Pub Date : 2023-11-02DOI: 10.1080/13647830.2023.2276696
Yusen Liu, Jiabo Zhang, Dong Han
AbstractThis study provides a chemical mechanism reduction strategy based on entropy production analyses in both auto-ignition and laminar flames, which enhances the predictive accuracy for laminar burning velocities. In addition to chemical reactions, other irreversible sources causing entropy generation, such as mass diffusion and heat conduction, are considered in the modified approach. Specifically, initial skeletal mechanisms are first generated based on important reactions that contribute to entropy production in auto-ignition processes. Mechanism patches are then constructed to include important species and reactions, which contribute to entropy production from mass diffusion and heat conduction in laminar premixed flames beyond the pre-defined thresholds, respectively. Finally, the initial skeletal mechanisms and mechanism patches are combined to establish the final skeletal mechanisms. In this way, two final skeletal mechanisms for n-dodecane, consisting of 162 species and 2276 reactions, and 160 species and 1916 reactions, respectively, are developed from the detailed POLIMI mechanism with 451 species and 17,848 reactions. The two final skeletal mechanisms are proven to accurately predict laminar burning velocities and entropy production in n-dodecane flames with insignificant variations in the simulation results compared to the detailed mechanism, while their accuracy in predicting ignition delay times relies on the initial skeletal mechanisms. Specifically, the reduced mechanism with 160 species and 1916 reactions exhibits less satisfactory performance in predicting ignition delay compared to that with 162 species and 2276 reactions, indicating that a lower threshold is required to generate the initial skeletal mechanism through entropy production analysis of homogeneous auto-ignition processes. Additionally, compared with the reduced mechanisms with similar sizes obtained with other mechanism reduction strategies, the two final skeletal mechanisms accurately capture the characteristics of laminar burning velocities and ignition delay times, with similar calculation time required.Keywords: mechanism reductionentropy production analysishomogeneous auto-ignitionlaminar flamen-dodecane Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work is supported by the National Natural Science Foundation of China [grant numbers 52106261 and 52022058], the Postdoctoral Research Foundation of China [grant numbers 2022M712042 and 2022T150403].
{"title":"A combustion mechanism reduction method based on entropy production analysis in fuel auto-ignition and laminar flames","authors":"Yusen Liu, Jiabo Zhang, Dong Han","doi":"10.1080/13647830.2023.2276696","DOIUrl":"https://doi.org/10.1080/13647830.2023.2276696","url":null,"abstract":"AbstractThis study provides a chemical mechanism reduction strategy based on entropy production analyses in both auto-ignition and laminar flames, which enhances the predictive accuracy for laminar burning velocities. In addition to chemical reactions, other irreversible sources causing entropy generation, such as mass diffusion and heat conduction, are considered in the modified approach. Specifically, initial skeletal mechanisms are first generated based on important reactions that contribute to entropy production in auto-ignition processes. Mechanism patches are then constructed to include important species and reactions, which contribute to entropy production from mass diffusion and heat conduction in laminar premixed flames beyond the pre-defined thresholds, respectively. Finally, the initial skeletal mechanisms and mechanism patches are combined to establish the final skeletal mechanisms. In this way, two final skeletal mechanisms for n-dodecane, consisting of 162 species and 2276 reactions, and 160 species and 1916 reactions, respectively, are developed from the detailed POLIMI mechanism with 451 species and 17,848 reactions. The two final skeletal mechanisms are proven to accurately predict laminar burning velocities and entropy production in n-dodecane flames with insignificant variations in the simulation results compared to the detailed mechanism, while their accuracy in predicting ignition delay times relies on the initial skeletal mechanisms. Specifically, the reduced mechanism with 160 species and 1916 reactions exhibits less satisfactory performance in predicting ignition delay compared to that with 162 species and 2276 reactions, indicating that a lower threshold is required to generate the initial skeletal mechanism through entropy production analysis of homogeneous auto-ignition processes. Additionally, compared with the reduced mechanisms with similar sizes obtained with other mechanism reduction strategies, the two final skeletal mechanisms accurately capture the characteristics of laminar burning velocities and ignition delay times, with similar calculation time required.Keywords: mechanism reductionentropy production analysishomogeneous auto-ignitionlaminar flamen-dodecane Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work is supported by the National Natural Science Foundation of China [grant numbers 52106261 and 52022058], the Postdoctoral Research Foundation of China [grant numbers 2022M712042 and 2022T150403].","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135972978","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 : 2023-10-20DOI: 10.1080/13647830.2023.2271437
Amir H. Mahdipour, Cecile Devaud
AbstractThe objective of the present study is to investigate two new formulations of the Conditional Source-term Estimation (CSE) model using Reynolds Averaged Navier Stokes (RANS) calculations applied to Sandia flames D and F. The first method relies on a first-order Tikhonov regularisation and the second approach denoted by CSEBP, includes Bernstein polynomials to approximate the conditional averages. Current predictions for temperature, main product and minor species are consistent with previously published CSE results with a different implementation. However, smoother conditional profiles are obtained with less a priori information. Both formulations have good predictions for flame D with minor discrepancies near the inlet and one position downstream, with occasional small advantages for CSEBP. In contrast to previous RANS-CSE attempts, stable solutions are obtained for flame F in good agreement with the experiments. Considering the RANS and single conditioning limitations to capture transient effects, both formulations predict the changes of conditional averages and Favre averaged quantities from flame D to F well, except at one location where the predicted re-ignition occurs earlier than what is seen in the experiments. Additionally, the computational cost of the CSE routine is decreased significantly from 85% of the total computational cost to only 10% for the first formulation and under 3% for CSEBP by means of using hash tables for storing the results of interpolations from the chemistry tables and avoiding on-the-fly interpolations.Keywords: CSEBernstein polynomialsturbulencecombustionSandia flames Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work has been supported by Natural Sciences and Engineering Research Council of Canada (NSERC).
