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Stabilization And Dynamic Of Premixed Swirling Flames

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Stabilization and Dynamic of Premixed Swirling Flames

Stabilization and Dynamic of Premixed Swirling Flames Book
Author : Paul Palies
Publisher : Academic Press
Release : 2020-07-03
ISBN : 0128199970
Language : En, Es, Fr & De

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Book Description :

Stabilization and Dynamic of Premixed Swirling Flames: Prevaporized, Stratified, Partially, and Fully Premixed Regimes focuses on swirling flames in various premixed modes (stratified, partially, fully, prevaporized) for the combustor, and development and design of current and future swirl-stabilized combustion systems. This includes predicting capabilities, modeling of turbulent combustion, liquid fuel modeling, and a complete overview of stabilization of these flames in aeroengines. The book also discusses the effects of the operating envelope on upstream fresh gases and the subsequent impact of flame speed, combustion, and mixing, the theoretical framework for flame stabilization, and fully lean premixed injector design. Specific attention is paid to ground gas turbine applications, and a comprehensive review of stabilization mechanisms for premixed, partially-premixed, and stratified premixed flames. The last chapter covers the design of a fully premixed injector for future jet engine applications. Features a complete view of the challenges at the intersection of swirling flame combustors, their requirements, and the physics of fluids at work Addresses the challenges of turbulent combustion modeling with numerical simulations Includes the presentation of the very latest numerical results and analyses of flashback, lean blowout, and combustion instabilities Covers the design of a fully premixed injector for future jet engine applications

Combustion Dynamics and Fluid Mechanics in Acoustically Perturbed Non premixed Swirl stabilized Flames

Combustion Dynamics and Fluid Mechanics in Acoustically Perturbed Non premixed Swirl stabilized Flames Book
Author : Uyi O. Idahosa
Publisher : Unknown
Release : 2010
ISBN : 0987650XXX
Language : En, Es, Fr & De

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The prevalence of gas turbines operating in primarily lean premixed modes is predicated on the need for lower emissions and increased efficiency. An enhancement in the mixing process through the introduction of swirl in the combustion reactants is also necessary for flame stabilization. The resulting lean swirling flames are often characterized by a susceptibility to feedback between velocity, pressure and heat release perturbations with a potential for unstable self-amplifying dynamics. The existing literature on combustion dynamics is predominantly dedicated to premixed flame configurations motivated by power generation and propulsive gas turbine applications. In the present research effort, an investigation into the response of atmospheric, non-premixed swirling flames to acoustic perturbations at various frequencies (f[subscript p] = 0-315Hz) and swirl intensities (S=0.09 and S=0.34) is carried out. The primary objective of the research effort is to broaden the scope of fundamental understanding in flame dynamics in the literature to include non-premixed swirling flames. Applications of the research effort include control strategies to mitigate the occurrence of combustion instabilities in future power generation gas turbines. Flame heat release is quantitatively measured using a photomultiplier with a 430nm bandpass filter for observing CH* chemiluminescence which is simultaneously imaged with a phase-locked CCD camera. Acoustic perturbations are generated with a loudspeaker at the base of an atmospheric co-flow burner with resulting velocity oscillation amplitudes, [vertical line]u'/U[subscript avg][vertical line] in the 0.03-0.30 range. The dependence of flame dynamics on the relative richness of the flame is investigated by studying various constant fuel flow rate flame configurations. The effect of varying fuel flow rates on the flame response is also examined using with dynamic time-dependent fuel supply rates over the data acquisition period. The Particle Image Velocimetry (PIV) method is used to study the isothermal flow field associated with acoustic pulsing. The acoustic impedance, wavelet analysis, Rayleigh criteria and phase conditioning methods are used to identify fundamental mechanisms common to highly responsive flame configurations.

Swirl stabilized Lean premixed Flame Combustion Dynamics An Experimental Investigation of Flame Stabilization Flame Dynamics and Combustion Instability Control Strategies

Swirl stabilized Lean premixed Flame Combustion Dynamics  An Experimental Investigation of Flame Stabilization  Flame Dynamics and Combustion Instability Control Strategies Book
Author : Rajavasanth Rajasegar
Publisher : Unknown
Release : 2018
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

Download Swirl stabilized Lean premixed Flame Combustion Dynamics An Experimental Investigation of Flame Stabilization Flame Dynamics and Combustion Instability Control Strategies book written by Rajavasanth Rajasegar, available in PDF, EPUB, and Kindle, or read full book online anywhere and anytime. Compatible with any devices.

Swirling Flows and Flames

Swirling Flows and Flames Book
Author : Toufik Boushaki
Publisher : BoD – Books on Demand
Release : 2019-06-26
ISBN : 1838807438
Language : En, Es, Fr & De

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Book Description :

Swirl flows are used in a wide range of industrial applications. In non-reacting cases, examples of applications include vortex amplifiers and reactors, heat exchangers, jet pumps, and cyclone separators. In reacting cases, swirlers are widely used in combustion systems, such as gas turbines, industrial furnaces, boilers, gasoline and diesel engines, and many other practical heating devices. Effects of using swirl on flow and combustion are significant and varied, and concern, for example, aerodynamics, mixing, flame stability, intensity of combustion, and pollutant emissions. The purpose of this book is to present recent research efforts to understand and characterize swirling flows of different types and in different applications. These include gaseous, liquid, and solid fuels in order to enhance combustion systems and their energy efficiency. Swirl flows are very complex and the studies proposed in this project are based on different means, including theoretical calculations, numerical modeling, and experimental measurements.

