This study deals with the spread of flames in a narrow gap which consists of the vertical space between a thick fuel sample and the non-combustible material at the top or roof of the channel (typically quartz or glass for visualization). A related scenario may occur behind walls (e.g., panels containing electronics wiring) and inside electronic equipment, which leads to interesting and difficult flame behaviors not typically seen in open flame spread. This setup (called the Narrow Channel) also largely reproduces conditions experienced by spreading microgravity flames. The samples of PMMA used in this research are ignited in a Narrow Channel Apparatus (NCA) in normal gravity. The primary variable in these tests in the opposed flow velocity which strongly influences the flame spread rate and the structure of the flame front. The phenomena studied include bifurcation into flamelets, recombination, receding flame fronts and various flame front oscillations as well as flame-front tunneling.
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