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Numerical Modelling And Simulation Of Hydrogen Enriched Premixed Turbulent Flames With Rans And Les Approaches
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Book Synopsis Numerical Modelling and Simulation of Hydrogen Enriched Premixed Turbulent Flames with RANS and LES Approaches by : Bhuvaneswaran Manickam
Download or read book Numerical Modelling and Simulation of Hydrogen Enriched Premixed Turbulent Flames with RANS and LES Approaches written by Bhuvaneswaran Manickam and published by . This book was released on 2012 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Subfilter Scale Modelling for Large Eddy Simulation of Lean Hydrogen-enriched Turbulent Premixed Combustion by : Francisco Emanuel Hernandez Perez
Download or read book Subfilter Scale Modelling for Large Eddy Simulation of Lean Hydrogen-enriched Turbulent Premixed Combustion written by Francisco Emanuel Hernandez Perez and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Large Eddy Simulations of Premixed Turbulent Flame Dynamics by : Gaurav Kewlani
Download or read book Large Eddy Simulations of Premixed Turbulent Flame Dynamics written by Gaurav Kewlani and published by . This book was released on 2014 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: High efficiency, low emissions and stable operation over a wide range of conditions are some of the key requirements of modem-day combustors. To achieve these objectives, lean premixed flames are generally preferred as they achieve efficient and clean combustion. A drawback of lean premixed combustion, however, is that the flames are more prone to dynamics. The unsteady release of sensible heat and flow dilatation in combustion processes create pressure fluctuations which, particularly in premixed flames, can couple with the acoustics of the combustion system. This acoustic coupling creates a feedback loop with the heat release that can lead to severe thermoacoustic instabilities that can damage the combustor. Understanding these dynamics, predicting their onset and proposing passive and active control strategies are critical to large-scale implementation. For the numerical study of such systems, large eddy simulation (LES) techniques with appropriate combustion models and reaction mechanisms are highly appropriate. These approaches balance the computational complexity and predictive accuracy. This work, therefore, aims to explore the applicability of these methods to the study of premixed wake stabilized flames. Specifically, finite rate chemistry LES models that can effectively capture the interaction between different turbulent scales and the combustion fronts have been implemented, and applied for the analysis of premixed turbulent flame dynamics in laboratory-scale combustor configurations. Firstly, the artificial flame thickening approach, along with an appropriate reduced chemistry mechanism, is utilized for modeling turbulence-combustion interactions at small scales. A novel dynamic formulation is proposed that explicitly incorporates the influence of strain on flame wrinkling by solving a transport equation for the latter rather than using local-equilibrium-based algebraic models. Additionally, a multiple-step combustion chemistry mechanism is used for the simulations. Secondly, the presumed-PDF approach, coupled with the flamelet generated manifold (FGM) technique, is also implemented for modeling turbulence-combustion interactions. The proposed formulation explicitly incorporates the influence of strain via the scalar dissipation rate and can result in more accurate predictions especially for highly unsteady flame configurations. Specifically, the dissipation rate is incorporated as an additional coordinate to presume the PDF and strained flamelets are utilized to generate the chemistry databases. These LES solvers have been developed and applied for the analysis of reacting flows in several combustor configurations, i.e. triangular bluff body in a rectangular channel, backward facing step configuration, axi-symmetric bluff body in cylindrical chamber, and cylindrical sudden expansion with swirl, and their performance has been be validated against experimental observations. Subsequently, the impact of the equivalence ratio variation on flame-flow dynamics is studied for the swirl configuration using the experimental PIV data as well as the numerical LES code, following which dynamic mode decomposition of the flow field is performed. It is observed that increasing the equivalence ratio can appreciably influence the dominant flow features in the wake region, including the size and shape of the recirculation zone(s), as well as the flame dynamics. Specifically, varying the heat loading results in altering the dominant flame stabilization mechanism, thereby causing transitions across distinct- flame configurations, while also modifying the inner recirculation zone topology significantly. Additionally, the LES framework has also been applied to gain an insight into the combustion dynamics phenomena for the backward-facing step configuration. Apart from evaluating the influence of equivalence ratio on the combustion process for stable flames, the flame-flow interactions in acoustically forced scenarios are also analyzed using LES and dynamic mode decomposition (DMD). Specifically, numerical simulations are performed corresponding to a selfexcited combustion instability configuration as observed in the experiments, and it is observed that LES is able to suitably capture the flame dynamics. These insights highlight the effect of heat release variation on flame-flow interactions in wall-confined combustor configurations, which can significantly impact combustion stability in acoustically-coupled systems. The fidelity of the solvers in predicting the system response to variation in heat loading and to acoustic forcing suggests that the LES framework can be suitably applied for the analysis of flame dynamics as well as to understand the fundamental mechanisms responsible for combustion instability. KEY WORDS - large eddy simulation, LES, wake stabilized flame, turbulent premixed combustion, combustion modeling, artificially thickened flame model, triangular bluff body, backward facing step combustor, presumed-PDF model, flamelet generated manifold, axi-symmetric bluff body, cylindrical swirl combustor, particle image velocimetry, dynamic mode decomposition, combustion instability, forced response.
