Laser-induced Fluorescence Experiments Research Articles

Comprehending flame development and misfire at advanced engine conditions: Detailed experimental characterizations and machine learning-assisted kinetic analyses

Through comprehensive experimental and modeling efforts, this work unravels the underlying mechanisms governing flame development and misfire at advanced engine conditions that are representative of low-load and lean blow-out operations. Toward this, preliminary heat release, autoignition, and flame developing patterns are characterized, via a case study of n-heptane, at ultra-lean conditions in a well-controlled optical engine under various combustion modes including homogeneous charge compression ignition (HCCI), partially premixed combustion (PPC), and reactivity-controlled compression ignition (RCCI). Changes in preliminary heat release and flame developing patterns at three overall equivalence ratios (0.12, 0.18, and 0.24) are first characterized under the PPC mode. Flame development characteristics including flame areas and number of initial flame kernels at close-to-misfire conditions are further extracted and compared across the HCCI, RCCI, and three PPC modes, with two distinctive and one transition regimes identified. Further analyses indicate that sustainable flame development and misfire are largely controlled by the spatial distribution of local equivalence ratio (phi) and local temperature in the mixture, which dictate the initial flame kernel generation and the subsequent flame propagation through localized preliminary heat release and autoignition. Chemical kinetic modeling is also undertaken, using a recently updated gasoline chemistry model, in conjunction with a backpropagation neural network, where the predicted ignition delay map well captures the different regions of flame development. Further kinetic analysis and heat rate of production per reaction analysis corroborate the CH2O planar laser-induced fluorescence experiments and highlight the important chemical kinetics that govern the initial flame development patterns.

Liquid and aerated jets behind different pylon configurations in supersonic crossflow

Effects of different pylon configurations on the liquid and aerated jets injected in supersonic crossflow of Mach number 1.65 were investigated experimentally. Pylon configurations with different bottom curvatures at the trailing edge were explored. Two liquid jets with momentum flux ratio of 0.1 and 0.4, and two aerated jets with gas-to-liquid mass ratio of 2% and 4% were selected in the current study. Acetone and air were used as the secondary liquid jet and the aeration gas, respectively. For the atomization quality of the jet, the droplet velocity field was obtained using fluorescence-based particle image velocimetry. The high-speed shadowgraph and cross-sectional planar laser-induced fluorescence experiments were performed for the mixing characteristics, such as penetration height and spreading area. The high-speed images were also used for the dynamic mode decomposition, which revealed dominant structures and their associated frequencies. Curved pylons with 45°and 60°trailing edge curvatures produced higher droplet velocity distribution than the other cases for liquid and aerated jets, respectively. The penetration height of the liquid jet at low momentum flux ratio tends to traverse towards the wall downstream of the injection. Aeration substantially improves the penetration height for the same liquid flow rate due to the annular nature of the aerated jet with a gas-to-liquid mass ratio of 2%. Cross-sectional planar laser-induced fluorescence results revealed a considerable increase in the spreading of the jet for the aerated jets as compared with the low momentum flux ratio liquid jet. This was due to the higher shear layer interaction of the aerated jet than that of the liquid jet. The aerated jets produced 60% higher spreading area than the liquid jet with the same mass flow rate. The curved pylons exhibited at least 10% increment in the spreading area as compared to the standard pylon cases for all the liquid and aerated jets. Three distinct modes were observed in the DMD analysis. The convective mode was the typical first and second modes of all the cases. The shear layer flapping and shear-induced entrainment breakup modes have also been observed with frequencies around 5 kHz.

