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NASA Contractor Report 198300
/'/ .-//
Aircraft Noise Prediction Program(ANOPP) Fan Noise Prediction forSmall Engines
Joe W. Hough and Donald S. Weir
AlliedSignal Engines, Phoenix, Arizona
Contract NAS1-20102
April 1996
National Aeronautics and
Space Administration
Langley Research Center
Hampton, Virginia 23681-0001
https://ntrs.nasa.gov/search.jsp?R=19960042711 2020-06-22T08:18:34+00:00Z
AIRCRAFT NOISE PREDICTION PROGRAM (ANOPP)FAN NOISE PREDICTION FOR SMALL ENGINES
Final Report Prepared for
National Aeronautics and Space AdministrationLangley Research CenterContract NAS1-20102
Task Order 6
By
Joe W. Hough
and
Donald S. Weir
SUMMARY
ANOPP has been successfullyrevised to include a module which improvesfan noise prediction capability with small turbofan engines. Themodifications have been verifiedwith measured data from three separate
AlliedSignal fan engines. Comparisons of the revised prediction show asignificantimprovement in overall and spectral noise predictions. Therevised technique provides predictions which now coincide with themeasured data spread from the AlliedSignal engines. The most notablerevisions to the Heidmaun method include the reduction of peak discretetone levelsand combination tone levels.
TABLE OF CONTENTS
1.0
2.0
3.0
STATEMENT OF WORK
1.1 Background
I. 2 Objective
1.3 Summary
RESULTS
2.1 Technical Approach
2.2 Update of Small Engine Data Base
2.2.1
2.2.2
2.2.3
2.2.4
2.2.5
2.2.6
Engine Fan Design
Dominant Engine Fan Noise FrequenciesANOPP And GASP Predictions Versus Data
From Engine 1ANOPP And GASP Predictions Versus Data
From Engine 2ANOPP And GASP Predictions Versus Data
From Engine 3
Generalized Small Engine Revisions
2.3 Develop Small Engine Fan Noise Prediction Method
2.3.1
2.3.2
2.3.3
2.3.4
2.3.5
Inlet Discrete Tone Noise
Inlet Combination Tone Noise
Inlet Broadband Noise
Discharge Discrete Tone Noise
Discharge Broadband Noise
REVISED PREDICTION COMPARISONS WITH MEASURED DATA
3.1 Engine 1
3.2 Engine 2
3.3 Engine 3
SMALL ENGINE REVISION TEST CASE
REFERENCES
Pa.e
1
1
1
2
3
3
5
6
6
7
8
9
I0
11
1317
20
23
25
28
2829
30
31
32
iii
OF C_S (Contd)
APPENDICES
I ANOPP THEORETICAL MANUAL UPDATE (15 pages)
II MEASURED DATA VERSUS REVISED PREDICTION, GASP, AND HEIDMANN,
ENGINE I, (20 pages)
III MEASURED DATA VERSUS REVISED PREDICTION, GASP, AND HEIDMANN,
ENGINE 2, (28 pages)
IV MEASURED DATA VERSUS REVISED PREDICTION, GASP, AND HEIDMANN,
ENGINE 3, (20 pages)
V MEASURED DATA VERSUS REVISED PREDICTION, GASP, AND HEIDMANN,
ENGINE 1, (5 pages)
VI MEASURED DATA VERSUS REVISED PREDICTION, GASP, AND HEIDMANN,
ENGINE 2, (7 pages)
VII MEASURED DATA VERSUS REVISED PREDICTION, GASP, AND HEIDMANN,
ENGINE 3, (4 pages)
VIII SMALL ENGINE REVISION; FAN NOISE PREDICTION TEST CASE
(9 pages)
IX SMALL ENGINE REVISION USER'S MANUAL AND ANOPP CODE
DEVELOPMENT (15 pages)
X INTERIM PREDICTION METHOD FOR FAN AND COMPRESSOR SOURCE
NOISE, M. F. HEIDMANN, LEWIS RESEARCH CENTER (SELECT
FIGURES ONLY) AND AIRCRAFT NOISE PREDICTION PROGRAM
THEORETICAL MANUAL, W. E. ZORUMSKI, LANGLEY RESEARCH CENTER
(SELECT TABLES ONLY) (20 pages)
iv
FINAL REPORT
AIRCRAFT NOISE PREDICTION PROGRAM(ANOPP)FAN NOISE PREDICTION
FORSM_LL ENGINES
1.0 STATEMENT OF WORK
1.1 Background
In 1982, AlliedSignal Engines (then Garrett Turbine Engine
Company) produced a "Computer Program to Predict the Noise of General
Aviation Aircraft," (NASA CR-168050) under contract with NASA Lewis
Research Center under the General Aviation Synthesis Program (GASP).
This study identified a need to modify the Heidmann fan noise predict-
ion procedure in the NASA Aircraft Noise Prediction Program (ANOPP) to
better correlate measurements of fan noise from engines in the 3000-
to 6000-pound thrust range. Additional measurements made by
AlliedSignal since that time have confirmed the need to revise the
ANOPP fan noise method for smaller engines.
1.2 Objective
The NASA ANOPP has been used successfully for predictions of
large transport aircraft. Application of ANOPP to smaller regional
transport and business aircraft has demonstrated a need to improve the
fan noise prediction capability. The objective of this task is to in-
tegrate a fan noise prediction capability for smaller engines into
ANOPP. Four subtasks include:
(1) Update of small engine data base
(2) Develop small engine fan noise prediction method
(3) Code and validate a revised ANOPP fan noise module
(4) Document and report results
1
1.3 S_ary
ANOPP has been successfully revised to include a module which
improves fan noise prediction capability with small turbofan engines.
The modifications have been verified with measured data from three
separate AlliedSignal fan engines. Comparisons of the revised
prediction show a significant improvement in overall and spectral
noise predictions.
Figure 1 shows the improved prediction as compared to the
Heidmann and GASP predictions. The revised technique provides
predictions which now coincide with the measured data spread from the
AlliedSignal engines. The most notable revisions to the Heidmann
method include the reduction of peak discrete tone levels and
combination tone levels.
The small engine revisions have been incorporated into the ANOPP
fan noise module. The revised module has been verified with measured
data and a test case has been included for demonstration purposes.
I05.0,
9s.o
i ..o•,- 85.0
_ o/total soundpower levelsfor threesmallAE engines
----"'" W .... GASPB m -- I::llS_8_ON
(lt]r)d : 1.5 _%
•...............-I-I"
I I I I I I I l
0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4
Rotortip retatJveinletroachnumber,Mtr
Figure 1.
I R_isionimpmv_fannoisepredi_onby2_SdB I
Revised Fan Noise Module Shows Overall Improvement
In AlliedSignal Small Engine Prediction.
2
2.0 RESULTS
2.1 Technical Approach
The proposed fan noise prediction revisions in the small engine
revision are intended to improve upon the well-established source
noise prediction procedures originally developed by The Boeing Company
under contract with NASA-Ames and later improved by full-scale engine
data from NASA Lewis under the direction of M. F. Heidmann. In the
Heidmann prediction procedure fan noise is divided into five separate
modules:
o Broadband noise emitted from the inlet and discharge ducts
o Discrete tone noise emitted from the inlet and discharge
ducts
o Combination tone noise emitted from the inlet duct
Predictions within each module provide a one-third octave band
spectrum shape function, a total spectrum level, and a free-field
directivity at a radius of one-meter from the source. Total fan noise
then is calculated through the logarithmic summation of the sound
levels within each of the five modules.
