High-Speed Reacting Flows: Research to Understand Processes in Supersonic Combustors PDF Download
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Author: H. Krier
Publisher:
ISBN:
Category :
Languages : en
Pages : 4
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Book Description
The objective of this program is to determine the fundamental fluid dynamic mechanisms occurring in the mixing and entrainment processes in the free shear layer formed between two high-speed (supersonic/sonic) streams. How the fluid mixing and subsequent combustion depends upon compressibility, as well as other parameters of the free shear layer process, is currently being investigated in an experimental study of the two-dimensional, compressible, turbulent reactive free shear layer. Use of non-intrusive, laser-based diagnostics including laser Schlieren for flow visualization, Laser Doppler Velocimetry (LDV) for velocity and turbulence measurement, and Planar Laser-Induced Fluorescence (PLIF) for temperature and concentration measurements are being employed.
Author: H. Krier
Publisher:
ISBN:
Category :
Languages : en
Pages : 4
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Book Description
The objective of this program is to determine the fundamental fluid dynamic mechanisms occurring in the mixing and entrainment processes in the free shear layer formed between two high-speed (supersonic/sonic) streams. How the fluid mixing and subsequent combustion depends upon compressibility, as well as other parameters of the free shear layer process, is currently being investigated in an experimental study of the two-dimensional, compressible, turbulent reactive free shear layer. Use of non-intrusive, laser-based diagnostics including laser Schlieren for flow visualization, Laser Doppler Velocimetry (LDV) for velocity and turbulence measurement, and Planar Laser-Induced Fluorescence (PLIF) for temperature and concentration measurements are being employed.
Author: C. T. Bowman
Publisher:
ISBN:
Category :
Languages : en
Pages : 28
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Book Description
An experimental and computational investigation of supersonic combustion flows is in progress. The principal objective of the research is to gain a more fundamental understanding of mixing and chemical reaction in supersonic flows. The research effort comprises three inter-related elements: 1) an experimental study of mixing and combustion in a supersonic plane mixing layer; 2) development of laser-induced fluorescence techniques for time-resolved two-dimensional imaging of species concentration, temperature, velocity and pressure; and, 3) numerical simulations of compressible reacting flows. The design of the supersonic plane mixing layer was completed and the high-pressure gas storage system was installed. The pulsed lasers and camera systems, to be used for two-dimension flow field imaging, were installed and initial performance evaluations are in progress. This work has focussed on development of appropriate numerical methods for performing full-turbulence simulations of high-speed compressible flows and on the application of these methods to temporally and spatially developing compressible mixing layers. The effort to date has identified several promising numerical methods for compressible flow problems. In addition, a code was developed for compressible mixing layers, and initial simulation using this code shows interesting features, such as imbedded shock waves, in high-speed mixing layers. Keywords: Turbulent reacting flow, Laser diagnostics, Computational fluid dynamics.
Author: John Buckmaster
Publisher: Springer Science & Business Media
ISBN: 9401110506
Category : Technology & Engineering
Languages : en
Pages : 639
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Book Description
This volume contains the proceedings of the Workshop on Com bustion, sponsored by the Institute for Computer Applications in Science and Engineering (ICASE) and the NASA Langley Research Center (LaRC). It was held on October 12-14, 1992, and was the sec ond workshop in the series on the subject. The first was held in 1989, and its proceedings were published by Springer-Verlag under the title "Major Research Topics in Combustion," edited by M. Y. Hussaini, A. Kumar, and R. G. Voigt. The focus of the second workshop was directed towards the development, analysis, and application of basic models in high speed propulsion of particular interest to NASA. The exploration of a dual approach combining asymptotic and numerical methods for the analysis of the models was particularly encouraged. The objectives of this workshop were i) the genesis of models that would capture or reflect the basic pllysical phenomena in SCRAMJETs and/or oblique detonation-wave engines (ODWE), and ii) the stimulation of a greater interaction between NASA exper imental research community and the academic community. The lead paper by D. Bushnell on the status and issues of high speed propulsion relevant to both the SCRAMJET and the ODWE parallels his keynote address which set the stage of the workshop. Following the lead paper were five technical sessions with titles and chairs: Experiments (C. Rogers), Reacting Free Shear Layers (C. E. Grosch), Detonations (A. K. Kapila), Ignition and Struc ture (J. Buckmaster), and Unsteady Behaviour ('1'. L. Jackson).