The relative efficiencies of the entrainment of mass, momentum and kinetic energy from a turbulent background

We derive expressions relating the entrainment fluxes of momentum and kinetic energy, relative to the mass flux entrained into a turbulent wake exposed to a turbulent background. These expressions contain correlations between the entrainment velocity and the turbulent fluctuations within the background. We perform high-resolution, simultaneous particle image velocimetry and planar laser-induced fluorescence experiments, and observe these correlations to be negligible in the far wake, such that momentum and kinetic energy are entrained into the wake with the same relative efficiency to mass as from an idealised, non-turbulent background. This is a useful result in the context of modelling, since the entrainment hypothesis (Turner, J. Fluid Mech., vol. 173, 1986, pp. 431–471) can still be used to model the entrainment of momentum and kinetic energy. Nevertheless, the entrainment rate of mass is shown to vary spatially, and with the specific nature of the background turbulence, so this in turn drives a spatial/background-turbulence-specific entrainment rate of momentum/kinetic energy. Contrastingly, in the near wake, whilst momentum is entrained from a turbulent background with the same relative efficiency to mass as for an idealised non-turbulent background, this is not the case for kinetic energy. Owing to the sum of multiple positive, small-valued correlations between the fluctuations in the background and the entrainment velocity, kinetic energy is entrained more efficiently than in the idealised case. This includes entrainment from a non-turbulent background, where small correlations are observed between the irrotational background fluctuations and the entrainment velocity. Evidence is also presented that the entrainment velocity scales with the Kolmogorov velocity scale when the background is turbulent.

Spatial evolution of the turbulent/turbulent interface geometry in a cylinder wake

This study aims to examine the spatial evolution of the geometrical features of the turbulent/turbulent interface (TTI) in a cylinder wake. The wake is exposed to various turbulent backgrounds in which the turbulence intensity and the integral length scale are varied independently, and comparisons to a turbulent/non-turbulent interface (TNTI) are drawn. The turbulent wake was marked with a high Schmidt number ( $Sc$ ) scalar, and a planar laser induced fluorescence experiment was carried out to capture the interface between the wake and the ambient flow from $x/d = 5$ to 40, where $x$ is the streamwise coordinate from the centre of the cylinder, and $d$ is the cylinder's diameter. It is found that the TTI generally spreads faster towards the ambient flow than the TNTI. A transition region of the interfaces’ spreading is found at $x/d \approx 15$ , after which the interfaces propagate at a slower rate than previously (upstream), and the mean interface positions of both the TNTI and TTI scale with the local wake half-width. The locations of both the TNTI and TTI have non-Gaussian probability density functions (PDFs) in the near wake because of the influence of the large-scale coherent motions present within the flow. Further downstream, after the large-scale coherent motions have dissipated, the TNTI position PDF does become Gaussian. For the first time, we explore the spatial variation of the ‘roughness’ of the TTI, quantified via the fractal dimension, from near field to far field. The length scale in the background flow has a profound effect on the TTI fractal dimension in the near wake, whilst the turbulence intensity becomes important only for the fractal dimension farther downstream.

Characterization of the intermolecular vibrational levels bound within the Ar + I2(E, v) potential energy surfaces

Two-color, two-photon laser-induced fluorescence experiments were performed to probe the intermolecular interactions within the Ar + I2(E, vE = 0–3) potential energy surfaces. Spectra were recorded using the lowest-energy T-shaped level and an excited intermolecular vibrational level with bending excitation within the Ar + I2(B, vB = 23) potential as intermediate levels to guide the spectral assignments. Progressions of intermolecular stretching and bending levels bound within the Ar + I2(E, vE) potentials were identified, and their vibrational frequencies were determined. The harmonic frequency and anharmonic constant for the bending vibrational mode were determined to be ωe(b) ∼ 34.8 cm−1 and ωeχe(b) ∼ 0.3 cm−1. The frequency and anharmonic constant for the stretching mode were found to be the same as reported previously [V.V. Baturo, et al. Chem. Phys. Lett. 647 (2016) 161], ωe(s) = 37.2(1.1) cm−1 and ωeχe(s) = 1.8(2) cm−1.