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 Large-eddy Simulation of Premixed Turbulent Combustion Using Flame Surface Density Approach by : Wen Lin
Download or read book Large-eddy Simulation of Premixed Turbulent Combustion Using Flame Surface Density Approach written by Wen Lin and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Numerical Simulation of Non-premixed Laminar and Turbulent Flames by Means of Flamelet Modelling Approaches by : Kilian Claramunt i Altimira
Download or read book Numerical Simulation of Non-premixed Laminar and Turbulent Flames by Means of Flamelet Modelling Approaches written by Kilian Claramunt i Altimira and published by . This book was released on 2005 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Direct Numerical Simulations of Premixed Turbulent Flame with Variable Density by : Songwei Zhang
Download or read book Direct Numerical Simulations of Premixed Turbulent Flame with Variable Density written by Songwei Zhang and published by . This book was released on 1994 with total page 292 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.
Book Synopsis Fundamentals of Premixed Turbulent Combustion by : Andrei Lipatnikov
Download or read book Fundamentals of Premixed Turbulent Combustion written by Andrei Lipatnikov and published by CRC Press. This book was released on 2012-10-24 with total page 551 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lean burning of premixed gases is considered to be a promising combustion technology for future clean and highly efficient gas turbine combustors. Yet researchers face several challenges in dealing with premixed turbulent combustion, from its nonlinear multiscale nature and the impact of local phenomena to the multitude of competing models. Filling a gap in the literature, Fundamentals of Premixed Turbulent Combustion introduces the state of the art of premixed turbulent combustion in an accessible manner for newcomers and experienced researchers alike. To more deeply consider current research issues, the book focuses on the physical mechanisms and phenomenology of premixed flames, with a brief discussion of recent advances in partially premixed turbulent combustion. It begins with a summary of the relevant knowledge needed from disciplines such as thermodynamics, chemical kinetics, molecular transport processes, and fluid dynamics. The book then presents experimental data on the general appearance of premixed turbulent flames and details the physical mechanisms that could affect the flame behavior. It also examines the physical and numerical models for predicting the key features of premixed turbulent combustion. Emphasizing critical analysis, the book compares competing concepts and viewpoints with one another and with the available experimental data, outlining the advantages and disadvantages of each approach. In addition, it discusses recent advances and highlights unresolved issues. Written by a leading expert in the field, this book provides a valuable overview of the physics of premixed turbulent combustion. Combining simplicity and topicality, it helps researchers orient themselves in the contemporary literature and guides them in selecting the best research tools for their work.
