Pub Date : 2023-01-31DOI: 10.1080/13647830.2023.2171905
Huahua Xiao, Xiaoxi Li
Flame acceleration and deflagration-to-detonation transition (DDT) in obstructed channels is an important subject of research for propulsion and explosion safety. Experiment and numerical simulation of DDT in a stoichiometric hydrogen–oxygen mixture in a channel equipped with continuous triangular obstacles were conducted in this work. In the experiment, high-speed schlieren photography was used to record the evolution of reaction front and strong pressure waves. A pressure transducer was used to record the pressure build-up. In the numerical simulation, a high-order numerical method was used to solve the fully compressible reactive Navier–Stokes equations coupled with a calibrated chemical-diffusive model. The calculations are in good agreement with experimental observations. The result shows that the triangular obstacles can significantly promote flame acceleration and provide conditions for the occurrence of DDT. In the early stages of flame acceleration, the main cause for flame roll-up and distortion is the effect of vortices generated in the gaps between neighbouring triangular obstacles. The scales and velocities of vortices are determined by the positive feedback process between combustion-generated flow and flame propagation. The continuous triangular obstacles create an intricate flow field and increase the complexity of shock reflections. This complicated flow leads to local detonation initiation through different mechanisms, i.e. flame-flame collisions and flame-shock interactions. Successive local detonation ignitions and failures are produced in the obstacle gaps due to the continuous layout of the triangular obstacles. It was found that successive local detonation ignitions are critical for the eventual success of DDT formation because the shock waves generated by them continually strengthen the leading shock. The detonation failure or survival due to diffraction depends on the height of the narrow space (h*) between the bulk flame and obstacle vertex, and can be quantitatively characterised by the ratio of the space height to detonation cell size ( ), h*/ .
{"title":"Experimental and numerical study of flame acceleration and DDT in a channel with continuous obstacles","authors":"Huahua Xiao, Xiaoxi Li","doi":"10.1080/13647830.2023.2171905","DOIUrl":"https://doi.org/10.1080/13647830.2023.2171905","url":null,"abstract":"Flame acceleration and deflagration-to-detonation transition (DDT) in obstructed channels is an important subject of research for propulsion and explosion safety. Experiment and numerical simulation of DDT in a stoichiometric hydrogen–oxygen mixture in a channel equipped with continuous triangular obstacles were conducted in this work. In the experiment, high-speed schlieren photography was used to record the evolution of reaction front and strong pressure waves. A pressure transducer was used to record the pressure build-up. In the numerical simulation, a high-order numerical method was used to solve the fully compressible reactive Navier–Stokes equations coupled with a calibrated chemical-diffusive model. The calculations are in good agreement with experimental observations. The result shows that the triangular obstacles can significantly promote flame acceleration and provide conditions for the occurrence of DDT. In the early stages of flame acceleration, the main cause for flame roll-up and distortion is the effect of vortices generated in the gaps between neighbouring triangular obstacles. The scales and velocities of vortices are determined by the positive feedback process between combustion-generated flow and flame propagation. The continuous triangular obstacles create an intricate flow field and increase the complexity of shock reflections. This complicated flow leads to local detonation initiation through different mechanisms, i.e. flame-flame collisions and flame-shock interactions. Successive local detonation ignitions and failures are produced in the obstacle gaps due to the continuous layout of the triangular obstacles. It was found that successive local detonation ignitions are critical for the eventual success of DDT formation because the shock waves generated by them continually strengthen the leading shock. The detonation failure or survival due to diffraction depends on the height of the narrow space (h*) between the bulk flame and obstacle vertex, and can be quantitatively characterised by the ratio of the space height to detonation cell size ( ), h*/ .","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"27 1","pages":"459 - 486"},"PeriodicalIF":1.3,"publicationDate":"2023-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49165148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2023-01-30DOI: 10.1080/13647830.2023.2169635
G. Saccone, P. Breda, P. Natale, F. Battista
