Investigation of the air-flow-regulation characteristics of a translating-spike inlet with two oblique shocks from Mach 1.6 to 2.0 Page: 2 of 16
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TECH LIBRARY KAFB, N
NACA RM E56D23b CONFIDNTIAL 0144086
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
INVESTIGATION OF THE AIR-FLOW-REGULATION CHARACTERISTICS
OF A TRANSLATING-SPIKE INLET WITH TWO OBLIQUE
SHOCKS FROM MACH 1.6 TO 2.0
By J. C. Nettles
The air-flow regulation and pressure recovery of a translating-cone
inlet with a 150 initial conical half-angle and a 100 additional com-
pression was investigated for a range of spike positions at Mach numbers
of 0.6 and 1.6 to 2.0 at zero angle of attack. Performance at the 50
angle of attack was determined at a Mach number of 2.0. The pressure
recovery of the two-shock inlet was essentially the same as the pressure
recovery with a single 250 half-angle cone. For a given spike position
the variation of critical equivalent air flow was small for a Mach num-
ber range of 1.6 to 2.0. Matching the inlet to a turbojet engine indi-
cated that the required translation for the two-shock cone was greater
than for a 250 cone.
The subcritical stability of the two-shock inlet was improved over
that of the single-shock inlet. For spike positions that placed the
first oblique shock inside the cowl lip, the two-shock inlet displayed
a pronounced hysteresis of the minimum stable point, which was not
characteristic of the single-shock inlet.
Regulation of the critical air flow can be achieved by translating
a 250 half-angle cone with a cowl designed for no internal contraction
(refs. 1 to 3). For this type of inlet the conical-shock angle defines
a spike position that will allow a stream tube equal to the cowl area
to enter the diffuser. The variation of the capture stream tube at
critical air flow with spike position can be determined from charts in
reference 4. Tests are required for this type of inlet to determine the
CONFIDENTIAL I 4 6 137
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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/m1/2/: accessed January 21, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.