{"title":"Different conditional source-term estimation formulations applied to turbulent nonpremixed jet flames with varying levels of extinction","authors":"Amir H. Mahdipour, Cecile Devaud","doi":"10.1080/13647830.2023.2271437","DOIUrl":"https://doi.org/10.1080/13647830.2023.2271437","url":null,"abstract":"AbstractThe objective of the present study is to investigate two new formulations of the Conditional Source-term Estimation (CSE) model using Reynolds Averaged Navier Stokes (RANS) calculations applied to Sandia flames D and F. The first method relies on a first-order Tikhonov regularisation and the second approach denoted by CSEBP, includes Bernstein polynomials to approximate the conditional averages. Current predictions for temperature, main product and minor species are consistent with previously published CSE results with a different implementation. However, smoother conditional profiles are obtained with less a priori information. Both formulations have good predictions for flame D with minor discrepancies near the inlet and one position downstream, with occasional small advantages for CSEBP. In contrast to previous RANS-CSE attempts, stable solutions are obtained for flame F in good agreement with the experiments. Considering the RANS and single conditioning limitations to capture transient effects, both formulations predict the changes of conditional averages and Favre averaged quantities from flame D to F well, except at one location where the predicted re-ignition occurs earlier than what is seen in the experiments. Additionally, the computational cost of the CSE routine is decreased significantly from 85% of the total computational cost to only 10% for the first formulation and under 3% for CSEBP by means of using hash tables for storing the results of interpolations from the chemistry tables and avoiding on-the-fly interpolations.Keywords: CSEBernstein polynomialsturbulencecombustionSandia flames Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work has been supported by Natural Sciences and Engineering Research Council of Canada (NSERC).","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135567521","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 : 2023-10-20DOI: 10.1080/13647830.2023.2270455
Yongsheng Jia, Yingkang Yao, Qi Zhang
AbstractUnlike the explosion limit of liquid fuel vapour, the explosion limit of aerosol is a function of the aerosol state. In this study, a prediction model of the lower explosion limit (LEL) of liquid fuel aerosol was established through theoretical analysis, and typical liquid fuels of n-heptane and n-hexane were used to observe the aerosol state and the lower explosion concentration limits in the experiments to verify the reliability of the established model for predicting the LEL of aerosol. The predicted LELs of the two n-heptane aerosols (D32 = 12.16 µm) and (D32 = 21.23 µm) are 3.59 and 3.62 times of that of n-heptane vapour, respectively. The relative errors for the predictive results are 5.4% and 8.8%, respectively, compared with the experimental results. The predicted LEL of n-hexane aerosol (D32 = 18.51 µm) is 3.5 times that of n-hexane vapour, and the relative error is 3.99% compared with the experimental results.Keywords: Liquid fuelcombustible aerosolLELpredictive modelaerosol state AcknowledgementsThanks to Dr. Xueling Liu for participating in the experiments.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThe research presented in this paper was supported by State Key Laboratory of Precision Blasting and Hubei Key Laboratory of Blasting Engineering, Jianghan University [grant number PBSKL2022A02].
