Bluff-body Flame Research Articles

A numerical study on the influence of airstream dilution and jet velocity on NO emission characteristics of CH4 and DME bluff-body flames

In this paper, a bluff-body flame structure has been modeled using conditional moment closure model (CMC) to study the effect of airstream dilution with CO2 and H2O on nitric oxide (NO) production. This scenario would mimic the effect of exhaust gas recirculation (EGR) in an internal combustion (IC) engine or in a gas turbine. A 2D in-house code, employing a k–ε turbulence model with modified constant Cε1, has been used to calculate the flow and mixing field. Methane (CH4) and di-methyl-ether (DME) have been separately used as fuels to assess the performance. Fuel jet velocities are varied to investigate the effectiveness of these dilutions at different levels of turbulence–chemistry interactions. The presence of both CO2 and H2O in the airstream reduced the NO quantity for both the fuels. The effectiveness of the H2O diluent on mass basis is more prominent in reducing NO. With the increased fuel velocity, a situation similar to increased injection pressure in IC engines, higher amounts of diluents caused near extinction of the flame. For the same amount of diluents, global NO reduction in DME is higher compared to that for methane.

Large-Eddy Simulation of Bluff-Body Flame Using the Equilibrium Combustion Model

Flame stabilization is an important issue in practical applications of combustion systems. The bluff-body configuration is a common technique that stabilizes the flame by producing a strong recirculation zone downstream of the bluff body. Gas turbines provide a typical application of the bluff-body configuration. In this paper, a computational study of a bluff-body flame has been undertaken using an unstructured large-eddy simulation. The filtered Navier–Stokes equations are closed using a standard Smagorinsky model, and an equilibrium combustion model is employed for the chemistry calculation. All filtered scalar quantities are evaluated using a presumed probability density function based on a beta distribution function. It was found that accurate prediction of velocity profiles are strongly dependent upon the inflow conditions. It was also found that the equilibrium model for chemistry calculation does not capture well the dynamics of the reaction in the recirculation zone, where the diffusion timescales are very small. Based on this observation, a criterion was established for the implementation of the equilibrium model in terms of diffusion and chemical timescales. The diffusion timescales are inversely proportional to the scalar dissipation rate. It was found that the ratio of the diffusion timescale to the chemical timescale must be at least to obtain accurate results with the equilibrium model.

A new robust consistent hybrid finite-volume/particle method for solving the PDF model equations of turbulent reactive flows

A new robust hybrid finite-volume (FV)/particle method is developed for solving joint probability density function (JPDF) model equations of statistically stationary turbulent reacting flows. The method is designed to remedy the deficiencies of the hybrid algorithm developed by Muradoglu et al. (1999, 2001). The density-based FV solver in the original hybrid algorithm has been found to be excessively dissipative and yet not very robust. To remedy these deficiencies, a pressure-based PISO algorithm in the open source FV package, OpenFOAM, is used to solve the Favre-averaged mean mass and momentum equations while a particle-based Monte Carlo algorithm is employed to solve the fluctuating velocity-turbulence frequency-compositions JPDF transport equation. The mean density is computed as a particle field and passed to the FV method. Thus the redundancy of the density fields in the original hybrid method is removed making the new hybrid algorithm more consistent at the numerical solution level. The new hybrid algorithm is first applied to simulate non-swirling cold and reacting bluff-body flows. The convergence of the method is demonstrated. In contrast with the original hybrid method, the new hybrid algorithm is very robust with respect to grid refinement and achieves grid convergence without any unphysical vortex shedding in the cold bluff-body flow case. In addition, the results are found to be in good agreement with the earlier PDF calculations and also with the available experimental data. Finally the new hybrid algorithm is successfully applied to simulate the more complicated Sydney swirling bluff-body flame ‘SM1’. The method is also very robust for this difficult test case and the results are in good agreement with the available experimental data. In all the cases, the PISO-FV solver is found to be highly resilient to the noise in the mean density field extracted from the particles.

Large eddy simulation/probability density function simulations of bluff body stabilized flames

This work presents large eddy simulation/probability density function (LES/PDF) simulation results for the Sandia/Sydney series of bluff-body stabilized CH4/H2 flames. Results are presented for the flames HM1, HM2 and HM3, using the 19-species ARM2 reduced chemical mechanism, and comparison is made with previous numerical simulations of the same flames. When compared to previous numerical studies of these bluff-body flames, the present simulation shows considerable improvement, particularly in the downstream regions of the flow. The simulations are shown to be sensitive to the treatment of heat transfer to the bluff-body face, with better agreement in the temperature profiles achieved with the addition of a Dirichlet temperature boundary condition.