CFD simulations of turbulent reacting flows based on finite rate chemistry often employ reduced kinetic mechanisms to decrease the computational cost, especially if the combustion of hydrocarbons is involved. This work presents a chemical-kinetic methodology, consisting of the formulation, development, testing and validation of a reduced, skeletal mechanism targeted to the Liquid Rocket Engines (LRE) combustion of CH4/O2. The reduced mechanism is generated for combustion processes involving medium-high pressures and ignition of undiluted methane-oxygen, using the 0D/1D open-source software Cantera. The presented mechanism, named Medium Pressure Rocket Burn (MPRB), is achieved from a semi-detailed kinetic scheme, i.e. Lu30, derived from the detailed mechanism GRI-Mech 3.0. Identification of the main chemical reaction paths and sensitivity analysis applied in a sequence leading to a final scheme consisting of 19 species and 51 reactions. Promising results are obtained in terms of ignition delay times and comparison with experimental measurements in high-pressure shock tube tests. The validation is extended to the turbulent case using a sub-scale single-injector combustion chamber with a gaseous injection of CH4/O2 as a benchmark. First, Improved Delayed Detached Eddy Simulations (IDDES) based on a non-adiabatic flamelet database are in good agreement with the available experimental data, although the average thermal load foreseen by MPRB is about 12.6% higher than the case with Lu30 used as reference. Secondly, RANS simulations based on the Eddy Dissipation Concept (EDC) show that accurate results can be obtained with an affordable computational cost, compared to the previously investigated detailed chemistry calculations. Overall the successful validation of the presented reduced mechanism encourages its use for CH4/O2 combustion regimes within this range of applicability.
{"title":"Reduced kinetic mechanism for methane/oxygen rocket engine applications: a reliable and numerically efficient methodology","authors":"G. Saccone, P. Breda, P. Natale, F. Battista","doi":"10.1080/13647830.2023.2169635","DOIUrl":"https://doi.org/10.1080/13647830.2023.2169635","url":null,"abstract":"CFD simulations of turbulent reacting flows based on finite rate chemistry often employ reduced kinetic mechanisms to decrease the computational cost, especially if the combustion of hydrocarbons is involved. This work presents a chemical-kinetic methodology, consisting of the formulation, development, testing and validation of a reduced, skeletal mechanism targeted to the Liquid Rocket Engines (LRE) combustion of CH4/O2. The reduced mechanism is generated for combustion processes involving medium-high pressures and ignition of undiluted methane-oxygen, using the 0D/1D open-source software Cantera. The presented mechanism, named Medium Pressure Rocket Burn (MPRB), is achieved from a semi-detailed kinetic scheme, i.e. Lu30, derived from the detailed mechanism GRI-Mech 3.0. Identification of the main chemical reaction paths and sensitivity analysis applied in a sequence leading to a final scheme consisting of 19 species and 51 reactions. Promising results are obtained in terms of ignition delay times and comparison with experimental measurements in high-pressure shock tube tests. The validation is extended to the turbulent case using a sub-scale single-injector combustion chamber with a gaseous injection of CH4/O2 as a benchmark. First, Improved Delayed Detached Eddy Simulations (IDDES) based on a non-adiabatic flamelet database are in good agreement with the available experimental data, although the average thermal load foreseen by MPRB is about 12.6% higher than the case with Lu30 used as reference. Secondly, RANS simulations based on the Eddy Dissipation Concept (EDC) show that accurate results can be obtained with an affordable computational cost, compared to the previously investigated detailed chemistry calculations. Overall the successful validation of the presented reduced mechanism encourages its use for CH4/O2 combustion regimes within this range of applicability.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"27 1","pages":"391 - 417"},"PeriodicalIF":1.3,"publicationDate":"2023-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48340110","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2023-01-30DOI: 10.1080/13647830.2023.2165968
K. Matsue, M. Matalon
The dynamics of hydrodynamically unstable premixed flames are studied using the nonlinear Michelson–Sivashinsky (MS) equation, modified appropriately to incorporate effects due to gravity. The problem depends on two parameters: the Markstein number that characterises the combustible mixture and its diffusion properties, and the gravitational parameter that represents the ratio of buoyancy to inertial forces. A comprehensive portrait of all possible equilibrium solutions are obtained for a wide range of parameters, using a continuation methodology adopted from bifurcation theory. The results heighten the distinction between upward and downward propagation. In the absence of gravity, the nonlinear development always leads to stationary solutions, namely, cellular flames propagating at a constant speed without change in shape. When decreasing the Markstein number, a modest growth in amplitude is observed with the propagation speed reaching an upper bound. For upward propagation, the equilibrium states are also stationary solutions, but their spatial structure depends on the initial conditions leading to their development. The combined Darrieus–Landau and Rayleigh–Taylor instabilities create profiles of invariably larger amplitudes and sharper crests that propagate at an increasingly faster speed when reducing the Markstein number. For downward propagation, the equilibrium states consist in addition to stationary structures time-periodic solutions, namely, pulsating flames propagating at a constant average speed. The stabilising influence of gravity dampens the nonlinear growth and leads to spatiotemporal changes in flame morphology, such as the formation of multi-crest stationary profiles or pulsating cell splitting and merging patterns, and an overall reduction in propagation speed. The transition between these states occurs at bifurcation and exchange of stability points, which becomes more prominent when reducing the Markstein number and/or increasing the influence of gravity. In addition to the local bifurcation characterisation the global bifurcation structure of the equation, obtained by tracing the continuation of the bifurcation points themselves unravels qualitative features such as the manifestation of bi-stability and hysteresis, and/or the onset and sustenance of time-periodic solutions. Overall, the results exhibit the rich and complex dynamics that occur when gravity, however small, becomes physically meaningful.
