Abstract Scramjet inlets typically ingest air that has been processed by a vehicle forebody. The forebody generates entropy and boundary layers that affect the thermodynamic properties of the ingested air and hence influence inlet mass capture, combustion performance and unstart characteristics. This paper investigates the effects of leading edge bluntness on combustion performance of a scramjet at Mach 8 flight conditions, focussing on combustion-induced pressure rise and transition between scram- and dual-mode combustion. Simulations have been performed on a 3D supersonic combustion flow path with length of order 1 m, examining the effects of forebody leading edge radii, finding that a large radius of 0.3% the engine length can produce engine unstart and significantly decrease inlet mass capture by over 45%. An experimental scramjet model has been tested to examine these effects with more reasonable, sharper radii of either 0.02% (sharp case) and 0.05% (blunt case) of the engine length for leading edges of both the forebody and the inlet walls. These experiments show that changing the forebody leading edge radii can have a strong impact on combustion mode within a scramjet flow path, with the blunt leading edge inducing dual-mode combustor earlier than the sharp leading edge. For higher equivalence ratios where both cases produce dual-mode combustion, the sharp forebody leading edge produced an increase of 5% of normalised gross thrust compared to the blunt case, indicating the increased losses for a blunt leading edge. This was consistent with numerical simulations of the two cases at an equivalence ratio of 1.4. These results suggest that changes to leading edge bluntness can influence gross thrust, engine operation mode and even trip the engine into full unstart. Thus, the leading edge radius on a hypersonic vehicle must be controlled over a vehicle's trajectory, and should not be allowed to melt or deform into a larger radius.


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    Title :

    The effect of leading edge bluntness on scramjet performance




    Publication date :

    2024-01-18




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English