Methane Flames Research Articles

Dynamics of 2D, V-shaped Bluff-body Stabilized Turbulent Premixed Flames near and Away from Blowoff with Different Gaseous Fuels

ABSTRACT V-shaped premixed flames of propane, methane, and ethylene-air mixtures were stabilized on a triangular-shaped flame holder under three different free stream turbulence levels; 4%, 18%, and 34% rms at a nominal burner exit velocity of 10 m/s. Flames were studied at strongly burning and near blowoff conditions to observe the changes in the overall flame dynamics. Flame behavior at different upstream flow turbulence conditions was visualized by simultaneously capturing the end and side views of flame chemiluminescence using high speed (4 kHz) imaging. A gradual shift from symmetric to asymmetric flame structures was observed with reduction of equivalence ratio approaching blowoff. Particle image velocity measurements confirmed the gradual switch of vortex shedding from symmetric varicose mode to the asymmetric sinuous mode as flame blowoff is approached by reduction of the mixture equivalence ratio. It is found that average flame front position crosses the shear layer from its outer location at strongly burning conditions to within the shear layers bounding the recirculation zone as flame blowoff is approached. Transition of flame behavior from “varicose” to “sinuous” oscillations is documented by way of a symmetry index as a function of equivalence ratio and turbulence intensity for the three fuels studied.

Effects of ignition disturbance on flame propagation of methane and propane in a narrow-gap-disk-burner

Unsteady flame propagation within a narrow channel, namely a Hele-Shaw burner, exhibits complicated phenomena. Recently, a new narrow-gap-disk-burner (NGDB) was developed, of which the disk-gap could be varied continuously and precisely. Although various complicated flame structures have been observed successfully, their dependency on the initial ignition has not been clarified. In this study, the volume of the ignition part was varied to introduce disturbance at the ignition stage, and the propagation characteristics of premixed methane and propane flames were investigated. Conclusively, quenching distance was not significantly affected by the ignition volume, especially in propane-rich conditions. In contrast, the flame structure and propagation velocity were sensitive to the ignition volume if it was larger than a critical volume, and when the disk-gap was approximately 1.5 times the quenching distance. A strong initial disturbance could generate complicated cellular structures coupled not only with shear stress but also with heat transfer. These cellular structures could increase the flame propagation velocity when the Lewis number was sufficiently smaller than unity. In contrast, the flame shape became smoother when the disk-gap was sufficiently larger than the quenching distance. Thus, the flame propagation velocity was comparable to the laminar burning velocity when it was less affected by the initial disturbance.

Dilution effect of different combustion residuals on laminar burning velocities and burned gas Markstein lengths of premixed methane/air mixtures at elevated temperature

Most of the experimental examinations on laminar flame characteristics of a diluted combustible mixture have simulated combustion residuals with one of the main exhaust gases (N2, H2O, and CO2) or a mixture of two. However, flue gases have quite different thermodynamic properties and chemical reactivities. Therefore, simulating the post combustion products used for dilution with only one or two of the main exhaust gases may yield erroneous laminar flame characteristic data. In the present study, the laminar burning velocities and burned gas Markstein lengths of diluted methane/air mixtures at 1 bar and 473 K were measured with spherically expanding flames under constant pressure in an optically accessible constant volume combustion chamber. The mixtures were diluted with N2, H2O, and CO2 individually as well as with a mixture of 71.49% N2 + 19.01% H2O + 9.50% CO2 by volume, which represents the main product concentrations from stoichiometric methane/air combustion. Experimental results show that the laminar flame speed values of methane/air mixtures diluted with actual combustion residuals are between those of N2 and H2O dilution, whereas the laminar burning velocities of methane flames diluted with CO2 are considerably slower. The effects of different combustion residuals on the burned gas Markstein length were not found to be significant. At the experimentally-investigated initial conditions, CHEMKIN analyses were performed with the GRI-Mech 3.0, San Diego, and USC Mech II mechanisms to inquire about the performances of the kinetic schemes. The GRI-Mech 3.0 results were the closest to the experimental data. This mechanism was also utilized to numerically quantify the dilution, thermal diffusion, and chemical effects of combustion residuals. The dilution effect was the leading effect in decreasing the laminar burning velocity, while the thermal diffusion effect had the smallest contribution. Nevertheless, the thermal diffusion effect changes the thermal and mass diffusivities, and, as a result, the Lewis number, making it a vital parameter for flame stability and stretch. As the thermodynamic properties and chemical reactivities of the combustion residuals vary with temperature, pressure, equivalence and dilution ratios, real combustion residuals cannot be accurately represented with only one or two of the main exhaust gases, as shown in the current study.

