Structure Of Turbulent Flames Research Articles

Learning-Based Super-Resolution Imaging of Turbulent Flames in Both Time and 3D Space Using Double GAN Architectures

This article presents a spatiotemporal super-resolution (SR) reconstruction model for two common flame types, a swirling and then a jet flame, using double generative adversarial network (GAN) architectures. The approach develops two sets of generator and discriminator networks to learn topographic and temporal features and infer high spatiotemporal resolution turbulent flame structure from supplied low-resolution counterparts at two time points. In this work, numerically simulated 3D turbulent swirling and jet flame structures were used as training data to update the model parameters of the GAN networks. The effectiveness of our model was then thoroughly evaluated in comparison to other traditional interpolation methods. An upscaling factor of 2 in space, which corresponded to an 8-fold increase in the total voxel number and a double time frame acceleration, was used to verify the model’s ability on a swirling flame. The results demonstrate that the assessment metrics, peak signal-to-noise ratio (PSNR), overall error (ER), and structural similarity index (SSIM), with average values of 35.27 dB, 1.7%, and 0.985, respectively, in the spatiotemporal SR results, can reach acceptable accuracy. As a second verification to highlight the present model’s potential universal applicability to flame data of diverse types and shapes, we applied the model to a turbulent jet flame and had equal success. This work provides a different method for acquiring high-resolution 3D structure and further boosting repeat rate, demonstrating the potential of deep learning technology for combustion diagnosis.

Development of a multiple laser-sheet imaging technique for the analysis of three-dimensional turbulent explosion flame structures

The present work describes the development of a multiple laser-sheet imaging technique for the study of turbulent, premixed flame surface structures at high Karlovitz stretch factor values. Experiments were conducted using CH4 air mixtures at 365 K and 0.5 MPa and up to a root mean square turbulence velocity of 1.5 m/s. A high-speed Nd:YAG laser capable of pulsing up to 60 kHz in conjunction with a high-speed camera and a rotating mirror was used to reconstruct time-resolved three-dimensional turbulent flames. This has, for the first time, enabled the direct measurement of wrinkled flame surface areas, along with reaction progress variable and flame brush thickness. These are important parameters for the characterization of turbulent burning rates and provide more insight into the dynamic nature of the flames and their structures. In addition, the current data aid toward direct comparison with results from combustion simulation studies.

Large eddy simulation of a supersonic lifted hydrogen flame: Impacts of Lewis, turbulent Schmidt and Prandtl numbers

Parametric large eddy simulations (LES) of a supersonic lifted hydrogen flame are reported. The emphases are on two aspects: impacts of (1) Lewis number (Lei of the ith species) and (2) turbulent Schmidt and Prandtl numbers (Sct and Prt) on supersonic turbulent flame and flow structures. Five cases are considered: species-specific Lei, Sct=Prt=1.0 (C0); unity Lei, Sct=Prt=1.0 (C1); species-specific Lei, Sct=0.5, Prt=1.0 (C2); species-specific Lei, Sct=1.0, Prt=0.5 (C3); and species-specific Lei, Sct=Prt=0.5 (C4). Numerical results of instantaneous and/or time-averaged species mole fractions, mixture fraction, heat release rate, flame base location, and mixed modes of premixed and diffusion combustion are compared between cases C0 and C1. Differences in auto-ignition locations and strengths and flame structures and stabilization specify the impacts of Lewis number. They are triggered by different predictions of species mass and thermal diffusions at fuel-coflow and/or coflow-ambient air mixing layers. These differences are rationalized by a scale analysis of mass/thermal diffusion and convection for case C0, which suggests the relatively low but non-negligible former against the latter. Cases C0 and C2–C4 barely see differences in terms of instantaneous and/or time-averaged temperature, velocity, and mixed combustion modes except for further downstream areas where combustion occurs. Both Sct and Prt impose less significant influences than Lewis number, as sub-grid scale mass/thermal diffusion is subordinate to its resolved counterpart according to their scale analysis for case C4.

