I 

i 

, 

NASA Technical Memorandum 101480 

Cruise Noise of the SR-2 

Model in a Wind Tunnel 

tliASA-Ta-lOl480) CRUISE NOISE OF THE SR-2 N09 -2 48 86 

PROPELLER BODEL IN il RIND TUNNEL ,lMASA. 

Lewis Research Center) 29 p CSU 208 

Propeller 

Unclas 

G3/71 0204417 

James H. Dittmar 

Lewis Research Center 

Cleveland, Ohio 

April 1989 
CRUISE NOISE OF THE SR-2 PROPELLER MODEL IN A WIND TUNNEL 

James H. Di ttmar 

National Aeronautics and Space Administration 

Lewis Research Center 

Cleveland, Ohio 44135 

SUMMARY 

Noise data on the SR-2 model propeller were taken in the NASA Lewis 

Research Center 8- by 6-Foot Wind Tunnel. 

with increasing helical tip Mach number to a peak level at a helical tip Mach 

number of about 1.05; then it remains the same or decreases at higher helical 

tip Mach numbers. This behavior, which has been observed with other propeller 

models, points to the possibility of using higher propeller tip speeds to limit 

airplane cabin noise while maintaining high flight speed and efficiency. Noise 

comparisons of the straight-blade SR-2 propeller and the swept-blade SR-7A pro- 

& peller showed that the tailored sweep of the SR-7A appears to be the cause of 

both lower peak noise levels and a slower noise increase with increasing helical tip Mach number. 

The maximum blade passing tone rises 

INTRODUCTION 

noi se 

it may 

prope 1 

ducers 

(refs. 

pel ler 

ers in 

this p 

Advanced turboprop-powered aircraft offer the potential for significant 

fuel savings over equivalent core technology turbofan-powered aircraft. The 

rom advanced high speed propellers is of present concern since at cruise 

pose an environmental problem in the airplane cabin. A number of model 

ers have previously been tested for acoustics by using pressure transembedded in the ceiling of the NASA Lewis 8- by 6-Foot Wind Tunnel 

1 to 5). The noise of the large-scale advanced propfan (LAP) model proSR-7A, was measured in this wind tunnel by embedding pressure transduca plate suspended from the tunnel ceiling (refs. 6 and 7). The use of 

ate permits better angular determination of the propeller directivity 

and, because of the thinner plate boundary layer, less boundary layer refraction than the wall measurements. The thickness-to-wavelength ratio for the 

plate boundary layer-to-model propeller sound is closer to that of the fuselage 

boundary layer-to-full size propeller-in-flight sound than is that of the ceiling boundary layer-to-model propel ler sound. Therefore, the data from the 

plate can more easily be scaled to airplane conditions. 

During the testing of the swept SR-7A model (refs. 6 and 7>, a limited 

amount of data on the straight-blade SR-2 propeller model was taken. By using 

the suspended plate, data with better resolution and less boundary layer 

refraction than the previously taken SR-2 data (ref. 1) was obtained. The data 

were intended to show how the SR-2 propeller noise varies with helical tip Mach 

number and, by comparison with the SR-7A data, the effect of sweep on propeller 

noise. This report presents the results of the SR-2 testing. 

APPARATUS AND PROCEDURE 

The SR-2 propeller, which is a straight-blade propeller nominally 62.2 cm 

(24.5 in.) in diameter, was tested for acoustics in the NASA Lewis 8- by 6-Foot 
Wind Tunnel. Table I shows some of the design characteristics of this propeller. A plan view of the wind tunnel is shown in figure l(a>, and a photograph 

of the SR-2 propeller in the test section is shown in figure l(b>. The propeller was tested at its nominal design blade setting angle of 59", measured at 

the 314 radius location. The propeller was operated at nominal advance ratios 

ranging from 2.75 to 3.85 for tunnel Mach numbers from 0.6 to 0.8, and at nominal advance ratios ranging from 3.06 to 3.65 for tunnel Mach numbers of 0.85 

and 0.9. 

A plate was firmly attached to the tunnel ceiling, 0.3 propeller diameters 

from the propeller tip, and transducers were installed flush with the plate 

surface to measure the noise of the propeller. A photograph of this plate with 

the SR-7A propeller (refs. 6 and 7) is shown in figure 2(a), and a sketch of 

the installed plate is shown in figure 2(b>. Twelve transducers were installed 

on the plate centerline, which was directly above the propeller centerline. 

The transducers' locations are shown in figure 2(b). The signals from the 

pressure transducers were recorded on magnetic tape, and narrowband spectra 

were obtained for each of the test points. Typically, the narrowband range was 

0 to 10 000 Hz with a bandwidth of 32 Hz. 

RESULTS AND DISCUSSION 

Noise data were taken for the experimental test conditions listed in 

table 11. The advance ratio J, the power coefficient Cp, and the helical tip 

Mach number Mht are presented in this table. Some limited additional aerodynamic data from previous testing is available in reference 8. The acoustic 

data for the first eight harmonics of the propeller blade passing tone are presented, as measured, in tables I11 to IX. 

Noise Variation with Helical Tip Mach Number 

The propeller was tested at a fixed blade setting angle of 59" for all 

the various tunnel axial Mach numbers. The peak blade passing tones measured 

on the plate were plotted as a function of helical tip Mach numbers (see 

fig. 3). These plots are at a constant advance ratio, so the helical tip Mach 

number was varied by changing the propeller tip speed and tunnel Mach number. 

