Investigation of the air-flow-regulation characteristics of a translating-spike inlet with two oblique shocks from Mach 1.6 to 2.0 Page: 3 of 16
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NACA RM E56D23b
If two-shock compression is employed, the condition of the flow
field behind the first conical shock hinders the estimation of the shape
and angular movement of the second shock. As a consequence, the vari-
ation of critical air flow with spike position and flight Mach number
can not be readily determined. It is also usually desirable from the
standpoint of pressure recovery to operate the inlet so that the second
shock does not fall inside the cowl lip.
In order to obtain data on the air-flow-regulation characteristics
of a translating-cone two-shock inlet, an extension having a 150 half-
angle was added to the 250 half-angle inlet (ref. 2). The investigation
was conducted in the Lewis 8- by 6-foot tunnel from Mach 1.6 to 2.0.
APPARATUS AND PROCEDURE
The general layout of the model is shown in figure 1. The model
support strut was so arranged that a 50 angle of attack could be obtained
by rotating the entire assembly relative to the tunnel ceiling. Figure
2 presents the variation of the flow-area ratio of the subsonic diffuser
in terms of the initial hydraulic diameter for the foremost and rearmost
spike positions. The area ratio for a 30 half-angle conical diffuser is
shown for comparison (fig. 2). The particular cowl used in these tests
was contoured to provide approximately 1 hydraulic diameter of essen-
tially constant flow area at the subsonic diffuser inlet.
The flow through the diffuser was controlled by a translating plug
at the exit. Air flow was calculated from the exit area and an average
static pressure which was measured at- a station ahead of the plug.
Pressure recovery was determined as an average of the total pressure
measured at a station approximately 32 cowl diameters downstream of the
Pulsing was detected by observation of a schlieren apparatus and
pressure transducers connected to an oscilloscope.
The juncture between the 150 cone and the 250 cone was selected to
cause intersection of both oblique shocks at the cowl lip at a free-
stream Mach number of 2. The curvature of the second shock was approxi-
mated. This method was based upon a linear interpolation of the Mach
number with the ray angle from the cone surface to the first-oblique
shock and upon the assumption that the deflection through the second
shock was constant (ref. 5).
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Nettles, J. C. Investigation of the air-flow-regulation characteristics of a translating-spike inlet with two oblique shocks from Mach 1.6 to 2.0, report, July 24, 1956; (digital.library.unt.edu/ark:/67531/metadc53048/m1/3/: accessed January 20, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.