ASME Technical Papers

ASME Technical Papers Book
Author : Anonim
Publisher : Unknown
Release : 2001
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

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International Aerospace Abstracts

International Aerospace Abstracts Book
Author : Anonim
Publisher : Unknown
Release : 1999
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Energy Research Abstracts

Energy Research Abstracts Book
Author : Anonim
Publisher : Unknown
Release : 1992
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

Includes all works deriving from DOE, other related government-sponsored information and foreign nonnuclear information.

Flame Structure and Stabilization in Premixed Swirl stabilized Combustion

Flame Structure and Stabilization in Premixed Swirl stabilized Combustion Book
Author : Craig L. Beyler
Publisher : Unknown
Release : 1981
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Download Flame Structure and Stabilization in Premixed Swirl stabilized Combustion book written by Craig L. Beyler, available in PDF, EPUB, and Kindle, or read full book online anywhere and anytime. Compatible with any devices.

AIAA Aerospace Sciences Meeting and Exhibit 42nd

AIAA Aerospace Sciences Meeting and Exhibit  42nd Book
Author : Anonim
Publisher : Unknown
Release : 2004
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

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34th AIAA ASME SAE ASEE Joint Propulsion Conference Exhibit

34th AIAA ASME SAE ASEE Joint Propulsion Conference   Exhibit Book
Author : Anonim
Publisher : Unknown
Release : 1998
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

Download 34th AIAA ASME SAE ASEE Joint Propulsion Conference Exhibit book written by , available in PDF, EPUB, and Kindle, or read full book online anywhere and anytime. Compatible with any devices.

Impact of Fuel and Oxidizer Composition on Premixed Flame Stabilization in Turbulent Swirling Flows

Impact of Fuel and Oxidizer Composition on Premixed Flame Stabilization in Turbulent Swirling Flows Book
Author : Soufien Taamallah
Publisher : Unknown
Release : 2016
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

The world relies on fossil fuels as its main energy source (86.7% in 1973, 81.7% in 2012). Several factors including the abundance of resources and the existing infrastructure suggest that this is likely to continue in the near future (potentially 75% in 2040). Meanwhile climate change continues to be a pressing concern that calls for the development of low CO2 energy systems. Among the most promising approaches are pre-combustion capture technologies, e.g., coal gasification and natural gas reforming that produce hydrogen-rich fuels. Another approach is oxy-combustion in which air is replaced by a mixture of O2/CO2/H2O as the oxidizer stream. However, modern gas turbines have been optimized to operate on methane-air combustion and several challenges, notably thermo-acoustic instability, arise when using other fuels or oxidizers because of their different thermochemical and transport properties. While these phenomena constitute a major challenge under conventional operations, using hydrogen-rich fuels or CO2-rich oxidizer exacerbates the problem by modifying the combustor stability map in ways that are not well understood. In this thesis, we identify combustion modes most prone to dynamics, predict the onset of thermo-acoustic instability over a wide range of fuel and oxidizer compositions, and define parameters that can scale the data. To this end, a combination of experimental and numerical tools were deployed. We carried out a series of experiments in an optically accessible laboratory-scale swirl-stabilized combustor typical of those found in modern gas turbines, using high-speed chemiluminescence to examine the flame macrostructure; high-speed Particle Image Velocimetry and OH Planar Laser Induced Fluorescence to probe the flow and flame microstructure. Numerical simulations were used to complement experiments and examine the complex three-dimensional two-way interaction between the flame and the turbulent swirling flow. Experimental data were used to construct the stability maps for different CH4-H2 mixtures and analyze the dynamic flame macrostructures and their transitions. A comparison with acoustically uncoupled combustion shows that the onset of thermo-acoustic instability is concomitant with a specific transition associated with the intermittent appearance of the flame in the outer recirculation zone (ORZ) and stabilization along the outer shear layer (forming between the swirling jet and the ORZ, as revealed by the PIV-PLIF data). The sudden onset of large amplitude limit cycle oscillations and the observed hysteresis suggest the existence of a sub-critical Hopf bifurcation typically characterized by a bistable or "triggering" zone; the flame intermittency in the ORZ can potentially provide the disturbance required to trigger these oscillations. Using a dual-camera method to track chemiluminescence in space and time, this flame transition was found to originate from a reacting kernel that detaches from the inner shear layer flame (forming between the jet and the vortex breakdown zone), reaching the ORZ and spinning at a specific frequency; its characteristic Strouhal number is independent of the Reynolds number and the fuel/oxidizer, only a function of the swirl strength. We propose a new Karlovitz number based criterion that defines the transition on a flow time - flame time space, the former being the inverse of the spinning frequency and the latter being the flame extinction strain rate. According to this scaling, the flame survives in the ORZ if and when it can overcome the region's bulk strain rate. This criterion is valid over a wide range of operating, fuel and oxidizer composition, covering a wide range of fast to slow chemistry scenarios. Given the role of this flame transition in triggering the instability, the same criterion is applicable to predicting the onset of thermo-acoustics. The interaction of the turbulent swirling flow with the flame is further examined using large eddy simulations. Numerical simulations show that the experimentally observed large scale flame structures along the inner shear layer are due to a helical vortex core that originates at the swirler's centerbody. This vortical structure stays aligned with the centerline in the combustor upstream section, but bends and reaches the inner shear layer-stabilized flame around the sudden expansion where it causes the flame wrinkling. We propose that the flame kernel igniting the ORZ/ OSL observed in the experiment may be related to the interaction between the helical vortical structure and the outer shear layer.

