Pub Date : 2022-11-28DOI: 10.1080/13647830.2023.2182235
Alex M. Garcia, S. Le Bras, W. Polifke
This study presents a numerical analysis of the impact of hydrogen addition on the consumption speed of premixed lean methane-air laminar flames exposed to combined strain and heat loss. Equivalence ratios of 0.9, 0.7, and 0.5 with fuel mixture composition ranging from pure methane to pure hydrogen are considered to cover a wide range of conditions in the lean region. The 1-D asymmetric counter-flow premixed laminar flame (aCFPF) with heat loss on the product side is considered as a flamelet configuration that represents an elementary unit of a turbulent flame and the consumption speed is used to characterise the effect of strain and heat loss. Due to the ambiguity in the definition of the consumption speed of multi-component mixtures, two definitions are compared. The first definition is based on a weighted combination of the consumption rate of the fuel species and the second one is based in the global heat release rate. The definition of the consumption speed based on the heat release results in lower values of the stretched flame speed and even an opposite response to strain rate for some methane-hydrogen-air mixtures compared to the definition based on the fuel consumption. Strain rate leads to an increase of the flame speed for the lean methane-hydrogen mixtures, reaching a maximum value after which the flame speed decreases with strain rate. Heat loss decreases the stretched flame speed and leads to a sooner extinction of the flamelet due to combined strain and heat loss. Hydrogen addition and equivalence ratio significantly impact the maximum consumption speed and the flame response to combined strain rate and heat loss. The effect of hydrogen on the thermo-diffusive properties of the mixture, characterised by the Zeldovich number and the effective Lewis number, are also analyzed and related to the effect on the consumption speed. Two definitions of the Lewis number of the multi-component fuel mixture are evaluated against the results from the aCFPF.
{"title":"Effect of hydrogen addition on the consumption speed of lean premixed laminar methane flames exposed to combined strain and heat loss","authors":"Alex M. Garcia, S. Le Bras, W. Polifke","doi":"10.1080/13647830.2023.2182235","DOIUrl":"https://doi.org/10.1080/13647830.2023.2182235","url":null,"abstract":"This study presents a numerical analysis of the impact of hydrogen addition on the consumption speed of premixed lean methane-air laminar flames exposed to combined strain and heat loss. Equivalence ratios of 0.9, 0.7, and 0.5 with fuel mixture composition ranging from pure methane to pure hydrogen are considered to cover a wide range of conditions in the lean region. The 1-D asymmetric counter-flow premixed laminar flame (aCFPF) with heat loss on the product side is considered as a flamelet configuration that represents an elementary unit of a turbulent flame and the consumption speed is used to characterise the effect of strain and heat loss. Due to the ambiguity in the definition of the consumption speed of multi-component mixtures, two definitions are compared. The first definition is based on a weighted combination of the consumption rate of the fuel species and the second one is based in the global heat release rate. The definition of the consumption speed based on the heat release results in lower values of the stretched flame speed and even an opposite response to strain rate for some methane-hydrogen-air mixtures compared to the definition based on the fuel consumption. Strain rate leads to an increase of the flame speed for the lean methane-hydrogen mixtures, reaching a maximum value after which the flame speed decreases with strain rate. Heat loss decreases the stretched flame speed and leads to a sooner extinction of the flamelet due to combined strain and heat loss. Hydrogen addition and equivalence ratio significantly impact the maximum consumption speed and the flame response to combined strain rate and heat loss. The effect of hydrogen on the thermo-diffusive properties of the mixture, characterised by the Zeldovich number and the effective Lewis number, are also analyzed and related to the effect on the consumption speed. Two definitions of the Lewis number of the multi-component fuel mixture are evaluated against the results from the aCFPF.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46277988","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 : 2022-11-12DOI: 10.1080/13647830.2022.2143428
F. Vance, J. van Oijen, L. D. de Goey
Development of a premixed flame theory that includes the effects of flame stretch and curvature has been at the forefront of combustion research. Diffusion dominated flames such as highly curved flame balls present a challenging flame structure that has not been included in current flame stretch theory so far. In such flames, the relationship between consumption speed and negative displacement speed usually marks the boundary of what flame stretch theory can predict. In this work, our objective is to derive a general formulation which naturally includes this relationship. We use flamelet equations derived using a mass based stretch rate and show that if the diffusion flux at the unburnt side is not ignored, as is normally done in flame stretch theory, a formulation that can describe the propagation of different types of premixed flames can be derived. Based on the thin reaction zone assumption, solutions from theory are verified against numerical results for 1D ideal flame balls. Further verification is done for multi-dimensional ball-like flames, where both convection and diffusion dominated regions are present for highly curved flames. It is shown that the extended theory is able to predict the flame kinematics in a better way by describing the diffusion dominated flame propagation as well.
