Pilot Flame Research Articles

Effects of hydrogen enrichment on the performance and emission characteristics of a diesel engine with the addition of Syzygium cumini (Jamun) biodiesel

ABSTRACT Biofuel made from Syzygium cumini, often known as Jamun, has the potential to be a low-cost, sustainable, and emission-free alternative. In this work, we experimentally explore the performance of a compression ignition (CI) engine that burns a blend of hydrogen and biodiesel. Hydrogen is pumped into the air intake manifold by means of a hydrogen gaseous supplement that, when exposed to atmospheric conditions, co-combusts with a pilot flame ignited by Jamun oil. To investigate the impact of hydrogen supplementation on performance and exhaust emission, a variety of hydrogen–Jamun fuel mixture proportions are provided to the engine. The research demonstrates that adding hydrogen improves the thermal efficiency (5%) of diesel engines whereas lowering specific energy fuel consumption (4%) at fixed Jamun flow rates. The gas emission data demonstrates that when hydrogen (HC) emission (12%) supplements decreases, NOx emission (10%) increases somewhat but opacity (8%) increases significantly. The experiment demonstrates that hydrogen and Jamun duel fuel in compression ignition engines burn smoothly.

Laser absorption correction for hydroxyl planar laser induced fluorescence measurements in a centrally staged combustor at elevated pressures

Planar laser-induced fluorescence (PLIF) is a crucial spectroscopic technique for measuring minor species [e.g., hydroxyl (OH), methylene (CH), and nitric oxide (NO) radicals] in combustion research, owing to its non-intrusive nature and high sensitivity. However, laser energy attenuation due to absorption poses significant challenges to its application under high-pressure conditions, which may cause asymmetric image intensity distribution along the light propagation direction. An absorption correction method for OH PLIF based on the concept of maximum number density is proposed in the present study. This method offers several key advantages, including simplicity, high accuracy, and versatility, allowing for correcting both time-averaged and instantaneous OH PLIF images. OH PLIF data obtained from a centrally staged combustor at elevated pressures (i.e., 0.3, 0.6, and 1.0 MPa) are utilized to validate the method. Correction for the time-averaged PLIF images achieves a much more symmetric distribution of OH, revealing the overall flame structures that would not have been completely visualized from the original images. The fronts of the pilot and main stage flames have also been recovered from the corrected instantaneous images. This correction algorithm provides an effective way of enhancing data quality for high-cost OH PLIF measurements at pressurized conditions.

Soot and Flame Structures in Turbulent Partially Premixed Jet Flames of Pre-Evaporated Diesel Surrogates with Admixture of OMEn

In this study, the soot formation and oxidation processes in different turbulent, pre-evaporated and partially premixed diesel surrogate flames are experimentally investigated. For this purpose, a piloted jet flame surrounded by an air co-flow is used. Starting from a defined diesel surrogate mixture, different fuel blends with increasing blending ratios of poly(oxymethylene) dimethyl ether (OME) are studied. The Reynolds number, equivalence ratio, and vaporization temperature are kept constant to ensure the comparability of the different fuel mixtures. The effects of OME addition on flame structures, soot precursors, and soot are investigated, showing soot reduction when OME is added to the diesel surrogate. Using chemiluminescence images of C2 radicals (line of sight) and subsequent Abel-inversion, flame lengths and global flame structure are analyzed. The flame structure is visualized by means of planar laser-induced fluorescence (PLIF) of hydroxyl radicals (OH). The spatial distribution of soot precursors, such as polycyclic aromatic hydrocarbons (PAHs), is simultaneously measured by PLIF using the same excitation wavelength. In particular, aromatic compounds with several benzene rings (e.g., naphthalene or pyrene), which are known to be actively involved in soot formation and growth, have been visualized. Spatially distributed soot particles are detected by using laser-induced incandescence (LII), which allows us to study the onset of soot clouds and its structures qualitatively. Evident soot formation is observed in the pure diesel surrogate flame, whereas a significant soot reduction with changing PAH and soot structures can be identified with increasing OME addition.