Chemical Abstracts

Chemical Abstracts Book
Author : Anonim
Publisher : Unknown
Release : 2002
ISBN : 0987650XXX
Language : En, Es, Fr & De

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40th AIAA Aerospace Sciences Meeting Exhibit

40th AIAA Aerospace Sciences Meeting   Exhibit Book
Author : Anonim
Publisher : Unknown
Release : 2002
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Government Reports Announcements Index

Government Reports Announcements   Index Book
Author : Anonim
Publisher : Unknown
Release : 1994
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Dynamics of Deflagrations and Reactive Systems flames

Dynamics of Deflagrations and Reactive Systems  flames Book
Author : A. L. Kuhl
Publisher : AIAA (American Institute of Aeronautics & Astronautics)
Release : 1991
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

The four companion volumes on Dynamics of Deflagrations and Reactive Systems and Dynamics of Detonations and Explosions present 91 of the149 papers given at the Twelfth International Colloquium on the Dynamics of Explosions and Reactive Systems (ICDERS) held at the University of Michigan in Ann Arbor during July 1989. Four volumes: Dynamics of Deflagrations and Reactive Systems: Flames (Volume 131) and Dynamics of Deflagrations and Reactive Systems: Heterogeneous Combustion (Volume 132) span a broad area, encompassing the processes of coupling the exothermic energy release with the fluid dynamics occurring in any combustion process. Dynamics of Detonations and Explosions: Detonations (Volume 133) and Dynamics of Detonations and Explosions: Explosion Phenomena (Volume 134) principally address the rate processes of energy deposition in a compressible medium and the concurrent nonsteady flow as it typically occurs in explosion phenomena. In this volume, Dynamics of Detonations and Explosions: Detonations, the papers have been arranged into chapters on gaseous detonations, detonation initiation and transmission, nonideal detonations and boundary effects, and multiphase detonations. Although the brevity of this preface does not permit the editors to do justice to all papers, we offer the following highlights of some of the especially noteworthy contributions.

Forced Response of Swirl Stabilized Flames in Hydrogen Enriched Gas Turbines

Forced Response of Swirl Stabilized Flames in Hydrogen Enriched Gas Turbines Book
Author : Kyu Tae Kim
Publisher : Unknown
Release : 2009
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

The forced response of swirl-stabilized lean-premixed turbulent flames to inlet velocity and/or equivalence ratio oscillations in hydrogen enriched laboratory-scale gas turbine combustors was experimentally investigated. To characterize the response of premixed and partially premixed flames, several measurement techniques were used. Inlet velocity and equivalence ratio fluctuations were measured by the two-microphone method and the infrared absorption technique, respectively. Global heat release oscillations were determined by measuring naturally occurring flame chemiluminescence emissions using photomultiplier tubes. Steady-state flame structure and phase-resolved flame dynamics were characterized by CH* chemiluminescence imaging using an intensified CCD camera. Results show that the response of a premixed flame to inlet velocity oscillations is strongly dependent on the effective flame length. This extends previous experimental and analytical results from laminar to turbulent premixed flames. The nonlinear response of the flame is manifested by shear layer rollup and unsteady flame liftoff, depending on the amplitude of perturbations. The response of hydrogen-enriched flames is linear, irrespective of vortex shedding. The forced response of a flame to equivalence ratio oscillations alone was achieved by using a fuel modulation method. When the flame is perturbed by mixture ratio modulations, it shows both linear and nonlinear responses. The nonlinearity is associated with the intrinsically nonlinear dependence of burning velocity and equivalence ratio upon the heat release. Finally, the response of a partially premixed flame to perturbations of both inlet velocity and equivalence ratio was studied. Unsteady local extinction events were identified as a mechanism of nonlinearity, which results from flame stretching effects. In particular, unsteady local extinction is more obvious in the nonlinear dynamics of hydrogen enriched partially premixed flames. The phase difference between inlet velocity and equivalence ratio nonuniformities is a key parameter controlling the linear and nonlinear response of a partially premixed flame. Results also show that in the linear regime, the response of a partially premixed flame can be reconstructed using the responses of a flame to velocity and equivalence ratio, using a vector summation rule.

29th AIAA Fluid Dynamics Conference

29th AIAA Fluid Dynamics Conference Book
Author : Anonim
Publisher : Unknown
Release : 1998
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

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