Computationally-efficient and Scalable Implementation of Chemistry in Large-scale Simulations of Turbulent Combustion PDF Download

Author: Varun Hiremath
Publisher:
ISBN:
Category :
Languages : en
Pages : 566

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Book Description
A major challenge in the numerical simulations of turbulent reacting flows involving large numbers of chemical species and reactions is the accurate and computationally-efficient representation of combustion chemistry. Recent advances on the experimental and theoretical fronts of the study of real fuel chemistry have led to more accurate chemical mechanisms of real fuels involving hundreds to thousands of species and thousands of reactions. However, the direct use of such detailed chemistry in large-scale calculations of turbulent reacting flows still remains computationally prohibitive. In our work, we focus on the combined Large-Eddy Simulation (LES)/Probability Density Function (PDF) computations of turbulent reacting flows, in which the thermochemical composition of the fluid is represented by a large number of particles. To reduce the cost of chemistry calculations in large-scale LES/PDF computations, we have developed a combined dimension reduction and tabulation approach in which the chemistry is represented accurately and efficiently in terms of a reduced number of "represented species". In this combined approach, the dimension reduction of combustion chemistry is performed using the Rate-Controlled Constrained-Equilibrium (RCCE) method, followed by tabulation using the In Situ Adaptive Tabulation (ISAT) algorithm. An automated Greedy Algorithm with Local Improvement (GALI) has been developed for selecting good rep- resented species for use in this approach. In addition, we have developed a Partitioned Uniform Random (P-URAN) parallel strategy for the efficient parallel implementation of chemistry in large-scale LES/PDF simulations on multiple cores. This strategy has been tested by performing full-scale LES/PDF simulations of the Sandia Flame D turbulent jet flame on up to 9,216 cores and it is found to achieve good scaling. In this work (1) we describe in detail the implementation of ISAT/RCCE/GALI and the P-URAN parallel strategy; (2) we show that the combined ISAT/RCCE/GALI yields orders of magnitude speed-up with very good error control; (3) we demonstrate that our implementation of RCCE is an accurate, efficient and robust implementation; (4) we show that the P-URAN parallel strategy achieves over 85% relative weak scaling efficiency and around 60% relative strong scaling efficiency on up to 9,216 cores; (5) we show that the combined ISAT/RCCE methodology with P-URAN significantly reduces the simulation time; and (6) a combination of ISAT/RCCE and PURAN algorithms enables us to perform accurate and computationally-efficient large-scale LES/PDF simulations with real fuel chemistry involving hundreds of chemical species.

Author: Ashish Shireeshkumar Newale
Publisher:
ISBN:
Category :
Languages : en
Pages : 191

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Book Description
There is a time critical need for design of fossil fuel based energy conversion devices that attain the dual and usually competing objectives of high efficiency and low pollutant emissions. The design of such devices can be informed by, and in certain instances derived from predictive computations. A crucial component of reacting flow simulations that are predictive is the turbulent combustion model. Probability density function (PDF) methods have been shown to accurately capture flames with strong turbulence chemistry interactions. However, PDF methods are known to be more computationally intensive than simpler topology based approaches such as steady laminar flamelet models. The recently proposed pre-partitioned adaptive chemistry (PPAC) methodology mitigates the cost of using particle PDF methods while maintaining their accuracy. PPAC generates a set of reduced models in an offline preprocessing stage, which are then dynamically utilized at runtime for integrating particle compositions. In the first part of this work, PPAC is augmented by combining it with complementary dimension reduction (rate-controlled constrained equilibrium (RCCE)) and storage retrieval methods (in-situ adaptive tabulation (ISAT)). The combined PPAC-RCCE-ISAT method is shown to outperform standalone PPAC by avoiding redundant direct integrations leading to a significant reduction in the CPU cost, and achieving a sizable reduction in the memory requirement by retaining fewer variables at runtime. Though PPAC has been developed for reducing the computational cost of particle PDF computations, it had previously been tested only in a partially stirred reactor (PaSR). Consequently, an integrated PPAC (-ISAT) particle PDF solver is developed as part of the current work. A detailed assessment of PPAC and PPAC-ISAT in LES/PDF simulations of turbulent combustion is completed using the developed solver. For a large-scale simulation of Sandia flame D, the coupled PPAC-ISAT particle PDF solver is shown to reduce the average wall clock time of a standalone ISAT implementation using the detailed mechanism by 39%, with a minimal loss of accuracy. A key assumption made in the PPAC framework is that the compositions used in the offline preprocessing stage are representative of those encountered at runtime. Hence, the efficient generation of a representative database is crucial to the success of PPAC. The suitability of existing canonical 0D-1D reactors is examined for this purpose. Specifically, compositions obtained from these canonical reactors are compared to the compositions extracted from a variety of direct numerical simulations using an ISAT based approach. We show that the compositions obtained from 1D counterflow flames and PaSR are representative of a significant fraction of the compositions encountered in turbulent combustion simulations. To directly quantify the impact of using databases generated from canonical 0D-1D reactors, we use the coupled PPAC-ISAT particle PDF solver for performing LES/PDF simulations of Sandia flame D. We explore two databases: a first one generated using compositions extracted from 1D counterflow flames, and a second one using compositions from a PaSR. We show that the use of these efficiently generated databases leads to results that are comparable to the case where the database is comprised of compositions extracted from the LES/PDF simulation itself. Finally, avenues for further research that can significantly improve the utility of PPAC for enabling computationally-efficient and accurate particle PDF computations are identified.