Temperature Field Measurements in Swirl Spray Flames Using Two-Line Planar Laser Induced Fluorescence Thermometry

Abstract This paper investigates the temperature fields in a centrally staged swirl spray combustor using two-line OH planar laser induced fluorescence (PLIF) thermometry at elevated inlet pressures and temperatures up to 0.62 MPa and 650 K. The pilot and main stages of the combustor were supplied with RP-3 kerosene. OH radicals were excited using the Q1(5) and Q1(14) transitions within the A2Σ←X2Π (1,0) band. Two laser excitation systems were operated simultaneously, where the two beams were spatially combined and separated by a small interval in time. The PLIF signals excited at the two wavelengths were captured by two identical sets of imaging system. The calibration coefficient needed for quantitative conversion from fluorescence ratio to temperature was determined based on results from independent coherent anti-Stokes Raman scattering (CARS) measurements. A joint threshold mask was developed to remove the noise and weak signals in the raw PLIF images. The high temperature zones in the temperature field were then obtained, and the pilot and main stage flames were identified. In addition, the radial position of the pilot flame showed marked variations at a nominally fixed condition. By extracting the radial profiles, a consistency between the peaks of PLIF intensity and temperature was found, suggesting that PLIF images could be a qualitative substitute for the high temperature zones in the temperature fields of these swirl spray flames. This study demonstrates the feasibility of temperature field measurements using two-line OH PLIF in aero-engine model combustors.

Fuel Temperature Effects on Combustion Stability of a High-Pressure Liquid-Fueled Swirl Flame

The influence of fuel temperature on combustion instabilities is investigated in a liquid-fueled, piloted swirl flame at 1.0 MPa. Fuels used for this study include Jet A and a Fischer–Tropsch-based synthetic paraffinic fuel (Shell GTL GS190). Simultaneous OH* chemiluminescence, particle image velocimetry, and Mie scattering measurements are performed in an optically accessible combustion chamber at 10 kHz for fuel temperatures ranging from 294 to 525 K. At ambient fuel temperature, a self-excited longitudinal instability is observed at 825 Hz. A higher instability amplitude is observed for Jet A compared to GS190 at all fuel temperatures. Analysis of the chemiluminescence images shows axial flame fluctuations at the instability frequency that are coupled to oscillations in fuel droplet consumption. Lower fuel temperatures lead to unburnt fuel accumulation in low-velocity regions of the flame, and consumption during the acoustic compression wave arrival results in high heat release magnitude that amplifies acoustic perturbations. Spatial correlations of the axial velocity and heat release fluctuation highlight the flame shear layers as predominant regions driving the global dynamics. Increased fuel temperature results in higher droplet evaporation rates in these regions, which promotes more uniform fuel deposition and subsequent burning over the thermoacoustic cycle, attenuating the instability.

A LES study on the instantaneous H2 jet-ignited combustion characteristics of H2/NH3 mixtures

This paper presents a Large Eddy Simulation (LES) study investigating jet flame ignition characteristics to achieve stable ammonia combustion for novel applications in gaseous ammonia/hydrogen-fueled engines with an active prechamber. The study investigated three cases with initial global equivalence ratios of 0.6, 0.8, and 1.0. Two main ignition modes were proposed, and five stages of coupled flame propagation processes were identified. The oscillation of supersonic hydrogen jet flame was investigated. The modes of flame-vortex interaction including vortex ring formation, along with the mechanism of highly reactive zone formation, were proposed. The effects of reactivity and turbulence transition on piloted ammonia flame were investigated to attain stable ammonia combustion and achieve a high heat release rate. The results showed that oscillations in the jet flame were strengthened at low global equivalence ratios with high hydrogen mass ratios. Enhancing propagation of initial and secondary vortex rings broadened highly reactive zones. Vorticity dissipated more rapidly at low equivalence ratios, leading to a stratified structure and enhanced piloted spherical flame. The Unsteady Flamelet Ignition Prediction (UFIP) sub-model of combustion was verified for the piloted ammonia flame, enabling a more comprehensive discussion of flame propagation tendencies.

Implementation of the P1 Radiation Model in a Velocity-Turbulent Frequency-Composition Joint PDF Method

ABSTRACT This research employs a more detailed radiation treatment to improve the accuracy of the velocity-turbulent frequency-composition joint probability density function (PDF) methods in numerical solution of the turbulent non-premixed flames. The radiation heat transfer in the traditional velocity-frequency-composition joint PDF methods has been disregarded or treated simply using an emission-only radiation model, even though radiation is important in the combustion systems. In the present PDF method, radiation is modeled using the P1-approximation and the radiative properties are calculated by the weighted-sum-of-gray-gases (WSGG) model. The results of present method are first validated by solving a laboratory turbulent piloted jet flame and comparing them with the measured data. Then, two constructed large-scale flames are modeled and simulated. Results reveal that reabsorption of emitted radiation increases from 2.98% in a laboratory-scale flame to 56.8% in the scaled-up flame and has a strong effect on the temperature distribution in the scaled-up flame. It is shown that reabsorption of emitted radiation increases the peak temperature on the flame axis by 119 degrees. Furthermore, radiation becomes more significant with the increase of the flame scales, so that the radiation fraction increases from 4.15% in the small-scale flame to 16.6% in the large-scale flame.

