Pub Date : 2024-09-04DOI: 10.1016/j.proci.2024.105542
Aaron W. Skiba, Campbell D. Carter, Stephen D. Hammack, James F. Driscoll
This study reports measurements of two-dimensional (2D) local displacement speeds ( ▪ ), curvature ( ▪ ), and tangential strain rate ( ▪ ) extracted from premixed flames subjected to turbulent Karlovitz and Reynolds numbers ranging from 2.1–23 and 1500–3500, respectively. Such measurements were facilitated through joint implementation of OH PLIF and stereoscopic PIV at 20kHz. Deriving these quantities from OH-PLIF-based flame edges permitted, to our knowledge, the first experimental assessment of their statistical correlations. Namely, joint PDFs (JPDFs) and conditional mean (CM) profiles of ▪ and ▪ indicate that ▪ tends to decrease as the magnitude of ▪ increases. JPDFs and CM profiles of ▪ and ▪ exhibit a strong negative correlation and demonstrate that density weighted values of ▪ ( ▪ , where and represent the density within the reactants and at the iso-contours selected to define the flame front, respectively) exceed three times the un-stretched laminar flame speed () when ▪0. Global averages of ▪ extracted near the bases of flames were 20%–30% less than ; yet, such values increased with axial distance (). These findings are all consistent with prior direct numerical simulation (DNS) studies, particularly those of burner-stabilized flames. Beyond enabling correlations of the aforementioned quantities, the employed diagnostics, coupled with a unique flame-edge-point tracking algorithm, enabled statistical assessment of their temporal evolution. Specifically, deriving a normalized time (01) based on when two flame-edge-points merged allowed assessment of quantities conditioned on the flame-edge-points proceeding that merger. Such analysis revealed that, on average, the lives of flame-edge-points fall into two epochs: (1) for 0.8, ▪ slowly decreases as increases and ▪; and (2) when 0.8, ▪ sharply increases to values exceeding and there is a marked rise in the decay rate of ▪ . These trends are consistent with recent DNS studies and support implementing a -based -model capable of predicting its extreme characteristics as flame-edge-points approach annihilation.
{"title":"On local displacement speeds, their correlations with flame-front quantities, and their temporal evolution measured in turbulent premixed flames","authors":"Aaron W. Skiba, Campbell D. Carter, Stephen D. Hammack, James F. Driscoll","doi":"10.1016/j.proci.2024.105542","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105542","url":null,"abstract":"This study reports measurements of two-dimensional (2D) local displacement speeds ( ▪ ), curvature ( ▪ ), and tangential strain rate ( ▪ ) extracted from premixed flames subjected to turbulent Karlovitz and Reynolds numbers ranging from 2.1–23 and 1500–3500, respectively. Such measurements were facilitated through joint implementation of OH PLIF and stereoscopic PIV at 20kHz. Deriving these quantities from OH-PLIF-based flame edges permitted, to our knowledge, the first experimental assessment of their statistical correlations. Namely, joint PDFs (JPDFs) and conditional mean (CM) profiles of ▪ and ▪ indicate that ▪ tends to decrease as the magnitude of ▪ increases. JPDFs and CM profiles of ▪ and ▪ exhibit a strong negative correlation and demonstrate that density weighted values of ▪ ( ▪ , where and represent the density within the reactants and at the iso-contours selected to define the flame front, respectively) exceed three times the un-stretched laminar flame speed () when ▪0. Global averages of ▪ extracted near the bases of flames were 20%–30% less than ; yet, such values increased with axial distance (). These findings are all consistent with prior direct numerical simulation (DNS) studies, particularly those of burner-stabilized flames. Beyond enabling correlations of the aforementioned quantities, the employed diagnostics, coupled with a unique flame-edge-point tracking algorithm, enabled statistical assessment of their temporal evolution. Specifically, deriving a normalized time (01) based on when two flame-edge-points merged allowed assessment of quantities conditioned on the flame-edge-points proceeding that merger. Such analysis revealed that, on average, the lives of flame-edge-points fall into two epochs: (1) for 0.8, ▪ slowly decreases as increases and ▪; and (2) when 0.8, ▪ sharply increases to values exceeding and there is a marked rise in the decay rate of ▪ . These trends are consistent with recent DNS studies and support implementing a -based -model capable of predicting its extreme characteristics as flame-edge-points approach annihilation.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"62 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223748","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 : 2024-09-04DOI: 10.1016/j.proci.2024.105763
