Delano, James B

Harrison, Daniel E

English

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NACA 
RESEARCH MEMORANDUM 
INVESTIGATION OF THE NACA 4-(4)(06)-04 TWO-BLADE 
PROPELLER AT FORWARD MACH NUMBERS TO 0.925
By James B. Delano and Daniel E. Harrison 
Langley Aeronautical Laboratory 
THIS oOcuMErT OW LAN FRO
oA3r Force Base, Va. 
CLA SSIFICATION C 
NATIONAL AVSRY COMMEE 
FOR AERONAU	
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CLASSIFIED 
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This document contains Classified lccforecatton R	 -  affectingthe National Defence of the United 
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u ,90:31 s . Its traesmefsiofl or the 
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0 hI bit ed by law.
ay be reparted 
IAL ADVtSORY COMMI1T
	
	
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R EET, N. W.	 cIvIlian offIcers scsI employees of the Federal 
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TO UNCIASSIFIED
 
DATE: 8-13-54 
L"I 
NATIONAL ADVISORY COMMITTEE 
FOR AERONAUTICS 
WASHINGTON 
October 28, 1949 
CONFIDENTIAL
https://ntrs.nasa.gov/search.jsp?R=19930090382 2020-06-17T04:09:24+00:00Z
NACA RN L9107
	
CONFIDENTIAL 
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

RESEARCH MEMORANDUM 
INVESTIGATION OF THE	 TWO-BLADE 
PROPELLER AT FORWARD MACH NUMBERS TO 0.925 
By James B. Delano and Daniel E. Harrison 
SUMMARY 
Investigation of the NACA 4-(4)(O6)-04 two-blade propeller (design 
thickness ratio, 0.06 at 0.7-radius. station) have been made in the 
Langley 8-foot high-speed tunnel for blade angles from 20 0
 to 700 for 
forward Mach numbers up to 0.925. 
In general, the effects of compressibility on maximum efficiency are 
similar to those reported earlier for the NACA 11_(5)(O8)-O3 propeller. 
The envelope efficiency for the NACA 1 -.( 4)(06)_04 propeller is 10 percent 
higher than that for the NACA 14. (5)(08)_03 propeller at a forward Mach 
number of 0.8.
INTRODUCTION 
Results of the first two phases of a general investigation to study 
the effects of compressibility, design camber, blade sweep, thickness 
ratio, and dual rotation on propeller performance at transonic speeds 
were presented in references 1 and 2. The effects of blade sweep on 
propeller performance constitute the next phase of this general 
investigation. 
In the course of the Investigation to study the effect of blade 
sweep on propeller performance a thin (6-percent thickness ratio) 
straight blade was tested to provide a comparison of results for swept 
and uriswept blades. It was believed that the results obtained for this 
thin propeller would be of immediate interest and consequently are 
presented herein. The Investigation was made for a range of blade angle 
from 200 to 700 for a forward Mach number range from 0.175 to 0.925. 
CONFIDENTIAL
2	 CONFIDENTIAL	 NACA RM L9107 
Force-test results and a limited analysis for only the unswept 
propeller are presented at this time to expedite publication of this 
information. Large--scale plots of the basic propeller characteristics 
(fig. 5) are available on request to the NACA.
	 - 
SYMBOLS 
b blade width, feet 
Cid blade-section design lift coefficient 
C power coefficient (P/Pn 3 'D 1) 
CT thrust coefficient (T/pn2D14) 
D propeller diameter, feet 
b/D blade width ratio 
h maximum thickness. of blade section, feet 
h/b blade thickness ratio 
J advance ratio (Vo/n1) 
M tunnel-datum (forward) Mach number (tunnel Mach number 
uncorrected for tunnel-wall constraint)
Mt	 helical tip Mach number
 (M 11 + 
n	 propeller rotational speed, revolutions per second 
P	 power, foot-pounds per second 
q	 dynamic pressure, pounds per square foot (OV2/2) 
R	 propeller-tip radius.,-feet 
r	 blade-section radius, feet 
T	 thrust, pounds
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NACA RM L9107	 CONFIDENTIAL	 3 
Tc	 thrust disk-loading coefficient (T/2qD2) 
V	 tunnel-datum velocity (tunnel velocity uncorrected for 
tunnel-wall constraint), feet per second 
V0	 equivalent free -air velocity (tinnel-datuni velocity 
corrected for tunnel-wall constraint), feet per second 
blade -section station (r/R) 
section blade angle, degrees 
section blade angle at 0.7 tip radius, degrees 
efficiency	 j 
\CpJ 
- 
TITMIX 
	
