Transition from turbulence-dominated to instability-dominated combustion regime in lean hydrogen-air flames

Lipatnikov，Andrei N.1; Lee，Hsu Chew2,3; Dai，Peng2; Wan，Minping2,3,4; Sabelnikov，Vladimir A.5,6

2024

10.1016/j.combustflame.2023.113170

Combustion and Flame   影响因子和分区

0010-2180

1556-2921

To explore the importance of thermodiffusive and hydrodynamic instabilities of laminar flames in turbulent flows, previously generated direct numerical simulations of statistically one-dimensional complex-chemistry lean hydrogen-air flames in forced turbulence were continued by switching-off turbulence forcing. Three sets of flames characterized by different ratios of initial root-mean-square velocity to laminar flame speed, i.e., (A) u/S=2.2, (B) u/S=4.0, and (C) u/S=8.3, were addressed. Moreover, new complementary simulations of unstable laminar flames were performed. Analyses from the obtained numerical results indicate (but do not prove) that laminar flame instabilities play a minor role at sufficiently high Karlovitz numbers Ka. This supposition is supported, first, in cases B and C, where the initial value of turbulent burning velocity U is significantly higher than burning velocity evaluated during non-linear stage of laminar flame instability development in the same computational domain. Second, regular large-scale perturbations of instantaneous flame surface are prominent in the unstable laminar flame but are not observed at high Ka. Third, Karlovitz numbers associated with appearance of such perturbations as the turbulence decays are scattered between 4 and 10 and are consistent within an order of magnitude to a recently proposed criterion (Chomiak and Lipatnikov, Phys. Rev. E 107: 015102, 2023) of importance for laminar flame instabilities in turbulent flows. Fourth, at such transition instants, a ratio of potential and solenoidal turbulent kinetic energies, averaged over the flame-brush leading edge, is close to 2.0 in 11 studied cases and a ratio of U/S varies between 3.0 and 3.5. Fifth, the maximum fuel consumption rate (over the computational domain) decreases as the turbulence decays. Thus, the initial maximum rates are significantly higher than the counterpart rate in the unstable laminar flame. Together these results show that the hypothesis that laminar flame instabilities play only a minor role at high Ka deserves further study.

DNS Hydrogen Premixed flame Thermodiffusive instabilty Turbulent burning velocity

SCI ; EI

英语

通讯

ENGINEERING

2-s2.0-85175444069

Scopus

1.Department of Mechanics and Maritime Sciences,Chalmers University of Technology,Gothenburg,SE-412 96,Sweden
2.Guangdong Provincial Key Laboratory of Turbulence Research and Applications,Department of Mechanics and Aerospace Engineering,Southern University of Science and Technology,Shenzhen,518055,China
3.Guangdong-Hong Kong-Macao Joint Laboratory for Data-Driven Fluid Mechanics and Engineering Applications,Southern University of Science and Technology,Shenzhen,518055,China
4.Jiaxing Research Institute,Southern University of Science and Technology,Jiaxing,Zhejiang,314031,China
5.ONERA – The French Aerospace Laboratory,Palaiseau,F-91761,France
6.Central Aerohydrodynamic Institute (TsAGI),Zhukovsky,Moscow Region,140180,Russian Federation

Lipatnikov，Andrei N.,Lee，Hsu Chew,Dai，Peng,et al. Transition from turbulence-dominated to instability-dominated combustion regime in lean hydrogen-air flames[J]. Combustion and Flame,2024,259.

Lipatnikov，Andrei N.,Lee，Hsu Chew,Dai，Peng,Wan，Minping,&Sabelnikov，Vladimir A..(2024).Transition from turbulence-dominated to instability-dominated combustion regime in lean hydrogen-air flames.Combustion and Flame,259.

Lipatnikov，Andrei N.,et al."Transition from turbulence-dominated to instability-dominated combustion regime in lean hydrogen-air flames".Combustion and Flame 259(2024).