Bleed Holes Research Articles

Bleed System Design Technology for Supersonic Inlets

A boundary-layer bleed system design procedure for supersonic inlets, with emphasis on the selection of bleed hole geometry, is described. Available experimental bleed hole performance data, coupled with bleed drag calculations, show that holes with shallow inclination are superior to holes normal to the surface in terms of over-all inlet performance. Recent test results from large-scale inlet models indicate that bleed hole size, bleed hole length, and boundary-layer velocity profile upstream of the bleed region are important parameters in the design of an effective and efficient bleed system. Nomenclature A = area A/A* = sonic area ratio Ca - drag coefficient D = bleed hole diameter HI - boundary-layer shape factor L/D = bleed hole length to diameter ratio m = mass flow M = Mach number P = pressure Q = sonic mass flow coefficient; ratio of actual mass flow to theoretical maximum mass flow at local total pressure and temperature X/D = spacing between rows of bleed holes Y/D - bleed hole spacing a = bleed hole inclination to inlet surface /8 = exit nozzle ramp angle 6* = boundary-layer displacement thickness rj = bleed efficiency factor Subscripts bl = bleed epl = bleed exit plenum / = cowl lip loc = local condition pi — bleed plenum se = sonic exit to — freestream stagnation condition 00 = freestream

Advanced supersonic inlet technology.

Recently, relatively new analytical procedures have been successfully used to design bleed systems for mixed-compression inlets designed to operate efficiently up to Mach number 2.65. The procedures used constitute a major advance in inlet technology by offering a promising approach to attain high internal and external performance for mixed-compression inlets that operate over a large supersonic Mach number range. Unfortunately, there is a lack of data describing bleed hole performance characteristics to verify these procedures at high Mach numbers. This paper briefly discusses the analytical procedures for designing advanced inlet systems and suggests facility modifications wherein the procedures can be verified on large-scale inlet models up to approximately Mach number 4.5.