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Item type:Publication, Soot evolution in turbulent non-premixed bluff body flames: Assessment of detailed soot formation models using large eddy simulation(Centre National de la Recherche Scientifique, 2024-01-26)Exploring the complexities of soot formation in combustion systems implies recognizing the intricate interplay among turbulence, chemical kinetics, radiation, and soot particle dynamics. Achieving accurate predictions of soot levels in turbulent flames entails a meticulous representation of all stages of soot formation and oxidation, which prompts the development and use of detailed soot formation models. This work delves into three detailed soot models-Method of Moments with Interpolative Closure (MOMIC), Hybrid Method of Moments (HMOM), and Discrete Sectional Method (DSM)-integrated into the open-source computational tool OpenFOAM. Both the combustion process and the formation of soot precursors in the gas phase are characterized using the Flamelet Progress Variable combustion model along with the detailed ABF chemical kinetic mechanism. Turbulence is addressed through a Large Eddy Simulation based approach, and the computational results are compared with experimental data from the Adelaide ENB1 Bluff Body Flame. Specifically, the analysis extends to detailing flow velocities and their fluctuations, along with fields and profiles depicting soot volume fraction. In order to obtain quantitatively correct soot volume fractions, the nucleation sticking factor was adjusted. The comparative assessments of the soot formation models carried out provide a unique perspective on soot formation, highlighting different effects of each soot source terms and specific model limitations. HMOM described the measured soot volume fraction with greatest accuracy followed by DSM and MOMIC. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Soot formation models assessment in turbulent diffusion jet flames: A RANS-based comparison(Centre National de la Recherche Scientifique, 2024-10-02)A RANS-based Comparison Due to the intricate interaction between turbulence, chemical kinetics, radiation, and soot particle dynamics, modelling soot formation processes in flames is a challenging task. To predict the level of soot formed, it is essential to accurately capture all stages of soot formation and oxidation. Using a RANS approach, this study focuses on the implementation, within the computational open-source tool OpenFOAM, and comparison of three detailed soot formation models, (i) the Interpolative Closure Method of Moments (MOMIC), (ii) the Hybrid Method of Moments (HMOM), and (iii) the Discrete Sectional Method (DSM), as well as a semi-empirical two-equation model. Both the combustion process and the formation of soot precursors in the gas phase are described using the Steady Laminar Flamelet model and a detailed chemical kinetic mechanism. Radiation effects are modelled using the optically thin method. The computational results obtained here are compared with the experimental data characterizing the Adelaide ENH1 jet flame and other past numerical results. The results reveal significant differences in soot formation source terms among the models and for each of the soot formation stages. DSM best matches the experimental peak soot position, which is attributed to its modelling of condensation and surface growth occurring downstream compared to MOMIC and HMOM. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Computational assessment of detailed soot formation models in ethylene/air laminar diffusion flames(Centre National de la Recherche Scientifique, 2024-01-26)To improve the accuracy of soot formation and evolution predictions, several physical and chemical models have been developed over the last decades.These models include (i) detailed chemical kinetic mechanisms describing both gas-phase chemistry related to combustion processes and reaction pathways leading to large-sized aromatic molecules, which are needed for modeling soot formation, and (ii) soot models providing a comprehensive description of soot particle dynamics and interactions with gas-phase chemical species.Accordingly, in this work, two detailed soot models, the method of moments (MOM) and the discrete sectional method (DSM), are evaluated in ethylene/air laminar diffusion flames, and their corresponding results are compared with experimental measurements.Furthermore, the NBP and KM2 chemical kinetic mechanisms are assessed and compared with each other by examining key chemical species related to soot formation and evolution.To compute gas mixture's radiative properties, the weighted sum of gray gases model considering a gray medium is also utilized.Finally, the contributions of the soot precursors known as PAH (polycyclic aromatic hydrocarbon) to soot formation are also analyzed.The main results show that the discrepancies in PAH concentrations obtained with different chemical kinetic mechanisms can be significant.In addition, compared to MOM ones, DSM results obtained here show a better agreement with experimental data.Finally, the analysis of PAH shows that those with two (A2) to four (A4) aromatic rings impact the most on soot modeling.Specifically, contributions of A4 were found to be more significant at lower heights above the burner, whereas A2 was found to be more impactful downstream as the flame develops.Maximum contributions of A2 and A4 to the soot inception rate were 66% and 85%, respectively, whereas the maximum summed contribution of PAH with five (A4R5) to seven (A7) aromatic rings accounted for only 13% of the inception rate.