Smoke Suppression Properties of Fe2O3 on Intumescent Fire-Retardant Coatings of Styrene–Acrylic Emulsion

The intumescent flame-retardant coatings were prepared using ammonium polyphosphate (APP), pentaerythritol (PER), melamine (MEL), styrene–acrylic emulsion, and iron oxide yellow (FeOOH) as the base material. A cone calorimeter (CCT), smoke density meter (SDA), and scanning electron microscope (SEM) were employed to investigate the smoke suppression and flame retardancy of FeOOH in intumescent fire-retardant coatings. The thermal degradation performance of intumescent fireproofing coatings with varying FeOOH content was investigated through thermogravimetric analysis (TGA). The structure of the carbon slag in the CCT test was analyzed using a scanning electron microscope (SEM). The results of the cone calorimeter (CCT) experiments demonstrated that FeOOH significantly reduced the heat release rate (HRR), total heat release rate (THR), smoke production rate (SPR), and total smoke release rate (TSR) of the coating, while simultaneously increasing the carbon residue rate of the coating. The smoke density analysis (SDA) results demonstrate that adding FeOOH can effectively reduce smoke generation, regardless of whether a pilot flame is used. TGA results demonstrate that FeOOH can enhance the weight of coke residue at elevated temperatures. SEM results indicate that incorporating FeOOH resulted in a more compact coke residue. According to these findings, among all the samples, those containing 2 wt% FeOOH showed low levels of HRR, THR, SPR, and TSR and high levels of SOD, which proves that FeOOH can be used as a smoke inhibitor in flame-retardant coatings.

Investigation of the dynamic interaction mechanism of split injections during the ignition process under diesel engine-like cold- and hot-start conditions

In a range of operating conditions with variable injection parameters, interactions among split sprays present uncertainties across both temporal and spatial dimensions. Understanding these dynamic interactions is crucial for optimizing injection strategies to improve both the performance and environmental adaptability of diesel engines. In this study, optical diagnostics and numerical simulations were conducted to explore the interaction mechanisms between split injections and their impact on the ignition process. Engine-like cold and hot-start operating conditions were configured, and four injection strategies, including a single injection, were examined. The findings reveal that ambient temperature influences split spray interactions by altering their ignition characteristics, while injection dwell time modifies these interactions by changing the combustion spatial and temporal phase between split sprays. Compared to a single injection, split injection promotes the ignition and combustion of the main spray such as shortening ignition delay, reducing ignition location, and increasing flame area, but this promoting effect weakens under hot-start conditions. When the main spray chases the pilot spray before ignition, it increases the local concentration and reduces the temperature upstream of the pilot spray plume. However, since the effect front fails to reach the expected ignition region before the pilot ignition occurs, the ignition of the pilot fuel pocket remains unaffected. Under cold-start conditions, the main ignition delay shows a non-monotonic trend, reaching its minimum at an injection dwell of 900 μs, where the pilot ignition provides the main spray with elevated local temperatures and an increased hydroxyl mass fraction. Under hot-start conditions, the temporal overlap of ignition in split sprays is enhanced, yet spatial interaction weakens. Despite varying degrees of pilot flame decay before the main spray ignites with increasing injection dwells, the thermal radiation emanating from their combustion elevates the local temperature in the interaction zone beyond 1200 K. Consequently, upon catching up with the pilot injection, the main spray mixture rapidly ignites through the high-temperature reaction pathway, rendering the ignition delay insensitive with injection dwells.