Validation and implementation of algebraic LES modelling of scalar dissipation rate for reaction rate closure in turbulent premixed combustion

The closure of the filtered reaction rate of the reaction progress variable using an algebraic model for Favre-filtered Scalar Dissipation Rate (SDR) N∼c in turbulent premixed combustion has been assessed in the context of Large Eddy Simulations (LES). This assessment consists of a priori Direct Numerical Simulation (DNS) analysis based on freely propagating statistically planar turbulent premixed flames and a posteriori analysis, involving the LES simulations of a well-documented rectangular dump combustor configuration with sudden expansion (i.e. ORACLES burner) and a premixed flame stabilised on a triangular bluff body flame holder (i.e. Volvo Rig). It has been found that the newly developed SDR model satisfactorily captures N∼c obtained from explicitly filtered DNS data. The predictions of this SDR based LES closure in the ORACLES burner and Volvo Rig configurations exhibit good agreement with experimental results without requiring any major modification to the model parameters. The predictions of the SDR model for the LES of the ORACLES burner and Volvo Rig have been compared to those of two algebraic Flame Surface Density (FSD) models, which yielded satisfactory agreement with experimental data in a previous analysis. The performance of the SDR based closure remains either comparable to or better than the FSD based closures for the two test configurations considered in this analysis.

The probabilistic nature of ignition of turbulent highly-strained lean premixed methane-air flames for low-emission engines

The probabilistic nature of ignition of turbulent highly-strained lean premixed flames has been investigated. Two flow configurations have been considered in this study; counter-flow and bluff-body flames. Different successful and non-successful ignition events in both flows have been observed directly with high-speed imaging. In addition, the flame front structure during the flame propagation following the ignition has been observed using OH-PLIF technique. Moreover, the ignition probability has been measured in both flows with different equivalence ratios and flow velocities. It has been found that high bulk velocities decrease the ignition probability in all locations and for all flames. For counter-flow flames, ignition is sometimes possible even in locations where there is negligible probability of finding flammable mixture and is sometimes impossible in locations with high probability of flammable flow. The edge flame propagation speed has also been detected in this type of flames. For bluff-body flames, the flame propagation behavior following the spark ignition depends mainly on the location of the spark in respect to the recirculation zones. Furthermore, the flame inside the side recirculation zone (SRZ) quenches soon after the whole flame lights-up. Failed ignition has been viewed close to the extinction flow conditions of the flame. Igniting the flame away from the extinction conditions results in 100% ignition probability regardless of the ignition location. However, close to extinction, ignition probability decreases gradually and achieving ignition is not possible at all outside the central recirculation zone (CRZ). The obtained ignition probability contours of both flows have been compared with the previously-studied ignition probability contours of turbulent non-premixed flames of the same burners.

Implicit and explicit schemes for mass consistency preservation in hybrid particle/finite-volume algorithms for turbulent reactive flows

This work addresses the issue of particle mass consistency in Large Eddy Simulation/Probability Density Function (LES/PDF) methods for turbulent reactive flows. Numerical schemes for the implicit and explicit enforcement of particle mass consistency (PMC) are introduced, and their performance is examined in a representative LES/PDF application, namely the Sandia–Sydney Bluff-Body flame HM1. A new combination of interpolation schemes for velocity and scalar fields is found to better satisfy PMC than multilinear and fourth-order Lagrangian interpolation. A second-order accurate time-stepping scheme for stochastic differential equations (SDE) is found to improve PMC relative to Euler time stepping, which is the first time that a second-order scheme is found to be beneficial, when compared to a first-order scheme, in an LES/PDF application. An explicit corrective velocity scheme for PMC enforcement is introduced, and its parameters optimized to enforce a specified PMC criterion with minimal corrective velocity magnitudes.

