Organizational Unit:
Daniel Guggenheim School of Aerospace Engineering
Daniel Guggenheim School of Aerospace Engineering
Permanent Link
Research Organization Registry ID
Description
Previous Names
Parent Organization
Parent Organization
Organizational Unit
Includes Organization(s)
Organizational Unit
Organizational Unit
Organizational Unit
Organizational Unit
Organizational Unit
ArchiveSpace Name Record
Publication Search Results
Now showing
1 - 10 of 36
-
ItemAssessment and Analysis of Turbulent Flame Speed Measurements of Hydrogen-Containing Fuels(Georgia Institute of Technology, 2023-08-14) Johnson, HendersonGlobal efforts to reduce greenhouse gas emissions and achieve a carbon-neutral economy have spurred the exploration of integrating hydrogen into various aspects of the global energy infrastructure. This can involve incorporating hydrogen into existing power generation applications or utilizing fuels with significant hydrogen content, such as syngas. However, the introduction of hydrogen poses significant challenges due to its potential to greatly impact the combustion process, with many aspects of its behavior not yet fully understood under practical gas turbine operating conditions. This thesis aims to investigate the influence of thermodynamic, fluid mechanic, and fuel factors on the turbulent global consumption speed, ST,GC, across different fuel types containing up to 90% hydrogen. This parameter represents the average rate of conversion of reactants to products relative to a specific iso-surface. The presented database encompasses three distinct fuel types: H2/CO, H2/CO/CH4/N2, and H2/CH4¬, which represent fuels that are either commonly encountered in practical applications or are of interest for future applications. The latter two fuels are new to the overall Georgia Tech database of turbulent flame speed measurements which increase the amount of high pressure data (up to 20 atm), and add data at preheat temperatures up to 500 K. The addition of this data is of great importance as it allows for further exploration of thermodynamic and fuel effects on ST,GC¬. The analysis of this database reveals several key findings. Firstly, regardless of whether the unstretched laminar flame speed, SL,0, is held constant, higher pressures lead to an increase in ST,GC across all fuel types. The preheat temperature is also shown to increase ST,GC, but when normalized by the laminar flame speed, it demonstrates a decrease. Moreover, the effects of hydrogen addition in H2/CO and H2/CO/CH4/N2 fuel blends are more pronounced compared to those in H2/CH4 fuels. Building upon prior studies that link these observations to mixture stretch sensitivity, the database is analyzed within the framework of a quasi-steady leading points concept model. In this framework, the maximum stretched laminar flame speed, SL,max, serves as the normalizing parameter. This approach proves effective for the H2/CO fuels discussed in this work, as it captures fuel effects at a fixed pressure and preheat temperature. However, a notable limitation arises in its inability to account for systematic differences in pressure and preheat temperature, indicating the need for a second correlating parameter. To identify this second parameter, a systematic investigation of three additional dimensionless numbers, namely the turbulent Reynolds number, Ret, time scale ratio, and acceleration ratio, is presented. Each of these numbers represents a different physical phenomenon that could potentially account for the observed variation in the data reported. The addition of Ret was considered in prior work; however, we identify that is insufficient as an appropriate scaling number due to its inconsistent correlation with preheat temperature. The acceleration ratio was introduced as a novel means of attempting to capture the ability of a flame to accelerate relative to the flow field. Similar to the Reynolds number, this approach showed limited ability to capture both pressure and preheat temperature effects; nevertheless, it does offer a new way to think about turbulence-flame interactions. Ultimately, the time scale ratio emerges as the optimal second correlating parameter due to its lesser degree of scatter compared to the acceleration ratio. This finding is significant, as it aligns with prior analyses that incorporated the time scale ratio to quantify non-quasi-steady chemistry effects at the leading point and demonstrates its promise as an appropriate scaling approach across a wide variety of conditions.
