Airport community acceptance of High Speed Civil Transport (HSCT) noise levels will depend on the relative noise levels of airplanes flying at the time of introduction. The 85 dBA noise contours for the range of large subsonic airplanes that are expected to be in service in the early 21st century are shown as a shaded area. A certifiable HSCT noise contour as shown, would be somewhat wider along the runway, but about the same in the residential areas downrange. An HSCT noise rule should insure this noise capability

Nihart, Gene L.

English

NASA Technical Reports Server

N94-33490
COMMUNITY NOISE TECHNOLOGY NEEDS
BOEINGS PERSPECTIVE
G. L. Nihart
Boeing Commercial Airplane Group
Seattle, Washington
High Speed Research
First Annual Workshop
May 14-16, 1991
PRECEDING PAGE BLANK NOT FILMED 1105
https://ntrs.nasa.gov/search.jsp?R=19940028984 2020-06-16T13:10:30+00:00Z
COMMUNITY NOISE TECHNOLOGY NEEDS
BOEING PERSPECTIVE
:_ NOISE REQUIREMENTS (NOISE CONTOURS)
:_ NOISE SOURCES
JET NOISE PREDICTION TECHNOLOGY
- JEN3RC (EMPIRICAL)
' JEN8 (SEMI-EMPIRICAL)
FLOW UNDERSTANDING:
- FLOW VISUALIZATION
- CFD MODELING
:_ OTHER PREDICTION TECHNOLOGY NEEDS
:_ PREDICTION ACCURACY AND CONFIDENCE LEVELS
:_ CONCLUSIONS
FIGURE 1
FIGURE 2
FIGURE 3
FIGURE 4
FIGURE 5
FIGURES 6, 7
FIGURE 8
FIGURES 9, 10
FIGURES 11, 12
1106
AIRPORTCOMMUNITY ACCEPTANCE
Airport communityacceptanceof HSCT noiselevelswill dependon the relativenoiselevels
to airplanesflying at the time of introduction. The 85 dBA noise contours for the range of
large subsonic airplanes that are expected to be in service in the early 21st century are
shown as a shaded area. A certifiable HSCT noise contour, as shown, would be somewhat
wider along the runway but about the same in the residential areas downrange. An HSCT
noise rule should insure this noise capability.
COMMUNITY NOISE
85 dBA FOOTPRINTS
HSCT Range of Large Subsonic Airplanes
1<_ 1 Mite _>l
FIGURE I
1107
COMMUNITY NOISE SOURCES
Jet noiseis theprimarynoisesourceat the sidelinemeasuringpoint but at the downrange
and approachmeasuringpointsburnernoise isalsoimportantIn addition turbine and air-
framenoiseare importantsourcesduringapproach.Predictionaccuracyfor all of the
sourcesandfor noisereductionfeatures,suchastile jet exhaustnoisesuppressionnozzle,
will havea major impacton designfeaturessuchasenginesizing.
120
116
112
108
104
EPNdBo o
96
92
i
84
80
_Hardwall NWith Suppression I
I CUTBACK 20% PLR 1
U
Yolal Comp. BurnerTurbine Jet
110
108-
106-
104
102-
EPNdB 100
98-
96
94
92
90-
Stage 3
Figure 2
12°/116 --12
108 ._
EPNdB 1°4
1oo
96
92
88
84
80
APPROACH
SIDELINE 20% PLR
Total Comp. BurnerTurbine Jei ,,
_ Stage 3
-N
aN
88
Total Comp. BurnerTurbino Jet Airframe
Noise Components Turbine Bypass Turbojet Engine
Stage 3
1108
JET NOISE PREDICTION TECHNOLOGY
CURRENT PROCEDURES ARE :
* EMPIRICAL
* PREDICT UNSUPPRESSED JET ; ie, R-C
* PREDICT SPECIFIC SUPPRESSION CONFIGURATIONS
IDEAL PROCEDURE :
* ANALYTICAL PROCEDURE THAT PREDICTS ABSOLUTE LEVELS
" FLEXIBLE SUCH THAT SUPPRESSION DEVICES CAN BE SCREENED
* USES PREDICTABLE FLOW PARAMETERS OR RESULTS OF CFD
MODELING
FIGURE 3
1109
NFM NOZZLE PREDICTION VERSUS DATA