Oussama Chaib, Simone Hochgreb, Isaac Boxx
The structure of hydrogen-enriched methane-air flames in a Bunsen burner at low turbulence is investigated using OH planar laser-induced fluorescence (PLIF). Three flames are investigated at identical unstretched laminar flame speeds and turbulence conditions, while hydrogen enrichment is varied up to 70% by volume. An increase in global flame consumption speed is recorded with hydrogen addition, and is attributed to both an increase in flame surface area and fluctuations in stoichiometry along the flame surface as a result of differential diffusion. These fluctuations are found to be well-captured by the gradient of OH-PLIF intensity along the flame front and it is hence identified as a promising experimentally-accessible marker of thermo-diffusive instability. Its correlation with curvature is hereby examined for the first time experimentally. No correlations are found in absence of hydrogen, while increasingly positive correlations are recorded with hydrogen enrichment, consistent with the behavior of local fuel consumption in direct numerical simulations (DNS) of lean hydrogen-air flames. This highlights the potential of OH intensity gradient magnitudes as a marker of thermo-diffusive instability, and a potential surrogate for local fuel consumption speed which is inaccessible experimentally.
{"title":"An experimental marker of thermo-diffusive instability in hydrogen-enriched flames","authors":"Oussama Chaib, Simone Hochgreb, Isaac Boxx","doi":"10.1016/j.proci.2024.105763","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105763","url":null,"abstract":"The structure of hydrogen-enriched methane-air flames in a Bunsen burner at low turbulence is investigated using OH planar laser-induced fluorescence (PLIF). Three flames are investigated at identical unstretched laminar flame speeds and turbulence conditions, while hydrogen enrichment is varied up to 70% by volume. An increase in global flame consumption speed is recorded with hydrogen addition, and is attributed to both an increase in flame surface area and fluctuations in stoichiometry along the flame surface as a result of differential diffusion. These fluctuations are found to be well-captured by the gradient of OH-PLIF intensity along the flame front and it is hence identified as a promising experimentally-accessible marker of thermo-diffusive instability. Its correlation with curvature is hereby examined for the first time experimentally. No correlations are found in absence of hydrogen, while increasingly positive correlations are recorded with hydrogen enrichment, consistent with the behavior of local fuel consumption in direct numerical simulations (DNS) of lean hydrogen-air flames. This highlights the potential of OH intensity gradient magnitudes as a marker of thermo-diffusive instability, and a potential surrogate for local fuel consumption speed which is inaccessible experimentally.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"84 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142180284","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 : 2024-09-03DOI: 10.1016/j.proci.2024.105737
Mingming Gu, Ziqiao Chang, Aman Satija, Shengming Yin, Shaojie Wang, Fei Qi, Robert P. Lucht
We presented a theoretical model designed to account for collisional line-mixing (LM) effects in order to provide an accurate characterization of femtosecond (fs) coherent anti-Stokes Raman scattering (CARS) spectroscopy for CO under high-temperature and high-pressure conditions. Numerical simulations revealed that the closely spaced rotational transitions within each CO vibrational manifold induced significant collisional line-mixing. This phenomenon led to a narrowing of the bandwidth of the entire vibrational manifold, partially offsetting the collisional broadening effects. Theoretical derivations further suggested that, for a relatively short probe delay (4-9 ps), a high-pressure CO chirped probe pulse (CPP) fs CARS spectrum could be precisely modeled by utilizing transition information extracted from atmospheric pressures. This proposition was substantiated through experimental measurements conducted in an atmospheric-pressure laminar flame over a temperature range of 300-1922 K, as well as in a high-pressure and high-temperature gas cell (HPHTC) at pressures up to 69 atm and preset temperatures reaching 805 K. The results indicated that CO CPP fs CARS held promise as an ideal diagnostic tool for high-pressure environments.
