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Results for “PROPELLERS - CONTROLLABLE PITCH”

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1938

Tests of a Contra-propeller for Aircraft

Tests of an 8-blade contra-propeller of 32-inch diameter in combination with a 4-inch, 36-inch diameter adjustable pitch, metal propeller at pitch setting of 15, 25, 35, and 45 degrees at 0.75 R were made. The tests showed a significant increase in effective thrust of the combination over that of the propeller alone for value V/nD somewhat below those for maximum efficiency and without a corresponding increase of power absorbed. From 1/2 percent to 2-1/2 percent in propulsive efficiency was thus gained in this range. In all but one case, however, the peak propulsive efficiency of the combination was found to be from 1 to 2 percent less than that of the propeller alone. Counter torque on the contra-propeller amounted to about 50 percent of the propeller torque.

Benson, William M↗
NASA NTRS1932

Full-Scale Tests of Metal Propellers at High Tip Speeds

This report describes tests of 10 full-scale metal propellers of several thickness ratios at various tip speeds up to 1,350 feet per second. The results indicate no loss of efficiency up to tip speeds of approximately 1,000 feet per second. Above this tip speed the loss is at a rate of about 10 per cent per 100 feet per second increase relative to the efficiency at the lower speeds for propellers of pitch diameter ratios 0.3 to 0.4. Propellers having sections of small thickness ratio can be run at slightly higher speeds than thick ones before beginning to lose efficiency.

Wood, Donald H↗
NASA NTRS1927

Tests on thirteen navy type model propellers

The tests on these model propellers were undertaken for the purpose of determining the performance coefficients and characteristics for certain selected series of propellers of form and type as commonly used in recent navy designs. The first series includes seven propellers of pitch ratio varying by 0.10 to 1.10, the area, form of blade, thickness, etc., representing an arbitrary standard propeller which had shown good results. The second series covers changes in thickness of blade section, other things equal, and the third series, changes in blade area, other things equal. These models are all of 36-inch diameter. Propellers A to G form the series on pitch ratio, C, N. I. J the series on thickness of section, and K, M, C, L the series on area. (author)

Durand, W F↗
NASA NTRS1929

Full-Scale Wind-Tunnel Tests of a Series of Metal Propellers on a VE-7 Airplane

An adjustable blade metal propeller was tested at five different angle settings, forming a series varying in pitch. The propeller was mounted on a VE-7 airplane in the twenty-foot propeller research tunnel of the National Advisory Committee for Aeronautics. The efficiencies were found to be from 4 to 7 per cent higher than those of standard wood propellers operating under the same conditions. The results are given in convenient form for use in selecting propellers for aircraft.

Weick, Fred E↗
NASA NTRS1945

Effect of Propeller-Axis Angle of Attack on Thrust Distribution over the Propeller Disk in Relation to Wake-Survey Measurement of Thrust

Tests were made to investigate the variation of thrust distribution over the propeller disk with angle of pitch of the propeller thrust axis and to determine the disposition and the minimum number of rakes necessary to measure the propeller thrust. The tests were made at a low Mach number for a low and a high blade angle with the propeller operating at three small angles of pitch, and some of the tests were repeated at a higher Mach number. The data obtained show that, for small angles of pitch, large changes occur in the energy distribution in the wake which prohibit the use of a single survey rake for thrust measurement in flight tests and limit the use of a single rake in wind-tunnel tests. Under certain conditions, the energy distribution in the wake took on a symmetrical form and two diametrically opposed survey rakes were shown to be satisfactory for obtaining propeller thrust. (author)

Pendley, Robert E↗
NASA NTRS1928

Characteristics of Five Propellers in Flight

This investigation was made for the purpose of determining the characteristics of five full-scale propellers in flight. The equipment consisted of five propellers in conjunction with a VE-7 airplane and a Wright E-2 engine. The propellers were of the same diameter and aspect ratio. Four of them differed uniformly in thickness and pitch and the fifth propeller was identical with one of the other four with exception of a change of the airfoil section. The propeller efficiencies measured in flight are found to be consistently lower than those obtained in model tests. It is probable that this is mainly a result of the higher tip speeds used in the full-scale tests. The results show also that because of differences in propeller deflections it is difficult to obtain accurate comparisons of propeller characteristics. From this it is concluded that for accurate comparisons it is necessary to know the propeller pitch angles under actual operating conditions. (author)

Crowley, J W , Jr↗
NASA NTRS1939

Tandem Air Propellers - II

Tests of three-blade, adjustable-pitch counterrotating tandem model propellers, adjusted to absorb equal power at maximum efficiency of the combination, were made at Stanford University. The aerodynamic characteristics, for blade-angle settings of 15, 25, 35, 45, 55, and 65 degrees at 0.75R of the forward propeller and for diameters spacings of 8-1/2, 15 and 30% were compared with those of three-blade and six-blade propellers of the same blade form. It was found that, in order to realize the condition of equal power at maximum efficiency, the blade angles for the rear propeller must be generally less than for the forward propeller, the difference increasing the blade angle. The tests showed that, at maximum efficiency, the tandem propellers absorb about double the power of three-blade propellers and about 8% more power than six-blade propellers having the pitch of the forward propeller of the tandem combination. The maximum efficiency of the tandem propellers was found to be from 2-15% greater than for six-blade propellers, the difference varying directly with blade angle. It was also found that the maximum efficiency of the tandem propellers was greater than that of a three-blade propeller for blade angles at 0.75R of 25 degrees or more. The difference in maximum efficiency again varied directly with blade angle, being about 9% for 65 degrees at 0.75R.

