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Investigation Of Conditional Source Term Estimation Approach To Modelling Mild Combustion
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Book Synopsis Investigation of Conditional Source-term Estimation Approach to Modelling Mild Combustion by : Jeffrey Labahn
Download or read book Investigation of Conditional Source-term Estimation Approach to Modelling Mild Combustion written by Jeffrey Labahn and published by . This book was released on 2016 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conditional Source-term Estimation (CSE) is a turbulent combustion model which uses conditional averages to provide closure for the mean chemical source term and is based on the same ideas as the Conditional Moment Closure (CMC) approach. CSE applies first order closure for the conditional averages which are obtained by inverting an integral equation and has been used to simulate a range of premixed, non-premixed and partially premixed flames. In the present study, CSE is applied to investigate a high efficient, low emission combustion process called Moderate and Intense Low Oxygen Dilution (MILD) combustion. This work represents the first application of CSE for MILD combustion, the first application of a multi-stream CSE formulation and the first doubly-conditioned CSE formulation applied in the Large Eddy Simulation (LES) framework. The objectives of the present study are to i) investigate the CSE combustion model for turbulent non-premixed combustion, ii) develop a CSE formulation for MILD combustion problems, iii) implement CSE for MILD combustion problems in Reynolds-Averaged Navier-Stokes (RANS) and LES and iv) compare the CSE predictions to experimental and previous numerical results for well documented MILD combustion flames. Numerical simulations of a confined non-premixed methane flame are completed using the CSE non-premixed approach. This study investigates the sensitivity to various CSE model parameters and shows CSE is able to accurately predict non-premixed methane combustion. A detailed study of the inversion problem encountered in CSE is also investigated using the Bayesian framework. The origin of the perturbation seen in the unconditional mass fraction in CSE and the impact of a smoothing prior on the recovered solution and credible intervals are discussed. Different regularization methods are studied and it is shown that both zeroth and first order Tikhonov are promising regularization methods for CSE. In the present work, the non-premixed CSE formulation is extended to include the impact of radiation of the conditional reaction rates and is applied to a semi-industrial furnace. This study demonstrates that a RANS-CSE simulation is able to accurately predict the temperature and species concentration, including NOx, for large scale realistic furnace configurations. Finally, a multi-stream CSE formulation is developed and applied to the DJHC burners in the RANS and LES framework. This new CSE formulation is able to predict the temperature and velocity profiles in very good agreement with the experimental data. Further, the LES multi-stream CSE formulation is able to predict the time-dependent nature of the DHJC burners.
Book Synopsis Investigation of Conditional Source-term Estimation Approach for Turbulent Partially Premixed Combustion Modelling by : Daniele Dovizio
Download or read book Investigation of Conditional Source-term Estimation Approach for Turbulent Partially Premixed Combustion Modelling written by Daniele Dovizio and published by . This book was released on 2015 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conditional Source-term Estimation (CSE) is a closure technique for modelling turbulent combustion phenomena. CSE uses the Conditional Moment Closure (CMC) hypothesis for closing chemical source terms: conditionally averaged chemical source terms are closed by conditional averaged scalars, which are obtained by inverting an integral equation, instead of solving transport equations (as in CMC). Since CSE has been successfully applied to both premixed and non-premixed configurations, it represents an attractive method for dealing with the more general and complex case of partially premixed combustion. The objectives of the present study are to (i) consolidate the premixed formulation of CSE through numerical simulations of a turbulent bluff body premixed flame; (ii) formulate, implement and test the Doubly conditional CSE (DCSE) in the context of partially premixed combustion; (iii) compare the DCSE predictions with well documented turbulent partially premixed flames. The canonical example of partially premixed flames is represented by turbulent lifted flames. A series of lifted turbulent jet flames is investigated in RANS by using DCSE. The DCSE calculations are successful in predicting the lift-off heights at three different conditions and reproducing many aspects of the flame structure in agreement with the experimental observations. The current results show that important aspects of the stabilization mechanism can be reproduced by the DCSE combustion model. The applicability of DCSE is further evaluated by applying this approach to a series of turbulent V-shaped flames for which experimental data is available. Premixed and stratified conditions are investigated. Overall, the agreement between numerical results and experimental findings is good, demonstrating the capability of DCSE to deal with partially premixed combustion. Future work includes implementation of CSE in LES and investigation of different fuels such as propane and biofuels.
