Improved NASA-ANOPP Noise Prediction Computer Code for ...

NASA Contractor Report 195480

: /

Improved NASA-ANOPP Noise Prediction

Computer Code for Advanced Subsonic

Propulsion SystemsVolume 1" ANOPP Evaluation and Fan Noise Model

Improvement

K. B. Kontos, B. A. Janardan, and P. R. Gliebe

GE Aircraft Engines

Cincinnati, OH

August, 1996

Prepared forNASA Lewis Research Center

Under Contract NAS3-26617

Task Order Number 24

Table of Contents

List of Figures ........................................................................................................ iv

List of Tables ......................................................................................................... v

Nomenclature ......................................................................................................... vi

1.0 Summary .................................................................................................... 1

2.0 Introduction ............................................................................................... 2

3.0 Results and Discussion -- ANOPP Evaluation .......................................... 3

3.1 Overall Results ............................................................................... 6

3.2 Fan Inlet Noise ............................................................................... 10

3.3 Fan Exhaust Noise .......................................................................... 12

3.4 Jet Noise ......................................................................................... 14

3.5 Combustor Noise ............................................................................ 16

3.6 Turbine Noise ................................................................................. 18

4.0 Results and Discussion -- Fan Noise Model Improvements ........................ 21

4.1 Fan Inlet Broadband Noise .............................................................. 22

4.2 Fan Exhaust Broadband Noise ........................................................ 25

4.3 Fan Inlet Discrete Tone Noise ......................................................... 27

4.4 Fan Exhaust Discrete Tone Noise ................................................... 32

4.5 Directivity ...................................................................................... 34

4.6 Combination Tone Noise ............................................................... 37

4.7 Summary of Fan Noise Methodology Changes ............................... 43

Concluding Remarks .................................................................................. 45

A. Sample ANOPP Input ..................................................................... 46

B. Fan Inlet Noise Spectral Comparisons - CF6-80C2 ......................... 50

C. Fan 63

D. Fan 70

E. Fan 77

5.0

Appendix

Appendix

Appendix

Appendix

Appendix

- E °ooooo ..... oo°°oooo°oo°°°o°oo°oo°° ....Inlet Noise Spectral Comparisons 3

Inlet Noise Spectral Comparisons - QCSEE .............................

Exhaust Noise Spectral Comparisons - CF6-80C2 ....................

Appendix F.

Appendix G.

Appendix H.

Appendix I.

Appendix J.

Appendix K.

Appendix L.

Appendix M.

6.0

Fan Exhaust Noise Spectral Comparisons - E 3................................ 102

Fan Exhaust Noise Spectral Comparisons - QCSEE ........................ 109

Jet Noise Spectral Comparisons, 150 degrees ................................. 116

Combustor Noise Spectral Comparisons, 120 degrees ..................... 120

Turbine Noise Spectral Comparisons, 120 degrees ......................... 124

Directivity, CF6-80C2 and QCSEE ................................................ 128

Combination Tone Noise Spectra - CFM56 .................................... 133

Combination Tone Noise Spectra - CF6-80C2 ................................ 142

References .................................................................................................. 147

ill

List of Figures

Figure 3.0.1

Figure 3.0.2

Figure 3.0.3

Figure 3.0.4

Figure 3.1.1

Figure 3.1.2

Figure 3.1.3

Figure 3.1.4

Figure 3.1.5

Figure 3.1.6

Figure 3.2.1

Figure 3.2.2

Figure 3.2.3

Figure 3.3.1

Figure 3.3.2

Figure 3.3.3

Figure 3.4.1

Figure 3.4.2

Figure 3.4.3

Figure 3.5.1

Figure 3.5.2

Figure 3.5.3

Figure 3.6.1

Figure 3.6.2

Figure 3.6.3

Figure 3.6.4

Figure 4.1.1

Figure 4.1.2

Figure 4.1.3

Figure 4.2.1

Figure 4.2.2

Figure 4.2.3

Figure 4.3.1

Figure 4.3.2

Figure 4.3.3

CF6-80C2 Engine .............................................................................

E 3 Engine ..........................................................................................

QCSEE Engine .................................................................................

Sample E 3 Component Noise Spectrum ............................................

ANOPP Summary, CF6-80C2, forward peak angle ...........................

ANOPP

ANOPP

ANOPP

ANOPP

ANOPP

Summary, E 3 , forward peak angle ......................................

Summary, QCSEE, forward peak angle ...............................

Summary, CF6-80C2, aft peak angle ...................................

Summary, E 3 , aft peak angle ..............................................

Summary, QCSEE, aft peak angle ......................................

Fan Inlet Noise Spectrum, CF6-80C2 ................................................ 11

Fan Inlet Noise Spectrum, E 3 ........................................................... 11

Fan Inlet Noise Spectrum, QCSEE .................................................... 12

Fan Exhaust Noise Spectrum, CF6-80C2 .......................................... 13

Fan Exhaust Noise Spectrum, E 3 ...................................................... 13

Fan Exhaust Noise Spectrum, QCSEE .............................................. 14

Jet Noise Spectrum, CF6-80C2 ......................................................... 15

Jet Noise Spectrum, E 3...................................................................... 15

Jet Noise Spectrum, QCSEE ............................................................. 16

Combustor Noise Spectrum, CF6-80C2 ............................................ 17

Combustor Noise Spectrum, E 3......................................................... 17

Combustor Noise Spectrum, QCSEE ................................................ 18

Turbine Noise Spectrum, CF6-80C2 ................................................. 19

Turbine Noise Spectrum, E 3.............................................................. 19

Turbine Noise Spectrum, QCSEE ..................................................... 20

Turbine Noise Adjustment ................................................................ 20

"Figure 4a" CF6-80C2 Fan Inlet Broadband Noise ........................... 23

"Figure 4a" E' Fan Inlet Broadband Noise ......................................... 24

"Figure 4a" QCSEE Fan Inlet Broadband Noise ............................... 24

"Figure 4b" CF6-80C2 Fan Exhaust Broadband Noise ...................... 25

"Figure 4b" E ' Fan Exhaust Broadband Noise ................................... 26

"Figure 4b" QCSEE Fan Exhaust Broadband Noise .......................... 27

"Figure 10a" CF6-80C2 Fan Inlet Tone ............................................ 28

"Figure 10a" E ' Fan Inlet Tone ......................................................... 29

"Figure 10a'" QCSEE Fan Inlet Tone ................................................ 29

iv

List of Figures (continued)

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

Figure

4.4.1

4.4.2

4.4.3

4.5.1

4.5.2

4.5.3

4.5.4

4.6.1

4.6.2

4.6.3

4.6.4

4.6.5

4.6.6

4.6.7

"Figure 10b" CF6-80C2 Fan Exhaust Tone ....................................... 32

"Figure 10b" E' Fan Exhaust Tone .................................................... 33

"Figure 10b" QCSEE Fan Exhaust Tone ........................................... 33

"Figure 7a" Fan Inlet Broadband Directivity Correction .................... 34

"Figure 13a" Fan Inlet Tone Directivity Correction ........................... 35

"Figure 7b" Fan Exhaust Broadband Directivity Correction ............... 35

"Figure 13b" Fan Exhaust Tone Directivity Correction ..................... 36

"Figure 14" Combination Tone Noise Spectrum Content ................... 37

Combination Tone Noise Spectra, CFM56, M,= 1.2 ......................... 38

Combination Tone Noise Spectra, CFM56, M_= 1.32 ........................ 39

Combination Tone Noise Spectra, CFM56, M_ = 1.43 ...................... 39

"Figure 15" Combination Tone Noise, f/fb = 1/2 ............................... 40



List of Tables

Table 3.0.1

Table 3.2.1

Table 4.3.1

Table 4.6.1

Engine Summary - Typical Takeoff Condition ................................... 4

Rotor Tip Relative Inlet Mach Number ............................................. 10

Flight Cleanup Suppression Table ...................................................... 31

Combination Tone Noise Levels ......................................................... 42

v

Nomenclature

ANOPP ................................. Aircraft Noise Prediction Program

B ........................................... number of fan blades

BPF ....................................... blade passing frequency

dB ......................................... decibel

E 3 ......................................... Energy Efficient Engine

f/fb ......................................... ratio of frequency to BPF frequency

F .......................................... normalized SPL

GE ........................................ General Electric

IGV ...................................... inlet guide vane

k ........................................... harmonic order

L c.......................................... characteristic peak SPL, dB

Lo.......................................... normalized peak sound pressure level, dB

m .......................................... airflow, lb/s

mo. ........................................ reference airflow, Ibis

M, ......................................... fan blade tip Mach number

M, or MTR ........................... rotor tip relative inlet Mach number

M,_ or MTRD ....................... rotor tip relative inlet Mach number at fan design point

MPT ..................................... multiple pure tone

NASA ................................... National Aeronautics and Space Administration

RSS ...................................... Rotor/Stator Spacing (in % of blade chord length)

SPL ...................................... Sound Pressure Level, dB

AT ........................................ delta T (total temperature rise across fan stage), deg R

AT o....................................... reference value of AT, 1 deg R

TCS ...................................... turbulence control screen

UHB ..................................... Ultra High Bypass

V .......................................... number of stator vanes

QCSEE ................................. Quiet, Clean, Short Haul Experimental Engine

8 ........................................... fan inlet tone cutoff ratio

0 ........................................... Angle relative to engine inlet, deg.

vi

1.0 Summary

Recent experience using ANOPP (Aircraft Noise Prediction Program) to predict

turbofan engine flyover noise suggests that it over-predicts overall EPNL by a significant

amount. An improvement in this prediction method is desired for system optimization

and assessment studies of advanced UHB engines.