Several engine performance parameters and engine build parameters
are specified within this procedure and drive the predictions. Given
that only three engines were available for AlliedSignal's proposed re-
vision procedure, some of these parameters did not appreciably vary
from engine-to-engine, and were not fully investigated in this proce-
dure. The influential prediction parameters are shown below:
Performance Parameters
o Mass flow rate
o Total temperature rise across the fan
o Design rotor tip relative inlet Mach number - This parameter
remained nearly constant for the three engines, (Mtr) d - 1.5
±5 percent. No attempt was made to modify the Heichnann cor-
rections where (Mtr) d was used
o Operating rotor tip relative inlet Mach number
Engine Build Parameters
o Rotor-Stator Spacing (RSS) - RSS for the three engines did
not vary enough to improve the RSS correction.
o Presence of Inlet Guide Vanes (IGVs) - AlliedSignal"s en-
gines do not have IGVs. Therefore, the corrections which
vary due to IGVs could not be adjusted.
o Presence of Inlet Flow Distortion (ground effects; static
operation) - During acoustic testing, AlliedSignal uses an
inlet flow control device (ICD) to eliminate flow distortion
into the inlet. Therefore, inlet flow distortion effects
were not examined in this investigation. AlliedSignal does
have separate engine data with and without the ICD and can
use this data for future studies.
AlliedSignal's revised predictions concentrate on the adjustments
to the spectrum level, spectrum shape, and directivity adjustments
within each module based on the measured data of three small engines.
4
No attempt was made to add new modules to the prediction or to incor-
porate different prediction procedures not related to the Heidmann
approach.
2.2 Update Of Small Engine Data Base
Subtask 1 calls for the identification of strengths and weak-
nesses of the Heidmann and GASP predictions based on the AlliedSignal
engine data. Figure 2 shows a comparison of small engine fan noise
data with the correlation of NASA Lewis full-scale fan data. Clearly,
it is evident that the small engine fan noise data does not obey the
same correlation function for large fan data. Specifically, the
current Heidmann fan noise routine significantly overpredicts inlet
and discharge fan tone noise levels, inlet buzz-saw peak noise and
spectrum content, and, to a lesser degree, broadband peak noise level
and spectrum content.
140
.="3"
,30:.1.
o
o. 120
1000
Correlation of totalsound power levels for/Ulk_lS_md fan data
" Engine #1 u Engine #2 a Engine #3 I
_ DmaCowelatm
PWL = 98.5 + 101og_TI,aTo) + 101og(SHP)
• 0
o o u & A A A
A &
Shaft Horsepower, SHP
5OOO 1OOOO
NASA-Lewis Data Correlation is Nearly 5 dB Higher Than AIIiedSignal Data J
Figure 2. ItlliedSignal Small Engine Data Does Not Correlate
Well With HASALewis Fan Data.
5
2.2.1 Engine Fan Desiqn
Provided in Table 1 are the fan design property ranges for the
three AlliedSignal test engines. Each of the geared or ungeared fans
has a single stage. Corrected thrust output varies from 400 pounds at
ground idle to 6500 pounds at full speed. These engines do not have
IGVs and inlet distortion is eliminated with the use of an inlet flow
control device for static engine acoustic testing.
TABLE 1. AlliedSignal FAN DESIGN PROPERTY R&NGES
Fan
1,2,and3
214Z790-001
TotalPressure
Ratio,PR
1.5 - 1.6
Rotor TipDesign Rotor-Relative Stator
Mass Rotor Tip inlet Macl Vane-to. Blade SpacingFlow Math Number Blade Passage Cut-Off Factor, InletRate, Number, (Mtr)d Ratio, Frequency, Factor, RSS, GuideIblsac Idt VIB fin Hz 6 percent Vanes
100-22C 0.3-1.2 1.45-1.53 2.0-2.5 3600-5300 0.77-1.15 170-214 None
2.2.2 Dominant Engine Fan Noise Frequencies
All_edSignal measures engine noise with a multimicrophone array
in the far-field over a reflecting plane. All engine noise components
are measured in this arrangement. AlliedSignal routinely performs
noise source separation and has determined that fan noise, for most
engine speeds, is the dominant engine source for frequencies above 1
kHz. In some lower speed engine operating points, jet noise can con-
tribute up to ~3 kHz in the aft microphone arc.
Given the strong noise contributions by other engine sources in
the lower frequency bands, fan noise is only shown for one-third oc-
tave bands from 1 kHz to 10 kHz. Overall noise levels shown in the
provided figures are computed from this frequency range.
2.2.3 _NOPP And GASP Predictions Versus Data Frc_ Enqine 1
Figure 3 shows the correlation of sound power levels for Engine 1
and the associated fan noise predictions using the Heidmann and GASP
routines. For subsonic tip speeds, the Heidmann and GASP routines
consistently provide sound power predictions a maximum 6- to 7-dB
higher than measured fan data. Examination of the predictions for
blade pass tones and their harmonics shows an average 2- to 6-dB over
the measured data. Broadband noise levels and spectrum content appear
to be mismatched as well.
For supersonic tip speeds, the predictions fair better against
the measured data. However, fan tones are still overpredicted by 2 to
4 dB and the combination tone noise spectra are slightly higher than
test data.
Fan Noise C.,ormlalbnfix Test F.ngine#1
iD Heiclmann u GASPx Measured
150!
>o..z-
_m = 140
m 130
_ g'" g
0 120 x
X
D
il
XI
2OO0
aX
I I I I I I I
1000 1500 2500 :3000 3500 4000 4500 5000
Shaft Horsepower, SHP
Discrete Tones and Combination Tones Require Revision I
Figure 3. Heickk_nn _nd _ Show Slight To Moderate Fan Noise
Overprediction For Engine 1.
2.2.4 ANOPP And GASP Prediotions Versus Data Frc_ Engine 2
Figure 4 shows the correlation of sound power levels for Engine
2. Unlike Engine 1, blade pass tones and their harmonics are only 2-
to 3-dB over the measured data for subsonic tip speeds, but 4- to 7-dB
over measured data for supersonic tip speeds. Combination tone noise
is underpredicted during the early introduction of buzz-saw and
overpredicted as fan speed increases.
Broadband noise is predicted well, however, the spectral
distribution appears to peak at a lower frequency than 2.5f b.
FanNoise Correlali_ tot Test Engine#2
J m Heidmann u GASP
140 •I
b.
|
_. is0
o®50
D
x
O D XD
x x
120 I I I I I I I I
1000 1500 2000 2500 3000 3500 4000 4500 5000
ShaftHorsepower,SHP
Broadband Spectral Distribution and Combination Tones Require Revision J
Figure 4. HeidBann And GKSP Show Moderate Fan Noise
Overprediotion For Engine 2.