{"title":"Flame speed in diffusion dominated premixed flames","authors":"F. Vance, J. van Oijen, L. D. de Goey","doi":"10.1080/13647830.2022.2143428","DOIUrl":"https://doi.org/10.1080/13647830.2022.2143428","url":null,"abstract":"Development of a premixed flame theory that includes the effects of flame stretch and curvature has been at the forefront of combustion research. Diffusion dominated flames such as highly curved flame balls present a challenging flame structure that has not been included in current flame stretch theory so far. In such flames, the relationship between consumption speed and negative displacement speed usually marks the boundary of what flame stretch theory can predict. In this work, our objective is to derive a general formulation which naturally includes this relationship. We use flamelet equations derived using a mass based stretch rate and show that if the diffusion flux at the unburnt side is not ignored, as is normally done in flame stretch theory, a formulation that can describe the propagation of different types of premixed flames can be derived. Based on the thin reaction zone assumption, solutions from theory are verified against numerical results for 1D ideal flame balls. Further verification is done for multi-dimensional ball-like flames, where both convection and diffusion dominated regions are present for highly curved flames. It is shown that the extended theory is able to predict the flame kinematics in a better way by describing the diffusion dominated flame propagation as well.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45028730","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 : 2022-11-11DOI: 10.1080/13647830.2022.2144460
Panlong Yu, H. Watanabe
A simplified two-mixture-fraction-based flamelet model is proposed in this work for a non-premixed staged combustion mode in which three feeds are introduced into the flow field. As the third stream is injected downstream of the main port, the system can be considered a special case of the two-mixture-fraction-based systems. It is considered that if a well-mixing is achieved in the upper stream prior to the third-stream injection, the simplification of the two-mixture-fraction-based flamelet model is feasible. In this work, a simplified model is proposed which can greatly reduce the library size compared to the complete two-mixture-fraction-based flamelet library providing identical resolutions for the fuel stream mixture fraction and the progress variable, respectively. Analysis associated with the interpolation strategy has been implemented. Extension of the current model for the cases in which the well-mixing state is not attained is also analysed, as well as the consideration of heat loss. To validate the model, two adiabatic cases of two-dimensional (2D) direct numerical simulations (DNS) have been performed in this work. To describe the chemical events, one is using finite-rate chemistry (FRC), while the other one is realised by means of the current flamelet model (FLM). An a priori test case that directly looks up the libraries by using the tracking parameters obtained from the FRC case is also considered. It is observed that the interpolation along the primary oxidiser mixture fraction direction outperforms that along directions for both fuel and primary oxidiser mixture fractions. It is also found that three one-mixture-fraction-based flamelet libraries which form the current model are sufficient for simulation of the non-premixed staged combustion, while the extended one which composes five libraries is expected to gain higher accurateness. In the FLM case, although the distributions of tracking parameters deviate from the FRC case slightly, good agreements can be obtained in terms of temperature and species mass fractions. The a priori test shows that the current model can reproduce the reacting flow accurately when the tracking parameters are identical to the FRC case. It is confirmed that the current model can be used to predict the characteristics of the reacting flow in the non-premixed staged combustion.