An assessment of the ANOPP fan inlet, fan exhaust, jet, combustor, and turbine noise

prediction methods was made using static engine component noise data from the CF6-

80C2, E 3, and QCSEE turbofan engines. It was shown that the ANOPP prediction

results are generally higher than the measured GE data, and that the fan inlet noise

prediction method (Heidmann method) is the most significant source of this

overprediction. Fan noise spectral comparisons show that improvements to the fan tone,

broadband, and combination tone noise models are required to yield results that more

closely simulate the GE data.

Suggested changes that yield improved fan noise predictions but preserve the Heidmannmodel structure were identified and are described herein. These changes are based on the

engine data sets mentioned above, as well as additional CFM56 engine data that was used

to expand the combination tone noise database. It should be noted that the recommended

changes are based on an analysis of engines that are limited to single stage fans with

design tip relative mach numbers greater than one.

2.0 Introduction

The purpose of the Aircraft Noise Prediction Program is to predict aircraft noise with

the best currently available methods (GiUian, 1982). The task of predicting the aircraftnoise is divided in to four areas within ANOPP:

1. Aircraft Flight Definition

2. Source Noise Modeling

3. Propagation and Ground Effects

4. Noise Calculations

The work described in this report is concerned entirely with the Source Noise Modeling

portion of the ANOPP program. In keepir_g with the promise of ANOPP to contain the

best methods available, an industry-established reputation for over-prediction, and the

need to refine ANOPP for the completion of advanced UHB studies, GE was provided

with the task of evaluating the engine source noise models in ANOPP. The evaluation of

ANOPP was made by comparing fan, jet, combustor, and turbine noise prediction model

results with GE data on a static, single engine basis.

The results of these comparisons identified that the Heidmann fan noise model

contained in ANOPP was contributing significantly to the trend of noise over-prediction,

and under the existing contract, GE was given the task of resolving this problem. Rather

than replace the fan noise model in its entirety, it was recommended by NASA that the

basic Heidmann model be retained, but modified to yield results that would more closely

predict the commercial turbofan noise.

Each part of the Heidmann fan noise prediction model was carefully evaluated relative

to three GE databases -- CF6-80C2, E 3, and QCSEE. A CFM engine database was also

used to expand the combination tone database in order to evaluate that part of the model

Volume ,1 of this report presents the results of the ANOPP fan, jet, combustor, and

turbine noise module assessment. Also included are specific recommendations for

changes to the Heidmann fan noise model (Heidmann, 1979) that were determined to

yield results in closer agreement with these databases.

Volume 2 of this report (to be published at a later date) will describe the results of

ongoing work relative to the correlation of fan inlet and fan exhaust noise suppressionwith various treatment design parameters. This follow-on work is an enhancement to the

Heidmann method, which currently predicts noise for only hardwaU engine nacelles.

3.0 Results and Discussion -- ANOPP Evaluation

An assessment of ANOPP was carried out to evaluate the ability of ANOPP to predict

engine component noise of high bypass ratio engines. Predictions were made for

representative engines for which detailed noise measurements were available. These

engines were the CF6-80C2 (Biebel, J., and Hoerst, D., "Acoustic Data Report for CF6-

80C2", GE TM #87-80, 1987, private communication), The Energy Efficient Engine (E 3)

(Lavin et al., 1978), and the Quiet Clean Short-Haul Experimental Engine (QCSEE)

(Stimpert, 1979). Cross-sections of each engine are shown in Figures 3.0.1, 3.0.2, and

3.0.3. A summary of general cycle and geometry information for these three engines isgiven in Table 3.0.1.

Figure 3.0.1 CF6-80C2 Engine

Figure 3.0.2 E 3 Engine

Figure 3.0.3 QCSEE UTW (Under The Wing) Engine

0.711

Table 3.0.1

FN

BPR

tip speed

Core jet velocity

Exhaust type

PR

Fan Treatment

Engine Summary -Typical Takeoff Condition

CF___66 E 3 QCSEE

57 32 19 K lbs

5.0 7.7 12.1

1434 1123 956 ft/s

1577 889 868 ft/s

separate mixed separate

1.8 1.4 1.3

hardwail hardwall hardwall

4

In order to assess the ANOPP source noise models, the following component noise

predictions were made:

Component ANOPP Modulefan HDNFAN

jet - STNJETcombustor - GECOR

turbine - GETUR

Predictions were made for each of three engines: the CF6-80C2, E 3, and QCSEE.

All predictions were made for a static, single engine on a 150 ft arc, and were made on

the VAX system using ANOPP version 03/02/10. For each engine, typical takeoff,

cutback, and approach conditions were predicted. These conditions were selected to

facilitate comparison with the existing GE engine component noise database. A sample

ANOPP input listing (E 3 takeoff case) is given in Appendix A.

The GE in-house component noise databases are created by using engine geometry

and cycle information in order to split the measured static acoustic data into jet, fan inlet,

and turbomachinery exhaust components. Figure 3.0.4 shows a typical E 3 component

database generated for the takeoff condition. The combustor and turbine noise

predictions shown were made using GE in-house prediction methods.

Figure 3.0.4 Sample E' Component Noise

150 ft arc, one engine, Takeoff

140

130

120

•_ 110

9O

7O

Fan Inlet _ Tutbom(_hlne_/ _ JetE_aust

Turl_ne _ Total

----x---- Combult _

20 _lO 60 80 100 120 laO 160

Angle re Inlet, deg

For the E 3 and QCSEE engines, the GE database used was for a hardwall fan inlet and

fan exhaust. For the CF6-80C2, a treated fan inlet and fan exhaust database was used (a

hardwall fan exhaust database did not exist at the time this work was completed). In

order to compare the ANOPP predictions with the CF6-80C2 database, calculated

treatment suppressions were applied to the ANOPP fan inlet and fan exhaust componentresults.

3.1 Overall Results

Figures 3.1.1 -- 3.1.6 show summaries on a spectral basis of the ANOPP component

predictions for all three engines at the takeoff condition. For each engine, there are

separate plots for both the peak forward and peak aft angles. The heavy, solid line

represents the total measured engine noise, and the solid squares represent a static SPL

sum of all of the ANOPP components. These plots show how well ANOPP predicts total

engine noise, and indicate where particular ANOPP component predictions are yielding

noise levels greater than the total engine noise.

Figure 3.1.1 ANOPP Component Sunnnary, CF6-80C2, forward angle, takeoff,

150 ft arc, one engine

i

Fan Inlet (r_o CT)

Fan Exhou_

Jet

=J_ Combustor

Turblne

ANOPP Sum

m Data

i

I00 I000 IOOOO

113 Octave Center Frequency, Hz

Figure 3.1.2 ANOPP Component Summary, E', forward peak angle, takeoff,


lOS

TO0

95

90

485

80

75

70

65

60

10

Fort Inlet

Fan Exnou%'

----e,---- Jel

I_ ComDu$Tor

,._z-- Turbine

-----m----- ANOPP Sum

m Oota

. _ _...i. _ ,

lO0 IO0O 1oooo

I/3 Octave Center Frequency, Nz

Figure 3.1.3 ANOPP Component Summary, QCSEE, forward angle, takeoff,


I00

95

9O

85

75

70

65

60

10

Far= _lelr

Fort Exr_oust

Jel

ComDusTOr

Turbine

,&NO PP Sum

m £)oto

oo :ooo _oooo

1/3 Octave Center Frequency, Hz

Figure 3.1.4 ANOPP Component Summary, CF6-80C2, aft angle, takeoff,


Fan _tet (no CT,}

Fen EXhOUST

Jet

ComDusIor

TufDIne

ANOPP Sum

m OOTO

.... L

T0 100 _000 _0000

I/3 Octave Center Frequency, Hz

Figure 3.1.5 ANOPP Component Summary, E _, aft angle, takeoff, 150 ft arc, one

engine

9O

85

75

70

65

6O

05

FOrt nWr100

Fort EX_OUSt

95JeT

--_'--" ComDuSlOr

TufDtne

ANOPP Sum

IO0 1000 10000


Figure 3.1.6 ANOPP Component Summary, QCSEE, aft angle, takeoff, 150 ft arc,

one engine

g

100

95

90

85

80

75

7O

65

60

_0

fan In_eT

Fon Exhous_

Jet

C omDustor

_ TurDlne

AN 0 PP Sum

m Doto

Ioo 1000 1000D


The general results for each noise component are presented in the following

subsections. Because of the large amount of data, only selected charts are shown in this

section. For each component, a peak angle spectrum at the takeoff condition for each of

the three engines is shown. Additional charts are given in Appendices B-J.

3.2 Fan Inlet Noise

General Results

The data show that the fan inlet noise ANOPP results depend heavily on the fan tip

relative Mach number (M_). At a subsonic value fM_ < 1), ANOPP shows a slight

underprediction relative to the GE component database (0.5 - 5 dB). At higher tip speeds

(such as for the CF6-80C2 engine at typical takeoff and cutback conditions), the ANOPP

results show a significant overprediction (11 - 19 dB). This overprediction is due largely

to the combination tone noise model in ANOPP. The amount of overprediction seems

related to the value of M_; the greater the value, the greater the degree of overprediction.

