Pub Date : 2023-02-10DOI: 10.1080/13647830.2023.2174046
P. Rajamanickam, J. Daou
Direct interactions between the flow field and the chemical reaction in premixed flames occur when the reaction zone thickness is comparable to, or greater than flow length scales. To study such interactions, a laminar model is considered that has direct bearings to steadily propagating deflagrations in a Hele-Shaw channel with a background plane Poiseuille flow. The study employs asymptotic analyses, pertaining to large activation energy and lubrication theories and considers a distinguished limit where the channel width is comparable to the reaction zone thickness, with account being taken of thermal-expansion and heat-loss effects. The reaction zone structure and burning rates depend on three parameters, namely, the Peclet number, , the Lewis number, and the ratio of channel half-width to reaction zone thickness, . In particular, when the parameter is small wherein the reaction zone is thick, transport processes are found to be controlled by Taylor's dispersion mechanism and an explicit formula for the effective burning speed is obtained. The formula indicates that for , which interestingly coincides with a recent experimental prediction of the turbulent flame speed in a highly turbulent jet flame. The results suggest that the role played by differential diffusion effects is significant both in the laminar and turbulent cases. The reason for the peculiar dependence can be attributed, at least in our laminar model, to Taylor dispersion. Presumably, this dependence may be attributed to a similar but more general mechanism in the turbulent distributed reaction zone regime, rather than to diffusive-thermal curvature effects. The latter effects play however an important role in determining the effective propagation speed for thinner reaction zones, in particular, when is large in our model. It is found that the magnitude of heat losses at extinction, which directly affects the mixture flammability limits, is multiplied by a factor in comparison with those corresponding to the no-flow case in narrow channels.
{"title":"A thick reaction zone model for premixed flames in two-dimensional channels","authors":"P. Rajamanickam, J. Daou","doi":"10.1080/13647830.2023.2174046","DOIUrl":"https://doi.org/10.1080/13647830.2023.2174046","url":null,"abstract":"Direct interactions between the flow field and the chemical reaction in premixed flames occur when the reaction zone thickness is comparable to, or greater than flow length scales. To study such interactions, a laminar model is considered that has direct bearings to steadily propagating deflagrations in a Hele-Shaw channel with a background plane Poiseuille flow. The study employs asymptotic analyses, pertaining to large activation energy and lubrication theories and considers a distinguished limit where the channel width is comparable to the reaction zone thickness, with account being taken of thermal-expansion and heat-loss effects. The reaction zone structure and burning rates depend on three parameters, namely, the Peclet number, , the Lewis number, and the ratio of channel half-width to reaction zone thickness, . In particular, when the parameter is small wherein the reaction zone is thick, transport processes are found to be controlled by Taylor's dispersion mechanism and an explicit formula for the effective burning speed is obtained. The formula indicates that for , which interestingly coincides with a recent experimental prediction of the turbulent flame speed in a highly turbulent jet flame. The results suggest that the role played by differential diffusion effects is significant both in the laminar and turbulent cases. The reason for the peculiar dependence can be attributed, at least in our laminar model, to Taylor dispersion. Presumably, this dependence may be attributed to a similar but more general mechanism in the turbulent distributed reaction zone regime, rather than to diffusive-thermal curvature effects. The latter effects play however an important role in determining the effective propagation speed for thinner reaction zones, in particular, when is large in our model. It is found that the magnitude of heat losses at extinction, which directly affects the mixture flammability limits, is multiplied by a factor in comparison with those corresponding to the no-flow case in narrow channels.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2023-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46994718","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 : 2023-02-08DOI: 10.1080/13647830.2023.2174451
E. A. Cutillo, Gianmarco Petito, K. Bizon, G. Continillo
In this work, a model-order reduction methodology based on proper orthogonal decomposition (POD) and Galërkin projection is presented and applied to the simulation of the self-ignition of a stockpile of solid fuel. Self-ignition is a phenomenon associated with steep changes in space and time, yielding high gradients of state variables which demand grid refinement and, thus, increase of the computational burden. To cope with this difficulty, first, a full order model (FOM), generated by finite-difference discretisation of the PDEs constituting the differential model, is employed to generate reference solutions. Two different POD-based formulations are proposed: the classical POD-Galërkin is employed to generate reduced order models (ROM), then discrete empirical interpolation method (DEIM) is employed to deal with nonlinearities in a more efficient manner. These reduction techniques are further supplemented with an innovative sampling approach based on k-means clustering. The resulting agile ROM is validated against the FOM. Both model-order reduction strategies, particularly the POD-DEIM model, reproduce the FOM solutions with high accuracy and much lower computational cost: The results of the application of a combination of the DEIM algorithm and k-means clustering show that the computational time for the calculation of one solution reduces up to 1020 times, while remaining able to reproduce all bifurcation points found with the FOM, thus demonstrating quantitative and qualitative agreement.