我们提出了一个旨在考虑碰撞线混合（LM）效应的理论模型，以准确描述一氧化碳在高温高压条件下的飞秒（fs）相干反斯托克斯拉曼散射（CARS）光谱。数值模拟显示，每个一氧化碳振动流形内紧密间隔的旋转跃迁会诱发显著的碰撞线混合。这种现象导致整个振动歧管的带宽变窄，部分抵消了碰撞展宽效应。理论推导进一步表明，对于相对较短的探针延迟（4-9 ps），高压 CO chirped probe pulse (CPP) fs CARS 光谱可以利用从大气压力中提取的过渡信息进行精确建模。在温度范围为 300-1922 K 的常压层流火焰中，以及在压力高达 69 atm 和预设温度达到 805 K 的高压高温气室 (HPHTC) 中进行的实验测量证实了这一观点。
{"title":"Theoretical and experimental characterization of CO2 CPP fs CARS for high-temperature and high-pressure diagnostics","authors":"Mingming Gu, Ziqiao Chang, Aman Satija, Shengming Yin, Shaojie Wang, Fei Qi, Robert P. Lucht","doi":"10.1016/j.proci.2024.105737","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105737","url":null,"abstract":"We presented a theoretical model designed to account for collisional line-mixing (LM) effects in order to provide an accurate characterization of femtosecond (fs) coherent anti-Stokes Raman scattering (CARS) spectroscopy for CO under high-temperature and high-pressure conditions. Numerical simulations revealed that the closely spaced rotational transitions within each CO vibrational manifold induced significant collisional line-mixing. This phenomenon led to a narrowing of the bandwidth of the entire vibrational manifold, partially offsetting the collisional broadening effects. Theoretical derivations further suggested that, for a relatively short probe delay (4-9 ps), a high-pressure CO chirped probe pulse (CPP) fs CARS spectrum could be precisely modeled by utilizing transition information extracted from atmospheric pressures. This proposition was substantiated through experimental measurements conducted in an atmospheric-pressure laminar flame over a temperature range of 300-1922 K, as well as in a high-pressure and high-temperature gas cell (HPHTC) at pressures up to 69 atm and preset temperatures reaching 805 K. The results indicated that CO CPP fs CARS held promise as an ideal diagnostic tool for high-pressure environments.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"306 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223752","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 : 2024-09-03DOI: 10.1016/j.proci.2024.105733
Mhanna Mhanna, Mohamed Sy, Ali Elkhazraji, Aamir Farooq
Chemical kinetic experiments of fuel oxidation/pyrolysis are quite complicated with a multitude of species being formed and consumed. It is desirable to have a diagnostic strategy that can detect many species simultaneously with high sensitivity, selectivity, and fast time response. In this work, cavity-enhanced absorption spectroscopy (CEAS) and deep neural network (DNN) are exploited for selective and simultaneous multi-species detection in high-temperature shock-tube experiments. As a representative case, time-histories of major products of propylbenzene pyrolysis are measured behind reflected shock waves at T 950–1300 K and P 1 atm. A distributed feedback inter-band cascade (ICL) laser emitting near is used as the laser source. Laser wavelength tuning over 3038.6–3039.8 cm and denoising models based on DNN are employed to differentiate the broadband absorbance spectra of benzene, toluene, ethylbenzene, ethylene, styrene and propylbenzene. The models are able to clean noisy absorbance spectra and split these into contributions from reference species by multidimensional linear regression (MLR). Off-axis CEAS is implemented to improve sensitivity to weak absorbers by amplifying effective laser path-length. To the best of our knowledge, this work reports the first successful implementation of time-resolved multispecies detection with a single narrow wavelength-tuning laser and CEAS configuration. This work also represents the first study of simultaneous measurement of multiple species during propylbenzene pyrolysis using laser absorption spectroscopy.
