Author: J. C. HermansonPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
An Experimental Study of Isolated Turbulent Flame Puffs with a Co-flow
Author: J. C. HermansonExperimental Study of the Flowfield of a V-shaped Premixed Turbulent Flame
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
The flowfield of a V-shaped, premixed ethylene/air flame in grid induced turbulence has been studied using Laser Doubler Velocimetry. The experimental conditions covered free-stream velocities of 5 and 7 m/s and equivalence ratios ranging from 0.6 to 0.78. The two-dimensional velocity vectors obtained indicate that flow deflection in the free stream was significant and seemed to correlate with the flame angle. The influence of the flame holder wake on the flame was demonstrated. In the presence of the flame, an increase in the turbulence level in the free stream was found and was attributed to fluctuations in flow deflection induced by the fluctuating flame.
Experimental Study of Turbulent Flame Structure
Author: Matthew Robert HarkerA Gallery of Combustion and Fire
Author: Charles E. Baukal, Jr.Publisher: Cambridge University Press
ISBN: 1107154979
Category : Law
Languages : en
Pages : 193
Book Description
The first book to present a full-color visual panorama of combustion images along with explanatory and tutorial overviews.
Experimental Investigation of Flow Turbulence Effects on Premixed Methane-air Flames
Author: Kenneth Owen SmithPublisher:
ISBN:
Category : Flame
Languages : en
Pages : 488
Book Description
Flame Structure and Emissions of Strongly-pulsed Turbulent Diffusion Flames with Swirl
Author: Ying-Hao LiaoPublisher:
ISBN:
Category : Flame
Languages : en
Pages : 201
Book Description
This work studies the turbulent flame structure, the reaction-zone structure and the exhaust emissions of strongly-pulsed, non-premixed flames with co-flow swirl. The fuel injection is controlled by strongly-pulsing the fuel flow by a fast-response solenoid valve such that the fuel flow is completely shut off between pulses. This control strategy allows the fuel injection to be controlled over a wide range of operating conditions, allowing the flame structure to range from isolated fully-modulated puffs to interacting puffs to steady flames. The swirl level is controlled by varying the ratio of the volumetric flow rate of the tangential air to that of the axial air. For strongly-pulsed flames, both with and without swirl, the flame geometry is strongly impacted by the injection time. Flames appear to exhibit compact, puff-like structures for short injection times, while elongated flames, similar in behaviors to steady flames, occur for long injection times. The flames with swirl are found to be shorter for the same fuel injection conditions. The separation/interaction level between flame puffs in these flames is essentially governed by the jet-off time. The separation between flame puffs decreases as swirl is imposed, consistent with the decrease in flame puff celerity due to swirl. The decreased flame length and flame puff celerity are consistent with an increased rate of air entrainment due to swirl. The highest levels of CO emissions are generally found for compact, isolated flame puffs, consistent with the rapid quenching due to rapid dilution with excess air. The imposition of swirl generally results in a decrease in CO levels, suggesting more rapid and complete fuel/air mixing by imposing swirl in the co-flow stream. The levels of NO emissions for most cases are generally below the steady-flame value. The NO levels become comparable to the steady-flame value for sufficiently short jet-off time. The swirled co-flow air can, in some cases, increase the NO emissions. The elevated NO emissions are due to a longer combustion residence time due to the flow recirculation within the swirl-induced recirculation zone. The reaction zone structure, based on OH planar laser-induced fluorescence (PLIF) is broadly consistent with the observation of luminous flame structure for these types of flames. In many cases, the reaction zone exhibits discontinuities at the instantaneous flame tip in the early period of fuel injection. These discontinuities in the reaction zone likely result from the non-ignition of injected fuel, due to a relatively slower reaction rate in comparison with the mixing rate. The discontinuity in the OH zone is generally seen to diminish with increased swirl level. Statistics generated from the OH PLIF signals show that the reaction zone area generally increases with increased swirl level, consistent with a broader and more convoluted OH-zone structure for flames with swirl. The reaction zone area for swirled flames generally exhibits a higher degree of fluctuation, suggesting a relatively stronger impact of flow turbulence on the flame structure for flames with swirl.
Experimental Study of Turbulent Premixed Combustion in V-shaped Flames
Author: Sina KheirkhahPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
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.
An Experimental Study of the Characteristics of High-speed Turbulent Flames in Premixed Gases
Author: Sydney Howard ReiterAn Experimental Study of Burner Stabilized Turbulent Flames in Premixed Reactants
Author: M. D. FoxPublisher:
ISBN:
Category : Flame
Languages : en
Pages : 33
Book Description
Current concepts of flame propagation in premixed, turbulent gas streams are examined. This leads to the conclusion that the link between theory and experiment is entirely inadequate and incapable of improvement by existing methods. A series of new methods is implemented in an attempt to short-circuit the unprofitable chain of hypothesis and experiment which has hampered the identification of dubious steps. Methods of introducing uniform turbulence at relatively slow flows and improvements in light sources allow analysis of the approach flow by photographing particles illuminated by an interrupted Tyndall beam. Three new optical deflection methods are used to give a measure of the randomness of flame-front orientation, of the time-mean structure of the flame and of the instantaneous shape of the corrugated front. It is found that this corrugated surface propagates at a velocity considerably in excess of the normal laminar burning velocity. Quantitative analysis of the frequency of "peaks" and "valleys" on the surface, together with comparative data from the apex of laminar flames, suggests an explanation in terms of the effects of curvature and, secondarily, of the influence of small scale turbulence.
Author: Gary David Grayson