{"title":"A simplified two-mixture-fraction-based flamelet modelling and its validation on a non-premixed staged combustion system","authors":"Panlong Yu, H. Watanabe","doi":"10.1080/13647830.2022.2144460","DOIUrl":"https://doi.org/10.1080/13647830.2022.2144460","url":null,"abstract":"A simplified two-mixture-fraction-based flamelet model is proposed in this work for a non-premixed staged combustion mode in which three feeds are introduced into the flow field. As the third stream is injected downstream of the main port, the system can be considered a special case of the two-mixture-fraction-based systems. It is considered that if a well-mixing is achieved in the upper stream prior to the third-stream injection, the simplification of the two-mixture-fraction-based flamelet model is feasible. In this work, a simplified model is proposed which can greatly reduce the library size compared to the complete two-mixture-fraction-based flamelet library providing identical resolutions for the fuel stream mixture fraction and the progress variable, respectively. Analysis associated with the interpolation strategy has been implemented. Extension of the current model for the cases in which the well-mixing state is not attained is also analysed, as well as the consideration of heat loss. To validate the model, two adiabatic cases of two-dimensional (2D) direct numerical simulations (DNS) have been performed in this work. To describe the chemical events, one is using finite-rate chemistry (FRC), while the other one is realised by means of the current flamelet model (FLM). An a priori test case that directly looks up the libraries by using the tracking parameters obtained from the FRC case is also considered. It is observed that the interpolation along the primary oxidiser mixture fraction direction outperforms that along directions for both fuel and primary oxidiser mixture fractions. It is also found that three one-mixture-fraction-based flamelet libraries which form the current model are sufficient for simulation of the non-premixed staged combustion, while the extended one which composes five libraries is expected to gain higher accurateness. In the FLM case, although the distributions of tracking parameters deviate from the FRC case slightly, good agreements can be obtained in terms of temperature and species mass fractions. The a priori test shows that the current model can reproduce the reacting flow accurately when the tracking parameters are identical to the FRC case. It is confirmed that the current model can be used to predict the characteristics of the reacting flow in the non-premixed staged combustion.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47741805","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 : 2022-11-10DOI: 10.1080/13647830.2022.2141138
Adam L. Comer, T. Gallagher, K. Duraisamy, B. Rankin
For large-eddy simulation of turbulent premixed reacting flows, major challenges stem from the inability to resolve the flame in a computationally affordable manner. These challenges are most evident in combustors characterized by large domains and thin flames. In these applications, the thickened flame model may be used to extend the flame artificially to a numerically resolvable size through a thickening factor. Thicker flames exhibit suppressed wrinkling in the presence of turbulence, so an efficiency factor increases the flame speed without influencing flame thickness. In contrast to the detailed considerations of unresolved turbulent flame wrinkling, recent work shows that thickened flames do not respond correctly to resolved-scale stretch. In this work, errors in stretch-induced extinction are considered. The already established effect of thickening on extinction is illustrated, and the effect of efficiency factor is characterized in detail. Significant errors in extinction stretch rate are observed analytically and numerically in twin premixed counterflow flame simulations. In general, the original thickened flame formulation does not permit control over extinction, in contrast to its control over freely-propagating-flame thickness and speed. For reactant mixtures with a Lewis number greater than 1, a novel modification of the thickened flame formulation is presented, and through Lewis number adjustments, extinction errors are significantly reduced, while key flame thickening and speed properties of the original formulation are preserved. A test case featuring a turbulent premixed bluff-body-stabilized flame demonstrates that the extinction errors of the original formulation can lead to premature blowoff dynamics and significant statistical errors, if the grid is too coarse. The modified thickened flame model applied to the same grids addresses this issue and provides reasonable flame predictions on all grids, indicating the potential for extending this combustion model to resolutions of greater engineering relevance.
