shamooni , R. Cheng , T. Zirwes , O.T. Stein , A. Kronenburg
Recently, advanced deep-learning techniques have been successfully applied as deconvolution operators to super-resolve the low-resolution data in large-eddy simulation (LES). The super-resolution (SR) operator provides an approximate inverse to the filter operators in LES such that the under-resolved and un-resolved sub-grid information can be reconstructed from the resolved scales. In this work, a particle-aware attention-based conditional super-resolution generative adversarial network (PACASRGAN) is proposed for the fourfold SR of gas field scalars which are generated by the pyrolysis process in a hot turbulent flow laden with pulverised biomass particles. Multiple carrier-phase direct numerical simulations (DNS) of two-way coupled particle-laden flows with heat and mass transfer, that mimic the near-burner field of pulverised biomass combustion (PBC) systems, are carried out to build the training/testing datasets. The model performance is assessed in an a priori manner by investigating statistical quantities of interest for the modelling in LES of PBC. The results show that the proposed model can super-resolve the temperature and mixture fraction fields to a good accuracy and outperforms unconditional GAN models. Particles create localised sources/sinks via two-way coupling which sharpen scalar gradients in the subgrid. The particle mask and feature vector encode this localisation to improve the predictions of the generator. The scalar spectra, the conditional average of unresolved scalar variances, the probability density function (PDF), and the conditional average of the square of the mixture fraction gradient from the reconstructed fields follow the DNS values well. Slight deviations are observed at rich conditions in conditional statistics and at the tail of the PDFs. Nonetheless, the results demonstrate that SR is applicable to two-way coupled particle-laden flows with heat and mass transfer, providing reasonably accurate high-resolution information for both the entire gas field and particle positions.
{"title":"Super-resolution reconstruction of scalar fields from the pyrolysis of pulverised biomass using deep learning","authors":"A. Shamooni , R. Cheng , T. Zirwes , O.T. Stein , A. Kronenburg","doi":"10.1016/j.proci.2025.105982","DOIUrl":"10.1016/j.proci.2025.105982","url":null,"abstract":"<div><div>Recently, advanced deep-learning techniques have been successfully applied as deconvolution operators to super-resolve the low-resolution data in large-eddy simulation (LES). The super-resolution (SR) operator provides an approximate inverse to the filter operators in LES such that the under-resolved and un-resolved sub-grid information can be reconstructed from the resolved scales. In this work, a particle-aware attention-based conditional super-resolution generative adversarial network (PACASRGAN) is proposed for the fourfold SR of gas field scalars which are generated by the pyrolysis process in a hot turbulent flow laden with pulverised biomass particles. Multiple carrier-phase direct numerical simulations (DNS) of two-way coupled particle-laden flows with heat and mass transfer, that mimic the near-burner field of pulverised biomass combustion (PBC) systems, are carried out to build the training/testing datasets. The model performance is assessed in an <em>a priori</em> manner by investigating statistical quantities of interest for the modelling in LES of PBC. The results show that the proposed model can super-resolve the temperature and mixture fraction fields to a good accuracy and outperforms unconditional GAN models. Particles create localised sources/sinks via two-way coupling which sharpen scalar gradients in the subgrid. The particle mask and feature vector encode this localisation to improve the predictions of the generator. The scalar spectra, the conditional average of unresolved scalar variances, the probability density function (PDF), and the conditional average of the square of the mixture fraction gradient from the reconstructed fields follow the DNS values well. Slight deviations are observed at rich conditions in conditional statistics and at the tail of the PDFs. Nonetheless, the results demonstrate that SR is applicable to two-way coupled particle-laden flows with heat and mass transfer, providing reasonably accurate high-resolution information for both the entire gas field and particle positions.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105982"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145516526","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 : 2025-01-01DOI: 10.1016/j.proci.2025.105845
Tobias Guivarch , Hugo Samson , Jérôme Bonnety , Jessy Elias , Sébastien Ducruix , Clément Mirat , Christopher Betrancourt , Guilhem Dezanneau , Ronan Vicquelin
Achieving the European net-zero greenhouse gas emissions target requires the development of sustainable combustion processes across various industrial sectors. These promising alternatives introduce new challenges, such as modifying wall heat transfer. Accurate surface temperature measurements are essential for understanding these effects. Laser-Induced Phosphorescence (LIP) provides a semi-invasive method that exploits the temperature-dependent phosphorescence spectra of thermographic phosphors. YAG:Dy is a thermographic phosphor that emits a phosphorescence signal over the range of 300 K to 2000 K. However, its poor sensitivity with the intensity ratio method and its low sensitivity at lower temperatures with the lifetime method limit its use to high-temperature combustion applications. Additionally, its sensitivity to ambient oxygen reduces the accuracy of those methods. This study evaluates the performance of the Full-Spectrum Fitting (FSF) method, developed by the EM2C Laboratory in Lechner et al. (2022), when applied to YAG:Dy. The method leverages the phosphor’s spectral temperature dependence over a wide range (303 to 1773 K), achieving an accuracy of 0.3 K and a precision of 8.4 K under given experimental conditions. It is observed that there is a laser fluence threshold above which temperature determination using the FSF method becomes independent of laser fluence. The impact of YAG:Dy’s sensitivity to oxygen concentration on temperature measurement is quantified. In the worst case, uncertainty in oxygen concentration can introduce a temperature error ranging from 7 to 19 K. Guidelines are provided to help mitigate these sensitivities in combustion applications.