8
2.2.5 ANOPP and GASP Predictions Versus Data From Engine 3
Figure 5 shows the correlation of sound power levels for Engine
3. The transition to supersonic tip speeds is the least evident in
the fan noise spectra with this engine. Fan tones are still
overpredicted by 2 to 7 dB for all fan speeds and combination tone
noise is well above the measurements. Broadband noise levels match
well at the lower fan speeds but are overpredicted by 3 to 5 dB
especially for high fan speeds.
140!
130
_o"
0120
1000
g
x x
Fan Noise Cormlal_onfor Test Engine
I" HeidmannaGASP x I
tR
x x
! I I I I I I
1500 2000 2500 3000 3500 4000 4500
Shaft Horsepower, SHP
I
5000
Discrete Tones and Combination Tones Require Revision
Figure 5. Heicksann And GASP Show Significant Fan Noise
Overprediction For Engine 3.
9
2.2.6 Generalized Small Engine Revisions
For each of the three engines, it is clear that many revisions
are necessary to the peak sound pressure levels, directivity, and
spectrum distribution. For example, broadband peak noise and spectra
content were either overpredicted or centered too high in frequency.
Inlet and discharge tone directivity functions did not match test data
well in the 70- to 100-degree midarc angles, and combination tone
noise predictions sometimes were so overpredicted that they dominated
a majority of the fan noise spectra.
Following a review of the predictions and their agreement or dis-
agreement with the measured data, a summary of the required revisions
is provided below. Further discussion is supplied in paragraph 2.3.
O Inlet prediction revisions relative to the Heidmann ap-
proach:
u
Peak pressure of the fundamental tone has been de-
creased by 6 dB
Rolloff of the first harmonic has been increased from 3
to 9.2 dB
Rolloff of the second harmonic is 1.6 dB
Rolloff of the remaining harmonics remains 3 dB
Tone directivity has been slightly modified
Peak pressure of the combination tone noise has been
significantly decreased
Peak pressure of the broadband noise has been decreased
by 3 dB
Broadband noise spectrum has been shifted lower in fre-
quency
10
o Discharge prediction revisions relative to the Heidmann ap-
proach:
D
m
m
m
Peak pressure of the fundamental tone has been de-
creased by 4 dB
Rolloff of the first harmonic has been increased from 3
to 9.2 dB
Rolloff of the second harmonic is 1.6 dB
Rolloff of the remaining harmonics remains 3 dB
Tone directivity has been slightly modified
Peak pressure of the broadband noise has been decreased
by 2 dB
Broadband noise spectrum has been shifted lower in fre-
quency
The changes in the small engine revision module are provided in
detail in Figures 6 to 19. The ANOPP manual has been updated as well,
see Appendix I.
2.3 Develop Small Engine Fan Noise Prediction Method
The procedure for predicting inlet and discharge fan noise is a
two-stage process:
(a) Calculate the characteristic one-third octave band SPL, L c
L c = 20 log(aT/AT o) + i0 log(m/m O) + Fl[Mtr,
+ C
(Mtr)d] + F 2[RSS] + F 3[e]
where:
Lc
one-third octave band
pressure level of a
radius, dB
characteristic partial sound
single-stage fan at 1-meter
11
AT =
AT ° =
m =
m =o
Mtr =
(Mtr) d =
RSS =
e =
C
total temperature rise across fan, °R
reference value of T, I°R
mass flow rate through fan, ib/sec
reference value of m, ib/sec
rotor tip relative mach number
design point value of Mtr
rotor-stator spacing in percent at rotor tip
directivity or polar angle relative to inlet axis,
degrees
correction for IGVs
The function F 1 determines the peak inlet or discharge discrete
or broadband noise level. The variance of F 1 is determined by the
values of Mtr and (Mtr) d. F 2 determines the influence of rotor-stator
spacing with a dependency on inlet flow distortion. F3 determines the
directivity function for each noise contributor.
(b) Calculate the spectrum shape function, SPL(f)
where SPL(f) = L c + F4(f/f b)
The sound pressure level for each contributor, Lc, is then given
a spectrum shape function, F4, which is centered on a multiple value
of the blade passage frequency. For supersonic rotor tip speeds, a
combination tone noise component is included and has its own spectral
shape function.
The process of calculating L c and SPL(f) is performed separately
for the five fan noise components listed:
(1) Inlet discrete tone noise
(2) Inlet combination tone noise (when applicable)
(3) Inlet broadband noise
(4) Discharge discrete tone noise
(5) Discharge broadband noise
12
Total fan noise is obtained through the energy summation of these
five noise components. These calculations provide one-third octave
band sound pressure levels of the free-field noise at a one-meter rad-
ius.
To accelerate the revision process, AlliedSignal created a PC-
based Excel spreadsheet of the GASP and Heidmann fan noise modules.
Each of the five component noise sources was programmed in a separate
file, and each file was linked to a total fan noise file. As influ-
ence parameters were modified, the changes in both the corresponding
component and total fan noise contributions were readily observed.
The accuracy of the spreadsheet was verified against the documented
fan noise version in the GASP library.
Using the temporary spreadsheet, revisions were made to each com-
ponent and compared with measured data from the three engines. This
process was repeated many times until satisfactory prediction agree-
ment with measured data was achieved. The result is a revised pre-
diction method which provides a significant improvement in
AlliedSignal small fan noise. The revisions to each component are
provided in the following sections and are referred to as small engine
revision or revision. Suggestions for further improvements in this
model are requested.
2.3.1 Inlet Discrete Tone Noise
The characteristic peak sound pressure level for the fundamental
tone is:
Lc -- 20 log(AT/ATo) + i0 log(m/mo) + F l[Mtr , (Mtr) d] + F 2[RSS] + F 318]
13
(a) Changes to Fl[Mtr, (Mtr)d]: Figure 6 shows the revisions to
the normalized peak SPL function, FI. A 6-dB reduction was
chosen due to the overall improvement of the fundamental
tone level with measured data for all three engines.
Notes for future investigation of FI: A value of 0.72 for
Mtr is used as a transition parameter between prediction
functions. The measured data indicates that this 0.72 value
may need to be increased possibly to the value of 0.9 or
even 1.0. MOre investigation is required to determine a
better approximation of this transition value.
Lc = 20log(AT/AT o) + 101og(m/mo) +lF,[Mtr,(Mtr)d]l+ F=[RSS] + Fa[0]
• For (Mtr)a>l, Mtr<0.72
Heidmann, GASP - 60.5 + 201og(Mtr)d
revision - 54.5 + 201og(Mtr)d
• For (Mtr)d>l, 1_0.72
Heidmann, GASP - lesser of: 60.5 + 501og(Mtr/0.72)
or 59.5 + 801og((Mtr)d/Mtr))
revision - lesser of: 54.5 + 501og(Mtr/0.72)
or 53.5 + 801og((Mtr)d/Mtr))
I Reference Figure 10a shown in Appendix X 1
Figure 6. Inlet Discrete Tone Noise Revisions Improve Peak SPL.
14
(b) Changes to F3[0]: Figure 7 shows the revisions to the
directivity function, F 3. The slope of the directivity
function relative to the maximum angles (20 to 40 degrees)
was slightly decreased.
Notes for future investigation of F3: Narrowband data
analysis can be used to better evaluate the tone rolloff in
future studies.
