1. AMPLIFICATION OF THE FORCE
AND THE TONAL NOISE
IN TRANSONIC HIGH-PRESSURE TURBINES
Stefano Bianchi1, Alessandro Corsini1, Guillermo Paniagua 2
1 Department of Mechanical and Aerospace Engineering, Sapienza – University of Rome, Roma, Italy,
bianchi@dma.ing.uniroma1.it
2 Turbomachinery and Propulsion Department, von Karman Institute, Rhode Saint Genese, Belgium,
paniagua@vki.ac.be
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2. Introduction
- Current military tactical aircraft operate from bases
close to communities. Naval tactical aircraft in
particular are based close to appreciating waterfront
real estate.
- Altering training flight operations to minimize noise
impact is considered restrictive for aircrews and leads
to flight training shortfalls, particularly for carrier-based
pilots who need to “train-as-they-fight”.
- The Secretary of the US Navy, has estimated a total
potential liability of $350 million should litigants prevail
in lawsuits involving jet noise.
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3. Introduction
- Launch crews, on aircraft carriers, are exposed to excessive
noise levels during takeoffs and landings leading to costly and
escalating hearing loss compensation programs.
Pictures Marine Nationale
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4. Introduction
- Typically launch/recovery support
personnel can be exposed to brutal
acoustic loads of up to 150 dBA. Each
launch typically involves a 30 sec average
mil power exposure (occasionally full AB).
- The carrier deck personnel may Picture US Navy
experience up to 200 launches/recoveries
per 12 hr duty shift.
The goal of engines noise reduction is considered of
high importance.
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5. Outline
- Methodology
- Tested HPT rotor and experimental apparatus
- Discussion of the experimental results.
- Sound prediction technique
- Rationale and background information
- Limits
- Discussion of the predicted rotor noise emission
- Mono and Dipolar sources
- Quadrupolar sources
- Concluding remarks
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6. Turbine noise in Low bpr TF engines
- For high by pass ratio engines turbine
noise account only during the Landing
operation, as the TO thrust is exerted
mainly by the fan.
- Low bpr engines are more senstive to
turbine noise, even for TO operation.
NASA report: FS-1999-07-003-GRC
- In low bpr engines turbine noise
is comparable with the rear
component of compressor noise:
directed roughly to the engine side.
Rolls-Royce, 2006
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10. Generalities Test facility
Similarity to engine conditions: Re, M, Tgas/Twall and Tgas/Tcooling ratios.
Transient operation: lower cost, heat transfer measurements
Absence of brake turbine torque = Inertia×acceleration
Test section diameter 800 mm
Fixed and rotation measurements, with an opto-electronic transmission system
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11. Generalities Test facility
Plane 1 Plane 3
Nearly constant conditions during 0.3s
Averaging region 40ms
P & T variation below 0.3%
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12. ΔP [mbar]
blade signature
BPF =: 6.7 kHz
1st harmonic
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2nd harmonic
Frequency Analysis
P2
Frequency [kHz]
3rd harmonic
resonance
ΔP [mbar]
Generalities
vane signature
VPF = 4.7 kHz
1st harmonic
2nd harmonic
Paniagua et al., 2008
3rd harmonic
4th harmonic
Frequency [kHz]
PROTOR
13. Analysis of Results Paniagua et al., 2008
S R
Rotor flow field
Mid-span P01/Ps3=3.86
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14. Analysis of Results Paniagua et al., 2008
Max Variation (gauge 3): 27 % of P01 S R
Rotor flow field
Low
Nom High
Vane trailing edge shock 0!
50%
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15. Analysis of Results
Blade force
Max. Variations
Axial force 8.95% of mean level (Low P/P)
Tangential force 12.6% of mean level (Nom P/P)
[kN/m]
[deg.]
Fax-disk
Angle
Blade Force Disk Force
Fmodulus
[kN/m]
[kN/m]
Ftan-disk
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16. Sound prediction technique – FWH
Sound prediction technique based on Ffowcs William-Hawkings
equation
Monopole
Dipole
Quadrupole
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17. Sound prediction technique – FWH
Farassat formulation of FWH integrals
for Monopole and Dipole sources
Thickness noise-Monopole
Near-field loading noise-Dipole
Far-field loading noise-Dipole
Farassat, 1975
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18. Sound prediction technique
- Discussion of the predicted rotor noise emission
- Quadrupolar sources and collapsing sphere
Brentner and Farassat, 1995
Ianniello, 1999
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19. Sound prediction technique
- Limitations:
- quadrupolar sources
- duct modes
- Non-linearities
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20. Acoustic model input
S R
- Time resolved unsteady pressure fluctuation
- Gauges @ 50% blade span
- Calculated local Mach number on the gauge 50%
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21. Acoustic model input
Vane Phase [I]
0.89→1
0.89→1 Direct shock : Crown and LE SS
0.25→0.5 No Shock Vane Phase [III]
0.7→0.77 Reflected vane shock : PS 0.7 → 0.77
Vane Phase [II]
0.25 →0.5
- Time resolved unsteady pressure fluctuation
- Gauges @ 50% blade span 50%
- Calculated total force on the gauge absolute value
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22. Sound prediction – dipolar sources only
Observer position at 30 m of distance in the rotor plane (Ianniello 1999)
Observer time [s]
Observer time [s]
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23. Sound prediction – OSPL @dipole only
20 dB
BPF
2nd BPF
3rd BPF
SPL [dB]
Frequency [kHz]
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24. Sound prediction – all sources
Observer time [s]
Observer time [s]
Observer time [s]
Observer time [s]
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25. Sound prediction - OSPL
20 dB 3rd BPF
BPF
2nd BPF
23.5
SPL [dB]
9.40
11.75
2.35
Frequency [kHz]
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26. vane pressure vs far-field noise spectral comparison
P2
3rd
BPF
BPF
1st harmonic
2nd harmonic
2nd
3rd harmonic
blade signature
ΔP [mbar]
BPF =: 6.7 kHz
SPL [dB]
BPF
resonance
23.5
9.40
2.35 11.75
Frequency [kHz] Frequency [kHz]
Rotor acoustic near-field Rotor acoustic far-field
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27. Predicted spectra composition
Farassat formulation + quadrupole
SPL [dB]
Farassat formulation only (dipole)
Frequency [kHz]
Rolls-Royce - 2006
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28. Sound prediction technique
- Concluding remarks
- Measurements of unsteady pressure fluctuations were carried on a hpt stage,
characteristic of the modern high loaded turbine rotor design.
- The experimental data-set was used as input for a basic FW-H rotor noise
prediction model.
- The predicted tonal noise appears fairly consistent with the expected results,
even if the lack of dedicated experimental noise measurement does not allow
the authors to consider the prediction accurate.
- The quadrupole approximation used seems to saturate the predicted noise
spectra and overpredict the SPL: questions arise form this behavior.
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29. AMPLIFICATION OF THE FORCE
AND THE TONAL NOISE
IN TRANSONIC HIGH-PRESSURE TURBINES
Stefano Bianchi1, Alessandro Corsini1, Guillermo Paniagua 2
1 Department of Mechanical and Aerospace Engineering, Sapienza – University of Rome, Roma, Italy,
bianchi@dma.ing.uniroma1.it
2 Turbomachinery and Propulsion Department, von Karman Institute, Rhode Saint Genese, Belgium,
paniagua@vki.ac.be
von Karman Institute
