Cinematographic stereoscopic PIV, combined with Taylor's frozen flow hypothesis, is used to generate three-dimensional (3D) quasi-instantaneous pseudo volumes of the three-component (3C) velocity field in the far field of turbulent nonpremixed jet flames at jet exit Reynolds number Reδ in the range 8,000-15,300. The effect of heat release, however, lowers the local (i.e., based on local properties) Reynolds number to the range 1,500-2,500. The 3D data enable computation of all nine components of the velocity gradient tensor ∇u from which the major 3D kinematic quantities, such as strain rate, vorticity, dissipation and dilatation, are computed. The volumetric PIV is combined with simultaneously acquired 10 Hz OH planar laser-induced fluorescence (PLIF). A single plane of the OH distribution is imaged on the center-plane of the volume and provides an approximate planar representation of the instantaneous reaction zone. The pseudo-volumes are reconstructed from temporally and spatially resolved kilohertz-rate 3C velocity field measurements on an end-view plane (perpendicular to the jet flame axis) invoking Taylor's hypothesis. The interpretation of the measurements is therefore twofold: the measurements provide a time-series representation of all nine velocity gradients on a single end-view plane or, after volumetric reconstruction, they offer a volumetric representation, albeit approximate, of the spatial structure of the flow. The combined datasets enable investigation of the fine-scale spatial structure of turbulence, the effect of the reaction zone on these structures and the relationship between the jet kinematics and the reaction zone. Emphasis is placed on the energy dissipation field and on the presence and role of dilatation. Statistics of the components of the velocity gradient tensor and its derived quantities show that these jet flames exhibit strong similarities to incompressible turbulent flows, such as in the distribution of the principal strain rates and strain-vorticity alignment. However, the velocity-gradient statistics show that these jet flames do not exhibit small-scale isotropy but exhibit a strong preference for high-magnitude radial gradients, which are attributed to regions of strong shear induced by the reaction zone. The pseudo volumes reveal that the intense-vorticity field is organized in two major classes of structures: tube-like away from the reaction zone (the classical worms observed in incompressible turbulence) and sheet-like in the vicinity of the local reaction zone. Sheet-like structures are, however, the dominant ones. Moreover, unlike incompressible turbulence where sheet-like dissipative structures enfold, but don't coincide with, clusters of tube-like vortical structures, it is observed that the sheet-like intense-vorticity structures tend to closely correspond to sheet-like structures of high dissipation. The primary reason for these features is believed to be due to the stabilizing effect of heat release on these relatively low local Reynolds number jet flames. It is further observed that regions of both positive and negative dilatation are present and tend to be associated with the oxidizer and fuel sides of the OH zones, respectively. These dilatation features are mostly organized in small-scale, short-lived blobby structures that are believed to be mainly due to convection of regions of varying density rather than to instantaneous heat release rate. A model of the dilatation field developed by previous researchers using a flamelet approximation of the reaction zone was used to provide insights into the observed features of the dilatation field. Measurements in an unsteady laminar nonpremixed jet flame where dilatation is expected to be absent support the simplified model and indicate that the observed structure of dilatation is not just a result of residual noise in the measurements, although resolution effects might mask some of the features of the dilatation field. The field of kinetic energy dissipation is further investigated by decomposing the instantaneous dissipation field into the solenoidal, dilatational and inhomogeneous components. Analysis of the current measurements reveals that the effect of dilatation on dissipation is minimal at all times (it contributes to the mean kinetic energy dissipation only by about 5-10%). Most of the mean dissipation arises from the solenoidal component. On average, the inhomogeneous component is nearly zero, although instantaneously it can be the dominant component. Two mechanisms are believed to be important for energy dissipation. Near the reaction zone, where the stabilizing effect of heat release generates layers of laminar-like shear and hence high vorticity, solenoidal dissipation (which is proportional to the enstrophy) dominates. In the rest of the ow the inhomogeneous component dominates in regions subjected to complex systems of nested vortical structures where the mutual interaction of interwoven vortical structures in intervening regions generates intense dissipation. / text

Combustion instability is a process which involves unsteady chemical kinetic, fluid mechanic, and acoustic processes. It can lead to unstable behavior and be detrimental in ways ranging from faster part fatigue to catastrophic system failure. In terms of combustion methodology, combustion instability has been a key issue for lean premixed combustion. The primary objective of this work is to improve understanding of combustion dynamics through an experimental study of lean premixed combustion using a low swirl combustor. This special burner was developed at the Lawrence Berkeley National Laboratory and has recently received significant interest from the gas turbine industry. In these experiments, acoustic perturbations (chamber modes) are imposed on a low swirl stabilized methane-air flame using loudspeakers. The flame response is examined and quantified with OH planar laser induced fluorescence. Rayleigh index maps of the flame are computed for each frequency and operating condition. Examining the structures in the Rayleigh maps, it is evident that, while the flame shows no significant response in some cases, acoustic forcing in the 70-150 Hz frequency range induces vortex shedding in the flame shear layer. These vortices distort the flame front and generate locally compact and sparse flame areas. This information about the flow field shows that, besides illuminating the combustion dynamics, the Rayleigh index is a useful way to reveal interesting aspects of the underlying flow. The experiments also revealed other interesting aspects of this flame system. It was found that the flame becomes unstable when the perturbation amplitude reaches 0.7% of the mean pressure. Decreasing the swirl number makes the flame shape more jet-like, but does little to alter the shear-layer coupling. In a similar fashion, increasing the pressure was found to alter the flame shape and flame extent, but the thermo-acoustic coupling and induced large scale structure persisted to 0.34MPa, the highest pressure tested.

