Shinichiro OGAWA

DOI Number: XXX-YYY-ZZZ

Conference number: HiSST2024-00218

To achieve ignition and stable combustion within a short residence time of milliseconds, the effective
stabilization of flames in scramjet combustors is crucial. Stable forced ignition and flame holding have
been explored in previous studies using various igniters, including micro-rocket torches and plasma jet
torches. In this study, the forced ignition and combustion instability of a scramjet combustor equipped
with a micro-rocket torch are investigated. Despite successful ignition promoted by the micro-rocket
torch in previous experiments, combustion instabilities were observed in the cavity flame holder, as
revealed by OH* chemiluminescence images. To elucidate the mechanisms of forced ignition and
combustion instability, modal analysis techniques, specifically dynamic mode decomposition (DMD), are
employed. DMD is a powerful method for extracting spatiotemporally coherent structures from high-
dimensional data, making it suitable for analysing combustion dynamics. DMD was applied to OH*
chemiluminescence images obtained from previous supersonic combustion experiments. The dominant
modes associated with combustion instability are identified, and their spectral characteristics are
investigated via power spectrum density (PSD) analysis. From the results, it is clarify the combustion
instability near the cavity flame holder, (a) in the case of low frequencies between 100 to 400 Hz were
formed by fuel injector flame feedback in this combustion result, (b) in the case of low frequencies
under 100 Hz (e.g., 15 to 50 Hz) were formed by torch gas injector flame feedback in this combustion
result, and (c) in the case of high frequencies over 1000 Hz were formed by interference between the
cavity flame holder and the flow field. Insights into the complex flow dynamics within the cavity flame
holder and the shear layer are provided, shedding light on the mechanisms underlying combustion
instability in scramjet engines equipped with micro-rocket torches.

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In Categories: 1.Events, HiSST 2024, Propulsion Systems and Components
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