The sound pressure level spectrum is:
SPL(f) - Lc + I0 log[ 10 0.1F4(f/fb ) ]
Lc : 2Olog(AT/ATo) + 1Olog(m/mo) + F,[M.,(I_,)_] + F,[RSS] +IF,[0] !Theta Heidmann GASP Revision
.3.0
-1.50.00.0
0.0
-1.2
.3.5-6.8
-10.5
-14.5-19.0
-24.5-30.0
-35.5-41.0
-46.5
-52.0-57.5
-63.0
-4.5-3.0
-1.5-1.5
-1.5
-2.5-4.0
-6.0
-8.5-12.5
-17.0-20.5
-24.0-27.5
-31.0
-34.5-38.0
-41.5-45.0
-3.0
-1.5-1.5
-1.5-1.5
-2.0
-3.0-4.0
.6.0
-9.0-12.5
-16.0-19.5
-23.0-26.5
.30.0
-33.5.37.0
-40.5
01020
30
40
5060
708O
90100
110120
130
140
150160170
180
I Reference Figure 13a shown in Appendix J1
×
Figure 7. Inlet Discrete Tone Noise Revisions ImproveDirectivity Correction.
15
(c) Changes to F4(f/fb): Figure 8 shows the revision to the
rotor-stator interaction discrete tone harmonic rolloff
levels. Rolloff of the second harmonic has been increased
from 3 to 9.2 dB. Rolloff of the third harmonic is 1.6 dB,
and the remaining harmonics retain a 3-dB rolloff.
Notes for future investigation of F4: Only one of the three
engines operating at low fan speed does not completely
exhibit the revised harmonic tone rolloff. For this fan
operating at low speed, the fundamental 1/3-octave band tone
level is barely visible above broadband sources,
inconsistent with the other two fans.
Harmonic tone rolloff for fans operating at low-speed points
may require a closer examination for follow-up studies.
SPL(f) : I. c + 10 log [1010"IF4(U )J]
H0idmsnn, GASP Revision
4
HarmonicLevel, L
1 2 3 4 5 6
Harmonic order, k
L = Lc + 3- 3k; 8> 1.05
L=Lc-8;k=I }L =Lc+3-3k; k>2
4
1 2 3 4 5 6
Harmonic order, k
8< 1.05
L=Lc 8 > 1.05'_ k=lL = Lc - 8 8 < 1.05 J
L = Lc- 9.2; k=2L=Lc -3k- 1.8; k>3
Figure 8.
Reference Figure 8a shown in Appendix X
Inlet And Discharge Discrete Tone Noise Revisions
Improve Interaction Tone Harmonic Levels.
16
2.3.2 Inlet Combination Tone Noise
The characteristic peak sound pressure level for the fundamental
tone is:
L c = 20 log(_T/ATo) + I0 log(m/m o) + F l[Mtr] + F 2[el + C
(a) Changes to Fl[Mtr]: Figures 9, 10, and 11 show the revi-
sions to the normalized peak SPL function, F 1. The peak
levels for the 1/2, 1/4, and 1/8 tones were reduced signifi-
cantly. The slopes of the F 1 curves were also changed to
better match the peak measured levels. Furthermore, note
the "201og[Mtr]" distribution rather than the "Mtr distri-
bution which is used in the Heidmann curves.
(f/fb = 1/2)
Lc = 201og(AT/ATo) + 101og(m/m o) +IF,[I_]I+ F2[0] + CB E
Combinationtonenoiselevelsat 1/2 of bladepassagefrequency
I O_ &GASP X Smmll_ _ ),
, 80.0
-J _ 70.0
m _ ,_.o
4o.0
Z .j_ 30.0 I I I ! I I
0.0 1.0 2.0 3.0 4.0 5.0 6.0
2010g(RotorTip RelativeMachNumber)
Figure 9.
I Reference Figure 15a shown in Appendix X }
Inlet Combination Tone Noise Revisions Improve PeakSPLCorrection.
17
Notes for future investigation of FI: The peak combination
tone levels currently are predicted by GASP to occur at Mtr
= 1.0 for 1/2 and 1/4 tones, and Mtr - 3.0 for 1/8 tones.
The measured data suggests that the actual peak levels may
not be solely dependent on the value of Mtr. Also, further
investigation likely will reveal the need to improve the
slopes of the normalized peak level curves.
(f/fb = 1/4)
Lc : 201og(ATIATo) + 101og(mlmo) +IFI[M ]I+ F2[0] + C
Combination tone noise levels at 1/4 of blade passage frequency
I 13 HeidmannX GASP
• Small Engine Revision I
. 'A 80.0
.oo600
"_ so.o
m ._ 40.0E,-OZ o
" 30.0
0.0
I I I I I I
1.0 2.0 3.0 4.0 5.0 6.0
20log (Rotor Tip Relative Mach Number)
I Reference Figure 15a shown in Appendix X J
Figure I0. Inlet Combination Tone Noise Revisions Improve PeakSPL Correction.
18
(f/fb = 118)
L© = 20log(AT/•To) + 101og(m/mo) +IF,[Mt,]I+ F2[0] + C
Combination tone noise levels at 1/8 of blade passage frequency
I D Heidmannx GASP
• Small Engine Revision I
80.0._- '.L.m o
i _ 70.0
_!60.0
so0
_ 40.0
Z_30.0
0.0
....... •I ...... "_ " ° " _ ....... • ............ "& ............ t ............ •
I I I
1.0 2.0 3.0 4.0 5.0 6.0
20log (Rotor Tq:) Relative Mach Number)
I Reference Figure 15a shown in Appendix X I
Figure 11. Inlet Combination Tone Noise Revisions Improve Peak
SPL Correction.
(b) Changes to F2[e]: Figure 12 shows the revision to the
directivity function, F 2. The slope of the function has
been decreased.
The sound pressure level spectrum is:
(c)
SPL(f) = L c + F 3(f/fb )
Changes to F3(f/fb): Figure 13 shows the revision to the
combination tone noise spectrum content. The distribution
was decreased from 301og to 151og for the 1/2 combination
tone spectrum. The 1/4 and 1/8 combination tone spectra
were not changed.
19
Lc = 201og(ATIATo) + 10log(mira o) + FI[M_] _ C
Theta Heidmann GASP, Revision
10203O405O607O8O90
100110120130140150150170180
-_5-7.0-5.0-2.00.00.0
-,%5-7.5-9.O-9.5
-10.0-10_-11.0-11._-12.0-12.5-13.0-1:L5
-4.5-3.O-1.50.00.00.00.0
-2.5-5.0-6.0-6.9-7.9-8.8-9_
-10.7-11.7-12.6-13.6
Reference Figure 16 shown in Appendix X
Figure 12. Inlet Combination Tone Revisions Improve DirectivityCorrection.
Notes for future investigation of F3: The combination tone
levels were so highly overpredicted that revisions to the
spectral content were not thoroughly investigated. Measured
data suggests significant room for improvement for F 3.
