4.7 Article

Self-similar propagation and flame acceleration of hydrogen-rich syngas turbulent expanding flames

Journal

FUEL
Volume 350, Issue -, Pages -

Publisher

ELSEVIER SCI LTD
DOI: 10.1016/j.fuel.2023.128813

Keywords

Hydrogen -rich syngas; Turbulent premixed expanding flame; Flame self -similar propagation; Flame acceleration

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Investigations were conducted on the flame self-similar propagation and flame acceleration characteristics of hydrogen-rich syngas turbulent expanding flames. The study found that the flame propagation speed and turbulent flame Reynolds number could be represented by power-law correlations. The increase in hydrogen fraction weakened the flame acceleration, while the decrease in equivalence ratio increased it due to the coupling between differential-diffusion and flame stretch.
In order to investigate the flame self-similar propagation and flame acceleration characteristics of hydrogen-rich syngas turbulent expanding flames, the turbulent combustion experimental studies of H2/CO/air mixtures with XH2 = 55%-95%, & phi; = 0.6-1.0, P = 1 bar-3 bar, u'=0.809-2.533 were conducted in a fan-stirred turbulent combustion chamber with an inner diameter of 380 mm. Results show that the normalized flame propagation speed ST/SL and turbulent flame Reynolds number ReT,flame could be represented by power-law correlations. With the increase of hydrogen fraction from 55% to 95%, the power exponent decreases from 0.413 to 0.301. The increase of hydrogen fraction makes the flame acceleration weaker because that the enhancing of laminar flame speed is more obvious than the differential-diffusion effect by decreasing Le. With the decrease of equivalence ratio from 1.0 to 0.6, the power exponent increases from 0.304 to 0.411 in this study. The relative high power exponent under low equivalence ratio is due to the coupling between differential-diffusion and the flame stretch on the local wrinkled flame structures. In addition, the influence of turbulence and flame intrinsic instabilities on flame acceleration propagation process of hydrogen-enriched syngas were studied. The acceleration exponent was extracted to quantitatively investigate the flame self-acceleration propagation in the transition stage, and the relationships between acceleration exponent and turbulence intensity (u'), Kovasznay number (Kz), turbulence integral length scale (LT), flame thickness (& delta;), thermal expansion ratio (pu/pb), effective Lewis number (Leeff) were analyzed

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