Nanosecond laser irradiation of soot particles: Insights on structure and optical properties

In spite of the advances in laser diagnostics in combustion, the effect of rapid laser irradiation on the physical/chemical properties of soot particles is far from being comprehensively understood. Optical properties, particle nanostructure and aggregate size of laser-irradiated soot particles are analyzed in this paper. Carbonaceous particles sampled from nitrogen-quenched diffusion flames of ethylene and methane are irradiated on-line by a 1064-nm short laser pulse. Wavelength-resolved extinction measurements in the visible range are used to follow their transformation by varying the laser energy density. A variation of the extinction coefficient of the irradiated particles compared to the extinction coefficient of the pristine ones is observed, especially for ethylene soot. The particle nanostructures are analyzed by Raman spectroscopy and the effect of laser irradiation on aggregate structure is evaluated by measuring particle size distributions. The results indicate that both soot nanostructure and optical properties are strongly dependent on the laser energy density when irradiated by a laser source. This is significant for ethylene soot, while for methane soot the degree of variation of such properties is less pronounced, at least in the investigated heating conditions.

Effect of Fuel Nozzle Geometry on Swirling Partially Premixed Methane Flames

Abstract This paper presents an experimental study of the effect of fuel nozzle geometry on swirling partially premixed methane flames, where the focus is put on the ensuing flowfield and its role on coherent structures' suppression. The burner consists of a central interchangeable fuel nozzle surrounded by a swirling co-airflow where both discharge into a short mixing tube. The nozzle geometry is classified into two groups, namely, single- and multi-orifice nozzles. The swirling motion of the co-airflow is produced using a radial-type swirl generator with a swirl number of 1.15. The flowfield characteristics and coherent structures are documented using particle image velocimetry (PIV). Flame front dynamics are captured using Mie scattering technique. Quantitative laser sheet (QLS) is used to qualitatively shed light on the mixing characteristics downstream of the mixing tube exit, and laser Doppler velocimetry (LDV) is used to extract the coherent structures' peak frequency from the power spectra. The results revealed that the fuel nozzle geometry significantly affects the mean flowfield, mean, and root-mean-square (RMS) of the flame front location, flame front asymmetry, and coherent structures' amplitude. Higher spread rate and faster decay caused by single-orifice nozzles inside the mixing tube result in divergent flames with higher degree of flame front asymmetry downstream of the mixing tube exit. On the other hand, multi-orifice nozzles mitigate coherent structures, enhance mixing, and hence, promote the most appropriate conditions for coherent structures' suppression.

Determination of temperature and water-concentration in fuel-rich oxy-fuel methane flames applying TDLAS

Combustion processes with pure oxygen (oxy-fuel) instead of air as oxidant are attractive for high temperature thermal or thermochemical and gasification processes. The absence of nitrogen in such applications leads to higher temperature and species concentrations, which can stabilize even extremely rich flames. Despite their benefits, there is lack of knowledge concerning the internal structure of rich oxy-fuel flames, which feature reactions with largely diverging chemical time scales, namely, the fast oxidation reactions and the slow endothermic formation of synthesis gas. In order to get a better insight, the scope of this study was to determine axial H2O- and temperature profiles of flat, fuel-rich methane-oxygen flames with equivalence ratios from 2.5 ≤ ϕ ≤ 2.9. A Heat-Flux-burner was used to stabilize quasi-adiabatic one-dimensional flames. The inlet temperature of the gas mixture was kept constant at TP = 300 K and the inlet velocity equal to the laminar burning velocity, which was determined in a preceding experimental study. The in-situ temperature and H2O-concentration measurements were performed using Tunable Diode Laser Absorption Spectroscopy (TDLAS). Laser measurements were carried out with three different diode lasers at center wavelengths λcw = 1344.5 nm, 1392.3 nm and 1853.5 nm, respectively, where multiple absorption peaks of the water molecule were investigated. Additionally, one-dimensional calculations with detailed chemistry were performed using the PREMIX code together with the GRI3.0 and CalTec2.3 mechanisms and compared with the experimental data. The results of the temperature measurements showed temperature peaks in the flame zone and a temperature decrease in the endothermic post flame zone, where synthesis gas is formed. The measured peak temperatures exceed the calculated equilibrium temperatures by approximately 100–400 K indicating super-adiabatic flame temperatures (SAFT). Both reaction mechanisms showed similar trends with respect to the decrease of the temperature in the post flame zone and were in line with the measured temperature. In contrast, the calculated decomposition of water in the post flame zone highly depends on the applied chemistry scheme. Here, the CalTech2.3 mechanism showed excellent performance in comparison to the experimental data for ϕ > 2.5. For ϕ = 2.5 the GRI3.0 performed better.