-
ItemNonlinear Dynamics of Coupled Thermoacoustic Modes in the Presence of Noise(Georgia Institute of Technology, 2022-07-30) John, TonyThis thesis investigates the dynamics of nonlinearly coupled thermoacoustic modes in the presence of noise. The dynamics of a single linearly unstable thermoacoustic mode has been extensively studied in literature. Typically, practical combustion systems consist of multiple thermoacoustic modes that are linearly stable or unstable at a wide range of frequencies. These modes can express independently or can interact with each other. The interactions between different modes is a strong function of the frequency spacing between them amongst other parameters such as its linear growth/decay rate, mode shapes etc. Studies have shown that, in a configuration with two linearly unstable modes, these modal interactions could lead to the suppression of one of the modes, and under certain conditions the more unstable mode (higher growth rate) can be suppressed. Frequency spacing between the modes particularly influenced the stability and existence of potential limit cycle solutions. In this work, the earlier studies are extended to include the effects of noise in the system, studying how deterministic dynamics change with the addition of noise and the impact of frequency spacing (i.e., closely or widely spaced) on the results. Noise can broaden the distribution of amplitudes (”diffusion”), change both the average limit cycle amplitudes (”drift”), and alter the bifurcation characteristics of the limit cycle solutions. In order to identify these noise-induced features, a local asymptotic analysis is performed to characterize the diffusive effects in the limit of low noise intensity. The width of the distribution is observed to be sensitive to frequency spacing and the variation in width along the limit cycle can be significant for widely spaced modes. Drift effects of noise are characterized by quantifying the shift in the averaged solutions from the deterministic values and the sensitivity of this shift to frequency spacing is explored. Further, bifurcation scenarios that exist due to symmetric/asymmetric coupling as well as those introduced by noise are identified. Examples are presented that show the dynamics of the system in its ensemble averaged state space and numerically obtained probability density functions (PDFs) are used to support the observations in the ensemble averaged state space. For certain frequency spacing and low noise intensity, two fixed points can be observed in the phase space and the most probable solution can be identified from the PDFs as well as by visually observing the domain of attraction for the fixed points. As the noise intensity is increased, changes in the qualitative features of the system are evident in the ensemble averaged state space and PDFs.
-
ItemKinetic-hydrodynamic instability interactions in near blowoff bluff body flames(Georgia Institute of Technology, 2022-05-02) Manosh Kumar, RaghulThis work examines the dynamics of confined bluff body flames in the process of lean blowoff (LBO) using simultaneous stereo-PIV (particle image velocimetry), OH PLIF (planar laser induced fluorescence) and CH2O PLIF. Flames at high density ratios blow off in at least two distinct stages: stage 1, where intermittent extinction occurs along the flame front, but the flame and flow remain qualitatively similar to stable conditions, and stage 2, where there is permanent downstream flame extinction and large-scale changes in dynamic flow characteristics. This work particularly focuses on stage 2 processes, with the goal of understanding what ultimately leads to irrecoverable flame blowoff. A new test facility was developed with the operational flexibility to achieve two goals: (1) approach LBO by keeping the parameters that influence its hydrodynamic stability approximately constant, particularly flow velocity (u_bulk) and gas expansion ratio (σ), and (2) compare near-LBO dynamics under conditions where, well away from blowoff, the flame is globally stable (high σ case) and globally unstable (low σ case, where the Bénard-Von Karman (BVK) instability of the flow is present). The latter case was of particular interest as most prior detailed diagnostic studies of LBO have been performed at high σ, BVK-suppressed conditions. We find, however, that the transient blowoff process remains largely unchanged in the high and low σ cases, presumably because the BVK instability reappears in either case under conditions very close to LBO. In all cases, blowoff is preceded by permanent downstream extinction that moves progressively closer to the bluff body as LBO is approached. We find that blowoff dynamics are intrinsically 3D, due to both secondary instabilities of the shear layer and confinement effects associated with bluff body-wall interactions. These 3D structures often manifest themselves as burning reactant fingers which are caught in the backflow of the recirculation zone; under very near LBO conditions they impinge on the back of the bluff body and extinguish. At the very edge of blowoff, the recirculation zone is no longer composed of hot products and is unable to autoignite the oncoming reactant flow, leading to global extinction. The characteristic time associated with this feedback between downstream extinction and wake structure alteration causing blowoff is about 2 orders of magnitude larger than the characteristic flow time, D/u_bulk.