La combustion diphasique implique de nombreux phénomènes physiques complexes, comprenant l'atomisation, la dispersion, l'évaporation et la combustion. Bien que la simulation numérique soit un outil performant pour aborder ces différentes interactions entre les phases liquides et gazeuses, la méthode doit être validée par des études expérimentales fiables. Par conséquent, des données expérimentales précises sur la structure de la flamme et sur les propriétés de la phase liquide et gazeuse le long des étapes d'évaporation et de combustion sont nécessaires. La complexité des configurations aéronautiques réelles implique d'étudier l'effet des propriétés locales sur la dynamique des flammes pour une configuration canonique. Ce travail, réalisé dans le cadre du projet ANR TIMBER, a pour objectif d'améliorer la compréhension de la combustion en flux diphasique, ainsi que de produire une base de données efficace et originale pour la validation des modèles utilisés dans les LES. / Liquid fuels are the primary energy source in a wide range of applications including industrial and residential furnaces, internal combustion engines and propulsion systems. Pollutant emission reduction is currently one of the major constraints for the design of the next generation combustion chamber. Spray combustion involves many complex physical phenomena including atomization, dispersion, evaporation and combustion, which generally take place simultaneously or within very small regions in the combustion chambers. Although numerical simulation is a valuable tool to tackle these different interactions between liquid and gas phases, the method needs to be validated through reliable experimental studies. Therefore, accurate experimental data on flame structure and on liquid and gas properties along the evaporation and combustion steps are needed and are still challenging. A joint effort between numerical and experimental teams is necessary to meet tomorrow's energy challenges and opportunities. The complexity of the real aeronautical configurations implies to study the effect of local properties in flame dynamics on a canonical configuration, which presents the essential feature of very well defined boundary conditions. This work, carried out within the framework of the ANR TIMBER project, aims to improve the understanding of two-phase flow combustion, as well as to produce an efficient and original database for the validation of the models used in LES.

Lean premixed combustors are highly susceptible to combustion instabilities, caused by the coupling between heat release fluctuations and combustor acoustics. In order to predict the conditions under which these instabilities occur and their limit cycle amplitudes, understanding of the amplitude dependent response of the flame to acoustic excitation is required. Extensive maps of the flame response were obtained as a function of perturbation amplitude, frequency, and flow velocity. These maps illustrated substantial nonlinearity in the perturbation velocity - heat release relationship, with complex topological dependencies that illustrate folds and kinks when plotted in frequency-amplitude-heat release space. A detailed analysis of phase locked OH PLIF images of acoustically excited swirl flames was used to identify the key controlling physical processes and qualitatively discuss their characteristics. The results illustrate that the flame response is not controlled by any single physical process but rather by several simultaneously occurring processes which are potentially competing, and whose relative significance depends upon forcing frequency, amplitude of excitation, and flame stabilization dynamics. An in-depth study on the effect of acoustic forcing on the turbulent flame properties was conducted in a turbulent Bunsen flame using PIV measurements. The results showed that the flame brush thickness and the local consumption speed were modulated in the presence of acoustic forcing. These results will not only be a useful input to help improve combustion dynamics predictions but will also help serve as validation data for models.

