Cellularization and intrinsic instability characteristics of 2-methylfuran spherical expanding flame

Abstract

ABSTRACT The flame morphology, flame instability and thermodynamic parameters of 2-methylfuran (2-MF) spherically expanding flame were studied at different initial temperatures, initial pressures, and equivalence ratios. Quantitative analysis of 2-MF flame surface cracks and cell structures was performed. The radius for the crack to enter the accelerated growth stage is reduced by 52.9% as the initial pressure increases from 2 bar to 4 bar. Also, the radius at which the crack enters the accelerated growth stage is reduced by 16.4% when the equivalence ratio is increased by 0.1. The radius required for the average cell area to stabilize is reduced by 31.5% when the initial pressure increases from 2 bar to 4 bar. Additionally, instability parameters were studied, and the results revealed that hydrodynamic instability and thermal-diffusion stability increase with increasing Peclet number. The relationship between the local instability and stability curves was discussed. The average wavenumber fitting line is closer to the upper limit of the instability curve when the equivalence ratio is 1.4, which is 8.5% higher than that of the equivalence ratio of 1.3. Next, the flame self-acceleration was studied, the initial pressure and equivalence ratio greatly promote the self-acceleration of the flame, but the temperature has no obvious effect, and the self-acceleration exponent of 2-MF flame is less than 1.5. Finally, the flame image information was reconstructed by a reconstruction algorithm and the cellularity factor was formulated to measure the degree of flame cellular. The cellularity factor is affected by initial pressure and equivalence ratio. Comparing and analyzing the evolution of flame cracks, flame self-acceleration, and cellularity factor, it was found that flame cracks promote flame self-acceleration and exacerbate flame cellularization and instability.