Download or read book Numerical Simulations of Stationary and Transient Spray Combustion for Aircraft Gas Turbine Applications written by Athanase Alain Fossi and published by . This book was released on 2017 with total page 293 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of current and future aero gas turbine engines is mainly focused on the safety, the performance, the energy consumption, and increasingly on the reduction of pollutants and noise level. To this end, the engine's design phases are subjected to improving processes continuously through experimental and numerical investigations. The present thesis is concerned with the simulation of transient and steady combustion regimes in an aircraft gas turbine operating under various combustion modes. Particular attention is paid to the accuracy of the results, the computational cost, and the ease of handling the numerical tool from an industrial standpoint. Thus, a commercial Computational Fluid Dynamics (CFD) code widely used in industry is selected as the numerical tool. A CFD methodology consisting of its advanced turbulence and combustion models, coupled with a subgrid spark-based ignition model, is formulated with the final goal of predicting the whole ignition sequence under cold start and altitude relight conditions, and the main flame trends in the steady combustion regime. At first, attention is focused on the steady combustion regime. Various CFD methodologies are formulated using three turbulence models, namely, the Unsteady Reynolds-Averaged Navier-Stokes (URANS), the Scale-Adaptive Simulation (SAS), and the Large Eddy Simulation (LES) models. To appraise the relevance of incorporating a realistic chemistry model and chemical non-equilibrium effects, two different assumptions are considered, namely, the infinitely-fast chemistry through the partial equilibrium model, and the finite-rate chemistry through the diffusion flamelet model. For each of the two assumptions, both one-component and two-component fuels are considered as surrogates for kerosene (Jet A-1). The resulting CFD models are applied to a swirl-stabilized combustion chamber to assess their ability to retrieve the spray flow and combustion properties in the steady combustion regime. Subsequently, the ratios between the accuracy of the results and the computational cost of the three CFD methodologies are explicitly compared. The second intermediate study is devoted to the ignition sequence preceding the steady combustion regime. A bluff-body stabilized burner based on gaseous fuel, and employing a spark-based igniter, is considered to calibrate the CFD model formulated. This burner of relatively simple geometry can provide greater understanding of complex reactive flow features, especially with regard to ignitability and stability. The most robust of the CFD methodologies formulated in the previous configuration is reconsidered. As this burner involves a partially-premixed combustion mode, a combustion model based on the mixture fraction-progress variable formulation is adopted with the assumptions of infinitely-fast chemistry and finite-rate chemistry through the Bray-Moss-Libby (BML) and Flamelet Generated Manifold (FGM) models, respectively. The ignition model is first customized by implementing the properties of the flame considered. Thereafter, the customized ignition model is coupled to the LES solver and combustion models based on the two above-listed assumptions. To assess the predictive capabilities of the resulting CFD methodologies, the latter are used to predict ignition events resulting from the spark deposition at various locations of the burner, and the results are quantitatively and qualitatively validated by comparing the latter to their experimental counterparts. Finally, the CFD methodology validated in the gaseous configuration is extended to spray combustion by first coupling the latter to the spray module, and by implementing the flame properties of kerosene in the ignition model. The resulting CFD model is first applied to the swirl-stabilized combustor investigated previously, with the aim of predicting the whole ignition sequence and improving the previous predictions of the combustion properties in the resulting steady regime. Subsequently, the CFD methodology is applied to a scaled can combustor with the aim of predicting ignition events under cold start and altitude relight operating conditions. The ability of the CFD methodology to predict ignition events under the two operating conditions is assessed by contrasting the numerical predictions to the corresponding experimental ignition envelopes. A qualitative validation of the ignition sequence is also done by comparing the numerical ignition sequence to the high-speed camera images of the corresponding ignition event.

