A numerical support of leading point concept. (30th June 2022)

• Record Type: Journal Article
• Authors: Lee, Hsu Chew; Dai, Peng; Wan, Minping; Lipatnikov, Andrei N.
• Is Part Of: International journal of hydrogen energy. Volume 47:Number 55(2022)
• Page Start: 23444
• Page End: 23461
• Publication Date: 2022-06-30
• Subjects: Turbulent combustion -- Leading point concept -- Preferential diffusion -- Lewis number -- Turbulent burning velocity -- Hydrogen; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2022.05.140
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: Unsteady three-dimensional Direct Numerical Simulation (DNS) data obtained from 16 statistically planar and one-dimensional, complex-chemistry, lean (equivalence ratio is equal to 0.50 or 0.35) hydrogen-air flames propagating in forced, intense, small-scale turbulence (Karlovitz number up to 565) are reported. The data are analyzed to compare roles played by leading and trailing edges of a premixed turbulent flame brush in its propagation. The comparison is based on the following considerations: (i) positively (negatively) curved reaction zones predominate at the leading (trailing, respectively) edge of a premixed turbulent flame brush and (ii) preferential diffusion of molecular or atomic hydrogen results in increasing the local fuel consumption and heat release rates in positively or negatively, respectively, curved reaction zones. Therefore, turbulent burning velocities computed by deactivating differential diffusion effects for all species with the exception of either H2 or H are compared for assessing roles played by leading and trailing edges of a premixed turbulent flame brush in its propagation. By analyzing the DNS data, a significant increase in the local fuel consumption and heat release rates due to preferential diffusion of H2 or H is documented close to the leading or trailing, respectively, edges of the studied flame brushes. Nevertheless, turbulent burning velocities computed by activating preferential diffusion solely for H2 are significantly higher than turbulent burning velocities computed by activating preferential diffusion solely for H. This result indicates an important role played by the leading edge in the propagation of the explored turbulent flame brushes. Highlights: Crucial role played by the leading edge of a premixed turbulent flame brush is evidenced. Preferential diffusion of H2 significantly accelerates even highly turbulent lean H2 -air flames. This effect is significantly more pronounced in leaner flames. Preferential diffusion of H weakly affects burning velocity of such flames.