Author: Paul A. Libby
Publisher:
ISBN:
Category : Combustion
Languages : en
Pages : 12
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Research conducted under the sponsorship of this grant focused on fundamental investigations of mixing, chemical-reaction and combustion processes; in turbulent, subsonic, and supersonic flows. Research on hydrocarbon-combustion was on methane and ethane flames. Flame extinction strain-rate measurements, flame speed, and detailed experiment-simulation comparisons indicate difficulties in modeling of fuel-rich flames. Direct Numerical Simulations (DNS) of axisymmetric unsteady flows in both cold and hot impinging jets were also performed. The research included work on high-speed internal flows of interest to scramjet mixing and combustion, aimed at flow-control and flameholding issues. DNS and Large Eddy Simulations (LES) of Rayleigh-Taylor instability flows studied Reynolds number effects on mixing in this important flow. Advances in high-performance digital-imaging systems were transferred to the laboratory environment enabling measurements unachievable by other means.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 500
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Author: J. Tamagno
Publisher:
ISBN:
Category :
Languages : en
Pages : 117
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Book Description
This report summarizes studies conducted in the area of high speed combustion processes. Although the work is basic in nature, the choice of particular aspects for investigation was oriented toward fuels and conditions pertaining to supersonic combustion in ramjet engines. The specific tasks which have been considered include: high altitude combustion studies, combustion of hydrocarbon fuels, effects of adverse pressure gradients in combustion fields and transition from supersonic to subsonic speeds by means of energy release. Analytical techniques developed for studying hydrogen-air combustion processes were extended to include hydrocarbon fuels. It was found that some modification of the turbulent transports from non-burning configurations is required in order to obtain agreement between the analytical results and the combustion experiments. Furthermore, transport models which gave satisfactory results for hydrogen-air reacting systems need modification for slower reacting fuels, e.g. methane and propane. Studies of the interaction of adverse pressure gradients with the mixing and combustion region show that the structure of the combustion field can be radically altered by pressure effects. Finally, the conditions of heat release which may produce a smooth transition from supersonic to subsonic flow were examined analytically. (Author).
Author: T. Takeno
Publisher: Elsevier
ISBN: 0444598898
Category : Science
Languages : en
Pages : 462
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Book Description
An understanding of the intricacies in the turbulent combustion process may be a key to solving many of the current energy and environmental problems. The essential nature of turbulent combustion can be derived from the interaction between stochastic flow fluctuations and deterministic molecular processes, such as chemical reaction and transport processes. Undoubtedly, this is one of the most challenging fields of engineering science today, requiring as it does the interaction of scientists and engineers in the respective fields of chemical kinetics and fluid mechanics. The 28 papers in this volume review recent advances in these two disciplines providing new insights into the fundamental processes, addressing a great deal of recent progress. This progress ranges from descriptions of elementary chemical kinetics, to working those descriptions into combustion calculations with large numbers of elementary steps, to improved understanding of turbulent reacting flows and advances in simulations of turbulent combustion. The contributions will inspire further research on many fronts, advancing the understanding of combustion processes, as well as fostering a growing interdisciplinary cooperation.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 7
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Book Description
This research involves theoretical studies of the chemical and fluid mechanical phenomena which make turbulent combustion in high-speed flows different from such combustion in low-speed flows. Finite-rate chemistry plays a significant role in high-speed flows because of the small ratios of flow times to chemical times. The studies address ignition and extinction phenomena in nonpremixed turbulent combustion of hydrogen-air systems by both numerical and asymptotic methods. Attention also is paid to effects of compressibility in high-speed turbulent combustion, with consideration given to interdispersal configurations of shocklets and flamelets. Efforts are made to provide a firmer foundation for the modeling of high-speed turbulent reacting flows, to aid in the development of a formulation which gives results that can be compared with experiments, on turbulent combustion ... Turbulent flames, Diffusion flames, Supersonic combustion.
Author: Peter Cocks
Publisher:
ISBN:
Category :
Languages : en
Pages :
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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.
