Investigation of the NACA 4-(4)(06)-057-45a and NACA 4-(4)(06)-57-45b Two-Blade Swept Propellers at Forward Mach Numbers to 0.925 Page: 3 of 46
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UNCLASSIFIED
2 R NACA RM L9L05
Investigations of model swept propellers, references 4 and 5, have
shown beneficial effects of sweep from tests at very low advance ratio
and high tip speed. Flight investigations, reference 6, and wind-tunnel
investigations, reference 7, of the same full-scale -swept and unswept
propellers, have shown no significant differences in the performance of
swept and unswept propellers. The small differences between the effi-
ciencies of the swept and unewept propellers may be due to the small
amounts of sweep employed in the outboard sections (150 at the 0.7-radius
station and increasing gradually to 450 at the tip). In addition, the
test results, reference 7, indicate that the tip Mach numbers may not a
have been sufficiently high to encompass the speeds for which sweepback
may have been beneficial. A preliminary investigation, reference 8, to
determine the effect on propeller performance produced by sweeping back
only the tip sections produced encouraging results. The onset of adverse
compressibility effects was delayed approximately 0.12 in tip Mach
number and the maximum efficiency was increased about 2 percent at super-
critical tip Mach numbers compared to the results for a similar uiswept
propeller .
On the basis of the results of reference 8 it was believed that
larger delays in the onset of adverse compressibility effects and high
efficiencies at superorftical speeds could be obtained by employing large
amounts of sweep all along the propeller blades. Consequently, two
propellers were designed having the maximum amount of blade sweep per-
mitted by consideration of blade stresses alone. An investigation of
these swept propellers was made up to a forward Mach number of 0.925 in
the Langley 8'foot high-speed tunnel.
Force-test data and a limited analysis of the results of the investi-
gation of two NACA swept propellers are presented at this time to expedite
publication of this information. Large-scale plots of the basic propeller
characteristics, figures 6 and 7, are available on request to the NACA.
SYMBOLS
b blade width, feet
ozd blade-section design lift coefficient
p power coefficient (P/n3D)
0 trust coeffiolent T/PD%)
CT C~7InUNCLASSIFIED
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Delano, James B. & Harrison, Daniel E. Investigation of the NACA 4-(4)(06)-057-45a and NACA 4-(4)(06)-57-45b Two-Blade Swept Propellers at Forward Mach Numbers to 0.925, report, February 6, 1950; (https://digital.library.unt.edu/ark:/67531/metadc64640/m1/3/: accessed March 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.