Characterizing turbulent non-premixed flame structure and pollutant formation of cracked ammonia jet flames using simultaneous NH and NO PLIF

The combustion of cracked ammonia is crucial for enhancing flame stability and reducing pollutant emissions in ammonia-based combustion systems. This study investigated the flame structure and pollutant formation in cracked ammonia jet flames (CAJFs) to improve our understanding of the turbulence-chemistry interactions in ammonia combustion. A simultaneous NH and NO planar laser-induced fluorescence (PLIF) technique was employed to analyze the flame structure of turbulent non-premixed CAJFs, emulated using ammonia-hydrogen–nitrogen mixtures. Experimental measurements were conducted across a range of pressures (1–5 bar) and cracking ratios (7 %-28 %). The results revealed the significant influence of the cracking ratio on the chemical reactivity and NH-layer characteristics of ammonia-hydrogen flames. NH effectively marked the heat release layer of CAJFs. Reducing the cracking ratio from 28 % to 7 % resulted in increased local extinction-induced NH-layer fragmentation and reduced reaction area. The reaction layer thickness exhibited low sensitivity to the cracking ratio and pressure, while the broadening of the NH layer displayed a slowdown pattern with increasing height, differing from premixed flames. The pollutant NO rapidly formed within the reaction zone, persisting in the outer hot products until reduced by turbulent mixing. The fragmented flame structure promoted decreased NO formation and potentially lower NO concentration. A novel approach of multiplying NH and NO was proposed to reflect the formation characteristics of another important pollutant N2O. The effect of turbulent disturbances on N2O formation needs to be considered in turbulent CAJFs because N2O formation is strongly suppressed when turbulent transport reduces local NO concentration. This research enhances understanding of turbulence-chemistry interactions in cracked ammonia combustion, benefiting ammonia flame stability and pollutant emission control.

Extraction of turbulent flame structures and dynamic modes with corrected OH-PLIF images for a hydrogen micromix burner

Diluted micromix combustion technology is an effective way to realize stable H2 flames with low NOx emission, and the turbulent flame structures of a micromix burner are experimentally revealed in this work with corrected OH-PLIF images.

A consistent MMC-LES approach for turbulent premixed flames

A multiple mapping conditioning (MMC) approach is coupled with large eddy simulations (LES) for the prediction of the flame propagation, the flame structure and finite rate chemistry effects including NO formation in turbulent premixed flames. The mixing term in MMC relies on a reference field that characterizes the chemical composition within the flame and it is typically taken to be the reaction progress variable. In LES, this reference field needs to be artificially thickened to be resolved on the LES grid. A novel MMC mixing time scale model that had been developed with the aid of direct numerical simulation (DNS), has been adapted to account for the thickening of the reference field. Equally, the particle selection mechanism for particle mixing has been modified to ensure localness of mixing in composition space and to preserve the prediction of a realistic (thin) flame thickness by the stochastic particles. A set of freely propagating turbulent premixed flames with varying equivalence ratios is used to test the performance of the MMC model. Results of MMC-LES are compared with reference DNS that include full chemistry. Additional simulations were carried out where MMC is coupled with quasi-DNS where the flow field is fully resolved but the reaction progress variable field is thickened and its source term is closed with a flamelet approach. This allows to isolate the different modelling assumptions invoked in MMC-LES. Deviations from the exact solution can then be associated with the MMC approach and with thickening of the reference field separately and they are small. The MMC-LES predictions of the turbulent premixed flame propagation speed and flame structure are very good and finite rate chemistry effects can be captured well which is demonstrated by good agreement of predicted NO with DNS data.

A Direct Numerical Simulation Study for Flame Structure and Propagation Characteristics of Multi-Jet Flames

ABSTRACT Lifted multi-jet flames of hydrogen and steam-diluted oxygen are studied using direct numerical simulations (DNS). The DNSs have been carried out for laminar and turbulent flame configurations. The simulation data are analyzed to investigate the flame and flame-base structures and the flame-base propagation in a configuration akin to a gas turbine with multiple fuel jets. The laminar flames have a tribrachial structure, although lean premixed and diffusi on flame branches collide downstream owing to preferential diffusion. The turbulent multi-jet flames have a single connected base region, whereas the laminar flames have separate bases, each of which is associated with the corresponding fuel jet. Although turbulent multi-jet flames have substantially different flame-base characteristics from laminar multi-jet flames (and conventional single-jet lifted flames), the propagation speed is similar for both conditions. The results suggest that the well-known flame-base stabilization theory can be straightforwardly applied to the multi-jet configuration, despite the turbulent flame structure’s unconventional features.

