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.
Results
Showing 1 to 20 of 41 for “"Recirculation zone"”.
-
Primary zone modeling for gas turbine combustors
Gas turbine combustor primary zone flows are typified by swirling flow with heat release in a variable area duct, where a central toroidal recirculation zone is formed. The goal of the research was to develop reduced-order models for these flows in an attempt to gain insight into, and understanding …
-
Suppression of thermoacoustic instabilities in a swirl combustor through microjet air injection
… the combustion chamber in the flame anchoring zone. These microjet injectors attempt to modify the flow field so as to break the feedback mechanism between the chamber acoustics and the heat release rate. Eight microjet injector configurations are studied. Flow is injected axially into the …
-
Effect of inlet configurations on the aerodynamics of swirl combustors
… with non-swirling flow produced a uniform corner recirculation near the wall of the combustion chamber. The S-inlet made the corner recirculation zones unequal. The introduction of swirling in the flow created a central recirculation zone in addition to the corner recirculation zone. It was found …
-
An Experimental Study of Flame Holding
… flames is examined under conditions where the recirculation zone is absent.
-
The Role of Swirl in the Flow Structure and Response of Premixed Flames
… help in stabilising the flames, by creating recirculation zones of hot combustion products, and are common in practical applications. Another issue is the coupling of acoustic waves and heat release rate oscillations which create combustion instabilities. These instabilities can results is …
-
Large Eddy Simulations of Flow and Heat Transfer in the Developing and 180° Bend Regions of Ribbed Gas Turbine Blade Internal Cooling Ducts with Rotation - Effect of Coriolis and Centrifugal Buoyancy Forces
… 180° bend by shifting the shape of the separated recirculation zone at the tip of the dividing wall and increasing the mainstream flow area. In addition, turbulence is attenuated near the leading wall throughout the bend, while Coriolis forces have little effect on trailing wall turbulence in the …
-
Physics-based flame dynamics modeling and thermoacoustic instability mitigation
… by modifying the dynamics of the flame anchoring zone. The two different anchoring configurations investigated were the wake-stabilized flames and the perforated-plate stabilized flames. In order to investigate the wake-stabilized flames, experiments were performed in an atmospheric pressure, …
-
Aerodynamic Interactions in Vortex Tube Separator Arrays
… the VTS array rapidly generates a strong central recirculation zone while a single VTS does not, implying the existence of axial flow gradients within associated separators that could affect filtration efficiency. The key factor here is the global swirl intensity, which is increased in array flows …
-
Environmental Chamber to Regulate Film Morphology for Solar Energy Materials Printing Using Additive Manufacturing and Investigating the Role of Additives in Perovskites
… in the deposition process that makes use of a recirculation zone created by constrained nitrogen to control and improve printed films. A contour of the airflow pattern was simulated on ANSYS 18.1, giving us a visual representation and quantitative estimations of the air flow over the printed …
-
Simulation of Isothermal Combustion in Gas Turbines
… layers (including the rotor pressure side recirculation zone (a natural flame holder). Computational methods utilized both steady and time accurate calculations with transitional flow as well as laminar and turbulent combustion and species transport. It has been determined that burning …
-
Experimental investigation of unconfined bluff body stabilised flames with vapourised kerosene fuels
… axis, pockets of OH and CH2O were found in the recirculation zone (RZ), and eventually, the individual fragments were extinguished. The CH2O seemed to enter the RZ from downstream early in the LBO process, with reactants following suit at times closer to LBO. During LBO, the integrated OH* …
-
Experimental Investigation of a Lean, Premixed Gas Turbine Combustor Using Advanced Laser Diagnostics
… of the flame occurred primarily in the side recirculation zone at the edge of the premixer exit. Single-shot temperature measurements were made using coherent anti-Stokes Raman scattering at the two pressure drop conditions with an equivalence ratio of 0.7. Time-resolved measurements were …
-
Computations of nonreacting flameholder flows with a zonal grid method
… direction does not change the strength of the recirculation zone, but alters the flow pattern. The predicted streamlines, the turbulence kinetic energy K, and the reverse mass flow rate are presented.
-
Towards predicting dynamics in turbulent premixed combustion using PIV-PLIF measurements of flow-flame microstructure
… PIV data reveal significant changes in the recirculation zone structure depending on the equivalence ratio and the fuel composition, demonstrating the impact of chemical kinetics on the flow. These changes are shown to correlate strongly with the stability characteristics, i.e., blow-off and …
-
Application of a modified k-[epsilon] turbulence model to gas turbine combustor geometries
… shape and size of the primary centerline recirculation zone for both cases. The large swirl and axial velocity gradients, which are diffused by the standard k-epsilon model, are preserved by the Chen model. The overprediction of turbulent eddy viscosity in regions of high shear, which is …
-
Computational fluid dynamics simulations of oxy-coal combustion for carbon capture at atmospheric and elevated pressures
… used in this study underestimate the internal recirculation zone size and the turbulence mixing intensity in the char combustion zone, while LES improves the predictions of internal recirculation zone size, the entrainment of oxygen from the staging stream, and the overall flame length than the …
-
Experimental investigations into high-altitude relight of a gas turbine
… that fuel becomes trapped inside the central recirculation zone in high concentrations. High-speed flame imaging performed simultaneously with the PLIF measurements provides important insights into the motion and breakup of flame during relight. An algorithm developed to track the flame …
-
Transient Phenomena in Annular Combustors
… with the build up of formaldehyde in the side recirculation zone. The pattern of blow-off and detachment close to LBO could be explained with CH2O accumulating in the inner recirculation zone of a single burner causing the flame to lift, while restabilisation was triggered by flame pockets …
-
Analyses of Bluff Body and Swirl-Stabilised Flames Using Large Eddy Simulation
… gas mixture. Accurately capturing the near-field recirculation zone behind the bluff body is essential for predicting the stabilisation of the flame and experimental measurements are used to validate this. The lengths of the recirculation zones are well captured by the simulations for isothermal …
-
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
… of length and time efficiently. A novel "buffer zone" methodology is introduced to impose the solid-fluid boundary conditions such that symmetric derivatives and interpolation stencils can be used throughout the interior of the domain, thereby maintaining the order of accuracy of the method. Near …
Page 1 of 3