Mixing enhancement of ethylene secondary jet injected into supersonic cross-flow using curved pylon

Mixing of ethylene secondary jet injected behind a curved pylon in supersonic cross-flow at a Mach number of 1.65 has been studied numerically with experimental validation. For the validation of numerical results, Schlieren, wall pressure measurements, particle image velocimetry, and planar laser-induced fluorescence experiments were performed. Ethylene fuel was used for the simulation, and air was used as a substitute fuel in the experiments. In this study, the curved pylon with different curvatures has been studied at 3.5 bar and 7 bar secondary injection pressures. The results are compared with the standard pylon and conventional transverse injection cases. The results showed improvements in mixing parameters when curved pylons were used. Results indicated that complete mixing was achieved in pylon cases at a much shorter distance than in the transverse injection. The complete mixing distance for the pylon cases was observed around z/dj = 50 and z/dj = 80 for 3.5 bar and 7 bar injection cases, respectively. Even though the mixing efficiencies were similar for all the pylon cases, the flammable plume area and total pressure loss differed. Changes in the bottom curvature angle at the trailing edge of the pylon caused different streamwise vortex structures, which affected the flammable plume area. A considerable difference was found in the penetration height among pylons at 3.5 bar injection pressure, and the difference became minimal at 7 bar injection pressure. Penetration height was greatly affected by the interaction of the secondary jet with the low-pressure region and the momentum flux ratio of the secondary jet. At least a 1 % reduction in total pressure loss was found for curved pylon cases when compared with the standard pylon.

Effects of secondary impinging on flow features and mixing performance in T-T jet reactors

The improvement of mixing performance for the micro/mini impinging jet reactor is a pivotal and attractive topic in the chemical industry. In the present study, the Planar Laser-Induced Fluorescence (PLIF) experiment and numerical simulation on a novel T-T jet reactor that generated secondary impinging were carried out. In the T-T jet reactor, the influence of secondary impinging on various flow regimes at diverse Reynolds numbers was investigated in detail. The results show that, compared with the classical T jet reactor, the mixing of different flow regimes is intensified by the secondary impinging. The number and shape of the impingement planes of the segregated flow and vortex flow are changed. The steady engulfment flow generates more fluid filaments under the secondary impinging. The agglomerate created by the vortex-merging of unsteady engulfment flow is strengthened and the flow topology of the unsteady symmetric flow is modified. All the above indicates that the mixing performance is improved. In addition, the impact of the T-T gap ratio (κ = l/w, where l and w are the width of the T-T gap and the inlet channel, respectively) on flow characteristics and mixing performance in the T-T jet reactor was also considered. The configuration with the lower T-T gap ratio, i.e., κ = 0.2, presented a better global mixing performance than those with the larger T-T gap ratios, i.e., κ = 0.6 and 1.0.

Treating NOx emission of hydrogen fueled combustion engines by NOx storage and reduction catalysts: A transient kinetic study including PLIF measurements

NOx storage and reduction (NSR) catalysts are a well-known and broadly used technology to reduce NOx emissions from combustion engines, which may also be applied for hydrogen fueled engines in the future. In this study, Pt- and Pd-based NSR-catalysts were investigated in the absence and presence of water to understand how NO oxidation as well as the storage and reduction phases are influenced by the gaseous environment with H2 as a reductant. A planar channel configuration was chosen for conducting planar laser-induced fluorescence experiments during the storage phase in addition to steady-state oxidation measurements and transient lean/rich cycles in a packed bed reactor. The presence of steam significantly decreases the NO oxidation activity of both noble metal catalysts. The Pt/BaO/Al2O3 catalyst is more active during transient lean/rich cycles, however, it suffers an activity loss during repeated cycles, whereas the activity of the Pd/BaO/Al2O3 sample is slightly more stable in the wet gas feed over time. All experiments showed a strong correlation between the NO2 formation over the catalyst and its storage capability. The influence of water in the exhaust gas on the NSR-catalysts shows a strong temperature dependency on storage and reduction of NO for both catalysts containing Pt and Pd. The storage behavior is also strongly influenced by both the experimental configurations chosen revealing the significance of the interaction of intrinsic catalytic kinetics and mass transfer in the surrounding flow field.