Soot primary particle sizing in a n-heptane doped methane/air laminar coflow diffusion flame by planar two-color TiRe-LII and TEM image analysis

Soot primary particle size distribution along the centerline of a laminar coflow methane/air diffusion flame doped with vaporized n-heptane at atmospheric pressure was studied using the planar two-color time-resolved laser-induced incandescence (TiRe-LII) technique and analysis of transmission electron microscope images. An improved thermophoretic probe sampling procedure was used to collect samples of soot particles. The LII signals captured at two wavelength bands in the visible are used to determine the soot effective temperature by two-color pyrometry. The methodology was first validated against the literature data obtained in a laminar coflow ethylene/air diffusion flame. The same methodology is then applied to the n-heptane doped methane flame along the flame centerline. The Sauter and geometric mean diameters of soot primary particles were obtained. Good agreement is found between the soot primary particle size distributions obtained by the two techniques.

On the Nature of the Synergetic Effect in Flames of Methane- and Formaldehyde-Air Mixtures

On the Nature of the Synergetic Effect in Flames of Methane- and Formaldehyde-Air Mixtures

Numerical simulation of the effect of diluents on NO<sub>x</sub> formation in methane and methyl formate fuels in counter flow diffusion flame

The increasing global demand for energy, the need to reduce green house gasses, and the depletion of fossil fuel resources have led for the need for renewable fuel sources such as biodiesel fuels. In the diesel engines, biodiesel fuels can also be used directly without comprehensive engine changes. Biodiesel relates to a diesel fuel that is based on vegetable oil or animal fat consisting of longchain of methyl, ethyl, or propyl esters. Methyl ester fuel burns more efficiently and has lower emissions of particulate matter, unburnt hydrocarbon, and carbon monoxide than fossil fuels. However, combustion of methyl ester fuel results in increased nitrogen oxides (NOx) emissions relative to fossil fuels. This study is concerned with characterizing the formation of NOx in the combustion of methyl formate under a counter diffusion flame. This was carried out in an Exhaust Gas Recirculation (EGR) system. Simulation of the process was done using Combustion Simulation Laboratory Software (COSILAB), and involved simulating the reactions of methyl formate fuel. The results obtained were compared to those of the methane/air diffusion flame, which is a well-characterized system. The extension validated the results obtained for the methyl formate/air diffusion flame. The reduction of NOx was found to be 26% and 14% in methane and methyl formate diffusion flame respectively from 0% to 29.5% of EGR. Increased EGR from 0% to 29.5% increased NOx reduction. Compared to methane/air diffusion flame, methyl formate/air diffusion flame with and without EGR had lower NOx emission. This was found to be true when examining the amount of other metrics viz. temperature, H, OH and N radicals associated with NOx. This showed that EGR system have an effect on NOx formation.

Extinction behavior of addition of PMMA powder into counterflow diffusion flame of methane and nitrogen and high temperature air

Extinction behavior of addition of PMMA powder into counterflow diffusion flame of methane and nitrogen and high temperature air

Effects of the cone angle on the stability of turbulent nonpremixed flames downstream of a conical bluff body

The effects of a stabilizer and the annular co-flow air speed on turbulent nonpremixed methane flames stabilized downstream of a conical bluff body were investigated. Four bluff body variants were designed by changing the outer diameter of a conically shaped object. The co-flow velocity was varied from zero to 7.4 m/s, while the fuel velocity was kept constant at 15 m/s. Radial distributions of temperature and velocity were measured in detail in the recirculation zone at vertical locations of 0.5D, 1D and 1.5D. Measurements also included the CO2, CO, NOx and O2 emissions at points downstream of the recirculation region. Flames were visualized under 20 different conditions, revealing various modes of combustion. The results evidenced that not only the co-flow velocity but also the bluff body diameter play important roles in the structure of the recirculation zone and, hence, the flame behavior.

