A Williams International FJ44-3A 3000-lb thrust class turbofan engine was used as a demonstrator for foam-metal liner installed in close proximity to the fan. Two foam metal liner designs were tested and compared to the hardwall. Traditional Single-Degree-of-Freedom liner designs were also evaluated to provide a comparison. Normalized information on farfield acoustics is presented in this paper. The results show that up to 5 dB PWL overall attenuation was achieved in the forward quadrant. In general, the foam-metal liners performed better when the fan tip speed was below sonic

Elliott, Dave

Hartley, Tom

Jones, Mike

Sutliff, Daniel

NASA Technical Reports Server

1A Williams International FJ44-3A 3000-lb thrust class turbofan engine was 
used as a demonstrator for foam-metal liner installed in close proximity to the 
fan. Two foam metal liner designs were tested and compared to the hardwall. 
Traditional Single-Degree-of-Freedom liner designs were also evaluated to 
provide a comparison. Normalized information on farfield acoustics is 
presented in this paper. The results show that up to 5 dB PWL overall 
attenuation was achieved in the forward quadrant. In general, the foam-metal 
liners performed better when the fan tip speed was below sonic.
Collaboration with Williams International to 
Demonstrate the Characteristics of a Foam-Metal-Liner 
Installed Over-the-Rotor of a Turbofan Engine
https://ntrs.nasa.gov/search.jsp?R=20090001341 2019-08-30T05:55:14+00:00Z
2Collaboration with Williams International to Demonstrate 
the Characteristics of a Foam-Metal-Liner Installed 
Over-the-Rotor of a Turbofan Engine.
Acoustics Technical Working Group Meeting
23-24 September-2008
Dan Sutliff (GRC)  Dave Elliott (GRC)  Mike Jones (LaRC)     
Tom Hartley (Williams International)
3Outline
Background
FJ44 / Liner
AAPL Facility / Test
Results
Discussion
4Rationale
•Traditional Liners are “tuned” - Single Degree of Freedom. 
( i.e. limited Band Width)
•Limited BW and/or unique design required.
•Not suitable for adverse environments (i.e. close to /over the rotor) 
‘distant’ from source.
•“Over the rotor” application requires rub & containment consideration.
• Ideally - would like to use a single component for improved attenuation, 
fan rub & containment.
Improve upon Traditional Liners Used in Turbofan 
Engines by Replacing with Foam Metal Liner 
5Historical Outline
• 2003 - 2004 RTX / LaRC preliminary studies of foam metal material and acoustic characteristics
• 2005 - 2006 ANCF tests of Foam Metal Liner in lab 
• April-2007: WI representatives attended Acoustics Technical Working Group meeting and 
expressed interest in applying foam metal liner to FJ44 engine.
• 23-May-2007: RTA/AAPL team visited WI and outlined collaboration with each parties supplying 
area of expertise; with less than $0-50K changing hands ($0)
–WI:
to provide engine & support (ideally:turnkey!!)
liner fabrication
engine integration
–NASA:
provide manpower and expertise for testing 
expertise and data systems for acoustic testing
material property investigation 
liner design guidance 
• IPP seed fund awarded July 2007
• Delineated though Simplified Space Act agreement signed October 2007
• Added Hawker Beechcraft Corporation and Dr. W. Eversman to collaboration effort on April 2008
6Metallic Foams
60 ppi, 6% Density
Advantages:
•Excellent acoustic absorption characteristics
•Ductile alloy with high temperature capability