Data for five advance ratios were plotted. 

As figure 3 shows, the maximum blade passing tone rises with increasing 

helical tip Mach number to a peak level; then it remains the same or decreases 

with increasing helical tip Mach numbers. This behavior has been observed 

previously, particularly with the swept-blade SR-7A propeller model (refs. 6 

and 7). This same noise variation for the straight-blade SR-2 propeller 

implies that faster rotating propellers may be useful as a method to limit 

cabin noise while maintaining high flight speed and efficiency. 

At some conditions a hump, consisting of the peak, a reduction from the 

peak, and then an increase with further increases in helical tip Mach number, 

is seen in the curve, (refs. 6 and 7). This hump is shown in figure 3(b> for 

an advance ratio of 3.5. As noted in references 6 and 7, the hump may represent a different noise mechanism. Two of the possibilities proposed were a 

"quadrupole noise" (ref. 9) and shock wave pressure rise (ref. 10). Another 

2 
possibility, presented by Hanson in reference 11, is that the flow around the 

propeller tip changes the noise production in this region. 

Directivity 

.- Blade passing tone levels as functions of angular position (i.e., direcvities) for the SR-2 propeller are shown in figure 4 for the design advance 

tio (J = 3.06) condition at the seven Mach numbers tested. The peak noise 

vels occur at or just behind the plane of rotation. 

The directivities at most of the Mach numbers are similar in shape, with 

2 noted exception at M = 0.7 where the directivity is much flatter. At 

= 0.7 the forward noise is higher than at either M = 0.65 or M = 0.75, and 

! noise at the forward-most position of around 50" is higher than at any 

ier Mach number. A similar observation was made for the SR-7A propeller 

fs. 6 and 7). For both of these propellers, the helical tip Mach number 

M = 0.7 was approximately 1.0, so the forward noise increase may be some 

nsient transonic effect. Since the far-forward noise levels are higher at 

0.7 than at any other Mach number, this may cause a cabin noise peak at 

far-forward angles during an airplane acceleration to M = 0.8 cruise. 

Comparison with Previous SR-2 Data 

Four pressure transducers embedded in the tunnel ceiling (ref. 1) were 

iously used to gather limited experimental data on the SR-2 propeller at a 

blade setting angle. In those experiments the propeller was tested only 

ts design condition; that is, an advance ratio equal to 3.06 and a tunnel 

number equal to 0.8. Figure 5 shows the four transducer blade passing 

j on the present directivity plot. The data from reference 1 were cor- 

?d (1) by adding 6 dB to compensate for the calibration error identified 

!ference 4 and (2) by using 20 log of the distance from the propeller cenne to adjust the ceiling data to the plate position - an addition of 8 dB 

e data noted in reference 4. The effect of boundary layer refraction on 

orward transducers is seen in figure 5. The data from the two forward 

ng transducers show lower noise levels than the plate data because of the 

er refraction. Reference 4 noted that for aft angles greater than about 

there is little or no refraction. Here, the ceiling and plate aft data 

-e very well. For the initial data of reference 1, only four transducers 

Ised; obviously, this set of data missed the peak noise level because 

was no transducer at 100". 

Compari son with SR-7A Data 

Noise variation with helical tip Mach number. - The SR-7A propeller's 

(refs. 6 and 7) leadinq edqe sweep was tailored to provide a noise reduction at 

the cruise condition (i.e.1 M = 0'.8 and J = 3.06): Comparison of the SR-7A 

propeller noise with that of the straight blade SR-2 propeller yields a measure 

of the no se reduction due to the tailored sweep. 

angles of 60.1" for the SR-7A and 59" for the SR-2, the propeller had similar 

aerodynam c performances. 

cient C, 

At design blade setting 

See, for example, the curves of the power coeffias a function of tunnel Mach number, for the SR-2 at 59" and for 
the three tested SR-7A blade setting angles, shown in figure 6 for an advance 

ratio of 3.06. Figure 7 compares the variation of noise with helical tip Mach 

number for the two propellers for advance ratios of 3.75, 3.5, 3.25, 3.06, and 

2.75. 

The SR-7A propeller shows less peak blade passing tone noise at all of 

the advance ratios shown in figure 7, with a maximum difference of about 5 dB 

at the design advance ratio of 3.06 and helical tip Mach number of 1.1. In 

most cases the noise for the two propellers starts at about the same level at 

the lower helical tip Mach numbers. The SR-7A noise rises more slowly as the 

helical tip Mach number increases, and reaches a lower peak level than the 

SR-2 propeller noise. 

caused the slower noise increase with speed and the lower peak value. 

The tailored sweep of the SR-7A propeller apparently 

A previous comparison of the SR-2 propeller and a swept SR-3 propeller 

showed the noise advantage of the swept propeller extends to a lower Mach 

number than is shown here for SR-7A (fig. 11 of ref. 1). In figure 6 the 

SR-7A is shown to have a somewhat higher power coefficient at the lower Mach 

numbers than does the SR-2. This higher power may be causing a higher loading 

noise level for the SR-7A, thus masking the sweep advantage at the lower Mach 

numbers. At the other end of the Mach number range, the SR-7A noise approaches 

the SR-2 levels at the high helical tip Mach numbers (fig. 7(d), Mht = 1.29). 