{"title":"A modified thickened flame model for simulating extinction","authors":"Adam L. Comer, T. Gallagher, K. Duraisamy, B. Rankin","doi":"10.1080/13647830.2022.2141138","DOIUrl":"https://doi.org/10.1080/13647830.2022.2141138","url":null,"abstract":"For large-eddy simulation of turbulent premixed reacting flows, major challenges stem from the inability to resolve the flame in a computationally affordable manner. These challenges are most evident in combustors characterized by large domains and thin flames. In these applications, the thickened flame model may be used to extend the flame artificially to a numerically resolvable size through a thickening factor. Thicker flames exhibit suppressed wrinkling in the presence of turbulence, so an efficiency factor increases the flame speed without influencing flame thickness. In contrast to the detailed considerations of unresolved turbulent flame wrinkling, recent work shows that thickened flames do not respond correctly to resolved-scale stretch. In this work, errors in stretch-induced extinction are considered. The already established effect of thickening on extinction is illustrated, and the effect of efficiency factor is characterized in detail. Significant errors in extinction stretch rate are observed analytically and numerically in twin premixed counterflow flame simulations. In general, the original thickened flame formulation does not permit control over extinction, in contrast to its control over freely-propagating-flame thickness and speed. For reactant mixtures with a Lewis number greater than 1, a novel modification of the thickened flame formulation is presented, and through Lewis number adjustments, extinction errors are significantly reduced, while key flame thickening and speed properties of the original formulation are preserved. A test case featuring a turbulent premixed bluff-body-stabilized flame demonstrates that the extinction errors of the original formulation can lead to premature blowoff dynamics and significant statistical errors, if the grid is too coarse. The modified thickened flame model applied to the same grids addresses this issue and provides reasonable flame predictions on all grids, indicating the potential for extending this combustion model to resolutions of greater engineering relevance.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45473656","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 : 2022-11-07DOI: 10.1080/13647830.2022.2136038
M. Valorani, R. Malpica Galassi, P. P. Ciottoli, H. Najm, S. Paolucci
The size and complexity of multi-scale problems such as those arising in chemical kinetics mechanisms has stimulated the search for methods that reduce the number of species and chemical reactions but retain a desired degree of accuracy. The time-scale characterisation of the multi-scale problem can be carried out on the basis of local information such as the Jacobian matrix of the model problem and its related eigen-system evaluated at one point P of the system trajectory. While the original problem is usually described by ordinary differential equations (ODEs), the reduced order model is described by a reduced number of ODEs and a number of algebraic equations (AEs), that might express one or more physical conservation laws (mass, momentum, energy), or the fact that the long-term dynamics evolves within a so-called Slow Invariant Manifold (SIM). To fully exploit the benefits offered by a reduced order model, it is required that the time scale characterisation of the n-dimensional reduced order model returns an answer consistent and coherent with the time-scale characterisation of the N-dimensional original model. This manuscript discusses a procedure for obtaining the time-scale characterisation of the reduced order model in a manner that is consistent with that of the original problem. While a standard time scale characterisation of the (original) N-dimensional original model can be carried out by evaluating the eigen-system of the ( ) Jacobian matrix of the vector field that defines the system dynamics, the time-scale characterisation of the n-dimensional reduced order model (with n
{"title":"The spectral characterisation of reduced order models in chemical kinetic systems","authors":"M. Valorani, R. Malpica Galassi, P. P. Ciottoli, H. Najm, S. Paolucci","doi":"10.1080/13647830.2022.2136038","DOIUrl":"https://doi.org/10.1080/13647830.2022.2136038","url":null,"abstract":"The size and complexity of multi-scale problems such as those arising in chemical kinetics mechanisms has stimulated the search for methods that reduce the number of species and chemical reactions but retain a desired degree of accuracy. The time-scale characterisation of the multi-scale problem can be carried out on the basis of local information such as the Jacobian matrix of the model problem and its related eigen-system evaluated at one point P of the system trajectory. While the original problem is usually described by ordinary differential equations (ODEs), the reduced order model is described by a reduced number of ODEs and a number of algebraic equations (AEs), that might express one or more physical conservation laws (mass, momentum, energy), or the fact that the long-term dynamics evolves within a so-called Slow Invariant Manifold (SIM). To fully exploit the benefits offered by a reduced order model, it is required that the time scale characterisation of the n-dimensional reduced order model returns an answer consistent and coherent with the time-scale characterisation of the N-dimensional original model. This manuscript discusses a procedure for obtaining the time-scale characterisation of the reduced order model in a manner that is consistent with that of the original problem. While a standard time scale characterisation of the (original) N-dimensional original model can be carried out by evaluating the eigen-system of the ( ) Jacobian matrix of the vector field that defines the system dynamics, the time-scale characterisation of the n-dimensional reduced order model (with n","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46351053","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 : 2022-10-20DOI: 10.1080/13647830.2022.2137062
A. Newale, Pushan Sharma, S. Pope, P. Pepiot
Large eddy simulation (LES)/ Probability Density Function (PDF) approaches are now well established and can be used for simulating challenging turbulent combustion configurations with strong turbulence chemistry interactions. Transported PDF methods are known to be computationally expensive compared to flamelet-like turbulent combustion models. The pre-partitioned adaptive chemistry (PPAC) methodology was developed to address this cost differential. PPAC entails an offline preprocessing stage, where a set of reduced models are generated starting from an initial database of representative compositions. At runtime, this set of reduced models are dynamically utilised during the reaction fractional step leading to computational savings. We have recently combined PPAC with in-situ adaptive tabulation (ISAT) to further reduce the computational cost. We have shown that the combined method reduced the average wall-clock time per time step of large-scale LES/particle PDF simulations of turbulent combustion by 39%. A key assumption in PPAC is that the initial database used in the offline stage is representative of the compositions encountered at runtime. In our previous study this assumption was trivially satisfied as the initial database consisted of compositions extracted from the turbulent combustion simulation itself. Consequently, a key open question remains as to whether such databases can be generated without having access to the turbulent combustion simulation. Towards answering this question, in the current work, we explore whether the compositions for forming such a database can be extracted from computationally-efficient low-dimensional simulations such as 1D counterflow flames and partially stirred reactors. We show that a database generated using compositions extracted from a partially stirred reactor configuration leads to performance comparable to the optimal case, wherein the database is comprised of compositions extracted directly from the LES/PDF simulation itself.
