Allen, J. L., Simon, P. C.
The performance of semicone inlets located on a fuselage was investigated at Mach numbers of 0, 0.63, and 1.5 to 2.0. The inlets utilized a half spike for compression and ram-type boundary-layer removal scoops. Peak pressure recoveries from 0.86 to 0.95 were obtained at Mach numbers from 2.0 to 1.5 at an angle of attack of 3 degrees with complete removal of the fuselage boundary layer forward of the inlets. Translating the semicone to an aft position increased the captured mass flow with no change in pressure recovery at a Mach number of 1.5; however, at Mach numbers of 1.9 and 2.0, the stable subcritical operating range of the inlet was severely limited by pulsing. Sweeping back the leading edge of the splitter plate used to separate the boundary layer and flow entering the main inlet increased the stable subcritical operating range of the inlet at a Mach number of 2.0 for angles of attack from 0 degrees to 9 degrees. At a Mach number of 0.63, a pressure recovery of 0.97 was attained for critical flow. At zero forward velocity, a large vena contracta was observed which may limit the performance at take-off unless auxiliary inlets are used.
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