Download or read book Experiments and Numerical Simulations of Diluted Spray Turbulent Combustion written by Bart Merci and published by Springer Science & Business Media. This book was released on 2011-06-20 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reflects the outcome of the 1st International Workshop on Turbulent Spray Combustion held in 2009 in Corsica (France). The focus is on reporting the progress of experimental and numerical techniques in two-phase flows, with emphasis on spray combustion. The motivation for studies in this area is that knowledge of the dominant phenomena and their interactions in such flow systems is essential for the development of predictive models and their use in combustor and gas turbine design. This necessitates the development of accurate experimental methods and numerical modelling techniques. The workshop aimed at providing an opportunity for experts and young researchers to present the state-of-the-art, discuss new developments or techniques and exchange ideas in the areas of experimentations, modelling and simulation of reactive multiphase flows. The first two papers reflect the contents of the invited lectures, given by experts in the field of turbulent spray combustion. The first concerns computational issues, while the second deals with experiments. These lectures initiated very interesting and interactive discussions among the researchers, further pursued in contributed poster presentations. Contributions 3 and 4 focus on some aspects of the impact of the interaction between fuel evaporation and combustion on spray combustion in the context of gas turbines, while the final article deals with the interaction between evaporation and turbulence.

Download or read book Experiments and Numerical Simulations of Turbulent Combustion of Diluted Sprays written by Bart Merci and published by Springer Science & Business Media. This book was released on 2014-03-27 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reflects the results of the 2nd and 3rd International Workshops on Turbulent Spray Combustion. The focus is on progress in experiments and numerical simulations for two-phase flows, with emphasis on spray combustion. Knowledge of the dominant phenomena and their interactions allows development of predictive models and their use in combustor and gas turbine design. Experts and young researchers present the state-of-the-art results, report on the latest developments and exchange ideas in the areas of experiments, modelling and simulation of reactive multiphase flows. The first chapter reflects on flame structure, auto-ignition and atomization with reference to well-characterized burners, to be implemented by modellers with relative ease. The second chapter presents an overview of first simulation results on target test cases, developed at the occasion of the 1st International Workshop on Turbulent Spray Combustion. In the third chapter, evaporation rate modelling aspects are covered, while the fourth chapter deals with evaporation effects in the context of flamelet models. In chapter five, LES simulation results are discussed for variable fuel and mass loading. The final chapter discusses PDF modelling of turbulent spray combustion. In short, the contributions in this book are highly valuable for the research community in this field, providing in-depth insight into some of the many aspects of dilute turbulent spray combustion.

Download or read book Advanced Turbulent Combustion Modeling for Gas Turbine Application written by Andrea Donini and published by Andrea Donini. This book was released on with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Numerical Simulation of Hot Surface Ignition and Combustion of Fuel Sprays written by Danyal Mohaddes Khorassani and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to their high energy density and ease of transportation, liquid fuels continue to be used in a variety of combustion systems, including in aerospace, automotive and industrial applications. Analysis of the underlying physics of multiphase combustion phenomena, particularly as it pertains to ignition, contributes to improved physical understanding and supports greater system reliability and safety. High-fidelity numerical simulations are particularly effective in supporting improved fundamental understanding, but detailed simulations of practical multiphase combustion configurations are highly computationally costly. The study of accidental ignition of liquid fuels and the development of computationally efficient means of performing physically accurate multiphase combustion simulations are therefore important avenues of scientific inquiry. This dissertation considers the problem of the ignition and combustion of a wall-impinging fuel spray using four complementary approaches. First, to analyze the long-term wall heat flux caused by a wall-stagnating spray flame, a steady, one-dimensional, multi-continuum formulation is developed with consideration given to conjugate heat transfer effects. Second, an unsteady, one-dimensional, multi-continuum formulation is developed and a broad parametric study of the hot surface ignition of wall-stagnating fuel sprays is conducted. Third, high-fidelity three-dimensional large-eddy simulations are performed in an Eulerian-Lagrangian formulation using a finite-rate chemistry model. Fourth, the substantial computational cost of the high-fidelity simulations performed motivates the development of a computationally efficient spray combustion modeling framework. This dissertation extends the Pareto-efficient combustion (PEC) modeling framework to spray combustion through a rigorous analysis of the governing equations. The spray-augmented PEC formulation is applied to the high-fidelity simulation of a wall-stagnating spray flame and to the simulation of a realistic gas turbine combustor to demonstrate improved physical fidelity compared to tabulated chemistry, while reducing computational cost compared to monolithic finite-rate chemistry.

