Flamelet Approach Research Articles

DQMOM approach for poly-dispersed soot formation processes in a turbulent non-premixed ethylene/air flame

To realistically treat the poly-dispersed soot formation system, the Direct Quadrature Method of Moment (DQMOM) in conjunction with the transient flamelet approach was adopted to simulate a turbulent non-premixed C2H4/air flame. The population balance equation of the soot particle distribution was approximated using the multi-environment probability density function which consists of multiple weights and abscissas in the physical space. The transient flamelet model was employed to treat the turbulence-chemistry interactions and the two-equation soot model was used to account for the soot/gas chemistry coupling allowing mass and energy exchange. In the framework of the transient flamelet model, the physical soot model terms such as nucleation, surface growth, and oxidation for the population balance equation of soot particle distribution were closed. In terms of the mean temperature, soot volume fraction, primary soot particle number density, primary soot aggregate number density, mean number of primary particle per aggregate, mean radius of soot aggregate, and mean primary soot particle diameter, the predicted profiles agreed reasonably well with the experimental data.

Computational analysis of a semi-industrial furnace fired by a flat flame burner under different O2/N2 ratios using the steady laminar flamelet approach

This paper uses computational fluid dynamics (CFD) to investigates a natural gas fired semi-industrial furnace with a thermal input of 250 kW which operates under different O2/N2 ratios in the oxidizer. The furnace is fired by a flat flame burner which is commonly used in industrial furnaces. The simulations were confronted with temperature measurements inside the furnace and with measurements of the surface temperature of the quarl. The main focus was on using models which are not computationally demanding. The steady laminar flamelet model (SFM) with a detailed mechanism was thus used to model the combustion. With the SFM the calculation time can be dramatically reduced compared to simulations with the eddy dissipation model (EDM) although using a detailed mechanism. The skeletal25 mechanism, consisting of 17 species and 25 reactions, was used in this investigation. Additionally the furnace was simulated with the two detailed mechanism GRI 3.0 and smooke46. The predicated temperature inside the furnace of the SFM and the skeletal25 were in good accordance with the measurements for all oxygen concentrations in the oxidizer. The predicted surface temperature of the quarl showed higher deviation from the measurements but also showed a reasonable standard of accuracy. Furthermore the investigation demonstrated that the two detailed mechanisms GRI 3.0 and smooke46 are also applicable for flat flame burners and oxygen concentrations up to 37 Vol% oxygen in the oxidizer, a finding which is in contrast to previous investigations with jet flames. For oxygen concentrations higher than 37 Vol% in the oxidizer the GRI 3.0 and the smooke46 mechanisms fails to predict the temperature field in the furnace. Only the skeletal25 mechanism was able to predict the temperature field correct for higher oxygen concentrations in the oxidizer.

Numerical modeling of soot formation in a turbulent C2H4/air diffusion flame

Soot formation in a lifted C 2 H 4 -Air turbulent diffusion flame is studied using two different paths for soot nucleation and oxidation; by a 2D axisymmetric RANS simulation using ANSYS FLUENT 15.0. The turbulence-chemistry interactions are modeled using two different approaches: steady laminar flamelet approach and flamelet-generated manifold. Chemical mechanism is represented by POLIMI to study the effect of species concentration on soot formation. P1 approximation is employed to approximate the radiative transfer equation into truncated series expansion in spherical harmonics while the weighted sum of gray gases is invoked to model the absorption coefficient while the soot model accounts for nucleation, coagulation, surface growth, and oxidation. The first route for nucleation considers acetylene concentration as a linear function of soot nucleation rate, whereas the second route considers two and three ring aromatic species as function of nucleation rate. Equilibrium-based and instantaneous approach has been used to estimate the OH concentration for soot oxidation. Lee and Fenimore-Jones soot oxidation models are studied to shed light on the effect of OH on soot oxidation. Moreover, the soot-radiation interactions are also included in terms of absorption coefficient of soot. Furthermore, the soot-turbulence interactions have been invoked using a temperature/mixture fraction-based single variable PDF. Both the turbulence-chemistry interaction models are able to accurately predict the flame liftoff height, and for accurate prediction of flame length, radiative heat loss should be accounted in an accurate way. The soot-turbulence interactions are found sensitive to the PDF used in present study.