Lesley, E. P.↗
NASA NTRS1932

The Effect of Small Angles of Yaw and Pitch on the Characteristics of Airplane Propellers

This report presents the results of wind tunnel tests to determine the effect on the characteristics of a propeller of inclining the propeller axis at small angles to the relative wind. Tests were made of a full-scale propeller and fuselage combination at four angles of yaw (0 degree, +5 degrees, +10 degrees, +15 degrees), and of a model propeller, nacelle, and wing combination of five angles of pitch (-5 degrees, 0 degree, +5 degrees, +10 degrees and +15 degrees). The results of the full-scale tests of a propeller and fuselage, without a wing, show that the effect on the propeller performance is small. Similar results are shown by the model test data except that where the propeller is directly in front of the wing there is an appreciable decrease in effective thrust and propulsive efficiency with increase of angle of pitch.

Freeman, Hugh B↗
NASA NTRS1937

Tandem Air Propellers

Tests of 2-blade, adjustable-pitch, counterrotating tandem model propellers, adjusted to absorb equal power at maximum efficiency, were made at Stanford University. The characteristics, for 15 degrees, 25 degrees, 35 degrees, and 45 degrees pitch settings at 0.75 R of the forward propeller and for 8 1/2%, 15% and 30% diameter spacings, were compared with those of 2-blade and 4-blade propellers of the same blade form. The tests showed that the efficiency of the tandem propellers was from 0.5% to 4% greater than that of a 4-blade propeller and, at the high pitch settings, not appreciable inferior to that of a 2-blade propeller. It was found that the rear tandem propeller should be set at a pitch angle slightly less than that of the forward propeller to realize the condition of equal power at maximum efficiency. Under this condition the total power absorbed by the tandem propellers was from 3% to 9% more than that absorbed by the 4-blade propeller and about twice that absorbed by a 2-blade propeller.

Lesley, E.P.↗
NASA NTRS1921

Dependence of propeller efficiency on angle of attack of propeller blade

In order to determine the maximum and the most favorable pitch for a propeller, it was found desirable to investigate the dependence of propeller efficiency on the angle of attack of the propeller blade. The results of a few experiments are given to show that propeller blades conduct themselves just like airplane wings with reference to the dependence of their efficiency on their angle of attack.

PROPELLERS - EFFICIENCY↗
NASA NTRS1939

Tandem Air Propellers

Tests of 2-blade, adjustable-pitch, counter rotating tandem model propellers, adjusted to absorb equal power at maximum efficiency, were made at Stanford University. The characteristics, for 15 degrees, 25 degrees, 35 degrees, and 45 degrees pitch settings at 0.75 R of the forward propeller and for 8-1/2 percent, 15 percent, and 30 percent diameter spacings, were compared with those of 2-blade and 4-blade propellers of the same blade form. The tests showed that the efficiency of the tandem propellers was from 0.5 percent to 4 percent greater than that of a 4-blade propeller and, at the high blade-angle settings, not appreciably inferior to that of a 2-blade propeller. It was found that the rear tandem propeller should be set at a blade angle slightly less than that of the forward propeller to realize the condition of equal power at maximum efficiency. Under this condition the total power absorbed by the tandem propellers was from 3 percent to 9 percent more than that absorbed by the 4-blade propeller and about twice that absorbed by a 2-blade propeller.

Lesley, E P↗
NASA NTRS1937

Air Propellers in Yaw

Report presents the results of tests conducted at Stanford University of a 3-foot model propeller at four pitch settings and at 0 degree, 10 degrees, 20 degrees, and 30 degrees yaw. In addition to the usual propeller coefficients, cross-wind and vertical forces and yawing, pitching, and rolling moments were determined about axes having their origin at the intersection of the blade axis and the axis of rotation. The tests showed that the maximum efficiency was reduced only slightly for angles of yaw up to 10 degrees but that at 30 degrees yaw the loss in efficiency was about 10 percent. In all cases the cross-wind force was found to be greater than the cross-wind component of the axial thrust. With a yawed propeller an appreciable thrust was found for v/nd for zero thrust at zero yaw. Yawing a propeller was found to induce a pitching moment that increased in magnitude with yaw.

Lesley, E P↗
NASA NTRS1932

Comparison of Full-Scale Propellers Having R.A.F.-6 and Clark Y Airfoil Sections

In this report the efficiencies of two series of propellers having two types of blade sections are compared. Six full-scale propellers were used, three having R. A. F.-6 and three Clark Y airfoil sections with thickness/chord ratios of 0.06, 0.08, and 0.10. The propellers were tested at five pitch setting, which covered the range ordinarily used in practice. The propellers having the Clark Y sections gave the highest peak efficiency at the low pitch settings. At the high pitch settings, the propellers with R. A. F.-6 sections gave about the same maximum efficiency as the Clark Y propellers and were more efficient for the conditions of climb and take-off.

Freeman, Hugh B↗
NASA NTRS1990

Propeller/fan-pitch feathering apparatus

A pitch feathering system for a gas turbine driven aircraft propeller having multiple variable pitch blades utilizes a counter-weight linked to the blades. The weight is constrained to move, when effecting a pitch change, only in a radial plane and about an axis which rotates about the propeller axis. The system includes a linkage allowing the weight to move through a larger angle than the associated pitch change of the blade.

Schilling, Jan C.↗