The current research focuses on the thermoacoustic instability of lean premixed combustion, which is a promising technique to inhibit Nitrogen Oxides (NOx) emission. Thermoacoustic instability describes the condition that the pressure oscillation is unusually high in the combustion device. It results from the coupling between pressure fluctuation and heat release oscillation, which experiences significant temporal and spatial variations. These variations are closely related to the flame shape deformation and critical in determining the trend of the global instability. Therefore, the current study aims to examine both the global and local flame features created by thermoacoustic instability. The first part of the work is studying the unstable flame induced by artificial acoustic perturbation. The particular focus is on the global and local heat release rate oscillation. In the experiment, the global heat release rate oscillation was indicated by the hydroxyl (OH*) chemiluminescence captured with a photomultiplier tube (PMT). On the other hand, the flame shape and the local mean heat release rate were examined with flame surface density (FSD), which was calculated with the images captured with the planar laser-induced fluorescence of the hydroxide radical (OH-PLIF) method. The main analysis methods used in the current research are Rayleigh criterion and proper orthogonal decomposition (POD), which can efficiently capture the dominant oscillation mode of the flame. The acoustic perturbation study first examined the effect of pressure variation (0.1 - 0.4 MPa) on the flame response to the acoustic perturbation. Results show that the elevated pressure intensifies the fundamental mode of heat release oscillation when the heat release oscillation is in phase with the pressure fluctuation; otherwise, the fundamental oscillation tends to be inhibited. The pressure affects both the strength and the distribution of the local fundamental and the first harmonic oscillations. Furthermore, the effect of the pressure on the distribution is larger than that on the strength. The study also investigated the role of Strouhal numbers in characterizing the flame oscillation induced by acoustic perturbation. Results show that the Strouhal number can characterize the changing trend of the oscillation amplitude, whereas the oscillation phase-delay is less dependent on the Strouhal number. The local analysis reveals that the nonlinear flame behavior results from the flame rollup induced by acoustic perturbation. Furthermore, the reconstruction of the global heat release shows that the cancellation of out-of-phase local oscillations can cause a low-level global oscillation. Results also demonstrate that the local heat release oscillation contains intense harmonic oscillations, which are closely associated with the flame rollup. However, the harmonic oscillation is less likely the main reason causing nonlinear flame behavior. Besides the study with acoustic perturbation, the current study also conducted experimental and modeling studies on the self-excited thermoacoustic instability. The particular focus is examining the effects of hydrogen addition on the instability trend. Results demonstrate that the hydrogen concentration can affect both the oscillation frequency and amplitude. Pressure analysis shows that the low-frequency mode is triggered when the hydrogen concentration is low, whereas a high hydrogen concentration tends to excite a high-frequency mode. Moreover, the frequency tends to increase with an increasing hydrogen concentration. Modeling results illustrate that the change of the oscillation mode, which is determined by the turbulent flame speed, is mainly affected by the delay time between the heat release oscillation and the velocity fluctuation. The modeling work shows that the one-dimensional model is not very efficient in capture the instability trend of the high-frequency mode. It may result from the lack of the knowledge of the mechanism of acoustic damping and flame dynamics.

Sustainable and low emission combustion requires new combustion paradigms and solutions to increase efficiency, comply with more stringent regulations on pollutants, and cope with the varying qualities of renewable fuels. Plasma Assisted Combustion (PAC) could be one of the tools to achieve these goals in practical combustion systems. Previous studies showed that PAC can be used in a variety of applications: to improve ignition in difficult environments, to extend the operating range of burners to leaner conditions, to contrast thermoacoustic instability, to allow flame-holding in extreme conditions, and more. While applications keep being proposed, there are efforts to model and understand the coupling between flames and plasma discharges. This work contributes to the unraveling of the action of plasma discharges on flames by performing a number of investigations on a simple PAC burner. Trends and temporal evolution of key chemical species and electric fields are measured during plasma actuation of the flame. Experimental datasets resulting from this work are meant to be used in cross-validating numerical simulations. The considered PAC burner generates a lean methane-air stagnation flame, across which discharges are applied, developing partially in the fresh and partially in the burned gases. Time-resolved 2D imaging of atomic hydrogen and oxygen is obtained by using two-photon absorption planar laser induced fluorescence (TALIF) while OH and CH radicals are measured by using planar laser induced fluorescence (PLIF). To measure the electric field, the Electric Field Induced Second Harmonic generation (EFISH) technique is used. A novel deconvolution-like post-processing procedure is proposed and used to calibrate the measurements and improve the spatial resolution, overcoming limitations and distortions typical of EFISH measurements. Presented results quantify the effect of the plasma actuation on the flame and lend themselves to the validation of numerical models.