On the physical nature of the turbulent/turbulent interface

The existence of a turbulent/turbulent interface (TTI) has recently been verified in the far wake of a circular cylinder exposed to free-stream turbulence (Kankanwadi & Buxton, J. Fluid Mech., vol. 905, 2020, p. A35). This study aims to understand the physics within the TTI. The wake boundary, approximately 40 diameters downstream of a circular cylinder subjected to grid-generated turbulence, was investigated through simultaneous cinematographic, stereoscopic particle image velocimetry and planar laser induced fluorescence experiments. With no grid placed upstream of the cylinder, the behaviour of the resultant interface, our closest approximation to a turbulent/non-turbulent interface, exactly matched what is observed in existing literature. When background turbulence is present, viscous action is no longer the only method by which enstrophy is transported to the background fluid, unlike for turbulent/non-turbulent interfaces. The presence of rotational fluid on both sides of the TTI allows the vorticity stretching term of the enstrophy budget equation to be the dominant actor in this process. The role of viscosity within a TTI is greatly diminished as the vorticity stretching term takes over responsibilities for enstrophy production. The turbulent strain rate normal to the TTI was found to be enhanced in the interfacial region. Decomposing the vorticity stretching term into components aligned with the three principal strain-rate directions, it was found that the term most aligned with the interface-normal direction contributed to the largest share of enstrophy production. This indicates that better ‘organised’ vorticity on the wake side of the interface yields the enstrophy amplification leading to the previously discovered enstrophy jump across the TTI by Kankanwadi & Buxton (J. Fluid Mech., vol. 905, 2020, p. A35).

Effects of an incoming vortex on the film cooling jet

In a high pressure turbine, film cooling is applied to protect the blades and endwalls from the high temperature main flow. The horseshoe and passage vortex near the endwall can significantly affect the film cooling performance and lead to a detrimental consequence for certain holes. In this study, large eddy simulations (LES) and laser-induced fluorescence (LIF) experiments were conducted to investigate the effects of the incoming vortex on the flow physics and cooling performance of a film cooling jet. Two cases with the incoming vortex passing from different sides of the cooling hole were compared with the baseline case with the uniform incoming flow. The time-averaged results showed that two cases with incoming vortex have more than three times variation in the film cooling effectiveness due to the downwash and upwash effects of the incoming vortex. The analysis based on the instantaneous flow field provides more insight into the flow physics and cooling mechanism. The instantaneous flow field showed that the incoming vortex changes the shape and the distributions of the coherent structures, which affects the mixing and surface area covered by the coolant and hence the cooling effectiveness. The norm of turbulent heat flux was found to better illustrate the mixing process between the main flow and the coolant due to the transportation and breakdown of the coherent structures. In addition, the cases with different vortex strengths were also studied to find the degree of improvement of film cooling effectiveness.

Atomic Transition Probabilities of Neutral Calcium*

Abstract The goals of this study are (1) to test the best theoretical transition probabilities for Ca i (a relatively light alkaline earth spectrum) from a modern ab initio calculation using configuration interaction plus many-body perturbation theory against the best modern experimental transition probabilities and (2) to produce as accurate and comprehensive a line list of Ca i transition probabilities as is currently possible based on this comparison. We report new Ca i radiative lifetime measurements from a laser-induced fluorescence experiment and new emission branching fraction measurements from a 0.5 m focal length grating spectrometer with a detector array. We combine these data for upper levels that have both a new lifetime and new branching fractions to report log(gf) values for two multiplets consisting of nine transitions. Detailed comparisons are made between theory and experiment, including the measurements reported herein and a selected set of previously published experimental transition probabilities. We find that modern theory compares favorably to experimental measurements in most instances where such data exist. A final list of 202 recommended transition probabilities is presented, which covers lines of Ca i with wavelengths ranging from 2200 to 10000 Å. These are mostly selected from theory but are augmented with high-quality experimental measurements from this work and from the literature. The recommended transition probabilities are used in a redetermination of the Ca abundance in the Sun and in the metal-poor star HD 84937.