On the structure of buoyant fires with varying levels of fuel-turbulence

This paper employs a novel burner to study the effects of fuel-generated turbulence on the spatial and temporal structure of buoyant turbulent diffusion flames which are representative of large fires. Fuel-turbulence levels are increased using a perforated plate that issues high-velocity jets, enabling shearing of the fuel stream. The perforated plate may be recessed to control the turbulence level at the jet exit plane. It is shown that the exit plane axial velocity fluctuations can be increased from 0.135 m/s to 1.813 m/s. Varying the levels of fuel-turbulence in the burner allows for the control of key processes defining buoyant fires such as the spatial and temporal flame structure and flame instability modes. These processes are characterised by high-speed simultaneous imaging of planar laser-induced fluorescence of the OH radical (OH-PLIF) and Mie scattering from soot particles. Increasing the fuel-turbulence level deforms the flame, which promotes non-radial lateral entrainment into the flame sheet. This results in a sharp increase in the tilting of the near-field flame sheet along the vertical flame axis. Strong angular entrainment forces are shown to overcome the diffusive and thermal expansive forces at the flame neck, which leads to a strained asymmetric sinuous flame pinch-off instability, followed by separation of the flame base. Sinuous pinch-off instabilities occur at a greater frequency than the symmetric varicose pinch-off instabilities observed for flames with low fuel-turbulence. The asymmetric stretching of the flame neck inhibits the formation of the classical puffing instability formed with an axisymmetric plume that defines classically buoyant flames. Probability density functions calculated for the flame front curvature and flame surface area are shown to monotonically broaden in the near-field region of the flame due to lateral entrainment effects. The transition to buoyancy-driven turbulence also shifts to an increasingly more upstream location. This burner, with its well-defined boundary conditions and novel data, forms a platform for advancing capabilities to model complex fire phenomena including turbulence-buoyancy interactions.

Direct numerical simulation of NH3/air combustion with H2 addition under HCCI relevant conditions

In the present work, two-dimensional direct numerical simulations (DNS) of NH3/air turbulent combustion with H2 addition under homogeneous-charge compression ignition (HCCI) relevant conditions were performed to explore the ignition and combustion characteristics. Three hydrogen addition levels in the fuel were considered with molar fractions of 0.0 (pure ammonia), 0.1 and 0.8. The corresponding one-dimensional laminar flames were also simulated to provide reference solutions. The general combustion characteristics were first presented. It was found that turbulence and thermal stratification facilitate the ignition process. The ignition occurs earlier with increasing hydrogen addition levels and temperature fluctuations. After ignition, high heat release rate (HRR) occurs simultaneously over the entire domain with low temperature fluctuations while significant HRR occurs in narrow sheets with high temperature fluctuations. HRR is significantly enhanced in positive curvature regions of the cases with high hydrogen addition levels due to the preferential diffusion of H and other radicals. The combustion mode was examined based on the analysis of the displacement speed and species transport equation budget. The mean displacement speed is decreased with increasing temperature fluctuations and the budget analysis suggests that high temperature gradient facilitates deflagration. The reaction fronts are thinner with increasing H2 addition levels, and the combustion mode of deflagration is promoted. The effects of turbulence intensity on the flame structure and combustion mode were evaluated. The ignition occurs earlier and the area of the reaction front increases with increasing turbulence intensity. The magnitude of the temperature gradient also increases with increasing turbulence intensity, which facilitates the occurrence of deflagration. The turbulent flame structures were compared with the corresponding 0D ignition and 1D thermally stratified flame results, and it was found that the mean turbulent flame structure can be well approximated by 1D thermally stratified flames.

Interactions between high hydrogen content syngas–air premixed flames and homogeneous isotropic turbulence: Flame thickening

This paper reports the findings from a three-dimensional direct numerical simulation conducted to investigate the turbulent flame behaviors of premixed high-hydrogen content syngas (with 50% hydrogen on a per mole basis) and air mixtures. To accomplish this, a laminar flame front is placed in a homogeneous isotropic decaying turbulence field composed of a syngas–air mixture at an equivalence ratio of 0.7 and allowed to evolve for 1.4 eddy turnover times. Homogeneous isotropic turbulence is generated using a helical forcing function in a cubic domain with a grid size of 256 × 256 × 256. The Reynolds number based on the Taylor microscale, Reλ, is 57 for the generated turbulence field. The laminar flame front is placed at the center of the domain. The premixture enters the domain at a velocity of 8 m/s and at an initial temperature of 800 K. The pressure remains constant at 1 atm. In addition to quantifying the spatial and temporal evolution of turbulent characteristics and flame structure, the study also focuses on identifying turbulence/flame interactions, specifically, the impact of these interactions on flame thickness. Energy transfer from small to large scales, i.e., a reverse cascade is observed as a result of energy release due to chemical reactions at the small scales that is transferred to larger scales. The increase in turbulent intensities due to chemical reactions correlates with flame thickening.