{"title":"Multi-speciation in shock tube kinetics using deep neural networks and cavity-enhanced absorption spectroscopy","authors":"Mhanna Mhanna, Mohamed Sy, Ali Elkhazraji, Aamir Farooq","doi":"10.1016/j.proci.2024.105733","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105733","url":null,"abstract":"Chemical kinetic experiments of fuel oxidation/pyrolysis are quite complicated with a multitude of species being formed and consumed. It is desirable to have a diagnostic strategy that can detect many species simultaneously with high sensitivity, selectivity, and fast time response. In this work, cavity-enhanced absorption spectroscopy (CEAS) and deep neural network (DNN) are exploited for selective and simultaneous multi-species detection in high-temperature shock-tube experiments. As a representative case, time-histories of major products of propylbenzene pyrolysis are measured behind reflected shock waves at T 950–1300 K and P 1 atm. A distributed feedback inter-band cascade (ICL) laser emitting near is used as the laser source. Laser wavelength tuning over 3038.6–3039.8 cm and denoising models based on DNN are employed to differentiate the broadband absorbance spectra of benzene, toluene, ethylbenzene, ethylene, styrene and propylbenzene. The models are able to clean noisy absorbance spectra and split these into contributions from reference species by multidimensional linear regression (MLR). Off-axis CEAS is implemented to improve sensitivity to weak absorbers by amplifying effective laser path-length. To the best of our knowledge, this work reports the first successful implementation of time-resolved multispecies detection with a single narrow wavelength-tuning laser and CEAS configuration. This work also represents the first study of simultaneous measurement of multiple species during propylbenzene pyrolysis using laser absorption spectroscopy.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"384 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142180286","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 : 2024-09-02DOI: 10.1016/j.proci.2024.105739
Tong Su, Boyan Xu, Rob J.M. Bastiaans, Nicholas A. Worth
The lean blow-off (LBO) behaviour of turbulent premixed bluff-body stabilized flames was investigated. Fuels with a range of Lewis numbers were used to examine differential diffusion characteristics, including NH/H/N (70%/22.5%/7.5% by volume), CH and CH. Simultaneous OH-PLIF and PIV were employed to study flame structure changes as the flames approach LBO, and quantify curvature and hydrodynamic strain rates along the flame surface. Large Eddy Simulation (LES) was also conducted to quantify the consumption rates of each fuel at some time before and during the blow-off transient. At moderate inlet velocities the ammonia blended flames are more resilient to LBO in comparison with the methane and propane flames. The flame structure of the ammonia blended flames is much more fragmented than the hydrocarbon flames, even relatively far from LBO, with a higher intensity heat release rate distribution close to the flame base. Higher positive flame curvatures were observed in the ammonia blended flames, which is likely to contribute to the strong anchoring of these flames even in regions of high strain close to the flame base. The consumption rate for these flames is shown to increase locally near the flame base when approaching LBO. Furthermore, the lower strain rates experienced on the surface of NH/H/N flame compared with the other two flames may also delay blow-off. The CH-air flames feature more spatial regions along the shear layers with predominantly negative curvature, which can also enhance the reaction due to the Lewis number of these flames exceeding unity. However in these flames the consumption rate decreases locally in the highly strained regions when ramping to LBO, potentially contributing to their lower relative LBO resilience. For CH-air flames, the curvature, hydrodynamic strain rates and consumption rates do not change much when ramping to LBO, which offer no input to modify the LBO.