{"title":"Dynamics of hydrodynamically unstable premixed flames in a gravitational field – local and global bifurcation structures","authors":"K. Matsue, M. Matalon","doi":"10.1080/13647830.2023.2165968","DOIUrl":"https://doi.org/10.1080/13647830.2023.2165968","url":null,"abstract":"The dynamics of hydrodynamically unstable premixed flames are studied using the nonlinear Michelson–Sivashinsky (MS) equation, modified appropriately to incorporate effects due to gravity. The problem depends on two parameters: the Markstein number that characterises the combustible mixture and its diffusion properties, and the gravitational parameter that represents the ratio of buoyancy to inertial forces. A comprehensive portrait of all possible equilibrium solutions are obtained for a wide range of parameters, using a continuation methodology adopted from bifurcation theory. The results heighten the distinction between upward and downward propagation. In the absence of gravity, the nonlinear development always leads to stationary solutions, namely, cellular flames propagating at a constant speed without change in shape. When decreasing the Markstein number, a modest growth in amplitude is observed with the propagation speed reaching an upper bound. For upward propagation, the equilibrium states are also stationary solutions, but their spatial structure depends on the initial conditions leading to their development. The combined Darrieus–Landau and Rayleigh–Taylor instabilities create profiles of invariably larger amplitudes and sharper crests that propagate at an increasingly faster speed when reducing the Markstein number. For downward propagation, the equilibrium states consist in addition to stationary structures time-periodic solutions, namely, pulsating flames propagating at a constant average speed. The stabilising influence of gravity dampens the nonlinear growth and leads to spatiotemporal changes in flame morphology, such as the formation of multi-crest stationary profiles or pulsating cell splitting and merging patterns, and an overall reduction in propagation speed. The transition between these states occurs at bifurcation and exchange of stability points, which becomes more prominent when reducing the Markstein number and/or increasing the influence of gravity. In addition to the local bifurcation characterisation the global bifurcation structure of the equation, obtained by tracing the continuation of the bifurcation points themselves unravels qualitative features such as the manifestation of bi-stability and hysteresis, and/or the onset and sustenance of time-periodic solutions. Overall, the results exhibit the rich and complex dynamics that occur when gravity, however small, becomes physically meaningful.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"27 1","pages":"346 - 374"},"PeriodicalIF":1.3,"publicationDate":"2023-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44357577","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2023-01-18DOI: 10.1080/13647830.2023.2166428
J. D. De León-Ruiz, I. Carvajal-Mariscal, M. De la Cruz-Ávila, R. Beltrán-Chacón
A computationally-supported experimental procedure to estimate the primary dimensions of diffusion flames, using volume reconstruction from thermal imagery, is presented. The experimental setup uses a 4 × 16.94 mm radial distribution gas-burner, with a 0.8 mm nozzle diameter, a thermal imaging camera and a proprietary image processing algorithm. Flame thermal imagery was captured, using four different fuel loads, 350, 650, 950 and 1200 cc/min, from two different visualisation planes, 0° and 90°. The images were visually and qualitatively processed leaving aside the temperature measurement and favouring instead a non-dimensional temperature gradient, . Corresponding flame front structures were estimated and reconstructed employing computational geometry. The height and diameter magnitudes were measured indirectly through a reference length. The results show that at the flame front structure separates itself from the background noise. Furthermore, when compared against available benchmarks, at and , the resulting flame coincides with the luminous and continuous flame heights, respectively. This approach yields maximum relative error of 36.54% and 18.91% for both compared geometries. When compared to image convolution and spatial density clustering procedures, this approach reduces the maximum error obtained by 47%. Based on this information, the methodology presented is considered suitable for dimensioning diffusion flames, thus, proposed as an estimation tool for the design and manufacturing of gas-fuelled appliances/devices.
