Impact Factor:5.8

DOI number:10.1016/j.combustflame.2024.113928

Journal:Combustion and Flame

Key Words:Shock-flame interactions, Richtmyer–Meshkov instability, Cool flame, Low-temperature chemistry, Flame dynamics

Abstract:Spherical cool, warm, and hot flames and their transitions during shock-flame interactions (SFI) are numerically studied using dimethyl ether (DME)/air mixtures. The flame dynamic, structure, regime transition, and chemical kinetics are investigated by varying incident shock strengths (Ma = 1.1, 1.6, 2.1, or 2.6) and initial flame states (cool, double, or hot flames). Our findings reveal that shock wave strength significantly influences cool flame evolution and transition. Weak shocks (Ma = 1.1) allow cool flames to persist, while moderate shocks (Ma = 1.6 and 2.1) lead to the formation of cool-warm coexisting flames. This occurs as shock-induced temperature and pressure increases activate intermediate-temperature reaction pathways in the partially-oxidized region downstream of the cool flame. Strong shocks (Ma = 2.6) rapidly transform cool flames into hot flames, with the resulting heat release significantly impacting flame shape, burning rate, vorticity generation, and other flow characteristics. Notably, we observe intriguing multilayered flame structures at different Mach strengths arising from the slow propagation of cool flames and vortex-flame interactions. Statistical analysis reveals that while mass burning rates increase with higher shock Mach numbers, flame area exhibits a non-monotonic trend for cool flames. Detailed examination of flame dynamics shows that Richtmyer–Meshkov instability (RMI)-driven vortices weaken and stretch flame fronts. Both upstream and downstream fronts experience positive stretching, with the former being reaction-controlled and the latter diffusion-controlled, highlighting the unique dynamics of shock-cool flame interactions. Given the transient nature of cool flames, which naturally evolve into double flames and eventually hot flames, we extended our study to examine the effects of different initial flame types on shock-flame interaction. Our analysis includes numerical Schlieren visualization of multiple incident and reflected shock waves near the flame interface, as well as statistical analysis of flame width, area, burning velocity, and mixing rate across various initial flame conditions. A notable discovery is the observation of transient triple flames (cool, warm, hot) during moderate shock interactions with double flames. This study summarizes a comprehensive phase diagram for cool, warm, and hot flames and extinction regimes. The current work holds significant importance by unveiling novel shock-cool flame interactions and providing insights for supersonic combustion considering detailed chemistry.

Co-author:Weizong Wang

First Author:E Fan

Indexed by:Journal paper

Correspondence Author:Tianhan Zhang

First-Level Discipline:Power Engineering and Engineering Thermophysics

Document Type:J

Volume:273

Translation or Not:no

Date of Publication:2024-12-30

Included Journals:SCI

Links to published journals:https://www.sciencedirect.com/science/article/pii/S0010218024006370?dgcid=author

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