{"title":"The behaviour of NH[formula omitted]/H[formula omitted]/N[formula omitted], CH[formula omitted] and C[formula omitted]H[formula omitted] turbulent premixed bluff-body stabilized flames near lean blow-off","authors":"Tong Su, Boyan Xu, Rob J.M. Bastiaans, Nicholas A. Worth","doi":"10.1016/j.proci.2024.105739","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105739","url":null,"abstract":"The lean blow-off (LBO) behaviour of turbulent premixed bluff-body stabilized flames was investigated. Fuels with a range of Lewis numbers were used to examine differential diffusion characteristics, including NH/H/N (70%/22.5%/7.5% by volume), CH and CH. Simultaneous OH-PLIF and PIV were employed to study flame structure changes as the flames approach LBO, and quantify curvature and hydrodynamic strain rates along the flame surface. Large Eddy Simulation (LES) was also conducted to quantify the consumption rates of each fuel at some time before and during the blow-off transient. At moderate inlet velocities the ammonia blended flames are more resilient to LBO in comparison with the methane and propane flames. The flame structure of the ammonia blended flames is much more fragmented than the hydrocarbon flames, even relatively far from LBO, with a higher intensity heat release rate distribution close to the flame base. Higher positive flame curvatures were observed in the ammonia blended flames, which is likely to contribute to the strong anchoring of these flames even in regions of high strain close to the flame base. The consumption rate for these flames is shown to increase locally near the flame base when approaching LBO. Furthermore, the lower strain rates experienced on the surface of NH/H/N flame compared with the other two flames may also delay blow-off. The CH-air flames feature more spatial regions along the shear layers with predominantly negative curvature, which can also enhance the reaction due to the Lewis number of these flames exceeding unity. However in these flames the consumption rate decreases locally in the highly strained regions when ramping to LBO, potentially contributing to their lower relative LBO resilience. For CH-air flames, the curvature, hydrodynamic strain rates and consumption rates do not change much when ramping to LBO, which offer no input to modify the LBO.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"7 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142180313","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 : 2024-09-02DOI: 10.1016/j.proci.2024.105503
Yuto Matsuura, Ayana Banno, Masato Mikami
Since ammonia is a carbon neutral fuel, it is expected to be widely utilized in the near future. Although there have been many researches on ammonia combustion, no research has been conducted on ammonia droplet combustion, which is a fundamental research on spray combustion, because ammonia is in a gaseous state at room temperature and atmospheric pressure. This study investigated the combustion characteristics of single ammonia droplets in microgravity for the first time. Single ammonia droplets were formed in high pressure air and were successfully ignited in microgravity. In an early stage of burning, the droplet vaporized with an almost constant vaporization rate of 0.87–1.0 mm/s. After such a quasi-steady period, the vaporization rate decreased over time. In accordance with the decrease in the vaporization rate, the flame standoff ratio also decreased over time. After that, the droplet exhibited unique phenomena such as droplet disruption, puffing, or droplet re-expansion although the fuel was initially pure. These types of unique behavior are caused by the diffusion of water vapor, a combustion product, to the droplet surface, and dissolution and accumulation of water on the droplet surface. Since water has a lower volatility than ammonia, the concentration of dissolved water at the droplet surface increases rapidly as the droplet diameter decreases. As a result, the vaporization of ammonia is suppressed and the flame standoff ratio decreases. Additionally, as the water concentration at the droplet surface increases, the boiling point at the droplet surface also increases, resulting in superheating of the liquid ammonia and homogeneous bubble nucleation. The growth of bubbles caused droplet disruption, puffing, and droplet re-expansion.
{"title":"Single ammonia droplet combustion in a high-pressure environment in microgravity","authors":"Yuto Matsuura, Ayana Banno, Masato Mikami","doi":"10.1016/j.proci.2024.105503","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105503","url":null,"abstract":"Since ammonia is a carbon neutral fuel, it is expected to be widely utilized in the near future. Although there have been many researches on ammonia combustion, no research has been conducted on ammonia droplet combustion, which is a fundamental research on spray combustion, because ammonia is in a gaseous state at room temperature and atmospheric pressure. This study investigated the combustion characteristics of single ammonia droplets in microgravity for the first time. Single ammonia droplets were formed in high pressure air and were successfully ignited in microgravity. In an early stage of burning, the droplet vaporized with an almost constant vaporization rate of 0.87–1.0 mm/s. After such a quasi-steady period, the vaporization rate decreased over time. In accordance with the decrease in the vaporization rate, the flame standoff ratio also decreased over time. After that, the droplet exhibited unique phenomena such as droplet disruption, puffing, or droplet re-expansion although the fuel was initially pure. These types of unique behavior are caused by the diffusion of water vapor, a combustion product, to the droplet surface, and dissolution and accumulation of water on the droplet surface. Since water has a lower volatility than ammonia, the concentration of dissolved water at the droplet surface increases rapidly as the droplet diameter decreases. As a result, the vaporization of ammonia is suppressed and the flame standoff ratio decreases. Additionally, as the water concentration at the droplet surface increases, the boiling point at the droplet surface also increases, resulting in superheating of the liquid ammonia and homogeneous bubble nucleation. The growth of bubbles caused droplet disruption, puffing, and droplet re-expansion.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142180317","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 : 2024-09-02DOI: 10.1016/j.proci.2024.105606
