Onset of cellular instability and self-acceleration propagation of syngas spherically expanding flames at elevated pressures (PDF)
Release Time:2025-04-30
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- Date:
- 2025-04-30
- Title of Paper:
- Onset of cellular instability and self-acceleration propagation of syngas spherically expanding flames at elevated pressures (PDF)
- Journal:
- Int J Hydrogen Energy
- Summary:
- Systematic study on the onset of cellular instability and self-acceleration propagation for syngas spherically expanding flames is investigated. Three onsets of crack branching, uniform cellularity and transition acceleration are obtained from Schlieren images and Sb-κcurves. Effective Lewis number Leeff and thermal expansion ratio σ are controlled independently by adjusting equivalence ratio and oxygen-nitrogen ratio. Results show that the order of three onsets is crack branching < transition acceleration < uniform cellularity. The critical flame radius is increased with Leeff but decreased with σ. Also, it is decreased with hydrogen volumetric fraction, leading to a much earlier onset at 85% hydrogen fraction. The theoretical result can give a qualitative prediction and closer to uniform cellularity onset quantitatively, although it overestimates Leeff effects a little. The critical Peclet number of uniform cellularity onset is not only increased with Leeff but also increased with σ, mainly due to the variation of flame thickness. Besides, there is a positive correlation between critical Peclet number and Markstein number, indicating a strengthened inhibition of stretch. The onset of similarity acceleration is also obtained through acceleration exponent and it performs a similar variation trend as that of cellular instability. All of these demonstrate that both cellular instability and similarity acceleration are the coupling results of diffusional-thermal instability, hydrodynamic instability and stretch.
- Co-author:
- Zhao HR， Wang JH, Bian ZJ, Cai X, Li XT, Huang ZH
- Volume:
- 2019, 44(51): 27995-28006
- Page Number:
- 27995-28006
- Translation or Not:
- No
- Date of Publication:
- 2019-10-22