-
ItemShear layer dynamics of a reacting jet in a vitiated crossflow(Georgia Institute of Technology, 2020-12-01) Nair, VedanthThe jet in crossflow (JICF) is a canonical shear flow that is present in a number of practical configurations including industrial gas turbines. Its complex flow topology, heavily influenced by underlying hydrodynamic instabilities, makes it an attractive configuration to implement when the mixing performance is critical. Past studies analyzing the behavior of non-reacting jets have noted that the overall performance of JICF configurations can be tied to the behavior of the shear layer, which influences both near-field and far-field jet dynamics. As a result, techniques used to manipulate jet mixing and penetration, such as active jet modulation, require an understanding of the dominant instability characteristics of the shear layer. Although this configuration finds extensive use in reacting applications, the hydrodynamics of reacting flows are often fundamentally different from non-reacting flows, and few studies have analyzed the influence of heat release and reactions on JICF dynamics. In addition to varying the momentum flux ratio (J) and the density ratio (S) this study presents a novel method of systematically moving the flame position with respect to the shear layer to gauge its impact on shear layer stability. High speed optical diagnostics including Stereoscopic PIV, OH-PLIF and OH* chemiluminescence were used to quantify the flowfield and infer the behavior of the reaction zone. Moving the flame inside the shear layer was observed to significantly change the jet topology as the shear layer vortices (SLV) were completely suppressed. This was further quantified through a growth rate defined based on tracking the swirling strength of SLV structures. Other structural characteristics including the location of mixing transition were shown to be highly correlated with this extracted growth rate. Time-resolved velocity data was further used to quantify the shear layer spectrum by extracting the dominant instability frequencies and classify the instability behavior as convectively and globally unstable. In order to explain the observed instability behavior, the counter current shear layer (CCSL) model was used to extract an analogous stratification parameter (S’), which along with the counter current velocity (Λ) ratio was shown to capture the stability behavior of both non-reacting as well as reacting configurations.
-
ItemExperimental investigation of nitrogen oxide production in premixed reacting jets in a vitiated crossflow(Georgia Institute of Technology, 2019-09-03) Sirignano, Matthew DavisThe presented work describes the experimental investigation of nitrogen oxide (NOx) emissions from reacting jets in a vitiated crossflow (RJICF). It is motivated by interest in axial staging of combustion as an approach to reduce undesirable NOx emissions from gas turbine combustors operating at high flame temperatures (>1900K). In lean-premixed combustion, NOx levels are exponential functions of temperature and linear functions of residence time. Consequently, NOx production rates are high at such temperatures, and conventional combustor architectures are unable to simultaneously deliver low NOx and part-load operability. A RJICF is a natural means of implementing axial staging. Therefore, a fuller understanding of the governing processes and parameters regarding pollutant formation within this complex flow field is critical to the next generation of gas turbine technology advancement. It is clear that RJICF NOx production is a highly coupled process. A key challenge was decoupling the interdependent jet parameters in order to observe fundamental NOx production sensitivities. Data is presented for premixed jets injected into a vitiated crossflow of lean combustion products. The jets varied in: fuel selection (methane or ethane or a combination), equivalence ratio (0.8≤ϕjet≤9.0), momentum flux ratio (2≤J≤40), and exit geometry (pipe or nozzle). The crossflow temperatures ranged from 1350K – 1810K, and the reacting jets induced a bulk averaged temperature rise on the flow (ΔT) ranging from 75K – 350K. In addition, several data series were replicated with varied ethane/methane ratios at constant ϕjet to influence flame lifting independent of other parameters. Similarly, the jet exit geometry was varied to influence shear layer vortex growth rates. Overall, these data indicate that NOx emissions are largely determined by ΔT. However, significant variation was observed at constant ΔT levels. The data is consistent with the idea that this variation is controlled by the stoichiometry at which combustion actually occurs, referred to as ϕFlame. ϕFlame is influenced by ϕjet and pre-flame mixing of the jet and crossflow that, in turn, is a function of flame lift-off distance (LO), nozzle geometry, and crossflow temperature. The data highlights the importance of flame lifting as well as the potential importance of post-flame mixing effects. Both are complex problems and are not directly addressed in this work. Further work in these areas would significantly deepen understanding of the relevant phenomena in RJICF NOx production.
