Congratulations to our PhD Candidate Andrea Bertolino! His paper with title "Prediction of flammable range for pure fuels and mixtures using detailed kinetics" has been recently published on Combustion and Flame.

Flammable ranges of hydrocarbons

 

 

Bertolino A., Stagni A., Cuoci, A., Faravelli, T., Parente A., Frassoldati A., Prediction of flammable range for pure fuels and mixtures using detailed kinetics(2019) Combustion and Flame, 207, pp. 120-133, DOI: 10.1016/j.combustflame.2019.05.036

 

Abstract

In this work, the flammable range of several hydrocarbons was predicted using a freely-propagating flame method for pure hydrocarbons and their mixtures, investigating the effects of operating conditions, in terms of temperature, pressure, fuel/oxidizer composition. The model showed accurate agreement with a wide set of experimental data. The average deviation between the experiments and the model was reduced to ∼20% for the UFL of methanol, methane, ethane, propane, n-butane, n-heptane, ethylene, benzene and two different mixtures, methane/ethylene and methanol/benzene. Model performance was improved for the upper flammability limit by including the effect of soot radiation, modeled using an optically-thin approximation. A comprehensive kinetic mechanism was adopted, and a skeletal kinetic mechanism including a soot sectional model was used to predict soot formation in rich flames. Comparison with Calculated Adiabatic Flame Temperature (CAFT) and Le Chatelier models was also carried out, discussing the advantages of a model including the effects of chemical kinetics. Sensitivity analysis was performed to point out the major role of chemical kinetics especially at the UFL, where chemistry drives the process. This methodology showed that the chemical interaction between two different fuels at the rich limit is the reason for the deviation from the thermally controlled behavior. Finally, chemistry was found to be relevant even for the lean flammability limits predictions of lower alkanes, when pure N2O is used as oxidizer.

The CRECK Modeling Lab is proud to have 8 presentations at the Seventeenth International Conference on Numerical Combustion in Aachen (Germany), 6-8 May 2019

  • 165 Towards an automated and generalized approach to the validation of kinetic models, Alessandro Stagni, Matteo Pelucchi, G. Scalia, Alberto Cuoci, B. Pernici, Tiziano Faravelli
  • 189 Large Eddy Simulation of MILD combustion with implicit combustion models, Z. Li, Alberto Cuoci, A. Parente
  • 225 Feature extraction in combustion applications, G. D’Alessio, G. Aversano, K. Zdybał, Alberto Cuoci, A. Parente
  • 292 Assessment of finite-rate chemistry models for highly turbulent jet flames, Arthur Péquin, Z. Li, Alberto Cuoci, A. Parente
  • 339 Effect of the training dataset and data preprocessing on adaptive-chemistry simulations, G. D’Alessio, G. Aversano, Alberto Cuoci, A. Parente
  • 391 Efficient tool for optimization of chemical kinetics using Dakota and OpenSMOKE++, M. Fürst, A. Bertolino, Alberto Cuoci, Alessio Frassoldati, A. Parente
  • 419 Predictive Automated Combustion Chemistry: A DOE-Exascale Project, S. Klippenstein, A. Copan, S. Elliott, M. Johnson, M. Keceli, Y.-P. Li, K. Moore, R. Van de Vivjer, Y. Wu, C. Cavallotti, Y. Georgievskii, B. Green, A. Jasper, T. Lu, J. Zádor, R. Bair, A. Wagner, J. Wozniak, Matteo Pelucchi
  • 428 From Electronic Structure to Temperature and Pressure Dependent Rate Constants: EStokTP. A Code for Automatically Predicting the Thermal Kinetics of Reactions, C. Cavallotti, Matteo Pelucchi, Y. Georgievskii, S. Klippenstein

Pelucchi Bio-oils Cover RCECongratulations to Matteo Pelucchi! His recent paper on "Detailed kinetics of substituted phenolic species in pyrolysis bio-oils" has been selected as the front cover paper of last issue of Reaction Chemistry & Engineering journal.

 

Pelucchi, M., Cavallotti, C., Cuoci, A., Faravelli, T., Frassoldati, A., Ranzi, E. , Detailed kinetics of substituted phenolic species in pyrolysis bio-oils, (2019) Reaction Chemistry & Engineering, 4, pp. 490-506, DOI: 10.1039/C8RE00198G

 

Abstract

Fast biomass pyrolysis is an effective and promising process to obtain high yields of bio-oils, whose upgrading provides valuable fuels for energy application or chemicals for industry. The growing interest in the use of bio-oils in combustion devices to produce energy motivates this study, in which we present the first comprehensive kinetic model to describe systematically the pyrolysis and combustion of substituted phenolic species, considered as reference components in bio-oil surrogate mixtures. In fact, bio-oils are complex liquid mixtures, containing a large variety of oxygenated organic species. Within these species, substituted phenolic compounds are one of the most significant fractions (∼20–30 wt%). A reliable characterization of the combustion properties and pollution potential of bio-oils strongly depends on the accurate knowledge of their combustion chemistry. While some experimental and kinetic modeling studies on pyrolysis and combustion of phenol, anisole, and catechol are available in the literature, only limited efforts have been devoted to the understanding of the decomposition and oxidation kinetics of guaiacol (2-methoxyphenol) and vanillin (4-hydroxy-3-methoxybenzaldehyde). Accurate theoretical calculations of bond dissociation energies have been performed to assess proximity effects originating from multiple substitutions on the aromatic ring. Based on these evaluations and on previous studies, rate rules and reference kinetic parameters are proposed for major pyrolysis and combustion reaction classes. Satisfactory comparisons of model predictions with experimental data of pyrolysis and combustion of anisole, catechol, guaiacol, and vanillin hierarchically support the development and the reliability of the proposed kinetic model. This work provides a valuable basis for further developments and strongly motivates additional experimental, theoretical, and kinetic modelling efforts in the area of reference components for bio-oil surrogates.

 

A paper on coal with title "Fully-resolved simulations of coal particle combustion using a detailed multi-step approach for heterogeneous kinetics" has been recently published on Fuel as the result of a successfull collaboration between CRECK Modeling Lab, University of Stuttgart, University of Duisburg Essen, Technical University Freiberg, and Darmstadt University of Technology.

Figure Fuel2019

 

 

Tufano, G.L., Stein, O.T., Kronenburg, A., Gentile, G., Stagni, A., Frassoldati, A., Faravelli, T., Kempf, A.M., Vascellari, M., Hasse, C., Fully-resolved simulations of coal particle combustion using a detailed multi-step approach for heterogeneous kinetics, (2019) Fuel, pp. 75-83, DOI: 10.1016/j.fuel.2018.11.139

 

Abstract

Fully-resolved simulations of the heating, ignition, volatile flame combustion and char conversion of single coal particles in convective gas environments are conducted and compared to experimental data (Molina and Shaddix, 2007). This work extends a previous computational study (Tufano et al., 2016) by adding a significant level of model fidelity and generality, in particular with regard to the particle interior description and heterogeneous kinetics. The model considers the elemental analysis of the given coal and interpolates its properties by linear superposition of a set of reference coals. The improved model description alleviates previously made assumptions of single-step pyrolysis, fixed volatile composition and simplified particle interior properties, and it allows for the consideration of char conversion. The results show that the burning behavior is affected by the oxygen concentration, i.e. for enhanced oxygen levels ignition occurs in a single step, whereas decreasing the oxygen content leads to a two-stage ignition process. Char conversion becomes dominant once the volatiles have been depleted, but also causes noticeable deviations of temperature, released mass, and overall particle conversion during devolatilization already, indicating an overlap of the two stages of coal conversion which are usually considered to be consecutive. The complex pyrolysis model leads to non-monotonous profiles of the combustion quantities which introduce a minor dependency of the ignition delay time tau(ign) on its definition. Regardless of the chosen extraction method, the simulations capture the measured values of tau(ign) very well.

Congratulations to our PhD Candidate Warumporn Pejpichestakul! Her paper with title "Buoyancy effect in sooting laminar premixed ethylene flame" has been recently published on Combustion and Flame.

Figure CF2019

 

 

Pejpichestakul W., Cuoci, A., Frassoldati, A., Pelucchi, M., Parente, A., Faravelli, T., Buoyancy effect in sooting laminar premixed ethylene flame, (2019) Combustion and Flame, 205, pp. 135-146, DOI: 10.1016/j.combustflame.2019.04.001

 

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are known as soot precursors, but their formation/consumption is not fully understood. A recent comprehensive experimental study of premixed laminar ethylene flame (Carbone et. al., Combust. Flame, 181 (2017), pp. 315-328) investigated the transition from gas-phase to soot particles. The complex fluid dynamics of this system is taken into account to compare model predictions with experimental measurements and thus further validate a detailed kinetic mechanism of soot formation. The relatively low inlet velocity and the large distance between the burner and the stagnation plate lead to significant influence of buoyancy, which requires a 2-D simulation. The observed constricted (necking) flame structure can be reproduced only using a comprehensive 2-D simulation, which includes buoyancy effects, radiative heat losses, and thermal diffusion. Predicted axial gaseous and PAH species profiles obtained from the CRECK mechanism are in good agreement with the measurements, especially even-carbon-number aromatics. Reasonable agreement of the predicted soot volume fraction profiles is also observed. Additionally, simulation results from different literature kinetic mechanisms are also discussed to highlight similarities and differences. The largest discrepancies among the predictions of the mechanisms are observed for phenylacetylene, a key-species representing the first building block of PAHs synthesis in flames.
A comprehensive analysis of relevant physical sub-models is also carried out in 2-D simulations. Additionally, predicted profiles from 2-D and 1-D simulations are compared. Following the literature, a 1-D simulation with imposed mass flux from the 2-D model was carried out to account for buoyancy effects. This approach provides an axial predicted flame temperature profile similar to the 2-D case. However, the predicted mole fraction profiles are quite different, especially for hydrogen and aromatics species because of the failure in accounting for the interplay of enhanced diffusion due to Soret effect, flame stretch, and large radial velocities in the proximity of the stagnation plane.

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H2020 JETSCREENh2020

 

 

 

Find out more about the JETSCREEN Project, which received funding from the European Union's Horizon 2020 research and innovation programme for developing a screening and optimization platform for alternative fuels

H2020 IMPROOFh2020

 

 

 

Find out more about the IMPROOF Project, which received funding from the European Union's Horizon 2020 research and innovation programme for improving the energy efficiency of steam cracking furnaces, while reducing emissions of greenhouse gases and NOx.