This study experimentally investigates flame dynamics during a combustion-driven mode transition in a cavity-stabilized scramjet model with an inlet Mach number of 2.2 using a split fuel injection scheme. Fueling into the cavity was gradually increased while keeping a constant global equivalence ratio of 0.3. A cavity-fueling percentage below 15% resulted in low-intensity combustion that corresponded to operation in scram mode. Redirecting 29% of the fuel from the upstream injection port to the cavity yielded flame spreading into the main flowpath, inducing intense combustion. A sharp pressure rise and an intense combustion region in the diverging section suggest dual-mode combustion, with thermal choking and a pseudoshock formation downstream of the cavity. An intermediate cavity-fueling fraction of 21% led to a low-frequency instability ( 5    Hz ) with intermittent transitions between the combustion modes, indicating operation at the thermal choking limit. Spectral and modal analyses of CH * chemiluminescence images and static-pressure measurement indicate peak response at 10–20 Hz and 50    Hz , originating from oscillations in the air heater and a fuel jet instability, respectively. Thermally chocked conditions significantly amplify oscillations at these frequencies. At the thermal choking limit, there was high-amplitude response at 50    Hz , preventing stable dual-mode operation.


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    Title :

    Combustion Instability due to Combustion Mode Transition in a Cavity-Stabilized Scramjet


    Contributors:

    Published in:

    Publication date :

    2022-05-16


    Size :

    12 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English



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