M_d values and the range of M_ values covered in the databases are as follows:

Table 3.2.1 Rotor Tip Relative

Engine M._

CF6-80C2 1.53

E 3 1.14

QCSEE 1.01

Inlet Mach Number

M r Range

0.65-- 1.53

0.64 -- 1.14

0.89-- 1.01

Results -- Takeoff

One-third octave spectra from the peak forward angle are shown in Figures 3.2.1,

3.2.2, and 3.2.3 for takeoff conditions of the CF6-80C2, E 3, and QCSEE engines,

respectively. A large overprediction by ANOPP is shown relative to the CF6-80C2

engine data (Figure 3.2.1). Since there was such a large difference, an inlet noise

prediction was made which excluded the contribution of the combination tone noise

portion of the fan noise model in ANOPP. Relative to the CF6-80C2 data, the ANOPP

method is shown to overpredict in this case as well. The ANOPP E 3 prediction (Figure

3.2.2) also shows that the fan inlet noise is overpredicted when the combination tone

noise model is included. If the combination to.ne noise calculation is excluded, the

engine noise is actually slightly underpredicted. An overprediction is shown relative to

the QCSEE engine data (Figure 3.2.3) -- but in this case the combination tone noise

model does not significantly contribute to the prediction due to the lower tip relative

Mach number. Detailed information regarding the combination tone noise model is

given in Section 4.6.

Note that the CF6-80C2 ANOPP prediction does not include the inflow distortion

noise effect, since the GE data was measured using a turbulence control screen (TCS).

The ANOPP E 3 and QCSEE predictions do include the inflow distortion effect, since thisdata was measured without a TCS.

Results -- Cutback, and Approach

The same trends are shown for each engine for the cutback and approach conditions as

were demonstrated at the takeoff condition. Spectra plots for all engine conditions and

at all angles of interest are given in Appendix B for CF6-80C2, Appendix C for E 3, and

Appendix D for QCSEE.

I0

Figure 3.2.1 Fan Inlet Noise Spectrum, CF6-80C2, takeoff, 40 deg, 150 ft arc

"_ ANOPP Fon Inlet

"-_ ANOPP w/Comb tones

"_'i'--- G E FIN (Fan 'nle0 /

-- - Totol Engine Data

_ =

,o _oo _ooo _oooo


Figure 3.2.2 Fan Inlet Noise Spectrum, E3, takeoff, 40 deg, 150 ft arc

...m

It0

I05

I00

95

90

85

80

75

70

10

_-A.ooo ooo.,ANOPP w/ COmb. tone_

GE FIN (Pan ]n_et)

-- - Tota_ Eng_e Data _ _

1oo _ooo _oooo

i/3 Octave Center Frequency, Hz

11

Figure 3.2.3 Fan Inlet Noise Spectrum, QCSEE, takeoff, 30 deg, 150 ft arc

1oo

95

90

85

80

75

70

65

60

I0

ANOPP FOt_ _n_lt

GE FiN (Fan inleT_

- Total Eng.4 DO_O

/\

f I

/J

i I i i i _ _ i ..... i i i i i i i , i

)00 1ooo 10o00


3.3 Fan Exhaust Noise

Results -- Takeoff, Cutback, and Approach

The fan exhaust noise ANOPP predictions vary with the type of engine as well as

condition. Peak aft angle spectra of takeoff fan exhaust noise are shown in Figures 3.3.1,

3.3.2, and 3.3.3 for the CF6-80C2, E 3, and QCSEE engines. The spectral content and

amplitudes for the CF6-80C2 and the E 3 ANOPP predictions (Figures 3.3.1 and 3.3.2)

show a slight overprediction relative to the GE component database, while the QCSEE

prediction is well below the measured engine data. Additional spectra plots at other

angles and for the other cycle conditions are given in Appendices E, F, and G for the

CF6-80C2, E 3, and QCSEE data respectively. The same trends demonstrated at takeoff

are shown in the cutback and approach conditions for the E 3 and QCSEE Engines. The

CF6-80C2 results vary from overprediction at takeoff to underprediction at approach.

12

Figure 3.3.1 Fan Exhaust Noise Spectrum, CF6-80C2, peak aft angle, 150 ft arc

to

_6dB

1

ANOPP Fan Exhaust

-- - Tofal Engl_e Data

i i t i t i i I

10o Ioo 0 1O0 O0


Figure 3.3.2 Fan Exhaust Noise Spectrum, E', peak aft angle, 150 ft arc

llO

lOS

O0

95

_ ,o85

80

75

70

10

ANOPP FOI_ EXhaust

GE FEX (_an £xhau_rl3

-- - TO_Ol Englne DO_O

i , , i , i i i l

J00 IOO0 _oo0o

!13 Octave Center Frequency, Hz

13

Figure 3.3.3 Fan Exhaust Noise Spectrum, QCSEE, peak aft angle, 150 ft arc

Ioo

95

90

85

_- 8o

75

70

65

60

_0

ANOPP Fort ExhOUSt

GE FEX (Fo. Ex_oust_

- TOIOI Engine OalO

IO0 1O0 0 10000


3.4 Jet Noise

Figures 3.4.1, 3.4.2, and 3.4.3 show the ANOPP predictions and GE jet noise

database spectra at takeoff conditions for the CF6-80C2, E 3, and QCSEE engines.

Additional jet noise spectra for the other engine conditions are shown in Appendix H.

The ANOPP-predicted amplitudes are generally above those of the GE database,

especially for predictions of the lower velocity jets. A clear trend of overprediction (1-6

dB) is indicated in the CF6-80C2 and the QCSEE predictions (Figure 3.4.1 and 3.4.3).

The peak frequency is quite different between data and prediction for the CF6-80C2 and

QCSEE engines. The ANOPP and GE jet noise component results are closer in

agreement in terms of peak noise (amplitude and frequency) for the mixed flow E 3

engine at takeoff (Figure 3.4.2) and cutback, but show a slight underprediction at

approach.

14

Figure 3.4.1 Jet Noise Spectrum, CF6-80C2, takeoff, 150 deg, 150 ft arc

10 I O0 1000 10000

113 Octave Center Frequency. Hz

Figure 3.4.2 Jet Noise Spectrum, E', takeoff, 150 deg, 150 ft arc

ItO

Io5

I co

95

90

85

80

75

70

lO

__ -,.. -,,, -../ \ _ ----

GE'LN J

I00 I000 I0000


15

Figure 3.4.3 Jet Noise Spectrum, QCSEE, takeoff, 150 deg, 150 ft arc

IO0

95

9o

85

80

7_

7o

65

6o

10

./'\, \

lO0 l_0 IO0 O0


3.5 Combustor Noise

ANOPP combustor noise predictions agree closely with the GE predictions (the two

prediction methods are identical, except that the cycle input parameters are slightly

different). The discrepancies observed in the QCSEE predictions are attributable to the

QCSEE cycle estimations that were made. Figures 3.5.1, 3.5.2, and 3.5.3 show the

combustor noise spectra at the peak noise angle for each of the three engines at takeoff

power. Spectra for the other engine conditions can be found in Appendix I.

Although the ANOPP and GE combustor noise predictions agree, it is difficult to

assess the absolute accuracy of the predicted levels and peak frequency. It can at least be

stated that the combustor noise predictions do not cause the total predicted engine noise

to assume an unreasonable spectral shape or to exceed the level of total measured engine

noise.

16

Figure 3.5.1 Combustor Noise Spectrum, CF6-80C2, takeoff, 120 deg, 150 ft arc

K

dBI

IDO 1000


10000

Figure 3.5.2 Combustor Noise Spectrum, E', takeoff, 120 deg, 150 ft arc

110

1o5

I00

95

6 _°85

8Q

75

70

ANOPP GECOR

-----m--=- GECombuslor

-- - 7o,oIEnglneOara ,/_ _ / _

i i i i .....

Io0 _ooo _oooo


17

Figure 3.5.3 Combustor Noise Spectrum, QCSEE, takeoff, 120 deg, 150 ft arc

_05

100

95

mqD

_ _°85

8O

75

7O

I _ANOPPGECO_

GEComDus_or

To,o,E,',o,n,,Da,o / \

. i i i i

1O0 1000 1 O0 O0

!/3 Octave Center Frequency, Hz

3.6 Turbine Noise

The ANOPP turbine noise predictions are on the order of 30 dB greater than the

corresponding GE predictions. Figures 3.6.1, 3.6.2, and 3.6.3 show the spectra for all

three engines at takeoff power. Additional peak noise spectra for the other engine

conditions are in Appendix J. All of these plots show an unusual turbine noise spectral

shape (no tones), and that the ANOPP component predictions are much greater than theturbine noise data.

There are several reasons for the differences observed. On the basis of previous

engine experience, GE turbine noise predictions assume that there is one dominant stage

(usually the last stage) of the low pressure turbine that significantly contributes to the

turbine noise component. Input parameters for the GE turbine noise prediction are

adjusted accordingly. If these adjustments are not made, the turbine noise component

prediction increases dramatically, nearly matching the ANOPP prediction in magnitude.Figure 3.6.4 demonstrates these results.

Although this "adjustment" seems to explain a significant portion of the large

differences observed, the discrepant spectral content of the ANOPP predictions still

requires explanation. (It should be noted that the ANOPP prediction method, despite the

name "GETUR", is in no way related to the GE turbine noise prediction method used.)

