Low-Speed Investigation of the Effects of Angle of Attack on the Pressure Recovery of a Circular Nose Inlet With Several Lip Shapes Page: 4 of 31
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NACA TN 3394
1 average conditions at the exit of the constant-area portion of the
inlet, station 15.00 (A1 = 0.0942 sq ft)
s average conditions at the face of the total-pressure rake, station
36.25 (As = 0.1389 sq ft)
MODEL AND TESTS
The model used in the tests was a streamline body of revolution with
internal ducting and provisions for mounting interchangeable inlet por-
tions at the nose (figs. 1, 2, and 3). The body, which had a maximum
diameter of 12 inches at station 72.00, was mounted on an 8-inch-diameter
vertical strut through which the inlet air flow was exhausted. The total
length of the body was 129 inches.
The inlet portions (fig. 2) were machined from aluminum or brass
castings, and the lip profiles were formed within the boundaries of a
basic sharp-edged inlet. This sharp-edged inlet was formed with a conical
outer surface, tangent to the basic forebody at station 14.118, and with
a cylindrical inner surface with a radius of 2.078 inches extending from
the sharp leading edge, station 9.00, to station 15.00. The angle between
the inner and outer surfaces was about 7-1/20,.
In addition to the sharp-edged inlet, two with circular-arce profiles
and two with elliptical internal and approximately elliptical external
profiles were tested. (The two types of profiles will be referred to as
circular type and elliptical type in the rest of the report.) The profiles
are identified by numbers and letters as shown in figure 2. The number is
approximately equal to the decimal portion of the inlet contraction ratio
while the letter R indicates a circular profile and the letter E, an ellip-
tical profile. Thus, lip 16R had a circular profile and the area encom-
passed by the leading edge was about 16-percent (actually 15.8 percent,
as tabulated in fig. 2) greater than the minimum inlet area. The minimum
inlet area was equal to 12 percent of the maximum frontal area of the body.
The diffusion ratio of the internal duct (As/A1) was 1.474. The
included angle of the unobstructed conical portion of the diffuser - from
station 15.00 to station 32.00 - was about 40,
The air flow through the inlet and subsequent ducting was regulated
by an exhaust pump outside the wind-tunnel test chamber. The rate of inlet
air flow was measured by a calibrated orifice meter, and the loss of total
pressure from the free stream to the simulated turbojet-engine compressor
inlet, station 3 (station 36.25, fig. 1), was measured by a rake consisting
of 24 total-pressure and 4 static-pressure tubes. The total-pressure loss
was measured for mass-flow ratios m/m from 0.6 to choking for each lip
Sfor angles of attack of 0O, 50, 100, 15 , 200, and 250. The test Mach
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Blackaby, James R. Low-Speed Investigation of the Effects of Angle of Attack on the Pressure Recovery of a Circular Nose Inlet With Several Lip Shapes, report, May 1955; (https://digital.library.unt.edu/ark:/67531/metadc57428/m1/4/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.