The turbulent flame structure in a steam diluted H2/Air micromix flame

In order to safely organize hydrogen flame with low NOx emission in traditional gas turbines and industrial burners, an attractive combustion technology is the steam diluted micromix combustion technology. The effects of equivalence ratio (φ), steam dilution ratio (D) and nozzle diameter (d) on the turbulent flame structure in a steam diluted H2/air micromix flame were investigated experimentally with a 10 kHz high-speed OH∗ chemiluminescence imaging system to detect the instantaneous flame zone. With the increase of equivalence ratio (φ) or the decrease of steam dilution ratio (D), the overall OH∗ signal intensity and the area of OH∗ signal increase. The maximum OH∗ signal intensity along the axial direction (Z) is distributed far from the nozzle outlet with the increase of nozzle diameter (d). Two types of flame were found for time-averaged images, namely the anchored flame and the lifted flame. And the increase of hydrogen velocity could lead to the changing of flame from anchored to lifted due to lower uniformity of the fuel-air mixture at the nozzle outlet. The instantaneous flames for larger nozzle diameter appear as “M” or “V” shape, and the changing of flame shape indicates an unstable combustion. This was further discussed with the OH∗ spatial distribution uniformity (SDU) and its variation determined by the coefficient of variation (CV) parameter.

Structure and propagation of spherical turbulent iron-methane hybrid flame at elevated pressure

In this communication we demonstrate the role of turbulence intensity in the dual-front structure and self-similar propagation of spherical turbulent iron-methane hybrid flames. We first show that iron-methane hybrid mixture, whose iron concentration is below a critical threshold for the formation of a dust flame front in laminar or weak turbulent environment, can be burned strongly with both separated dual-front and merged single-front structures in intense turbulence. It is suggested that the formation of iron flame front would be attributed to local iron concentration accumulation by preferential sampling with near-unity Stocks number (St), heat transfer enhancement of iron particles to fluid and mixing promotion of iron particles with oxidants by strong turbulence. The propagation of iron front falls behind the methane front in the leading segments which is promoted by flame stretch for sub-unity Lewis number (Le), thus the separated dual-front structure occurs. Furthermore, the strong self-similar propagation of spherical turbulent iron-methane hybrid flame was observed under different turbulence intensities (urms). Mechanistically, such strong self-similar propagation of the hybrid flame is the consequence of the couple effects of flame mode transition at high urms with near-unity St and differential diffusion for sub-unity Le.

Experimental and theoretical study of combustion and aerothermodynamic effects on the flame structure from wind-driven rectangular fires

This work provides a comprehensive model for global morphology parameters of flame structure of turbulent diffusion flames in wind-driven rectangular burner fires. Five flame morphology parameters were configured by using the image from CCD cameras and CFD calculations, demonstrating for the first time the image corresponds to a mixture fraction. The unique physics-based similarity correlations for the combustion were proposed to predict the morphology parameters of flame structures in terms of a characteristic length scale. The reliability of the current physical model and new correlations was validated by comparing it with other literature data. One important result of this paper is that the source size does not affect the flame morphology if a Froude number based on the source size is greater than a fraction of the ratio of the flame length at no wind to the source size. Subsequently, based on top hat similarity of the flow profiles, a phenomenological integral combustion model including momentum and continuity equations was also established and the results were compared well with the experimental data and the new correlations. Finally, CFD numerical modeling and large-scale experimental data in the literature were employed to verify the applicability of the present model for large-scale pool fire combustion.