Syngas, a gaseous mixture of H2, CO and diluents such as N2, CO2, is a clean fuel generated via gasification of coal or biomass. Syngas produced via gasification typically has low calorific values due to very high dilution levels (~60% by volume). It has been recognized as an attractive energy source for stationary power generation applications. The present work focuses on experimental and numerical investigation of syngas-air counterflow diffusion flames with varying composition of syngas. Laser-based diagnostic techniques such as Particle Imaging Velocimetry, Rayleigh thermometry and Laser-induced fluorescence have been used to obtain non-intrusive measurements of local extinction strain rates, temperature, quantitative OH and NO concentrations, respectively, for three different compositions of syngas. Complementing the experiments, numerical simulations of the counterflow diffusion flame have been performed to assess the performance of five H2/CO chemical kinetic mechanisms from the literature. The first part of the work involved determination of local extinction strain rates for six H2 /CO mixtures, with H2:CO ratio varying from 1:4 to 1:1. The extinction strain rates were observed to increase from 600 sec-1 to 2400 sec-1 with increasing H2:CO ratio owing to higher diffusivity and reactivity of the H2 molecule. Numerical simulations showed few mechanisms predicting extinction conditions within 5% of the measurements for low H2:CO ratios, however, deviations of 25% were observed for higher H2 :CO ratios. Sensitivity analyses revealed that the chain branching reactions, H+O2 <=>O+OH, O+H2 <=>H+OH and the third body reaction H+O2 +M<=>HO2 +M are the key reactions affecting extinction limits for higher H2:CO mixtures. The second phase of work involved quantitative measurement of OH species concentration in the syngas-air diffusion flames at strain rates varying from 35 sec-1 to 1180 sec-1. Non-intrusive temperature measurements using Rayleigh thermometry were made in order to provide the temperature profile necessary for full quantification of the species concentrations. The [OH] is observed to show a non-monotonous trend with increasing strain rates which is attributed to the competition between the effect of increased concentrations of H2 and O2 in the reaction zone and declining flame temperatures on the overall reaction rate. Although the kinetic mechanisms successfully captured this trend, significant deviations were observed in predictions and measurements in flames with H2:CO ratios of 1:1 and 4:1, at strain rates greater than 800 sec-1 . The key reactions affecting [OH] under these conditions were found to be the same reactions identified earlier during extinction studies, thus implying a need for the refinement of their reaction-rate parameters. Significant disagreements were observed in the predictions made using the chemical kinetic mechanisms from the literature in flames with high H2 content and high strain rate. The final phase of work focused on measurement of nitric oxide (NO) species concentrations followed by a comparison with predictions using various mechanisms. NO levels as high as ~ 48 ppm were observed for flames with moderate to high H2 content and low strain rate. Quantitative reaction pathway diagrams (QRPDs) showed thermal-NO, NNH and prompt-NO pathways to be the major contributors to NO formation at low strain rates, while the NNH pathway was the dominant route for NO formation at high strain rates. The absence of an elaborate CH chemistry in some of the mechanisms has been identified as the reason for underprediction of [NO] in the low strain rate flames. Overall, the quantitative measurements reported in this work serve as a valuable reference for validation of H2/CO chemical kinetic mechanisms, and the detailed numerical studies while providing an insight to the H2:CO kinetics and reaction pathways, have identified key reactions that need further refinement.