{"title":"Prediction of lower explosion limit of liquid fuel aerosol","authors":"Yongsheng Jia, Yingkang Yao, Qi Zhang","doi":"10.1080/13647830.2023.2270455","DOIUrl":"https://doi.org/10.1080/13647830.2023.2270455","url":null,"abstract":"AbstractUnlike the explosion limit of liquid fuel vapour, the explosion limit of aerosol is a function of the aerosol state. In this study, a prediction model of the lower explosion limit (LEL) of liquid fuel aerosol was established through theoretical analysis, and typical liquid fuels of n-heptane and n-hexane were used to observe the aerosol state and the lower explosion concentration limits in the experiments to verify the reliability of the established model for predicting the LEL of aerosol. The predicted LELs of the two n-heptane aerosols (D32 = 12.16 µm) and (D32 = 21.23 µm) are 3.59 and 3.62 times of that of n-heptane vapour, respectively. The relative errors for the predictive results are 5.4% and 8.8%, respectively, compared with the experimental results. The predicted LEL of n-hexane aerosol (D32 = 18.51 µm) is 3.5 times that of n-hexane vapour, and the relative error is 3.99% compared with the experimental results.Keywords: Liquid fuelcombustible aerosolLELpredictive modelaerosol state AcknowledgementsThanks to Dr. Xueling Liu for participating in the experiments.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThe research presented in this paper was supported by State Key Laboratory of Precision Blasting and Hubei Key Laboratory of Blasting Engineering, Jianghan University [grant number PBSKL2022A02].","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135567911","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 : 2023-10-17DOI: 10.1080/13647830.2023.2270962
Haochen Liu, Chao Xu, Zifei Yin, Hong Liu
AbstractThe grid resolution requirement for trustworthy Chemical Explosive Mode Analysis (CEMA) in Large Eddy Simulation (LES) of premixed turbulent combustion is proposed. Explicit filtering, to emulate the effect of the LES filter, is applied to one-dimensional laminar flame and three-dimensional planar turbulent flames across a wide range of Karlovitz numbers (5−239). The identification of the flame front by CEMA is found relatively insensitive to the cell size (Δ), while the combustion mode identification shows more significant sensitivity. Specifically, increasing Δ falsely enhances the auto-ignition and local extinction modes and suppresses the diffusion-assisted mode. Limited dependence of the CEMA performance on the turbulent combustion regime (Karlovitz number) is observed. A simple grid size criterion for reliable CEMA mode identification in LES is proposed as Δ≲δL/2; The criterion can be relaxed to Δ≲δL in the laminar flame limit. Furthermore, theoretical analysis is conducted on an idealised chemistry-diffusion system. The effects of the filtering process and turbulence on the local combustion mode are demonstrated, which is consistent with the numerical observations. By incorporating turbulent combustion models in CEMA, potential improvement in identifying local combustion modes can be expected.Keywords: chemical explosive mode analysis (CEMA)large eddy simulation (LES)premixed turbulent combustion AcknowledgmentsThe numerical computations were performed using π-2.0 at the Center for High-Performance Computing, Shanghai Jiao Tong University.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThe authors gratefully acknowledge financial support from the National Natural Science Foundation of China (No. 91941301 and No. 12002210) and the Shanghai Municipal Natural Science Foundation (No. 21ZR1434000). Argonne National Laboratory's work was supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under contract DE-AC02-06CH11357.
{"title":"Grid resolution requirement of chemical explosive mode analysis for large eddy simulations of premixed turbulent combustion","authors":"Haochen Liu, Chao Xu, Zifei Yin, Hong Liu","doi":"10.1080/13647830.2023.2270962","DOIUrl":"https://doi.org/10.1080/13647830.2023.2270962","url":null,"abstract":"AbstractThe grid resolution requirement for trustworthy Chemical Explosive Mode Analysis (CEMA) in Large Eddy Simulation (LES) of premixed turbulent combustion is proposed. Explicit filtering, to emulate the effect of the LES filter, is applied to one-dimensional laminar flame and three-dimensional planar turbulent flames across a wide range of Karlovitz numbers (5−239). The identification of the flame front by CEMA is found relatively insensitive to the cell size (Δ), while the combustion mode identification shows more significant sensitivity. Specifically, increasing Δ falsely enhances the auto-ignition and local extinction modes and suppresses the diffusion-assisted mode. Limited dependence of the CEMA performance on the turbulent combustion regime (Karlovitz number) is observed. A simple grid size criterion for reliable CEMA mode identification in LES is proposed as Δ≲δL/2; The criterion can be relaxed to Δ≲δL in the laminar flame limit. Furthermore, theoretical analysis is conducted on an idealised chemistry-diffusion system. The effects of the filtering process and turbulence on the local combustion mode are demonstrated, which is consistent with the numerical observations. By incorporating turbulent combustion models in CEMA, potential improvement in identifying local combustion modes can be expected.Keywords: chemical explosive mode analysis (CEMA)large eddy simulation (LES)premixed turbulent combustion AcknowledgmentsThe numerical computations were performed using π-2.0 at the Center for High-Performance Computing, Shanghai Jiao Tong University.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThe authors gratefully acknowledge financial support from the National Natural Science Foundation of China (No. 91941301 and No. 12002210) and the Shanghai Municipal Natural Science Foundation (No. 21ZR1434000). Argonne National Laboratory's work was supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under contract DE-AC02-06CH11357.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135994646","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 : 2023-10-09DOI: 10.1080/13647830.2023.2267526
Shahrooz Motaghian, Tarek Beji
AbstractThis paper proposes a Laminar Smoke Point (LSP)-based soot model, incorporating (as opposed to previously developed LSP-based models) soot surface growth. The latter is indeed believed to be dominant in soot formation. Simple reactions are also introduced to account for the conversion of fuel and oxygen in soot evolution mechanisms. The proposed and a reference LSP-based soot models have been implemented in OpenFOAM-v2006 and assessed against a wide variety of laminar flames (16 flames). A calibration-evaluation procedure is defined in which some flames are involved in the calibration of the constants, and the majority are utilised in an independent evaluation stage. The results show that the newly added features to the LSP-based soot modelling approach allow for a better agreement over a wider range of conditions, e.g. diluted and highly sooty flames. It is shown that although the proposed model is more accurate for buoyant flames, it performs significantly better than the reference model for non-buoyant flames.Keywords: CFDlaminar smoke pointsoot modellingOpenFOAMlaminar diffusion flames Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work is funded by Ghent University (UGent), Belgium. Project number BOF/STA/201909/008.