{"title":"Flame front reconstruction and volume estimation through computational geometry: a case study on machine vision applied to combustion systems","authors":"J. D. De León-Ruiz, I. Carvajal-Mariscal, M. De la Cruz-Ávila, R. Beltrán-Chacón","doi":"10.1080/13647830.2023.2166428","DOIUrl":"https://doi.org/10.1080/13647830.2023.2166428","url":null,"abstract":"A computationally-supported experimental procedure to estimate the primary dimensions of diffusion flames, using volume reconstruction from thermal imagery, is presented. The experimental setup uses a 4 × 16.94 mm radial distribution gas-burner, with a 0.8 mm nozzle diameter, a thermal imaging camera and a proprietary image processing algorithm. Flame thermal imagery was captured, using four different fuel loads, 350, 650, 950 and 1200 cc/min, from two different visualisation planes, 0° and 90°. The images were visually and qualitatively processed leaving aside the temperature measurement and favouring instead a non-dimensional temperature gradient, . Corresponding flame front structures were estimated and reconstructed employing computational geometry. The height and diameter magnitudes were measured indirectly through a reference length. The results show that at the flame front structure separates itself from the background noise. Furthermore, when compared against available benchmarks, at and , the resulting flame coincides with the luminous and continuous flame heights, respectively. This approach yields maximum relative error of 36.54% and 18.91% for both compared geometries. When compared to image convolution and spatial density clustering procedures, this approach reduces the maximum error obtained by 47%. Based on this information, the methodology presented is considered suitable for dimensioning diffusion flames, thus, proposed as an estimation tool for the design and manufacturing of gas-fuelled appliances/devices.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"27 1","pages":"375 - 390"},"PeriodicalIF":1.3,"publicationDate":"2023-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44006394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2023-01-17DOI: 10.1080/13647830.2023.2165965
N. Kabbaj, H. Im
To provide fundamental insights into the response of laminar flames to alternating current (AC) electric fields, a simplified one-dimensional model using an ionised layer model is formulated with the conservation equations for the ion species with ionisation, recombination, and transport due to molecular diffusion and electric mobility. A parametric study is conducted to investigate the response of the ion layer at different voltages and oscillation frequencies, and the results are examined mainly in terms of the net current–voltage (I–V) characteristics. As the oscillation frequency is increased, a nonmonotonic response in the I–V curve is seen such that the current may exceed the saturation condition corresponding to the steady DC condition. In general the current reaches a peak as the unsteady time scale becomes comparable to the ion transport time scale, which is dictated by the mobility, and eventually becomes attenuated at higher frequencies to behave like a low-pass filter. The extent of the peak current rise and the cut-off frequency are found to depend on the characteristic time scales of the ion chemistry and mobility-induced transport. The simplified model serves as a framework to characterise the behaviour of complex flames in terms of the dominant ionisation and transport processes. The current overshoot behaviour may also imply that the overall effect of the electric field may be further magnified under the AC conditions, motivating further studies of multi-dimensional flames for the ionic wind effects.