{"title":"Full-spectrum fitting method applied to YAG:Dy : Impact of oxygen content and laser fluence on wall-temperature phosphor thermometry for combustion","authors":"Tobias Guivarch , Hugo Samson , Jérôme Bonnety , Jessy Elias , Sébastien Ducruix , Clément Mirat , Christopher Betrancourt , Guilhem Dezanneau , Ronan Vicquelin","doi":"10.1016/j.proci.2025.105845","DOIUrl":"10.1016/j.proci.2025.105845","url":null,"abstract":"<div><div>Achieving the European net-zero greenhouse gas emissions target requires the development of sustainable combustion processes across various industrial sectors. These promising alternatives introduce new challenges, such as modifying wall heat transfer. Accurate surface temperature measurements are essential for understanding these effects. Laser-Induced Phosphorescence (LIP) provides a semi-invasive method that exploits the temperature-dependent phosphorescence spectra of thermographic phosphors. YAG:Dy is a thermographic phosphor that emits a phosphorescence signal over the range of 300 K to 2000 K. However, its poor sensitivity with the intensity ratio method and its low sensitivity at lower temperatures with the lifetime method limit its use to high-temperature combustion applications. Additionally, its sensitivity to ambient oxygen reduces the accuracy of those methods. This study evaluates the performance of the Full-Spectrum Fitting (FSF) method, developed by the EM2C Laboratory in Lechner et al. (2022), when applied to YAG:Dy. The method leverages the phosphor’s spectral temperature dependence over a wide range (303 to 1773 K), achieving an accuracy of 0.3 K and a precision of 8.4 K under given experimental conditions. It is observed that there is a laser fluence threshold above which temperature determination using the FSF method becomes independent of laser fluence. The impact of YAG:Dy’s sensitivity to oxygen concentration on temperature measurement is quantified. In the worst case, uncertainty in oxygen concentration can introduce a temperature error ranging from 7 to 19 K. Guidelines are provided to help mitigate these sensitivities in combustion applications.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105845"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145154442","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 : 2025-01-01DOI: 10.1016/j.proci.2025.105944
Hu Meng , Yuhao Nie , Junqing Chen , Yun Huang , Yihua Ren
Surface-disordered TiO2 nanoparticles exhibiting various colors including grey, yellow, blue, and black have attracted considerable attention owing to their outstanding photocatalytic activity, attributed to their narrow bandgap and thus enhanced absorption of solar energy. In this study, we have successfully synthesized TiO2 nanoparticles with tailored surface-disorder structures using a well-controlled H2/O2/N2 premixed Bunsen flame supported by multi-element diffusion flames in a single step. To systematically examine the influence of gas composition on surface-disorder layer formation, we designed four distinct flame conditions maintaining consistent flame structures, adiabatic temperatures, and precursor concentrations while varying the atmospheric composition. In-situ OH-planar laser induced fluorescence (PLIF), spontaneous Raman scattering (SRS), and 2D phase-selective laser-induced breakdown spectroscopy (PS-LIBS) has been employed to characterize the flame structures, temperature profiles, atmospheric conditions, and particle volume fraction across all flame conditions. The in-situ diagnostic results verify that the designed flame conditions have identical particle formation and growth route in flames but with varying gas-particle interactions under different post-flame atmospheres. Ex-situ characterization through high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) of the synthesized nanoparticles demonstrates that TiO2 nanoparticles with surface disorder structure and rutile phase are more preferentially formed under reducing atmospheric condition. Furthermore, both ex-situ UV-Vis spectra and in-situ PS-LIBS indicated that a higher H2 mole fraction in the post-flame region can enhance the light absorption of the synthesized nanoparticles attributed their stronger surface disorder structures.