Numerical investigation to evaluate the effects of gravity and pressure on flame structure and soot formation of turbulent non-premixed methane-air flame

In this study, a turbulent non-premixed (diffusion) methane-air flame has been investigated computationally to analyze the influences of pressure and gravity on flame structure and sooting characteristics between 1 and 10 atm. The simulation has been conducted in a 2-D axisymmetric computational domain using the finite volume-based computational fluid dynamics (CFD) code. The interaction of turbulence and chemistry is modeled by considering the steady laminar flamelet model (SLFM) and the GRI Mech 3.0 chemical mechanism. The radiative heat transfer calculation is carried out by considering the discrete ordinate (DO) method and the weighted sum grey gas model (WSGGM). The semi-empirical Moss-Brookes model is considered to calculate soot. The impact of gravity on flame and sooting characteristics are evaluated by comparing the normal-gravity flames with the zero-gravity flames. The effect of soot and radiation on flame temperature is also examined. The results show a close agreement with the measurement when both soot and radiation are included in the numerical modeling. The rates of soot formation, surface growth, and oxidation increase with increased operating pressure, regardless of gravity. Zero-gravity flames have a higher soot volume fraction, a wider soot-containing zone, a higher CO mass fraction, and a lower flame temperature than normal-gravity flames while maintaining constant pressure. In normal-gravity flames, the CO mass fraction decreases with pressure, whereas it increases with pressure rise in flames of zero gravity. Flames of zero gravity appear taller and broader compared to the flames of normal-gravity for a fixed pressure. An increase in pressure significantly reduces the flame length and width in normal-gravity flames. However, the pressure elevation has little effect on the shape of a zero-gravity flame. The outcomes of the present study will assist in fully understanding the combustion and sooting characteristics of turbulent diffusion flames that will help design and develop high-efficiency, pollutant-free combustion devices and fire suppression systems for space application.

Multiple Mapping Conditioning Mixing Time Scales for Turbulent Premixed Flames

A novel multiple mapping conditioning (MMC) mixing time scale model for turbulent premixed combustion has been developed. It combines time scales for the flamelet and distributed flame regimes with the aid of a blending function. The blending function serves two purposes. Firstly, it helps to identify zones where the premixed flame resides and where the time scale associated with the premixed flame shall be used. Secondly, it uses the Karlovitz number to identify the turbulent premixed combustion regime and to reduce the weighting of the premixed flame time scale if Karlovitz numbers are high and deviations from the flamelet regime are expected. A series of three-dimensional direct numerical simulations (DNS) of statistically one dimensional, freely propagating turbulent methane-air flames provides a wide range of turbulent combustion regimes for the mixing model validation. The new mixing time scale provides correct predictions of the flame speed of freely propagating turbulent flames which could not be matched by most recognized mixing models. The turbulent flame structure predicted by the new model is in good agreement with DNS for all combustion regimes from flamelet to the thickened reaction zone.

Temporally resolving premixed turbulent flame structures using self-supervised adversarial reconstruction of CH-PLIF

Understanding the turbulence-flame interaction is crucial to model the low-emission combustors developed for energy and propulsion applications. To this end, a novel frame interpolation (FI) method is proposed to better resolve the spatiotemporal evolution of premixed turbulent flame structures. The framework is completely self-supervised, agnostic to optical flow, and driven by leveraging transferrable feature knowledge at lower speeds and adversarial learning to statistically map the flame dynamics across frames. The method is successfully applied on a 10 kHz CH planar laser-induced fluorescence (PLIF) dataset of highly wrinkled premixed flames with turbulent Reynolds numbers (ReT) of 1100, 1400, and 7900, by down-sampling the image sequence to 5 kHz and restoring the sequence back to 10 kHz via FI. All reconstructions recovered important flame events and displayed excellent resemblance of the corrugated CH-layer geometries to that of the ground truths, with average intersection over union (IoU) and structural similarity index (SSIM) scores of 0.49 and 0.82, which are above the high-similarity baselines of 0.36 and 0.75, respectively. The wrinkling parameters (WP) of the flames also matched the ground truths, wherein R2 was roughly 0.95 for ReT = 1100 and 1400 and 0.85 for ReT = 7900 (lower due to the turbulence-induced uncertainties). The FI is further iteratively repeated to 40 kHz on the ReT = 7900 flames to facilitate pocket analysis by confidently linking their origin of formation, thus, enabling distinction from 3D tunnels, and improving statistical characterization of their consumption speeds. Given that the object features do not exhibit highly turbulent motions with regard to the initial time step, the proposed FI method is shown to be highly accurate and useful to analyzing finite-resolution experimental image sets including, but not restricted to, CH-PLIF.

