Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 20 for “"Blow-off"”.
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The blow-off of burner flames
The mechanism of blow-off has been investigated because of the increased importance of this phenomenon consequent upon the conversion of the Gas Industry from high burning velocity manufactured gas to relatively low burning velocity natural gas.Burning velocity is regarded as the primary variable …
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Blow-off in gas turbine combustors
… flame structure close to the extinction and the blow-off events of non-premixed and spray flames stabilized on an axisymmetric bluff body in a confined swirl configuration. The comparison of flames of different canonical types in the same basic aerodynamic field allows insights on the relative …
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Simulating Extinction and Blow-off in Kerosene Swirl Spray Flames
… phenomena like flame extinction and lean blow-off (LBO) are still not well-understood for conventional spray flames, but alternative fuels provide additional challenges as they have been observed to have increased variability from expected behaviour at conditions close to LBO. Evaporation …
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The Influence of Preferential Diffusion On the Blow-Off of Laminar Aerated Burner Flames
The blow-off of a laminar aerated burner flame in which Hydrogen is present cannot be characterised by the flame stretch correlation proposed by Reed. A literature review has indicated that the preferential diffusion of Hydrogen towards the point of stability in the region of maximum primary flame …
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Development of a multi-scale projection method with immersed boundaries for chemically reactive flows and its application to examine flame stabilization and blow-off mechanisms
… underlying mechanisms of flame stabilization and blow-off in canonical configurations. A second-order immersed boundary method for reacting flow simulations near heat conducting, grid conforming, solid object has been developed. The method is coupled with a block-structured adaptive mesh …
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Experimental investigation of unconfined bluff body stabilised flames with vapourised kerosene fuels
… devices is difficult because they are prone to blow-off, resulting in reduced efficiency or worse, engine failure. Thus, there is a need to understand the underlying physics of lean blow-off (LBO) so that accurate, yet computationally tractable models can be developed to predict its onset. In …
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Extinction in turbulent swirling non-premixed flames
… is reasonably predicted. At the experimental blow-off point, the LES/3D-CMC modelling does not obtain the occurrence of complete extinction, but severe extinction occurs at the flame base, qualitatively in line with experimental observations. Localized extinction features of a non-premixed …
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Transient Phenomena in Annular Combustors
… gas turbine combustors, namely ignition and blow-off. The experiments were conducted on complex multi-burner geometries, close to realistic combustors, to provide a wide data set including stability limits, flame regimes and physical mechanisms of ignition and extinction. The first part of …
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Oxy-combustion of High Water Content Fuels
… Flame stability, as characterized by the blow-off limit -- the lowest O2 concentration when a flame could exist under a given oxidizer flow rate, was determined as a function of total oxidizer flow rate, fuel concentration and nozzle type. Furthermore, both the gas temperature contour and …
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EXPERIMENTAL INVESTIGATION OF THE RESPONSE OF FLAMES WITH DIFFERENT DEGREES OF PREMIXEDNESS TO ACOUSTIC OSCILLATIONS
… flame. The proximity of forced flames to blow-off was found to be critical in their heat release response, as close to blow-off the flame response was significantly lower than that farther from blow-off. In the NPR and NPA systems, it was shown that the acoustic forcing reduced the …
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Experimental and gyrokinetic studies of impurity transport in the core of Alcator C-Mod Plasmas
… L-mode discharges. A new, multi-pulse laser blow-off system was designed and constructed to introduce trace amounts of non-recycling, non-intrinsic, impurities in the plasma edge. This system was coupled with an x-ray crystal spectrometer, a single chord x-ray/ultraviolet spectrometer, and …
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Experimental Inference of Particle Transport in Tokamak Plasmas
… coefficients have been inferred following laser blow-off (LBO) impurity injections into both Alcator C-Mod and DIII-D plasmas. Development of the Aurora modeling package has supported the creation of Bayesian frameworks that leverage a wide range of spectroscopic diagnostics. This investigation …
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Development of mesoscale burner arrays for next generation compact gas turbines
… optical diagnostic and analysis techniques. Lean blow off limit, flame temperature, and NO emission measurements were performed on the mesoscale burner array; the obtained measurements were compared with those of a baseline single-swirl burner. Furthermore, various flame structures from the …
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Dynamic stability, blowoff, and flame characteristics of oxy-fuel combustion
… and similar for air and oxy-combustion. Blowoff trends are also analyzed. While oxy-combustion flames blow off at a higher temperature for a given Reynolds number due to weaker flames, there is an unexpected negative slope in blowoff velocity vs temperature for both air and …
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Towards predicting dynamics in turbulent premixed combustion using PIV-PLIF measurements of flow-flame microstructure
… with the stability characteristics, i.e., blow-off and flashback limits as well as the onset of the thermoacoustic instabilities, highlighting a critical role of the recirculation zone in flame stabilization. An expression for the critical phase at which dynamic mode transition occurs is …
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Development of Multi-perspective Diagnostics and Analysis Algorithms with Applications to Subsonic and Supersonic Combustors
… during transient processes such as lean blow off and ignition. After these relatively simple tests and demonstrations, these algorithms were applied to process the measurements obtained from multi-perspective in the supersonic combustor. compared to past analyses (which have been limited …
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The Role of Swirl in the Flow Structure and Response of Premixed Flames
… unstable as they may operate close to the flame blow off limit. Therefore, a suitable method of stabilisation is required. Swirlers or bluff bodies help in stabilising the flames, by creating recirculation zones of hot combustion products, and are common in practical applications. Another issue …
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Analyses of Bluff Body and Swirl-Stabilised Flames Using Large Eddy Simulation
… flame temperatures can be achieved, thereby offering reductions in pollutant emissions. The stability of these flames in practical combustion systems, where ubiquitous turbulence is present, is enhanced through the use of bluff body flame holders and swirling flow. However, these flames are …
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Lean Premixed Prevaporised Combustion for Microturbines
… to 343 and 393 K has little effect on the lean blow-off (LBO) velocity, but recessing the fuel injection significantly decreases the lean stability limit. To correlate these limits, various attempts to define a Damköhler number were made, but unlike previous studies with no prevaporisation, the …
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Increased Proton Energies - Above the ~ 60 MeV Empirical Barrier, from High-Contrast High-Intensity Short-Pulse Laser-Interactions with Micro-Cone Targets
… the cone neck [3]; preplasma is plasma from wall blow-off due to the low level of laser light entering the cone before the main high-intensity pulse, called laser "prepulse". Combining and correlating Cu Ka 2-D imaging with proton acceleration was one of my main goals for this dissertation. At an …