The design and cascade tests of free-streamline and full-contour 160 degrees turning supersonic-turbine-blade sections Page: 4 of 24
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NACA RM L57F21 5
U upper or convex surface
t stagnation conditions
co inlet free stream
DESIGN OF BLADE SECTIONS
The inlet-air angle was selected as 800 since this value was as
high as was considered practicable. The design of a nozzle that would
provide the high swirl required by a rotor at an inlet angle of 800 would
require modification to methods presently employed to use radial inflow
to increase the tangential velocity component between the nozzle and the
The turning angle was then selected as 1600 on the basis that high
power extraction and a small pressure change across the rotor (impulse-
type rotor) were desirable. An entering Mach number of 1.57 was used
since an existing test section designed for this Mach number was available.
If it is specified that the blade passage has a large enough throat
to pass the starting shock wave of a fixed-geometry upstream nozzle and
that the flow is of the vortex type at the throat, reference 1 shows that
for the Mach number chosen either the design values of the convex-surface
Mach number must be quite high or the blade loading must be comparatively
light. The low blade loadings would result in a flow passage that is
long in comparison with its width and, hence, would have a large wetted
area per unit of mass flow.
Two examples of sections that would just start for an entering Mach
number of 1.57, as determined from figure 13 and table I of reference 1,
are shown in the following table:
Blade Convex surface Concave surface R*U
section M R* v M R L
I 14 1.57 0.7102 4 1.218 0.8532 0.8325
II 27 2.02 0.6137 0 1.000 1.0000 0.6157
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Westphal, Willard R. The design and cascade tests of free-streamline and full-contour 160 degrees turning supersonic-turbine-blade sections, report, August 16, 1957; (digital.library.unt.edu/ark:/67531/metadc63750/m1/4/: accessed February 21, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.