The basic low bypass ratio jet noise prediction program at Boeing is empirical
and is for a round convergent (RC) nozzle. This program was used to predict
externally generated noise based on the fully mixed stream and the internal noise
from one of the primary nozzles using the aspirated flow as the free stream. The
predicted noise levels are then added. Shock cell noise predicted for the primary
nozzle is reduced by 7 dB to account for the convergent-divergent (CD)
expansion of the primary nozzle.
25
20
t
Z
o
a. 15
10
1110
_[ Pre-Testr diction ]
7"
I{.W.
X
X = Prediction
0= Data
X = Modified
Prediction.
• Long Shroud
X
Medium Shroud
"ShortShroud
t I 1___1.... 1 I I I I
"EFFECTIVE" LINING LENGTH - AI/,'_I
I I 1 I I I 1
[ FI__._GURE4, NFM NOZZLE PREDICTION VS DATA ]
JET NOISE PREDICTION PROCEDURE DE\,'ELOPMENT
A computer prediction program is being developed at Boeing incorporating the recent
nozzle test data modeling externally generated mixing noise, internally generated
mi:,dng noise and internal shock cell noise components. A status comparison to test
data in the forward and aft arc are shown.
H S C T JET NOISE
SEMI-EMPIRICAL COMPONENT MODELLING
TO GUIDE NOZZLE / AIRPLANE DEVELOPMENT
Forward Radiated Aft Radiated
:'°t _ r i
:_°1 ; t A
85
"70
oo.11
I I I I I
t mas_re_--k
/-A_ i\
_ . -_ -
xmg--q_ _
Sh4ck I_ I t 'X.
22 24 26 28 30 .32 34 36 38 40 42 44
_JAND
,,_! d I
15 ur -"--""_ I
_,,o-r ' I ._t ,
.... ]
[..... !' Z2
22 24 26 28 30 32 34 36 38 40 42 44 46
1111
FIGURE 5
CROSS-CORRELATIONSTUDIES
Techniquesarebeingstudiedto cross-correlateinternal fluctuatingjet velocities
with far field soundpressure.If this is successful,noisesourcelocationsand
their frequencycharacteristicscanbedeterminedinsidethe ejector.This would
be usefulin improvingthemixer nozzleandejector lining designs.
z_Zg;2WzT,6_f_'
APPLICATION OF CROSS CORRELATION TECHNIQUES
Present Opportunities for Better Under-
standing of Internal Noise Sources
<:_ Nozzle
P
/
Signal Processing:
Sampling, Recording, Fil-
tering, Differentiating,
Multiplying, Cross-Corre-
lating
1112
FIGURE 6
SIMULATED CROSS-CORRELATIONRESULTS
In order to determinethe numberof samples(proportional to processingtime) needed
to obtain usefulcross-correlationfunctions,a digitally simulatedrandomtest signal
wasburied in a noisesignalanddelayed.Resultingcross-correlationsbetweenthe
secondderivativeof the original testsignalandthe testandnoisesignalcombination,
areshownwherethesignalto noiseratio isabout 10.The reducionin thevariancein
the correlationwith increasingnumberof samplesisevident.Frequencycharacteristics
areobtainedby fourier transformingthecrosscorrelation.
SIMULATED CROSS-CORRELATION
Results- Time Domain- Noise > Signal
g
c,..)
¢...,
._o
O
16K
Samples
Time Delay
.c2
O
64K co,
Samples
Time Delay
32K
Samples
Time Delay
128K
Samples
Time Delay
Idealized
Shape for
band-limited
noise:
I
FIGURE 7
1113
CFD AND NOZZLE DESIGN
ComputationalFluid Dynamics(CFD) hasthepotential of beinga very
usefultool in nozzledesign.CurrentlyCFD is usedto evaluatenew
designs,prior to fabrication,in order to find potential flow problems.
Datagatheredduringwind tunnel testingis usedto validateCFD
modelingincreasingconfidencein theCFD results.