2.3.3 Inlet Broadband Noise
The characteristic peak sound pressure level for the single fan
stage is:
L c : 20 log(AT/AT o) + i0 log(m/m o) + F l[Mtr, (Mtr)d] + F 2[RSS] + F 3[e]
20
(f/fb = 1/2)
SPL(f) = Lc +IFa=(flfb) I
, I Revision: "151og(f/fb) I
0
Relative 1/3 -10Octave Band
-20 g(flfb)
I-30
0.1 0.5 1.0 5.0
Dimensionless frequency, flfb
I Reference Figure 14a shown in Appendix X J
Figure 13. Inlet Combination Tone Noise Revisions Improve
Spectrum Content.
(a) Changes to Fl[Mtr, (Mtr)d]: Figure 14 shows the revisions
to the normalized peak SPL function, F I. A 3-dB decrease
was made for an overall improvement of the inlet broadband
noise. The parameter of Mtr = 0.9 is agreeable with the
measured data.
The sound pressure level spectrum is:
SPL(f) = Lc + F 4(f/fb )
21
Lc = 201og(ATIATo) + 101og(m/m o) +IF,[M_,(I_)_]I+ F=[RSS] + F318]
Heidmann, GASP
revision
• For (M_)_.I, M_0.9
- 58.5 + 201og((l_) d)
- 55.5 + 201og((l_r)d)
Heidmann, GASP
revision
For (1_)_1, M_0.9
- 58.5 + 201og((l_r)d) - 201og(M,]
- 55.5 + 201og((M_)d) - 201og(Mtr )
IFigure 14.
Reference Figure 4a shown in Appendix X I
Inlet Broadband Noise Revisions Improve Peak SPL.
(b) Changes to F4(f/fb): Figure 15 shows the revision to the
spectrum content correction. The log normal distribution
center frequency has been shifted down from 2.5 f/fb to 2.0
f/fb" Sound level rolloff has been decreased for fre-
quencies below f/fb' and increased for frequencies above
f/fb"
Notes for future investigation of F4: NASA Lewis data
analysis suggests that broadband spectral noise content
follows two log normal distribution functions, one centered
at 2.5 f/fb and the other centered near 20 f/fb" The
measured engine data agree with the log distribution but
suggests the possible need for a second spectrum distri-
bution function.
22
SPL(f) = Lc +_
• Heidmann, GASP
- 101og(exp(-0.5(In(fl2.5fh))2))In2.2
for all f
• Revision
- 101og(exp(-O.35(In(f/2.0fh))2)) for f < 2fbIn2.2
- 101og(exp(-2.0(In(fl2.0fb))2)) for f > 2fbIn2.2
I Reference Figure 3a shown in Appendix X J
Figure 15. Inlet And Discharge Broadband Noise Revisions
Improve Spectrum Content Correction.
2.3.4 Discharge Discrete Tone Noise
The characteristic peak sound pressure level for the fundamental
tone is:
Lc
(a)
= 20 log(AT/AT o) + I0 log(m/m o) + F l[Mtr, (Mtr)d] + F 2[RSS] +
F318 ] + C
Changes to Fl[Mtr, (Mtr)d]: Figure 16 shows the revisions
to the normalized peak SPL function, F 1. A 4-dB rolloff was
chosen due to the overall improvement of the blade passage
level with measured data.
23
I-c: 201og(ATIATo)+ 101og(rn/mo) + +c• For (M_)d>l, Mv<I
Heidmann, GASP - 63.0 + 201og((Mtr) d)
revision - 59.0 + 201og((Mtr) d)
• For (l_r)d >1, M_I
Heidmann, GASP - 63.0 + 201og((l_r) _) - 201og(l_r)
revision - 59.0 + 201Og((lVltr) d) - 20lOg(My)
Figure 16.
I Reference Figure 10b shown in Appendix X I
Discharge Discrete Tone Noise Revisions Improve Peak SPL.
(b) Changes to F318]: Figure 17 shows the revisions to the
directivity function, F 3. The slope of the directivity
function below the peak level angles (110 to 130 degrees)
was slightly decreased.
The sound pressure level spectrum is:
(c)
SPL(f) = Lc + F4(f/f b)
Changes to F 4 (f/fb) : Revisions to the
harmonic rolloff is provided in Figure 8.
discrete tone
24
i. c = 201og(ATIL_T o) + 101og(m/m o) + FI[Mu,(I_) d] + F2[RSS ] _ C
Theta Iteidmann GASP Revision
10 -,15.020 -31.030 -27.O40 -23.050 -19.06O -15.070 -11.08O -_0
9O .9.O100 -_0110 -1.0120 0.0130 0.0140 -2.0150 o5_160 -9.0170 -1_0180 -18.0
-3O.O-28.5 -2_0-24.q -22.0-20._ -1_0-16.5 -14.0-12.5 -10.5
-8.5 -6.5-S.5 -4.0-2-5 -1.0-0.5 0.00.0 0.0
0.0 0.00.0 0.0
-2.0 -1.0-_5 -3J-9.0 -7.0
-I:L0 -11.0-18.0 -16.0
I Reference Figure 13b shown in Appendix X I
Figure 17. Discharge Discrete Tone Noise Revisions Improve
Directivity Correction.
2.3.5 Discharge Broadband Noise
The characteristic peak sound pressure level for the single fan
stage is:
L c = 20 log(AT/AT O) + i0 log(m/m O) + F l[Mtr, (Mtr)d ] + F 2[RSS] +
F318] + C
(a) Changes to Fl[Mtr, (Mtr)d]: Figure 18 shows the revisions
to the normalized peak SPL function, F 1. A 2-dB decrease in
the peak sound pressure level was made for an overall
improvement of the inlet broadband noise with measured data.
25
• For (Mtr)d >1, I_r<l
Heidmann, GASP - 60.0 + 201og((Mtr)d)
revision - 58.0 + 201og((Mtr)d)
• For (Mtr)d>l, I_1
Heidmann, GASP - 60.0 + 201og((Mtr)d) - 201og(M_)
revision - 58.0 + 201og((l_r)d ) - 201og(Mtr )
I Reference Figure 4b shown in Appendix X I
Figure 18. Discharge Broadband Noise Revisions Improve Peak SPL.
(b) Changes to F3[0]: Figure 19 shows the revisions to the
directivity function, F 3. The slope of the directivity
function below the maximum level angle (130 degrees) has
been decreased.
The sound pressure level spectrum is:
(c)
SPL(f) = Lc + F4(f/f b)
Changes to F4(f/fb): Revisions to the discharge broadband
spectrum content are provided in Figure 15.
26
Lc = 201og(AT/ATo) + 101og(m/m o) + FI[M_,(IV_)d] + F2[RSS] Fs_rrr_ C
Theta Heidmann, GASP Revision
10203O
4050
6070
8090
100
110120
130140
150160170
180
-36.0-32.0
-28.0-24.0
-20.0
-16.0-11.5
-8.0
-5.0-2_7
-1_.-0_0.0
-2_0-6.0
-10.0
-15.0-20.0
-29.5-26.0
-22.5-19.0
-15.5
-12_0-8.5-5.0-3.5
-2_5-2.0
-1.30.0
-3.0-7.0
-11.0
-15.0-20.0
Reference Figure 7b shown in Appendix X
Figure 19. Discharge Broadband Noise Revisions I_prove
Directivity Correction.