18

Figure 3.6.1 Turbine Noise Spectrum, CF6-80C2, takeoff, 120 deg, 150 ft arc

..t

$

IO0 1000 10000


Figure 3.6.2 Turbine Noise Spectrum, E', takeoff, 120 deg, 150 ft arc

_00

9G

70

6O

5O

_ ANOPP GEIUR '

-- - To,a_Eng_noDa,o ].._... ._/

Ico _ooo Igo co


19

Figure 3.6.3 Turbine Noise Spectrum, QCSEE, takeoff, 120 deg, 150 ft arc

t2D

105

95

85

65

5S

45

I0

ANOPP G ETUi_

----4t----- GETurD_o

-- - TOtOl EnQlne D

iiii ........................100 1000 1O0 O0


Figure 3.6.4 Turbine Noise Adjustment, CF6-80C2, Takeoff, 120 deg, 150 ft arc

"U

...Eettt_

10d8 _" _ --

-_o_ ANOPp G_=FUR

GETurt_no

i _ i .... . • i fl I i I , , i . . , , .... n

I0 100 1000 10000


2O

4.0 Results and Discussion -- Fan Noise Model Improvements

This section, which describes all of the recommended changes to the Heidmann fan

noise model, refers extensively to the Interim Prediction Method for Fan and Compressor

Source Noise (Heidmann, 1979). Complete understanding of the content of this section

requires familiarity with the Heidmann fan noise model.

A detailed description of the model would be impossible to give within the context of

this report. However, in order to help the reader who may be unfamiliar with the

method, a brief summary of the Heidmann model is attempted in the following

paragraph (excerpted from Heidmann, 1979).

The Heidmann procedure predicts one-third octave band levels of the free-field noise

pattern. The prediction method was initially developed by The Boeing Company, undercontract with NASA Ames Research Center. Heidmann made modifications to this

method, based on correlations and interpretations of the acoustic data from full-scale fan

tests performed at NASA Lewis (Heidmann, 1973). The noise predictions applicable to

one- and two-stage turbofans with or without inlet guide vanes (IGVs). The procedure

involves predicting spectrum shape, spectrum level, and free-field directivity for each of

the following components:

• fan inlet broadband noise

• fan inlet tone noise

• fan inlet combination-tone noise

• fan exhaust noise

• fan exhaust tone noise

Four parameters are required to predict the basic spectrum levels: mass flow rate (m),

total temperature rise across the fan stage (AT), and the design and operating point values

of the rotor tip relative inlet Mach number (M_, M_). The basic levels are then corrected

for presence of IGV, rotor-stator spacing (RSS), inlet flow distortions, and cutoff.

In order to compare with the Heidmann model, tone and broadband noise components

for the fan inlet and fan exhaust were separated for all three engine databases. Using the

Heidmann method normalization (fan temperature rise and mass flow), the GE data was

corrected and plotted relative to each appropriate Heidmann method correlation. Using

the CF6-80C2 data, the Heidmann method was adjusted to agree with the data, as

necessary. These adjustments were then further evaluated using the E 3 and QCSEE data.Since these databases did not contain much combination tone noise information, a typical

CFM56 noise database was also used to provide additional direction for the combination

tone noise model adjustments.

In the following sections, the specific results for each of the noise models are

described. The figures make reference in the title to the corresponding figure numbers in

the original Heidmann method documentation.

21

4.1 Fan Inlet Broadband Noise

Fan inlet broadband, fan exhaust broadband, fan inlet tone, and fan exhaust tone noise

components axe each described by the following equation (Heidmann, 1979)

201og(AT/ATo)+101og(m/mo)+Fl(M_, M_)+F2(RSS)+F3(0) (1)]

where:

is the peak characteristic sound pressure level of the noise component, AT/ATo is the

temperature rise across the fan stage normalized by a reference delta temperature, m/mo is

the mass flow through the fan relative to a reference mass flow, FI is a function of rotor

tip relative inlet roach numbers at the design and operating points, 1=2is a function of the

rotor to stator spacing, and F3 is a function of observer angle relative to the engine inlet.

Values for F_, F2, and 1=3vary for each noise component.

In the initial stages of the Heidmann method evaluation, comparisons of the GE data

with the Heidmann method predictions did not show consistent results for the different

engines. It was found that when the I=2 term (rotor-stator spacing effect) was eliminated,

more consistent results were predicted. Elimination of this term is in accord with prior GE

commercial engine experience, in which no effect of rotor-stator spacing on fan inletbroadband noise is observed.

Figure 4.1.1 shows the "Figure 4a" (Heidmann, 1979) fan inlet broadband noise curve

for the design tip relative Mach number (M,,a) of 1.53 for the CF6-80C2 engine. The CF6

inlet broadband data shown by the triangles indicate that a steeper slope on the Heidmann

prediction curve is required. This can be accomplished by using -50 log instead of -20 log

such that the new curve for normalized inlet broadband peak noise level, _, (F_ in

equation (1)) is given by:

1I_ = 58.5 + 20 log(M_)-50 log(Md0.9); Mt_ > 1, rat_> 0.9 (2) I

22

The solid line in Figure4.1.1representsthe originalHeidmanncurve, the dotted lineindicatesthechangedescribedin equation(2). Similarly,Figures4.1.2and4.1.3show theresultsfor theE3(Mt_d= 1.14)andQCSEE(Mt_= 1.01)enginedata,respectively. Thedatagenerallyshowcloseagreementwith thenewHeidmannmethodcurve.

One-thirdoctavespectrafor theinlet anglesaregiveninAppendixB for theCF6-80C2engine. Eachplot showsthe measuredenginenoise,the original Heidmannprediction,andthe new prediction(the new predictionreflects all of the changes that have not yet

been explained, but will be described later in this section). E 3 inlet spectra are shown in

Appendix C, and QCSEE inlet spectra are in Appendix D. These plots generally show

close agreement between the new broadband prediction and the measured data.

The directivity correction, F3 in equation (1), remains unchanged (see Section 4.5).

Figure 4.1.1 "Figure 4a", CF-80C2 Fan Inlet Broadband Noise

80.00

75,00t,.-

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23

Figure 4.1.2 "Figure 4a", E' Fan Inlet Broadband Noise

70.00

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n i t i i i i i i i i t i i i i t

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Figure 4.1.3 "Figure 4a", QCSEE Fan Inlet Broadband Noise

70.00

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24

4.2 Fan Exhaust Broadband Noise

Fan exhaust broadband noise is also described by equation (1), with different values for

F_, 1=2, and F3. Figure 4.2.1 shows the "Figure 4b" (Heidmann, 1979) fan exhaust

broadband noise curve for a design tip relative Mach number (M_) of 1.53 (CF6-80C2).

The CF6-80C2 exhaust broadband data shown by the triangles indicate that an increased

level as well as a steeper slope on the Heidmann prediction curve are required.

Accordingly, the base level of the "Figure 4b" curves for Mad > 1 is increased by 3 dB.

The slope of these curves is increased by using -30 log instead of -20 log. The new

equations for peak normalized broadband noise levels (F_ in equation (1)) are:

]_: 63 + 20 log(M_); M,_ > 1, Mt_<l.063 + 20 log(Mt_)-30 log(M_); Mt_d > 1,'Mt_> 1.0

(3a)

(3b)

80.00

Figure 4.2.1 "Figure 4b", CF6-80C2 Fan Exhaust Broadband Noise

Chart 4. "Figure 4b" - Fan Exhaust Broadband NoiseCF6-80C2, MTRD=1.53

75.00t-..J

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25

Figures 4.2.2 and 4.2.3 show the results for the E 3 (Mad = 1.14) and QCSEE (M_ =

1.01) engine data, respectively. The E 3 data do not agree well with the new Heidmann

curve. However, the E 3 is a mixed flow exhaust engine and the fan exhaust component

extracted from the measured engine noise is much lower in this case (not true for other

mixed flow exhaust databases) than for the separate flow engines at comparable speeds.

The QCSEE results generally agree with those of the CF6-80C2 in that an increase in theHeidmann curve level is desirable.

One-third octave spectra for the exhaust angles are given in Appendix E for the CF6-

80C2 engine. Each plot shows the measured engine noise, the original Heidmann

prediction, and the new prediction (The new prediction reflects all of the changes that

have not yet been explained, but will be described later in this section). E 3 inlet spectra are

shown in Appendix F, and QCSEE inlet spectra are in Appendix G. The E 3 charts show

that the new Heidmann noise method is overpredicting the fan exhaust noise, as expected.

The QCSEE charts generally show close agreement between the new broadband

prediction and the measured data.

Figure 4.2.2 "Figure 4b", E' Fan Exhaust Broadband Noise

80.00

75.00p,

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26

Figure 4.2.3 "Figure 4b", QCSEE Fan Exhaust Broadband Noise

80.00

75,00e---I

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N.

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MTR

F 2, the rotor-stator spacing (RSS) correction term, should always be calculated using

the equation labeled "no inlet distortion" in "Figure 6 -- Rotor Stator Spacing Correction

For Broadband Noise" ( Heidmann, 1979), given by:

Fz =-5 log(RSS/300) (4)1


4.3 Fan Inlet Discrete Tone Noise

Figure 4.3.1 shows the "Figure 10a" (Heidmann, 1979) fan inlet discrete tone noise

curve for a design tip relative Mach number (M_d) of 1.53 (CF6-80C2). The CF6 inlet

tone data shown by the triangles indicate that an increased level as well as "shift to the

right" of the Heidmann prediction curve are required. Accordingly, "Figure 10a" curves

were adjusted. The new equation for normalized peak fan inlet discrete tone noise, I__,

(F1 in equation (1)) is:

= 64.5 + 80 log(M:_Vl,); _ = 60.5 + 20 1og(M:d) +50 log(M_/0.72)for M:d > 1, M: > 0.72 (choose lesser value) (5)

27

Figure 4.3.1 "Figure 10a", CF6-80C2 Fan Inlet Tone

M_d = 1.53

80.00

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A Normalized -80C Data

&

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i i i i i i i50.00 ' ' ' ' '

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Figure 4.3.2 shows the E 3 engine results. This plot shows that the new curve will yield

a slight overprediction for the higher speed points that were previously underpredicted.

Figure 4.3.3, the QCSEE results, show very good agreement between the data and thenew Heidmann curve.

