On the self-starting performance of hypersonic inlets under the influence of leading-edge bluntness

To study the effect of leading-edge bluntness on the self-starting characteristics of a hypersonic inlet, a two-dimensional Mach 6 inlet is examined. The self-starting behavior and flow evolution are compared for five bluntness radii. Numerical simulations show that the self-starting process is similar for both sharp and blunt leading edges, comprising four stages: unstart, disappearance of subsonic spillage at the cowl lip, ingestion of the separation bubble on the compression surface, and stable start. Leading-edge bluntness alters the internal shock structure: as the bluntness radius increases, the throat mass flow, entrance Mach number, and total-pressure recovery decrease, while the self-starting Mach number rises. Compared with a sharp leading edge, a small dimensionless bluntness (R/H_i = 0.0077) has minor effects, increasing the self-starting Mach number by only 0.1 and reducing total-pressure recovery by 0.022. With R/H_i = 0.0309, the separation zone at Mach 2.0 lengthens by 5.58 % and the self-starting Mach number increases by 1.3. The entropy layer behind the blunt leading edge is the primary cause of the higher self-starting Mach number. Increased bluntness thickens the entrance boundary layer and enlarges the separation bubble during unstart state, thereby raising the self-starting Mach number.