Book Synopsis High-fidelity Computation and Modeling of Turbulent Premixed Combustion by : Yunde Su
Download or read book High-fidelity Computation and Modeling of Turbulent Premixed Combustion written by Yunde Su and published by . This book was released on 2020 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: High-fidelity simulation of turbulent premixed combustion is desirable for the design of advanced energy-efficient and environmentally-friendly combustion engines. An attractive high-fidelity simulation approach that is applicable to practical combustion problems is the large eddy simulation (LES), in which the large-scale dynamics of flame-turbulence interaction are resolved down to a filter scale while the sub-filter phenomena are modeled. Since the grid size in practical LES is typically comparable to or larger than the flame front thickness, the filtered flame front is not well resolved when the filter size is taken as the grid size. Under such a condition, the spurious propagation of the filtered flame front can occur. To overcome this challenge, the front propagation formulation (FPF) method that was originally proposed to simulate propagating reaction fronts on under-resolved grids is extended to LES of turbulent premixed combustion. The closure of the regularized Dirac delta function, which FPF uses to minimize the spurious propagation, is investigated using direct numerical simulation (DNS) data for statistically planar premixed flames propagating in homogeneous isotropic turbulence. As a key ingredient in the sub-filter flame speed model that is required for the FPF method and many other combustion models, the flame wrinkling in the DNS dataset is studied in the context of fractals. The results show that, for the flames investigated in the DNS, the fractal dimension increases with the Reynolds number and the inner cut-off scale is on the order of the flame thickness. The FPF-LES framework is validated for a non-piloted Bunsen flame in the corrugated flamelet regime and a piloted Bunsen flame in the thin reaction zone regime. In both cases, the predicted results compare reasonably well with experimental measurements, demonstrating the performance of the FPF-LES framework. In LES of the non-piloted Bunsen flame, it is found that neglecting the stretch effects can cause the flame length and radius to be clearly under-predicted, which suggests the necessity to include stretch effects in LES. It is also found that the strain rate in the stretch effect model needs to be evaluated on the unburned side of the filtered flame to avoid the artificial modification of the flame wrinkling. Finally, the FPF-LES framework is applied to an experimentally studied spark-ignition (SI) engine with the emphasis on the prediction of cycle-to-cycle variations (CCVs), which are known to limit engine performance. To capture the degree of CCVs observed in the experiments, a laminar-to-turbulent flame transition model that describes the non-equilibrium sub-filter flame speed evolution during an early stage of flame kernel growth is developed. The multi-cycle LES with the proposed flame transition model under the FPF framework is found to reproduce experimentally-observed CCVs satisfactorily. The simulation results indicate the importance of modeling the laminar-to-turbulent flame transition and the effect of turbulence on the transition process, when predicting CCVs, under certain engine conditions.
Book Synopsis A Framework for Turbulent Non-premixed Combustion Modeling in OpenFoam by : Vasu Jaganath
Download or read book A Framework for Turbulent Non-premixed Combustion Modeling in OpenFoam written by Vasu Jaganath and published by . This book was released on 2020 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: Combustion remains a critical technology for electricity generation, heating, transportation and other industrial processes. Turbulent combustion lies at the heart of many of these processes. The accurate, robust and efficient computational modeling of turbulent combustion is necessary to design clean, efficient and safe combustion devices and processes. For practical combustion problems the direct numerical simulation (DNS) of the governing equations is computationally intractable. The Reynolds averaged Navier-Stokes simulation (RANS) and large eddy simulation (LES) techniques have emerged as powerful tools to simulate turbulent reacting flows. RANS and LES methodologies require closure of the unclosed terms arising from the averaging or filtering the governing equations. Even with adequate closure, RANS and LES remain computationally infeasible for simulating many combustion processes in engineering applications, further simplifications regarding flame thickness, flow and chemical reaction time scales are required. The high Damk\"{o}hler (Da) number flames can be modeled using a reduced chemistry model. A flamelet derived reduced chemistry model like Flamelet Generated Manifolds (FGM) accounts for finite rate chemistry while it greatly simplifies the simulation of turbulent combustion as it decouples the turbulent transport and flame structure. The interaction between the turbulence and the flame front in non-premixed combustion is described by the probability density function (PDF) of the composition variables. In this work, a framework for turbulent combustion modeling is presented for both RANS and, LES with FGM reduced chemistry model. This framework consists of implementation of presumed and transported PDF models and is developed within the open source CFD software OpenFOAM. The simulation of the well-known piloted methane-air jet flames (Sandia flames) is conducted in RANS context with both presumed and transported PDF models. An "A priori" analysis is conducted based on the RANS/TPDF simulation data. The analysis quantifies the extent of errors in PPDF models, specifically errors in choice of presumed PDF, statistical independence and the number moments and cross moments considered. A new PPDF model based on the Gaussian copula approach for correlation of the composition variables is developed and analyzed. The implementation of RANS/TPDF solver incorporates robust algorithms for particle tracking, position and number control. The LES/TFDF simulation of Sandia flame D is conducted to showcase the capability of the developed framework.