Localization and quantification of radical production in cavitating flows with luminol chemiluminescent reactions

Hydrodynamic cavitation experiments in microfluidic systems have been performed with an aqueous solution of luminol as the working fluid. In order to identify where and how much reactive radical species are formed by the violent bubble collapse, the resulting chemiluminescent oxidation reaction of luminol was scrutinized downstream of a constriction in the microchannel. An original method was developed in order to map the intensity of chemiluminescence emitted from the micro-flow, allowing us to localize the region where radicals are produced. Time averaged void fraction measurements performed by laser induced fluorescence experiments were also used to determine the cavitation cloud position. The combination void fraction and chemiluminescence two-dimensional mapping demonstrated that the maximum chemiluminescent intensity area was found just downstream of the cavitation clouds. Furthermore, the radical yield can be obtained with our single photon counting technique. The maximum radical production rates of 1.2*107 OH/s and radical production per processed liquid volume of 2.15*1010 HO/l were observed. The proposed technique allows for two-dimensional characterisation of radical production in the microfluidic flow and could be a quick, non-intrusive way to optimise hydrodynamic cavitation reactor design and operating parameters, leading to enhancements in wastewater treatments and other process intensifications.

LIF diagnostics for selective and quantitative measurement of PAHs in laminar premixed flames

Laser-induced fluorescence (LIF) technique has been widely applied in PAH measurement in sooting flames, but it is still a big challenge to quantitatively identify the specific PAH species due to the complexities of spectral characteristics and calibration method. In this study, we aimed at developing a spectral-resolved LIF analytic model that can obtain PAH mole fractions in flames. A comprehensive LIF spectrum database in the wide temperature and concentration ranges was firstly established by the LIF experiments of gas-phase PAHs in an optical cell. Then, a spectral-resolved LIF analytic model was presented based on linear superposition regulation and an optimization fitting algorithm, and the LIF spectra of PAH components can be decomposed from the LIF spectra of the flame using this model. Finally, the integral fluorescence intensities of each PAH component were calibrated to their mole fractions by the calibration factors at corresponding temperatures. In this way, we can measure the mole fractions of several PAHs. Subsequently, the presented LIF method was applied to investigate the PAH formation characteristics at different flame temperatures. The experimental results showed that the mole fractions of each PAH except naphthalene decreased around 60% to 70% when the temperature increased from 1186 K to 1483 K, while the mole fraction of naphthalene kept nearly constant. The mole fractions simulated by a chemical kinetic model well reproduce the experimental results. According to the chemical kinetic analysis, C2H2 oxidation reaction was promoted and the C2H2-addition reactions were suppressed by increasing temperatures, which suppressed the PAH formation.

Laser-induced fluorescence and dispersed-fluorescence spectroscopy of the Ã2E-X̃2A1 transition of jet-cooled calcium methoxide (CaOCH3) radicals.