L

28

Figure 4.3.2 "Figure 10a", E 3 Fan Inlet Tone

M_d = 1.14

75.(30

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Figure 4.3.3 "Figure 10a", QCSEE Fan Inlet Tone

M_ = 1.01

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10

29

The cutoff factor, 5, for the fundamental tone is given by:

1C5= I Mt/(1-V/B)I (6) [

where Nit is the blade tip Mach number, V is the number of stator vanes, and B is the

number of rotor blades. If the cutoff factor is less than or equal to the critical value of

1.05, then the fundamental tone level is reduced by 8 dB ("Figure 8a", Heidmann, 1979).

Based on the GE databases, it is recommended that the amount of tone reduction, L, due

to cutoff become a function of the rotor tip relative Mach number, as shown by equation

sets 7 and 8. The correction at cutoff remains 8 dB, but the harmonic fall-off rates are

increased from 3 dB as follows:

For M_ < 1.15: For M_ > 1.15:

L = 6 - 6k; _5> 1.05 (7a) L = 9 - 9k; 5 > 1.05 (8a)

L = -8; k = 1 (7b) L = -8; k = 1 (8b)

L = 6 - 6k; k > 2 (7c) L = 9 - 9k; k > 2 (8c)

Refer to the data in Appendices B-D for the spectra plots for each of the three engines.

The "modified Heidmann method curves" generally show better agreement at the BPF

harmonics (reduced/eliminated over-prediction) relative to the measured engine data.

No changes are recommended to "Figure 8b", the cutoff correction curve for fans with

inlet guide vanes, since this effect could not be evaluated with the given commercial

engines that do not have inlet guide vanes.

It should be noted that the BPF cutoff factor is being incorrectly calculated in ANOPP

due to an error in the computer code. The vane/blade ratio is defined in the code as an

integer value, but must be defined as a real number to yield the proper value of 8 thatdetermines cutoff.

The F2 term (rotor-stator spacing effect), in accord with prior GE commercial engine

experience in which no effect of rotor-stator spacing on fan inlet tone noise is observed,

should be set equal to zero. The directivity correction, F3 in equation (1), remains

unchanged (see Section 4.5).

30

During ground static test, inflow disturbances drawn into the engine and interact withthe fan to cause rotor-turbulence interaction noise. A Turbulence Control Structure

(TCS) is a test apparatus that is used to clean-up the airflow disturbances in static engine

tests. The Heidmann model was developed from data that was taken without the benefit

of such a structure. GE initially developed a set of 'Ylight cleanup" values based on the

CF6-50/A300 aircraft flight test and engine static test data (Ho, Patrick Y., GE Design

Practice # 1935, 1987, private communication). Table 4.3.1 shows the suppressions that

should be applied to the Heidmann fan inlet tone predictions at the fundamental (BPF) and

second harmonic (2BPF) frequencies to remove the effects of inflow disturbances in the

model.

Table 4.3.1 GE "Flight Cleanu

Angle102O3O405O6O70809O

100110120130140150160

£' -- TCS Suppression

ApproachBPF5.6 5.45.8 4.34.7 3.44.6 4.14.9 2.05.1 2.92.9 1.63.2 1.31.6 1.51.6 1.11.8 1.42.1 1.52.4 1.02.2 1.82.0 1.62.8 1.6

Takeoff2BPF BPF 2BPF

4.85.55.55.35.35.14.43.92.62.31.82.11.71.72.63.5

5.83.85.36.43.53.02.12.11.11.40.90.70.70.40.60.8

31

4.4 Fan Exhaust Discrete Tone Noise

Figures 4.4.1, 4.4.2, and 4.4.3 show the "Figure 10b" (Heidmann, 1979) normalized

fan exhaust noise levels representative of the CF6-80C2, E 3, and QCSEE engines,

respectively. The CF6-80C2 data show fairly good agreement with the Heidmann curve.

The E 3 and QCSEE data do not show any trends that resemble the Heidmann fan exhaust

tone curve, nor do they suggest any alternative correlation. For these reasons, it is

recommended that the original curve be retained.

Figure 4.4.1 "Figure 10b" CF6-80C2 Fan Exhaust Tone

80.00

75.00

,,-I

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70.00

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=0

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Or_

ON

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A Normalized -80C Data

50.00 t * = i t = i i i = t i i i ,

0.1 1 10

MTR

F2, the rotor-stator spacing (RSS) correction term, should always be calculated using

the equation labeled "no inlet distortion" in "Figure 12 -- Rotor Stator Spacing

Correction For Discrete Tone Noise" ( Heidmann, 1979), given by:

[ F; = - l 0 log(RSS/300) (9)1


32

Figure 4.4.2 "Figure 10b" E _ Fan Exhaust Tone

80.00

75.00C

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,__ 70.00

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i i i i i I i i i i i i

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Figure 4.4.3 "Figure 10b" QCSEE Fan Exhaust Tone

80.00

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i i i = i i i i i i J i

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33

4.5 Directivity

The directivity correction "L", (F3 in equation 1) for fan inlet broadband, fan inlet tone,

fan exhaust broadband, and fan exhaust tone noise fit the GE measured data reasonably

well. The data were normalized by subtracting the peak one-third octave level from all

angles. Peak angles therefore have a directivity correction equal to zero, and off-peak

angles have correction values less than zero. The Heidmann directivity curves for each of

the four noise components are shown in comparison to the normalized E 3 data in Figures

4.5.1 - 4.5.4. Directivity comparisons relative to the CF6-80C2 and QCSEE engines are

given in Appendix K. Since the data generally show a close relationship to the directivity

curves in the Heidmann model, no changes are recommended.

Figure 4.5.1 "Figure 7a" Fan Inlet Broadband Directivity Correction -- E a Data

2

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34

Figure 4.5.2 "Figure 13a: Fan Inlet Tone Directivity Correction -- E 3 Data

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0

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140 150 160 170

35

Figure 4.5.4 "Figure 13b" Fan Exhaust Tone Directivity Correcdon -- E 3 Data

2

0

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36

4.6 Combination Tone Noise

The Heidmann method contains a model for predicting combination tone noise, a noise

source that occurs only at supersonic tip speeds. It is also commonly referred to as "buzz-

saw" noise or Multiple Pure Tone (MPT) noise. "At supersonic tip speeds, shock waves

are formed at the leading edge of each rotor blade. These shocks move upstream and

decay into a system of Mach waves which propagate out of the inlet duct. Ideally, these

shocks would contribute to the BPF tone, but small blade-to-blade manufacturing

variations result in a redistribution of the energy into various harmonics of the shaft

rotational speed" (Heidmann, 1979).

The characteristic peak level at center frequencies one-half, one-fourth, and one-eighth

of the fundamental blade passage frequency fb is given by

I_ = 20 log(AT/ATo)+10 log(m/mo)+Fl(Mt_)+ F_(0) + C (10) I

(C = -5 dB for fans with inlet guide vanes, C = 0 for fans without IGV)

FI is characterized by three separate spectra, which have peaks at one-half, one-fourth,

and one-eighth of the fundamental blade passage frequency of the fan stage, respectively.

These curves appear in Figure 4.6.1. ("Figure 14", Heidmann, 1979).

Figure 4.6.1. "Figure 14." Combination Tone Noise Spectrum Content

2f_0- L- 30 k_ '_. -30 k_ _n b

-I1 hi) Peek Iwelat f/lb'- 1/2. :

w abl Plat levelIt f/lb" 1/4.

L

-10

-3o I I.02 .05 .1 .2 .5 _ 1 Z $

Oimen.sionlessfrequency, f/lb

(r,.JPeBklevelat f/fb" 1/8.

37

The changes recommended for the combination tone model are largely based on GE

CFM56 data comparisons. Use of this data was required since the CF6-80C2 data contain

relatively little combination tone noise. There is no discernible MPT noise in either the E 3

or QCSEE databases.

Figures 4.6.2, 4.6.3, and 4.6.4 show how well the spectral content of the combination

tone noise is predicted by the modified Heidmann method, relative to the CFM56 data at

various tip speeds. These charts indicate that the spectral distribution shapes with peaks at

one-half, one-fourth, and one-eighth of the blade passage frequency (f/fb = 1/2, 1/4, and

1/8) are not characteristic of the combination tone noise. In fact, there are no clear trends

shown for the spectral distribution, and therefore no changes can be recommended.

Figure 4.6.2 Combination Tone Noise Spectrum, CFM56 engine, Mr = 1.2

10

m"o

t-O

o

E

oI

O_

-5

-10

-15

-2O

--_-- Data-.e- Heidmann 1/2 BPF1

--6- Heidmann 1/4 BPFI

--e- Heidmann 1/8 BPF]

-30

O.O1 0.1 1 10

Dimensionless Frequency, f/fib

38

Figure 4.6.3 Combination Tone Noise Spectrum, CFM56 engine, M= = 1.32

10

en"u

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-15U0D.¢,o

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•-*- Data

•-*- Heidmann 1/4 BPF

•4- Heidmann 1/8 BPF

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Dimensionless Frequency, fifo

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I0

Figure 4.6.4 Combination Tone Noise Spectrum, CFM56 engine, M= = 1.43

m-u

.J

t-O

gt.

Et.

OOD.

