The topics covered include the following: community noise sources and noise control issues; noise components for turbine bypass turbojet engine (TBE) turbojet; engine cycle selection and noise; nozzle development schedule; NACA nozzle design; NACA nozzle test results; nearly fully mixed (NFM) nozzle design; noise versus aspiration rate; peak noise test results; nozzle test in the Low Speed Aeroacoustic Facility (LSAF); and Schlieren pictures of NACA nozzle

Nihart, Gene L.

English

NASA Technical Reports Server

I N94- 33467
COMMUNITY NOISE SOURCES
AND NOISE (?ONTROL ISSUES
G. 1.. Nihart
Boeing Commercial Airplane Group
Seattle, Washington
High Speed Research
First Annual Workshop
May 14-16, 1901
PRECEDIN3 PAC_E _L_.P4_ NL)T FILMED 593
https://ntrs.nasa.gov/search.jsp?R=19940028961 2020-06-16T13:11:01+00:00Z
COMMUNITY NOISE SOURCES AND NOISE
CONTROL ISSUES
• TURBINE BYPASS ENGINE (TBE) NOISE LEVELS
• JET NOISE CONTROL
_< ENGINE CYCLE IMPLICATIONS
_< NOZZLE DEVELOPMENT SCHEDULE
_< NOZZLE TEST RESULTS
- NACA NOZZLE
- NFM NOZZLE
• TEST TECHNOLOGY
• CONCLUSIONS
FIGURE 1
FIGURE 2
FIGURE 3
FIGURES 4, 5
FIGURES 6 - 8
FIGURES 9 - 11
594
NOISE COM PON ENTS TB E TU RBOJ ET
Unsuppressed levels for the Turbine Bypass Turbojet Engine (TBE) at each of tile
certification points indicates the suppression needed to achieve FAR 36 Stage 3.
At sideline 20 EPNdB jet noise suppression is needed, at cutback 16 EPNdB jet
noise and 2 EPNdB burner noise, at approach 6 EPNdB jet noise, 7 EPNdB
burner noise and 10 EPNdB suppression of turbine noise.
120
11
112-
108
104-
EPNdB00-
96"
92-
88"
84 _
8O
CUTBACK 20% PLR
Total Comp. Burner Turbine Jet
110
I08
Hardwall _With Suppression 106
104
102
EPNdB too
98
96
94
92
90
88
Figure 1
Stage 3
120
116
112
108
104
EPNdB
100
96
92
88
84
8O
APPROACH
SIDELINE 20% PI.P, _',x-X_
<
N
N
Total Comp, BumerTurbine Jet ,
Stage 3
Total Comp. BurnerTurbine Jet Airframe
Noise Components Turbine Bypass Turbojet Engine
Stage 3
595
ENGINE ('YCLE St_IJ_CTION AND NOISE
The engine cycle selection will determine the jet noise suppression required
from 20 EPNdB for the turbojet to less than 10 EPNdB for some of the low
specific thrust variable cycle engines. Undestanding of nozzle technology to
achieve 20 EPNdB suppression is needed to understand the engine cycle /
jet suppression trades.
Variable Cycle Engine Developments
Air.,,. _,_..
 1111 Turbine-Bypass :ETBUTREQUIRESNoISESUPP ESSION_20ePNde
urbojet Engine
NEXT BEST PROPULSION
_- First bypass
v-Second bypass --, PERFORMANCER QUIRES_18 EPNdB JET NOISE
_.. SUPPRESSION
__ Double-Bypass
Turbofan Engine
/
i Secondary
intake door F C°re flow
LOWESTPROPULSION _ "" / rBypass flow
PERFORMANCE BUT REQUIRES L---n_:_'_ \ \ \ \. . .,"-'-nd-g-___THELEASTget NOIS S PPRESSION
Tandem Fan Concept- _ _ "_
High-Bypass Mode _--___
Remote [ \'_, /.._ Secondaryfront tan----I _. , "--,--
High-bypass/_ exhausl duct
valve
I
FIGURE 2
596
NOZZLE I)I_VFA_OPMENTSCItEDULE
Model scalenozzledevelopmentestingwill continue through1995followed
byverificationtestingusinga largescaledemonstratorengine.Testsin 1991
includeelementsof the nearlyfully mixed(NFM) nozzle,avariable
geometryversionof the NFM nozzleand sourcediagnosticsof tile NFM
nozzle.Sourcediagnosticswill includecross-correlationof far field noise
with internalvelocityfluctuations.
NOZZLE DEVELOPblENT TESTING
TASKS 1990 i 1991 ; 1992 ; 1993 1994 i 1995
NOISE TESTING
NT2,4 ELEMENTS
VAR. GEOM. NFM LSAF
SOURCE DIAGNOSTICS
ENGINE CYCLE SELECTION
2 :
MOD,ZLSCALE.res"r_4
, o
3 : 4 5 6 '. 7 8 9 ' 10
r--q
v--n
[--1
[
LARGE SCALE
DEMO
,
i
FIGURE 3
597
_AI_A
NACA N()ZZIJ£ TI:_ST RESULTS
The mixing of the aspirated flow and the prinlary jet takes place outside of the
nozzle so that the primary sneam is at full velocity in the initial mixing region.
This results in large noise reduction down stream but no reduction of high
frequency noise generated in the initial mixing region limiting the suppression
to 10 EPNdB.
NATURALLY ASPIRATING CO-ANNULAR,
NOZZLE SOURCE LOCATION
NACA._
_0_0 C0_,'v[ _CEN_:_7_ '- _