Performance study of a central reentrant step pilot-flameholder in a dual-mode combustor

The augmented/ramjet combustion chambers are characterized by wide operating ranges, large flow state variations, and harsh operating conditions. The reliable ignition of these chambers urgently needs to be achieved. To improve the pilot ignition and blowout performance based on the centerbody in augmented/ramjet combustion chambers, a reentrant step flameholder is proposed on the basis of a conventional backward step. In this paper, the flow characteristics, ignition and blowout boundary under the non-premixed inflow, dynamic ignition process and flame stabilization mechanism of the reentrant step flame holder are investigated by using an experimental method with numerical simulation. The results show that the reentrant step flame holder exhibits better ignition and blowout performance than the conventional step flame holder without increasing the flow resistance. The ignition and blowout equivalence ratios of the reentrant step flame holder decrease by 22.86 % and 24.34 %, respectively, compared with those of the conventional step flame holder. The radial reentrant expansion is more effective than the axial reentrant expansion. Analyzing different reentrant structures shows that radial expansion can shorten the ignition delay time and improve the time-averaged integral flame intensity; axial expansion can improve the time-averaged integral flame intensity and reduce the flame pulsation rate; and the structure Da30Dr30 (the conventional step structure expands axially and radially by 30 mm simultaneously within the centerbody.) whose pilot flames are all stabilized in front of the reentrant step flame holder under different incoming flow conditions, exhibits the best ignition and blowout performances.

Experimental investigations on acoustic-velocity-flame dynamic characteristics of a stratified burner

To reveal the influence of interaction between pilot and main flames on flow and thermo-acoustic instability characteristics, high-frequency measurement devices such as High-Frequency Particle Image Velocimetry (HFPIV), high-speed camera, pressure sensors, and photomultiplier tube were applied to study the acoustic-velocity-flame dynamic characteristics of the stratified burner under ambient temperature and pressure. Results show that the pilot swirling flow significantly influences the acoustic-velocity-flame dynamic characteristics of the stratified burner. When the pilot and main stage are operated with a swirling air jet and swirling flame, the main recirculation zone disappears, the thermo-acoustic instability is strengthened and the frequency of thermo-acoustic instability is locked with the large-scale vortex shedding frequency. When the pilot stage is converted into a swirling flame, the main recirculation zone re-appears down stream of the nozzle outlet, and the high-temperature burned gas is rolled back to improve the combustion stability of the swirling flame. However, in this case, the interaction between the pilot and main flames makes the thermo-acoustic instability frequency not well consistent with large-scale vortex shedding frequency. The interaction between the main stage and pilot stage flames leads to the increase of the flame angle of the main stage. The heat release fluctuation at the flame interaction region is the most intense, and the large-scale vortex in the outer shear layer of the main stage also causes the flame to produce severe oscillation.

Polytetrafluoroethylene (PTFE) burn characteristics and toxicant formation in an oxidizer cross-flow via laser absorption tomography

A two-dimensional solid-fuel combustion experiment for fire-resistant polymers under forced convective cross-flow was developed to assess burn characteristics and toxicant formation using advanced laser absorption diagnostics that enable in situ species and temperature measurements near the fuel surface. The method was used to examine the thermochemical flow-field structure near the surface of polytetrafluoroethylene (PTFE) exposed to a well-defined solid-fuel pilot flame burning polymethyl methacrylate (PMMA). Infrared diode and quantum cascade lasers were used to probe rovibrational absorption transitions of hydrogen fluoride (HF) and carbon monoxide (CO), respectively, at the exit plane of a heterogeneous cylindrical fuel grain from which temperature and mole fraction could be inferred. A laser absorption tomography (LAT) technique with a Tikhonov-regularized Abel inversion was applied to reconstruct radially-resolved profiles in the axisymmetric reacting flow which, when compiled across a range of fuel lengths, provided a two-dimensional image of the near-surface reaction layer. Thermochemical data and reaction rate parameters from existing fluorocarbon chemistry models were used to generate high-temperature simulations of product species concentrations and temperature as a function of oxidizer-to-fuel ratio to elucidate observed trends and identify key reactions relevant to the novel dataset. The geometry and scale of the composite fuel experiments is intended to be tractable for reactive multi-physics models, enabling quantitative comparison of combustion characteristics and ultimately improved predictive capability of toxicant quantities resulting from fluoropolymer combustion in fire environments.

