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Item type:Publication, Soot modeling in turbulent diffusion flames: review and prospects(Springer Science and Business Media Deutschland GmbH, 2021-04-01)This work reviews the state of the art of the main soot modeling approaches used in turbulent diffusion flames. Accordingly, after a short introduction about the subject addressed here, the main soot formation mechanisms are described next. This description provides the basis for the discussions about the different soot modeling techniques employed nowadays for soot predictions. Since combustion and radiation models have a significant impact on soot predictions, as a consequence of the strong coupling between chemistry, turbulence and soot formation, a general overview about these models is also provided. For the sake of clarity, the main soot formation models reviewed in this work are classified as semiempirical soot precursor models and detailed ones. Both advantages and disadvantages of the referred soot modeling approaches are properly discussed. In the last part of this review, comparative results obtained using some of the main soot models currently available are presented along with a discussion about the prospects for soot modeling in turbulent flames. Finally, some conclusions and references are provided. Overall, based on the literature reviewed, it is concluded that there is yet a long path to be followed before understanding first and having then a soot model able to properly describe the formation of this critical pollutant for a variety of situations of industrial interest. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Genetic algorithms-based size optimization of directly and indirectly coupled photovoltaic-electrolyzer systems(Elsevier Ltd, 2022-10-15)Since relatively high costs and low efficiencies are usually associated with photovoltaic-electrolyzer (PV-EL) systems, the coupling of a PV system to an EL one is a critical aspect when sizing PV-EL systems. Accordingly, using a genetic algorithms-based optimization approach and considering a hydrogen production target of 100 g per day, the size of different directly and indirectly coupled PV-EL systems is optimized in this work. The referred optimization processes are carried out for five PV-EL system configurations, one related to directly coupled systems and four (one per each DC/DC converter topology accounted for) to indirectly coupled ones. In addition, seeking to maximize hydrogen production, minimize losses, and increase system efficiency, four objective functions are assessed. Some of the results highlight that, when using system cost and overall efficiency as objective functions, properly sized indirectly coupled PV-EL systems feature lower implementation costs than directly coupled ones. In addition, the differences in the overall efficiencies characterizing the optimum directly and indirectly coupled PV-EL systems so determined are relatively small (>1%). One of the original contributions of this work relates to the fact that this is one of the first works dealing with optimization processes of both directly and indirectly coupled PV-EL systems, where optimum system configurations are compared with each other. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Flow-field analysis and performance assessment of rotating detonation engines under different number of discrete inlet nozzles(Elsevier Ltd, 2024-12-01)This study explores in depth rotating detonation engines (RDEs) fueled by premixed stoichiometric hydrogen/air mixtures through two-dimensional numerical simulations including a detailed chemical kinetic mechanism. To model the spatial reactant non-uniformities observed in practical RDE combustors, the referred simulations incorporate different numbers of discrete inlet nozzles. The primary focus here is to analyze the influence of reactant non-uniformities on detonation combustion dynamics in RDEs. By systematically varying the number of reactant injection nozzles (from 15 to 240), while maintaining a constant total injection area, the study delves into how this variation influences the behavior of rotating detonation waves (RDWs) and the associated overall flow field structure. The numerical results obtained here reveal significant effects of the number of inlets employed on both RDE stability (self-sustaining detonation wave) and performance. RDE configurations with a lower number of inlets exhibit a detonation front with chaotic behavior (pressure oscillations) due to an increased amount of unburned gas ahead of the detonation wave. This chaotic behavior can lead to the flame extinguishing or decreasing in intensity, ultimately diminishing the engine's overall performance. Conversely, RDE configurations with a higher number of inlets feature smoother detonation propagations without chaotic transients, leading to more stable and reliable performance metrics. This study uses high-fidelity numerical techniques such as adaptive mesh refinement (AMR) and the PeleC compressible reacting flow solver. This comprehensive approach enables a thorough evaluation of critical RDE characteristics including detonation velocity, fuel mass flow rate, impulse, thrust, and reverse pressure waves under varying reactant injection conditions. The insights derived from the numerical simulations carried out here enhance the understanding of the fundamental processes governing the performance of RDE concepts. - Some of the metrics are blocked by yourconsent settings
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.