Experimental investigation at supersonic speeds of twin-scoop duct inlets of equal area 3: inlet enclosing 37.2 percent of the maximum circumference of the forebody Page: 3 of 27
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TECH LIBRARY KAFB, NM s-
NACA RM No. A8EO4 0142975
NATIONAL ADVTSCRY COMMITTEE FCO AERONAUTICS
EXPERIMENTAL INVESTIGATION AT SJRSONIC SPEDS OF TWIN-SCOOP
DICT INLETS OF EQUAL AREA. III - ILET ENCLOSIII 37.2 PERGEl
OF TEE MAXIMT CIRCUMFERENCE OF TE FCIREBODY
By Wallace F. Davis and Sherman S. Edwards
A twin-scoop duct inlet that enclosed 37.2 percent of the
forebody circumference was tested at Mach numbers between 1.36
and 2.01. The approach to eac scoop consisted of a ramp that
deflected the flow to create an oblique shock wave in front of
the duct entrance. Tests were made with the duct walls having
slots contiguous to the forebody and immediately behind the inlet
to drain retarded air from the diffusor. The total-pressure
recovery and mass flow through the diffusor were measured during
tests in which the ramp angle, slot dimensions, and angle between
the model axis and the stream direction were altered. Comparison
of the results with those of previous tests of a model having
scoops that enclosed 61.5 percent of the forebody circumference
showed that a greater maximum total-pressure ratio could be
attained with the narrow scoops because the effectiveness of
ramps placed before the inlet continued to higher ramp angles.
Slots in the walls of the ducts contiguous to the forebody and
immediately behind the inlet caused a marked increase in both
pressure recovery and flow stability. At an angle of incidence of
00, the model having scoops with a 120 ramp and slots in the duct
walls attained maximum total-pressure ratios nearly equal to those
of a normal shock wave at Mach numbers less than 1.70; at a Mach
number of 2.01, the pressure recovery was 4 percent less than
that of a normal wave. At angles of attack or yaw of 60, the
decrease in pressure recovery after diffusion was 6 percent or less.
Previous tests at supersonic speeds of an air-induction system
that bad the inlet situated in a region of appreciable boundary layer
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Davis, Wallace F. & Edwards, Sherman S. Experimental investigation at supersonic speeds of twin-scoop duct inlets of equal area 3: inlet enclosing 37.2 percent of the maximum circumference of the forebody, report, July 22, 1948; (digital.library.unt.edu/ark:/67531/metadc57767/m1/3/: accessed January 15, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.