A Comparative Study between FGM and SLF Approach for Turbulent Piloted Flame of Methane

This study validates the RANS simulation results by comparing them with experimental data. Numerical simulations were performed for a piloted methane-air jet flame in an axisymmetric burner. It is noteworthy that RANS simulations have been performed using a Non-premixed model with Steady Laminar Flamelet (SLF) and a partially premixed model with Flamelet Generated Manifold (FGM) of the Ansys-Fluent solver are used to express the chemistry-turbulence interaction, to provide an initial solution to the simulation performed by the Pdf transported, joint two kinetic mechanisms for oxidation of methane, detailed GRI-Mech 3.0 mechanism (53 species, 325 reactions), and CH4-Skeletal mechanism (16 species, 41-step). The case test consists of a rich premixed flame (Sandia Flame D). A comparison between the results of the obtained simulations and experimental data shows good agreement, in particular in the context of RANS/FGM with both mechanisms (GRI 3.0 and CH4-Skel).

Impact of pilot flame and hydrogen enrichment on turbulent methane/hydrogen/air swirling premixed flames in a model gas turbine combustor

This work investigates the impact of pilot flame and fuel composition on the structures and stabilization of swirling turbulent premixed methane/hydrogen/air flames in a lab-scale gas turbine model combustor. Simultaneous measurements of the velocity field and OH radicals distribution in the combustor were conducted using particle imaging velocimetry (PIV) and planar laser-induced fluorescence (PLIF) methods, respectively. Flames under stable and close to lean blow-off (LBO) conditions were studied for two fuel mixtures, with a hydrogen mole ratio of 0 and 50 % in the hydrogen/methane mixture, respectively. The studied flames were at a constant Reynolds number of 20,000 with different equivalence ratios. Two pilot-to-global fuel ratios were investigated (2 % and 6 %) while keeping the pilot-to-global air ratio constant at 2 %. Data for non-piloted flames were also acquired for comparison. The pilot flames were shown to extend the operability range. The LBO equivalence ratio of the main flame decreased with increasing fuel mass flow rate in the pilot flames due to the increased amount of hot gases with high concentrations of OH radicals in the outer recirculation zone (ORZ), which significantly enhanced the stabilization of the main flame. The stable flame reaction zone was in the high-speed shear layer between the ORZ and the inner recirculation zone (IRZ). When approaching LBO, the reaction zone was pushed downstream to the IRZ and subsequently decreased the size of IRZ, indicating a strong flow/flame interaction. Hydrogen enrichment was shown to reduce the LBO equivalence ratio. When close to LBO, the OH radicals in the hydrogen-enriched flames were observed in isolated pockets due to differential diffusion, which enhanced resilience to LBO. The flame front curvature, mean progress variable, and flame surface density were calculated from the acquired OH-PLIF data to quantify the impact of fuel composition and pilot flames on the flame structures.

Multi-line OH-LIF for gas-phase temperature and concentration imaging in the SpraySyn burner

Gas-phase temperature and OH concentration images are measured in the SpraySyn nanoparticle-synthesis standard burner using multi-line OH laser-induced fluorescence (LIF) thermometry. In this burner, a spray flame fed by a combustible nanoparticle precursor solution is stabilized by a surrounding axisymmetric lean premixed laminar methane/oxygen pilot flame. For measuring OH rotational temperature, the laser is scanned across the 282.05–282.17 nm range and LIF excitation spectra are fitted for each image pixel by simulated spectra. Temperature maps are determined for the pilot flame and the ethanol spray flame with variable dispersion gas flow rates of oxygen used in the two-fluid nozzle. The addition of 2-EHA (2-ethylhexanoic acid) to the solution was found to increase the flame temperature. Laser attenuation across the flame was measured using simultaneous recordings of the fluorescence of uranine/water solution from two dye cuvettes illuminated with the laser sheet before and after the flame and the effect of attenuation was quantified. Absolute OH concentration distributions are determined by combining the LIF images, laser attenuation measurements, and derived temperature distributions. The temporal stability of the flame is investigated for various operating conditions by statistical evaluation of recorded instantaneous OH-LIF images.

On the subgrid dissipation concept for large eddy simulation of turbulent combustion

A new subgrid turbulent combustion model for LES is derived based on the eddy dissipation concept (EDC). To be consistent with the LES framework, the relationship between the subgrid quantities and the fine structure ones is built from the unresolved part of the energy cascade, hence the subgrid dissipation concept (SDC). The fine structure quantities are directly computed using the subgrid scale ones. Resolving local laminar flame structures is allowed if the grid resolution permits. The model is examined using premixed piloted jet flames and non-premixed swirl flame. Satisfactory predictions from the SDC model are obtained in the test cases, showing improvements with respect to the standard EDC model. The new SDC model is relatively insensitive to the grid resolution.

