Author: Yuri Paixao De AlmeidaPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Large Eddy Simulation of Supersonic Combustion Using a Probability Density Function Method
Author: Yuri Paixao De AlmeidaLarge-eddy Simulations of Scramjet Engines
Author: Heeseok KooPublisher:
ISBN:
Category :
Languages : en
Pages : 398
Book Description
The main objective of this dissertation is to develop large-eddy simulation (LES) based computational tools for supersonic inlet and combustor design. In the recent past, LES methodology has emerged as a viable tool for modeling turbulent combustion. LES computes the large scale mixing process accurately, thereby providing a better starting point for small-scale models that describe the combustion process. In fact, combustion models developed in the context of Reynolds-averaged Navier Stokes (RANS) equations exhibit better predictive capability when used in the LES framework. The development of a predictive computational tool based on LES will provide a significant boost to the design of scramjet engines. Although LES has been used widely in the simulation of subsonic turbulent flows, its application to high-speed flows has been hampered by a variety of modeling and numerical issues. In this work, we develop a comprehensive LES methodology for supersonic flows, focusing on the simulation of scramjet engine components. This work is divided into three sections. First, a robust compressible flow solver for a generalized high-speed flow configuration is developed. By using carefully designed numerical schemes, dissipative errors associated with discretization methods for high-speed flows are minimized. Multiblock and immersed boundary method are used to handle scramjet-specific geometries. Second, a new combustion model for compressible reactive flows is developed. Subsonic combustion models are not directly applicable in high-speed flows due to the coupling between the energy and velocity fields. Here, a probability density function (PDF) approach is developed for high-speed combustion. This method requires solution to a high dimensional PDF transport equation, which is achieved through a novel direct quadrature method of moments (DQMOM). The combustion model is validated using experiments on supersonic reacting flows. Finally, the LES methodology is used to study the inlet-isolator component of a dual-mode scramjet. The isolator is a critical component that maintains the compression shock structures required for stable combustor operation in ramjet mode. We simulate unsteady dynamics inside an experimental isolator, including the propagation of an unstart event that leads to loss of compression. Using a suite of simulations, the sensitivity of the results to LES models and numerical implementation is studied.
Large Eddy Simulation of Supersonic Combustion with Application to Scramjet Engines
Author: Peter CocksPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
This work evaluates the capabilities of the RANS and LES techniques for the simulation of high speed reacting flows. These methods are used to gain further insight into the physics encountered and regimes present in supersonic combustion. The target application of this research is the scramjet engine, a propulsion system of great promise for efficient hypersonic flight. In order to conduct this work a new highly parallelised code, PULSAR, is developed. PULSAR is capable of simulating complex chemistry combustion in highly compressible flows, based on a second order upwind method to provide a monotonic solution in the presence of high gradient physics. Through the simulation of a non-reacting supersonic coaxial helium jet the RANS method is shown to be sensitive to constants involved in the modelling process. The LES technique is more computationally demanding but is shown to be much less sensitive to these model parameters. Nevertheless, LES results are shown to be sensitive to the nature of turbulence at the inflow; however this information can be experimentally obtained. The SCHOLAR test case is used to validate the reacting aspects of PULSAR. Comparing RANS results from laminar chemistry and assumed PDF combustion model simulations, the influence of turbulence-chemistry interactions in supersonic combustion is shown to be small. In the presence of reactions, the RANS results are sensitive to inflow turbulence, due to its influence on mixing. From complex chemistry simulations the combustion behaviour is evaluated to sit between the flamelet and distributed reaction regimes. LES results allow an evaluation of the physics involved, with a pair of coherent vortices identified as the dominant influence on mixing for the oblique wall fuel injection method. It is shown that inflow turbulence has a significant impact on the behaviour of these vortices and hence it is vital for turbulence intensities and length scales to be measured by experimentalists, in order for accurate simulations to be possible.
Turbulent Combustion Modeling
Author: Tarek EchekkiPublisher: Springer Science & Business Media
ISBN: 9400704127
Category : Technology & Engineering
Languages : en
Pages : 496
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.
Unsteady Supersonic Combustion
Author: Mingbo SunPublisher: Springer Nature
ISBN: 9811535957
Category : Technology & Engineering
Languages : en
Pages : 380
Book Description
This book describes the unsteady phenomena needed to understand supersonic combustion. Following an initial chapter that introduces readers to the basic concepts in and classical studies on unsteady supersonic combustion, the book highlights recent studies on unsteady phenomena, which offer insights on e.g. interactions between acoustic waves and flames, flow dominating instability, ignition instability, flame flashback, and near-blowout-limit combustion. In turn, the book discusses in detail the fundamental mechanisms of these phenomena, and puts forward practical suggestions for future scramjet design.
Large Eddy Simulation of Turbulent Supersonic Combustion and Characteristics of Supersonic Flames
Author: Basic Research and Technologies for Two-Stage-to-Orbit Vehicles
Author: Dieter JacobPublisher: John Wiley & Sons
ISBN: 3527605509
Category : Technology & Engineering
Languages : en
Pages : 683
Book Description
Focusing on basic aspects of future reusable space transportation systems and covering overall design, aerodynamics, thermodynamics, flight dynamics, propulsion, materials, and structures, this report presents some of the most recent results obtained in these disciplines. The authors are members of three Collaborative Research Centers in Aachen, Munich and Stuttgart concerned with hypersonic vehicles. A major part of the research presented here deals with experimental and numerical aerodynamic topics ranging from low speed to hypersonic flow past the external configuration and through inlet and nozzle. Mathematicians and engineers jointly worked on aspects of flight mechanics like trajectory optimization, stability, control and flying qualities. Structural research and development was predominantly coupled to the needs for high temperature resistant structures for space vehicles.
Large-Eddy Simulation of Premixed Turbulent Combustion Using Flame Surface Density Approach
Author: Wen LinAdvanced Turbulent Combustion Physics and Applications
Author: N. SwaminathanPublisher: Cambridge University Press
ISBN: 1108497969
Category : Science
Languages : en
Pages : 485
Book Description
Explore a thorough overview of the current knowledge, developments and outstanding challenges in turbulent combustion and application.
Author: Donald P. Rizzetta