maximum efficiency 
P	 air density, slugs per cubic foot 
APPARATUS, METHODS, AND TESTS 
The apparatus and methods described in reference 1 were used in 
this Investigation which was conducted in the Langley 8-foot high-speed 
tunnel. A sketch of the 800-horsepower dynamometer installed in the 
tunnel is shown as figure 1. 
The NACA I-(4)(06)-04 two-blade propeller used in this investi-
gation is the unswept propeller of a family of propellers designed to 
study the effect of blade sweep on propeller characteristics at transonic 
speeds. It utilizes NACA 16-series airfoil sections and was designed 
as a two-blade propeller to produce minimum energy losses (profile drag 
assumed equal to zero) at a blade angle of 600 at the 0.7-radius station 
and at an advance ratio of 3.65. The gaps between the spinner and 
blades were sealed for all operating conditions. Blade-form curves are 
given in figure 2, and a photograph of the blades is shown In figure 3. 
Thrust, torque, and rotational speed were measured throughout the 
- complete operating range of the propeller. For each tunnel Mach number 
the propeller was run at a constant blade angle and the rotational speed 
CONFIDENTIAL
CONFIDENTIAL
	 NACA RN L9107 
was varied. The range of blade angle covered for each forward Mach 
number is given In the following table: 
Mach number, (deg)	 O-7R 
-__IU--UIø 
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______TIIII_ 
JI. 11111_lCD_ 
11111 lID
REDUCTION OF DATA 
Propeller thrust.— Propeller thrust, as used herein, Is defined as 
the shaft tension produced by the spinner—to--tip portion of the blades. 
The method used in determining thrust tares and in evaluating the 
propeller thrust is described In detail in reference 1. 
Propeller torque.— Torque—tare corrections were found to be small 
and depended only on spinner rotational speed. The Indicated torque 
reading was corrected for the spinner tare (a maximum of 1.2 foot—
pounds at 6000 rpm).
CONFIDENTIAL 
NACA EM L9107	 CONFIDENTIAL	 5 
Tunnel-wall correction.- The force-teat data have been corrected 
for the effect of tunnel-wall constraint on velocity at the propeller 
test plane by using the iriethod described in reference 1. These results 
are presented in figure Ii- as the ratio of free-air velocity to the 
tunnel-datum velocity as a function of thrust disk-loading coefficient 
and tunnel-datum Mach number. 
Accuracy
 of results.- Analysis of the accuracy of the separate 
measurements required to define fully the propeller characteristics has 
indicated that errors in the results presented herein are probably less 
than ±1 percent. Repeat runs have shown that the data can be reproduced 
to within ±1 percent.
RESULTS AND DISCUSSION 
The basic propeller characteristics are presented in figure 5. For 
each value of tunnel-datum Mach number M the propeller thrust and power 
coefficients and efficiency are plotted against advance ratio. The 
variation of tip Mach number with advance ratio is also included.. As 
used herein, the tunnel-datum Mach number M Is not corrected for tunnel-
wall constraint. The free 
-air Mach number, however, can be obtained by 
applying the tunnel-wall corrections, presented in figure Ii., to the 
tunnel-datum Mach number. At the high Mach numbers the tunnel-wall 
correction is generally less than 1 percent but, in the exact use of the propeller characteristics presented in figure 5 wherever small changes 
in Mach number produce large changes In propeller characteristics, the 
tunnel-datum Mach number should be corrected to free 
-air Mach number. 
Attention is called to the use of the blade angle 00.1m at the 
0.7-radius station to designate the pitch setting of the blades for 
this investigation. 
Effect of forward Mach number on maximum efficienc y ,- The variation 
of maximum efficiency with forward Mach number is presented in figure 6 
for all the blade angles investigated. Results for a blade angle 
