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National Advisory Committee for Aeronautics, Report - An Investigation of Single and Dual Rotation Propellers at Positive and Negative Thrust, and in Combination with an with an NACA 1-Series D-Type Cowling at Mach Numbers up to 0.84

An investigation has been made to determine the aerodynamic
characteristics of the NACA 4-(5) (Um—041 four—blade, single—
rotation propeller and the NACA 4—(5) (05)—037' sin:- and
eight-blade, dual-rotation propellers in combination with
various spinners and NACA D-type spinner-cowling combina-
tions at hIach numbers up to 0.84. Propeller force characteris-
tics, local velocity distributions in the propeller planes, inlet
pressure recoveries, and static-pressure distributions on the
cowling surfaces were measured for a wide range of blade
angles, advance ratios, and inlet-velocity ratios.

Included aredata showing: (a) the efi'ect of extended cylindrical spinners
on the characteristics of the single-rotation propeller, (b) the
eflect of variation of the difierence in blade angle setting between
the front and rear components of the dual-rotation propellers,
(c) the negative- and static-thrust characteristics of the propellers
with 1-series spinners, and (d) the ejects of ideal— and platfonn-
type propeller-spinner junctures on the pressure-recovery
characteristics of the single-rotation propeller-spinner-cowling
combination. All tests were made at an angle of attach: of 0°,
and, except for the static-thrust data, were made at Reynolds
numbers of 1.5 and 1.0 million per foot, respectively, for the
single- and dual-rotation propeller—spinner-cowling combina-
tions. A description of the MOO-horsepower propeller dyna—
mometer used to obtain the data is also included in the report.

The highest Mach number at which the propellers with the
NACA 1—series spinners operated without marked compres-
sibility losses was about 0.7. The maximum efliciencies of the
propellers at this Mach number were ’79, 88, and 82 percent,
respectively, for the four-, sin, and eight-blade propellers at a
blade angle of 65°. The results indicate that for operation of
the propellers at Mach numbers greater than about 0.8, highest
efiiciencies would be obtained at lower advance ratios and lower
blade angles.

Substantially higher efliciencies were obtained for the NACA
4—(5) (013)—041 propeller with extended cylindrical spinners as
compared to those obtained for the propeller with an NACA
1-_series spinner, amounting to as much as 15 percent at the
highest Mach number and blade angle of the tests. Due to the
apparent increase in propeller thrust associated with favorable
interference ejects of the cowling on the flow field at the propeller,
maximum eflioiencies obtained with the single— and dual-rotation
propellers operating in the presence of the cowlings were
higher at all Mach numbers and blade angles than those for the
isolated propeller-spinner combinations.