Directivity comparisons. - Comparisons of the SR-7A and SR-2 blade passing 

tone directivities are shown in figure 8 for the 3.06 design advance r a t i o a t 

the seven Mach numbers tested. 

In general, the directivities for the two propellers have the same shape. 

At the lower axial Mach numbers, M = 0.6 to M = 0.8, the SR-2 noise level 

peaks at a location slightly forward of that of the SR-7A propeller. This 

might be expected since the SR-7A's swept blades move its tip sections downstream with respect to the SR-2 tip sections. However, at the M = 0.85 axial 

Mach number, the peak noise location of the SR-7A is slightly forward, and at 

M = 0.9 significantly forward, of that of the SR-2. The peak noise location 

for the SR-7A propeller remained at about 100" for the M = 0.8, 0.85, and 

0.90 test conditions, but that of the SR-2 propeller moved rearward from about 

100" at M = 0.8 to about 110" at M = 0.9. A possible explanation for this 

shift to the rear is related to the shock wave on the SR-2 leading edge. Reference 12 notes such a leading edge shock on the SR-2 blade at these high helical tip Mach numbers, whereas none was exhibited by a swept-blade SR-3, which 

is similar to the SR-7A. The shift in location of the peak for the SR-2 directivity may be due to this shock front angling more downstream as the Mach 

number increases. The SR-7A, presumedly lacking the leading edge shock, does 

not exhibit the peak location change. 

Harmonics. - The relative levels of the blade passing tone harmonics with 

respect to the fundamental are also of interest. As was shown in references 6 

and 7 for the SR-7A propeller, figure 9 is the plot of the relative levels of 

the harmonics at M = 0.8 and J = 3.06 (design) with respect to the fundamental at the maximum noise position - transducer number 7 (100"). Although individual harmonics differ somewhat, particularly harmonic number 2, the slopes of 

the general decline in noise with increasing harmonic number are approximately 

4 
the same (about 6 dB/harmonic> for both propellers. 

decay is more complex for the SR-7A than for the SR-2. 

In general, the harmonic 

CONCLUDING REMARKS 

Noise data on the straight blade SR-2 propeller model were taken in the 

NASA Lewis 8- by 6-Foot Wind Tunnel. The propeller was tested at its design 

blade setting angle at seven tunnel Mach numbers and five advance ratios. 

maximum blade passing tone occurs in the 100" to 110" range and, at constant 

advance ratio, rises with increasing helical tip Mach number to a peak level 

at around 1.05 helical tip Mach number; then it remains the same or decreases 

with increasing helical tip Mach numbers. This behavior, which has been 

observed with other propeller models, implies that using faster rotating propellers may be a method of limiting cabin noise while maintaining high flight 

speed and efficiency. 

The 

Noise comparisons of the straight-blade SR-2 propeller and the swept-blade 

SR-7A propeller showed that the tailoring of the SR-7A sweep appears to have 

resulted in lower peak noise levels and slower noise increases with increasing 

helical tip Mach numbers. Comparison of plots of relative levels of the blade 

passing tone harmonics with respect to the fundamental at 100" as a function of 

increasing harmonic number showed about the same slope for the two propellers 

at 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

the design condition. 

REFERENCES 

Dittmar, J.H.; Jeracki, R.J.; and Blaha, R.J.: Tone Noise of Three Supersonic Helical Tip Speed Propellers in a Wind Tunnel. NASA TM-79167, 1979. 

Di ttmar, J.H.; and Jeracki, R.J.: Additional Noise Data on the SR-3 Propeller. NASA TM-81736, 1981. 

Dittmar, J.H.; Stefko, G.L.; and Jeracki, R.J.: Noise of the 10-Bladed, 

60" Swept SR-5 Propeller in a Wind Tunnel. NASA TM-83054, 1983. 

Dittmar, J.H.; Burns, R.J.; and Leciejewski, D.J.: An Experimental Investigation of the Effect of Boundary Layer Refraction on the Noise from a 

High-speed Propeller. NASA TM-83764, 1984. 

Dittmar, J.H.: Preliminary Measurement of the Noise from the 219 Scale 

Model of the Large-Scale Advanced Propfan (LAP) Propeller, SR-7A. NASA 

TM-87116, 1985. 

Dittmar, J.H.; and Stang, D.B.: Cruise Noise of the 2/9th Scale Model of 

the Large-Scal e Advanced 

1987. 

Dittmar, J.H.; and Stang 

the Large-Scale Advanced 

87-2717. Oct. 1987. 

Mikkelson, D.C, et al.: 

pellers for Mach 0.8 Cru 

Propfan (LAP) Propeller, SR-7A. NASA TM-100175, 

D.B.: Cruise Noise of the 2/9 Scale Model of 

Propfan (LAP) Propeller, SR-7A. AIAA Paper 

Design and Performance of Energy Efficient Prose. NASA TM-X-73612, 1977 (SAE Paper 770458). 

5 
9. Hanson, D.B.; and Fink, M.R.: The Importance of Quadrupole Sources in 

Prediction of Transonic Tip Speed Propeller Noise. J. Sound Vibr., 

vol. 62, no. 1, Jan. 8, 1979, pp. 19-38. 

10. Dittmar, J.H.; and Rice, E.J.: A Shock Wave Approach to the Noise of 

Supersonic Propellers. NASA TM-82752, 1981. 