Velocity and Flame Wrinkling Characteristics of a Transversely Forced, Bluff-Body Stabilized Flame, Part II: Flame Response Modeling and Comparison with Measurements

This article analyzes the response of bluff-body stabilized flames to transverse acoustic waves. Data were obtained for bluff-body flames at flow velocities of 50 m/s and 100 m/s with inlet air temperatures ranging from 475–750 K. Two different modes of acoustic excitation were applied, corresponding to velocity and pressure nodes/antinodes along the combustor centerline. High-speed imaging and phase-locked particle image velocimetry (PIV) were used to characterize the spatio-temporal flame front and velocity field response. The key objective of the study is to compare measurements of the fluctuating velocity and flame wrinkling using the G-equation, e.g., to compare how the ensemble averaged unsteady flame wrinkling gain/phase predicted by solving the G-equation using the measured velocity field as inputs compares to the measured values. These results show good qualitative agreement between the comparisons and measurements, and quite good quantitative accuracy in many of the cases. These comparisons also enable insight into the features controlling the unsteady flame wrinkling; for example, it enables insight into the relative contributions of acoustic and vortical disturbances on the flame wrinkling characteristics, whose different propagation velocities lead to interference patterns and oscillatory flame wrinkle amplitude characteristics.

Modal dynamics of self-excited azimuthal instabilities in an annular combustion chamber

In this paper we describe the time-varying amplitude and its relation to the global heat release rate of self-excited azimuthal instabilities in a simple annular combustor operating under atmospheric conditions. The combustor was modular in construction consisting of either 12, 15 or 18 equally spaced premixed bluff-body flames around a fixed circumference, enabling the effect of large-scale interactions between adjacent flames to be investigated. High-speed OH∗ chemiluminescence imaged from above the annulus and pressure measurements obtained at multiple locations around the annulus revealed that the limit cycles of the modes are degenerate in so much as they undergo continuous transitions between standing and spinning modes in both clockwise (CW) and anti-clockwise (ACW) directions but with the same resonant frequency. Similar behaviour has been observed in LES simulations which suggests that degenerate modes may be a characteristic feature of self-excited azimuthal instabilities in annular combustion chambers. By modelling the instabilities as two acoustic waves of time-varying amplitude travelling in opposite directions we demonstrate that there is a statistical prevalence for either standing m=1 or spinning m=±1 modes depending on flame spacing, equivalence ratio, and swirl configuration. Phase-averaged OH∗ chemiluminescence revealed a possible mechanism that drives the direction of the spinning modes under limit-cycle conditions for configurations with uniform swirl. By dividing the annulus into inner and outer annular regions it was found that the spin direction coincided with changes in the spatial distribution of the peak heat release rate relative to the direction of the bulk swirl induced along the annular walls. For standing wave modes it is shown that the globally integrated fluctuations in heat release rate vary in magnitude along the acoustic mode shape with negligible contributions at the pressure nodes and maximum contributions at the pressure anti-nodes.

Analysis of entropy generation in a hydrogen-enriched turbulent non-premixed flame

The analysis of local entropy generation and exergy loss was performed in a turbulent non-premixed H2-enriched CH4–air bluff-body flame. Detailed chemical kinetic, transport properties, and turbulence-chemistry interaction were taken into account in using laminar flamelet model for the simulation of combustion process via an in-house, finite volume code. The analysis was based on local entropy generation calculation. Results showed that thermal conduction made the most contribution to entropy generation followed by chemical reaction and mass diffusion, while the contribution of viscous dissipation was negligible. Entropy generation resulting from thermal conduction occurs in a large volume of the domain, while entropy generation resulting from chemical reaction and mass diffusion occurs only near the bluff surface. The effect of H2 addition to fuel and air preheating on the entropy generation rate was investigated. It was observed that entropy generation and exergy loss were decreased by H2 addition, mainly due to a decrease in the chemical reaction component of entropy generation, while entropy generation resulting from thermal conduction slightly increased and entropy generation resulting from mass diffusion remained almost constant. Entropy generation resulting from heat conduction by preheating combustion air decreased, while entropy generation resulting from chemical reaction and mass diffusion remained almost constant. The decrease of thermal conduction contribution in entropy generation is so significant that, by preheating air up to 750 K in the case of pure CH4, chemical reaction becomes the main source of irreversibility. These investigations show that H2 addition and preheating the combustion air both lead to the improvement of the second law efficiency, although the second law efficiency is more sensitive to flame structure and air temperature.

