A numerical study was undertaken using the commercial Computational Fluid Dynamics code CFD ++ to analyse the ignition behaviour of a three-dimensional non-uniform compression Scramjet. The study concerned itself with understanding how 3D flow features / combustion coupling enables the combustion flame to propagate from higher to lower compression regions within the combustor. A premixed H_2/Air mixture with an equivalence ratio of 1 was used to decouple the influence of fuel injection on combustion characteristics. The free stream properties corresponded to a flow enthalpy, total temperature and total pressure of 4.5 MJ/kg (Mach 10), 4676 K and 8 MPa respectively. Three sources of flame propagation into the low compression region were identified: 3D Flow Structures which provide ignition sources within the boundary layer, Radical Transport within a 3D shock-induced boundary layer separation and Thermal Compression from combustion within the high compression region. All three sources had a significant influence in propagating the flame into the low compression region.
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