Download or read book Analysis of the Wave Scattering from Turbulent Premixed Flame written by Ju Hyeong Cho and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A theoretical investigation of acoustic wave interactions with turbulent premixed flames was performed. Such interactions affect the characteristic unsteadiness of combustion processes, e.g., combustion instabilities. The small perturbation method (SPM) was utilized to evaluate the scattered fields as a result of the flame-wave interaction at the instantaneous wrinkling surface of a randomly moving turbulent flame. Stochastic analysis of ensemble-averaged net acoustic energy was conducted to examine coherent and incoherent acoustic energy amplification /damping by the interaction. Net acoustic energy flux out of the flame is due to two factors: the acoustic velocity jump due to unsteady heat release from flame. The other is the flames unsteady motion. Five(5) dimensionless parameters that govern this net acoustic energy were determined: rms height and correlation length of flame front, incident wave frequency, the ratio of flames diffusion time to flame fronts correlation time, and incidence angle. The dependence of net acoustic energy upon these dimensionless parameters was illustrated and discussed by numerical simulations in case of Gaussian statistics of flame front. The laminar flame response to equivalence ratio perturbations was also examined, showing that the overall heat release response is controlled by the superposition of three disturbances: heat of reaction, flame speed, and flame area. Heat of reaction disturbances dominate the flame response at low Strouhal numbers, roughly defined as (frequency x flame length)/(axial flow velocity). All three disturbances play equal roles at Strouhal numbers of O(1). In addition, the mean equivalence ratio exerts little effect upon this transfer function at low Strouhal numbers. At O(1) Strouhal numbers, the flame response increases with decreasing values of the mean equivalence ratio.
Download or read book High Frequency Acoustic Wave Scattering from Turbulent Premixed Flames written by Venkateswarlu Narra and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes an experimental investigation of high frequency acoustic wave scattering from turbulent premixed flames. The objective of this work was to characterize the scattered incoherent acoustic field and determine its parametric dependence on frequency, flame brush thickness, incident and measurement angles, mean velocity and flame speed. The experimental facility consists of a slot burner with a flat flame sheet that is approximately 15 cm wide and 12 cm tall. The baseline cold flow characteristics and flame sheet statistics were extensively characterized. Studies were performed over a wide range of frequencies (1-24 kHz) in order to characterize the role of the incident acoustic wave length. The spectrum of the scattered acoustic field showed distinct incoherent spectral sidebands on either side of the driving frequency. The scattered incoherent field was characterized in terms of the incoherent field strength and spectral bandwidth and related to the theoretical predictions. The role of the flame front wrinkling scale, i.e., flame brush thickness, was also studied. Flame brush thickness was varied independent of the mean velocity and flame speed by using a variable turbulence generator. Results are reported for five flame brush thickness cases, ranging from 1.2 mm to 5.2 mm. Some dependence of scattered field characteristics on flame brush thickness was observed, but the magnitude of the effect was much smaller than expected from theoretical considerations. The spatial dependence of the scattered field was investigated by measuring the scattered field at four measurement angles and exciting the flame at four incident angles. Theory predicts that these variations influence the spatial scale of the acoustic wave normal to the flame, a result confirmed by the measurements. Measurements were performed for multiple combinations of mean velocities and flame speeds. The scattered field was observed to depend strongly on the flame speed. Further analysis suggested that the change in orientation angle distribution with flame speed had a large influence on the scattered field. The scattered field characteristics did not show any appreciable change with mean velocity. This result was expected since flame brush thickness characteristics themselves exhibit a weak velocity dependence.