Laser-induced fluorescence (LIF) and dispersed fluorescence (DF) spectra of the Ã2E-X̃2A1 electronic transition of the calcium methoxide (CaOCH3) radical have been obtained under jet-cooled conditions. Complete active space self-consistent field and coupled-cluster calculations on the free radical were performed to aid the assignment of vibronic transitions observed in the LIF/DF spectra. In addition to dominant spectral features that are well reproduced by vibrational frequencies and Franck-Condon (FC) factors calculated ab initio, the FC matrix for the Ã2E-X̃2A1 electronic transition contains considerable off-diagonal elements that connect (i) the CaO-stretch (ν4) mode and non-CaO stretch modes and (ii) the asymmetric CaOC stretch (ν3) and the CaOC bending (ν8) modes. The Jahn-Teller and pseudo-Jahn-Teller interactions involving the Ã2E state as well as the spin-orbit interaction induce additional vibronic transitions that are not allowed under the Born-Oppenheimer approximation. Additionally, anharmonic vibrational terms in the ground state induce transitions that are forbidden in the harmonic-oscillator approximation. Spin-orbit splitting has been observed for several vibrational levels of the Ã2E state, and an essentially constant value was measured at all levels accessed in the LIF experiment. Implications of the present spectroscopic investigation to the proposed schemes of laser-cooling MOCH3 (M = alkaline earth metals) molecules and detection of time-reversal-symmetry-violating interactions are discussed.

Iron Contamination in High-Enthalpy Test Facilities: OH PLIF Imaging Considerations

Thermometry measurements were performed in a scramjet combustor using thermally-assisted laser-induced fluorescence. Experimental data were obtained through laser-induced fluorescence where a laser beam was focused into the combustor and the OH () transition at 283.55 nm was excited. Measurements in the 360 nm spectral region resulted in detection of a strong fluorescence line. Investigation of this phenomenon led to the conclusion that when the OH line is chosen for excitation, another line of a different species that lies very close to is also unintentionally excited. The second species has been identified as iron, Fe I. The assumption is that the erosion of the shock tunnel walls introduced iron in the flow that is excited with the laser when exciting OH. Thus, it is very important to ensure that this is avoided in future. Instead, another OH excitation line should be used for OH excitation line in planar laser-induced fluorescence (PLIF) experiments where iron may potentially also be present in the flow. Alternatively, fluorescence from this iron line can be circumvented by proper filtering of the PLIF. A proposal is made to turn the iron contamination into advantage by using iron present in the non-combusting flow for PLIF.

Product channels of the reactions of O2(b1[formula omitted

Laser-induced fluorescence (LIF) experiments have been employed to evaluate the branching fractions for the product channels for O2(b1Σg+) reactions with M = CO2, N2, H2, C2H4, N2O, H2O CH4 and I2 molecules. O2(b1Σg+) was formed by exciting ground-state oxygen molecules with pulses from a tunable dye laser, and the kinetics were followed by observing the temporal profiles of the O2 b1Σg+ − X3Σg-, O2a1Δg − X3Σg-, and I2 A′3Π2u, A3Π1u − X1Σg+ fluorescence signals. It has been found that O2(b1Σg+) is quenched to O2(a1Δg) with a branching fraction 1.00 ± 0.05 for all tested molecules except iodine. The reaction of O2(b1Σg+) with I2 has been found to have two dominant product channels, O2(X3Σg-) + I2(A′3Π2u or A3Π1u) and O2(X3Σg-) + 2 I(2P3/2) with branching fractions of 33 ± 7% and 67 ± 7%, respectively. Emission from I2(A′3Π2u or A3Π1u) molecules formed in recombination of iodine atoms in the gas phase was detected in the near IR.

Laser-induced fluorescence measurements in a single-ring test rig: Evidence of cavitation and the effect of different operating conditions and lubricants in cavitation patterns and initiation

The laser-induced fluorescence technique is based on the excitation of molecules of a fluorescent material by a light source. The main advantage of this technique is that it has the potential to quantify the lubricant film thickness throughout the cycle. Similar to all the other optical techniques, it has this major advantage compared to the electrical techniques where the oil film can be measured only under the piston rings. In this work, experimental data from a simulating single-ring test rig are presented and further parametric analysis is given regarding cavitation in lubricants that was, at first, in the case of the single-ring test rig, evident in laser-induced fluorescence measurements. Different lubricants are used for the laser-induced fluorescence experiments and the different laser-induced fluorescence signals are analysed and interpreted compared to their physical and chemical properties and, furthermore, with the aid of imaging through a glass liner, a clearer picture is given regarding the cavitation shapes together with the respective laser-induced fluorescence measurements and cavitation initiation.