Caleb Van Beck, Venkat Raman
Flow behavior was investigated in an RDE using Lagrangian Particle Tracking coupled with high-fidelity Eulerian simulations. The case considered utilized the AFRL Radial Air Inlet design under stoichiometric hydrogen–air conditions at a specified mass flow rate, with a single wave observed in the system. Particle properties were recorded throughout the simulation to compare to Eulerian data as well as to examine the effect of particle injection location on resulting flow behavior. The Lagrangian description of the flow closely resembled the Eulerian description in terms of capturing the detonation wave front properly, but axial velocities between the two descriptions varied significantly due to the moving particles increasing the average recorded velocities within the flow. Injection location was examined based on three conditions, namely starting injection locations 5° ahead of the detonation wave, 5° behind, and 180° ahead. Results showed differing behavior in the 180° condition, wherein a pressure rise was seen further axially into the chamber from detonation wave contact. Particle data was also viewed from a thermodynamic cycle standpoint and compared against an ideal detonative process from a reduced-order cycle deck model. Each injection condition studied failed to fully represent the ideal detonative process, despite showing similar overall trends between enthalpy and entropy, with the highest peak enthalpy coming within 23.75% of the ideal enthalpy in the 180° condition. Heat release behavior aided in understanding deflagrative losses incurred in certain injection conditions. An optimal injection location of 26° ahead of the wave was determined based on maximum pressure rise, which also failed to produce fully ideal thermodynamic behavior. Overall, this analysis shows the value of examining RDE flow from a Lagrangian perspective, given the insight it yields into how fluid interacts with flow structures inside complex RDE systems and how this translates to thermodynamic space for comparison to ideal behavior.
{"title":"Lagrangian-conditioned statistics of detonation propagation in a realistic rotating detonation engine","authors":"Caleb Van Beck, Venkat Raman","doi":"10.1016/j.proci.2024.105606","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105606","url":null,"abstract":"Flow behavior was investigated in an RDE using Lagrangian Particle Tracking coupled with high-fidelity Eulerian simulations. The case considered utilized the AFRL Radial Air Inlet design under stoichiometric hydrogen–air conditions at a specified mass flow rate, with a single wave observed in the system. Particle properties were recorded throughout the simulation to compare to Eulerian data as well as to examine the effect of particle injection location on resulting flow behavior. The Lagrangian description of the flow closely resembled the Eulerian description in terms of capturing the detonation wave front properly, but axial velocities between the two descriptions varied significantly due to the moving particles increasing the average recorded velocities within the flow. Injection location was examined based on three conditions, namely starting injection locations 5° ahead of the detonation wave, 5° behind, and 180° ahead. Results showed differing behavior in the 180° condition, wherein a pressure rise was seen further axially into the chamber from detonation wave contact. Particle data was also viewed from a thermodynamic cycle standpoint and compared against an ideal detonative process from a reduced-order cycle deck model. Each injection condition studied failed to fully represent the ideal detonative process, despite showing similar overall trends between enthalpy and entropy, with the highest peak enthalpy coming within 23.75% of the ideal enthalpy in the 180° condition. Heat release behavior aided in understanding deflagrative losses incurred in certain injection conditions. An optimal injection location of 26° ahead of the wave was determined based on maximum pressure rise, which also failed to produce fully ideal thermodynamic behavior. Overall, this analysis shows the value of examining RDE flow from a Lagrangian perspective, given the insight it yields into how fluid interacts with flow structures inside complex RDE systems and how this translates to thermodynamic space for comparison to ideal behavior.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"31 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142180315","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 : 2024-09-02DOI: 10.1016/j.proci.2024.105725
Hugo Pers, Thierry Poinsot, Thierry Schuller
The -hybridization of premixed methane-air flames stabilized above perforated plates is hindered by the flashback tendency of hydrogen-rich flames. This study investigates the role of flame quenching by heat losses to the burner wall on flashback mechanisms. A set of canonical multi-perforated plates with various sub-millimeter slit widths is studied experimentally. Depending on the slit width and operating conditions, two regimes of hydrodynamic flashback initiation are identified. The first is solely controlled by the kinematic imbalance between flow and flame speed downstream of the flame-holder. The second is governed by the ratio of the slit width over a quenching distance that depends on the temperature of the preheated reactants. A method that allows to determine the quenching width at any preheat temperature for a given plate geometry and operating condition is presented. This approach enables to differentiate the two hydrodynamic flashback regimes. A map of flame stabilization and flashback regimes depending on the slit width and -hybridization rate is proposed based on the experiments. The controlling mechanisms leading to a specific regime of flashback for a given operating condition are unveiled. Flame quenching is found to inhibit the influence of the Lewis number on flashback limits in narrow slits. This prevents the abrupt increase in the ratio of bulk flow velocity to laminar flame speed at flashback, a phenomenon observed in larger slits when the effective Lewis number falls below . These results establish the role of quenching in flashback phenomena and may support the design of hydrogen-robust perforated burners.