{"title":"Single-step flame synthesis of surface-disordered titania nanoparticles in Hencken-supported hydrogen premixed flames","authors":"Hu Meng , Yuhao Nie , Junqing Chen , Yun Huang , Yihua Ren","doi":"10.1016/j.proci.2025.105944","DOIUrl":"10.1016/j.proci.2025.105944","url":null,"abstract":"<div><div>Surface-disordered TiO<sub>2</sub> nanoparticles exhibiting various colors including grey, yellow, blue, and black have attracted considerable attention owing to their outstanding photocatalytic activity, attributed to their narrow bandgap and thus enhanced absorption of solar energy. In this study, we have successfully synthesized TiO<sub>2</sub> nanoparticles with tailored surface-disorder structures using a well-controlled H<sub>2</sub>/O<sub>2</sub>/N<sub>2</sub> premixed Bunsen flame supported by multi-element diffusion flames in a single step. To systematically examine the influence of gas composition on surface-disorder layer formation, we designed four distinct flame conditions maintaining consistent flame structures, adiabatic temperatures, and precursor concentrations while varying the atmospheric composition. <em>In-situ</em> OH-planar laser induced fluorescence (PLIF), spontaneous Raman scattering (SRS), and 2D phase-selective laser-induced breakdown spectroscopy (PS-LIBS) has been employed to characterize the flame structures, temperature profiles, atmospheric conditions, and particle volume fraction across all flame conditions. The <em>in-situ</em> diagnostic results verify that the designed flame conditions have identical particle formation and growth route in flames but with varying gas-particle interactions under different post-flame atmospheres. <em>Ex-situ</em> characterization through high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) of the synthesized nanoparticles demonstrates that TiO<sub>2</sub> nanoparticles with surface disorder structure and rutile phase are more preferentially formed under reducing atmospheric condition. Furthermore, both <em>ex-situ</em> UV-Vis spectra and <em>in-situ</em> PS-LIBS indicated that a higher H<sub>2</sub> mole fraction in the post-flame region can enhance the light absorption of the synthesized nanoparticles attributed their stronger surface disorder structures.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105944"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145319675","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 : 2025-01-01DOI: 10.1016/j.proci.2025.105868
G.S. Russell , T.L. Howarth , A.W. Skiba , C.D. Carter , A.J. Aspden
Turbulence is known to exaggerate the thermodiffusive response in lean premixed hydrogen flames. The mean local flame speed has been demonstrated to increase with Karlovitz number, but the range of validity has not been established; furthermore, several studies observed a decrease in turbulent/local flame speed at moderately-high Karlovitz numbers. All of the aforementioned DNS studies were conducted in the canonical flame-in-a-box (FIAB) configuration. To investigate these observations further and to establish whether similar behaviour is observed in realistic configurations, six DNS have been conducted to reproduce a laboratory piloted jet flame. The jet internal diameter was 7.04 mm, with bulk inflow velocities from 6 m/s to 192 m/s (increasing in factors of 2), corresponding to jet Reynolds numbers of 2,500 to 80,000; the reactants had an equivalence ratio of 0.32 at atmospheric conditions. Complementary turbulent FIAB simulations are used to compare the realistic configuration with the canonical abstraction. The mean local flame speed is found to peak in the 48 m/s case, after which a decrease is observed; the transition is found to occur at slightly higher Karlovitz number in the FIAB configuration. A key difference between the two configurations is shown to be that the jet flames are effectively unconfined, whereas the turbulent FIAB area confined by the periodic boundary conditions (so there is a limit on how much flame surface area can be generated in a given volume). Finally, at the highest inflow speed, the jet flame appears to become lifted (there is a significant region near the inlet with little-to-no heat release), and turbulence-flame interaction is shown to be distinctly different to that at lower Karlovitz numbers; the thermodiffusive response is suppressed without the flame becoming fully distributed.