Effect of gas—phase carbon depletion by sooting on the structure of methane/air flamelets

The paper describes an approach to model soot formation/oxidation in non premixed turbulent flames, which in particular accounts for the effect of gas-phase carbon depletion due to sooting. The effect is relevant to combustion chambers fed with oxygen (rather than air), operating at high pressure and overall rich, such as rocket chambers. A scaled gas-phase elemental carbon mass fraction is introduced to this end and, in the framework of a laminar flamelet approach, a library is developed for use in turbulent combustion models. Due to the lack of reference data for rocket chambers conditions, the library is limited for the time being to nonpremixed methane/air flames at two values of pressure, 1 atm and 3 atm, for which experimental data are available. Results indicate a signicant effect of carbon depletion on the concentration of soot precursor acetylene in particular, and on the ensuing soot nucleation rate. The model is shown to correctly capture the decrease of the latter rate with gas-phase carbon depletion, thereby potentially enabling to extend the range of applicability of semi-empirical soot prediction models for nonpremixed turbulent combustion.

A Large-Eddy-Simulation Study of Combustion Dynamics of Bluff-Body Stabilized Flames

ABSTRACTA comprehensive numerical study is conducted to explore the dynamic behaviors of a flame stabilized by a triangular bluff body in a straight chamber. The formulation accommodates the complete set of conservation equations with turbulence closure achieved by a large eddy simulation (LES) technique. A G-equation-based level-set flamelet approach is employed to model the interactions between premixed combustion and turbulence. Both non-reacting and reacting flows are treated, with special attention given to the effect of inlet boundary conditions on the flame evolution. The flow around the bluff body consists of boundary layers, separated shear layers, a recirculation zone and a wake. Their mutual coupling, as well as interactions with acoustic motion and flame oscillation are analyzed in detail. The physical processes responsible for driving combustion instabilities and the mechanism of energy transfer from chemical reactions in the flame zone to acoustic oscillations in the bulk of the chamber are investigated systematically. Intensive resonance is found to occur between shear-layer instabilities and chamber acoustic waves, when the acoustically reflecting inlet boundary condition is enforced. The resulting complex interplay among acoustic motion, vortex shedding, and unsteady heat release forms a feedback loop and excites combustion instabilities with large flow oscillations.

Nonlinear hydrodynamic and thermoacoustic oscillations of a bluff-body stabilised turbulent premixed flame

Turbulent premixed flames often experience thermoacoustic instabilities when the combustion heat release rate is in phase with acoustic pressure fluctuations. Linear methods often assume a priori that oscillations are periodic and occur at a dominant frequency with a fixed amplitude. Such assumptions are not made when using nonlinear analysis. When an oscillation is fully saturated, nonlinear analysis can serve as a useful avenue to reveal flame behaviour far more elaborate than period-one limit cycles, including quasi-periodicity and chaos in hydrodynamically or thermoacoustically self-excited system. In this paper, the behaviour of a bluff-body stabilised turbulent premixed propane/air flame in a model jet-engine afterburner configuration is investigated using computational fluid dynamics. For the frequencies of interest in this investigation, an unsteady Reynolds-averaged Navier–Stokes approach is found to be appropriate. Combustion is represented using a modified laminar flamelet approach with an algebraic closure for the flame surface density. The results are validated by comparison with existing experimental data and with large eddy simulation, and the observed self-excited oscillations in pressure and heat release are studied using methods derived from dynamical systems theory. A systematic analysis is carried out by increasing the equivalence ratio of the reactant stream supplied to the premixed flame. A strong variation in the global flame structure is observed. The flame exhibits a self-excited hydrodynamic oscillation at low equivalence ratios, becomes steady as the equivalence ratio is increased to intermediate values, and again exhibits a self-excited thermoacoustic oscillation at higher equivalence ratios. Rich nonlinear behaviour is observed and the investigation demonstrates that turbulent premixed flames can exhibit complex dynamical behaviour including quasiperiodicity, limit cycles and period-two limit cycles due to the interactions of various physical mechanisms. This has implications in selecting the operating conditions for such flames and for devising proper control strategies for the avoidance of thermoacoustic instability.