11. Hanson, D.B.: Propeller Noise Caused by Blade Tip Radial Forces. AIAA 

Paper 86-1892, July 1986. 

12. Brooks, B.M.; and Metzger, F.B.: Acoustic Test and Analyses of Three 

Advanced Turboprop Models. NASA CR-159667, 1972. 

6 
TABLE I . . SR-2 PROPELLER DESIGN CHARACTERISTICS 

Diameter. cm (in.) ........... 62.2 (24.5) 

Number of blades ................. 8 

Design Mach number ............... 0.80 

Design tip speed. m/sec (ft/sec) ..... 244 (800) 

Design advance ratio .............. 3.06 

Design power coefficient ............ 1.7 

Activity factor ................ 203 

Blade setting angle. deg ............. 59 

Design power loading kW/m2 (hp/ft2) ... 301 (37.5) 

7 
TABLE 11. - TEST CONDITIONS 

[Blade setting angle equals 59O.I 

Axial 

Mach 

number 

0.90 

I 

I 

0.85 

0.80 

I 

I 

I 

I 

I 

0.75 

0.70 

0.65 

0.60 

aWi ndmi 

Advance 

ratio, 

J 

3.63 

3.5 

3.25 

3.06 

3.70 

3.5 

3.25 

3.06 

3.84 

3.75 

3.5 

3.25 

3.06 

2.84 

3.84 

3.75 

3.5 

3.25 

3.06 

2.75 

3.84 

3.75 

3.5 

3.25 

3.06 

2.75 

3.84 

3.75 

3.5 

3.25 

3.06 

2.75 

3.85 

3.75 

3.5 

3.25 

3.06 

2.75 

He1 i cal 

tip Mach 

number, 

Mht 

1.192 

1.209 

1.250 

1.289 

1.115 

1.143 

1.182 

1.217 

1.034 

1.042 

1.074 

1.111 

1.147 

1.191 

.968 

.978 

1.006 

1.043 

1.074 

1.140 

.904 

.915 

.940 

.974 

1.004 

1.061 

.838 

.845 

.870 

.go1 

.928 

.980 

.773 

.782 

.805 

.833 

.857 

.907 

Power 

coef f i ci ent , 

cP 

(a) 

0.292 

,786 

1.047 

(a) 

.502 

1.022 

1.335 

(a) 

.182 

.685 

1.187 

1.514 

1.834 

(a) 

.190 

.673 

1.143 

1.512 

2.015 

(a) 

.174 

.630 

1.092 

1.432 

2.024 

.165 

.615 

1.042 

1.359 

1.912 

(a) 

.186 

.619 

1.025 

1.320 

1.816 

(a) 

a 
TABLE 111. - ACOUSTIC DATA FOR FIRST EIGHT HARMONICS AT MACH 0.9 

I Harmonic I Transducer 

1 2 3 4 5 6 7 8 9 10 11 12 

Sound pressure level of harmonic, SPL, dB, ref. 2x10-!’ N/mZ 

Advance ratio J = 3.06 

5 

6 

7 

8 

--- --- --- ----- (c) 138.0 145.0 147.0 141.0 141.0 144.5 132.0 

--- --- --- ----- ----- 135.5 144.0 146.0 137.0 134.0 141.0 129.0 

--- --- --- ----- ----- 133.5 143.0 144.5 138.5 128.0 136.0 125.0 

--- --- --- ----- - ---- 131.0 140.0 142.0 133.5 132.5 (c) 126.5 

2 

3 

4 

5 

--- --- --- (c) 143.5 147.0 153.0 154.0 149.0 150.5 150.5 143.0 

--- --- --- ----- 138.5 145.0 151.0 151.0 142.5 135.5 139.5 141.0 

--- --- --- ----- 131.5 142.5 148.5 148.0 140.0 136.0 135.0 139.0 

--- --- --- ----- 126.0 139.5 145.5 145.0 138.5 138.0 133.0 135.0 

8 --- --- --- ----- ----- 133.0 142.0 139.0 124.5 132.0 133.0 127.0 

+- 149.0 149.5 142.0 146.0 

159.0 I 161.0 162.0 161.0 I 161.0 I 153.5 

154.0 I 157.0 160.0 152.5 I 144.5 I 146.5 I 

134.0 I 142.0 + 150.0 153.0 

148.5 151.0 

153.0 

126.5 1 139.0 151 .O 

146.0 I 148.0 146.0 132.5 I 143.0 I 132.0 I I 

142.5 

141 .O 

139.5 I 142.0 137.5 130.0 1 137.0 I 131.0 I 

a1 I (b) I (c) I (c) I 144.5 I 151.0 I 153.5 I 159.5 I 160.0 I 159.0 I 156.0 I 155.5 I 141.5 

9 
Harmonic Transducer 

number 

1 2 3 4 5 6 7 8 9 10 11 12 

Sound pressure level of harmonic, SPL, dB, ref. ZX~O-~ N/m2 

Advance ratio J = 3.06 

a1 (b) (C) (c) 143.5 152.0 155.5 161.5 163.0 163.0 161.5 153.0 144.0 

2 --- --- --- (c) 141.5 148.0 157.0 158.5 153.0 144.5 147.0 144.0 

3 --- --- --- ----- 133.5 146.5 155.0 157.0 147.5 149.5 145.5 137.0 

4 --- --- --- ----- (c) 143.5 152.0 152.0 147.0 138.0 145.0 133.0 

5 --- --- --- ----- ----- 139.0 149.0 148.5 137.5 138.0 137.0 130.0 

6 --- --- --- ----- --- -- 137.0 147.5 147.0 135.0 141.0 134.0 (c) 