Spatially-Resolved experimental investigations of combustion characteristics in a solid fuel doped methane swirl flame and the influence on the formation of ultrafine particulate matter

The formation of inhalable fine particles (dp≤10 µm) is an undesirable side effect of solid fuel combustion processes. These particles can accumulate in the human respiratory system and thus cause severe lung damage. Therefore, an understanding of the formation of these particles is of crucial importance to avoid or to reduce the amount of fine particulate matter (PM) released into the atmosphere. Until now, most of the studies have been carried out for laminar and early-stage solid fuel combustion under simplified conditions (e.g. flat flame burner with radial almost homogeneous conditions) and only a few studies have been carried out with more complex turbulent flame structures. As the majority of real applications on an industrial scale involves turbulent conditions, research in this area is highly important. For the investigation of particulate matter formation, a swirled methane-assisted pulverized solid fuel combustion test rig with full optical access which allows intrusive and non-intrusive measurements in different heights and radial positions was developed. In order to study the local influences of flame characteristics on the formation of ultrafine particulate matter, results from laser Doppler velocimetry (LDV), suction pyrometer, Fourier transform infrared (FTIR) spectroscopy, and scanning mobility particle sizer (SMPS) spectrometer measurements are presented and discussed. It is shown that the local differences - such as gas temperature, the velocity of the solid fuel particles, and concentrations species - have an influence on the formation of particulate matter. Especially in regions with high local velocities and shear zones, PM coagulates strongly due to the increased turbulence in this area. The data presented in this paper are an important foundation for further studies to validate CFD simulations using the measurements and to further develop existing PM formation models for turbulent cases.

Design and testing of an additively manufactured flameholder for scramjet flows

A small-scale cavity flameholder for high-speed, premixed ethylene combustion has been designed, additively manufactured, and tested at Mach 5 enthalpy. The work has enabled a comprehensive study on the effects of flow compressibility and heat release on turbulent flame structures and stabilization mechanisms. The cavity is sized to produce a practical computational domain for Direct Numerical Simulations. Likewise, the flameholder is supported away from the flow path walls to minimize boundary layer growth upstream and simplify the numerical calculations. Optical access is provided for laser diagnostics. Challenges related to transforming a direct-connect combustor flow path into a semi-free jet flow path for immersed models were encountered, primarily flow blockage and heat removal. The final design can sustain an ethylene flame for repeated cycles lasting more than an hour. The flameholder was fabricated from Inconel 718 with internal cooling passages incorporated throughout. This paper presents a methodology for design and fabrication of additively manufactured scramjet combustor components and documents the first published conversion of a direct-connect, high-speed combustion wind tunnel to a semi-free jet configuration. While additive manufacturing enables novel designs with complex geometries, residual stresses and geometric distortion are notable concerns that must be considered in the design stages.

프랙탈 난류생성판을 갖는 V-shape 화염에서 난류 예혼합 화염 분석 : Part. Ⅲ 난류 연소속도

This study focused on calculating the turbulent flame speed in a V-shape turbulent premixed flame using a circular fractal turbulence generator. In previous studies [Part. I turbulent flow characteristics in a Non-Reacting Field], [Part. II characteristics of turbulent flame structures], the non-reactive turbulent flow and turbulent flame structure for the V-shape flame of a fractal turbulence generator were investigated in detail. Two types of turbulent burning velocities are evaluated : local displacement and consumption speeds. The local consumption speed is calculated via the image processing of flame surface density. The results show that turbulent burning velocity increases much with fractal grids as compared with the conventional grids perforated plate and mesh. Finally, it was confirmed that the correlation between the turbulent flow factor and the two turbulent burning velocities of each turbulence generator was collapsed well with a specific correlation equation.

프랙탈 난류생성판을 갖는 V-shape 화염에서 난류 예혼합 화염 분석: Part. II 난류화염의 구조 특징

This study focuses on the characteristics of turbulent flame structures in V-shape turbulent premixed flames to evaluate the turbulent combustion dynamics of fractal turbulence generator. The details of the non-reactive turbulent flow characteristics with the fractal turbulence plate were explained in the previous study of Part I. In this work, the integral length scale of non-reactive flow was additionally investigated to obtain a Borghi-Peters diagram. By comparing the Borghi-Peters diagram shown as a result of the non-reactive flow with the reaction OH-PLIF image, it was confirmed that the flame characteristics for each regime were well represented. Also, the irregular turbulence of premixed flame was quantitatively analyzed using the flame brush obtained by the mean progress variable method. As a result, the flame brush of the fractal turbulence generator was wider than the perforated plate and mesh type. Finally, it was found that the thickness and angle of the flame brush were proportional to the turbulence intensity and turbulent Reynolds number, which are dimensionless numbers of turbulent flow.