27
3.0 REVISED PREDICTION COMPARISONS WITH _
The small engine revisions have been verified against measured
data from three AlliedSignal engines. Differences of the predicted
and measured far-field sound pressure levels (40 degrees - midangle of
inlet noise arc, 80 degrees - near midangle between inlet and exhaust,
and 120 degrees - midangle of exhaust noise arc) and sound power
levels for the three engines are provided in Appendices II, III, and
IV. These plots show 1/3-octave band spectral differences in AdB SPL
and AdB PWL from 1 kHz to I0 kHz. The data points cover a spread of
fan speeds from 60 to 100 percent of the design speed. Tabulated 1/3-
octave band level differences and overall level differences for all
angles, 10 to 160 degrees, are provided in Appendices V, VI, and VII.
3.1 Engine 1 (See Appendices II And
Five data points were used for this engine. Fan speeds ranged
from 65 to 99 percent speed. The revised prediction method shows a
significant improvement in inlet noise for the 65 and 75 percent fan
speeds, but discharge noise still remains slightly over-predicted
especially for the exhaust noise angles, 100 to 160 degrees.
This particular engine seems to have an abrupt combination tone
noise cut-on behavior as seen in the inlet midangles for the 85 per-
cent speed point. At this speed, the buzz-saw noise prediction has
improved but the predictions for inlet fan tones has worsened.
Conversely, the 95 and 99 percent speeds show a significant
improvement with the revised prediction method. Predictions for buzz-
saw noise fair well and inlet and discharge discrete tones and broad-
band noise show improvement.
28
Notes for future prediction improvements:
o Inlet and discharge discrete tones and broadband noise are
still overpredicted for low fan speeds
o Inlet and discharge broadband noise is slightly underpre-
dicted for higher fan speeds
o Combination tone noise is still overpredicted for higher fan
speeds
3.2 Engine 2 (See J_ndices III And V I)
Seven data points were used for this engine. Fan speeds ranged
from 61 to 100 percent speed. The revised prediction method shows a
significant improvement in discharge noise for all fan speeds, but
inlet noise is slightly to marginally underpredicted especially for
the 61 to 88 percent speed points. The discrete tone rolloff is not
severe for the 65 to 75 percent speeds, but as fan speed increases,
the rolloff begins to show characteristics similar to the revised
prediction.
Buzz-saw noise prediction has improved tremendously. An improve-
ment of 10 dB and more is seen in the peak combination tone levels.
For the higher fan speeds inlet fundamental tones, harmonics and
broadband noise show improvement with the revised prediction method.
Notes for future prediction improvements:
o
o
Inlet and discharge discrete tones and harmonics are now
slightly underpredicted for lower fan speeds
Inlet broadband noise is slightly underpredicted for lower
fan speeds
29
3.3 Engine 3 (See ]qopendices IV And VII)
Four data points were used for this engine. Fan speeds ranged
from 60 to 87 percent speed. The revised prediction method shows
excellent agreement for the 60 to 75 percent fan speeds. Agreement
also is improved for the higher fan speeds where the buzz-saw noise
has improved over 10 dB.
Discrete fundamental tones are still being overpredicted with the
revised method, but by only 2 to 5 dB instead of 9 to 15 dB with
Heidmann and GASP. Broadband noise has improved but is still slightly
overpredicted as well.
Notes for future prediction improvements:
O Inlet and discharge discrete tone and broadband noise are
still slightly overpredicted for high fan speeds
o Combination tone noise is overpredicted for the 1/4 tone
30
4.0 SMALL ENGINE REVISION TEST CASE
A sample fan noise prediction test case using the small engine
revision module has been compared to measured Engine 1 data, see
Appendix VIII.
Using the supplied engine parameters for Engine 1, fan noise
predictions were made with the Heidmann, GASP, and Small Engine
Revision modules. The results of these predictions are provided in
four tables and figures which show the following:
O
O
O
O
Third-octave sound power level spectra
Third-octave sound pressure level spectra 40 degrees from
inlet
Third-octave sound pressure level spectra 80 degrees from
inlet
Third-octave sound pressure level spectra 120 degrees from
inlet -
The ANOPP theoretical manual has been modified to reflect the
revisions in the Small Engine Revision procedure, see Appendix I.
Appendix IX contains a description of the ANOPP code changes.
31
5.0 REFERENCES
• Interim Prediction Method For Fan And Compressor Source Noise, M.
F. Heidmann, NASA Lewis Research Center, NASA TM X-71763, June
1975.
•Aircraft Noise Prediction Program Theoretical Manual, W.
Zorumski, NASA Technical Memorandum 83199, Parts 1 and 2.
E•
32
APPENDIX I
ANOPP THEORETICAL _ UPDATE
33
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48
APPENDIX II
MEASURED DATA VERSUS REVISED PREDICTION, GASP, AND RR.IDMANNENGINE 1
1/3-OCTAVE BAND LEVEL DIFFERENCES
FROM 1 TO 10 kRz, dB
49
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_PPENDIX III
MEASURED _ VERSUS REVISED PREDICTION, GASP, ARD HEIDMRJNENGINE 2.
I/3_VE BRRD LEVEL DIFFERENCESFROM I TO I0 kHz, dB
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MEASURED DA_% VERSUS REVISED PREDICTION, GASP, RJND HEIDMANNENGINE 3
I/3_VE BAND LEVEL DIFFERENCES
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MEASURED DATA VERSOS REVISED PREDICTIOI, GASP, ARD RRIDM_RNBGINE 1
I/3-OCClVE BAND LEVEL DIFFERENCES
1 TO 10 kCz, cB
120
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ME/_SORED D3L_I VERSOS REVISED PREDICTION, GILSP, Z%RD HEIDMAB_ENGIRE 2
1/3-OC21VE BARD LEVEL DIFFERIWCES
FROM 1 TO I0 EHZ, dB
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J_PPERDIXVII
MEASURED _ VERSUS REVISED PREDICTION, C_LqP, AND HEIDMANNENGIRE 3
1/3-OCTAVE BARD LEVEL DIFFERENCESFRCE I TO I0 EHZ, dB
134
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139
APPEHDIX VIII
S_LL _GIHE R_VlSIOM F/%N NOISE PREDICTIONTEST C2&SE
140
Engine #1 Input parameters for Small Engine Revision test case
Engine Information:Fan blade #:
Stator blade #:
Fan speed,rpm:Fan blade pass,Hz:
Fan physical flow,lb/s:Fan diameter,R:
Inlet total temp,°R:
Discharge total temp,°R:Rel. Tip mach #:
T,°R:Rel. Tip mach # (design):
RSS, %:Reference mass flow,lb/s:
Reference total temp,°R:
GASP(G), Heidmann(H), or Small Engine Revision(J)?(G,H,J):
Enqine #13O61
100065OO3
132.48
2.455537617
1.20080
1.44(17(
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151
APPENDIX IX
SNALL ENGXI_ REVISION USER'S MANUAL
_NOPP CODE DKVKLOPMKHT
152
The small engine revision routine discussed in this report can be accessed in
ANOPP through the USER PARAMETERS data input as shown in the attached data
input section. Under USER PARAMETERS_METHOD:
T provides the original Heidman method
whereas,
'2' provides the AJliedSignal Small Engine Method.