7 --- --- --- ----- ----- 134.0 146.0 144.5 132.5 138.0 135.0 ----- 

8 --- --- --- ----- ----_ 130.0 142.5 142.0 127.5 129.0 133.0 ----- 

Advance ratio J 3.25 

al 1 (c) I (c) I (c) 1 143.0 I 152.5 1 156.0 I 160.5 I 161.0 I 159.5 I 153.0 I 154.5 I 142.0 , 

2 

3 

--- --- --- (c) 145.0 149.5 158.0 158.0 148.0 146.0 147.5 138.0 

--- --- _-- ----- 137.5 147.5 154.0 152.5 148.0 145.0 135.5 135.0 

af31 ade passi ng frequency . bTransducer not functioning. 

CNot visible above tunnel background noise. 

4 

5 

6 

10 

--- --- --- ----- (c) 144.0 152.0 146.0 141.0 143.0 140.0 132.5 

--- --- --- ----- ----- 141.5 150.0 144.0 136.0 134.0 139.5 (c) 

--- --- --- ----- -- --- 138.0 147.0 136.0 136.0 130.0 133.5 ----- 

7 --- 

8 --- 

--- --- ----- ----- 135.5 146.0 137.5 130.0 136.0 127.0 ----- 

--- --- ----- - ---- 133.5 144.0 133.0 129.5 134.5 124.0 ----- 
TABLE IV. - Concluded. 

Harmonic 

number 

Transducer 

1 2 3 4 5 6 7 8 9 10 11 12 

Sound pressure level of harmonic, SPL, dB, ref. N/m2 

Advance ratio J = 3.5 

a1 I (c) 1 (c) I (c) I 143.0 I 152.5 I 157.5 I 157.5 I 156.5 I 153.5 I 151.0 I 145.0 I 144.5 

2 

3 

--- --- --- (c) 144.5 151.0 154.5 152.5 143.0 144.5 137.0 139.0 

--- --- --- ----- 139.5 146.5 149.0 137.0 146.5 138.0 138.5 (c) 

5 

6 

8 I --- I --- I --- I ----- I ----- I 134.0 I 137.5 I 124.5 I 130.0 I 127.0 I 127.0 I ----- 

--- --- _-- ----- (c) 142.0 144.5 140.0 125.0 139.5 137.5 ----- 

--- --- --- ----- ----- 140.0 142.5 133.0 137.0 132.5 136.0 ----- 

Advance ratio J 3.70 

aBl ade passing frequency. 

bTransducer not functioning. 

‘Not visible above tunnel background noise. 

11 
TABLE V. - ACOUSTIC DATA FOR FIRST EIGHT HARMONICS AT MACH 0.80 

Harmonic 

number 

Transducer 

1 2 3 4 5 6 7 8 9 10 11 12 

Sound pressure level of harmonic, SPL, dB, ref. ZX~O-~ N/m2 

144.0 

(C) 

144.0 151.5 156.0 162.0 166.0 166.0 163.0 160.0 160.0 150.5 

(c) 138.5 149.5 158.0 162.0 159.0 146.0 154.5 152.0 145.0 

----- ---_- (c) 141.5 153.5 157.5 151.0 145.5 

----- 1 ----- 1 ----- I (c) 1 145.5 1 150.5 I 138.5 1 140.0 I 130.5 1 136.0 I 129.0 

139.0 137.0 141.5 

----- 

----_ 

Advance ratio J = 3.06 

a1 I 142.0 I 142.0 1 145.0 1 152.5 I 157.0 I 162.0 I 165.5 165.0 I 162.0 I 159.5 I 158.0 I 153.5 

----- ----- 136.0 151.5 155.5 144.0 134.5 138.5 143.0 136.0 

----_ ---__ 130.0 146.5 151.0 139.5 133.5 133.0 131.0 130.5 

----- 

----- 

----_ ---_- ----- 142.0 137.0 134.5 134.0 126.0 132.0 129.0 

---_- -- - -_ ---_- 140.5 136.5 132.0 131.0 127.0 125.5 125.0 

2 

3 

Advance ratio J = 3.25 

(C) (C) (c) 142.5 150.0 158.0 158.0 151.5 152.5 149.5 150.5 140.5 

___-_ ----_ ----- (c) 143.5 153.0 151.5 144.5 139.0 139.0 139.5 139.5 

143.0 -+-IT 

4 

5 

6 

I 

----- ----_ ----_ ----- 139.0 150.5 145.0 136.5 142.5 134.5 137.5 135.5 

----- ----_ ---__ ----_ 134.5 147.5 140.0 129.0 136.5 136.0 133.0 139.0 

----- ----- ----- ----- 130.0 146.0 137.0 130.0 130.0 134.5 130.0 135.5 

145.0 144.0 154.0 

7&&G 

7 

8 

I ----- I ----- ----- 

----- ----- ----_ ---__ (c) 143.0 132.0 129.5 127.0 133.0 126.0 126.0 

----- ----- ----- ----- (c) 140.5 128.0 123.0 124.5 127.5 126.5 127.5 

158.5 

150.5 

163.0 164.0 162.5 157.5 151.5 149.0 155.5 

157.5 152.5 143.0 146.0 145.5 141.5 139.5 

137.5 I 148.5 I 134.0 I 132.5 I 136.5 I 136.0 I 131.0 I (c) 

145.5 

142.0 

155.0 144.0 144.5 132.0 143.5 138.0 136.5 

151.0 140.0 133.0 140.5 138.5 133.0 131.5 

133.0 

129.0 

aBl ade passing frequency. 

bTransducer not functioning. 