Download or read book Experimental Study of Turbulent Premixed Combustion in V shaped Flames written by Sina Kheirkhah and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Characteristics of turbulent premixed flames were investigated experimentally. The investigations were performed using Mie scattering, Particle Image Velocimetry, Rayleigh scattering, and broad-band luminosity imaging techniques. Methane-air flames associated with a relatively wide range of turbulence intensities, fuel-air equivalence ratios, and mean bulk flow velocities were investigated. For a relatively moderate value of turbulence intensity, a new concept is introduced and utilized to provide a detailed description associated with interaction of turbulent flow and flame front. The concept pertains to reactants velocity estimated at the vicinity of the flame front and is referred to as the edge velocity. Specifically, it is shown that fluctuations of the flame front position are induced by fluctuations of the edge velocity. For a relatively wide range of turbulence intensity, several characteristics of turbulent premixed flames, namely, front topology, brush thickness, surface density, and consumption speeds are investigated. For the first time, several flame front structures are identified and studied. It is shown that, due to formation of these front structures, the regime of turbulent premixed combustion transitions from the regime of counter-gradient diffusion to that of the gradient diffusion. In addition to these, a comprehensive study is performed to investigate influence of flame configuration on several flame front characteristics. It is obtained that, although changing the flame configuration influences several flame characteristics, the trends associated with the effects of governing parameters on the characteristics are nearly independent of the flame configuration.
Download or read book Unsteady Combustor Physics written by Tim C. Lieuwen and published by Cambridge University Press. This book was released on 2021-10-21 with total page 533 pages. Available in PDF, EPUB and Kindle. Book excerpt: Explore a unified treatment of the dynamics of combustor systems, including acoustics, fluid mechanics, and combustion in a single rigorous text. This updated new edition features an expansion of data and experimental material, updates the coverage of flow stability, and enhanced treatment of flame dynamics. Addresses system dynamics of clean energy and propulsion systems used in low emissions systems. Synthesizing the fields of fluid mechanics and combustion into a coherent understanding of the intrinsically unsteady processes in combustors. This is a perfect reference for engineers and researchers in fluid mechanics, combustion, and clean energy.
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.
Download or read book Development and Application of a Light Scattering Technique for the Study of Premixed Turbulent Flames written by Robert M. Gurnitz and published by . This book was released on 1966 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Unsteady Combustion written by F. Culick and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains selected papers prepared for the NATO Advanced Study Institute on "Unsteady Combustion", which was held in Praia da Granja, Portugal, 6-17 September 1993. Approximately 100 delegates from 14 countries attended. The Institute was the most recent in a series beginning with "Instrumentation for Combustion and Flow in Engines", held in Vimeiro, Portugal 1987 and followed by "Combusting Flow Diagnostics" conducted in Montechoro, Portugal in 1990. Together, these three Institutes have covered a wide range of experimental and theoretical topics arising in the research and development of combustion systems with particular emphasis on gas-turbine combustors and internal combustion engines. The emphasis has evolved roughly from instrumentation and experimental techniques to the mixture of experiment, theory and computational work covered in the present volume. As the title of this book implies, the chief aim of this Institute was to provide a broad sampling of problems arising with time-dependent behaviour in combustors. In fact, of course, that intention encompasses practically all possibilities, for "steady" combustion hardly exists if one looks sufficiently closely at the processes in a combustion chamber. The point really is that, apart from the excellent paper by Bahr (Chapter 10) discussing the technology of combustors for aircraft gas turbines, little attention is directed to matters of steady performance. The volume is divided into three parts devoted to the subjects of combustion-induced oscillations; combustion in internal combustion engines; and experimental techniques and modelling.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied mechanics reviews written by and published by . This book was released on 1948 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book AIAA Aerospace Sciences Meeting and Exhibit 42nd written by and published by . This book was released on 2004 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1998 with total page 980 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2008 with total page 906 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA Thesaurus written by and published by . This book was released on 1994 with total page 916 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Study of the Characteristics of Turbulent Premixed Flames written by Mohamed Elshimy and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NBS Special Publication written by and published by . This book was released on 1968 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Publications of the National Bureau of Standards Catalog written by United States. National Bureau of Standards and published by . This book was released on 1983 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy Research Abstracts written by and published by . This book was released on 1990 with total page 840 pages. Available in PDF, EPUB and Kindle. Book excerpt:
