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Effects of pressure on cellular flame structure of high hydrogen content lean premixed syngas spherical flames: A DNS study

Ranga Dinesh, KKJ; Shalaby, H; Luo, KH; van Oijen, JA; Thévenin, D; (2016) Effects of pressure on cellular flame structure of high hydrogen content lean premixed syngas spherical flames: A DNS study. International Journal of Hydrogen Energy , 41 (46) pp. 21516-21531. 10.1016/j.ijhydene.2016.09.181. Green open access

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Abstract

The structure and propagation of turbulent lean premixed high hydrogen content syngas flames at pressure values of 1 bar, 2 bar and 4 bar are studied using three-dimensional direct numerical simulations. Simulations for each pressure considered were performed for three different initial turbulence levels at the turbulent Reynolds numbers of 50, 100 and 150. The DNS of expanding spherical flames has taken into account detailed chemical kinetics and preferential diffusion effects. The mixture-averaged transport model has been employed. Effects of pressure on flame structures, heat release rate and radical species distributions under low to high initial turbulent conditions are examined. The results show that elevated pressures greatly influence the cellular flame structure of syngas spherical flames under different initial turbulent conditions. At the atmospheric pressure, the flame shows weakly wrinkling structures due to the initial turbulence level imposed in the simulation. At elevated pressures under turbulence conditions, the flame develops cellular burning structures, superimposed by flame wrinkles due to turbulence. It is shown that highly wrinkled cells that develop over the surface of a spherical flame increase its area and thereby the global propagation speed at elevated pressures. Results show noticeable increases in the local heat release rate with increasing pressure. The analysis also reveals the formation of cusped structures with low heat release rate values in areas of negative curvatures at elevated pressures, in agreement with previous studies. The joint probability density functions of OH radical mass fraction and temperature show broadening OH values in the high temperature zone at elevated pressures compared to its distribution at the atmospheric pressure. Comparisons of mean species distributions of OH and HO2 over temperature between laminar and turbulent flames show that pressure elevation has a major influence on the flame structure in the composition space.

Type: Article
Title: Effects of pressure on cellular flame structure of high hydrogen content lean premixed syngas spherical flames: A DNS study
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.ijhydene.2016.09.181
Publisher version: http://dx.doi.org/10.1016/j.ijhydene.2016.09.181
Additional information: © 2016. This manuscript version is published under a Creative Commons Attribution Non-commercial Non-derivative 4.0 International licence (CC BY-NC-ND 4.0). This licence allows you to share, copy, distribute and transmit the work for personal and non-commercial use providing author and publisher attribution is clearly stated. Further details about CC BY licences are available at http://creativecommons.org/licenses/by/4.0. Access may be initially restricted by the publisher.
Keywords: Direct numerical simulation; Spherical flames; Pressure effects; Cellular flame structure; Heat release rate; Radicals
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Mechanical Engineering
URI: https://discovery.ucl.ac.uk/id/eprint/1532214
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