CNot vi si ble above tunnel background noise. 

145.0 134.5 128.0 135.5 133.0 (C) ----- 

143.0 132.0 (c) 133.0 131.0 ----- ----- 

12 

(c) 142.0 129.0 (c) 132.5 129.5 ----- ----- 
TABLE V. - Concluded. 

Harmonic 

number 

Transducer 

1 2 3 4 5 6 7 8 9 10 11 12 

Sound pressure level of harmonic, SPL, dB, ref. ZX~O-~ N/m2 

. 

2 

3 

(C) (C) (c) 139.5 146.5 152.5 144.5 141.0 139.0 136.5 

----- ----- _-__- (C) (c) 139.0 149.0 146.5 138.5 (c) 

136.0 141.5 143.0 

E- 137.5 134.0 138.5 137.0 ----- 

(c) 139.0 131.0 134.0 ----- 

17 

Advance ratio J = 3.84 

a1 I 137.5 I 139.0 I 139.5 I 146.0 I 154.0 I 156.5 I 151.5 I 147.5 I 145.5 I 146.0 I 142.5 I 139.5 

13 
TABLE VI. - ACOUSTIC DATA FOR FIRST EIGHT HARMONICS AT MACH 0.75 

1 

I Harmonic I 

2 3 4 5 6 7 8 9 10 11 12 

~~~ ~ 

Transducer 

2 

3 

4 

--- 140.0 140.5 148.0 156.5 162.0 156.0 153.0 152.5 156.0 150.0 145.5 

--- (c) 136.0 144.0 152.0 158.0 143.0 150.5 142.0 144.0 141.5 143.0 

--- ----- (c) 133.0 147.0 155.0 140.0 140.5 143.0 135.5 138.0 143.0 

I al 1 (b) 1 146.5 I 148.0 I 159.0 I 162.5 1 167.5 I 168.5 I 167.0 I 165.0 I 155.0 I 151.0 I 155.5 

5 --- ----- ----- I 130.0 I 143.0 I 152.0 I 142.0 I 141.0 1 137.0 1 133.0 I 135.5 I 138.0 

6 --- ----- --_-- I (c) I 139.0 I 150.0 I 141.0 I 135.0 I 137.0 I 135.0 I 138.5 136.0 

7 

8 

--- ----- ----- ----- 133.5 147.0 139.0 126.0 125.0 132.0 132.0 126.5 

--- ----- ----- ----- 131.0 145.0 135.0 129.5 128.0 129.0 130.0 131.0 

a1 

2 

3 

aBl ade passi ng frequency . bTransducer not functioning. 

‘Not visible above tunnel background noise. 

(b) 145.5 144.5 158.0 161.5 162.5 159.0 155.0 156.0 156.5 154.0 149.5 

--- 140.0 140.5 144.5 147.5 143.0 151.0 151.5 147.0 139.5 140.5 143.0 

--- (C) (c) 134.5 141.5 148.5 138.0 140.5 137.5 137.0 134.5 137.5 

14 

4 

5 

--- ----- ----- (c) 136.0 146.0 140.0 135.0 134.0 131.0 132.5 138.5 

--- ----- ----- ----- (c) 138.5 135.0 129.5 131.0 130.0 133.0 134.0 
TABLE VI. - Concluded. 

1 2 3 4 5 6 7 8 9 10 11 12 

~~ 

Transducer 

146.0 142.5 140.5 142.0 I 139.5 

142.5 139.5 I 131.5 

138.5 

132.0 

143.0 

137.0 

(C) 

128.0 

129.5 

126.0 I 126.0 I 129.0 127.0 

(c) 124.0 128.0 122.0 

,dvance ratio J = 3.75 

I I I I I I I 

tdvance ratio J 3.84d 

* 136.0 138.0 149.0 

I 

aBl ade p a s s i n g frequency . bTransducer not functioninq. 

CNot v i s i b l e above tunnel Lackground noise. 

dMeasurements were taken at all transducers for the first eight harmonics. but none was visible above the 

tunnel background noise. 

15 
TABLE VII. - ACOUSTIC DATA FOR FIRST EIGHT HARMONICS AT MACH 0.7 

1 2 3 4 5 6 7 8 9 

I Harmonic I Transducer 

10 11 12 

Sound pressure level of harmonic, SPL, dB, ref. ZxlO-’ N/m’ I I 

aBlade passing frequency. 

bTransducer not functioning. 

CNot visible above tunnel background noise. 

16 
TABLE VII. - Concluded. 

1 2 3 4 5 6 7 8 9 10 11 

I Harmonic I Transducer 

12 

Sound pressure level of harmonic, SPL, dB, ref. 2~10-~ N/m' I I 

I Advance ratio J = 3.5 

aBl ade passi ng frequency . bTransducer not functioning. 

'Not vi si ble above tunnel background noise. 

dMeasurements were taken at all tranducers for the first eight harmonics, but none was visible above the 

tunnel background noise. 

17 
TABLE VIII. - ACOUSTIC DATA FOR FIRST EIGHT HARMONICS AT MACH 0.65 

1 2 3 4 5 6 7 8 9 10 

I Harmonic I Transducer 

11 12 

