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

A two-stage numerical study is conducted in order to enhance the functionality of the bleed system of a single-ramp, external-compression inlet. Initially, three-dimensional RANS simulations of eight representative perforated plates are utilized 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 5(3) full-factorial design (hole diameter, length-to- diameter ratio L/D, and porosity) comprising 125 geometries is then analyzed for the entry plate with the response-surface methodology, Shannon-entropy weighting, and multi-objective desirability optimization. The analysis of the variance demonstrates that porosity and L/D account for in excess of 95% of the sum of squares of the mass- flow ratio, drag coefficient and discharge coefficient. Conversely, the diameter is found to be statistically insignificant over the tested range. The optimization returns a compact entry-plate with the optimum L/D of 1.0 and the porosity of 0.20. Repeating the procedure for the exit plate, following the elimination of the weakly sensitive discharge coefficient, the optimum L/D of 0.25 and the porosity of 0.47 are obtained. These two optimized plates result in the enhancement of total-pressure recovery by 2.2- 2.3% at the baseline buzz-onset points (M-EF = 0.46 for M-infinity = 1.6 and M-EF = 0.48 for M-infinity = 1.8-1.9), without any change in the captured mass flow rate. Furthermore, the aerodynamic buzz is delayed to the engine-face Mach numbers, 25-30% lower than the solid-wall configuration. The 19 degrees bleed door results in the preservation of the recovery gain, concurrently delivering a further 1% increase and extending the stable operating envelope. The optimization of the porous plates with active bleed control provides a robust and Mach-independent means of enhancing the performance and operability of high-speed inlets.