{"title":"A laminar smoke point-based soot model considering surface growth and soot reactions","authors":"Shahrooz Motaghian, Tarek Beji","doi":"10.1080/13647830.2023.2267526","DOIUrl":"https://doi.org/10.1080/13647830.2023.2267526","url":null,"abstract":"AbstractThis paper proposes a Laminar Smoke Point (LSP)-based soot model, incorporating (as opposed to previously developed LSP-based models) soot surface growth. The latter is indeed believed to be dominant in soot formation. Simple reactions are also introduced to account for the conversion of fuel and oxygen in soot evolution mechanisms. The proposed and a reference LSP-based soot models have been implemented in OpenFOAM-v2006 and assessed against a wide variety of laminar flames (16 flames). A calibration-evaluation procedure is defined in which some flames are involved in the calibration of the constants, and the majority are utilised in an independent evaluation stage. The results show that the newly added features to the LSP-based soot modelling approach allow for a better agreement over a wider range of conditions, e.g. diluted and highly sooty flames. It is shown that although the proposed model is more accurate for buoyant flames, it performs significantly better than the reference model for non-buoyant flames.Keywords: CFDlaminar smoke pointsoot modellingOpenFOAMlaminar diffusion flames Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work is funded by Ghent University (UGent), Belgium. Project number BOF/STA/201909/008.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135142214","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}
AbstractPartially-premixed flames (PPFs) incorporate effects of both premixed and non-premixed types of reaction zones. The modelling of PPFs using manifold-based model reduction methods faces some inherent difficulties due to the underlying assumptions of a-priori identification of the type of combustion system. In this work, the reaction–diffusion manifold (REDIM) model reduction method is applied to study PPFs. The REDIM method requires minimal prior knowledge about the type of combustion system, which makes it a suitable method for studying PPFs. It allows incorporating system-specific diffusion (gradients) terms in a generic way so that the manifold can evolve according to the diffusion related information provided by the combustion system. In this way, a prior identification of the type of combustion system is no longer needed.This work utilises an iterative methodology to generate REDIM chemistry tables so that the reduced manifold can be iteratively converged very close to the detailed manifold according to the gradients of the reduced coordinates provided by the physical combustion system in each iteration step. In addition, a new method is proposed to provide the gradient estimates of the reduced coordinates during the generation of REDIM from the scattered gradient data in REDIM reduced CFD calculations. Laminar triple flames, a special case of PPFs, with two types of mixture fraction gradients are selected as the target cases to assess the presented iterative methodology. REDIM reduced calculations are compared with simulations based on detailed finite-rate kinetics. It is found that in the final iteration steps, temperature and all considered major and minor species mass fraction profiles are very well predicted by the REDIM reduced calculations.Keywords: Reaction–diffusion manifold (REDIM)model reductionpartially-premixed flametriple flamelaminar flame Disclosure statementNo potential conflict of interest was reported by the author(s).Supplemental dataSupplemental data for this article can be accessed online at http://dx.doi.org/10.1080/13647830.2023.2260350.Additional informationFundingFinancial support by the German Research Foundation (DFG) within the projects SFB/TRR 150 (project number 237267381) within sub-projects B06 and B07 is gratefully acknowledged.