I I Sound pressure level of harmonic, SPL, dB, ref. 2~10-~ N/mL 

aBl ade passi ng frequency. 

bTransducer not functioning. 

CNot visible above tunnel background noise. 

dMeasurements were taken at all transducers for the first eight harmonics, but none was visible above the 

tunnel background noise. 

18 
TABLE IX. - ACOUSTIC DATA FOR FIRST EIGHT HARMONICS AT MACH 0.6 

1 2 3 4 5 6 7 8 9 10 11 

1 Harmonic I Transducer 

12 

a1 

2 

I I Sound pressure level of harmonic, SPL, dB, ref. 2~10-~ N/mL 

(b) 127.5 128.5 136.5 

--- 127.0 124.0 124.5 

140.0 I 141.5 I 139.0 I 137.0 I 133.0 I 128.5 I 128.0 I 131.0 

I I I I I 1 I 

126.5 I 127.5 I 125.5 I 123.5 I 122.0 I 123.0 I 123.5 I 123.0 

I Advance ratios J = 3.5, 3.75, and 3.85d 

aBl ade passi ng frequency . bTransducer not function i ng. 

'Not vi si bl e above tunnel background noise. 

dMeasurements were taken at all transducers for the first eight harmonics, but none was visible above the 

tunnel background noise. 

19 
ORIGINAL PAGE 

BLACK AND WfllTE PHOTOGRAPH 

r 

I 

-AIRFLOW 

DRYER MODEL 1 t PREPARATION 

BUILDING 

BUILDING 

EQU I PENT 

DRIVE 

BUILDING \ 

TUNNEL I BALANCE / ‘-8x6 TEST SECTION 

COMPRESSOR’ CHAMBERA 

(a) PLAN VIEW OF 8- BY FOOT WIND TUNNEL. 

(b) SR-2 PROPELLER IN TCST SECTION. 

FIGURE 1. - WIND TUNNEL AND PROPELLER INSTALLATION 

20 
(a) ACOUSTIC PLATE MOUNTED OVER SR-7A PROPELLER. 

11 2 3 4 5 16 17 18 19 I10 Ill I12 

-46.7 -41.7 -30.5 

(-18.4) (-16.4) (-12.0) 

I 46.8 I 50.0 I 58.5 I 72.2 I 80 I 90.9 1 100 I 104 I 110 I 116.8 I 120 I 130.4 I 

-16.0 -8.9 0.8 8.9 12.4 18.0 25.0 28.7 42.4 

(-6.3) (-3.5) (0.3) (3.5) (4.9) (7.1) (9.9) (11.3) (16.7) 

(b) TRANSDUCER LOCATIONS. 

FIGURE 2. - ACOUSTIC PLATE. 

21 ORIGINAL PAGE 

BLACK AND WHITE PHOTOGRAPH 
i 150 

140 1 

(a) ADVANCE RATIO J = 3.75. EXCEPT AS NOTED. 

U m 170 r 

(b) ADVANCE RATIO J = 3.5. 

- 

160 

150 

140 

.8 .9 1.0 1.1 1.2 1.3 

ADVANCE 

RATIO. 

J 

0 3.75 

[7 3.70 

0 3.63 

0 3.50 

A 3.25 

0 3.06 

V 2.84 

0 2.75 

(d) ADVANCE RATIO J = 3.06. 

.8 .9 1.0 1.1 1.2 1.3 

HELICAL TIP MACH NUMBER 

(c) ADVANCE RATIO J = 3.25. (e) ADVANCE RATIO J = 2.75, EXCEPT AS NOTED. 

FIGURE 3. - VARIATION OF R4XINUM BLADE PASSING TONE WITH RESPECT TO HELICAL TIP MACH NUMBER AT 

VARIOUS ADVANCE RAT I OS. 

22 
170 r 

160 

A 

N 

f 

z 

150 ln 

N X 

170 r 

- 

- 

130 

170 r 

(c) M = 0.80. 

150 l6OIfi 

lqo 

I 

t 

13040 60 80 100 120 140 

MACH 

NUMBER, 

M 

0 0.90 

0 .85 

A .80 

0 .75 

0 .70 

0 .65 

D .60 

ANGLE FROM UPSTREAM. - DEG 

12 3 4 5 6 78 9 1011 12 

u 

(g) M = 0.60. 

12 3 4 5 6 78 9 1011 12 

(d) M = 0.75. 

TRANSDUCER LOCATIONS 

FIGURE 4. - BLADE PASSING TONE DIRECTIVITIES FOR VARIOUS AXIAL MACH NUMBERS FOR J = 3.06. 

23 
0 CURRENT DATA 

0 PREVIOUS DATA ADJUSTED FOR DISTANCE 

AND CALIBRATION ERROR 

170 c 

ANGLE FROM UPSTREAM, DEG 

I 

12 

L 

3 4 5 6 7891011 12 

TRANSDUCER LOCATIONS 

FIGURE 5. - COMPARISON OF SR-2 DIRECTIVITY WITH 

PREVIOUS DATA CORRECTED BY ADDING 6 dB FOR 

CALIBRATION ERROR (REF. 4) AND 8 dB FOR DISTANCE FROM CENTERLINE (14 dB TOTAL). 

2.8 

BLADE 

SETTING 

ANGLE, 

DEG 

0 59 SR-2 DATA 

- 57.7 

2.4pm ' 

LA 

0 

0 

D: ** ** 

Q 

Q 

.4 0 .6 4 .7 .8 .9 

TUNNEL MACH NUMBER. M 

FIGURE 6. - VARIATION OF POWER COEFFICIENT 

WITH RESPECT TO TUNNEL RACH NUMBER FOR 

J = 3.06. 

24 
160 

150 

140 

(a) ADVANCE RATIO J = 3.75. EXCEPT AS NOTED. 