(D

-5

-10

-15

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• --0-- "

-30 f

0.01 0.1 1 10

Dimensionless Frequency, fffb

39

The levels of the three spectraaredeterminedby a set of curves that are labeled"Heidmann"in Figures4.6.5- 4.6.7(takenfrom "Figure 15",Heidmann, 1979). Figure4.6.5showsthenewcombinationtonenoiselevelcurvethatis recommendedfor f/fb= 1/2(shown by the dashed line), based on the comparison made with the CFM56 and CF6-80C2 data. Similarly, Figures 4.6.6 and 4.6.7 show the recommended shapes for the f/fb =

1/4 and 1/8 curves. In the case of the 1/2 and 1/4 BPF curves, the modification was

determined by a best fit with the CFM56 data (the CF6-80C2 data was ignored since the

MPT content is relatively low in this engine). For the 1/8 BPF peak curve, the CFM56

and CF6-80C2 data agree, but there is not enough data to support definition of a new

curve. In this case, the slope of the ascending curve was modified according to the data,

and the slope of the descending curve was maintained.

Spectral comparisons of the old and new Heidmann method predictions relative to the

GE data are given in Appendix L for the CFM56 and Appendix M for the CF6-80C2.

Exact definition of the new normalized combination tone levels (Fx) is given in Table

4.6.1.

Figure 4.6.5 "Figure 15" Combination Tone Noise, f]fb -- 1/2

80

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20

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\

Heidmann

• CF'M56

,', CF6-80C2

- - - rnodilied He dmann

RMTR10

4O

Figure 4.6.6 "Figure 15" Combination Tone Noise, f/fb = 1/4

8O

7O

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Figure 4.6.7 "Figure 15" Combination Tone Noise, f/fb = 1/8

80 .........................................................................................................................................................................................

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41

Table 4.6.1

f/fb1/2

Combination Tone Noise Levels

MTR Ln1_ 3o

1.14 ! 72.521 4.4

1/4 li 3o1.25 68.6

2 10.51/8 1

1.612

3660.656.5

4.7 Summary of Fan Noise Methodology Changes

The following section is an outline of all recommended changes to the Heidmann fan

noise model, based on the results of correlations made with the CF6-80C2, E 3, and

QCSEE engine data.

Inlet Broadband Noise

Inlet broadband noise is given by Heidmann as:

L¢ = 20 log(AT/ATo)+10 log(m/mo)+Fl(M_, M_)+Fz(RSS)+F3(0)

Modify Fx such that:

F] = 58.5 + 20 log(Mt_)-501og(Md0.9); Mt_ > 1, Mr > 0.9

Modify F2 such that:

• F2=0

Fan Exhaust Broadband Noise

Fan exhaust broadband noise is given by Heidmann as:

I_ = 20 log(AT/ATo)+ 10 log(m/mo)+F1 (M_d, M_)+F2(RSS)+F3(0)

Modify FI such that:

L_ = 63 + 20 log(M_); Mt,d > 1, M__<I .0

= 63 + 20 log(Mr,d)-30 log(M_); M_d > 1, Ms > 1.0

Always calculate F2 by:

F2 = -5 log(RSS/300)

42

Inlet Tone Noise

Fan inlet tone noise is given by Heidmann as:

L = 20 log(AT/ATo)+I 0 log(m/mo)+Fl(Mt_d, M_)+F2(RSS)+F3(0)


L_ = 64.5 + 80 log(Mt_/Mt_); _ = 60.5 + 20 log (Mt_) +50 log(MJ0.72)

for Mad > 1, M_ > 0.72 (choose lesser value)


F2=0

Cutoff Correction

Increase the harmonic fall-off rate for cutoff correction and make it a function of M_ as

follows:

For M_ < 1.15:

L=6- 6k;5> 1.05

L=-8;k= 1

L=6-6k;k>2

For M_ > 1.15:

L = 9 - 9k; 5 > 1.05

L= -8;k= 1

L=9-9k;k>2

Flight Cleanup

Apply following suppressions to fan inlet

(2BPF) tones for "flight cleanup" effect:

fundamental (BPF) and second harmonic

Angle1020304O5O6O708090100110120130140150160

ApproachBPF5.65.84.74.64.95.12.9

2BPF5.44.33.44.12.02.91.6

TakeoffBPF4.85.55.55.35.35.14.4

2BPF5.83.85.36.43.53.02.1

3.21.61.61.82.12.42.22.02.8

1.31.51.11.41.51.01.81.61.6

3.92.62.31.82.11.71.72.63.5

2.11.11.40.90.70.70.40.60.8

43

Fan Exhaust Tone Noise

Always calculate F2 by:

F2 = - 10 log(RSS/300)

Combination Tone Noise

Fan combination tone noise is given by Heidmann as:

I.,¢ = 20 log(AT/ATo)+10 log(m/mo)+F_(M_)+ F2(0) + C

Revise normalized combination tone noise levels (F_) as follows:

f/fb MTR Ln1/2

1/4

1/8

11.14

21

1.2521

1.612

3072.5

4.43O

68.610.5

3660.656.5

44

5.0 Concluding Remarks

The fan noise model in ANOPP is based on noise correlations developed from fan rigtests at NASA Lewis. The recommendations that have been made relative to commercial

engine data have now helped the method to achieve results that are a better indication of

full-scale fan noise from large commercial turbofan engines. No assessments related to

multiple stage fans or fans with inlet guide vanes were made, since this is outside of the

task of developing ANOPP as a tool for advanced UHB studies.

The recommendations intentionally are structured to retain the form of the Heidmann

model. Generally, no need to change the structure of the models was demonstrated, since

many of the original correlations showed some relationship to the engine data. An

exception to this was the combination tone noise model. In this case, it was demonstrated

that the structure of the model did not reflect the nature of the data, both in magnitude and

in frequency. The engine combination tone noise data does not fit the one-half, one-

fourth, and one-eighth blade passage frequency spectrum model. It is therefore suggested

that the current Heidmann method for combination tone noise prediction be replaced with

a new methodology.

The assessment of the other components of engine noise (jet, combustor, and turbine)

identified some other areas for potential model improvements, especially to the turbine

noise method. This model was shown to give tremendously high predictions of turbine

noise, and a spectral content that wasmuch different from that of the engine data.

Follow-on work to this task is in progress to add fan inlet and fan exhaust noise models

of acoustic treatment suppression. This will be an enhancement to the current Heidmann

model, which predicts only hardwall fan noise. Such a tool will enable comparisons of

engine configurations with different treatment designs.

45

Appendix A

Sample ANOPP Input

46

ANOPP JECHO=.TRUE. JLOG=.FALSE. NLPPM=60 $

STARTCS $

SETSYS JECHO=.FALSE. JCON=.TRUE. $

CREATE SCRATCH ATMHDNFAN STNJET GECOR GETUR SFIELD $

CREATE FANIN FANEX $

$$ DEFINE FREQUENCY AND DIRECTIVITY ANGLE ARRAYS

$UPDATE NEWU=SFIELD SOURCE=* $

-ADDR OLDM=* NEWM=FREQ FORMAT=5H24RS$ $

50. 63. 80. i00. 125. 160. 200. 250. 315. 400. 500. 630. 800. i000

1250. 1600. 2000. 2500. 3150. 4000. 5000. 6300. 8000. 10000. $

-ADDR OLDM=* NEWM=THETA FORMAT=5HI7RS$ $

I0. 20. 30. 40. 50. 60. 70. 80. 90. i00. ii0. 120. 130. 140.

150. 160. 170. $

-ADDR OLDM=* NEWM=PHI

90. $END* $

$PARAM IUNITS=7HENGLISH $

PARAM RS = 150.

PARAM IOUT=I

PARAM AE=33.2

PARAMNENG=I

PARAM IPRINT=2

$$ LOAD SYSTEM PROCEDURE LIBRARY

$LOAD /LIBRARY/STNTBL $

LOAD /LIBRARY/ LIB=PROCLIB $

$$

FORMAT=3HRS$ $

$ RADIAL DISTANCE FROM SOURCE TO OBSERVER, M

$ REQUEST dB OUTPUT

$ ENGINE REFERNCE AREA, ft**2

$ NUMBER OF ENGINES

$ INPUT PRINT ONLY

RELATIVE HUMIDITY

$ BUILD ATMOSPHERIC AND ATMOSPHERIC ABSORPTION TABLES

$PARAM DELH=I00. $ ALTITUDE INCREMENT FOR OUTPUT, M

PARAMHI=0. $ GROUND LEVELALTITUDE

PARAM NAI=I $

PARAM NHO=II $ NUMBER OF ALTITUDES FOR OUTPUT

PARAM Pi=1936.08 $ ATMOSPHERIC PRESSURE AT GROUND LEVEL, LB/FT^2

PARAM ABSINT=I0 $ # OF INTEGRATION STEPS FOR ABS

$$ DEFINE MEMBER ATM(IN)- ALTITUDE. TEMPERATURE.

$UPDATE NEWU=ATM SOURCE=* LIST=ES $

-ADDR OLDM=* NEWM=IN FORMAT=4H3RS$ $

0. 536.67 70. $

END* $

$$EXECUTE ATM $

$EXECUTE ABS $

$$ SET UP INPUT FOR GEO

$PARAM DELT=0.5

PARAM ENGAM= 3 HXXX

PARAM START=0.0

PARAM STOP=40.

PARAM ICOORD= 1

$ RECEPTION TIME INCREMENT

$ MATCH DEFAULT NAMES IN OTHER MODULES

$ START TIME FOR GEOMETRY

$ STOP TIME FOR GEOMETRY

$ REQUEST BODY AXIS ONLY

$PAR//_DELTH=I0.

PARAMCTK=I.