{"title":"Effect of quenching on flashback of hydrogen-enriched laminar premixed flames","authors":"Hugo Pers, Thierry Poinsot, Thierry Schuller","doi":"10.1016/j.proci.2024.105725","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105725","url":null,"abstract":"The -hybridization of premixed methane-air flames stabilized above perforated plates is hindered by the flashback tendency of hydrogen-rich flames. This study investigates the role of flame quenching by heat losses to the burner wall on flashback mechanisms. A set of canonical multi-perforated plates with various sub-millimeter slit widths is studied experimentally. Depending on the slit width and operating conditions, two regimes of hydrodynamic flashback initiation are identified. The first is solely controlled by the kinematic imbalance between flow and flame speed downstream of the flame-holder. The second is governed by the ratio of the slit width over a quenching distance that depends on the temperature of the preheated reactants. A method that allows to determine the quenching width at any preheat temperature for a given plate geometry and operating condition is presented. This approach enables to differentiate the two hydrodynamic flashback regimes. A map of flame stabilization and flashback regimes depending on the slit width and -hybridization rate is proposed based on the experiments. The controlling mechanisms leading to a specific regime of flashback for a given operating condition are unveiled. Flame quenching is found to inhibit the influence of the Lewis number on flashback limits in narrow slits. This prevents the abrupt increase in the ratio of bulk flow velocity to laminar flame speed at flashback, a phenomenon observed in larger slits when the effective Lewis number falls below . These results establish the role of quenching in flashback phenomena and may support the design of hydrogen-robust perforated burners.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"21 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142180318","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 : 2024-09-02DOI: 10.1016/j.proci.2024.105744
Ethan S. Genter, Jackson B. Kennedy, Cinnamon Sipper, Amitesh S. Jayaraman, Nicholas Montes, Hai Wang
The influence of gasdynamic and chemical kinetic properties on cellular detonation structure is experimentally investigated through CH-O, CH-O, and H-O detonations with different diluents and O addition. Eight hydrocarbon mixtures are designed to independently vary the detonation gas dynamic effect, characterized by the post-shock mixture specific heat ratio , and the chemistry effect, characterized by the effective activation energy . A statistical representation of the cellular regularity is proposed to quantify the degree of geometric irregularity. For the range of considered, under a constant , cell regularity is found to have no clear dependence on . However, under a constant , cell irregularity is found to increase significantly with increasing , generalizing the findings of previous studies on H-O cell regularity. A scaling argument based on local kinetic sensitivity is proposed to describe the effect of on cell regularity. The scaling result is found to be in good agreement with experimental data.