Author: Daniel Livescu
Publisher: Springer Nature
ISBN: 9811526435
Category : Technology & Engineering
Languages : en
Pages : 273

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Book Description
This book highlights recent research advances in the area of turbulent flows from both industry and academia for applications in the area of Aerospace and Mechanical engineering. Contributions include modeling, simulations and experiments meant for researchers, professionals and students in the area.

Author: Tarek Echekki
Publisher: Springer Science & Business Media
ISBN: 9400704127
Category : Technology & Engineering
Languages : en
Pages : 496

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Book Description
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.

Author: Akshai K. Runchal
Publisher: Springer
ISBN: 9811074739
Category : Technology & Engineering
Languages : en
Pages : 499

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Book Description
This research book provides state-of-the-art advances in several areas of energy generation from, and environmental impact of, fuels and biofuels. It also presents novel developments in the areas of biofuels and products from various feedstock materials along with thermal management, emission control and environmental issues. Availability of clean and sustainable energy is of paramount importance in all applications of energy, power, mobility and propulsion. This book is written by internationally renowned experts from around the globe. They provide the latest innovations in cleaner energy utilization for a wide range of devices. The energy and environment sustainability requires a multipronged approach involving development and utilization of new and renewable fuels, design of fuel-flexible combustion systems and novel and environmentally friendly technologies for improved fuel use. This book serves as a good reference for practicing engineers, educators and research professionals.

Author: Andrea Donini
Publisher: Andrea Donini
ISBN: 9038636199
Category :
Languages : en
Pages : 173

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Book Description
In spite of the increasing presence of renewable energy sources, fossil fuels will remain the primary supply of the world's energy needs for the upcoming future. Modern gas-turbine based systems represent one of the most efficient large-scale power generation technology currently available. Alongside this, gas-turbine power plants operate with very low emissions, have flexible operational characteristics and are able to utilize a broad range of fuels. It is expected that gas-turbine based plants will play an important role as an effective means of converting combustion energy in the future as well, because of the vast potential energy savings. The numerical approach to the design of complex systems such as gas-turbines has gained a continuous growth of interest in the last few decades. This because simulations are foreseen to provide a tremendous increase in the combustor efficiency, fuel-flexibility and quality over the next future. In this dissertation, an advanced turbulent combustion technique is implemented and progressively developed for the simulation of all the features that are typically observed in stationary gas-turbine combustion, including hydrogen as a fuel. The developed turbulent combustion model retains most of the accuracy of a detailed simulation while drastically reducing its computational time. As a result of this work, the advancement of power generation plants can be accelerated, paving the way for future developments of alternative fuel usage in a cleaner and more efficient combustion.

Author:
Publisher: ScholarlyEditions
ISBN: 1490106669
Category : Technology & Engineering
Languages : en
Pages : 1190

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Book Description
Issues in Energy Conversion, Transmission, and Systems: 2013 Edition is a ScholarlyEditions™ book that delivers timely, authoritative, and comprehensive information about Additional Research. The editors have built Issues in Energy Conversion, Transmission, and Systems: 2013 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Additional Research in this book to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in Energy Conversion, Transmission, and Systems: 2013 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.

Author: Chao Xu
Publisher:
ISBN:
Category : Combustion
Languages : en
Pages : 182