The specific changes used in the small engine method have been provided in
Appendix I. An electronic version of the coded changes will be provided to NASA
following approval of the proposed small engine revision module.
153
_ee
.
.
.
.
PURPOSE ° PREDICT THE BROADBAND NOISE AND PURE TONES FOR AN
AXIAL FLOW COMPRESSOR OR FAN BY THE HEIDMAN METHOD
REFERENCE - NASA TM X-71763, INTERIM PREDICTION
METHOD FOR FAN AND COMPRESSOR SOURCE NOISE, M. F.
HEIDMAN
AUTHOR - CBF(L03/00/00)
DSW( )INPUT
USER PARAMETERS
AE - ENGINE REFERENCE AREA (RS), M**2 (FT**2)
RS - DISTANCE FROM SOURCE TO OBSERVER (RS), M (FT)
AFAN - FAN INLET CROSS-SECTIONAL AREA (RS), RE AE
DIAM - FAN ROTOR DIAMETER (RS), RE SQRT(AE)MD - FAN ROTOR RELATIVE TIP MACH NUMBER AT DESIGN
POINT (RS)
RSS - ROTOR-STATOR SPACING (RS), RE MEAN ROTOR BLADE
CHORD
MDOT - MASS FLOWRATE (RS), RE REOA * CA * AE
MA - AIRCRAFT MACH NUMBER (RS)
N - ROTATIONAL SPEED (RS), RE CA/DIAM
DELTAT - TOTAL TEMPERATURE RISE ACROSS FAN (RS), RE TA
CA - AMBIENT SPEED OF SOUND (RS), M/S (FT/S)
REOA - AMBIENT DENSITY (RS), KG/M**3 (SLUG/FT**3)
METHOD - PREDICTION METHOD FLAG
i, ORIGINAL HEIDMAN METHOD
2, ALLIEDSIGNAL SMALL ENGINE METHOD
NBANDS - NUMBER OF 1/3 OCTAVE BANDS FOR TONE FREQUENCY
SHIFT (I)NENG - NUMBER OF ENGINES (I)
NB - NUMBER OF ROTOR BLADES (I)
NV - NUMBER OF STATOR VANES (I)
IGV - INLET GUIDE VANE INDEX (I)
i, FOR A FAN WITH NO INLET GUIDE VANES
2, FOR A FAN WITH INLET GUIDE VANES
DIS - INLET FLOW DISTORTION INDEX (I)
i, IF THERE IS NO INLET FLOW DISTORTION
2, IF THERE IS INLET FLOW DISTORTION
STIME - SOURCE TIME (RS)
IOUT - TABLE OUTPUT AND PRINT OUTPUT OPTION (I)
0 NO PRINT BUT GENERATE TABLE HDNFAN(XXXNNN)
-i PRINT OUTPUT IN DB UNITS, BUT DO NOT
GENERATE TABLE HDNFAN(XXXNNN)
-2 PRINT OUTPUT IN DIMENSIONLESS FORM BUT DO
NOT GENERATE TABLE HDNFAN (XXXNNN)
-3 BOTH OPTIONS -i AND -2
1 PRINT OUTPUTIN DB UNITS AND GENERATE TABLE
RDNFAN(XXXNNN)
2 PRINT OUTPUT IN DIMENSIONLESS FORM AND
GENERATE TABLE RDNFAN(XXXNNN)3 BOTH OPTIONS 1 AND 2
IPRINT - PRINT FLAG (I)0 NO PRINT DESIRED
1 INPUT PRINT ONLY
2 OUTPUT PRINT ONLY
3 BOTH INPUT AND OUTPUT PRINT
SCRNNN - INTEGER VALUE, NNN, .GT. 0 USED TO FORM TABLE
UNIT MEMBER NAME HDNFAN(XXXNNN)
SCRXXX - THREE LETTER CODE XXX USED TO FORM TABLE UNIT
MEMBER NAME HDNFAN(XXXNNN)
IUNITS - INPUT UNITS FLAG
7HENGLISH, ENGLISH UNITS
2HSI, SI UNITS
154
t
e
e
(THE NEXT SIX CODES HAVE THE FOLLOWING VALUES)
(. FALSE.
(. TRUE.
INRS
INCT
INDIS
IDBB
IDRS
INBB
DO NOT INCLUDE )
- INCLUDE IN TOTAL PREDICTION )
INLET ROTOR-STATOR INTERACTION TONES
COMBINATION TONE NOISE
INLET FLOW DISTORTION TONES
DISCHARGE BROADBAND NOISE
DISCHARGE ROTOR°STATOR INTERACTION TONES
INLET BROADBAND NOISE
REAL USER PARAMETER LIMITS - SI UNITS
PARAMETER MINIMUM MAXIMUM
AE 0.01 50.0
RS 0.01 i00.0
AFAN 0.1 i0.0
DIAM 0.3 4.0
MD 0.5 2.0
RSS 0.2 i0.0
MDOT 0.0 I0.0
MA 0.0 0.9
N 0.0 0.5
DELTAT 0.0 i. 3
CA 0.0 400.0
RHOA 0.0 i. 5
STIME -i00.0 500.0
DEFAULT
0.785398
0. 886227
1.0
1.128
1.0
1.0
0.2
0.0
0.3
0.2
340.294
1.225
0.0
REAL USER PARAMETER LIMITS - ENGLISH UNITS
PARAMETER MINIMUM MAXIMUM DEFAULT
AE 0. 1076 500.0 8. 454
RS 0.03281 328.084 2.908
AFAN 0.I I0.0 1.0
DIAM 0.3 4 .0 i. 128
MD 0.5 2.0 1.0
RSS 0.2 10.0 1.0
MDOT 0 .0 I0 .0 0.2
MA 0.0 0.9 0.0
N 0.0 0.5 0.3
DELTAT 0.0 I. 3 0.2
CA 0.0 1312 .336 1116.45
RHOA 0.0 0 .0029105 0. 0023769
STIME -I00.0 500.0 0.0
INTEGER/LOGICAL/ALPHA PARAMETER LIMITS
PARAMETER
METHOD
DIS
IGV
IOUT
IPRINT
NB
NBANDS
NENG
NV
SCRNNN
INRS
INCT
INDIS
IDBB
IDRS
INBB
SCRXXX
IUNITS
MINIMUM MAXIMUM
1 2
1 2
1 2
-3 3
0 3
2 i00
-3 3
1 6
i0 200
001 999
DEFAULT
1
1
1
3
3
20
0
1
50
001
.TRUE
•TRUE
.TRUE
.TRUE
.TRUE
•TRUE
3HXXX
2HSI
155
DATA BASE UNIT MEMBERS
(DESCRIBED UNDER DATA BASE STRUCTURES)
SFIELD (FREQ )
SFIELD (THETA)
SFIELD (PHI)
e
e
**e
OUTPUT
USER PARAMETERS
RS DISTANCE FROM SOURCE TO OBSERVER
SYSTEM PARAMETERS
NERR .TRUE., IMPLIES AN ERROR WAS ENCOUNTERED
DURING MODULE EXECUTION
.FALSE., NO ERROR ENCOUNTERED
DATA BASE UNIT MEMBERS
HDNFAN(XXXNNN) SEE FORMAT UNDER DATA BASE STRUCTURES.