{"title":"Analysis of an innovative sampling strategy based on k-means clustering algorithm for POD and POD-DEIM reduced order models of a 2-D reaction-diffusion system","authors":"E. A. Cutillo, Gianmarco Petito, K. Bizon, G. Continillo","doi":"10.1080/13647830.2023.2174451","DOIUrl":"https://doi.org/10.1080/13647830.2023.2174451","url":null,"abstract":"In this work, a model-order reduction methodology based on proper orthogonal decomposition (POD) and Galërkin projection is presented and applied to the simulation of the self-ignition of a stockpile of solid fuel. Self-ignition is a phenomenon associated with steep changes in space and time, yielding high gradients of state variables which demand grid refinement and, thus, increase of the computational burden. To cope with this difficulty, first, a full order model (FOM), generated by finite-difference discretisation of the PDEs constituting the differential model, is employed to generate reference solutions. Two different POD-based formulations are proposed: the classical POD-Galërkin is employed to generate reduced order models (ROM), then discrete empirical interpolation method (DEIM) is employed to deal with nonlinearities in a more efficient manner. These reduction techniques are further supplemented with an innovative sampling approach based on k-means clustering. The resulting agile ROM is validated against the FOM. Both model-order reduction strategies, particularly the POD-DEIM model, reproduce the FOM solutions with high accuracy and much lower computational cost: The results of the application of a combination of the DEIM algorithm and k-means clustering show that the computational time for the calculation of one solution reduces up to 1020 times, while remaining able to reproduce all bifurcation points found with the FOM, thus demonstrating quantitative and qualitative agreement.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2023-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46915190","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 : 2023-02-02DOI: 10.1080/13647830.2023.2169636
Saeedeh Hamoudi, A. Mirvakili, A. Jamekhorshid, Mohamad Gholipour
In this work, Computational Fluid Dynamic (CFD) is applied to compare the performance of an industrial reformer furnace in four cases. The first and tenth years of operation are two cases with different emissivity factors and fuel components. The results are validated with industrial data and with other CFD simulation typical plants reported in the SMR literature. The results show that a 10% increase in fuel consumption in the tenth year cannot compensate for all temperature drop in skin tubes, and there is still a 14 K temperature drop, leading to a 5% decrease in hydrogen production in tubes. This is due to the different fuel components of the tenth year compared to the first year. To examine the effect of fuel change more closely, the third case is defined with the fuel components of the tenth year and the emissivity factor of the first year. The comparison of this case with others shows that fuel components have a high effect on system performance. The major reason for efficiency reduction between the first and tenth years correlates to a 50% decline in the wall surface emissivity factor. Finally, in the fourth case, applying a ceramic coating with a high emissivity factor is considered via the CFD model for the reformer in the tenth year. This change leads to an increase of about 19 K in tube temperature in the tenth year, which is 3 K more than that in the first year. It can be concluded that the ceramic coating application in the wall of the refractory of the reformer can reduce 14% fuel consumption and enhance hydrogen production.
{"title":"Simulation and performance improvement of an industrial steam methane reformer: depreciation and ceramic coating effects","authors":"Saeedeh Hamoudi, A. Mirvakili, A. Jamekhorshid, Mohamad Gholipour","doi":"10.1080/13647830.2023.2169636","DOIUrl":"https://doi.org/10.1080/13647830.2023.2169636","url":null,"abstract":"In this work, Computational Fluid Dynamic (CFD) is applied to compare the performance of an industrial reformer furnace in four cases. The first and tenth years of operation are two cases with different emissivity factors and fuel components. The results are validated with industrial data and with other CFD simulation typical plants reported in the SMR literature. The results show that a 10% increase in fuel consumption in the tenth year cannot compensate for all temperature drop in skin tubes, and there is still a 14 K temperature drop, leading to a 5% decrease in hydrogen production in tubes. This is due to the different fuel components of the tenth year compared to the first year. To examine the effect of fuel change more closely, the third case is defined with the fuel components of the tenth year and the emissivity factor of the first year. The comparison of this case with others shows that fuel components have a high effect on system performance. The major reason for efficiency reduction between the first and tenth years correlates to a 50% decline in the wall surface emissivity factor. Finally, in the fourth case, applying a ceramic coating with a high emissivity factor is considered via the CFD model for the reformer in the tenth year. This change leads to an increase of about 19 K in tube temperature in the tenth year, which is 3 K more than that in the first year. It can be concluded that the ceramic coating application in the wall of the refractory of the reformer can reduce 14% fuel consumption and enhance hydrogen production.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2023-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45428193","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}
The uncertainties existing in the parameters of chemical kinetic models have a non-negligible influence on the model predictions. It is necessary to conduct a quantitative uncertainty analysis to explore the influence of each parameter on chemical mechanism predictions. To comprehensively consider the effect of the uncertainties of reaction rate parameters, thermodynamic parameters, and transport parameters on model predictions, local sensitivity analysis, local-sensitivity-based uncertainty analysis (LSUA), and random-sampling high dimensional model representation (RS-HDMR) method were coupled to investigate the uncertainty propagation of the chemical kinetic parameters to the calculated laminar flame speed of dimethyl ether under a wide range of conditions using a detailed mechanism. First, the uncertainty analysis was conducted using the local sensitivity analysis and the LSUA method under a wide range of operating conditions to identify the important operating conditions and chemical kinetic parameters. It is found that the prediction uncertainty of laminar flame speed is more obvious under the conditions of high dilution ratio, high pressure, and large equivalence ratio than that under other conditions. According to the results of LSUA, the prediction uncertainty is mainly from the reaction rate coefficients and thermodynamic data. Then, the uncertainty propagation from the significant parameters to the calculated laminar flame speed under important conditions was analysed using the RS-HDMR method. To reduce the huge computational cost of the RS-HDMR method, the backpropagation artificial neural network was employed. The RS-HDMR results indicate that the reaction H + O2 = O + OH has the highest sensitivity coefficient under the whole investigated conditions, which is different from the results using the LSUA method. The non-linear relationship between the rate coefficient and the predicted laminar flame speed is responsible for the discrepancy. Furthermore, it is found that the sensitivity coefficient of the input parameters strongly depends on the operating conditions.