{"title":"An iterative methodology for REDIM reduced chemistry generation and its validation for partially-premixed combustion","authors":"Prashant Shrotriya, Robert Schießl, Chunkan Yu, Viatcheslav Bykov, Thorsten Zirwes, Ulrich Maas","doi":"10.1080/13647830.2023.2260350","DOIUrl":"https://doi.org/10.1080/13647830.2023.2260350","url":null,"abstract":"AbstractPartially-premixed flames (PPFs) incorporate effects of both premixed and non-premixed types of reaction zones. The modelling of PPFs using manifold-based model reduction methods faces some inherent difficulties due to the underlying assumptions of a-priori identification of the type of combustion system. In this work, the reaction–diffusion manifold (REDIM) model reduction method is applied to study PPFs. The REDIM method requires minimal prior knowledge about the type of combustion system, which makes it a suitable method for studying PPFs. It allows incorporating system-specific diffusion (gradients) terms in a generic way so that the manifold can evolve according to the diffusion related information provided by the combustion system. In this way, a prior identification of the type of combustion system is no longer needed.This work utilises an iterative methodology to generate REDIM chemistry tables so that the reduced manifold can be iteratively converged very close to the detailed manifold according to the gradients of the reduced coordinates provided by the physical combustion system in each iteration step. In addition, a new method is proposed to provide the gradient estimates of the reduced coordinates during the generation of REDIM from the scattered gradient data in REDIM reduced CFD calculations. Laminar triple flames, a special case of PPFs, with two types of mixture fraction gradients are selected as the target cases to assess the presented iterative methodology. REDIM reduced calculations are compared with simulations based on detailed finite-rate kinetics. It is found that in the final iteration steps, temperature and all considered major and minor species mass fraction profiles are very well predicted by the REDIM reduced calculations.Keywords: Reaction–diffusion manifold (REDIM)model reductionpartially-premixed flametriple flamelaminar flame Disclosure statementNo potential conflict of interest was reported by the author(s).Supplemental dataSupplemental data for this article can be accessed online at http://dx.doi.org/10.1080/13647830.2023.2260350.Additional informationFundingFinancial support by the German Research Foundation (DFG) within the projects SFB/TRR 150 (project number 237267381) within sub-projects B06 and B07 is gratefully acknowledged.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135535653","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 : 2023-09-26DOI: 10.1080/13647830.2023.2258841
Mohammad Reza Salimi, Hadiseh Karimaei, Mostafa Gholampour Yazdi
AbstractMonopropellant hydrazine thruster, depending on their thrust level, specific impulse, and unique functional regime, are widely used in situation control, orbital transmission, and position correction systems of satellites. In these thrusters, hydrazine decomposes by passing through the catalyst bed in a highly exothermic reaction to hot gas products. Hot gases generate thrust force by passing through a convergent-divergent nozzle. Pore scale analysis of catalytic reactions is very common in various industries and is of interest to researchers due to its accuracy. In this paper, the decomposition chamber of a monopropellant hydrazine thruster is numerically simulated with a single-part bed model at the pore-scale. The length of decomposition chamber was 2.48 cm. Then the effects of parameters such as catalyst granule diameter, catalyst bed porosity coefficient and also chamber inlet pressure on the performance of the decomposition chamber and thruster are investigated. Simulations have been performed for catalyst granules with diameters of 0.88, 1.00 and 1.15 mm in three porosity coefficients of 0.4, 0.55 and 0.65. The inlet pressure is also changed from 10 to 25 bar in four different levels. The results showed that the porosity coefficient is the most effective parameter and with its decrease, the specific impulse and temperature rise, while the thrust force and mass flow rate intensify. Also, the size of the catalyst granules affects the performance of the bed and thruster so that by increasing it (at a certain porosity coefficient), a trend similar to the effect of decreasing the porosity coefficient can be seen in the results. On the other hand, with enhancing inlet pressure, the thrust force increases significantly. In this paper, the effect of bed parameters on the thruster performance is discussed in detail, which contains helpful results for researchers that work on improving the decomposition chamber efficiency.Keywords: monopropellant thruster; catalyst bed; decomposition chamber; catalyst granule diameter; bed porosity coefficient; chamber inlet pressure; pore scale analysis Disclosure statementNo potential conflict of interest was reported by the author(s).