Mixing process of two miscible fluids in a lid-driven cavity

A laminar lid-driven cavity flow was constructed to represent the fundamental characteristics of an industrial dynamic mixer. The flow patterns and mixing process in the cavity were measured by using particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) experiments respectively. The refractive indices of the two miscible liquids involved were carefully matched to allow for unhindered optical access. The mixing process was predicted by using computational fluid dynamics (CFD) including models for species transport. The simulated flow and mixing results are in good agreement with the experimental data. The effects of density difference and viscosity of the two miscible fluids on the mixing process were evaluated. Minor variations in the densities of the fluids have significant influence on the mixing process in terms of the coefficient of variation as a function of time. The dimensionless group ArRe (Archimedes number over Reynolds number) is proposed to characterize the mixing process in the cavity.

流动分离与涡结构显示的激光诱导荧光水洞实验技术

The purpose of the study on experiment technology of laser induced fluorescence in water tunnel is to provide a practical, intuitive, and effective method for flow visualization on separation and vortex structure. Rhodamine B was selected as the stain and fluorescence agent which matched the optical parameter and the characteristics of green laser sheet with 532 nm wavelength in 1 m1 m water tunnel. The study focused on the key technical problems such as the constitution and preparation method of stain and fluorescent agent, the selection of the optimum intensity of continuous laser, the matching relationship between flow velocity and the pore pressure of dyeing line and the matching relationship between camera field of view and the flow structure in the contrast of fine adjustment. The experiments were carried out to investigate the flow field around a cylinder, the wing of a transport plane model and the cargo door of a transport plane model together with the wake by means of the dedicated laser induced fluorescence experiment technology. The typical experiment results verify that the dedicated laser induced fluorescence technique is suitable for flow visualization on flow separation and vortex structure including boundary layer, spatial separation and wake field which is a promising method worthy of popularization and application.

Detailed modeling of soot particle formation and comparison to optical diagnostics and size distribution measurements in premixed flames using a method of moments

Recently improved knowledge about key processes for the formation and growth of soot particles lead to very extensive soot models describing several kinetic pathways for particle nucleation and growth in detail. One of these models has been proposed by D’Anna and coworkers (D’Anna et al., 2010, Sirignano et al., 2010). In these original studies, the multivariate formulation was solved with a sectional approach, while a more recent study (Salenbauch et al., 2017) also showed the suitability of moment methods such as the Conditional Quadrature Method of Moments (CQMOM) (Yuan et al., 2011). However, being a moment method, CQMOM does not allow to directly access the soot particle size distribution (PSD). This prevents the consistent comparability of CQMOM results to soot measurements based on a scanning mobility particle sizer (SMPS). Furthermore, the comparison to laser-induced fluorescence (LIF) experiments is also limited, as the LIF signal only represents small particles and their concentration is only extractable from the simulation results if the PSD shape is known.The aim of this study is to extend the previously developed CQMOM soot model by a PSD reconstruction step applying the concept of entropy maximization. Maintaining the efficiency of the CQMOM moment inversion algorithm to close the moment equations, the model extension enables to evaluate the diameter-based PSD in a post-processing step without prescribing a specific shape as input. The updated algorithm is applied to simulate soot formation in two different burner-stabilized premixed C2H4/O2/N2 flames with a very lightly sooting (C/O = 0.67) and a heavily sooting (C/O = 0.77) character. Numerical results are compared to recently published LIF, laser-induced incandescence (LII) and SMPS measurement data. The analysis investigates the model’s capability to predict phenomena such as uni- or bimodal distribution shapes and the transition of small nanostructures to agglomerates in the two target flames both of which exhibit very different sooting behaviour.