Ce travail porte sur la stabilisation de flammes prémélangées et swirlées de mélanges combustibles méthane/hydrogène/air avec différents taux de dilution d’azote et de dioxyde de carbone. Une tige centrale permet de stabiliser des flammes pour de faibles nombres de swirl. Le sommet de la flamme interagît éventuellement avec les parois de la chambre de combustion. L’objectif ces travaux est d’améliorer la connaissance des mécanismes qui gouvernent la stabilisation et la topologie de ces flammes. Ces travaux démontrent que le nombre de swirl, la composition du mélange combustible, la géométrie de la chambre de combustion ainsi que les conditions aux limites thermiques ont une grande influence sur la forme prise par la flamme. Le dispositif expérimental permet de modifier la forme et la taille de la chambre de combustion, le diamètre du tube d’injection et le nombre de swirl. Des conditions opératoires propices aux transitions de forme de flamme sont ensuite étudiées pour différentes configurations de brûleur. Une caractérisation expérimentale fouillée d’un point de fonctionnement est réalisée grâce à la Fluorescence Induite par Laser sur le radical Hydroxyle (OH-PLIF), la Vélocimétrie par Images de Particules (PIV) et la Phosphorescence Induite par Laser de phosphores sensibles à la température (LIP). Une base de donnée de l’écoulement et des conditions aux limites associées est obtenue sans et avec combustion. Les mécanismes qui contrôlent les transitions de formes de flamme sont ensuite analysés lorsque la flamme interagit avec les parois de la chambre de combustion. L’influence de la composition du mélange combustible, de la vitesse débitante et du nombre de swirl est caractérisée et il est démontré que la transition d’une flamme en V vers une flamme en M est déclenchée par un retour de flamme dans la couche limite le long d’une des parois latérales de la chambre de combustion. Les nombres sans dimension contrôlant ces transitions sont identifiés et un modèle de prévision de la forme de ces flammes est développé. La physique déterminant les transitions de forme de flammes est différente lorsque celles-ci n’interagissent pas avec les parois de la chambre de combustion. En utilisant le signal de chimiluminescence OH* et la OH-PLIF, il est montré que la teneur en hydrogène dans le combustible a une grande influence sur la forme de flamme. L’utilisation de la LIP et de thermocouples a également permis de montrer que les conditions aux limites thermiques jouent un rôle prépondérant sur la forme de flamme. Les effets combinés de l’étirement et des pertes thermiques sont examinés par l’utilisation conjointe de la PIV et de la OH-PLIF. Il est montré que les limites d’extinction de flammes pauvres prémélangées sont réduites par les pertes thermiques et que la transition d’une flamme en M vers une flamme en V est consécutive à l’extinction du front de flamme situé dans la couche de cisaillement externe du jet soumis à un étirement trop important. Ces expériences sont complétées par une analyse de la dynamique de ces flammes. Des modulations de la vitesse débitante à basse fréquence et à haute amplitude modifient la forme de flamme. La stabilisation de flammes CH4/H2/air diluées par du N2 ou du CO2 est finalement examinée. La zone de recirculation produite par la tige centrale permet d’alimenter la base de la flamme avec des gaz brûlés chauds et de stabiliser des flammes fortement diluées. Augmenter la fraction molaire de diluant dans le combustible réduit l’intensité de lumière émise par le radical OH*. Il est également montré que la composition du diluant a un impact sur le champ de température des gaz brûlés et des surfaces de la chambre de combustion. La dilution par du CO2 augmente les pertes thermiques par rayonnement des gaz brûlés. Cela réduit l’efficacité de la chambre de combustion équipée de quatre parois transparentes. [...] / This work deals with the stabilization of premixed turbulent swirling flames of methane/hydrogen/air combustible mixtures with different dilution rates of nitrogen and carbon dioxide. A central bluff body helps stabilizing the flames at low swirl numbers. The flame tip eventually impinges the combustor peripheral wall. The general objective is to gain understanding of the mechanisms governing the stabilization and the topology of these flames. It is found that the swirl number, the combustible mixture composition, the geometry of the combustor, and the thermal boundary conditions have a strong impact on the shape taken by these flames. The experimental setup used to characterize flames topologies is first described. Flames prone to topology bifurcations are selected and are studied for different arrangement of the combustor when the combustion chamber shape and size, the injection tube diameter, and swirl number are varied. One operating condition is fully characterized under non-reactive and reactive conditions using Planar Hydroxyl Laser Induced Fluorescence (OH-PLIF), Particle Imaging Velocimetry (PIV), and Laser Induced Phosphorescence of thermographic phosphors (LIP) to generate a detailed database of the flow and the corresponding boundary conditions. An analysis is then conducted to understand the mechanisms controlling shape bifurcations when the flame interacts with the combustor peripheral wall. Effects of the combustible mixture composition, the bulk flow velocity, and the swirl number are analyzed. It is shown that the transition from a V to an M flame is