Di-n-buthylether, n-octanol, and n-octane as fuel candidates for diesel engine combustion

In this study, three different C8 fuels, namely n-octanol, di-n-buthylether (DnBE), and n-octane, are investigated with regard to diesel engine combustion to assess and analyze the effects of fuel structure. DnBE and n-octanol are isomers, i.e. they have the same elementary composition (C8H18O), but a different structure and very different chemical and physical properties. The ignition behavior of these fuels in engine-like configurations is studied in terms of chemical modeling using recently published detailed kinetic mechanisms. The reduced and enhanced homogeneous ignition propensity of the alcohol and ether functional groups, respectively, are explained by reaction pathway analysis. However, the difference in low temperature reactivity of n-octanol and n-octane is relatively small compared to the difference in their cetane ratings. To study the engine behavior of these fuels, experiments and simulations were performed. A single cylinder diesel engine was operated with DnBE, n-octanol, and n-octane as single component fuels. For all three fuels, very low soot emissions at nitrogen oxide emissions within the Euro 6 regulation limits can be reached. Combustion and pollutant formation in the diesel engine are computed using the representative interactive flamelet approach. Results from the numerical simulations show good agreement with the experimental diesel engine tests. A subsequent analysis of the diesel engine simulation results shows that the differences in engine operation and carbon monoxide emissions can be attributed to the different ignitability, reflected by the different cetane ratings of the fuels. The substantially lower cetane rating of n-octanol compared to n-octane is explained by analysis of engine simulations and homogeneous reactor calculations. The effect of the different physical fuel properties does not play a significant role in the operation range studied. However, it is found that one of the main reasons for the large differences in cetane numbers between n-octane and n-octanol is the different stoichiometric mixture fraction, which leads in diesel engines to lower temperatures at the ignition location and hence to longer ignition delay times.

Application of the steady flamelet model on a lab-scale and an industrial furnace for different oxygen concentrations

In the present study a numerical and experimental investigation was done on the impact of oxy-fuel combustion in a lab-scale furnace. For combustion and radiation modelling the steady flamelet approach with 17 species and 25 reactions associated with a WSGG (weighted sum of grey-gases) model was used. CFD (computational fluid dynamics) model was validated by measured temperatures and heat fluxes with different O2 concentrations. It was found that simulated temperatures and heat fluxes were in close agreement with the measurements in the full range of oxygen enrichment. Although 17 species were considered the calculation time was significantly reduced by the steady flamelet approach compared to commonly used eddy dissipation concept models. Predicted and measured data revealed gas savings of 8.2% by an O2 concentration of 25 vol% instead of 21 vol%. Maximum gas savings were determined for 100 vol% O2 with a value of 16.7%. The CFD model was also applied to a simulation of an 18.2 MW walking hearth furnace under air-fired conditions which should be adapted for oxy-fuel combustion in the future. Results from CFD showed a heat flux of 9.15 MW compared to the required 9.33 MW according to the material data and production rate.

An evaluation of the assumptions of the flamelet model for diesel combustion modeling

Flamelet-based models are widely used to model turbulence-chemistry interaction in Reynolds-Averaged Navier–Stokes (RANS) simulations and Large Eddy Simulations (LES). In this study, one-dimensional laminar and two-dimensional Direct Numerical Simulations (DNS) of reacting mixing layers are used to assess the validity of flamelet models in turbulent diesel jets. The pressure and initial temperature are chosen to be similar to those found in diesel engine combustion chambers at the end of compression. The validity of the flamelet model is first evaluated by comparing the flame development predicted by DNS with that predicted by solving the unsteady flamelet equations. It is shown that there are significant differences in the temperature profiles during the flame development following autoignition. This difference in the unsteady flame development can be a source of error in predicting ignition and flame development. The difference is attributed to the fact that in flamelet models, the dependence of scalar dissipation rate, χ, on the mixture fraction, Z, is assumed to have a constant functional relationship, usually an error function profile, which remains unchanged during the flame development process. The DNS results show that the chemical reactions cause significant increase in the local scalar dissipation rate near the flame. This increase leads to higher diffusion rates for the active radicals near the flame and thus faster flame development. It was shown that solving the unsteady flamelet equations using the scalar dissipation rate profiles obtained from one-dimensional direct simulations lead to less than 5% error in the temperature profiles during the flame development. Since this approach is not computationally feasible for practical applications, an ad hoc modification of the error function profile employed in generating flamelet libraries is proposed for the scalar dissipation rate to account for the chemical reactions and the results show an improved performance compared to the traditional flamelet approach.