LES of premixed jet flames subjected to extreme turbulence using flamelet-generated manifolds: a comparison of unstrained and strained flamelets

Two piloted premixed CH 4 /air jet flames with extreme turbulence are modelled using the Flamelet-Generated Manifold (FGM) method in the context of Large Eddy Simulation (LES). Free-propagating and reactant-to-product laminar flames are adopted to build unstrained and strained chemical databases, respectively. Detailed comparison of the LES-FGM results using the unstrained/strained databases is conducted which is validated against the direct numerical simulation results. The results show that whether including straining effects in the database will not influence the modelling of temperature and major species (e.g. CH 4 , O 2 and CO 2 ), but using a strained database is essential for predictions of intermediate minor species (e.g. H 2 , CH 2 O, OH and CO). The main reason is that the major species and temperature are almost insensitive to the straining due to the supportive effects from the pilot flame, which also tentatively explains why the unstrained database can be employed to model these strong turbulent flames. In contrast, the intermediate minor species are more prone to the straining, so that using a strained database is crucial. The preferential diffusion effects on the species and temperature predictions are examined to be negligible. It is proposed that adding extra transport equations for these minor species also leads to satisfactory predictions if using an unstrained database, which helps to include the straining effects on the minor species. This study is expected to be significant in high-fidelity simulations of strong turbulent flames using flamelet-tabulated combustion models.

Development of a novel hydrogen-based burner concept for pilot-scale spray flame synthesis of nanoparticles

The development of a novel burner concept for the synthesis of nanoparticles in spray flames is described and the prototype is experimentally characterised. The burner was designed to enable the process to be scaled up while maintaining stable operation in terms of fluid mechanics and combustion kinetics. It utilises a hydrogen pilot flame that is stabilised by auto-ignition of the premixed gas. The pilot ignites a spray generated from a commercial two-fluid nozzle that uses air instead of oxygen as a dispersion gas. General operation characteristics are shown from measurements of the velocity fields and the OH* chemiluminescence of the flame. The burner shows reliable operation under various conditions and excellent scaling potential. The present study is focused on stable operating conditions and the scaling of the process, particle production with the burner is shown in another publication.

Effect of fuel temperature on the structure of a high-pressure liquid-fueled swirl flame

Experiments were conducted in a liquid-fueled, piloted swirl burner operating at high pressure (1.0 MPa and 2.0 MPa) to study the influence of fuel injection temperature on the coupled flow and combustion processes. Simultaneous 10 kHz stereoscopic particle image velocimetry and OH* chemiluminescence measurements were used to characterize the overall flow and flame structure over a range of equivalence ratios at three discrete fuel temperatures: 367, 486, and 577 K. The location of the pilot flame was found to be insensitive to the fuel temperature, while the main flame moved closer to the injector as the fuel temperature was increased. This was accompanied by an increase in the axial velocity in the region of the main flame and a downstream shift of the shear layer along the border of the central recirculation zone. Analysis of the mean velocity fields relative to the location of maximum OH* chemiluminescence intensity showed an increase in velocity normal to the mean flame position with higher fuel temperatures. This indicates the flame speed increases with fuel temperature, which, along with the changes to the fuel injection process, helps explain the observed changes to the flow and flame structure.

Large eddy simulation of iron(III) oxide nanoparticle synthesis in spray flames

The SpraySyn burner has been developed to investigate nanoparticle synthesis from spray flames by various diagnostic methods and simulations from research groups within the DFG (German Research Foundation) priority program SPP1980. We investigate the formation of iron oxide nanoparticles from iron nitrate dissolved in a mixture of ethanol and ethyl hexanoic acid. In the SpraySyn experiment, the nanoparticle precursor solution is injected and atomized via an air-blast nozzle, surrounded by a pilot flame. The solvent itself is combustible, such that the droplets evaporate at high heating rates in a highly reactive environment. We investigate the synthesis flame in large eddy simulations. The liquid droplets are described by Lagrangian particles, and gas-phase combustion is modeled by the flamelet-generated manifold approach with adaptations for particle inception. The nanoparticle dynamics are predicted by three models: a monodisperse model, a bimodal model, and a sectional model. The monodisperse and bimodal models account in terms of number-, surface-, and volume-concentration from inception, coagulation, and sintering processes, while the sectional model accounts for inception and coagulation and provides the particle size distribution. The comparison of nanoparticle sizes with the in-situ measurements shows that the bimodal model can be a suitable alternative approach to the computationally expensive sectional model.