Book Synopsis Conditional Source-term Estimation Methods for Turbulent Reacting Flows by :
Download or read book Conditional Source-term Estimation Methods for Turbulent Reacting Flows written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Conditional Source-term Estimation (CSE) methods are used to obtain chemical closure in turbulent combustion simulation. A Laminar Flamelet Decomposition (LFD) and then a Trajectory Generated Low-Dimensional Manifold (TGLDM) method are combined with CSE in Reynolds-Averaged Navier Stokes (RANS) simulation of non-premixed autoigniting jets. Despite the scatter observed in the experimental data, the predictions of ignition delay from both methods agree reasonably well with the measurements. The discrepancy between predictions of these two methods can be attributed to different ways of generating libraries that contain information of detailed chemical mechanism. The CSE-TGLDM method is recommended for its seemingly better performance and its ability to transition from autoignition to combustion. The effects of fuel composition and injection parameters on ignition delay are studied using the CSE-TGLDM method. The CSE-TGLDM method is then applied in Large Eddy Simulation of a non-premixed, piloted jet flame, Sandia Flame D. The adiabatic CSE-TGLDM method is extended to include radiation by introducing a variable enthalpy defect to parameterize TGLDM manifolds. The results are compared to the adiabatic computation and the experimental data. The prediction of NO formation is improved, though the predictions of temperature and major products show no significant difference from the adiabatic computation due to the weak radiation of the flame. The scalar fields are then extracted and used to predict the mean spectral radiation intensities of the flame. Finally, the application of CSE in turbulent premixed combustion is explored. A product-based progress variable is chosen for conditioning. Presumed Probability Density Function (PDF) models for the progress variable are studied. A modified version of a laminar flame-based PDF model is proposed, which best captures the distribution of the conditional variable among all PDFs under study. A priori tests are performed with the CSE.
Book Synopsis MILD Combustion: Modelling Challenges, Experimental Configurations and Diagnostic Tools by : Alessandro Parente
Download or read book MILD Combustion: Modelling Challenges, Experimental Configurations and Diagnostic Tools written by Alessandro Parente and published by Frontiers Media SA. This book was released on 2021-11-26 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Combustion Modelling in Spark-ignition Engines Using Conditional Source-term Estimation by : Girish Venkata Nivarti
Download or read book Combustion Modelling in Spark-ignition Engines Using Conditional Source-term Estimation written by Girish Venkata Nivarti and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fundamentals of Low Emission Flameless Combustion and Its Applications by : Seyed Ehsan Hosseini
Download or read book Fundamentals of Low Emission Flameless Combustion and Its Applications written by Seyed Ehsan Hosseini and published by Academic Press. This book was released on 2022-07-30 with total page 668 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamentals of Low Emission Flameless Combustion and Its Applications is a comprehensive reference on the flameless combustion mode and its industrial applications, considering various types of fossil and alternative fuel. Several experimental and numerical accomplishments on the fundamentals of state-of-the-art flameless combustion is presented, working to clarify the environmentally friendly aspects of this combustion mode. Author Dr. Hosseini presents the latest progresses in the field and highlights the most important achievements since invention, including the fundamentals of thermodynamics, heat transfer and chemical kinetics. Also analyzed is fuel consumption reduction and the efficiency of the system, emissions formation and the effect of the flameless mode on emission reduction.This book provides a solid foundation for those in industry employing flameless combustion for energy conservation and the mitigation of pollutant emissions. It will provide engineers and researchers in energy system engineering, chemical engineering, industrial engineers and environmental engineering with a reliable resource on flameless combustion and may also serve as a textbook for senior graduate students. Presents the fundamentals of flameless combustion and covers advances since its invention Includes experimental and numerical investigations of flameless combustion Analyzes emission formation and highlights the effects of the flameless mode on emission reduction
Book Synopsis Conditional Source-term Estimation for Diesel Combustion by : Riyaz Ismail
Download or read book Conditional Source-term Estimation for Diesel Combustion written by Riyaz Ismail and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Advanced Turbulent Combustion Physics and Applications by : N. Swaminathan
Download or read book Advanced Turbulent Combustion Physics and Applications written by N. Swaminathan and published by Cambridge University Press. This book was released on 2022-01-06 with total page 485 pages. Available in PDF, EPUB and Kindle. Book excerpt: Explore a thorough overview of the current knowledge, developments and outstanding challenges in turbulent combustion and application.