Design Improvement Survey for NOx Emissions Reduction of a Heavy-Duty Gas Turbine Partially Premixed Fuel Nozzle Operating With Natural Gas: Numerical Assessment

A numerical investigation of a low NOx partially premixed fuel nozzle for heavy-duty gas turbine applications is presented in this paper. Availability of results from a recent test campaign on the same fuel nozzle architecture allowed the exhaustive comparison study presented in this work. At first, an assessment of the turbulent combustion model was carried out, with a critical investigation of the expected turbulent combustion regimes in the system and taking into account the partially premixed nature of the flame due to the presence of diffusion type pilot flames. In particular, the fluent partially premixed combustion model and a flamelet approach are used to simulate the flame. The laminar flamelet database is generated using the flamelet generated manifold (FGM) chemistry reduction technique. Species and temperature are parameterized by mixture fraction and progress variable. Comparisons with calculations with partially premixed model and the steady diffusion flamelet (SDF) database are made for the baseline configuration in order to discuss possible gains associated with the introduced dimension in the FGM database (reaction progress), which makes it possible to account for nonequilibrium effects. Numerical characterization of the baseline nozzle has been carried out in terms of NOx. Computed values for both the baseline and some alternative premixer designs have been then compared with experimental measurements on the reactive test rig at different operating conditions and different split ratios between main and pilot fuel. Numerical results allowed pointing out the fundamental NOx formation processes, both in terms of spatial distribution within the flame and in terms of different formation mechanisms. The obtained knowledge would allow further improvement of fuel nozzle design.

CFD and experimental analysis of a 115 kW natural gas fired lab-scale furnace under oxy-fuel and air–fuel conditions

This paper investigates a natural gas fired lab-scale furnace with a thermal input between 28 and 115kW under different O2/N2 ratios in the oxidizer by computational fluid dynamics (CFD). Results of the simulation were confronted with temperature measurements inside the furnace and heat flux measurements on a water cooled plate inside the furnace. The main goal of this work was to use a detailed chemical mechanism and reduce the calculation time. This was achieved with the steady flamelet (SFM) approach. The advantage of the SFM approach is that the computational chemical calculation can be pre-processed and stored in look up tables. Only two additional equations have to be solved to determine the chemical reaction in the flow field. For the simulation the detailed mechanism skeletal25 was used with 17 species and 25 reactions. Additionally the furnace was simulated with the eddy dissipation concept model (EDC) which other authors mainly use to describe oxy-fuel combustion. For the EDC simulation a refined version of the 4-step mechanism proposed by Jones and Lindstedt was used. The EDC simulation was used as a benchmark to determine the time saving potential of the SFM approach. With the SFM approach the calculation time could be reduced from 4weeks to 4days on 8 CPU cores, although a detailed mechanism was being used. The predicted temperatures of the CFD simulations were in good accordance with the measurements and showed the applicability of the skeletal25 mechanism with the SFM approach under different combustion environments. In metal melting or reheating furnace the right prediction of the heat flux on the goods is crucial. Therefore the heat flux on a water cooled plate inside the furnace was determined by measurements and CFD calculations for different combustion environments. For the heat flux at a temperature level of 1070°C the CFD calculation showed a maximum relative error of 5% to the measurements for 21, 25, 30, 45 and 100Vol% O2 in the oxidizer. For the temperature level of 1200°C the maximum error increases, especially for O2 concentration in the oxidizer higher than 45% up to 12%. Both the experiments and the numerical model showed an increase in furnace efficiency with increasing oxygen in the oxidizer. A maximum efficiency of 76% was observed for 100Vol% in the oxidizer compared to 48% at 21Vol% O2. This shows the fuel saving potential of oxygen or oxygen enriched combustion.

The usability and limits of the steady flamelet approach in oxy-fuel combustions

This paper investigates two furnaces which work under oxy-fuel condition with natural gas. One is a 0.8 MW furnace where detailed inflame measurements are available. The other furnace is an 11.5 kW lab-scale furnace with temperature measurements. The furnaces were investigated by CFD (Computational fluid dynamics) analysis. The main focus was on using combustion models that are not computationally demanding. Therefore the SFM (steady flamelet) approach was used with two detailed mechanisms. The advantage of the SFM is that the calculation time can be reduced from 4 weeks to 4 days on 8 CPU-cores. The applicability of two detailed mechanisms under oxy-fuel condition is pointed out in this paper. The investigation showed that the skeletal25 mechanism and the SFM are in very good accordance with measurements. If the strain rate between CH4 and O2 stream is too low, the SFM fails to predict the flame shape correctly. The influence of three different turbulence models was also investigated. Furthermore simulations with the eddy dissipation model and numerically expensive eddy dissipation concept model were conducted. Different WSGGM (weighted sum of grey gases model) were applied. The comparison of the WSGGMs showed that the difference between them is insignificant for small furnaces.