{"title":"Turbulence-flame interactions in high-Karlovitz-number lean premixed hydrogen piloted jet flames","authors":"G.S. Russell , T.L. Howarth , A.W. Skiba , C.D. Carter , A.J. Aspden","doi":"10.1016/j.proci.2025.105868","DOIUrl":"10.1016/j.proci.2025.105868","url":null,"abstract":"<div><div>Turbulence is known to exaggerate the thermodiffusive response in lean premixed hydrogen flames. The mean local flame speed has been demonstrated to increase with Karlovitz number, but the range of validity has not been established; furthermore, several studies observed a decrease in turbulent/local flame speed at moderately-high Karlovitz numbers. All of the aforementioned DNS studies were conducted in the canonical flame-in-a-box (FIAB) configuration. To investigate these observations further and to establish whether similar behaviour is observed in realistic configurations, six DNS have been conducted to reproduce a laboratory piloted jet flame. The jet internal diameter was 7.04<!--> <!-->mm, with bulk inflow velocities from 6<!--> <!-->m/s to 192<!--> <!-->m/s (increasing in factors of 2), corresponding to jet Reynolds numbers of 2,500 to 80,000; the reactants had an equivalence ratio of <span><math><mi>φ</mi></math></span> <!--> <span><math><mo>=</mo></math></span> <!--> <!-->0.32 at atmospheric conditions. Complementary turbulent FIAB simulations are used to compare the realistic configuration with the canonical abstraction. The mean local flame speed is found to peak in the 48<!--> <!-->m/s case, after which a decrease is observed; the transition is found to occur at slightly higher Karlovitz number in the FIAB configuration. A key difference between the two configurations is shown to be that the jet flames are effectively unconfined, whereas the turbulent FIAB area confined by the periodic boundary conditions (so there is a limit on how much flame surface area can be generated in a given volume). Finally, at the highest inflow speed, the jet flame appears to become lifted (there is a significant region near the inlet with little-to-no heat release), and turbulence-flame interaction is shown to be distinctly different to that at lower Karlovitz numbers; the thermodiffusive response is suppressed without the flame becoming fully distributed.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105868"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262369","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 : 2025-01-01DOI: 10.1016/j.proci.2025.105800
Yi Yan, Nicolas S.B. Jaeger, R. Mitchell Spearrin
Improved understanding of hydrogen fluoride (HF) emissions from lithium-ion battery fires, including the temporal dynamics, is needed to optimize fire response and protection. Due to the high polarity of HF and its associated surface adsorption and reactivity, most traditional sensing methods are prone to error and slow response due to issues with sampling or surface interactions. To address these limitations, an in situ tunable diode laser absorption spectrometer is developed to achieve real-time measurements of HF emissions during dynamic battery fires with a temporal resolution of milliseconds, and with detection limits of single parts per million along with several orders of magnitude of dynamic range. The laser spectrometer is used in situ to perform measurements near the fire source so that the fire dynamics and the transient behavior of HF emissions can be more accurately characterized. Thermal runaway and fire/explosion conditions of model 18650 lithium-ion batteries are simulated in a conical radiative heater, and HF measurements are performed online via an optical access port in the effluent exhaust. By varying the radiative heating flux of the conical heater and the initial state of charge of the batteries, different characteristics of the safety venting and thermal runaway behavior of lithium-ion batteries and the corresponding emissions of toxic HF gas are measured. These findings provide valuable insights into the dynamics of lithium-ion battery fires and will aid in the development of strategies to mitigate their associated risks.
{"title":"Hydrogen fluoride emissions from lithium-ion batteries during induced thermal runaway via in situ laser spectroscopy","authors":"Yi Yan, Nicolas S.B. Jaeger, R. Mitchell Spearrin","doi":"10.1016/j.proci.2025.105800","DOIUrl":"10.1016/j.proci.2025.105800","url":null,"abstract":"<div><div>Improved understanding of hydrogen fluoride (HF) emissions from lithium-ion battery fires, including the temporal dynamics, is needed to optimize fire response and protection. Due to the high polarity of HF and its associated surface adsorption and reactivity, most traditional sensing methods are prone to error and slow response due to issues with sampling or surface interactions. To address these limitations, an in situ tunable diode laser absorption spectrometer is developed to achieve real-time measurements of HF emissions during dynamic battery fires with a temporal resolution of milliseconds, and with detection limits of single parts per million along with several orders of magnitude of dynamic range. The laser spectrometer is used in situ to perform measurements near the fire source so that the fire dynamics and the transient behavior of HF emissions can be more accurately characterized. Thermal runaway and fire/explosion conditions of model 18650 lithium-ion batteries are simulated in a conical radiative heater, and HF measurements are performed online via an optical access port in the effluent exhaust. By varying the radiative heating flux of the conical heater and the initial state of charge of the batteries, different characteristics of the safety venting and thermal runaway behavior of lithium-ion batteries and the corresponding emissions of toxic HF gas are measured. These findings provide valuable insights into the dynamics of lithium-ion battery fires and will aid in the development of strategies to mitigate their associated risks.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105800"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144860419","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}