•Sheet product identified as unusually high 
impact resistance 
•Processing technology developed with Porvair 
(including face sheet brazing and complex shapes)
Flammability test:  foam unaffected by 1000oC/30 min in 
a burner rig.  Long life in oxidizing environment to at 
least 800oC.
Immersion tests: foam specimens with a variety of size 
and shapes in various fluids such as water, skydroll, 
advanced hydraulic fluid and jet fuel (2 hr immersion + 2 
hr ambient drying).  Does not readily absorb fluids.
Stress Tests :  Mechanical properties surveyed, including 
compression, bending, tensile (w/face sheets).  Can 
withstand expected mechanical loads.
Rub Tests : Completed
7Impedance Tube Tests
Normal Impedance Tube Tests at LaRC
•Porosities (20 -100 ppi)
•Densities (4-8%)
•(2” x 2” x 0.425”) samples
•Two-microphone procedure
•Two-thickness procedure
0.0
0.2
0.4
0.6
0.8
1.0
0 500 1000 1500 2000 2500 3000 3500
Frequency, Hz
Abs.
Coeff
1" thickness
2" thickness
3" thickness
8Outline
Background
FJ44 / Liner
AAPL Facility / Test
Results
Discussion
9FJ-44 -3A Overview
10
Fan Case & Insert Design
THIS AREA TO HAVE 20% OPEN 
AREA WITH Ø.030” HOLES 
(1:1,L:D,WALL:HOLES)
314 Stainless Steel:
A1/A1t - 80 ppi / ~8%
A2 - 40 ppi / ~8%
Current 
HW1
FML
(HW2)
Rotor pathFlow
11
FML Close-up
12
Outline
Background
FJ44 / Liner
AAPL Facility / Test
Results
Discussion
13
Placement in AAPL
14
Schedule as Tested
CONFIGURATONS TESTED:
HW0 Hardwall configuration - original fan shroud (phased array)
HW1 Hardwall configuration - New inlet & baseline fan shroud
HW2 Hardwall configuration 
A1-80 Fan case only treated - 80 ppi foam
A1t-80 Fan case only treated - 80 ppi foam near the rotor only 
A2-40 Fan case only treated - 40 ppi foam
SDOF-71 Inlet only treated - C-71 - Hybrid thick/thin treatment zones
SDOF-72 Inlet only treated - C-72 - Thin core treatment (new/orig fan shroud)
DATA TAKEN:
Nearfield Acoustic 15-mic array @ 10’/10’
Farfield Acoustic 28-mic array @ ~60’ (not planar)
In-Duct Dynamic 9-high response transducer linear array in inlet 
Rotating Rake Modal 14-mic radial distribution in inlet
Flow Data Inlet: Pt rakes ; Ps wall taps
Bypass: Pt/Tt rake
new fan 
shroud
15
Outline
Background
FJ44 / Liner
AAPL Facility / Test
Results
Discussion
16
Near-Field Data Reduction
•Data acquired synchronously sampled 
to fan shaft @ 144/rev
•Frequency/time domain averaged
•Spectra for each microphone       
integrated over ‘harmonic bands’
i.e. 1/2 to 11/2 harmonics
or 8 to 24 shaft orders (etc)
multiplied by area, etc,  to obtain PWL
•Overall/Broadband/Tones
50
60
70
80
90
100
0 8 16 24 32 40 48 56
1xBPF
2xBPF 3xBPF
HARMONIC BANDS
Fan Tones
1st 2nd 3rd
50
60
70
80
90
100
0 8 16 24 32 40 48 56
Shaft Order (freq / (rpm/60) )
1st 2nd 3rd
HARMONIC BANDS
1 2 3 total
80
82
84
86
88
90
92
94
96
98
100
Harmonic Band
OA PWL (dB)
BB PWL (dB)
Tone PWL (dB)
17
Nearfield Directivity Plots
1st Harmonic Band / BPF 
18
Nearfield Results (10’ inlet arc)
 
50
60
70
80
90
100
0 8 16 24 32 40 48 56
Shaft Order (freq / (rpm/60) )
1st Harm Band
1xBPF
0
1
2
3
4
5
55% 60% 65% 70% 75% 80% 85% 90% 95% 100%
N1-corr
sonic rotor
tip speed
BROADBAND
-2
-1
0
1
2
3
4
5
6
7
8
55% 60% 65% 70% 75% 80% 85% 90% 95% 100%
N1-corr
A2 (40 ppi) A1   (80 ppi) A1t
sonic rotor
tip speed
OVERALL
-4
-2
0
2
4
6
8
10
55% 60% 65% 70% 75% 80% 85% 90% 95% 100%
N1-corr
sonic rotor
tip speed
19
Nearfield Results (10’ inlet arc)
 