化学动力学模型参数中存在的不确定性对模型预测有着不可忽略的影响。有必要进行定量的不确定性分析，以探索每个参数对化学机理预测的影响。为了综合考虑反应速率参数、热力学参数和输运参数的不确定性对模型预测的影响，进行了局部灵敏度分析、基于局部灵敏度的不确定性分析（LSUA），和随机采样高维模型表示（RS-HDMR）方法相结合，利用详细的机制研究了化学动力学参数在宽范围条件下对计算的二甲醚层流火焰速度的不确定性传播。首先，在广泛的操作条件下，使用局部灵敏度分析和LSUA方法进行不确定性分析，以确定重要的操作条件和化学动力学参数。研究发现，在高稀释比、高压和大当量比条件下，层流火焰速度的预测不确定性比其他条件下更明显。根据LSUA的结果，预测的不确定性主要来自反应速率系数和热力学数据。然后，使用RS-HDMR方法分析了重要条件下从重要参数到计算层流火焰速度的不确定性传播。为了降低RS-HDMR方法的巨大计算成本，采用了反向传播人工神经网络。RS-HDMR结果表明反应H + 氧气 = O + OH在整个研究条件下具有最高的灵敏度系数，这与使用LSUA方法的结果不同。速率系数和预测的层流火焰速度之间的非线性关系是造成这种差异的原因。此外，还发现输入参数的灵敏度系数与操作条件密切相关。
{"title":"Comprehensive influence of uncertainty propagation of chemical kinetic parameters on laminar flame speed prediction: a case study of dimethyl ether","authors":"Yachao Chang, Pengzhi Wang, Shuai Huang, Xu Han, Ming-lei Jia","doi":"10.1080/13647830.2023.2169637","DOIUrl":"https://doi.org/10.1080/13647830.2023.2169637","url":null,"abstract":"The uncertainties existing in the parameters of chemical kinetic models have a non-negligible influence on the model predictions. It is necessary to conduct a quantitative uncertainty analysis to explore the influence of each parameter on chemical mechanism predictions. To comprehensively consider the effect of the uncertainties of reaction rate parameters, thermodynamic parameters, and transport parameters on model predictions, local sensitivity analysis, local-sensitivity-based uncertainty analysis (LSUA), and random-sampling high dimensional model representation (RS-HDMR) method were coupled to investigate the uncertainty propagation of the chemical kinetic parameters to the calculated laminar flame speed of dimethyl ether under a wide range of conditions using a detailed mechanism. First, the uncertainty analysis was conducted using the local sensitivity analysis and the LSUA method under a wide range of operating conditions to identify the important operating conditions and chemical kinetic parameters. It is found that the prediction uncertainty of laminar flame speed is more obvious under the conditions of high dilution ratio, high pressure, and large equivalence ratio than that under other conditions. According to the results of LSUA, the prediction uncertainty is mainly from the reaction rate coefficients and thermodynamic data. Then, the uncertainty propagation from the significant parameters to the calculated laminar flame speed under important conditions was analysed using the RS-HDMR method. To reduce the huge computational cost of the RS-HDMR method, the backpropagation artificial neural network was employed. The RS-HDMR results indicate that the reaction H + O2 = O + OH has the highest sensitivity coefficient under the whole investigated conditions, which is different from the results using the LSUA method. The non-linear relationship between the rate coefficient and the predicted laminar flame speed is responsible for the discrepancy. Furthermore, it is found that the sensitivity coefficient of the input parameters strongly depends on the operating conditions.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43665867","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 : 2023-01-31DOI: 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":null,"pages":null},"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":null,"pages":null},"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":null,"pages":null},"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":null,"pages":null},"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":null,"pages":null},"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: 10.1080/13647830.2023.2165966
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":null,"pages":null},"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}
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