Effect of Various Methods of Boundary-Layer Control on Performance of V-1710-93 Engine-Stage Supercharger Page: 3 of 28
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NACA I14 No. E6L19
Studies of the air flow through the V-1710-93 engine-stage
supercharger (reference 1) have indicated that the impeller passages
flow only partly full, owing to flow separations along the impeller
front shroud and within the impeller chan Is, Inasmuch as flow
separation can be avoided by either properly removin} or energizing
the boundary layers in the regions of high adverse pressure gradients
(references 2 and 3), an investigation was made on the engine-stage
supercharger impeller to determine the effects of exercising simple
boundary-layer controls on the impeller front shroud and along the
impeller blades. Because no data for estimating the magnitude and
extent of the adverse pressure gradients in an impeller have yet
been acquired, the location of the devices for disturbing the boundary-
layer flow had to be based oan a purely qualitative study of the flow
in impeller channels. The methods used for the boundary-layer con-
trol had to be restricted, to those requiring only small alterations
to the supercharger assembly..
In the first part of this investigation, provision was made for
removal of the boundary layer by suction over the region of greatost
curvature on the impeller front shroud. The air bled through the
impeller front shroud could be removed either by external low-
pressure exhausters or by reoirculation of the air to the inlet duct
immediately before the rotating inlet guide vanes. A standard .
V-1710-93 engine-stage impeller was used in these runs but the struo-
tural features of the bleeding apparatus necessitated the replacement
of the vaned diffuser by a vanoloss diffuser.
The second part of this investigation was concerned, with ener-
gizing the boundary layer at selected points along the blade chord.
Slots were provided at the downstream edge oc the rotating guide
vanes to let air from the high-pressure side of the impeller acti-
vate and disperse the boundary layer on the low pressure side, where
severe adverse pressure gradients are undoubtedly present. After
the effect of these slots had been experimentally determined, addi-
tional slots were provided at a station that was approximately
30 percent of the mean-flow-path length from the blade tips. This
location was selected because it was believed that the unloading
of the impeller blades begins in this neighborhood and because
structural considerations did not permit the slotting of the blades
at a station closer to the blade tips.
These investigations were made i a variable-oomponent super-
charger rig. Over-all adiabatio effiolencies, pressure coeffiolents
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Kohl, Robert C. & Diggs, Donald R. Effect of Various Methods of Boundary-Layer Control on Performance of V-1710-93 Engine-Stage Supercharger, report, January 1947; (digital.library.unt.edu/ark:/67531/metadc63815/m1/3/: accessed January 23, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.