Experimental and modeling study of nitric oxide formation in premixed methanol + air flames

Validation and further development of models for alcohol combustion requires accurate experimental data obtained under well-controlled conditions. To this end, measurements of nitric oxide, NO, mole fractions in premixed laminar methanol + air flames have been performed using saturated laser-induced fluorescence, LIF. The methanol flames have been stabilized at atmospheric pressure and initial gas temperature of 318 K at equivalence ratios ɸ = 0.7–1.5 using the heat flux method that allows for simultaneous determination of their laminar burning velocity. The LIF signal is converted into NO mole fraction via calibration measurements, which have been performed in flames of methane, methanol and syngas seeded with known amounts of NO. The experimental approach is verified by the measurements of NO mole fractions in the post flame zone of methane flames, investigated in previous studies at similar conditions. Data on the NO formation together with burning velocities for methanol and methane obtained under adiabatic flame conditions provide highly valuable input for model validation. They have been compared with predictions of six different chemical kinetic mechanisms. Summarizing the behavior of all models tested with respect to burning velocities and NO formation in flames of methane and methanol, the mechanism of Glarborg et al. (2018) and the San Diego mechanism (2019) demonstrate uniformly satisfactory performance.

Comparison of the Numerical Models for the Temperature Distributions of Non-Premixed Swirling Methane Flame

This study aimed to investigate the numerical modelling parameters that are in good agreement with experimental data for the temperature distribution of a non-premixed swirling methane flame. All numerical calculations have been performed with FLUENT, a computational fluid dynamics code. P-1 radiation model has been chosen for all numerical calculations. In addition, the swirl number has been taken 0.4 value to validate the results with respect to reference experimental data. All comparisons have been performed in axial and radial temperature distributions according to experimental data. Firstly, the number of swirl has been defined as a user-defined function. Thus, the effect of defining user-defined functions has been examined in the swirl number. Secondly, the model constant (A) of the eddy dissipation combustion model has been investigated to determine suitable value. After that, the eddy dissipation and PDF mixture fraction combustion models have been compared with each other. Finally, k-ε standard, realizable and RNG models have been analyzed to determine the proper turbulence model. The results showed that to define the swirl number as a user-defined function in the comparison tests has not been an important effect to obtain good agreement with the experimental temperature distribution data. It has been found that the value of one for the Eddy dissipation model constant is suitable for this model. It has also been found that the experimental results in both combustion models give approximate results, but the PDF model is particularly better at axial temperature distribution. Moreover, it has been seen that the k-ε realizable turbulence model is more suitable for this model.

Chemical effects of hydrogen addition on soot formation in counterflow diffusion flames: Dependence on fuel type and oxidizer composition

We experimentally studied and kinetically modeled the effects of hydrogen addition on soot formation in methane and ethylene counterflow diffusion flames (CDFs). To isolate the chemical effects of hydrogen in such flames, we also ran a set of experiments on flames of the same base fuels but with the addition of helium. Specifically, we measured the soot volume fractions of the flames using the planar laser-induced incandescence technique. We simulated detailed sooting structures by coupling the gas-phase chemistry with the polycyclic aromatic hydrocarbon (PAH)-based soot model, using a sectional method to resolve the soot particle dynamics. Our experimental and numerical results show that hydrogen chemically inhibits soot formation in ethylene CDFs. While in methane flames, it is interesting to observe that the difference in soot production between the hydrogen- and helium-doped cases became much smaller when the oxygen concentration in the oxidizer stream (XO) was reduced. This suggests that for methane CDFs the chemical soot-inhibiting effects of hydrogen was highly dependent on oxidizer composition (i.e., XO). Explanations are provided through detailed kinetic analysis concerning the effects of hydrogen addition on the growth of PAH, soot inception, and soot surface growth processes. Our results suggest that hydrogen's chemical role in soot formation not only depends on fuel type (ethylene or methane), it also may be sensitive to oxidizer composition.