Book Synopsis Modeling of Turbulent Mixing in Combustion LES by : Abhishek Jain
Download or read book Modeling of Turbulent Mixing in Combustion LES written by Abhishek Jain and published by . This book was released on 2017 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current work focusses on investigating previously formulated subfilter mixing models for scalar variance and dissipation prediction in large eddy simulation (LES) of turbulent reacting flows. Three different models based on the local equilibrium assumption (Pierce, C. D., & Moin, P. Physics of Fluids (10), 3041, 1998), the second-moment transport equation (STE), and the variance transport equation (VTE) (Kaul, C. M. et al. Proceedings of the Combustion Institute (34), 1289-1297, 2013) are assessed. The emphasis of the investigation is placed on the effects of the discretization errors on the prediction of sub-filter variance and scalar dissipation rates. Estimation of subfilter quantities is a crucial procedure for LES. Among other subfilter quantities, the subfilter variance of the mixture fraction is particularly important for LES of non-premixed combustion because of the role it plays in the prediction of mixing of the fuel and co-flow at the molecular level. Previous works have assumed an equilibrium between the production and dissipation of the variance at these subfilter scales, and models based on this assumption have been developed with dynamic estimation of a model constant. Recent works have focused on eliminating this assumption of local equilibrium of production and dissipation of variance. Two of these approaches were studied and implemented for a non-premixed flame and their results are compared. In the first approach, the subfilter variance was calculated by solving the transport equation for the second moment of the mixture fraction (STE). The second approach solved the transport equation for the subfilter scalar variance itself (VTE). Both models incorporate the same modeled quantity for the scalar dissipation rate. It is seen from the results that the STE approach substantially overpredicts the subfilter variance. This discrepancy is attributed to the error generated due to the discrete version of the product rule for differentiation that is used when deriving the equation for the subfilter variance from the second and first moment transport equation for the mixture fraction. This error acts as an artificial source term and results in the overprediction of the subfilter variance in the STE approach. The contribution of this artificial source term is found to be much larger than that of the actual production term. Due to this susceptible nature of the STE approach to numerical errors, it is suggested to calculate the subfilter variance by solving a transport equation for it, i.e., the VTE approach. A dynamic approach for the model coefficient of the subfilter scalar dissipation in the VTE approach is also implemented. This model is used to simulate the Sandia Flame D with a 1-D Conditional Moment Closure (CMC) combustion model. The results show satisfactory agreement with experimental data.
Book Synopsis Turbulent Combustion Modeling by : Tarek Echekki
Download or read book Turbulent Combustion Modeling written by Tarek Echekki and published by Springer Science & Business Media. This book was released on 2010-12-25 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent combustion sits at the interface of two important nonlinear, multiscale phenomena: chemistry and turbulence. Its study is extremely timely in view of the need to develop new combustion technologies in order to address challenges associated with climate change, energy source uncertainty, and air pollution. Despite the fact that modeling of turbulent combustion is a subject that has been researched for a number of years, its complexity implies that key issues are still eluding, and a theoretical description that is accurate enough to make turbulent combustion models rigorous and quantitative for industrial use is still lacking. In this book, prominent experts review most of the available approaches in modeling turbulent combustion, with particular focus on the exploding increase in computational resources that has allowed the simulation of increasingly detailed phenomena. The relevant algorithms are presented, the theoretical methods are explained, and various application examples are given. The book is intended for a relatively broad audience, including seasoned researchers and graduate students in engineering, applied mathematics and computational science, engine designers and computational fluid dynamics (CFD) practitioners, scientists at funding agencies, and anyone wishing to understand the state-of-the-art and the future directions of this scientifically challenging and practically important field.