Book Synopsis Utilization of Ammonia as an Alternate Fuel in Army Aircraft Engines by : Nicholas C. Kailos
Download or read book Utilization of Ammonia as an Alternate Fuel in Army Aircraft Engines written by Nicholas C. Kailos and published by . This book was released on 1966 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Numerical Modelling of Compressible Turbulent Premixed Hydrogen Flames by : Charles Turquand D'Auzay
Download or read book Numerical Modelling of Compressible Turbulent Premixed Hydrogen Flames written by Charles Turquand D'Auzay and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Turbulence And Combustion by : Vadim Rostislavovich Kuznet͡sov
Download or read book Turbulence And Combustion written by Vadim Rostislavovich Kuznet͡sov and published by CRC Press. This book was released on 1990-01-01 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: Investigates the turbulent combustion of gases as well as a variety of problems relating to the theory of turbulence. This book sytematizes derivation methods and closure of equations for probability distributions.
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 LES Modelling of Non-premixed and Partially Premixed Turbulent Flames by : S. K. Sadasivuni
Download or read book LES Modelling of Non-premixed and Partially Premixed Turbulent Flames written by S. K. Sadasivuni and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A large eddy simulation (LES) model has been developed and validated for turbulent non-premixed and partially premixed combustion systems. LES based combustion modelling strategy has the ability to capture the detailed structure of turbulent flames and account for the effects of radiation heat loss. Effects of radiation heat loss ismodelled by employing an enthalpy-defect based non-adiabatic flamelet model (NAFM) in conjunction with a steady non-adiabatic flamelet approach. The steady laminar flamelet model (SLFM) is used with multiple flamelet solutions through thedevelopment of pre-integrated look up tables. The performance of the non-adiabatic model is assessed against experimental measurements of turbulent CH4/H2 bluff-body stabilized and swirl stabilized jet flames carried out by the University of Sydney combustion group. Significant enhancements in the predictions of mean thermal structure have been observed with both bluff body and swirl stabilized flames by the consideration of radiation heat loss through the non-adiabatic flamelet model. In particular, mass fractions of product species like CO2 and H2O have been improved with the consideration of radiation heat loss. From the Sydney University data the HM3e flame was also investigated withSLFM using multiple flamelet strategy and reasonably fair amount of success has been achieved. In this work, unsteady flamelet/progress variable (UFPV) approach based combustion model which has the potential to describe both non-premixed and partially premixed combustion, has been developed and incorporated in an in-house LES code. The probability density function (PDF) for reaction progress variable and scalardissipation rate is assumed to follow a delta distribution while mixture fraction takes the shape of a beta PDF. The performance of the developed model in predicting the thermal structure of a partially premixed lifted turbulent jet flame in vitiated co-flow has been evaluated. The UFPV model has been found to successfully predict the flame lift-off, in contrast SLFM results in a false attached flame. The mean lift-off height is however over-predicted by UFPV-? function model by ~20% for methane based flame and under-predicted by ~50% for hydrogen based flame. The form of thePDF for the reaction progress variable and inclusion of a scalar dissipation rate thusseems to have a strong influence on the predictions of gross characteristics of the flame. Inclusion of scalar dissipation rate in the calculations appears to be successful in predicting the flame extinction and re-ignition phenomena. The beta PDFdistribution for the reaction progress variable would be a true prospect for extending the current simulation to predict the flame characteristics to a higher degree.