-
ItemLean blowout sensitivities of complex liquid fuels(Georgia Institute of Technology, 2019-05-20) Rock, NicholasLean blowout is a process whereby a previously stable flame is either extinguished or convected out of its combustor. In aviation applications, blowout is a direct threat to passenger safety and it therefore sets operational limits on a combustor. Understanding the blowout problem is a key prerequisite to the deployment of alternative aviation fuels, as these fuels are expected to have comparable flame stability characteristics as traditional jet fuels. The objective of this work is to identify the fuel properties that govern lean blowout and to characterize their effect on the physics involved in the blowout process. The blowout performance of 18 different liquid fuels were experimentally compared in an aircraft relevant combustor. These experiments were repeated at 3 different air inlet temperatures, 300 K, 450 K, and 550 K, in order to vary the effect of fuel physical properties. Custom fuels were introduced that were specifically designed to decouple interrelated fuel properties and to accentuate the significance of preferential vaporization on lean blowout. The methodology that was used clearly demonstrated differences in the equivalence ratio at blowout between fuels, and a multiple linear regression analysis was performed to determine the relative contributions of each of the fuel properties. This work also characterizes the effect of fuel composition on the processes that precede blowout of the flame, thereby providing an explanation for why certain fuel properties govern lean blowout boundaries. By quantifying the time variation of flame luminosity and extinction “events” as a function of blowout proximity, it was demonstrated that local extinction processes are operative in and lead to blowout in spray flames. In addition, high speed imaging was used to analyze the space-time evolution of the most upstream point of the flame near blowout. Fast motion of these points upstream relative to the flow velocity was interpreted as flame re-ignition. These re-ignition processes become manifest when the stability of the flame is severely threatened by local extinction and often allow for recoveries that extend flame burning. Fuel composition was shown to have a clear effect on a flame’s propensity for extinction and re-ignition.
-
ItemTurbulence-chemistry interactions for lean premixed flames(Georgia Institute of Technology, 2018-10-09) Dasgupta, DebolinaTurbulent combustion, particularly premixed combustion has great practical importance due to their extensive industrial usage in gas turbines, internal combustion engines etc. However, the physics governing the inherent multi- scale interactions of turbulence, flow-field and chemistry is not yet well established. A complete understanding of each of these interactions and their coupling is essential for the development of models that can aid simulations of realistic engines (using Large Eddy Simulations (LES) or Reynolds averaged Navier-Stokes equations (RANS). Particularly, understanding the flame structure and its stabilization requires an understanding of the turbulence-chemistry interactions. This can manifest itself in many different forms. For example, flame wrinkling gives rise to flame stretch that can modify the local temperature and species concentrations in turn altering the local chemistry. Also, the smaller eddies in a turbulent flow can penetrate into the preheat and reaction zones changing the species’ gradients within the flame. The influence of turbulence on chemistry can be analyzed in two different ways: firstly, a “global” analysis which investigates the direct impact of turbulence on the chemical pathways (a series of elementary reactions involved in the fuel oxidation process) and secondly, a “local” analysis which investigates the influence of turbulence on the chemical flame structure (i.e. species and reaction rate profiles). To understand these influences of turbulence, this work performs Direct Numerical Simulations (DNS) for lean premixed flames involving three fuels: hydrogen, methane and n-dodecane. A “global” analysis using different metrics such as heat release and species consumption/production is performed to quantify the changes in the chemical pathways. This analysis is performed for the metrics averaged over the entire flame and conditioned on local flame features such as fuel consumption, curvature etc. The results are also compared and contrasted with simple laminar flame models such as unstretched flames, stretched flames and perfectly stirred reactors. In general, the laminar models provide a good estimate for the chemical pathways for these key metrics suggesting turbulence does not have a significant impact on the fuel oxidation pathways. However, this is not true for the reaction rate and species profiles across the flame. Conditional means of these quantities are calculated to identify the “local” influence of turbulence on chemistry. These conditional means are also compared with laminar unstretched and stretched flames to