Flame interactions in a stratified swirl burner: Flame stabilization, combustion instabilities and beating oscillations

The present article investigates the interactions between the pilot and main flames in a novel stratified swirl burner using both experimental and numerical methods. Experiments are conducted in a test rig operating at atmospheric conditions. The system is equipped with the BASIS (Beihang Axial Swirler Independently-Stratified) burner fuelled with premixed methane-air mixtures. To illustrate the interactions between the pilot and main flames, three operating modes are studied, where the burner works with: (i) only the pilot flame, (ii) only the main flame, and (iii) the stratified flame (with both the pilot and main flames). We found that: (1) in the pilot flame mode, the flame changes from V-shape to M-shape when the main stage is switched from closed to supplying a pure air stream. Strong oscillations in the M-shape flame are found due to the dilution of the main air to the pilot methane flame. (2) In the main flame mode, the main flame is lifted off from the burner if the pilot stage is supplied with air. The temperature of the primary recirculation zone drops substantially and the unsteady heat release is intensified. (3) In the stratified flame mode, unique beating oscillations exhibiting dual closely-spaced frequencies in the pressure spectrum is found. This is observed within over narrow window of equivalence ratio combinations between the pilot and main stages. Detailed analysis of the experimental data shows that flame dynamics and thermoacoustic couplings at these two frequencies are similar to those of the unstable pilot flame and the attached main flame cases, respectively. Large Eddy Simulations (LESs) are carried out with OpenFOAM to understand the mechanisms of the time-averaged flame shapes in different operating modes. Finally, a simple acoustic analysis is proposed to understand the acoustic mode nature of the beating oscillations.

Quantitative measurement of density fluctuations with a full-field laser interferometric vibrometer

Modern, lean and premixed gas turbine combustion concepts for low NOx emissions are prone to combustion instabilities. In a previous work it was shown that laser interferometric vibrometry (LIV) can be used to record global as well as local heat release fluctuations in swirl-stabilized premixed methane flames quantitatively, if other effects influencing density are small. In this work a newly developed camera-based full-field LIV system (CLIV) was applied to a lean, confined, premixed and swirl-stabilized methane flame under atmospheric conditions. Instead of time-consuming pointwise scanning of the flame, CLIV records full-field line-of-sight density fluctuations with high spatio-temporal resolution. With a recording rate of 200 kHz, CLIV enables the visualization of highly unsteady processes in fluid dynamics and combustion research. As an example for an unsteady process, the propagation of the flame front through a lean, premixed gas volume is visualized during an ignition process. A discussion of algorithms and assumptions necessary to calculate heat release oscillations from density oscillations is presented and applied to phase-averaged data recorded with CLIV for this type of flame. As reference, OH* chemiluminescence data were recorded simultaneously. While density gradients travelling with the flow are recorded by LIV and CLIV, chemiluminescence imaging will show nothing in the absence of chemical reaction.Graphic abstracta Time-averaged density gradient within the combustor in lateral direction. b Density fluctuations along line-of-sight 7 ms after ignition. c Phase-averaged and local heat release fluctuations at 225 Hz perturbation frequency

Effects of annular N2/O2 and CO2/O2 jets on combustion instabilities and NOx emissions in lean-premixed methane flames

Experiments on the effects of annular N2/O2 and CO2/O2 jets on combustion instabilities and NOx emissions in lean-premixed methane flames were conducted. Two variables were investigated to validate the effectiveness of suppressing combustion instabilities and NOx emissions synchronously—the flow rate and the volume fraction of O2. Results indicate that the amplitude-damped ratio of combustion instability can reach 79.53% under CO2/O2 injection, sound pressure reduced from 30.3 Pa to 6 Pa. Damped ratio of NOx emissions achieve 45% under the case of CO2/O2 injection, NOx emission reduced from 22.5 ppm to 12 ppm, but the N2/O2 injection case cannot significantly reduce NOx emissions. Mode shifting of flame heat release rate is observed during the process of annular injection, the amplitude of flame heat release rate increases to two times than that of the uncontrolled flames during the N2/O2 injection case, but the amplitude maintains a relatively stable level in the case of CO2/O2 injection, under both N2/O2 and CO2/O2 jets, oscillation frequency of flame heat release rate jumps from 265.5 Hz to approximately 125 Hz. The CO2/O2 jets lead to a more uniform temperature field than the N2/O2 jets, thus contribute to lower NOx emissions. The application of CO2/O2 injection improves combustion velocity and provides better mixing, the flame length becomes shorter and compact. This study realized the reduction of combustion instabilities and NOx emissions simultaneously, which could be conducive to the prevention of combustion instabilities or pollutant discharge in industrial gas turbine burners.