50
60
70
80
90
100
0 8 16 24 32 40 48 56
Shaft Order (freq / (rpm/60) )
2nd Harm Band
2xBPF
0
1
2
3
4
5
55% 60% 65% 70% 75% 80% 85% 90% 95% 100%
N1-corr
sonic rotor
tip speed
BROADBAND
-2
-1
0
1
2
3
4
5
6
7
8
55% 60% 65% 70% 75% 80% 85% 90% 95% 100%
N1-corr
A2 (40 ppi) A1   (80 ppi) A1t
sonic rotor
tip speed
OVERALL
-4
-2
0
2
4
6
8
10
55% 60% 65% 70% 75% 80% 85% 90% 95% 100%
N1-corr
sonic rotor
tip speed
TONAL
20
Acoustic Summary (1)
9” SDOF liner in inlet:
SDOF1 - thick liner (except TT1 cut-out)
•fan BPF targeted at  100% N1c
SDOF1 - thin liner 
fan BPF targeted at 75% N1c
HW1
HW2
-3
-2
-1
0
1
2
3
4
5
6
7
55% 60% 65% 70% 75% 80% 85% 90% 95% 100%
N1-corr
sonic rotor
tip speed
 
HW2
HW1
A1
A2
SDOF1
SDOF2
sonic rotor
tip speed
5-dB
21
Performance (1)
Limited instrumentation:
4 Pt (5 ports) rakes in inlet w/ Ps at base
3 Pt / 3Tt rakes in bypass (behind stators)
Simple flow computations:
HW1
HW2
Pt/Tt-rakes Inlet Bypass
Row 10.322 9.450
R5 9.769 8.575
R4 8.649 8.200
R3 7.325 7.872
R2 5.701 7.450
R1 3.368 7.075
Riw 0.875 7.000
50% 55% 60% 65% 70% 75% 80% 85% 90% 95% 100%
m-dot corr
HW2
HW1
A1
A2
.01
Ý m = π 2
R
ro
2 − ri2( ) (PsTt )(
Pt
Ps
)(γ −1)/γ (Pt − Ps)
ηadiabatic = (Ptratioγ /(γ −1)) /(Ttratio −1)
22
Performance (2)
WI used acquired test parameters as input to engine simulation deck to estimate 
performance impact of the FML on select engine performance parameters.
(#’s relative to HW2 - effect of FML)
Δ
 
Fn 100% N1c 88% N1c 70% N1c
HW1 +3.0% +3.5% +5.6%
HW2 --- --- ---
A2 +0.6% +0.5% +0.7%
A1 -1.5% -2.2% -2.5%
Δ
 
SFC 100% Fn 88% Fn 70% Fn(?)
HW1 -0.4% -1.5% -4.6%
HW2 --- --- ---
A2 +0.0% -0.1% -0.1%
A1 +0.2% +0.6% +1.2%
Δ S.M. 100% N1c 88% N1c 70% N1c
HW1 +2.5% +3.9% +4.3%
HW2 --- --- ---
A2 +0.4% +0.5% +0.5%
A1 -0.9% -1.3% -1.7%
23
Outline
Background
FJ44 / Liner
AAPL Facility / Test
Results
Discussion
24
Conclusions
Foam Metal Liner was used successfully in an high-speed turbofan engine:
•Significant attenuation achieved from 2 acoustic designs
•Performance penalty at optimum acoustic design
•No performance penalty at off- optimum acoustic design
FML attenuates tones & broadband / not shocks(?).
Aero/Acoustic design was not integrated.


Collaboration with Williams International to Demonstrate the Characteristics of a Foam-Metal-Liner Installed Over-the-Rotor of a Turbofan Engine

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