identify regions of good agreement and deviation. The laminar calculations are performed using two different transport models; firstly, the mixture-averaged transport wherein every species diffuses into the mixture with its molecular diffusivity and secondly, Le=1 transport wherein the mass diffusivity of every species is equal to the thermal diffusivity of the mixture eliminating effects of preferential and differential diffusion. Le=1 is considered the theoretical limit of transport where turbulent mixing governs the transport process opposed to molecular diffusivity. For lean hydrogen/air flames (Le<1), the behavior of the profiles is similar to the evolution of the laminar profiles with increasing stretch. However, for the lean methane/air flames (Le~1), with increasing turbulence intensity, the flame profiles deviate from the evolution of laminar profiles with increasing stretch and align more closely with the Le=1 transport model laminar flame profiles. For n-dodecane/air flames (Le>1), the evolution of the turbulent flame profiles, with slight increase in turbulence intensity, replicates the behavior of stretched flames. However, with a further increase, a deviation is seen from the stretched flame profiles. Additionally, these profiles significantly deviate from the Le=1 transport model suggesting the inadequacy of stretched flames and a simple Le=1 model to replicate the behavior of stretched flames. In order, to identify the effect of increased diffusivity due to turbulence, a new transport model is implemented for unstretched and stretched flames wherein a constant is added to the mass diffusivity of the species obtained from the mixture-averaged transport. This constant covers multiple orders of magnitude mimicking the effect of increased turbulence diffusivity. For the lean hydrogen flames(Le<1), the turbulent flame profiles are seen to evolve similar to the laminar profiles with increasing stretch and not similar to the laminar profiles with increasing diffusivity. This suggests mixtures containing a highly diffusive fuel does not need the aid of turbulence to enhance transport. For the lean methane flames (Le~1), the turbulent flame profile evolution is similar to the effect of increasing diffusivity for unstretched flames suggesting a significant effect of diffusivity on the flame structure. For the lean n-dodecane flames (Le>1), the turbulent flame profiles evolve similar to the effect of increased diffusivity on stretched flames. This further emphasizes the necessity to include diffusivity in laminar models used to replicate turbulent flame structure. Overall, this work helps identify the key players in turbulence-chemistry interactions which need to be considered for modeling real combustors.
-
ItemExperimental investigation of transverse acoustic instabilities(Georgia Institute of Technology, 2017-11-09) Smith, Travis EdwardThis work presents 5 kHz stereo PIV and OH PLIF measurements as well as OH* and CH* chemiluminescence measurements of transversely forced swirl flames. The presence of transverse forcing on this naturally unstable flow both influences the natural instabilities, as well as amplifies disturbances that may not necessarily manifest themselves during natural oscillations. By manipulating the structure of the acoustic forcing field, both axisymmetric and helical modes are preferentially excited away from the frequency of natural instability. Additionally, forced and self-excited transverse acoustic instability studies to date have strong coupling between the transverse and axial acoustic fields near the flame. This is significant, as studies suggest that it is not the transverse disturbances themselves, but rather the induced axial acoustic disturbances, that control the bulk of the heat release response. The work first presents a method for spatially interpolating the phase locked r-z and r-θ planar velocity and flame position data, extracting the full three-dimensional structure of the helical disturbances. These helical disturbances are also decomposed into symmetric and antisymmetric disturbances about the jet core, showing the subsequent axial evolution (in magnitude and phase) of each of these underlying disturbances. Then experiments performed with essentially the same transverse acoustic wave field, but with and without axial acoustics, show that significant heat release oscillations are only excited in the former case. The results show that the axial disturbances at the nozzle exit are the dominant cause of the heat release oscillations. These observations support the theory that the key role of the transverse motions is to act as the “clock” for the instability, setting the frequency of the oscillations while having a negligible direct effect on the actual heat release fluctuations. They also show that transverse instabilities can be damped by either actively canceling the induced axial acoustics in the nozzle (rather than the much larger energy transverse combustor disturbances), or by passively tuning the nozzle impedance to drive an axial acoustic velocity node at the nozzle outlet.