Effects of preferential transport and strain in bluff body stabilized lean and rich premixed CH4/air flames

The effects of preferential transport and strain on the scalar structure of turbulent premixed bluff body stabilized flames are examined using Raman–Rayleigh–LIF diagnostics. Bulk flowrate and equivalence ratio are varied parametrically. Comparisons with laminar flame calculations are used both to validate the quality of the experimental measurements and to facilitate interpretation of the measured response of the bluff body flames to changes in equivalence ratio and flow conditions. Strong effects of preferential species transport on the internal flame structure and the product composition of the recirculation zone are observed in lean, stoichiometric, and rich flames. Contrary to the standard view of differential diffusion effects in turbulent flow becoming negligible at sufficiently high Reynolds number, the preferential diffusion effects in the premixed bluff body flames reported here initially increase with the Reynolds number then saturate and persist at higher Reynolds numbers. Measurements in a rich bluff body flame are suggestive of high strain, but instantaneous profiles in the turbulent flame for this shear-flow geometry are thicker than calculated for an unstrained laminar flame.

Analysis of blowoff dynamics from flames with stratified fueling

In some compact combustors with bluff body flame stabilization, fuel injection may be too closely coupled to permit uniform mixing. This stratification in the fuel profile can be asymmetric about the bluff body, and the flame equivalence ratio may differ across the recirculation zone. An experimental study of asymmetric fueling about a bluff body is reported in this paper with a focus on the impact of stratification on flame blowoff. In order to understand the blowoff dynamics of turbulent flames with stratified fueling, high speed chemiluminescence imaging was performed for five levels of fuel stratification through blowoff. Physical probe measurements of the local equivalence ratios were used to characterize the stratification. It was found that for overall fuel lean flames (averaged across the bluff body), fuel stratification increases the flame stability such that the overall equivalence ratio at blowoff is decreased for increased stratification. It was also found that the stronger (richer) shear layer determines the flame dynamics near blowoff. The leaner branch of the flame extinguishes earlier and the richer branch is shown to pilot the overall flame and therefore be responsible for the increase in flame stability at larger gradients. Proper orthogonal decomposition (POD) was applied to the high speed chemiluminescence images of the flames and used to quantitatively track the flame front dynamics through blowoff. All flames were found to exhibit Benard–von Karman vortex shedding just prior to blowoff. The POD time constants demonstrate that a strong fuel gradient decreases the time it takes for the flame to shift from its mean fully burning shape to blowoff and decreases the dwell time of the flame in the recirculation zone following local extinction. These time scales indicate a faster blowoff process with fuel stratification.

C/H atom ratio in recirculation-zone-supported premixed and nonpremixed flames

Recent measurements of Barlow et al. in a bluff-body burner revealed that local atom balances were not conserved. They attributed the observed higher C/H atom ratios to the preferential diffusion of certain species and longer residence times in the recirculation zones (RZs). For verifying this hypothesis, detailed calculations for the reacting flows in the bluff-body burner were made using UNICORN code incorporated with GRI version 3.0 chemical kinetics. A lean mixture (Φ=0.77) of methane and air was used as fuel jet. Time-dependent laminar simulations resulted in steady RZs for fuel jet velocities up to 7.0m/s. Similar to experiments, calculations also revealed nonuniform distributions for C/H atom ratio in the flame at all heights. Results were compared to the data obtained for an unstrained 1D flame. Simulations for the bluff-body flame were repeated after setting diffusion coefficients of every species equal to that of O2. In the absence of preferential diffusion, C/H atom ratio was found to be equal to 0.25 everywhere in the flame. For understanding the effects of flame stretch on C/H atom ratio, calculations were made for the double flames formed between the opposing jets of premixed methane–air mixtures at different velocities. Distributions of C/H atom ratio in the RZ-supported nonpremixed flame were investigated through performing calculations for the Air Force centerbody burner fueled with ethylene. Both the attached and lifted-flame conditions were studied for understanding the role of RZs in enhancing C/H atom ratio. It was found that the hypothesis proposed by Barlow et al. in general, explains the higher C/H atom ratios found in bluff-body flames. However, RZs are not found to enhancing the preferential diffusion effects. Instead, the sharp velocity gradients near the fuel jet in the vicinity of the bluff-body surface increased the removal of H2O.