PARAMDELDB=I0.

$$

PARAM DIRECT=.FALSE. $ INTERPOLATE FROM FLI(TAKOFF) OBSERVER RECEPTION

TIMES AND GEOMETRY BASED ON USER PARAMS

$ MAXIMUM POLAR DIRECTIVITY ANGLE

$ CHARACTERISTIC TIME CONSTANT

$ LIMITING NOISE LEVEL DOWN FROM PEAK

$ PUT OBSERVER AT LOCATION 0,0,0

$UPDATE NEWU=OBSERV SOURCE=* $

-ADDR OLDM=* NEWM=COORD FORMAT=4H3RS$ $

o. o. o. $END* $

$$PARAM RHOA=.00222 $

PARAMMA=0.00 $$$$ DEFINE ENGINE CYCLE PARAMETERS FOR FAN NOISE

$PARAM CA= 1135.6

PARAM DIAM=I.2

PARAMMDOT=.443

PARAM N=0.320

PARAMDELTAT=0.123

PARAMNB=32

PARAM MD=0.989

PARAMAFAN=I.0

PARAM RSS=2.600

PARAMNV=34

PARAM IGV=I

PARAMDIS=2

PARAM INRS=.TRUE.

PARAM INCT=.FALSE.

PARAM INDIS=.TRUE.

PARAM IDRS=.FALSE.

PARAM IDBB=.FALSE.

PARAM INBB=.TRUE.

$

$ AMBIENT SPEED OF SOUND

$ FAN ROTOR DIAMETER, RE AE

$ MASS FLOW RATE, RE RHOA*CA*AE

$ ROTATIONAL SPEED, RE CA/DIAM

$ TOTAL TEMPERATURE RISE ACROSS FAN, RE TA

$ NUMBER OF BLADES

$ FAN ROTOR REL. TIP MACH NO. AT DESIGN POINT

$ FAN INLET X-SECT AREA, RE AE

$ ROTOR-STATOR SPACING, RE MEAN BLADE CHORD

$ NUMBER OF VANES

$ NO INLET GUIDE VANES

$ INLET FLOW DISTORTION

$ ROTOR STATOR INTERACTION TONES ON

$ COMBINATION TONES ON

$ INLET DISTORTION TONES OFF

$ DISCHARGE ROTOR-STATOR TONES ON

$ DISCHARGE BROADBAND ON

$ INLET BROADBAND ON

EXECUTE HDNFAN HDNFAN=FANIN $

$PARAM IDBB=.TRUE. IDRS=.TRUE. INBB=.FALSE. INCT=.FALSE. INRS=.FALSE. $

PARAM INDIS=. FALSE. $

$EXECUTE HDNFAN HDNFAN=FANEX $

$$$ DEFINE INPUT PARAMETERS FOR JET NOISE MODULE

$PARAM CIRCLE=. TRUE.

PARAM PLUG=. TRUE.

PARAM SUPER= .FALSE .

PARAM DELTA=0.

PARAM MI=. 707

PARAM VI=0. 783

PAR.AM TI=I. 341

PARAM MA=0.0

PARAM RHOI=. 819

PARAM DE1=. 912

$ IMPLIES CIRCULAR NOZZLE

$ EXHAUST PLUG OPTION ON

$ SUPERSONIC JET OPTION OFF

$ ANGLE BETWEEN FLIGHT VECTOR AND ENGINE AXIS

$ PRIMARY STREAM MACH NO

$ " " JET VELOCITY,RE CA

$ " " TOTAL TEMP, RE TA

$ AIRCRAFT MACH NO.

$ PRIMARY STREAM JET DENSITY, RE RHOA

$ ACTUAL PRIMARY STREAM EQUIVALENT DIAMETER

PARAMDHI=DEI $ PRIMARY STREAM HYDRAULIC DIAMETER

PARAMAI=.653 $ PRIMARY STREAM FULLY EXPANDED JET AREA

$EXECUTE STNJET $

$$$ DEFINE PARAMETERS FOR COMBUSTION NOISE MODULE

$PARAM MDOT=.037

PARAM PI=25.09

PARAM TI=2.709

PARAM TCJ=5.707

PARAM TDDELT=2.8

PARAM A=.01

$EXECUTE GECOR $

$$$ DEFINE PARAMETERS FOR TURBINE NOISE MODULE

$PARAM AREA=.213 $ TURBINE INLET CROSS-SECTIONAL AREA, RE AE

PARAMNBLADE=48 $ # OF ROTOR BLADES

PARAM D= .351 $ TURBINE ROTOR DIAMETER, RE SQRT AE

PARAM ROTSPD=.32 $ ROTATIONAL SPEED, RE CA/D

PARAM TTI=3.786 $ ENTRANCE TOTAL TEMPERATURE, RE TA

PARAM TSJ=2.875 $ EXIT STATIC TEMPERATURE, RE TA

$EXECUTE GETUR $

$$PARAM PROPRT=2 $

$ENDCS $

$ COMBUSTOR ENTRANCE MASS FLOW RATE, RE RHOA*CA*AE

$ " " TOTAL PRESSURE, RE TA

$ " " " TEMPERATURE, RE TA

$ " EXIT TOTAL TEMPERATURE, RE TA

$ DESIGN TURBINE TEMPERATURE RISE, RE TA

$ COMBUSTOR ENTRANCE AREA, RE AE

Appendix B

Fan Inlet Noise Spectral Comparisons- CF6-80C2

Page

51

52

53

54

Appendix B Contents

Fan Speed, rpm Angles, deg

3150 (takeoff)

3150 (takeoff)

2850 (cutback)

2850 (cutback)

2700

20-50

60-80

20-50

60-80

20-5055

56 2700 60-80

57 2550 20-50

58 2550 60-80

59 2250 20-50

60 2250 60-80

2100(appmach)

2100(approach)

61

62

20-50

60-80

squares

circles

triangles

Key to Plots:

= total measured engine data

= Heidmann method prediction

= modified Heidmann method prediction (see Section 4)

50

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Appendix C

Fan Inlet Noise Spectral Comparisons - E 3

Page

64

65

66

67

68

69

Appendix C Contents


3100 (takeoff)

3100 (takeoff)

2800 (cutback)

2800 (cutback)

1820 (approach)

1820 (approach)

20-50

60-70

20-50

60-70

20-50

60-70

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circles

triangles

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63

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Appendix DFan Inlet Noise Spectral Comparisons - QCSEE

Page

71

72

73

74

75

76

Appendix D Contents


3086 (takeoff)

3086 (takeoff)

2931 (cutback)

2931 (cutback)

2759(approach)

2759 (approach)

20-50

60-70

20-50

60-70

20-50

60-70

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.,42

Appendix EFan Exhaust Noise Spectral Comparisons - CF6-80C2

Page

78

79

Appendix E Contents


3534

3534

80 3000

81 3000

82 2400

83 2400

84 3450

90-120

130-160

90-120

130-160

90-120

130-160

90-120

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86 3300 90-120

87 3300 130-160

88 3150 90-120

89 3150 130-160

90 2850 90-120

91 2850 130-160

92 2700 90-120

93 2700 130-160

94 2100 90-120

95 2100 130-160

96 1950 90-120

97 1950 130-160

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101 1650 130-160

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Appendix F

Fan Exhaust Noise Spectral Comparisons - E _

Page

103

104

105

106

107

108

3100 (takeoff)3100 (takeoff)

2800 (cutback)

2800 (cutback)

1820(approach)

1820 (approach)

Appendix F Contents


110-140

150-160

110-140

150-160

110-140

150-160

squares

circles

triangles

Key to Plots:




102

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Appendix G

Fan Exhaust Noise Spectral Comparisons. QCSEE

Page

110

111

112

113

114

115

Appendix G Contents


3086 (takeoff)

3086 (takeoff)

2923 (cutback)

2923 (cutback)

2759 (approach)

2759 (approach)

110-140

150-160

110-140

150-160

110-140

150-160

squarescircles

triangles

Key to Plots:




109

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Appendix H

Jet Noise Spectral Comparison, 150 degrees

Page

117

117

118

118

119

119

Appendix H Contents

Engine Condition

CF6-80C2

CF6-80C2

E 3

E 3

QCSEE

QCSEE

cutback

approach

cutback

approachcutback

approach

dashed line

X

diamonds

Key to Plots:


= GE jet noise

= ANOPP jet noise (STNJET) prediction

116

5O 8O 1_ _3

_._g Le 4 _d04_I_94_ EGSREP_.CPOST 4 SJ 04_&g4 on c04241rNO _ V_R _IFIEDI

i

31S 500 800 t250 2000 31S0

1_ Oe CENTER FREQUENCY (Hz)

iso.o_.s_x ANOPPversusJTFXFNPREDICTIONCF6JET.160FTARC._CH CONDITK_

50 80 12_ 200

i355 500 800 1250 2_0 3150 5000 IIODO

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!

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i

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2000 3150 G000 alO00

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t 1in IO t_

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CR:SEE ,E'r, lS0 FI ARC, CVTBN_ CGNIXrI_

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acs_ Je-r. 1so FT _qc. _PRO_H CO_T_

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l_J OIB CENTER FREQ4.,'ENCY (HZ)

Appendix I

Combustor Noise Spectral Comparisons, 120 degrees

Page121

121

122

122

123

123

Appendix I Contents

Engine Condition

CF6-80C2

CF6-80C2

E 3

E 3

QCSEE

QCSEE

cutback

approach

cutback

approach

cutback

approach

dashed line

X or filled square

diamonds or open square

Key to Plots:

= total measured engine data= GE combustor noise

= ANOPP combustor noise (GECOR) prediction

120

t=ooOWs=--,_ ANOPPvBsus JTFXFN PREDICTIONcr4 COmUSTOR,1SOrr _c. CUTS_KCONOmON

o

L =

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a=

110

105

i00

95

90

85

80

75

70

IO

Task 24 ANOPP Assessment: Combustor NoiseQCSEE, Cutback, 150 ff arc, 120 deg

---o--- ANOPP GECOR

GECombustor

-- - -- Total Engine Data

,,-- -\ /\,

/ "\/ .I . / _ -_..!kl"

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100 1000 10000


M.i"o

110

105

100

95

90

85

80

75

70

Task 24 ANOPP Assessment: Combustor NoiseQCSEE, Approach, 150 ft arc, 120 deg

Io

ANOPP GECOR

GECombustor

-- " -- Total Engine Data.\

/., \

/ /\,

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I00 1000


\- ._ o_ °_ .