-
ItemFlow characterization of lifted flames in swirling, reacting flows(Georgia Institute of Technology, 2017-05-15) Chterev, Ianko PavlovSwirl stabilized combustors are commonly used in gaseous fueled land-based gas turbines and liquid fueled aerospace combustors to achieve simultaneously high efficiency, low emissions, wide operability limits, and low thermal and mechanical hardware loadings. Flame shape and location are critical to successful design, and are, therefore, the general focus of this work. In premixed swirl combustion aerodynamically stabilized flames are sometimes observed and desirable as they potentially reduce hardware heat loadings. However, their understanding is largely phenomenological and geometry specific. First, aerodynamically stabilized flames are subject to flow perturbations such as a precessing vortex core (PVC), and therefore, this thesis studies how a precessing flow field affects time-averaged quantities such as flame location. Second, in swirling flowfields with no interior time-averaged stagnation point, flames are sometimes aerodynamically stabilized by instantaneous stagnation points created by large scale structures such as the PVC. Since this places the flame in a time-averaged reverse flow, natural questions are what the flame and flow characteristics are at the flame stabilization location, such as flame stretch, and why the flame does not flash back. Experiments in high pressure, multi-phase, hydrocarbon fueled, reacting flows are highly complex, and quantities such as liquid and gas phase fuel distribution, heat release and flowfield are difficult to obtain. Thus, another focus of this work is experimental development to study the internal physics. First, this thesis finds that precession in radial-axial planar measurements can result in the time-averaged stagnation point to be located in a highly negative region of the flow. Since the time-averaged flow field is often used to determine the flame location, these findings indicate that time-averaged treatments may lead to erroneous results. Precession can also alter the general flow field topology by inducing asymmetries and can cause time-averages to converge slower. Second, the local flow field of a flame aerodynamically stabilized by instantaneous stagnation points is characterized using planar velocity and flame location measurements, conditioned using a line-of-sight technique to capture the flame global leading in the imaging plane. The flame stretch is measured, indicating that the stretch the flame experiences has a high dependence on nozzle velocity. However, the scaling is not understood, and further study is proposed. The time-averaged flame stretch is much higher than opposed diffusion flame extinction stretch rate calculations, which also requires further study. Furthermore, the stretch is not correlated strongly with location and flow velocity. Last, a simultaneous stereo-PIV and fuel/OH-PLIF technique is developed using a single PLIF laser (and a PIV laser) to characterize the spray distribution, flame shape and location, and dual phase flow field for two different jet fuels, at pressures from 2 to 5 bar. Two different flame shapes are observed, with a stability behavior different than with gaseous fuel. Furthermore, the flames extends into the annular jet core, a phenomenon not observed in premixed systems, and mentioned as needing verification in the liquid fueled combustion literature.