Download or read book Numerical Simulations of Turbulent Combustion written by Andrei Lipatnikov and published by Mdpi AG. This book was released on 2020-07 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent burning of gaseous fuels is widely used for energy conversion in stationary power generation, e.g., gas turbines, land transportation, piston engines, and aviation, and aero-engine afterburners. Nevertheless, our fundamental understanding of turbulent combustion is still limited, because it is a highly non-linear and multiscale process that involves various local phenomena and thousands (e.g., for gasoline-air mixtures) of chemical reactions between hundreds of species, including several reactions that control emissions from flames. Therefore, there is a strong need for elaborating high fidelity, advanced numerical models, and methods that will catch the governing physical mechanisms of flame-turbulence interaction and, consequently, will make turbulent combustion computations an efficient predictive tool for applied research and, in particular, for development of a new generation of ultra-clean and highly efficient internal combustion engines that will allow society to properly respond to current environmental and efficiency challenges. Accordingly, papers published in this Special Issue (i) contribute to our fundamental understanding of flame-turbulence interaction by analyzing results of unsteady multi-dimensional numerical simulations and (ii) develop and validate high-fidelity models and efficient numerical methods for computational fluid Dynamics research into turbulent combustion in laboratory burners and engines.

Download or read book Reduced Order Models and Large Eddy Simulation for Combustion Instabilities in Aeronautical Gas Turbines written by Fabien Dupuy (docteur en physique).) and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Increasingly stringent regulations as well as environmental concerns have lead gas turbine powered engine manufacturers to develop the current generation of combustors, which feature lower than ever fuel consumption and pollutant emissions. However, modern combustor designs have been shown to be prone to combustion instabilities, where the coupling between acoustics of the combustor and the flame results in large pressure oscillations and vibrations within the combustion chamber. These instabilities can cause structural damages to the engine or even lead to its destruction. At the same time, considerable developments have been achieved in the numerical simulation domain, and Computational Fluid Dynamics (CFD) has proven capable of capturing unsteady flame dynamics and combustion instabilities for aforementioned engines. Still, even with the current large and fast increasing computing capabilities, time remains the key constraint for these high fidelity yet computationally intensive calculations. Typically, covering the entire range of operating conditions for an industrial engine is still out of reach. In that respect, low order models exist and can be efficient at predicting the occurrence of combustion instabilities, provided an adequate modeling of the flame/acoustics interaction as appearing in the system is available. This essential piece of information is usually recast as the so called Flame Transfer Function (FTF) relating heat release rate fluctuations to velocity fluctuations at a given point. One way to obtain this transfer function is to rely on analytical models, but few exist for turbulent swirling flames. Another way consists in performing costly experiments or numerical simulations, negating the requested fast prediction capabilities. This thesis therefore aims at providing fast, yet reliable methods to allow for low order combustion instabilities modeling. In that context, understanding the underlying mechanisms of swirling flame acoustic response is also targeted. To address this issue, a novel hybrid approach is first proposed based on a reduced set of high fidelity simulations that can be used to determine input parameters of an analytical model used to express the FTF of premixed swirling flames. The analytical model builds on previous works starting with a level-set description of the flame front dynamics while also accounting for the acoustic-vorticity conversion through a swirler. For such a model, validation is obtained using reacting stationary and pulsed numerical simulations of a laboratory scale premixed swirl stabilized flame. The model is also shown to be able to handle various perturbation amplitudes. At last, 3D high fidelity simulations of an industrial gas turbine powered by a swirled spray flame are performed to determine whether a combustion instability observed in experiments can be predicted using numerical analysis. To do so, a series of forced simulations is carried out in en effort to highlight the importance of the two-phase flow flame response evaluation. In that case, sensitivity to reference velocity perturbation probing positions as well as the amplitude and location of the acoustic perturbation source are investigated. The analytical FTF model derived in the context of a laboratory premixed swirled burner is furthermore gauged in this complex case. Results show that the unstable mode is predicted by the acoustic analysis, but that the flame model proposed needs further improvements to extend its applicability range and thus provide data relevant to actual aero-engines.