{"title":"A feasibility study on the use of low-dimensional simulations for database generation in adaptive chemistry approaches","authors":"A. Newale, Pushan Sharma, S. Pope, P. Pepiot","doi":"10.1080/13647830.2022.2137062","DOIUrl":"https://doi.org/10.1080/13647830.2022.2137062","url":null,"abstract":"Large eddy simulation (LES)/ Probability Density Function (PDF) approaches are now well established and can be used for simulating challenging turbulent combustion configurations with strong turbulence chemistry interactions. Transported PDF methods are known to be computationally expensive compared to flamelet-like turbulent combustion models. The pre-partitioned adaptive chemistry (PPAC) methodology was developed to address this cost differential. PPAC entails an offline preprocessing stage, where a set of reduced models are generated starting from an initial database of representative compositions. At runtime, this set of reduced models are dynamically utilised during the reaction fractional step leading to computational savings. We have recently combined PPAC with in-situ adaptive tabulation (ISAT) to further reduce the computational cost. We have shown that the combined method reduced the average wall-clock time per time step of large-scale LES/particle PDF simulations of turbulent combustion by 39%. A key assumption in PPAC is that the initial database used in the offline stage is representative of the compositions encountered at runtime. In our previous study this assumption was trivially satisfied as the initial database consisted of compositions extracted from the turbulent combustion simulation itself. Consequently, a key open question remains as to whether such databases can be generated without having access to the turbulent combustion simulation. Towards answering this question, in the current work, we explore whether the compositions for forming such a database can be extracted from computationally-efficient low-dimensional simulations such as 1D counterflow flames and partially stirred reactors. We show that a database generated using compositions extracted from a partially stirred reactor configuration leads to performance comparable to the optimal case, wherein the database is comprised of compositions extracted directly from the LES/PDF simulation itself.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45804593","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 : 2022-10-20DOI: 10.1080/13647830.2022.2136039
Wenliang Zhou, Qizhao Lin
With the increase of bioenergy crops and the rapid development of agriculture, the total amount of solid waste is increasing rapidly. This study quantified the pyrolytic performance and gaseous products of spent coffee grounds (SCG), Chinese medicine residue (CMR), vinasse (VI) and camellia oil shell (COS) by using (derivative) thermogravimetric ((D)TG), Fourier transform infrared spectrometry (FTIR) and mass spectrometry (MS) analyses. There are two main stages of mass loss: volatilisation of volatiles and continuous decomposition of macromolecules. At a heating rate of 20°C/min, COS has the slowest pyrolysis rate compared to the other three. Model-free methods: Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) were used to calculate the activation energy (E) of samples with different conversion rates (α). SCG and VI have the highest average activation energy (about 240kJ/mol), followed by CMR (200kJ/mol), and COS the lowest (175kJ/mol). FTIR was mainly used to detect functional group types (including hydroxyl, carbonyl, aldehyde and ester groups, etc.), while MS co-detected the characteristics of condensable/non-condensable gases (including H2O, CO2, NOx, SOx, C6H6, C7H8, C9H8 and other major gas emissions, pollutants and hydrocarbons). Nitrogen oxides are produced in the range of 500–800°C. SCG and VI emit more gas pollutants than CMR and COS.