{"title":"Numerical modeling and parametric analysis of performance of a monopropellant thruster using a single-part catalyst bed model","authors":"Mohammad Reza Salimi, Hadiseh Karimaei, Mostafa Gholampour Yazdi","doi":"10.1080/13647830.2023.2258841","DOIUrl":"https://doi.org/10.1080/13647830.2023.2258841","url":null,"abstract":"AbstractMonopropellant hydrazine thruster, depending on their thrust level, specific impulse, and unique functional regime, are widely used in situation control, orbital transmission, and position correction systems of satellites. In these thrusters, hydrazine decomposes by passing through the catalyst bed in a highly exothermic reaction to hot gas products. Hot gases generate thrust force by passing through a convergent-divergent nozzle. Pore scale analysis of catalytic reactions is very common in various industries and is of interest to researchers due to its accuracy. In this paper, the decomposition chamber of a monopropellant hydrazine thruster is numerically simulated with a single-part bed model at the pore-scale. The length of decomposition chamber was 2.48 cm. Then the effects of parameters such as catalyst granule diameter, catalyst bed porosity coefficient and also chamber inlet pressure on the performance of the decomposition chamber and thruster are investigated. Simulations have been performed for catalyst granules with diameters of 0.88, 1.00 and 1.15 mm in three porosity coefficients of 0.4, 0.55 and 0.65. The inlet pressure is also changed from 10 to 25 bar in four different levels. The results showed that the porosity coefficient is the most effective parameter and with its decrease, the specific impulse and temperature rise, while the thrust force and mass flow rate intensify. Also, the size of the catalyst granules affects the performance of the bed and thruster so that by increasing it (at a certain porosity coefficient), a trend similar to the effect of decreasing the porosity coefficient can be seen in the results. On the other hand, with enhancing inlet pressure, the thrust force increases significantly. In this paper, the effect of bed parameters on the thruster performance is discussed in detail, which contains helpful results for researchers that work on improving the decomposition chamber efficiency.Keywords: monopropellant thruster; catalyst bed; decomposition chamber; catalyst granule diameter; bed porosity coefficient; chamber inlet pressure; pore scale analysis Disclosure statementNo potential conflict of interest was reported by the author(s).","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134886474","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 : 2023-09-25DOI: 10.1080/13647830.2023.2261895
Mojtaba Latifi, Mohammad Mahdi Salehi
AbstractConditional Source-term Estimation (CSE) is a turbulence-chemistry interaction model similar to CMC, except that the conditional scalars are calculated from unconditional ones using an integral equation. This problem is inherently ill-posed and should be regularised. Recently, an efficient regularisation approach based on Bernstein polynomial expansion was proposed by Mahdipour and Salehi (Combust. Flame, 2022) in an a priori analysis using DNS data. This work implements this approach in a reacting flow solver, and two laboratory-scale turbulent premixed flames are simulated in the Reynolds-Averaged Navier-Stokes (RANS) context. The turbulent intensity in the first flame is low, and the results show that, unlike the conventional CSE approach, the new approach can accurately predict the flamelet conditional averages. Furthermore, the predicted averaged velocity field and major and minor species mass fractions compare favourably with the experimental measurements. The turbulent intensity in the second flame is relatively higher, and the predicted conditional averages should deviate from an unstrained laminar flame solution. The new approach can correctly predict this trend as well as the flame height in this flame. The computational cost of the new CSE approach is also substantially reduced compared to the regular CSE approach.Keywords: turbulent combustionpremixed flamestabulated chemistryconditional moment closureconditional source-term estimation Disclosure statementNo potential conflict of interest was reported by the author(s).
【摘要】条件源项估计(CSE)是一种类似CMC的湍流-化学相互作用模型，不同之处是条件标量由无条件标量用积分方程计算而成。这个问题本质上是病态的，应该加以规范。最近，Mahdipour和Salehi (comust)提出了一种基于Bernstein多项式展开的高效正则化方法。Flame, 2022)，使用DNS数据进行先验分析。这项工作在反应流求解器中实现了这种方法，并在reynolds - average Navier-Stokes (RANS)环境中模拟了两个实验室规模的湍流预混火焰。结果表明，与传统的CSE方法不同，该方法可以准确地预测小火焰条件平均。此外，预测的平均速度场和主要和次要物种质量分数与实验结果比较吻合。第二火焰中的湍流强度相对较高，并且预测的条件平均值应该偏离非应变层流火焰解。新方法可以准确地预测这一趋势以及火焰高度。与常规CSE方法相比，新的CSE方法的计算成本也大大降低。关键词:湍流燃烧预混燃烧确定化学条件力矩闭合条件源项估计披露声明作者未报告潜在的利益冲突。
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Pub Date : 2023-09-25DOI: 10.1080/13647830.2023.2261423