{"title":"Response of one-dimensional ionised layer to oscillatory electric fields","authors":"N. Kabbaj, H. Im","doi":"10.1080/13647830.2023.2165965","DOIUrl":"https://doi.org/10.1080/13647830.2023.2165965","url":null,"abstract":"To provide fundamental insights into the response of laminar flames to alternating current (AC) electric fields, a simplified one-dimensional model using an ionised layer model is formulated with the conservation equations for the ion species with ionisation, recombination, and transport due to molecular diffusion and electric mobility. A parametric study is conducted to investigate the response of the ion layer at different voltages and oscillation frequencies, and the results are examined mainly in terms of the net current–voltage (I–V) characteristics. As the oscillation frequency is increased, a nonmonotonic response in the I–V curve is seen such that the current may exceed the saturation condition corresponding to the steady DC condition. In general the current reaches a peak as the unsteady time scale becomes comparable to the ion transport time scale, which is dictated by the mobility, and eventually becomes attenuated at higher frequencies to behave like a low-pass filter. The extent of the peak current rise and the cut-off frequency are found to depend on the characteristic time scales of the ion chemistry and mobility-induced transport. The simplified model serves as a framework to characterise the behaviour of complex flames in terms of the dominant ionisation and transport processes. The current overshoot behaviour may also imply that the overall effect of the electric field may be further magnified under the AC conditions, motivating further studies of multi-dimensional flames for the ionic wind effects.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"27 1","pages":"267 - 289"},"PeriodicalIF":1.3,"publicationDate":"2023-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45741799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2023-01-17DOI: 10.1080/13647830.2023.2165967
Z. Huo, M. Cleary, Kun Wu, A. Masri, Xuejun Fan
Due to the composition-dependent stiffness of chemistry, simulations of reactive turbulent flows may present computational load imbalance among parallel processes when spatial decomposition is used for parallelisation, causing high CPU idle time and waste of computational resources. To increase computational efficiency, a dynamic load balancing (DLB) model is proposed to redistribute computational load among computing cores. The DLB model exploits a decomposition in the mixture fraction space with two dynamic adjusting decomposition strategies to realise load redistribution. The DLB model is suitable for the integration of chemistry on stochastic particles in hybrid Eulerian/Lagrangian turbulent combustion models in which the Eulerian field is conventionally decomposed statically in physical space in a way that balances the computational load for the solution of the Navier-Stokes equation but which does not generally lead to balanced load for the computation of the composition fields. Here it is tested using an OpenFOAM-based platform, mmcFoam, which is a comprehensive object-orientated C++ library for stochastic turbulent combustion modelling. Apart from direct integration (DI) for chemistry, the DLB model is also coupled with dynamic adaptive chemistry (DAC) and in situ adaptive tabulation (ISAT), which allows for extra speedup. The performance of the coupled models is validated and assessed for two laboratory flame conditions that exhibit different levels of computational load imbalance. Overall, the DLB model effectively balances the computational load distribution and increases the effective usage of computing power, shortening the simulation wall time required. Moreover, a strong scaling test is carried out using up to 512 cores. Although all approaches have sub-ideal scalability, the scalability of each with DLB is significantly better than without DLB. While DLB-ISAT has relatively poor scalability compared to the DI- and DAC-based methods, DLB-ISAT still ranks the fastest among the algorithms in all scaling trials.