Validation of turbulent flame speed models for methane–air-mixtures at high pressure gas engine conditions

To describe the premixed combustion of natural gas in internal combustion engines, the flamelet approach is often assumed to be appropriate. It postulates a thin flame front which is wrinkled by turbulence but locally spreads like a laminar flame. Numerous correlations for the macroscopic turbulent flame speed to the local laminar flame speed exist. In this study seven correlations are validated at engine conditions, i.e., at high pressure (up to 7.0MPa) and high turbulence (turbulent Reynolds number up to 4.4·104), with the help of measurements from a single cylinder research gas engine. The stoichiometry, the exhaust gas recirculation rate, and the engine speed are varied. Simulations of the detailed reaction kinetics with the diffusive species and energy transport are performed to calculate the laminar flame speed. The flame propagation is described by a zonal cylinder model on the basis of the measured in-cylinder pressure traces, to determine the turbulent flame speed with respect to the thermal expansion of the reacting gas. Additionally, Computational Fluid Dynamics (CFD) simulations of the in-cylinder charge motion are performed to describe the turbulent flow field. It is found that four flame speed correlations including a pressure-dependent term predict flame speed ratios in quantitative accordance to the measurements. This is noteworthy, as these correlations are mostly developed for lower turbulence and at considerable lower pressure. It supports the hypothesis that flamelet-like combustion is still found above the Klimov–Williams criterion.

Effects of fuel injection parameters on the performance of homogeneous charge compression ignition at low-load conditions

With the objective of enhancing the effectiveness of late fuel injection strategy in extending the low-load limit of homogeneous charge compression ignition engines, a numerical study is conducted to investigate the effects of fuel injection parameters, such as the injection pressure and spray cone angle, on the overall combustion efficiency and CO/NOx emissions. Closed-cycle engine simulations are performed incorporating detailed iso-octane reaction kinetics and combustion submodel based on the spray-interactive flamelet approach. Extensive parametric studies are conducted to provide a detailed map of the combustion efficiency and emission performance. In general, it is found that the in-cylinder charge stratification can be reduced by both an increased injection pressure and a wider spray cone angle, resulting in substantially lower NOx emissions and reasonably high combustion efficiency simultaneously. The present study demonstrates that an optimal adjustment of the two fuel injection parameters can result in significant extension of the low-load limit of homogeneous charge compression ignition through delayed fuel injection strategy.

Assessment of flamelet versus multi-zone combustion modeling approaches for stratified-charge compression ignition engines

The spray-interactive flamelet and extended multi-zone combustion models coupled with multi-dimensional computational fluid dynamics are applied to investigate the effects of charge stratification in a direct-injection compression ignition engine under low load conditions. A parametric study was carried out in order to compare the two approaches for early and late fuel injection timings. Comparison of numerical results with available experimental data shows that for early fuel injection, both models predict the auto-ignition and combustion characteristics with comparable fidelity. As the fuel injection timing is delayed, however, the spray-interactive flamelet model is found to capture the onset of combustion and subsequent heat release with greater accuracy. Further investigation reveals that the better performance of the spray-interactive flamelet model over a wider range of mixture-stratified conditions is mainly attributed to its ability to capture the diffusive transport resulting from small-scale mixing and turbulence–chemistry interaction, which becomes more important when significant mixture inhomogeneities exist in the engine cylinder.

ICOPE-15-1124 Numerical Investigation of Turbulent Combustion Flow in Industrial Combustor with Flamelet Approach

ICOPE-15-1124 Numerical Investigation of Turbulent Combustion Flow in Industrial Combustor with Flamelet Approach

Analysis of a filtered flamelet approach for coarse DNS of premixed turbulent combustion

