Numerical Analysis and Optimization of Bleed Systems for External Supersonic Compression Inlets

A two-stage numerical programme is conducted in order to enhance the functionality of the bleed system of a single-ramp external-compression inlet. Initially, three-dimensional RANS calculations of eight representative perforated plates are utilised to calibrate a porous-jump model. This approach results in a cost reduction of the subsequent design survey by an order of magnitude, while maintaining pressure-loss accuracy within ±2%. A 5³ full-factorial design (hole diameter, length-to-diameter ratio L/D, and porosity) comprising 125 geometries is then analysed for the entry plate with response-surface methodology, Shannon-entropy weighting, and multi-objective desirability optimisation. The analysis of variance demonstrated that porosity and L/D accounted for in excess of 95% of the summed squares in the mass-flow ratio, drag coefficient and discharge coefficient. Conversely, diameter was found to be statistically insignificant over the range that was tested. Optimisation returned a compact entry-plate optimum of L/D≈1.0 and porosity≈0.20. Subsequent repetition of the procedure for the exit plate, following the elimination of the weakly sensitive discharge coefficient, resulted in an optimum of L/D=0.25 and porosity ≈ 0.47. The installation of both optimised plates resulted in an enhancement of total-pressure recovery by 2.2–2.3% at the baseline buzz-onset points (MEF=0.46 for M∞=1.6 and 0.48 for M∞=1.8–1.9), without any alteration in captured mass flow. Furthermore, aerodynamic buzz was delayed to engine-face Mach numbers 25–30% lower than the solid-wall configuration. The incorporation of a 19° bleed door resulted in the preservation of this recovery gain, concurrently delivering a further 1% increase and extending the stable operating envelope. The findings of the present study demonstrate that the optimisation of porous plates, in conjunction with active bleed control, provides a robust and Mach-independent means of enhancing the performance and operability of high-speed inlets.