{"title":"Pyrolysis of four waste biomasses and elucidation of reaction kinetics and pyrolytic products","authors":"Wenliang Zhou, Qizhao Lin","doi":"10.1080/13647830.2022.2136039","DOIUrl":"https://doi.org/10.1080/13647830.2022.2136039","url":null,"abstract":"With the increase of bioenergy crops and the rapid development of agriculture, the total amount of solid waste is increasing rapidly. This study quantified the pyrolytic performance and gaseous products of spent coffee grounds (SCG), Chinese medicine residue (CMR), vinasse (VI) and camellia oil shell (COS) by using (derivative) thermogravimetric ((D)TG), Fourier transform infrared spectrometry (FTIR) and mass spectrometry (MS) analyses. There are two main stages of mass loss: volatilisation of volatiles and continuous decomposition of macromolecules. At a heating rate of 20°C/min, COS has the slowest pyrolysis rate compared to the other three. Model-free methods: Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) were used to calculate the activation energy (E) of samples with different conversion rates (α). SCG and VI have the highest average activation energy (about 240kJ/mol), followed by CMR (200kJ/mol), and COS the lowest (175kJ/mol). FTIR was mainly used to detect functional group types (including hydroxyl, carbonyl, aldehyde and ester groups, etc.), while MS co-detected the characteristics of condensable/non-condensable gases (including H2O, CO2, NOx, SOx, C6H6, C7H8, C9H8 and other major gas emissions, pollutants and hydrocarbons). Nitrogen oxides are produced in the range of 500–800°C. SCG and VI emit more gas pollutants than CMR and COS.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47450875","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 : 2022-10-13DOI: 10.1080/13647830.2022.2132015
S. Yakush, O. Korobeinichev, A. Shmakov, T. Bolshova, S. Trubachev
Gas-phase combustion of methylmethacrylate (MMA) monomer is an essential stage of solid polymethylmethacrylate (PMMA) combustion, which is of interest in many applications. A skeletal kinetic scheme for MMA combustion in air is proposed including 44 irreversible elementary reactions for 29 species. The mechanism is derived from the reduced kinetic scheme for MMA oxidation comprised of 263 reactions for 66 components. In this work, the mechanism predictive capabilities are demonstrated by solving the self-ignition problem, as well as the premixed flame propagation problem for MMA-air mixtures. It is shown that the skeletal mechanism overpredicts the ignition delay times due to significant simplification of the MMA decomposition stage reaction pathways. The flame propagation speed is predicted reasonably for lean and nearly-stoichiometric mixtures, but overpredicted for fuel-rich mixtures. Also, a diffusion flame representing the cup burner of liquid MMA is simulated in two-dimensional statement of the problem, the results are shown to agree well with the measurements and numerical simulations performed earlier on the basis of a detailed kinetic scheme. The skeletal mechanism can be used in the numerical simulations of gas-phase combustion of MMA, including the problems of flame propagation over the solid PMMA polymer.
{"title":"A reduced kinetic scheme for methyl methacrylate gas-phase combustion","authors":"S. Yakush, O. Korobeinichev, A. Shmakov, T. Bolshova, S. Trubachev","doi":"10.1080/13647830.2022.2132015","DOIUrl":"https://doi.org/10.1080/13647830.2022.2132015","url":null,"abstract":"Gas-phase combustion of methylmethacrylate (MMA) monomer is an essential stage of solid polymethylmethacrylate (PMMA) combustion, which is of interest in many applications. A skeletal kinetic scheme for MMA combustion in air is proposed including 44 irreversible elementary reactions for 29 species. The mechanism is derived from the reduced kinetic scheme for MMA oxidation comprised of 263 reactions for 66 components. In this work, the mechanism predictive capabilities are demonstrated by solving the self-ignition problem, as well as the premixed flame propagation problem for MMA-air mixtures. It is shown that the skeletal mechanism overpredicts the ignition delay times due to significant simplification of the MMA decomposition stage reaction pathways. The flame propagation speed is predicted reasonably for lean and nearly-stoichiometric mixtures, but overpredicted for fuel-rich mixtures. Also, a diffusion flame representing the cup burner of liquid MMA is simulated in two-dimensional statement of the problem, the results are shown to agree well with the measurements and numerical simulations performed earlier on the basis of a detailed kinetic scheme. The skeletal mechanism can be used in the numerical simulations of gas-phase combustion of MMA, including the problems of flame propagation over the solid PMMA polymer.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46643102","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}
A hybrid particle/finite volume algorithm has been formulated for zone-adaptive modelling of turbulent reactive flows to achieve both high fidelity in predictions and high computational efficiency. Specifically, a computationally economical species transport model via finite volume algorithm is employed as the base model for the whole computational domain, while the advanced transported probability density function (TPDF) method via Lagrangian particle tracking is employed only for regions with intense turbulence-chemistry interaction. The ‘PDF regions’ can be updated dynamically based on local flow and flame characteristics, and are compatible with complex geometric structures such as separated multi blocks, non-convex, and multi-connected regions. A two-way particle/finite volume submodel coupling is formulated to ensure the composition consistency in submodels in the PDF regions and to impose the correct interface conditions for composition and mass flow rate on the boundary of the PDF regions. The spatial partition and particle algorithms for time-varying PDF regions are demonstrated and the convergence characteristics of the adaptive modelling are investigated specifically for the variation of statistical error and bias with the number of particles per cell. The proposed zone-adaptive hybrid particle/finite volume algorithm has been numerically validated in a turbulent hydrogen/air non-premixed jet flame. It is shown that the predictions from zone-adaptive modelling are almost identical to those of stand-alone TPDF, illustrating the preservation of prediction accuracy but with significantly less computational cost.