Self-excited circumferential instabilities in a model annular gas turbine combustor: Global flame dynamics

In this paper the global flame dynamics of a model annular gas turbine combustor undergoing strong self-excited circumferential instabilities is presented. The combustor consisted of either 12, 15 or 18 turbulent premixed bluff-body flames arranged around an annulus of fixed circumference so that the effect of flame separation distance, S, on the global heat release dynamics could be investigated. Reducing S was found to produce both an increase in the resonant frequency and the limit-cycle amplitudes of pressure and heat release for the same equivalence ratio. The phase-averaged global heat release, obtained from high-speed OH∗ chemiluminescence imaging from above, showed that these changes are caused by large-scale modifications to the flame structure around the annulus. For the largest S studied (12 flame configuration) the azimuthal instability produced a helical-like global heat release structure for each flame. When S was decreased, large-scale merging or linking between adjacent flames occurred spanning approximately half of the annulus with the peak heat release concentrated at the outer annular wall. The circumferential nature of the instability was evident from both the pressure measurements and the phase-averaged OH∗ chemiluminescence showing the phase of the heat release on either side of the annulus to be ≈180° apart and spinning in the counter clockwise direction. Both spinning and standing modes were found but only spinning modes are considered in this paper. To the best of the authors knowledge, these are the first experiments to provide a phase-averaged picture of self-excited azimuthal instabilities in a laboratory-scale annular combustor relevant to gas turbines.

Characterization of flame-shedding behavior behind a bluff-body using proper orthogonal decomposition

Researchers have been interested in bluff-body flame-shedding dynamics and the effects of vortex shedding for the past few decades. The objective of the present study is to quantify various modes of vortex shedding as flames transition from near-blow-off to stable and acoustically coupled conditions. Two modes of shedding, Kelvin–Helmholtz and Von-Karman, play a significant role in flame stability. Previous studies have been limited to visual identification of the contributions from each of these modes without quantitatively addressing the contribution from each mode as the flame transitions from blow-off to a stable or acoustically coupled state. The present study is focused on quantitatively identifying the contribution of various instability modes for three 1.5-in. flame-holder configurations and is performed in an augmentor test rig employing propane and air as fuel and oxidizer, respectively. The quantitative identification of instability modes is performed by implementing proper orthogonal decomposition (POD) on high-speed chemiluminescence imaging for various flame configurations. The application of POD provides an objective means of examining contributions from asymmetric, symmetric, and uncorrelated spatial shedding modes. To determine trends, equivalence ratios are set to 1.1 and then stepped down until blow-off. Acoustically coupled flames are observed to be dominated by contributions from the symmetric shedding mode. As flames decouple from rig acoustics, they exhibit increased combinations of asymmetric and uncorrelated shedding behavior, depending on flow conditions. The methodology can also be extended to other measurement techniques such as high-speed particle-image velocimetry, planar laser-induced fluorescence, and numerical simulations as a means of studying bluff-body flames.

Simulation of vortex shedding behind a bluff body flame stabilizer using a hybrid U-RANS/PDF method

The present study aims at the investigation of the effects of turbulence-chemistry interaction on combustion instabilities using a probability density function (PDF) method. The instantaneous quantities in the flow field were decomposed into the Favre-averaged variables and the stochastic fluctuations, which were calculated by unsteady Reynolds averaged Navier-Stokes (U-RANS) equations and the PDF model, respectively. A joint fluctuating velocityfrequency-composition PDF was used. The governing equations are solved by a consistent hybrid finite volume/Monte-Carlo algorithm on triangular unstructured meshes. A nonreacting flow behind a triangular-shaped bluff body flame stabilizer in a rectilinear combustor was simulated by the present method. The results demonstrate the capability of the present method to capture the large-scale coherent structures. The triple decomposition was performed, by dividing the coherent Favre-averaged velocity into time-averaged value and periodical coherent part, to analyze the coherent and incoherent contributions to Reynolds stresses. A simple modification to the coefficients in the turbulent frequency model will help to improve the simulation results. Unsteady flow fields were depicted by streamlines and vorticity contours. Moreover, the association between turbulence production and vorticity saddle points is illustrated.