Download or read book Numerical Simulations of Combustion Instabilities in Gas Turbine Combustors with Applications written by Grant Douglas Swenson and published by . This book was released on 2000 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Combustion in Advanced Gas Turbine Systems written by I. E. Smith and published by Elsevier. This book was released on 2014-05-17 with total page 415 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cranfield International Symposium Series, Volume 10: Combustion in Advanced Gas Turbine Systems covers the proceedings of an International Propulsion Symposium, held at the College of Aeronautics in Cranfield in April 1967. The book focuses on the processes, methodologies, reactions, and transformations involved in chemical combustion. The selection first takes a look at the design considerations in advanced gas turbine combustion chambers, combustion in industrial gas turbines, and combustion development on the Rolls-Royce Spey engine. Discussions focus on mechanical condition, carbon-formation and exhaust smoke, system requirements, fuel oil ash deposition and corrosion, combustion-system design, performance requirements, types of primary zone, fuel injection, and combustion chamber types. The text then examines subsonic flow flameholder studies using a low pressure simulation technique; stabilization of hydrogen diffusion flames by flame-holders in supersonic flow at low stagnation temperatures; and augmentation systems for turbofan engines. The book takes a look at a consideration of the possible use of refractory ceramic materials for advanced combustion chamber design; cooling of flame tubes by steam injection; and combustion problems in the massive steam injection gas turbine. The selection is a valuable source of information for researchers interested in the process of combustion in advanced gas turbine systems.

Download or read book Simulation and Control of Instationary Reactive Flows in Matrix Burner for Small Power Gas Turbine Applications written by James Fayiah Willie and published by Cuvillier Verlag. This book was released on 2012-02-02 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main objective of this thesis is to analyze combustion instabilities in a matrix burner. The various tools that exist for analyzing thermoacoustic instabilities are applied to the matrix burner with multiple flames. The principal goals are to determine the primary causes of combustion instabilities in the burner and to explore ways of controlling such instabilities in order to prevent damage to the burner. To achieve these goals, the stability map of the burner obtained from measurements is analyzed. This is followed by the analysis of the aerodynamics of the cold flow using CFD. Results obtained from CFD are validated with PIV and LDA results from measurements. Critical are the centerline axial velocity inside the combustion chamber and the recirculation zones on the walls of the combustion chamber and those between the various slots of the matrix burner. Cold flow simulations are followed by reactive flow simulations for both gaseous and liquid fuels. A detailed atomization model is developed for the liquid fuel case from experimental data. Two combustion models, namely, the combined finite rate/eddy dissipation model and the finite rate chemistry model are compared in the CFD simulations of combustion instabilities and validation with measurements are done. The latter is chosen over the former because it accounts for chemistry and it is not numerically dissipative. Two CFD softwares, Fluent and CFX are also compared to determine which is better at capturing acoustics. System identification using CFD is used to determine the flame transfer function and the acoustic transfer matrix. This is followed by the use of acoustic forcing and fuel modulation on the primary and pilot in order to limit the amplitude of the instabilities inside the matrix burner combustor. The 1D acoustic network is used to determine the longitudinal eigenmodes of the matrix burner. This is followed by the use of 3D finite element method (FEM) and fluid-structure interaction (FSI) to determine whether a coupling exist between the fluid and structure of the matrix burner combustor and vice versa. Finally, Full harmonic analysis is performed for the rectangular combustor and the results obtained are validated with analytical results. This is followed by the 3D structure modal analysis of the full matrix burner test rig.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Combustion and Heat Transfer in Gas Turbine Systems written by E. R. Norster and published by Elsevier. This book was released on 2013-10-22 with total page 417 pages. Available in PDF, EPUB and Kindle. Book excerpt: Combustion and Heat Transfer in Gas Turbine Systems is a compilation of papers from the Proceedings of an International Propulsion Symposium held at the College of Aeronautics, Cranfield in April 1969. This compilation deals with research done by academic and scientific institutions and of industrial organizations, with some research papers covering atomization, fuels, and high-temperature materials. One paper describes the combustion system of the Concorde engine used in commercial flights, temperature of metal parts, and some design modifications to increase the mechanical life of the combustion system. Another paper discusses the evolution of the RB 162 combustion system that is used in the vertical takeoff and landing aircrafts. The RB 162 has many design features of the earlier single reversal chamber and differs in only one or two points. The book then notes the necessity of a plenum chamber burning to further development of supersonic engines and flight. One paper also proposes an alternative theory to the traditional ignition theory of altitude relighting such as those developed by Lewis and von Elbe. Another paper reposts on some observations made of the atomizing characteristics of air-blast atomizers and proposes simple changes to improve the performance of the atomizer by prefilming and allowing air to both sides of the fuel. This compilation will prove very helpful for aeronautical engineers, aviation designers, physicists, students of engineering, and readers who are interested in the design and development of jet engines and supersonic aircrafts.

