Document
Fan Noise for a Concept
Commercial Supersonic
Transport
David Stephens
NASA Glenn Research Center
Acoustics Branch
This work funded by the NASA Commercial Supersonic Technology Project
Background
• A 2015 study by Lockheed Martin, GE and Stanford
described the LM 1044 vehicle
• 80 passenger, Mach 1.7 tri - jet, shaped boom
• Community noise: Jet noise and fan noise
NASA/CR — 2015 - 218719
Engine Inlet Aux Doors and Struts
• Additional inlet
mass flow needed
at low speeds
• Used during all
noise certification
points
• Aux doors and
NASA/CR — 2015 - 218719
struts introduce
distortion
• Aux doors become a
noise transmission
path
NASA P - Inlet Test (1980’s)
• Inlet performance and
recovery
• Fan noise and noise
propagation
• Tested for noise in the
NASA GRC 9x15
• Confirmed aux doors,
bleed systems, other
details can have a big
effect on fan noise
• Soft choke beneficial for
noise, bad for operability
Objective
• Validate and provide guidance on use of fan noise
models for CST system studies
• Investigating an optimized design for range, boom,
community noise
• ANOPP2 (Aircraft Noise Prediction Program)
• Propagation
• Prediction
• Airframe Noise • Engine Noise • Jet • Core • Fan • Heidmann • HSRNoise F120
Empirical Fan Noise Model #1
1.6 Heidmann Fans 1.5 AlliedSignal/Honeywell Fans
Heidmann
1.4 GE Aircraft Engine Fans
• Four versions
1.3 CF6-80C2 • Original (1979) 1.2 Energy Efficient Engine (E3) • AlliedSignal/ Honeywell 1.1 Quiet Clean Short-Haul (1996) Experimental Engine (QCSEE) Design Tip Mach Number • GE Aircraft Engines 22" GE High Speed Fan (1996) 0.9 22" Quiet High Speed Fan • Krejsa /Stone (2014) 0.8 22" R4 Fan from NASA Source 1 1.2 1.4 1.6 1.8 2 Diagnostic Test
• 5 sources
Fan Pressure Ratio • Inlet Broadband • Inlet Blade Rate Tones • Inlet Multiple Pure Tones • Aft Broadband • Aft Blade Rate Tones
Empirical Fan Noise Model #2
F120 Fan Model
• Developed during NASA
High Speed Research
program (1990 - 1999)
• Developed from GE
Engine data
• 3 - stage fan
• Only models front fan
• 2 sources
• Inlet Broadband
• Inlet Blade Rate Tones
Fans to Compare vs Model
2 - Stage Fan QHSF GE HSF Geometric Parameters Blade Count 26 and 42 22 24 or 34 Vane Count 72 and 104 52 52 or 80 Fan Inlet Annular Area, m2 (ft2) 0.162 (1.74) 0.216 (2.32) 0.222 (2.39) Fan rotor diameter, cm (in) 48 (19) 56 (22) 56 (22) Hub/Tip Ratio 0.34 0.35 0.31 Design Point Performance Parameters Design RPM 16670 15444 15105 Design Pressure Ratio 2.4 1.82 1.76 Tip Speed, m/s ( ft /s) 429 (1406) 449 (1474) 442 (1450) Axial Rotor - stator spacing (in rotor tip chords) 0.55 2.4 2.54 Corrected Fan Airflow, kg/s (lbm/s) 29.9 (66) 44.9 (98.9) 45.4 (100) Average Bypass Fan Temperature Ratio 1.32 1.21 1.21 2 - Stage Fan (2002) Quiet High - Speed Fan (2000) GE High Speed Fan (1999) Microphone Traverse Track
Data Collection
135º
and Processing
Barrier Wall Flow 30º End of Fan
• Start with
Start of Traverse Stacking Traverse Axis
narrowband
spectra, 1 - ft
lossless
RDG 2554, Angle = 62.9 90 Total
• Separate Tones
Broadband BPF
from
PSD, dB
Broadband
3 4 10 10 Total Frequency, Hz
• Sort tones into
Broadband Tones BPF
BPF or MPT
MPT
• Convert to 1/3
TOB Level, dB
Octave
3 4 10 10 Frequency, Hz
2 - Stage Fan
• IGVs operate on a
schedule
• First fan BPF tone
Measured Moving Median
and harmonics
BPF Tones BPF Tones
dominate
• Second fan BPF
barely noticable
PSD, dB
• Fairly few other
tones
• Broadband noise