Measurements in turbulent premixed bluff body flames close to blow-off

The structure of unconfined lean premixed methane–air flames stabilized on an axisymmetric bluff body has been examined for conditions increasingly closer to blow-off and during the blow-off event. Fast imaging (5kHz) of OH∗ chemiluminescence and OH-PLIF and PIV (at 1kHz) were used to obtain instantaneous and time-averaged images, temporal sequences, spectra of OH, 2-D estimates of flame surface density, curvature, turbulence statistics, and measurements of the duration of the blow-off transient. Blow-off was approached by slowly reducing the fuel flow rate, and the flame shape was seen to change from a cylindrical shape at stable burning conditions, with the flame brush closing across the flow at conditions close to the blow-off condition. This was followed by entrainment of fresh reactants from the downstream end of the recirculation zone (RZ), and fragmentation of the downstream flame parts. Just before the blow-off event, reaction fronts were observed inside the RZ, with progressive fragmentation occurring, leading to a shorter flame brush. Complete extinction occurred once the flame at the attachment point had been destroyed, and stabilization at the shear layers was no longer possible. Measurements showed a gradual reduction in FSD during the approach to blow-off and during the extinction event itself, and higher values of flame front curvature at conditions approaching extinction. The local Karlovitz number was estimated based on the local turbulence velocity and lengthscale characteristics and it reached a maximum value of about 10 at the location where the flame bends towards the axis. Quantification of the duration of the blow-off event showed that it was an order of magnitude longer than the characteristic timescale of the burner d/Ub. The measurements reported here are useful for model validation and for exploring the changes in turbulent premixed flame structure as extinction is approached.

Large-eddy Simulation of Triangular-stabilized Lean Premixed Turbulent Flames: Quality and Error Assessment

In this numerical study, an algebraic flame surface wrinkling (AFSW) reaction submodel based on the progress variable approach is implemented in the large-eddy simulation (LES) context and validated against the triangular stabilized bluff body flame configuration measurements i.e. in VOLVO test rig. The quantitative predictability of the AFSW model is analyzed in comparison with another well validated turbulent flame speed closure (TFC) combustion model in order to help assess the behaviour of the present model and to further help improve the understanding of the flow and flame dynamics. Characterization of non-reacting (or cold) and reacting flows are performed using various subgrid scale models for consistent grid size variation with 300,000 (coarse), 1.2 million (intermediate) and 2.4 million (fine) grid cells. For non-reacting flows at inlet velocity of 17 m/s and inlet temperature 288 K, coarse grid leads to over prediction of turbulence quantities due to low dissipation at the early stage of flow development behind the bluff body that convects downstream eventually polluting the resulting solution. The simulated results with the intermediate (and fine) grid for mean flow and turbulence quantities, and the vortex shedding frequency (fs) closely match experimental data. For combusting flows for lean propane/air mixtures at 35 m/s and 600 K, the vortex shedding frequency increase threefold compared with cold scenario. The predicted results of mean, rms velocities and reaction progress variable are generally in good agreement with experimental data. For the coarse grid the combustion predictions show a shorter recirculation region due to higher turbulent burning rate. Finally, both cold and reacting LES data are analyzed for uncertainty in the solution using two quality assessment techniques: two-grid estimator by Celik, and model and grid variation by Klein. For both approaches, the resolved turbulent kinetic energy is used to estimate the grid quality and error assessment. The quality assessment reveals that the cold flows are well resolved even on the intermediate mesh, while for the reacting flows even the fine mesh is locally not sufficient in the flamelet region. The Klein approach estimates that depending on the recirculation region in cold scenario both numerical and model errors rise near the bluff-body region, while in combusting flows these errors are significant behind the stabilizing point due to preheating of unburned mixture and reaction heat release. The total error mainly depends on the numerical error and the influence of model error is low for this configuration.

The Optimal Selection Investigation on Flame Holder for Afterburner

In order to determine the bluff body and slitted bluff body flame stability and combustion performance, atmospheric low-speed experimental platform was used to carry out diesel fog combustion experiment for two types of bluff body, which are respectively streamlined V-form added straight channel and triangle V-form added straight channel. Results have shown that flame stability and combustion efficiency of streamlined bluff body is orderly slit width at 13mm, 6mm, 0mm and the triangular bluff body is orderly slit width at 6mm, 13mm, 0mm. Optimal combustion performance is streamlined bluff body with slit width 13mm.

Error analysis of large-eddy simulation of the turbulent non-premixed sydney bluff-body flame

A computational error analysis is applied to the large-eddy simulation of the turbulent non-premixed Sydney bluff-body flame, where the error is defined with respect to experimental data. The error-landscape approach is extended to heterogeneous compressible turbulence, which is coupled to combustion as described by a flamelet model. The Smagorinsky model formulation is used to model the unknown turbulent stresses. We introduce several measures to quantify the total simulation error and observe a striking ‘valley-structure’ in the error that arises as function of the spatial resolution and the Smagorinsky length parameter. The optimal refinement strategy that can be extracted from this error-landscape is reminiscent of that for non-reacting turbulent flow.