10000

Appendix J

Turbine Noise Spectral Comparisons, 120 degrees

Page

125

Appendix J Contents

Engine Condition

CF6-80C2

125 CF6-80C2

126

126

127

127

E 3

E 3

QCSEE

QCSEE

cutback

approach

cutback

approachcutback

approach

dashed line

filled squares

open squares

Key to Plots:

= total measured engine data= GE turbine noise

= ANOPP turbine noise (GETUR) prediction

124

Task 24 ANOPP Assessment: Turbine NoiseCF6-80C2, Cutback, 150 fl arc, 120 deg

,,JO,. ---.-a-.--- ANOPP GETU

! j /\

IO IOO 1ooo 100013


"O

.=__L

Task 24 ANOPP Assessment: Turbine NoiseCF6-80C2, Approach, 150 ff arc, 120 deg

I

iI I°d6

----o-- ANOPPGETUR -_ J / _ "

"_°--- TGcEtT_inn;n e t_ /\

I0 100 1000 100(30


110

Task 24 ANOPP Assessment: Turbine NoiseE3, Cutback, 150 ft arc, 120 deg

100

9O

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,__ 8O

cf_

7O

60

5O

10

/ \

----o--- ANOPP GETUR

GETurblne

-- - -- Total Englne Data

r i i i i i j

I00 lOOQ 101300


Task 24 ANOPP Assessment: Turbine NoiseE3, Approach, 150 fl arc, 120 deg

105

95 I _ ANOPP GE'I'UR . _ _.\-- gETurblne

Tota Engine Data /k., _ --- "_8 5 .... _ / ' , . _ .

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75 -_ ./"

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105

75

65

55

45

10

Task 24 ANOPP Assessment: Turbine NoiseQCSEE, Cutback, 150 ft arc, 120 deg

"_'\/\.,/'_ ./ '\ __ /'

... ./ i -- .-..i "/

+ ANO_P GETUR _A

r i i L L i i .m i i i , i , ,

100 10130 1000O

I/3Octave Center Frequency, Hz

Task 24 ANOPP Assessment: Turbine NoiseQCSEE, Approach, 150 fl arc, 120 deg

105 -

95 ! ./ \

r i I , i i r, r , , , ..... --45

lO 100 I000 I0000


Appendix K

Directivity, CF6-80C2 and QCSEE

Page

129

129

130

130

131

131

132

132

Appendix K Contents

Noise Component

Fan Inlet Broadband

Fan Inlet Broadband

Fan Inlet Tone

Fan Inlet Tone

Fan Exhaust Broadband

Fan Exhaust Broadband

Fan Exhaust Tone

Fan Exhaust Tone

EngineCF6-80C2

QCSEE

CF6-80C2

QCSEE

CF6-80C2

QCSEE

CF6-80C2

QCSEE

all symbolssolid line

Key to Plots:

= total measured engine data, all speeds= Heidmann method

128

Fan Inlet Broadband Directivity Correction, CF6-80C2

0

-2

rn"0

- -4.J

o -6e=

U.t-O -8

mo=,- -100(J

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u

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-16

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I 2100

& 225O

X 24OO

z 255O

• 2600

+ 2700

- 2850

3000

• 3110

--Heidmann

I i

0 10 20

.\: i- -,_ #,

=\

i I i i i i, i

30 40 50 60 70 80 90

Angle re Inlet, deg

loo

2 •

Fan Inlet Broadband Dlrectlvlty Correction, QCSEE

0

-2

m -4"o

-I,. .6o

(,I

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-14

-16

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• 2755

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Angle re Inlet, deg

i

9o 10o

129

0

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m -4"10

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o_ -8

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-14

-16

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9+

E

x

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10 20 30

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o X _ X 2400

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il = _. • 3110

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i I i i t i i

40 5O 60 70 80 90 100

Angle re Inlet, deg

Fan Inlet Tone Directivity Correction, QCSEE

m"0

J,- -6o

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6

• 2755 I

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i i

10 20

i i i l i i i ,

30 40 50 60 70 80 90 1 O0

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130

Fan Exhaust Broadband Directivity Correction, CF6-80C2

0

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m"O__ -4

o

o -6

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70 80 90 100 110 120 130 140 150 160 170

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Fan Exhaust Broadband Directivity Correction, QCSEE

-2

*in"0

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131

Fan Exhaust Tone Dlrectlvlty Correction, CF6-80C2

0

-2

m -4'ID

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o

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-18 mx

-20 i i s i i i _ i i i t

50 60 70 80 90 100 110 120 130 140 150 160 170

Angle re Inlet, deg

Fan Exhaust Tone Directlvity Correction, QCSEE

0

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Angle re Inlet, deg

170

132

Appendix L

Combination Tone Noise Spectra - CFM56

Page

134

Appendix L Contents

Fan Speed, rpm

3600

Angles50-80

135 3900 50-80

136 4050 50-80

137 4150 50-80

138 4250 50-80

139 4350 50-80

140 4450 50-80

141 4550 50-80

squares

circles

triangles

Key to Plots:

= total measured engine data= Heidmann method

= modified Heidmann method

133

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Appendix M

Combination Tone Noise Spectra- CF6-80C2

Page

143

Appendix M Contents

Fan Speed, rpm2700

Angles40-70

144 2850 40-70

145 3000 40-70

146 3110 40-70

squares

circles

triangles

Key to Plots:

= total measured engine data= Heidmann method

= modified Heidmann method

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6.0 References

Gillian, Ronnie: Aircraft Noise Prediction Program User's Manual, NASA TM 84486,

1982.

Heidmann, Marcus F., and Feiler, C. E.: Noise Comparisons From FuU-Scale Fan Tests

at NASA Lewis Research Center, AIAA 73-1017, October 1973.

Heidmann, Marcus F.: Interim Prediction Method for Fan and Compressor Source

Noise, NASA TM X-71763, 1979.

Lavin, S. P., and Ho, P.: NASA Energy Efficient Engine Acoustic Technology Report,

Contract NAS3-20643, GE Aircraft Engines, 1978.

Stimpert, Dale L.: Quiet Clean Short-Haul Experimental Engine (QCSEE) Under the

Wing (UTW) Composite Nacelle Test Report, Vol. II -- Acoustic Performance, NASA

CR-159472, 1979.

147

Form ApprovedREPORT DOCUMENTATION PAGE OMBNo.0704-0188

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time Jor reviewing instructions, searching existing data sources,gathering and mainlaining 1he data needed, and ¢orr_leting and rev_wing the collection of information, Send comments regarding this burden estimate or any other asDect of thiscollection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports. 1215 JeffersonDavis Highway. Suite 1204, Arlinglon. VA 22202.4302, and to the Office of Management and Budge1. Paperwork Reduction Project (0704.0188), Washington. DC 20503.

1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

August 1996 Final Contractor Report4. Vm.E ANDSUBTrrLE S. FUNDINGNUMBERS

Improved NASA-ANOPP Noise Prediction Computer Code for AdvancedSubsonic Propulsion Systems

6. AUTHOR(S)

Karen Kontos, Bangalore Janardan, and Philip Gliebe

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

GE Aircraft EnginesP.O. Box 156301

Cincinnati, Ohio 45215-6301

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135-3191

WU-538-08-11C-NAS 3-26617Task Order 24

8. PERFORMING ORGANIZATIONREPORT NUMBER

E-9710

10. SPONSORING/MONITORINGAGENCY REPORTNUMBER

NASA CR-195480

11. SUPPLEMENTARY NOTES

Project Manager, Jeffrey J. Berton, Aeropropulsion Analysis Office, organization code 2430, (216) 977-7031.

12a. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified -Unlimited

Subject Category 07

This publication is available from the NASA Center for Aerospace Information, (301) 621--0390.

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

Recent experience using ANOPP to predict turbofan engine flyover noise suggests that it over-predictsoverall EPNL by a significant mount. An improvement in this prediction method is desired for systemopfimizaton and assessment studies of advanced UHB engines. An assessment of the ANOPP fan inlet,fan exhaust, jet, combustor, and turbine noise prediction methods is made using static engine componentnoise data from the CF6-80C2, E3, and QCSEE turbofan engines. It is shown that the ANOPP predictionresults are generally higher than the measured GE data, and that the inlet noise prediction method(Heidmann method) is the most significant source of this overprediction. Fan noise spectral comparisonsshow that improvements to the fan tone, broadband, and combination tone noise models are required toyield results that more closely simulate the GE data. Suggested changes that yield improved fan noisepredictions but preserve the Heidmann model structure are identified and described. These changes arebased on the sets of engine data mentioned, as well as some CFM56 engine data that was used to expandthe combination tone noise database. It should be noted that the recommended changes are based on ananalysis of engines that are limited to single stage fans with design tip relative roach numbers greater thanone.

14. SUBJECTTERMS

ANOPP, Heidmann Method, Engine Noise Prediction

17. SECURITY CLASSIFICATION

OF REPORT

Unclassified

NSN 7540-01-280-5500


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15. NUMBER OF PAGES147

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