NOTE MEMBER NAME XXXNNN IS FORMED
FROM USER PARAMETERS SCRXXX AND SCRNNN.
OUTPUT OF THIS TABLE IS CONTROLLED
BY USER PARAMETER IOUT.
DATA BASE STRUCTURES
SFIELD(FREQ) - 1 RECORD MEMBER IN *RS FORMAT
CONTAINING VALUES OF 1/3 OCTAVE BAND
CENTER FREQUENCIES IN HZ
SFIELD(THETA) " 1 RECORD MEMBER IN *RS FORMAT
CONTAINING VALUES OF THE POLAR
DIRECTIVITY ANGLE IN DEG
SFIELD(PHI) - 1 RECORD MEMBER IN *RS FORMAT
CONTAINING VALUES OF THE AZIMUTHAL
DIRECTIVITY ANGLE IN DEG
HDNFAN(XXXNNN) - TYPE 1 TABLE CONTAINING MEAN SQUARE
ACOUSTIC PRESSURE AS A FUNCTION OF
(i) FREQUENCY, (2) DIRECTIVITY ANGLE
AND (3) AZIMUTHAL ANGLE
ERRORS
NON- FATAL
i. INSUFFICIENT LOCAL DYNAMIC STORAGE.
2. MEMBER MANAGER ERROR OCCURRED ON SPECIFIED UNIT
MEMBER.
FATAL - NONE
REMARKS
REFERENCES
HEIDMAN, M. F., INTERIM PREDICTION METHOD FOR FAN
AND COMPRESSOR SOURCE NOISE, NASA TM X-71763,
JUNE 1975.
HOUGH, J. AND WEIR, D., ANOPP FAN NOISE PREDICTION FOR
SMALL ENGINES, ALLIEDSIGNAL ENGINES REPORT 21-8700,
JANUARY 1995.
LDS REQUIREMENTS
LENGTH " (NFREQ * NTHETA * NPHI) + (NTHETA * NPHI)
+ NFREQ + NTHETA + NPHI + 3 * ( NFREQ * NTHETA )+ NTHETA
WHERE
NFREQ - NUMBER OF FREQUENCY VALUES
NTHETA - NUMBER OF DIRECTIVITY ANGLES
NPHI - NUMBER OF AZIMUTHAL ANGLES
GDS REQUIREMENTS
SUFFICIENT ALLOCATION FOR TABLE HDNFAN(XXXNNN)
156
APPENDIX X
INTERIM PREDICTION METHOD FOR 1FAN ARD CXJMPRESSOR SOURCE NOISE-
(FIGURES}
AI_ NOISE PREDICTION_PROGRAMTHEORETICAL lu_nJ_L-
(TABLES)
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175
TABLE IV.- SPECTRUM FUNCTIONS FOR FAN NOISE
Source Spectrum function
S(D) = 0.116 exp -0.DE in 2.2
Inlet
broadband
noise
Inlet
rotor-stator
interaction
tones
iInlet flow
distortion
tones
1/8 funda-
mental
combination
tone noise
n u
S(n) = _ S (n,i,j)
where
n=n£
S(l,i, j) =
-o.499 0.136
0.799 0.387
S(n,i,j) =
10.250 0.432
0.101 0.307m
n u
S (n) = 9 _ i0 -n
n=n£
x i0 -0"3 (n-2)
S(_) = ! 0"405(8n)50.405(8n) -3
(n > I)
(TI -< 0.125)
(_ > 0.125)
176
TABLE IV.- Concluded
Source Spectrum function
1/4 funda-
mental
combination
tone noise
1/2 funda-
mental
combination
tone noise
Discharge
broadband
noise
Discharge
rotor-stator
interaction
tones
s(q) =0. 520 (4q)
0.52O (4n) -5
s(n)= I 0"332(2n)3
O. 332 (2n)-3
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s(n) =
nu
S(n,i,j)
n=n£
where
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-0.499
0.799m
0.136-
0.387
S (n,i, j) =
-0.250
0.i01
0.432
0.307
x I0 -0" 3 (n-2)
(q -< 0.25)
(rl > 0.25)
(n -< o.5)
(n > 0.5)
(n > i)
177
FormApprovedREPORT DOCUMENTATION PAGE OMBNo. 0704-0188
1. AGENCYUSEONLY(LNm blank) 2. REPORTDATE 3. REPORTTYPEANDDATESCOVERED
Apd11996 Contractor Report4. TITLEANDSUBITTLE
Aircraft Noise Prediction Program (ANOPP) Fan Noise Prediction for Small
Engines
6. AUTHOR(S)
Joe W. Hough and Donald S. Weir
7. PERFORMINGORATION NAME(S)ANDADORESS(ES)
Lockheed AeronauUcal Systems Company (SubconlTactor)86 South Cobb Drive AlliedSignal EnginesMarietta, GA 30063 P.O. Box 52181
Phoenix, AZ 85072
9. SPONSORING/MONITORINGAGENCYNAME(S)ANDADDRE$S(ES)
National Aeronaubcs and Space AdministrationLangley Research CenterHampton, VA 23681-0001
5. FUNDINGNUMBERS
NAS1-20102, Task 653803-11-01
8. PERFORMINGORGAWZATIONREPORTNUMBER
21-8700
10.SPONSORINGI MoNrrORINGAGENCYREPORTNUMBER
NASA CR-198300
11. SUPPLEMENTARYNOTES
Langley Technical Monitor: Robert A. GolubFinal Report
12a.DISTRIBUTIONI AVAILABILJTYSTATEMENT
Unclassified-Unlimited
Subject Category 71
12b.DISTRIBUTIONCOOE
13.ABSTRACTI'Mwxknum200words)
The Fan Noise Module of ANOPP is used to predict the broadband noise and pure tones for axial flow
compressors or fans. The module, based on the method developed by M. F. Heidmann, uses empiricalfunctions to predict fan noise spectra as a function of frequency and polar directivity. Previous studies havedetermined the need to modify the module to better correlate measurements of fan noise from engines in the3000- to 6000-pound thrust class. Additional measurements made by AlliedSignal have confirmed the need to
revise the ANOPP fan noise method for smaller engines. This report descdbes the revisions to the fan noisemethod which have been verified with measured data from three separate AlliedSignal fan engines.Comparisons of the revised prediction show a significant improvement in overall and spectral noise predictions.
14.SUBJECTTERMS
Jet Engine Noise, Fan Noise, ANOPP Noise Prediction, Fan Noise Spectra,Heidmann Fan Noise Code
17.SECURITYCLASSIFICATIONOFREPORT
Unclassified
:18.SECURITYCLASSIFICATIONOFTHISPAGE
Unclassified
11. SECURrrYCLASSIFICATIONOFABSTRACT
15. NUMBEROFPAGES
180
16. PfllCECOOE
A09
20. LIMITATIONOFABSTRACT
NSN 7540-01-280-5500 StandardForm29e (Rev.2-1)))Pm_cnl_dbyANSISial.Z3e-18_.lrn