Comparison of Coarse and Fine Grid Pressure Contours
Flow Conditions: PR1=3.5, TR1=1.01, PR2=1.16, TR2=1.01, M_--0.24
Coarse Grid
P/7P_
D. B2OO
D. BD50
O. 79DO
O. 775D
O, 76DO
D, 7450
l=il- o. 7a0o
- D.7150
- D, ?ODD
O. EBSO
O. GTOO
O. G550
- O. 6.400
- O. 525D
1- O. 5950
0. SOD0
- D. 5650
- D, 55D0
1114 FIGURE 8
OTHER PREDICTION TECHNOLOGY NEEDS
SIDELINE SHIELDING AND GROUND REFLECTION / ATTENUATION
* CURRENT METHODS ARE BASED ON H'BPR ENGINES AND SUBSONIC
AIRPLANE CONFIGURATIONS
INSTALLATION EFFECTS
* EFFECT ON SUPPRESSION SYSTEM
* NO[SE REFLECTION, ETC.
OTHER NOISE SOURCES
* TURBOMACHINERY
* BURNER NOISE (LOW EMISSION BURNERS)
* AIRFRAME NOISE
FIGURE 9
1115
SIDELINE SHIELDING PREDICTION
Current sideline shielding prediction programs were developed using sideline noise
measurements of 747 and 767 airplanes with the same engines. The shielding is
then for high bypass ratio engines mounted off of the leading edge of the wing and
with many configuration differences from current HSCT designs. There is currently
little capability to accuratly predict shielding sensitivities to configuration layout
changes.
Size Comparison
HSCT Versus 747-400
747-400
23! ft 10 in
311 ft
211 ft 5 in
132 ft
CO-318R1
G-8-1
P 1642,29 H
m
=
1116 FIGURE 10
DESIGN MARGIN IMPORTANCE
A designmarginon theorder of 80% confidencewill be requiredto launchan ItSCT
productionprogram.The currentstatusis lessthan 50% with a one sigma variation of
5. To reach 80% confidence will require irnprovements in the airplane, such as an im-
provements in the jet suppression nozzle, but will also require improved prediction
capability to reduce the variation.
9O
8O
V
JET NOISE SUPPRESSION AND
PREDICTION ACCURACY
EFFECT ON CONFIDENCE LEVEL
o 2 GOAL
g
7O
60
5O
4O
3O
[] 17
I I I I I I I I I I I I I I
18 19 20
Jet Suppression, delta EPNdB
FIGURE 11
1117
PREDICTION UNCERTAINTY SOURCES
Predictionuncertaintyincludesthe uncertaintyof eachof thecontributingnoisesources
(A-D). The total accumulatedmeasurementvariation includes(E) thesingletest
variability (datascatter)but also(F) any true error (bias).To improvethe total
predictionto demonstrationuncertainty(G) eachnoisesourcepredictionprocedure
shouldbeevaluatedfor accuracyand improvedif possible.Improvementsin prediction
of propagation,installationeffects,shielding,groundreflectionandairplane
performancewill alsobe required.
VALUE
PREDICTION UNCERTAINTY
(_( DISPLACED BY BIAS G )
+
VARIABILITY IN 1 ,,SCATTER, '
SINGLE TEST / • L ..
VAR,ABIL,T .
MEASURED
_ _MEAN (X)
"-TNRU E (p]
.%
DICTED []./}
I PREDICTION/
I TOOE,.:O/
!UNCERT, 'N I
CONDITION
1118 FIGURE 12
CONCLUSIONS
JET NOISE PREDICTIONS ARE PRIMARILY EMPIRICAL AND PREDICT TESTED NOZZLE
CONFIGURATIONS.
FLEXIBLE AND MORE ANALYTICAL PREDICTION PROCEDURES ARE NEEDED THAT
ACCURATELY PREDICT ABSOLUTE LEVELS.
ALSO, IMPROVEMENTS ARE NEEDED IN PREDICTION PROCEDURES FOR THE OTHER
NOISE SOURCES TOGETHER WITH IMPROVEMENTS IN INSTALLATION EFFECTS, SIDELINE
SHIELDING AND GROUND REFLECTION PREDICTIONS.
1119
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Community noise technology needs: Boeing's perspective

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