{"title":"A dynamic load balancing model coupled with DAC and ISAT for a stochastic turbulent combustion model","authors":"Z. Huo, M. Cleary, Kun Wu, A. Masri, Xuejun Fan","doi":"10.1080/13647830.2023.2165967","DOIUrl":"https://doi.org/10.1080/13647830.2023.2165967","url":null,"abstract":"Due to the composition-dependent stiffness of chemistry, simulations of reactive turbulent flows may present computational load imbalance among parallel processes when spatial decomposition is used for parallelisation, causing high CPU idle time and waste of computational resources. To increase computational efficiency, a dynamic load balancing (DLB) model is proposed to redistribute computational load among computing cores. The DLB model exploits a decomposition in the mixture fraction space with two dynamic adjusting decomposition strategies to realise load redistribution. The DLB model is suitable for the integration of chemistry on stochastic particles in hybrid Eulerian/Lagrangian turbulent combustion models in which the Eulerian field is conventionally decomposed statically in physical space in a way that balances the computational load for the solution of the Navier-Stokes equation but which does not generally lead to balanced load for the computation of the composition fields. Here it is tested using an OpenFOAM-based platform, mmcFoam, which is a comprehensive object-orientated C++ library for stochastic turbulent combustion modelling. Apart from direct integration (DI) for chemistry, the DLB model is also coupled with dynamic adaptive chemistry (DAC) and in situ adaptive tabulation (ISAT), which allows for extra speedup. The performance of the coupled models is validated and assessed for two laboratory flame conditions that exhibit different levels of computational load imbalance. Overall, the DLB model effectively balances the computational load distribution and increases the effective usage of computing power, shortening the simulation wall time required. Moreover, a strong scaling test is carried out using up to 512 cores. Although all approaches have sub-ideal scalability, the scalability of each with DLB is significantly better than without DLB. While DLB-ISAT has relatively poor scalability compared to the DI- and DAC-based methods, DLB-ISAT still ranks the fastest among the algorithms in all scaling trials.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"27 1","pages":"317 - 345"},"PeriodicalIF":1.3,"publicationDate":"2023-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48202425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2023-01-17DOI: 10.1080/13647830.2023.2165966
A. Bhattacharya, S. Mondal, S. De, A. Mukhopadhyay, S. Sen
Interactions between a couple of flames often lead to their synchronisation. Flame–flame interaction has recently been linked with thermoacoustic instability in combustors. However, synchronisation caused by the interaction of coupled flames is still not fully understood. Furthermore, the interacting flame oscillators in practical situations often have a slight dissimilarity between them. Here, we systematically study the effects of such dissimilarity on the flame–flame interaction with a simple system consisting of two candle flame oscillators (CFO). The interaction is studied with CFOs having similar and dissimilar amplitudes of oscillations. The distance between the CFOs is parametrically varied. The results indicate that the synchronisation phenomena caused by flame–flame interaction have a complex dependence on the distance between the oscillators. Further, we find the flame–flame interaction to be significantly affected by the dissimilarity of the interacting oscillators. In-phase (IP) synchronisation occurs when the interacting oscillators are separated by a low distance and the oscillators have similar or moderately dissimilar amplitudes of oscillations. On the other hand, for large disparities in the amplitudes of oscillations, lag synchronisation (LS) is observed at a low distance between the CFOs. If the interacting oscillators have similar amplitudes of oscillations, the amplitude death (AD) regime persists throughout the operating range except at a low distance between the CFOs. In contrast, if the interacting oscillators have dissimilar amplitudes of oscillations, different rich dynamical states such as lag synchronisation and partial amplitude death are encountered in addition to amplitude death as the distance between the oscillators is varied. This study might be useful to understand synchronisation due to flame–flame interaction in modern multi-burner turbulent combustors where the constituent burners often have inherent dissimilarities.
{"title":"Synchronisation behaviour between two candle flame oscillators with similar and dissimilar amplitudes of oscillations","authors":"A. Bhattacharya, S. Mondal, S. De, A. Mukhopadhyay, S. Sen","doi":"10.1080/13647830.2023.2165966","DOIUrl":"https://doi.org/10.1080/13647830.2023.2165966","url":null,"abstract":"Interactions between a couple of flames often lead to their synchronisation. Flame–flame interaction has recently been linked with thermoacoustic instability in combustors. However, synchronisation caused by the interaction of coupled flames is still not fully understood. Furthermore, the interacting flame oscillators in practical situations often have a slight dissimilarity between them. Here, we systematically study the effects of such dissimilarity on the flame–flame interaction with a simple system consisting of two candle flame oscillators (CFO). The interaction is studied with CFOs having similar and dissimilar amplitudes of oscillations. The distance between the CFOs is parametrically varied. The results indicate that the synchronisation phenomena caused by flame–flame interaction have a complex dependence on the distance between the oscillators. Further, we find the flame–flame interaction to be significantly affected by the dissimilarity of the interacting oscillators. In-phase (IP) synchronisation occurs when the interacting oscillators are separated by a low distance and the oscillators have similar or moderately dissimilar amplitudes of oscillations. On the other hand, for large disparities in the amplitudes of oscillations, lag synchronisation (LS) is observed at a low distance between the CFOs. If the interacting oscillators have similar amplitudes of oscillations, the amplitude death (AD) regime persists throughout the operating range except at a low distance between the CFOs. In contrast, if the interacting oscillators have dissimilar amplitudes of oscillations, different rich dynamical states such as lag synchronisation and partial amplitude death are encountered in addition to amplitude death as the distance between the oscillators is varied. This study might be useful to understand synchronisation due to flame–flame interaction in modern multi-burner turbulent combustors where the constituent burners often have inherent dissimilarities.