An updated short chemical‐kinetic nitrogen mechanism for carbon‐free combustion applications

Chemical-kinetic combustion mechanisms for hydrogen-oxygen-nitrogen systems, motivated originally by concerns about NOx emissions during hydrogen burning, have recently acquired renewed interest as a result of the possibility of employing ammonia-hydrogen mixtures in gas turbines and reciprocating engines as drop-in fuel to replace the use of natural gas. Specifically, this is of relevance to the implementation of engineering approaches for economical power generation with carbon sequestration or to large-scale energy-storage schemes, based on hydrogen or efficient hydrogen carriers such as ammonia. Because computational investigations are facilitated by short mechanisms (since the use of large mechanisms is often prohibitively expensive in reactive flow simulations), in response to the original concerns, a short nitrogen mechanism was developed in San Diego in the 1990s (not updated since 2004), without consideration of ammonia combustion. In view of the renewed interest in this topic, that mechanism has now been expanded to encompass 60 elementary steps among 19 reactive chemical species, including ammonia burning and NOx production, as reported herein, greatly improving predictions. With particular attention to high reactant temperatures and high-pressure conditions, relevant to industrial applications, it is shown that the present short mechanism retains satisfactory accuracy, exhibiting deviations that in most cases are within acceptable bounds (±20%). The revisions maintain the shortness of the original mechanism, adding only one more reactive species and six more elementary steps (while updating values of rate parameters of nine other steps, on the basis of newly available information). In addition, the short mechanism is applied herein to the analysis of fundamental combustion properties of ammonia/hydrogen/nitrogen-air laminar premixed flames, at unstrained and strained conditions, for comparison with methane-air flames as a reference gas-turbine fuel. It is found by comparing carbon-free and hydrocarbon laminar flames that these reactive mixtures, even if characterized by nearly identical adiabatic flame temperature and laminar flame speeds, nevertheless exhibit substantially different resistance to strain, with the ammonia/hydrogen flames exceeding the strain limit of methane flames by a factor of 5.

A physics-based approach to modeling real-fuel combustion chemistry – V. NOx formation from a typical Jet A

Real transportation fuels are complex mixtures of a variety of hydrocarbon components. Predicting NOx formation in practical combustors burning real fuels is usually made with the assumption that the NOx submodels developed and tested for small hydrocarbon combustion are applicable to mixtures of large hydrocarbons as found in real fuels. Additionally, NOx data are scarce for flames of real fuels. The aims of the current study are (i) to provide reliable NOx data in flames of a typical jet fuel, and (ii) to test our capability to predict these data by combining a recently proposed HyChem reaction model of jet A combustion (Xu et al., 2018) with the NOx submodel of Glarborg (2018). Specifically, NOx concentrations were measured in stretch-stabilized premixed flames of methane and Jet A (POSF10325) from fuel lean to rich conditions and of ethylene at a fuel-rich equivalence ratio. This range of stoichiometries allows both thermal NO and prompt NO pathways to be tested. The results show reasonably good agreement between the experimental data and model predictions for all flames tested, although the model appears to underpredict NOx concentrations in the Jet A flames under fuel rich conditions. Sensitivity analyses were conducted to illustrate the influence of the reaction pathways and flame boundary conditions on NOx predictions. The analyses also suggest that additional prompt NO reaction pathways may play a role in flames of large hydrocarbons.

Layer-by-layer modified low density cellulose fiber networks: A sustainable and fireproof alternative to petroleum based foams

Wood-based cellulose fibers were used to prepare porous, low density and wet-stable fiber networks (FN). Multilayer coatings consisting of chitosan (CH), sodium hexametaphosphate (SHMP) and inorganic nanoparticles comprising of either sodium montmorillonite (MMT), sepiolite (SEP) or colloidal silica (SNP) were deposited by the layer-by-layer (LbL) technique onto FNs in an effort to impart flame-retardancy. A simulated fire scenario measured by cone calorimetry showed that five quadlayers (QL) of CH/SHMP/CH/MMT, CH/SHMP/CH/SEP and CH/SHMP/CH/SNP can produce significant reduction in peak heat release rate (pkHRR). In detail, the coating containing SEP showed the largest reduction of the pkHRR by 47% relative to the uncoated FN. MMT and SEP coated FNs were also able to self-extinguish fire and to retain their shapes after direct exposure to a methane flame. This study hence shows that the LbL assembly is a highly effective way to impart flame-retardant properties to this new type of porous FN.