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.

Download or read book Numerical Simulation of Spray Combustion Using Bio mass Derived Liquid Fuels written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The main objective of this work is to create a robust model for two-phase liquid spray combustion flow using vegetable oils, to investigate the flow structure generated by a swirler array with different fuels, and secondly to assess and optimise the capability of the CFD to predict accurately the results obtained experimentally and eventually enhance CFD model development and simulation. Validation is achieved by comparing the numerical results obtained with CFD with the experimental measurements. The purpose of this research is to increase the scientific understanding of the fundamental mechanisms of the spray combustion process using a carbon neutral fuel such as ethanol and biodiesel. In fact, very few numerical simulations of liquid biomass fuels in gas turbine systems are available in the literature. The flames are simulated using the commercial code FLUENT. The combustion/turbulence interaction is modelled using the laminar flamelet approach with detailed chemistry modelled using the OPPDIFF model from CHEMKIN. While the experiments could be carried out only up to 3 atm, the simulations were further extended to a maximum pressure of 10 atm. The FLUENT results were assessed qualitatively and quantitatively between the experimental measurements and the simulation. The cold flow features have been captured by the present simulations with a good degree of accuracy. Effect of air preheating was investigated for the biodiesel, and sensitivity to droplet size and spray angles variation were analysed. Good agreement was obtained for ethanol except in the fuel lean region due to failure of the FLUENT laminar flamelet model to capture local flame extinction while biodiesel simulation resulted in a significant overprediction of the flame temperature especially in the downstream region and satisfactory results further upstream. The results show the importance of setting proper droplet initial conditions, since it will significantly affect the structure of the flame.

Download or read book Direct Numerical Simulations of Turbulent Flow and Spray Combustion written by Abouelmagd Abdelsamie and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Transient Spray Combustion Computations written by William A. Sirignano and published by . This book was released on 1986 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many practical combustion devices involves direct injection of liquid fuel into the combustion chamber, e.g., gas turbine engines, diesel engines, rockets and ramjet engines, and furnaces. Typically, the fuel is of sufficiently low volatility that vaporization is an important or controlling factor in the rate of combustion. It is desirable, therefore, to analyze the trajectories, heating, and vaporization of the large number of droplets in a fuel spray and to account for the exchange of mass, momentum, and energy between the liquid and gas phases in order to predict combustor performance, stability, and pollutant emission. A review is made of one-dimensional, unsteady and axisymmetric, unsteady spray combustion calculations. Proper formulation of the governing two-phase equations are discussed. Problems of ignition and flame propagation are examined. Since droplet lifetime is of the same order to magnitude as time for heat transport through the droplet, transient heating of the droplets is considered together with effects of internal droplet circulation due to shear forces on the droplet surface. Keywords: Sprays, Combustion, Ignition, Fuels, Droplets, Vaporization, Drag.

Download or read book Catalogus bibliotheek School voor de Grafische Vakken te Utrecht written by and published by . This book was released on 1930 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: