A Comparison of Several Systems of Boundary-Layer Removal Ahead of a Typical Conical External-Compression Side Inlet at Mach Numbers of 1.88 and 2.93 Page: 3 of 60
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NACA RM E53FI6
INTRODUCTION
The use of the ram-type boundary-layer scoop (straight leading
edge with enclosed sides) as a means of removing the boundary layer
ahead of conical external-compression side inlet configurations at Mach
numbers of 1.88 and 2.93 has been reported in references I and 2,
respectively. The inlet for these tests was mounted on a flat plate
at zero angle of attack and yaw with respect to the local free stream.
It was observed that, with sufficient removal of the boundary layer
ahead of the inlet, total-pressure recoveries comparable with those of
nose inlets could be obtained at Mach 1.88; while at Mach 2.93 the
total-pressure recovery was slightly lower than that obtained with a
nose inlet for the case considered. Some recent investigations of other
side inlet configurations using boundary-layer-removal scoops installed
on the fuselage of a proposed supersonic airplane are reported in refer-
ences 3 to 5.
The investigations reported in references 1 .and 2 with the ram-
scoop removal system have indicated that while the inlet performance
was acceptable with sufficient removal of the boundary layer, reduction
of the amount of boundary-layer removal severely reduced the inlet
total-pressure recovery. If the reduction in removal occurred through
a reduction in the bQundary-layer-scoop mass flow with resultant spil-
lage into the inlet, an additional adverse effect of unstable operation
was encountered.
In reference 1 several alternative systems of boundary-layer
removal wherein the boundary layer was diverted around the inlet were
investigated briefly. For those tests the boundary layer was simply
allowed to spill to the sides around the inlet, either beneath the
splitter plate separating the inlet and boundary-layer flows or through
inlet-cowl slots. Inlet total-pressure recovery for all-variations of
boundary-layer removal investigated showed improvements over that
obtained with the ducted scoop when no boundary layer was allowed to
enter the duct (i.e., low scoop mass-flow ratio). The swept-leading-
edge splitter plate with complete blockage of the flow downstream of
the inlet and beneath the splitter plate was the most effective of the
variations investigated. This configuration successfully diverted the
boundary layer around the inlet.
For the designer who wishes to use the air obtained from boundary-
layer removal for cooling or as a source of secondary air in ejector
designs, the swept-leading-edge boundary-layer scoop with ducting there-
fore appeared promising; pressure recovery obtained with maximum removal
of the boundary layer should be equivalent to that previously obtained
using a ram scoop, and the inlet pressure recovery should be less sensi-
tive to boundary-layer scoop mass flow because of the ability of the_ _ __
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Piercy, Thomas G. & Johnson, Harry W. A Comparison of Several Systems of Boundary-Layer Removal Ahead of a Typical Conical External-Compression Side Inlet at Mach Numbers of 1.88 and 2.93, report, September 4, 1953; (https://digital.library.unt.edu/ark:/67531/metadc59665/m1/3/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.