Performance characteristics of axisymmetric two-cone and isentropic nose inlets at Mach number 1.90 Page: 2 of 33

                                
TECH LIBRARY KAFB, NM
NACA RM E55F29                                                 0144046
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
RESEARCH MEMORANDUM
PERFORMANCE CHARACTERISTICS OF AXISYNMEIRIC TWO-CONE AND
ISENTROPIC NOSE INLETS AT MACH NUMBER 1.90
By James F. Connors and Rudolph C. Meyer
SUNMARY
An experimental investigation was conducted at a Mach number of
1.90 to determine the over-all performance capabilities of axisymmetric
atwo-cone and isentropic nose inlets in terms of total-pressure recovery,
mass flow, and external drags. At zero angle of attack, the external
drags were separated into their components of cowl pressure, friction,
and additive drags. For angles of attack up to 80, only internal-flow
performance was determined.
At zero angle of attack, critical total-pressure recoveries of 0.94
4       and 0.92 were obtained with the isentropic inlet and with the two-cone
inlet, respectively. With an alternate cowl which had an initially
rapid area expansion, the two-cone inlet also realized a total-pressure
recovery of 0.94. Each inlet captured essentially the maximum stream-
tube of air. At zero angle of attack, stable subcritical operating
ranges of approximately 30 percent of maximum mass flow were obtained.
With suction on the first cone of the two-cone inlet, the range of stable
subcritical operation was increased to 90 percent of maximum mass flow.
The isentropic inlet had a cowl-pressure drag coefficient (0.155
based on maximum frontal area) which was 29 percent larger than that for
the two-cone inlet (0.12). In a thrust-minus-nacelle-drag comparison
based on a typical turbojet application with afterburning, the isentropic
inlet was marginally better (0.6 percent) than the two-cone inlet and
approximately 3 percent better than a representative high-recovery one-
cone inlet.
For angles of attack greater than 50, the pressure recovery and
mass-flow performance of the two-cone inlet was superior to that of the
isentropic inlet.

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