Wang, X;
Jin, T;
Luo, KH;
(2019)
Response of heat release to equivalence ratio variations in high Karlovitz premixed H2/air flames at 20 atm.
International Journal of Hydrogen Energy
, 44
(5)
pp. 3195-3207.
10.1016/j.ijhydene.2018.12.027.
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Abstract
This paper presents three-dimensional direct numerical simulations of lean premixed H2/air flames with equivalence ratios 0.4, 0.5 and 0.6, respectively. The initial Karlovitz number is around 2335 and the pressure is 20 atm, which is relevant to gas turbine conditions. The heat release in reaction zones under different equivalence ratios is examined statistically with the aim to extend our understanding of lean combustion under high-pressure conditions. With increasing equivalence ratio, the relative thickness of reaction zone (δf/δL) is increasing for both laminar and turbulent flames, but the extent of increase is reduced under high equivalence ratio. By examining the local structures of flame fronts, it is found that trenches and plateaus of local equivalence ratio are located on separate sides of the reaction zone edge. Due to the decreased Lewis number under high equivalence ratio, the trench ‘depth’ and plateau ‘height’ are reduced. For the flame under ultra-lean conditions, there are some spots with temperatures above adiabatic temperature. This is attributed to the high-fraction of radicals in these regions, which will promote heat release. Furthermore, the heat release rates of elementary reactions are investigated with the analysis of radical fractions and rate constants. When the mixture equivalence ratio varies, the local heat release is changed in different temperature windows due to the combined effects of radical fractions and reaction rate constants.
| Type: | Article |
|---|---|
| Title: | Response of heat release to equivalence ratio variations in high Karlovitz premixed H2/air flames at 20 atm |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1016/j.ijhydene.2018.12.027 |
| Publisher version: | https://doi.org/10.1016/j.ijhydene.2018.12.027 |
| Language: | English |
| Additional information: | This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | Science & Technology, Physical Sciences, Technology, Chemistry, Physical, Electrochemistry, Energy & Fuels, Chemistry, Direct numerical simulation, Lean premixed flame, Heat release rate, Equivalence ratio, DIRECT NUMERICAL-SIMULATION, THERMAL UNIMOLECULAR REACTIONS, HYDROGEN JET FLAME, FALL-OFF RANGE, LEWIS NUMBER, PRESSURE, COMBUSTION, LAMINAR, SPEED, MIXTURES |
| UCL classification: | UCL 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/10068827 |
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