3 4 10 10 Frequency, Hz
2 - Stage Fan Tone Level vs
F120 Fan Model
• 92.1% Speed (maximum tested)
• Model largely captures slope and level of BPF tone
• Noise metric penalizes tones
• Broadband noise under - predicted
BPF (Measured) Broadband (Measured) 1st Harmonic (Measured) Broadband (Model) BPF (Model) 140 140 1st Harmonic (Model) 130 130 Tone Power Level, dB 110 Sound Power Level, dB 20 40 60 80 20 40 60 80 Emitted Angles, Degrees from Upstream Emitted Angles, Degrees from Upstream
GE High Speed Fan vs
Heidmann Fan Noise Model
• 3 fans
• Wide Chord
• Forward Swept
• Shrouded
• 3 stators
• Baseline Radial Sweep
• Lean & Radial Sweep
• Integral (not used with barrier wall )
• 12 fan speeds
Forward Swept fan with Barrier Wall in 9x15 LSWT
Find best fit to data
• Equal weighting for each one - third octave band &
directivity
• At speeds above 85%
• GE model works best for Broadband and MPTs • Honeywell model fit best for BPF tones BPF Tones Multiple Pure Tones Broadband 10 10 10 Heidmann Original AlliedSignal/Honeywell GE Aircraft Engines 8 8 8 Krejsa/Stone 6 6 6 4 4 4 2 2 2 Mean MPT Error, dB Mean BPF Tone Error, dB Mean Broadband Error, dB 0 0 0 60 80 100 60 80 100 60 80 100 13 Pct Speed Pct Speed Pct Speed
Honeywell Quiet High Speed Fan
• Two fans tested
• Baseline fan a
scale model of
TFE731 - 60
• Forward swept
fan, designed
to reduce
takeoff EPNL
• Stator set for
each fan
Baseline Fan Forward Swept QHSF
QHSF Broadband
• GE version of Heidmann fan model best fit for
broadband, but over - predicts at most emission
angles
Baseline Fan QHSF Original AlliedSignal/Honeywell GE Aircraft Engines Krejsa/Stone Overall Sound Pressure Level, dB 20 40 60 80 Emitted Angle, degrees
QHSF BPF Tones
• Honeywell method closest for BPF noise, but again
overprediction , especially at aft angles
Baseline Fan QHSF Original AlliedSignal/Honeywell GE Aircraft Engines Krejsa/Stone BPF and Harmonics Tone Level, dB 20 40 60 80 Emitted Angle, degrees
QHSF MPTs
• MPTs much lower than any models
• GE method predicts smallest MPTs
Baseline Fan QHSF Original AlliedSignal/Honeywell GE Aircraft Engines Krejsa/Stone Overall Sound Pressure Level, dB 20 40 60 80 Emitted Angle, degrees
Simulated Flyover: 2 Stage fan
• Straight and level, 1000’, Mach = 0.30
• Fan inlet noise only, three engines
• 2 - Stage fan sized to LM 1044 1.65 (65”) diameter
• BPF tone dominates
Flyover Noise, dB 2-Stage Fan Test Data EPNL = 97.9 dB F120 Model EPNL = 98.4 dB -15 -10 -5 0 5 10 Time, seconds
Simulated Flyover: Single Stage Fan
• Straight and level, 1000’, Mach = 0.30
• Fan inlet noise only, three engines
• QHSF scaled to match fan thrust of 2 - Stage fan
• 2.34m (92.2”) diameter
Each model component over predicted 5 to 10 dB Flyover Noise, dB quieter than 2 - Stage Fan QHSF Test Data EPNL = 86.3 dB Heidmann Fan Model EPNL 92.0 dB -15 -10 -5 0 5 10 Time, seconds
Conclusions
• High speed fan data from 9x15 LSWT compared with Heidmann and F120 fan models • 2 - Stage Fan noise dominated by first rotor BPF • F120 model matches measurements reasonably well • Two single stage fans evaluated • GE High - Speed Fan • Honeywell Quiet High - Speed Fan • Guidance for use of Heidmann fan model: • GEAE model for broadband • AlliedSignal/Honeywell model for blade rate tones • MPTs may be over - predicted by all models • Single stage fan 5 - 10 dB quieter • System studies should include fan noise • Still need to consider aux doors, inlet flow distortion