Xinyi Chen, Zisen Li, Yiqing Wang, Wang Han, Arne Scholtissek, Peng Dai, Christian Hasse, Zheng Chen
AbstractNon-premixed combustion often occurs in practical engines, and it is affected by the coupling effects of chemical kinetics and transport. This study aims to elucidate the individual effect of chemical kinetics, molecular diffusion, and convective transport on non-premixed combustion. To this end, three types of reactive systems are investigated by numerical simulations considering detailed chemistry and transport: (1) thermochemical system: 0D homogeneous autoignition, (2) thermochemical-diffusive system: 1D non-premixed ignition in a static diffusion layer, (3) thermochemical-diffusive-convective system: 1D non-premixed ignition in a counterflow and 2D lifted flame in a coflow. The simulations are carried out for diluted dimethyl ether and hot air under engine-relevant conditions with a pressure of 40 atm and hot air temperatures of 700∼1500 K. First, homogeneous ignition process of DME/air premixture is investigated. It is found that, apart from the low- and high-temperature chemistry which are essential in the typical two-stage ignition, the intermediate-temperature chemistry can also play an important role, especially for slow reaction process in fuel rich regions. Then, the effects of thermochemical conditions and molecular diffusion are assessed for non-premixed ignition process in the 1D diffusion layer. The results show that, the reaction front always initiates from local autoignition in most reactive regions; then it propagates either in sequential auto-ignition mode or in diffusion-driven mode as a deflagration wave. With various thermochemical conditions, the chemical kinetics behave differently and produce complex multibrachial (tetrabrachial, pentabrachial and hexbrachial) structures during the reaction front propagation. Decreasing the diffusion layer thickness generally delays the reaction front initiation but enhances its transition into a diffusion-driven flame. Finally, it is shown that 1D diffusion layer simulations can qualitatively reproduce the complex multibrachial structures in 1D counterflow and 2D coflow at certain conditions. A regime diagram is proposed to separate the effects of chemical kinetics, molecular diffusion, and convective transport.Keywords: non-premixed combustiondimethyl etherthree-stage ignitionintermediate-temperature chemistry Disclosure statementNo potential conflict of interest was reported by the author(s).Supplemental dataSupplemental data for this article can be accessed here https://doi.org/10.1080/13647830.2023.2261423.Additional informationFundingThis work is jointly supported by the National Natural Science Foundation of China (Nos. 52176096 and 51861135309) and the German Research Foundation (DFG, no. 411275182).
{"title":"Numerical study on three-stage ignition of dimethyl ether by hot air under engine-relevant conditions","authors":"Xinyi Chen, Zisen Li, Yiqing Wang, Wang Han, Arne Scholtissek, Peng Dai, Christian Hasse, Zheng Chen","doi":"10.1080/13647830.2023.2261423","DOIUrl":"https://doi.org/10.1080/13647830.2023.2261423","url":null,"abstract":"AbstractNon-premixed combustion often occurs in practical engines, and it is affected by the coupling effects of chemical kinetics and transport. This study aims to elucidate the individual effect of chemical kinetics, molecular diffusion, and convective transport on non-premixed combustion. To this end, three types of reactive systems are investigated by numerical simulations considering detailed chemistry and transport: (1) thermochemical system: 0D homogeneous autoignition, (2) thermochemical-diffusive system: 1D non-premixed ignition in a static diffusion layer, (3) thermochemical-diffusive-convective system: 1D non-premixed ignition in a counterflow and 2D lifted flame in a coflow. The simulations are carried out for diluted dimethyl ether and hot air under engine-relevant conditions with a pressure of 40 atm and hot air temperatures of 700∼1500 K. First, homogeneous ignition process of DME/air premixture is investigated. It is found that, apart from the low- and high-temperature chemistry which are essential in the typical two-stage ignition, the intermediate-temperature chemistry can also play an important role, especially for slow reaction process in fuel rich regions. Then, the effects of thermochemical conditions and molecular diffusion are assessed for non-premixed ignition process in the 1D diffusion layer. The results show that, the reaction front always initiates from local autoignition in most reactive regions; then it propagates either in sequential auto-ignition mode or in diffusion-driven mode as a deflagration wave. With various thermochemical conditions, the chemical kinetics behave differently and produce complex multibrachial (tetrabrachial, pentabrachial and hexbrachial) structures during the reaction front propagation. Decreasing