Porous and microporous honeycomb composites as potential boundary-layer bleed materials

Results of an experimental investigation are presented in which the use of porous and microporous honeycomb composite materials is evaluated as an alternate to perforated solid plates for boundary-layer bleed in supersonic aircraft inlets. The terms "porous" and "microporous," respectively, refer to bleed orifice diameters roughly equal to and much less than the displacement thickness of the approach boundary-layer. A baseline porous solid plate, two porous honeycomb, and three microporous honeycomb configurations are evaluated. The performance of the plates is characterized by the flow coefficient and relative change in boundary-laye r profile parameters across the bleed region. The tests were conducted at Mach numbers of 1.27 and 1.98. The results show that the porous honeycomb is not as efficient at removing mass compared to the baseline. The microporous plates were about equal to the baseline with one plate demonstrating a significantly higher efficiency. The microporous plates produced significantly fuller boundarylayer profiles downstream of the bleed region for a given mass flow removal rate than either the baseline or the porous honeycomb plates.