170 r 

ni I I I I 

f. (b) ADVANCE RATIO J = 3.5. 

160 c 

I 

2 1.3 

ADVANCE 

RATIO, 

J 

0 3.75 

3.72 

[7 3.70 

0 3.63 

0 3.50 

A 3.25 

0 3.06 

v 2.84 

h 2.82 

a 2.75 

OPEN SYMBOLS DENOTE SR-2 DATA 

SOLID SYNBOLS DENOTE SR-7A DATA 

r 

(d) ADVANCE RATIO J = 3.06. 

R4CH NUMBER 

(c) ADVANCE RATIO J = 3.25. (e) ADVANCE RATIO J = 2.75, EXCEPT AS NOTED. 

FIGURE 7. - COMPARISON OF SR-2 AND SR-7A BLADE PASSING TONES. 

25 
170 r 

160 

h 

hl 

\ 

150 In 

2 

hl 

MACH 

NUMBER, 

M 

0 0.90 

0 .85 

A .80 

0 .75 

a .70 

0 .65 

D .60 

OPEN SYMBOLS DENOTE SR-2 DATA 

SOLID SYMBOLS DENOTE SR-7A DATA 

::,A

130 

(a) M = 0.90. 

160 

150 

140 

130 

170 r 

- 

- 

- 

I 1 I I I 

130 

tc) M = 0.80. 

170 r 

r 

c 

(f) M = 0.65. 

r 

40 60 80 100 120 140 - ANGLE FROM UPSTREAM, DEG 

12 3 4 5 6 78 9 1011 12 12 3 

- 

4 5 6 78 9 1011 12 

TRANSDUCER LOCATIONS 

(d) M = 0.75. (9) M = 0.60. 

FIGURE 8. - COMPARISONS OF SR-2 AND SR-7A BLADE PASSING TONE DIRECTIVITIES AT VARIOUS MACH 

NUMBERS FOR J = 3.06. 

26 
WEN SYMBOLS DENOTE SR-2 DATA 

SOLID SYMBOLS DENOTE SR-7A DATA 

r 

IW 

4 -30 - a 

- 40 I I I I 

1 2 3 4 5 6 

HARRONIC NUMBER 

FIGURE 9. - LEVEL OF BLADE PASSING FREWENCY 

HARMONICS RELATIVE TO FUNDAMENTAL AT MIPWM NOISE LOCATION (R = 0.8: e = 100~). 

27 
NASA 

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No of pages 

Unclassified Unclassified 28 

National Aeronautics and 

Space Administration 

22. Price' 

A03 

Report Documentation Page 

1. Report No. I 2. Government Accession No. 

NASA TM-101480 I I 

4. Title and Subtitle 

Cruise Noise of the SR-2 Propeller Model in a Wind Tunnel 

7. Author(s) 

James H. Dittmar 

9. Performing Organization Name and Address 

National Aeronautics and Space Administration 

Lewis Research Center 

Cleveland, Ohio 44135-3191 

12. Sponsoring Agency Name and Address 

National Aeronautics and Space Administration 

Washington, D.C. 20546-0001 

3. Recipient's Catalog No. 

5. Report Date 

April 1989 

6. Performing Organization Code 

8. Performing Organization Report No. 

E-4606 

10. Work Unit No. 

535-03-0 1 

11. Contract or Grant No. 

13. Type of Report and Period Covered 

Technical Memorandum 

14. Sponsoring Agency Code 

15. Supplementary Notes 

16. Abstract 

Noise data on the SR-2 model propeller were taken in the NASA Lewis Research Center 8- by 6-Foot Wind 

Tunnel. The maximum blade passing tone rises with increasing helical tip Mach number to a peak level at a 

helical tip Mach number of about 1.05; then it remains the same or decreases at higher helical tip Mach 

numbers. This behavior, which has been observed with other propeller models, points to the possibility of using 

higher propeller tip speeds to limit airplane cabin noise while maintaining high flight speed and efficiency. Noise 

comparisons of the straight-blade SR-2 propeller and the swept-blade SR-7A propeller showed that the tailored 

sweep of the SR-7A appears to be the cause of both lower peak noise levels and a slower noise increase with 

increasing helical tip Mach number. 

17. Key Words (Suggested by Author@)) 

Propeller noise 

Noise 

Supersonic tip speed 

18. Distribution Statement 

Unclassified -Unlimited 

Subject Category 7 1 

*For sale by the National Technical Information Service, Springfield, Virginia 221 61 NASA FORM 1626 OCT 86