Performance of Twin-Duct Variable-Geometry Side Inlets at Mach Numbers of 1.5 to 2.0 Page: 2 of 34
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NATIONAL ADVISORY COMtTTEE FOR AERONAUTICS
PERFORMANCE OF TWIN-DUCT VARIABLE-GEOMETRY SIDE
INLETS AT MACH NUMBERS OF 1.5 TO 2.0
By Richard A. Yeager, Milton A. Beheim, and John L. Klann
The performance of a twin-duct air-intake system mounted on the sides
of a 1/8-scale fuselage forebody model of a proposed aircraft was inves-
tigated at free-stream Mach numbers of 1.5 to 2.0 over a range of angles
of attack and yaw. The inlets were of the double-ramp type and were
tested at 00 and -5 cant with respect to the fuselage centerline. The
test was conducted with several second-ramp angles and at several second-
ramp longitudinal positions along the first-ramp surface. Various meth-
ods of second-ramp surface boundary-layer removal were also investigated.
For a particular second-ramp position a slot in the second ramp in-
side the cowl increased the subcritical stability over that obtained with-
out boundary-layer removal, while perforations in the second ramp just up-
stream of the cowl had no effect on stability. Little change in pressure
recovery was obtained by employing either method of boundary-layer control.
Canting the inlets from 0 to -5 improved the total-pressure recovery at
positive angles of attack greater than 2o0 and increased subcritical sta-
bility at all the Mach numbers investigated. At Mach number 2.0 and 20
angle of attack, the -50-cant inlet yielded a peak pressure recovery of
86 percent and a critical mass-flow ratio of 84 percent with 28 percent
stability. The distortion was about 7 percent for critical and subcriti-
cal operation. Asymmetrical duct flow occurred only during operation
where normal-shock oscillations were observed at angle of attack but for
all operating conditions at angle of yaw. The addition of canards on the
fuselage upstream of the 00-cant inlets increased the total-pressure re-
covery and reduced distortion at all positive angles of attack.
An investigation has been conducted in the Lewis 8- by 6-foot super-
sonic wind tunnel to determine the performance of a twin-duct air-intake
system mounted on the sides of a 1/8-scale fuselage forebody model of a
proposed aircraft. The fuselage inlet configuration differed from that
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Yeager, Richard A.; Beheim, Milton A. & Klann, John L. Performance of Twin-Duct Variable-Geometry Side Inlets at Mach Numbers of 1.5 to 2.0, report, January 21, 1957; (https://digital.library.unt.edu/ark:/67531/metadc63208/m1/2/?rotate=270: accessed March 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.