triggered by a flashback of the V flame tip in the boundary layer of the combustor peripheral wall. Dimensionless numbers controlling these transitions are identified and a simplified model is developed to help the prediction of the flame shapes. The physics of these shape bifurcations differs when the flame does not interact with the combustor wall. The large influence of the hydrogen enrichment in the fuel on the flame shape is analyzed using flame chemiluminescence and OH-PLIF. LIP and thermocouple measurements demonstrate that the thermal boundary conditions still have a strong impact on the flame topology. The combined effects of strain and heat losses are investigated using joint OH-PLIF and PIV experiments. It is shown that flammability limits of premixed flames are reduced due to heat losses and the transitions from M to V shaped flames is consecutive to localized extinctions of flame front elements located in the outer shear layer of the jet flow that are submitted to large strain rates. These experiments are completed by an analysis of the dynamics of methane/hydrogen/air flames. It is shown that low frequency and high amplitude velocity modulations generated by a loudspeaker alter the shape taken by these flames. The stabilization of methane/hydrogen/air flames diluted by nitrogen and carbon dioxide is finally examined. It was possible to stabilize swirled flames featuring important dilution rates due to the presence of the bluff body, installed on the axis of the injection tube. The recirculation zone behind this element supplies hot burnt gases to the flame anchoring point. Using OH* chemiluminescence imaging, it is shown than increasing the molar fraction of diluent in the fuel reduces the light emission from excited OH* radicals. The influence of dilution on the flame chemistry is emphasized with experiments conducted at a fixed thermal power and fixed adiabatic flame temperature. It is also demonstrated that the composition of the diluent has a strong influence on the temperature field of the burnt gases and of the combustor wall surfaces. Dilution with carbon dioxide increases radiative heat losses from the burnt gases in comparison to dilution with nitrogen. This penalizes the combustor efficiency equipped with four transparent quartz walls. [...]

Syngas consisting mainly of a mixture of carbon monoxide, hydrogen and other diluents, is an important fuel for power generation applications since it can be obtained from both biomass and coal gasification. Clean coal technologies require stable and efficient operation of syngas-fired gas turbines. The trapped vortex combustor (TVC) is a relatively new gas turbine combustor concept which shows tremendous potential in achieving stable combustion under wide operating conditions with low emissions. In the present work, combustion of low calorific value syngas in a TVC has been studied using in-situ laser diagnostic techniques and numerical modeling. Specifically, this work reports in-situ measurements of mixture fraction, OH radical concentration and velocity in a single cavity TVC, using state-of-the art laser diagnostic techniques such as Planar Laser-induced Fluorescence (PLIF) and Particle Image Velocimetry (PIV). Numerical simulations using the unsteady Reynolds-averaged Navier-Stokes (URANS) and Large Eddy Simulation (LES) approaches have also been carried out to complement the experimental measurements. The fuel-air momentum flux ratio (MFR), where the air momentum corresponds to that entering the cavity through a specially-incorporated flow guide vane, is used to characterize the mixing. Acetone PLIF experiments show that at high MFRs, the fuel-air mixing in the cavity is very minimal and is enhanced as the MFR reduces, due to a favourable vortex formation in the cavity, which is corroborated by PIV measurements. Reacting flow PIV measurements which differ substantially from the non-reacting cases primarily because of the gas expansion due to heat release show that the vortex is displaced from the centre of the cavity towards the guide vane. The MFR was hence identified as the controlling parameter for mixing in the cavity. Quantitative OH concentration contours showed that at higher MFRs 4.5, the fuel jet and the air jet stream are separated and a flame front is formed at the interface. As the MFR is lowered to 0.3, the fuel air mixing increases and a flame front is formed at the bottom and downstream edge of the cavity where a stratified charge is present. A flame stabilization mechanism has been proposed which accounts for the wide MFRs and premixing in the mainstream as well. LES simulations using a flamelet-based combustion model were conducted to predict mean OH radical concentration and velocity along with URANS simulations using a modified Eddy dissipation concept model. The LES predictions were observed to agree closely with experimental data, and were clearly superior to the URANS predictions as expected. Performance characteristics in the form of exhaust temperature pattern factor and pollutant emissions were also measured. The NOx emissions were found to be less than 2 ppm, CO emissions below 0.2% and HC emissions below 700 ppm across various conditions. Overall, the in-situ experimental data coupled with insight from simulations and the exhaust measurements have confirmed the advantages of using the TVC as a gas turbine combustor and provided guidelines for stable and efficient operation of the combustor with syngas fuel.