Nowadays numerical simulations of premixed turbulent combustion can be performed at high spatial resolutions due to the continuously increasing computational power. At a resolution of the order of the laminar flame thickness there is negligible turbulence in the subgrid level and a proper reconstruction of the filtered flame is adequate for accurate predictions. In this scenario, which can be termed as a coarse scale Direct Numerical Simulation (DNS), reconstruction of the filtered flame using a spatially filtered flamelet (1-D laminar flame) is analysed. First, DNS of a turbulent premixed slot burner is computed to generate a reference database. This database is filtered at different length scales of the order of laminar flame thickness for an a priori assessment of turbulent flame reconstruction using a filtered flamelet. The filtered DNS source term, molecular diffusion and subgrid convection of the reaction progress variable is compared with a flamelet convoluted with top-hat profiles of the same order. The source term and molecular diffusion are approximated well from the filtered flamelet while the unresolved convection shows deviation. Finally, the reconstruction of the turbulent flame is tested a posteriori on the same filter widths (mesh size) and the results are compared. It is found that a flamelet filtered spatially at the order of the computational mesh and tabulated using a single controlling variable i.e. the reaction progress variable is suitable for a coarse scale DNS of premixed turbulent combustion.

Large eddy simulations of the HIFiRE scramjet using a compressible flamelet/progress variable approach

In this study, large eddy simulations (LES) of supersonic combustion using a compressible flamelet/progress variable (CFPV) approach are performed for the HIFiRE scramjet at Mach 8 flight conditions. The LES results show good agreement with the ground test experimental measurements. The combustion model is based on an efficient flamelet approach, where compressibility corrections are devised based on assumed functional forms of important thermo-chemical quantities. Specifically, the source term of the progress variable is rescaled with the local density and temperature in the LES, leading to improved predictions relative to existing flamelet models. A modified equilibrium wall-model, capable of predicting the viscous heating, is used in the viscous near-wall region. Temperature near the wall increases significantly due to viscous heating, enhancing the reaction rate and heat-release. This is shown to be a crucial step for accurately predicting the pressure rise in the combustor.

Numerical investigation of the steady flamelet approach under different combustion environments

In the present work a CFD study of a natural gas fired lab-scale furnace under different oxygen enrichments was done. Results were compared to measured temperatures and heat fluxes on a thermal sink inside the furnace. The main emphasis was to apply the steady flamelet model (SFM) with a detailed chemical mechanism to predict the flow field, temperature and species concentrations in high temperature applications. A skeletal mechanism, which considered 25 reversible reactions and 17 species, showed close agreement with the measurement for all oxygen concentrations in the oxidizer. Turbulence modelling was done by the standard and realizable k-epsilon models as well as the Reynolds stress model (RSM). It was found, that standard k-epsilon model calculates too high temperatures in the vicinity of the burner. Results from realizable k-epsilon model and RSM were in close accordance with marginal differences in flame length and maximum temperatures. The CFD calculation with the SFM was also compared with a time expensive eddy dissipation concept (EDC) simulation with 46 reactions and 17 species. Both approaches calculated similar results for temperature and species concentrations. The calculation time was reduced significantly from 4weeks (EDC) to 6days with the SFM although dissociation effects and forming of radicals were taken into account. Considering melting and annealing furnaces, the heat flux to a thermal sink constitutes a major role for combustion processes. Heat flux to the thermal sink was determined by measurement and CFD predictions for different O2/N2 ratios in the oxidizer. CFD calculations revealed a maximum relative error to the measurement for the heat flux of 5% for 25, 30, 45 and 100Vol% O2 in the oxidizer. The numerical model and experiments highlighted a major increase on the furnace efficiency due to oxygen enrichment. A maximum efficiency of 67% was detected for natural-gas combustion with pure oxygen compared to 44% in case of 25Vol% O2. It was also found, that high oxygen concentrations lead to a homogeneous temperature distribution on the sink which is desired for melting and annealing applications.

Modeling partially premixed combustion behavior in multiphase LES

A partially premixed flamelet model is extended to account for liquid fuel, and its accuracy and dependence on spray modeling inputs are investigated. The spray and combustion model coupling is considered by simulating single drop evaporation experiments. These simulations confirmed previous findings showing that small changes in spray model assumptions significantly influence evaporation rates. The analysis is then extended to Large Eddy Simulation (LES) using a NASA model aircraft combustor burning Jet-A fuel. Results indicate the partially premixed flamelet approach can describe the range of combustion physics found in the burner. However, they also reveal that the liquid model sensitivities hold in LES, where a tight coupling exists between combustion model predictions and spray model assumptions. Details of the liquid modeling approach, including thermodynamic specifications and descriptions of liquid spray at the nozzle outlet, influence the burning regime, mean gas temperatures, and emissions levels predicted by LES. The results suggest that while the combustion model is capable, spray model influences must be firmly understood before validation can be accomplished in liquid fueled contexts.