of 700 were obtained only for forward. Mach numbers of 0.75, 0.80, 
and 0.8 because a crack developed in one of the blades and thereby 
prohibited further investigation of this propeller. In general, the 
results are similar to those presented in reference 1 for the 
NACA 14-(5)(08)_03 propeller. 
The maxlmuiii delay In the onset of adverse ,
 compressibility effects 
was obtained for a blade angle of 700 (0.75R 680) in comparison to 
a blade angle (0.75R) of 65° for the NACA 4-(5)(08)_03 propeller. 
This result occurs primarily because of the difference in design pitch. 
CONFIDENTIAL
6	 CONY[DENTIAL	 NACA IM L9107 
Effect of advance ratio and forward Mach number on maximum 
efficiency.- The variation of maximimi efficiency with advance ratio for 
the forward Mach numbers at which the propeller was investigated is 
shown in figure 7. In general, the results are similar to those 
presented in reference 1 for the NACA 14-(5)(08)_03 propeller except 
that the forward Mach number defining the transition from operation at 
high advance ratio to operation at low advance ratio for highest 
efficiencies is higher for the NACA	 (06)-04 propeller (M 0.85). 
These results indicate that thinning the blade makes this transition 
occur at higher forward Mach numbers. Eventually, however, as the 
forward Mach number is increased the propeller will be operating as a 
supersonic type of propeller and the highest efficiencies will then be 
obtained at low values of advance ratio. 
Comparison of envelope efficiency for NACA 4_(I)(06)_Ot. 
and 14_(5)(03)-03 propellers.- The envelope of the maximum-efficiency 
curves in figure 6 is presented in figure 8. A similar envelope curve 
for the NACA 1_-(5)(08)_03 propeller from results of reference 1 is also 
presented in figure 8. At low forward Mach numbers there is little 
difference in envelope efficiency. At supercritical Mach numbers the 
rate of efficiency loss is less for the thin propeller, and at a forward 
Mach number of 0.80 the efficiency of the thin propeller is about 
10 percent higher than for the NACA 14_(5)(08)_03 propeller. These 
differences in efficiency are caused by differences in thickness ratio 
and design pitch. The effect due to differences in design lift coef-
ficient is believed to be secondary, as is shown by the comparison of 
results (reference 2) for the NACA 4-(3)08)-03 and 145)(08)-03 
propellers.
CONCLUSIONS 
Investigations of an NACA 1_( ii)(O6)_0 14- two-blade propeller in the 
Langley 8-foot high-speed tunnel for blade angles of 20 0
 to 70 and 
through a forward Mach number range extending up to 0.925 and comparison 
of results with those for the NACA 4_(5)(08) .03 propeller (NACA 
RM L9G06a) indicate the following conclusions: 
1. In general, the effects of compressibility on maximum efficiency 
are similar to those for the NACA 4-(5)(08)-03 propeller. 
2. At a forward Mach number of 0.8 the envelope efficiency for the 
thin-blade propeller is 10 percent higher than that for the NACA 
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SS 
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NACA RM L9107
	
CONFIDENTIAL	 7' 
I-47)(08)-03 propeller. This higher efficiency is attributed, to the 
combination of reduced thickness ratio and a more favorable pitch 
distribution for the thinner propeller. 
Langley Aeronautical Laboratory 
National Advisory Committee for Aeronautics 
Langley Air Force Base, Va. 
REFERENCES 
1. Delano, James B., and Carmel, Melvin M.: Investigation of the NACA 
1_(5)(08)_03 Two-lade Propeller at Forward Mach Numbers to 0.927. 
NACA EM L9GO6a, 1949. 
2. Delano, James B., and Morgan, Francis C., Jr.: Investigation of the 
NACA 1I_(3)(08)-03 Two-lade Propeller at Forward Mach Numbers 
to 0. 927. NACA EM L9106, 1949. 
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Investigation of the NACA 4-(4)(06)-04 two-blade propeller at forward Mach numbers to 0.925

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