the diffusion layer thickness generally delays the reaction front initiation but enhances its transition into a diffusion-driven flame. Finally, it is shown that 1D diffusion layer simulations can qualitatively reproduce the complex multibrachial structures in 1D counterflow and 2D coflow at certain conditions. A regime diagram is proposed to separate the effects of chemical kinetics, molecular diffusion, and convective transport.Keywords: non-premixed combustiondimethyl etherthree-stage ignitionintermediate-temperature chemistry Disclosure statementNo potential conflict of interest was reported by the author(s).Supplemental dataSupplemental data for this article can be accessed here https://doi.org/10.1080/13647830.2023.2261423.Additional informationFundingThis work is jointly supported by the National Natural Science Foundation of China (Nos. 52176096 and 51861135309) and the German Research Foundation (DFG, no. 411275182).","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135859159","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 : 2023-09-20DOI: 10.1080/13647830.2023.2260351
Abhilash M. Menon, Michael Oevermann, Alan R. Kerstein
LES–LEM is a simulation approach for turbulent combustion in which the stochastic Linear Eddy Model (LEM) is used for sub-grid mixing and combustion closure in Large-Eddy Simulation (LES). LEM resolves, along a one-dimensional line, all spatial and temporal scales, provides on-the-fly local turbulent flame statistics, captures finite rate chemistry effects and directly incorporates turbulence-chemistry interaction. However, the approach is computationally expensive as it requires advancing an LEM-line in each LES cell. This paper introduces a novel turbulent combustion closure model for LES using LEM to address this issue. It involves coarse-graining the LES mesh to generate a coarse- level ‘super-grid’ comprised of cell-clusters. Each cell-cluster, instead of each LES cell, then contains a single LEM domain. This domain advances the combined advection–reaction–diffusion solution and also provides suitably conditioned statistics for thermochemical scalars such as species mass fractions. Local LES-filtered thermochemical states are then obtained by probability-density-function (PDF) weighted integration of binned conditionally averaged scalars, akin to standard presumed PDF approaches for reactive LES but with physics-based determination of the full thermochemical state for particular values of the conditioning variables. The proposed method is termed ‘super-grid LEM’ or ‘SG-LEM’. The paper describes LEM reaction–diffusion advancement, the LEM representation of turbulent advection, a novel splicing algorithm (a key feature of LES–LEM) formulated for the super-grid approach, a wall treatment, and a thermochemical LES closure procedure. To validate the proposed model, a pressure-based solver was developed using the OpenFOAM library and tested on a premixed ethylene flame stabilised over a backward facing step, a setup for which some DNS data is available. SG-LEM provides high resolution flame structures, temperature and mass fractions suitable for LES thermochemical closure. Additionally, it provides reaction-rate data at the coarse level, a unique feature compared to other mapping-type closure methods. Quantitative comparisons are made between the proposed model and time-averaged DNS data, focussing on velocity, temperature and species mass fraction. Results show good agreement downstream of the step. Furthermore, comparison with an equivalent Partially-Stirred Reactor (PaSR) simulation demonstrates the superior predictive capability of SG-LEM. Additionally, the paper briefly examines the sensitivity of the model to coarse-graining parameters and finally, explores computational efficiency highlighting the substantial speedup achieved when compared to the standard LES–LEM approach with potentially significant speedup relative to PaSR closure for the intensely turbulent regimes of principal interest.
LES - LEM是一种湍流燃烧模拟方法，在大涡模拟(LES)中使用随机线性涡模型(LEM)进行亚网格混合和燃烧闭合。LEM可以沿一维线解析所有空间和时间尺度，提供实时的局部湍流火焰统计数据，捕获有限速率化学效应，并直接结合湍流-化学相互作用。然而，这种方法的计算成本很高，因为它需要在每个LES单元中推进一个lem线。为了解决这一问题，本文提出了一种新的紊流燃烧闭合模型。它涉及对LES网格进行粗粒度处理，以生成由细胞簇组成的粗级“超级网格”。然后，每个细胞簇，而不是每个LES细胞，都包含一个LEM域。该领域推进了对流-反应-扩散联合解决方案，并为热化学标量(如物种质量分数)提供了适当的条件统计。然后通过分类条件平均标量的概率-密度-函数(PDF)加权积分获得局部LES过滤的热化学状态，类似于反应性LES的标准假定PDF方法，但对特定条件变量值的完整热化学状态进行基于物理的确定。提出的方法被称为“超级网格LEM”或“SG-LEM”。本文描述了LEM反应扩散的进展，湍流平流的LEM表示，为超网格方法制定的一种新的拼接算法(LES - LEM的关键特征)，壁面处理和热化学LES闭合程序。为了验证所提出的模型，使用OpenFOAM库开发了一个基于压力的求解器，并在向后台阶上稳定的预混乙烯火焰上进行了测试，该设置提供了一些DNS数据。SG-LEM提供高分辨率火焰结构，温度和质量分数适合LES热化学封闭。此外，它还提供粗略级别的反应速率数据，这是与其他映射类型闭包方法相比的一个独特功能。将所提出的模型与时间平均DNS数据进行了定量比较，重点是速度、温度和物种质量分数。结果表明，该阶跃下游具有良好的一致性。此外，通过与等效部分搅拌反应器(PaSR)模拟的比较，验证了SG-LEM的优越预测能力。此外，本文简要地考察了模型对粗粒度参数的敏感性，最后探讨了计算效率，强调了与标准LES-LEM方法相比所实现的实质性加速，相对于主要利益强烈湍流状态的PaSR关闭可能有显着的加速。
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