-
ItemEnsemble-averaged dynamics of premixed, turbulent, harmonically excited flames(Georgia Institute of Technology, 2017-04-07) Humphrey, LukeIncreasing awareness of the negative impacts of pollutant emissions associated with combustion is driving increasingly stringent regulatory limits. In particular, oxides of nitrogen, generally referred to as NOx, now face strict limits. These restrictions have driven development of cleaner burning combustion systems. Because NOx formation increases significantly at elevated temperatures, one method to reduce NOx emissions is to burn the fuel at lower temperatures. By premixing the fuel and oxidizer prior to combustion significantly lower flame temperatures can be achieved, with corresponding reductions in NOx emissions. Unfortunately, premixed combustion systems are generally more prone to potentially problematic feedback between the unsteady heat release from the flame and unsteady pressure oscillations. This self-excited feedback loop is known as combustion instability. Because these oscillations are associated with unsteady pressure fluctuations they can degrade system performance, limit operability, and even lead to catastrophic failure. Understanding combustion instability is the primary motivation for the work presented in this thesis. The interaction of quasi-coherent and turbulent flame disturbances changes the spatio-temporal flame dynamics and turbulent flame speed, yet this interaction is not fully understood. Therefore, this thesis concentrates on identifying, understanding, and modeling these interactions. In order to address this topic, two primary avenues of research are followed: development and validation of a flame position model and experimental investigations of predicted ensemble-averaged flame speed sensitivity to flame curvature. First, a reduced order modeling approach for turbulent premixed flames is presented, based on the ensemble-averaged flame governing equation proposed by Shin and Lieuwen (2013). The turbulent modeling method is based on the G-equation approach used in laminar flame position and heat release studies. In order to capture the dependence of the ensemble-averaged turbulent flame speed on the ensemble-averaged flame curvature, the turbulent flame model incorporates a flame speed closure proposed by Shin and Lieuwen (2013). Application of the G-equation approach in different coordinate systems requires the inclusion of time-varying integration limits when calculating global flame area. This issue is discussed and the necessary corrections derived. Next, the reduced order turbulent modeling approach is validated by comparison with three-dimensional simulations of premixed flames, for both flame position and heat release response. The reduced order model is the linearized, allowing development of fully analytical flame position and heat release expressions. The use of the flame speed closure is shown to capture nonlinear effects associated with kinematic restoration. Second, the development of and results from a novel experimental facility are described. This facility has the capability to subject premixed flames to simultaneous broadband turbulent fluctuations and narrowband coherent fluctuations, which are introduced on the flame using an oscillating flame holder. Mie scattering images are used to identify the instantaneous flame edge position, while simultaneous high speed PIV measurements provide flow field information. Results from this experimental investigation include analysis of the ensemble-averaged flame dynamics, the ensemble-averaged turbulent displacement speed, the local ensemble-averaged area and consumption speed, and the dependence of both the displacement speed and consumption speed on the ensemble-averaged flame curvature. Finally, the flame speed sensitivity to curvature is quantified through calculation of the normalized turbulent Markstein displacement and consumption numbers. The results show that the amplitude of coherent flame wrinkles generally decreases with both downstream distance and increasing turbulence intensity, providing the first experimental validation of previous isothermal results. The average displacement and consumption speeds increase with downstream distance and turbulence intensity, reflecting the increasing wrinkled flame surface. The ensemble-averaged, phase dependent displacement and consumption speeds demonstrate clear modulation with the shape of the ensemble-averaged flame. Specifically, these turbulent flame speeds increase in regions of negative curvature. For both the displacement and consumption speed, the magnitude of the normalized turbulent Markstein length increases with ratio of the turbulent flame wrinkling length to the coherent wrinkling length when u'/SL0 >2.5 . For u'/SL0 < 2.5 the trends are less clear due to the presence of convecting disturbances which introduce additional fine scale wrinkles on the flame. Together the results presented in this thesis provide a foundation for modeling turbulent flames in the presence of quasi-coherent disturbances. The flame position can be modeled using the ensemble-averaged governing equation with the dynamical flame speed closure, and the corresponding heat release can be calculated from the turbulent consumption speed closure. The turbulent Markstein numbers and uncurved flame speed may be extracted from experimental or numerical data.