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Book Description
Three approaches toward efficient and predictive turbulent combustion modeling are investigated in this dissertation. The first approach focuses on the development of locally reduced chemistry and advanced solvers for efficient time integration of stiff chemical kinetic systems. In particular, a numerical technique using dynamic adaptive chemistry (DAC) with splitting schemes is developed and demonstrated in one-dimensional (1-D) premixed flames. A sparse stiff chemistry solver based on dynamic adaptive hybrid integration (AHI) and sparse matrix techniques (AHI-S), and an iterative uncoupled quasi-steady-state (IU-QSS) method for improved stability of explicit solvers, are further developed and shown to be more computationally efficient than other chemistry solvers in various flame configurations. In the second approach, a computational diagnostic tool, namely the chemical explosive mode analysis (CEMA), is extended to account for the interactions between chemical reactions and transport processes. Different local combustion modes, including the auto-ignition, diffusion-assisted ignition, and extinction modes, are demarcated by projecting the chemical and transport source terms to the chemical explosive mode. A criterion based on the local combustion modes is proposed to distinguish between two premixed flame propagation modes, that is the auto-ignition and diffusion-controlled deflagration waves, respectively. The new criterion is validated in 1-D premixed flames and 2-D homogeneous charge compression ignition (HCCI) systems. CEMA-based diagnostics are then employed to investigate the local structures of strongly turbulent premixed n-dodecane flames, and to understand the propagation modes and stabilization mechanisms of a turbulent lifted dimethyl ether (DME) jet flame, based on direct numerical simulation (DNS) data. The third approach is to construct a dynamic adaptive combustion modeling framework for turbulent flames that involve both premixed and non-premixed features. CEMA is adopted as a flame segmentation tool, and appropriate sub-models are assigned on-the-fly to different flame zones. The proposed modeling framework is tested in a turbulent lifted n-dodecane spray flame using large eddy simulations (LES). The new model is found to predict the ignition delay and lift-off length more accurately compared with the low-cost flamelet models, while the overall computational cost can be substantially reduced compared with the high-cost regime-independent models that incorporate finite rate chemistry.

Author: Pushan Sharma
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
In this time of severe climate change, there is an increasing need for sophisticated simulation tools to facilitate more efficient fossil-fuel based combustion devices with low pollutant and greenhouse gas emissions. In particular, to simulate a turbulent reacting flow, a proper prediction of the interactions between turbulence and chemistry is extremely important. Probability density function (PDF) methods have been shown to capture this strong turbulence chemistry interaction accurately. However, one of the biggest disadvantages of PDF methods is its significantly higher computational cost of solving the chemistry in its exact form compared to other simpler methods, such as flamelet-based models. This necessitates the development of strategies to reduce the cost of PDF type approaches without losing the level of accuracy. Two different categories of techniques to accelerate the process are explored in this thesis. The use of analytical Jacobian is observed to be a promising step to accelerate the chemistry source term integration compared to using numerical Jacobian. Here, a generalized projection-based analytical Jacobian framework is provided that considers all species mass fractions and temperature in the state vector while satisfying the mass conservation constraint consistently. The use of a projection matrix with the analytical Jacobian ensures that the mass fraction vector never goes off its realizable simplex, defined by the constraint, at any time step. This approach provides an accurate solution with different types of solvers, and also predicts the spectral properties of the corresponding dynamical system within round-off errors. Next, the algorithm for generating the analytical Jacobian is combined with a dimension reduction technique, the quasi-steady species (QSS) assumption. An automated algorithm package is developed, which provides the analytical expression of the Jacobian with QSS species, properly integrating all the additional derivatives corresponding to the QSS-derived algebraic expressions, and can be readily implemented in any high-fidelity turbulent simulation. Combining these two techniques (analytical Jacobian and QSS) has shown a significant reduction in the computational cost of a partially stirred reactor (PaSR) simulation. Adaptive chemistry approaches, which tailor the fidelity and size of the kinetic models used for reaction integration to the local flame conditions, have reduced the cost of PDF-type methods due to their ability to accurately describe the relevant combustion kinetics with significantly fewer variables and equations. In this work, two new adaptive chemistry algorithms are developed. The first addresses a key challenge of efficiently capturing the secondary chemistry pathways, such as pollutant formation, in an existing pre-partitioned adaptive chemistry (PPAC) approach. This new algorithm, PPAC-Additive, decouples the secondary chemistry from primary chemistry pathways (fuel oxidation), thus developing smaller reduced kinetic models compared to PPAC. In PPAC-Additive, the reduced models are generated first for main oxidation targets only, and then the important secondary pathways, demonstrated with NOx prediction, are dealt with afterwards in a separate stage. Both PPAC and PPAC-Additive generate the reduced models based on a sample set of compositions in an offline stage, which are then used adaptively during the simulation of interest. In contrast to the current adaptive frameworks, which require extensive pre-processing analysis and assumption, the second algorithm, dynamically partitioned adaptive chemistry (DPAC), is a completely stand-alone adaptive approach with limited need for user input. DPAC generates the reduced models during the adaptive simulation based on the encountered compositions at runtime. DPAC updates the reduced kinetic models continuously as the flame and its compositions evolve in time, making it more flexible and efficient than other existing adaptive ...

Author: Arie Shoshani
Publisher: CRC Press
ISBN: 1420069810
Category : Computers
Languages : en
Pages : 592

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Book Description
Dealing with the volume, complexity, and diversity of data currently being generated by scientific experiments and simulations often causes scientists to waste productive time. Scientific Data Management: Challenges, Technology, and Deployment describes cutting-edge technologies and solutions for managing and analyzing vast amounts of data, helping