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"27 1","pages":"291 - 316"},"PeriodicalIF":1.3,"publicationDate":"2023-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45172628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2023-01-12DOI: 10.1080/13647830.2023.2165454
A. Tyliszczak, A. Wawrzak, K. Wawrzak
This paper presents an analysis of numerical and modelling issues based on a simulation of nitrogen-diluted hydrogen lifted flame evolving in a hot co-flow. We apply the large-eddy simulations (LES) method with the so-called ‘no combustion model’ and concentrate on the impact of chemical mechanisms and various discretisation schemes on the obtained results. The main attention is put to the latter issue in which we analyse to what extent a discretisation method of the convective terms of the scalar equations for the species and enthalpy affects the solutions. We consider eight commonly known total variation diminishing (TVD) schemes and three upwind schemes of the second order. The remaining terms in the scalar equations and all the terms in the Navier–Stokes equations are discretised applying the sixth-order compact difference method. Such an approach makes the discretisation errors of the convective terms the main factor affecting the solutions from the numerical point of view. Prior to the main analysis, the differences caused by the use of various TVD or upwind schemes are highlighted based on a single scalar transport equation with a known analytical solution. The results obtained for the flame are compared to experimental data taken from the literature. It is shown that the differences due to the application of a particular discretisation method are of similar magnitude as the differences between the simulation results and experimental data. Moreover, analysis of the impact of the chemical mechanism showed that observed differences are comparable to these originating from the use of different discretisation methods.
{"title":"Impact of a discretisation method and chemical kinetics on the accuracy of simulation of a lifted hydrogen flame","authors":"A. Tyliszczak, A. Wawrzak, K. Wawrzak","doi":"10.1080/13647830.2023.2165454","DOIUrl":"https://doi.org/10.1080/13647830.2023.2165454","url":null,"abstract":"This paper presents an analysis of numerical and modelling issues based on a simulation of nitrogen-diluted hydrogen lifted flame evolving in a hot co-flow. We apply the large-eddy simulations (LES) method with the so-called ‘no combustion model’ and concentrate on the impact of chemical mechanisms and various discretisation schemes on the obtained results. The main attention is put to the latter issue in which we analyse to what extent a discretisation method of the convective terms of the scalar equations for the species and enthalpy affects the solutions. We consider eight commonly known total variation diminishing (TVD) schemes and three upwind schemes of the second order. The remaining terms in the scalar equations and all the terms in the Navier–Stokes equations are discretised applying the sixth-order compact difference method. Such an approach makes the discretisation errors of the convective terms the main factor affecting the solutions from the numerical point of view. Prior to the main analysis, the differences caused by the use of various TVD or upwind schemes are highlighted based on a single scalar transport equation with a known analytical solution. The results obtained for the flame are compared to experimental data taken from the literature. It is shown that the differences due to the application of a particular discretisation method are of similar magnitude as the differences between the simulation results and experimental data. Moreover, analysis of the impact of the chemical mechanism showed that observed differences are comparable to these originating from the use of different discretisation methods.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"27 1","pages":"244 - 266"},"PeriodicalIF":1.3,"publicationDate":"2023-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48695909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-12-28DOI: 10.1080/13647830.2022.2157753
R. Lamioni, C. Bronzoni, M. Folli, L. Tognotti, C. Galletti
Domestic condensing boilers are equipped with perforated burners ensuring short-length premixed flames issues from a series of circular holes and slits. Despite some efforts that have been devoted to understanding the effect of hole diameter, pattern, and hole-to-hole distance on the resulting flames, very little is known about the flames from a series of slits. In this work 3-dimensional numerical simulations with skeletal kinetic mechanisms are performed to determine the structure of premixed methane-air flames issuing from two-slits patterns, often recurring in practical burner designs, i.e. several equally-spaced slits and a group of four slits. The arrangement of the slits greatly influences the resulting flames. A significant change in the flame behaviour occurs depending on the inlet velocity; at low speeds, the flames issuing from the slits present a flat region, while increasing the speed they assume a conical shape along the slit length. Neighbour flames are distinct from each other at low speeds, while they interact strongly with increasing the velocity. Interestingly, a series of several slits produce a single long wedge-shaped flame, while the group of four slits generates a single conical flame.