{"title":"Regularity of detonation cellular structures in hydrocarbon mixtures of moderate effective activation energies","authors":"Ethan S. Genter, Jackson B. Kennedy, Cinnamon Sipper, Amitesh S. Jayaraman, Nicholas Montes, Hai Wang","doi":"10.1016/j.proci.2024.105744","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105744","url":null,"abstract":"The influence of gasdynamic and chemical kinetic properties on cellular detonation structure is experimentally investigated through CH-O, CH-O, and H-O detonations with different diluents and O addition. Eight hydrocarbon mixtures are designed to independently vary the detonation gas dynamic effect, characterized by the post-shock mixture specific heat ratio , and the chemistry effect, characterized by the effective activation energy . A statistical representation of the cellular regularity is proposed to quantify the degree of geometric irregularity. For the range of considered, under a constant , cell regularity is found to have no clear dependence on . However, under a constant , cell irregularity is found to increase significantly with increasing , generalizing the findings of previous studies on H-O cell regularity. A scaling argument based on local kinetic sensitivity is proposed to describe the effect of on cell regularity. The scaling result is found to be in good agreement with experimental data.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"111 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142180285","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 : 2024-09-02DOI: 10.1016/j.proci.2024.105755
Dwi M.J. Purnomo, Yiren Qin, Maria Theodori, Maryam Zamanialaei, Chris Lautenberger, Arnaud Trouvé, Michael Gollner
Wildland fires in the wildland–urban interface (WUI) threaten urban structures. Effective landscape management relies on predictive tools that incorporate information on structural attributes and fire incident intensity to quantify the risks. Current computational models often fall short, either focusing solely on wildland fire spread or neglecting critical fire spread pathways in the WUI, including direct flame contact (DFC), radiation, and firebrands. To address this gap, we conducted a computational study to investigate WUI fire spread, encompassing both urban and wildland landscapes while accounting for all three primary fire spread pathways. We developed a two-dimensional landscape-scale model for urban fire spread and integrated it with an operational model for wildland fires, employing semi-physical level set approaches in both cases. We used the model to simulate the Tubbs and Thomas Fires, historical WUI fires in the United States. Our model’s predictions achieved an accuracy exceeding 85% for fire perimeters and around 70% for the damaged houses, with over 30% of the houses ignited by firebrands. For the first time, our model spatially quantified the fire intensity of the events in terms of incident heat flux maps. In the Tubbs Fire, this ranged from 30 to 50 kW/m (DFC) and 5 to 25 kW/m (radiation), while it is 80 to 130 kW/m (DFC) and 10 to 40 kW/m (radiation) in the Thomas Fire. These values closely align with large-scale experiments on structure-to-structure fire spread. Despite limitations in the model, such as the nonuniformity of structural properties, our findings underscore its potential to provide a range of outputs for various applications. The model addresses a critical need for integrating wildland and urban fire spread processes and offers insight into primary mechanisms for fire spread. This work provides promising tools for simulating WUI fires and can aid in the development of strategies to mitigate them.
{"title":"Reconstructing modes of destruction in wildland–urban interface fires using a semi-physical level-set model","authors":"Dwi M.J. Purnomo, Yiren Qin, Maria Theodori, Maryam Zamanialaei, Chris Lautenberger, Arnaud Trouvé, Michael Gollner","doi":"10.1016/j.proci.2024.105755","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105755","url":null,"abstract":"Wildland fires in the wildland–urban interface (WUI) threaten urban structures. Effective landscape management relies on predictive tools that incorporate information on structural attributes and fire incident intensity to quantify the risks. Current computational models often fall short, either focusing solely on wildland fire spread or neglecting critical fire spread pathways in the WUI, including direct flame contact (DFC), radiation, and firebrands. To address this gap, we conducted a computational study to investigate WUI fire spread, encompassing both urban and wildland landscapes while accounting for all three primary fire spread pathways. We developed a two-dimensional landscape-scale model for urban fire spread and integrated it with an operational model for wildland fires, employing semi-physical level set approaches in both cases. We used the model to simulate the Tubbs and Thomas Fires, historical WUI fires in the United States. Our model’s predictions achieved an accuracy exceeding 85% for fire perimeters and around 70% for the damaged houses, with over 30% of the houses ignited by firebrands. For the first time, our model spatially quantified the fire intensity of the events in terms of incident heat flux maps. In the Tubbs Fire, this ranged from 30 to 50 kW/m (DFC) and 5 to 25 kW/m (radiation), while it is 80 to 130 kW/m (DFC) and 10 to 40 kW/m (radiation) in the Thomas Fire. These values closely align with large-scale experiments on structure-to-structure fire spread. Despite limitations in the model, such as the nonuniformity of structural properties, our findings underscore its potential to provide a range of outputs for various applications. The model addresses a critical need for integrating wildland and urban fire spread processes and offers insight into primary mechanisms for fire spread. This work provides promising tools for simulating WUI fires and can aid in the development of strategies to mitigate them.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"2010 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142180314","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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