{"title":"Consistent submodel coupling in hybrid particle/finite volume algorithms for zone-adaptive modelling of turbulent reactive flows","authors":"Tianwei Yang, Yuchao Yin, Hua Zhou, Yi Mo, Yuxuan Chen, Zhuyin Ren","doi":"10.1080/13647830.2022.2133636","DOIUrl":"https://doi.org/10.1080/13647830.2022.2133636","url":null,"abstract":"A hybrid particle/finite volume algorithm has been formulated for zone-adaptive modelling of turbulent reactive flows to achieve both high fidelity in predictions and high computational efficiency. Specifically, a computationally economical species transport model via finite volume algorithm is employed as the base model for the whole computational domain, while the advanced transported probability density function (TPDF) method via Lagrangian particle tracking is employed only for regions with intense turbulence-chemistry interaction. The ‘PDF regions’ can be updated dynamically based on local flow and flame characteristics, and are compatible with complex geometric structures such as separated multi blocks, non-convex, and multi-connected regions. A two-way particle/finite volume submodel coupling is formulated to ensure the composition consistency in submodels in the PDF regions and to impose the correct interface conditions for composition and mass flow rate on the boundary of the PDF regions. The spatial partition and particle algorithms for time-varying PDF regions are demonstrated and the convergence characteristics of the adaptive modelling are investigated specifically for the variation of statistical error and bias with the number of particles per cell. The proposed zone-adaptive hybrid particle/finite volume algorithm has been numerically validated in a turbulent hydrogen/air non-premixed jet flame. It is shown that the predictions from zone-adaptive modelling are almost identical to those of stand-alone TPDF, illustrating the preservation of prediction accuracy but with significantly less computational cost.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45902153","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 : 2022-09-16DOI: 10.1080/13647830.2022.2121663
V. Kurdyumov, C. Jiménez
The purpose of this work is to demonstrate that there are different stable configurations of lifted edge flames for the same set of parameters. It is shown that when a fuel jet is injected surrounded by oxidiser streams of equal velocity, there are configurations with symmetric and non-symmetric flame structures with respect to the symmetry line of the problem. These two kinds of solutions are both stable and the actual realisation of one or another solution depends on the initial conditions, in particular on the flame ignition parameters. It is shown that this multiple solution phenomenon takes place when the fuel Lewis number is less than unity. The influence of the Zel'dovich number and the injection flow rate is also investigated.
{"title":"Lifted jet edge flames: symmetric and non-symmetric configurations","authors":"V. Kurdyumov, C. Jiménez","doi":"10.1080/13647830.2022.2121663","DOIUrl":"https://doi.org/10.1080/13647830.2022.2121663","url":null,"abstract":"The purpose of this work is to demonstrate that there are different stable configurations of lifted edge flames for the same set of parameters. It is shown that when a fuel jet is injected surrounded by oxidiser streams of equal velocity, there are configurations with symmetric and non-symmetric flame structures with respect to the symmetry line of the problem. These two kinds of solutions are both stable and the actual realisation of one or another solution depends on the initial conditions, in particular on the flame ignition parameters. It is shown that this multiple solution phenomenon takes place when the fuel Lewis number is less than unity. The influence of the Zel'dovich number and the injection flow rate is also investigated.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2022-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41979022","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：