{"title":"Effect of slit pattern on the structure of premixed flames issuing from perforated burners in domestic condensing boilers","authors":"R. Lamioni, C. Bronzoni, M. Folli, L. Tognotti, C. Galletti","doi":"10.1080/13647830.2022.2157753","DOIUrl":"https://doi.org/10.1080/13647830.2022.2157753","url":null,"abstract":"Domestic condensing boilers are equipped with perforated burners ensuring short-length premixed flames issues from a series of circular holes and slits. Despite some efforts that have been devoted to understanding the effect of hole diameter, pattern, and hole-to-hole distance on the resulting flames, very little is known about the flames from a series of slits. In this work 3-dimensional numerical simulations with skeletal kinetic mechanisms are performed to determine the structure of premixed methane-air flames issuing from two-slits patterns, often recurring in practical burner designs, i.e. several equally-spaced slits and a group of four slits. The arrangement of the slits greatly influences the resulting flames. A significant change in the flame behaviour occurs depending on the inlet velocity; at low speeds, the flames issuing from the slits present a flat region, while increasing the speed they assume a conical shape along the slit length. Neighbour flames are distinct from each other at low speeds, while they interact strongly with increasing the velocity. Interestingly, a series of several slits produce a single long wedge-shaped flame, while the group of four slits generates a single conical flame.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"27 1","pages":"218 - 243"},"PeriodicalIF":1.3,"publicationDate":"2022-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44021612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-12-22DOI: 10.1080/13647830.2022.2157333
H. S. Mukunda, A. Shiva Kumar, Sachin Payannad, C. S. Bhaskar Dixit
The extensive work on wood crib fires, both experimental and model development over the last six decades is examined in some detail. The wide range of parameters of crib tests and the theories have been reviewed in the literature and a satisfactory correlation has still to emerge from these studies. From early times, the burn flux (g/m s) has been considered the most appropriate parameter to characterise the burn behaviour of the cribs. These data on a re-examination revealed a surprisingly simple behaviour of a linear variation of the mass loss rate (g/s) with the mass of the crib, particularly for smaller size sticks with the crib placed on the ground. Some insight into this behaviour is brought out and the basic idea has been pursued to reveal an alternate and a more accurate correlation for the burn rate with crib mass and the crib size as principal parameters with the crib height-to-spacing ratio providing a minor correction. The resulting correlation has been compared with over a hundred and fifty experimental data along with a modified Thomas correlation and shown to perform much better for smaller-size sticks.
{"title":"Insights into and the evolution of a novel predictive model for free burning wooden cribs","authors":"H. S. Mukunda, A. Shiva Kumar, Sachin Payannad, C. S. Bhaskar Dixit","doi":"10.1080/13647830.2022.2157333","DOIUrl":"https://doi.org/10.1080/13647830.2022.2157333","url":null,"abstract":"The extensive work on wood crib fires, both experimental and model development over the last six decades is examined in some detail. The wide range of parameters of crib tests and the theories have been reviewed in the literature and a satisfactory correlation has still to emerge from these studies. From early times, the burn flux (g/m s) has been considered the most appropriate parameter to characterise the burn behaviour of the cribs. These data on a re-examination revealed a surprisingly simple behaviour of a linear variation of the mass loss rate (g/s) with the mass of the crib, particularly for smaller size sticks with the crib placed on the ground. Some insight into this behaviour is brought out and the basic idea has been pursued to reveal an alternate and a more accurate correlation for the burn rate with crib mass and the crib size as principal parameters with the crib height-to-spacing ratio providing a minor correction. The resulting correlation has been compared with over a hundred and fifty experimental data along with a modified Thomas correlation and shown to perform much better for smaller-size sticks.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"27 1","pages":"198 - 217"},"PeriodicalIF":1.3,"publicationDate":"2022-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48483488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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