_.--_-______-
Flow [",'off& Sckcmot_c
• L.L5
_.._,% FREQgENCY
,_,. SO,OHZ {UC.3[L)
"_ IC3HZ (FULLSCALE)
F m_ r
4 _ 12
O_SIANC[ ALO.',GO_{ ¢[N[ER LINE. gt_[_
_q¢;V_c afuror No.ue Soun:¢ Dtstnbueao,: Scan at a L_w F_que,acy
• P33
_20
-4
FIGURE 5
599
NI'M NOZZLE I)ESIGN
One solution to the NACA nozzle limitation is to mix the aspirated flow inside
a treated ejector and Boeings version of this nozzle is called the Nearly Fully
Mixed (NFM) nozzle. This nozzle aspirates 100 + % of the core flow, fully
mixes the core and aspirated flows inside the ejector and minimizes inte,nal
shock cell noise from the primary nozzle. The internally generated mixing and
shock cell noise is reduced with acoustic lining.
Internally Mixed Ejector- Suppressor
Nozzle Concept
Secondary air
(100+ % aspiration)
}ound attenuation lining
(7-10 dB attenuation'
Engine
exhaust
Mixing region
(minimum shock cell
and mixing noise)
Low-noise
mixed-velocity
stream
(Vim :- <: 1,500 It/see)
FIGURE 6
600
NOISEVERSUSASPII_,ATIONRAI'I;
Noisereductionof anaspiratingnozzlehastile potential of reducingnoiseto the
levelof anequivalentnozzlewith thefully mixedstreamflow conditions.lhc
noisereductionpotential of anaspiratingnozzleversusaspiraf,ion rate is shown.
NACA nozzleand NFM nozzledataarealsoshown.Neithernozzlereachesits
full potential, theNACA nozzlebecausethe streamsare mixedoutsidethe
nozzleandtile NFM nozzlebecausesomeinternallygeneratednoiseis still
radiatedout.
I:;PNI,
re:
S'FAG E 3
I IBASELINE AIRPI_.N E22 -- SIDELINE NOISE.
20 NSUPPRESSED
181--
14--
12 -- NACA NOZZI : NFM ItNOZZL
"1
10 -- N _Initial
8
-- _ gMixing • No Lining D;q'A POINTS
6 -- "x_Noise
- •
4 _ '_ Increased
PREDICTION \ ] 1 inim,
._ FU I.I.Y MIXED \ • I _
"-- SINGLE STREANL _ /
I
0 i I t 200
50 100 1_
AS,PIRtXI'ION RATE % CORE F'I.()W.
t:IGURI{ 7
601
PEAK N()ISE 'I'EST RESUI;I'S
The reference RC nozzle noise spectrum is shown at its peak radiation angle
(140 ° ) compared to the NACA and NFM nozzles at their peak angles (110°).
The high frequency noise reduction of the NACA nozzle is limited because
the mixing takes place outside the nozzle. The NFM nozzle, with the longest
treated ejector, shows large noise reductions at all frequencies.
NFM, NACA, and RC Nozzle Noise Comparison
5_
5 dB
ca
10
I
i i i _ , i i f i
i()0 l()'01)
full scale frctlucnc ),
i i i 1 i r
10000
602
FIGURE 8
TEST TECHNOLOGY
j NOISE SOURCE LOCATION TECHNIQUES
FLOW PARAMETER MEASUREMENT TECHNIQUES
TECHNIQUES FOR CROSS-CORRELATION OF NOISE
WITH FLOW PARAMETERS
FLOW VISUALIZATION TECHNIQUES
FIGURE 9
603
N()ZZLE TESF IN I.SAI:
A nozzle test in progress m tile l.ow Speed Aeroacoustic I:'dcilit,, (I SAI:) wind tunnel
at Boeing. The 9' X 12' trcc jet m>zzle is shown as well as nlicro[_ht_m: h>catiom,.
The translating elliptic mirror microphone is used to determine tht,, n_c _ourcc
location. Far field noise measurements are made at 20 ft. sideline, di,,t<ince with lixed
microphones out of the tunnel flow and within the t]o,a with tr_tr>,l_ltiu_ micr<+ph_mcs
at 4.7 ft.
BOEING I
604
S(:IIIJI_RI_N PI(71UI(I,IS ()1, NA('A N()ZZI.t.I
lqow visualization pictures taken by Jack Neincr's group fronl NASA l.angley
are shown. 'lhcsc pictures of the NA(:A nozzle lcsl show the effect of
translating the outer shroud length on shock cell slrength. As the shroud was
translated the expal_sion ratio (A/A*) was changing.
SCHLIEREN RECORDS FOR
CONFIGURATIONS 2.3 AND 2.1
(NPR--3.5, M T-0-23, FfPA-1000_'F, WBP ON)
CONFIG 2.3
LS
CONFIG 2.1
+0.5"
0 5"I •
-1.3"
2 0"
°
FIGURE 11
605
CONCLUSIONS
._'-AN HSCT WILL REQUIRE NOISE CONTROL OF SEVERAL NOISE SOURCES, IN PARTICULAR JET
NOISE, TO GET AIRPORT COMMUNITY ACCEPTANCE
>_ ENGINE EXHAUST NOZZLE TECHNOLOGY DEVELOPMENT IS NEEDED TO ESTABLISH THE
PENALTIES FOR 20 EPNDB SUPPRESSION SO THAT ENGINE CYCLE AND AIRPLANE TRADE
STUDIES CAN BE MADE
>}_IMPROVEMENTS IN JET NOISE TEST TECHNOLOGY AND PREDICTION TECHNOLOGY WOULD
GREATLY ENHANCE THE NOZZLE DEVELOPMENT EFFORT
6O6


Community noise sources and noise control issues

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