Book Synopsis Numerical Simulation of Turbulent Premixed Flames with Conditional Source-term Estimation by : Mohammad Mahdi Salehi
Download or read book Numerical Simulation of Turbulent Premixed Flames with Conditional Source-term Estimation written by Mohammad Mahdi Salehi and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Conditional Source-term Estimation Evaluations for Partially-premixed Flames by : Nikola Sekularac
Download or read book Conditional Source-term Estimation Evaluations for Partially-premixed Flames written by Nikola Sekularac and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Application of Conditional Source-term Estimation to Two Turbulent Non-premixed Methanol Flames by :
Download or read book Application of Conditional Source-term Estimation to Two Turbulent Non-premixed Methanol Flames written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Turbulent Premixed Flames by : Nedunchezhian Swaminathan
Download or read book Turbulent Premixed Flames written by Nedunchezhian Swaminathan and published by Cambridge University Press. This book was released on 2011-04-25 with total page 447 pages. Available in PDF, EPUB and Kindle. Book excerpt: A work on turbulent premixed combustion is important because of increased concern about the environmental impact of combustion and the search for new combustion concepts and technologies. An improved understanding of lean fuel turbulent premixed flames must play a central role in the fundamental science of these new concepts. Lean premixed flames have the potential to offer ultra-low emission levels, but they are notoriously susceptible to combustion oscillations. Thus, sophisticated control measures are inevitably required. The editors' intent is to set out the modeling aspects in the field of turbulent premixed combustion. Good progress has been made on this topic, and this cohesive volume contains contributions from international experts on various subtopics of the lean premixed flame problem.
Book Synopsis Modeling and Simulation of Turbulent Combustion by : Santanu De
Download or read book Modeling and Simulation of Turbulent Combustion written by Santanu De and published by Springer. This book was released on 2017-12-12 with total page 663 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive review of state-of-the-art models for turbulent combustion, with special emphasis on the theory, development and applications of combustion models in practical combustion systems. It simplifies the complex multi-scale and nonlinear interaction between chemistry and turbulence to allow a broader audience to understand the modeling and numerical simulations of turbulent combustion, which remains at the forefront of research due to its industrial relevance. Further, the book provides a holistic view by covering a diverse range of basic and advanced topics—from the fundamentals of turbulence–chemistry interactions, role of high-performance computing in combustion simulations, and optimization and reduction techniques for chemical kinetics, to state-of-the-art modeling strategies for turbulent premixed and nonpremixed combustion and their applications in engineering contexts.
Book Synopsis Source Term Evaluation for Combustion Modeling by : Myles A. Sussman
Download or read book Source Term Evaluation for Combustion Modeling written by Myles A. Sussman and published by . This book was released on 1993 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Turbulent Combustion by : Norbert Peters
Download or read book Turbulent Combustion written by Norbert Peters and published by Cambridge University Press. This book was released on 2000-08-15 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: The combustion of fossil fuels remains a key technology for the foreseeable future. It is therefore important that we understand the mechanisms of combustion and, in particular, the role of turbulence within this process. Combustion always takes place within a turbulent flow field for two reasons: turbulence increases the mixing process and enhances combustion, but at the same time combustion releases heat which generates flow instability through buoyancy, thus enhancing the transition to turbulence. The four chapters of this book present a thorough introduction to the field of turbulent combustion. After an overview of modeling approaches, the three remaining chapters consider the three distinct cases of premixed, non-premixed, and partially premixed combustion, respectively. This book will be of value to researchers and students of engineering and applied mathematics by demonstrating the current theories of turbulent combustion within a unified presentation of the field.
