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Showing 1 to 20 of 28 for “"Flame Dynamics"”.
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Vortex driven flame dynamics and combustion instability
… due to the coupling between heat release rate dynamics and system acoustics. It is crucial to understand the instability mechanisms to design reliable, high efficiency, low emission gas turbine combustors. In this thesis, elementary processes acting as a source of unsteady heat release rate are …
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Physics-based flame dynamics modeling and thermoacoustic instability mitigation
… for thermoacoustic instabilities under different flame anchoring configurations, (ii) to develop reduced-order models to predict the dynamic flame response, and (iii) to develop passive instability mitigation strategies by modifying the dynamics of the flame anchoring zone. The two different …
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Investigation of Ozone Initiated Ethylene Oxidation at Room Temperature: Chemistry and Flame Dynamics
… the effect of ozonolysis reaction on laminar flame dynamics is studied. Stable C2H4 lifted flames are established with oxygen/nitrogen co-flow at reduced oxygen content conditions. By adding certain amounts of O3 into the oxidizer co-flow, non-monotonic flame dynamic behaviors are recorded. …
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Large eddy simulations of premixed turbulent flame dynamics : combustion modeling, validation and analysis
… To achieve these objectives, lean premixed flames are generally preferred as they achieve efficient and clean combustion. A drawback of lean premixed combustion, however, is that the flames are more prone to dynamics. The unsteady release of sensible heat and flow dilatation in combustion …
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Spatially Resolved Analysis of Flame Dynamics for the Prediction of Thermoacoustic Combustion Instabilities
… lean premixed combustion, which results in lower flame temperatures and therefore the possibility of significantly reduced nitric oxide emissions. While lean premixed combustion offers reduced environmental impacts, it has been observed to experience increased possibility of the occurrence of …
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Determination of Flame Dynamics for Unsteady Combustion Systems using Tunable Diode Laser Absorption Spectroscopy
… emissions. Unfortunately, operating the flame at lean conditions increases susceptibility to thermoacoustic (TA) instability. Self-excited TA instabilities are a result of the coupling of the unsteady heat release rate of the flame with the acoustics of the combustion chamber. The result …
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Swirl-stabilized lean-premixed flame combustion dynamics: An experimental investigation of flame stabilization, flame dynamics and combustion instability control strategies
… two decades which allows for visualization of flame structure and behavior. However, resolving both temporal and spatial structures from image-based experimental data can be very challenging. Thus, understanding flame dynamics remains a demanding task and the difficulties often lie in the …
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Flame front imaging and ignition performance of ultra-compact trapped-vortex combustor
In this study, the flame dynamics and ignition performance of a novel ultra-compact trapped-vortex combustor, the ARC-S1, is investigated. Time-averaged OH* chemiluminescence was used to visualize flame anchoring and distribution inside the combustor. High-speed OH* PLIF imaging was conducted at …
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A Study of the Dynamics of Laminar and Turbulent Fully and Partially Premixed Flames
… towards developing reduced order models for the dynamics of laminar flat flames, swirl stabilized turbulent flames, and in evaluating the effects of the variation in fuel composition on flame dynamics. The laminar flat flame study was conducted on instrument grade methane, propane, and ethane …
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Linear Stability Analysis of a Rijke Tube and Modeling of Turbulent Combustion Using Dynamic Well-Stirred Reactors
… forcing term derived from a one-dimensional flame dynamics model. The new two-term acoustic forcing term, which is comprised of the summation of chemical heat release rate and heat transfer due to convection, correctly predicts instability where older models of acoustic forcing based solely …
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Analytical and Computational Study of Flame Acceleration in Tubes: Effect of Wall Friction
Premixed flame acceleration is especially strong in the case of flame propagation in tubes or channels. Being a reasonably simple configuration to investigate fundamental flame properties, combustion tubes have numerous practical applications such as safety issues in mines, subways and power …
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Model-based active control of thermoacoustic instability in continuous combustion processes
… The model considers the linear acoustic and flame dynamics, acoustic mode coupling, and actuator dynamics. Several model-based control designs including proportional, phase-lead, and LQG are presented and tested on the bench-top combustor using a 0.2 W loudspeaker as an actuator. Results show …
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Reduced-Order Models for the Prediction of Unsteady Heat Release in Acoustically Forced Combustion
… turbulent, laminar, and the moderately turbulent flamelet regime. Particular emphasis is placed on simplification of the models to facilitate analytical solutions while still reflecting real phenomenology. Each derivation is treated by beginning with general reacting flow equations, identifying a …
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Combustion Physics and Inverse Modeling of Energetic Materials
… involves intricate multi-scale and multi-phase dynamics, where the interplay of chemical reaction and transport processes results in complex wave patterns across a wide range of length scales from nano to millimeter. Our limited fundamental understanding of these combustion processes poses a …
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Implementation of Adaptive Filter Algorithms for the Suppression of Thermoacoustic Instabilities
… a first order low pass filter to simulate the flame dynamics of an unstable tube combustor. The second was a flat flame, methane-air Rijke tube. The third can be considered a quasi-LDI liquid fuel combustor with a thermal output of approximately 30 kW. Actuation included the use of an acoustic …
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Hydrodynamic stability of a premixed flame subjected to transverse shear
Flame instabilities arise intrinsically in combustion systems and have important implication in the operation of engineering devices. The primary intrinsic instability of premixed combustion is caused by thermal gas-expansion, known as the hydrodynamic or the Darrieus-Landau (DL) instability. …
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Nanosecond Pulsed Plasmas in Dynamic Combustion Environments
… envelopes with a low energy cost relative to flame power. It has been investigated for use in various situations, particularly those where combustion is being performed near flammability limits imposed by equivalence ratio, residence time, etc. While the fundamental processes allowing plasma …
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Development of high-speed laser diagnostics for the study of advanced propulsion systems
… of exploring the chemistry and fluid dynamics of complex reacting flows. The primary objective of this study is to develop and apply kHz-rate planar imaging to further our understanding of ignition and flame dynamics in turbulent flames relevant to next-generation propulsion systems. …
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Acoustic Transfer Functions Derived from Finite Element Modeling for Thermoacoustic Stability Predictions of Gas Turbine Engines
… reduced to dominant physics which depend only on flame dynamics and acoustics. This is the general approach adopted in this research. The primary objective of this thesis is to describe how to obtain acoustic transfer functions using finite element modeling. These acoustic transfer functions can …
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Characteristics of flame-turbulence interactions in freely propagating turbulent premixed flames under decaying and forced isotropic turbulence conditions
Turbulent premixed flames observed in energy conversion and propulsion applications are characterized by highly nonlinear, unsteady, and multi-scale processes. Previous numerical studies of freely propagating flames have utilized either forced or decaying background isotropic turbulence to provide …
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