Paper ETC9 089

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  Amplification of the force and tonal noise in HP turbine. Presented at the 9th European Turbomachinery Conference.
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  • 1. AMPLIFICATION OF THE FORCE AND THE TONAL NOISEIN TRANSONIC HIGH-PRESSURE TURBINES Stefano Bianchi1, Alessandro Corsini1, Guillermo Paniagua 2 1 Department of Mechanical and Aerospace Engineering, Sapienza – University of Rome, Roma, Italy, 2 Turbomachinery and Propulsion Department, von Karman Institute, Rhode Saint Genese, Belgium, Karman Institute
  • 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.von Karman Institute
  • 3. Introduction- Launch crews, on aircraft carriers, are exposed to excessivenoise levels during takeoffs and landings leading to costly andescalating hearing loss compensation programs. Pictures Marine Nationale von Karman Institute
  • 4. Introduction-  Typically launch/recovery supportpersonnel can be exposed to brutalacoustic loads of up to 150 dBA. Eachlaunch typically involves a 30 sec averagemil power exposure (occasionally full AB).-  The carrier deck personnel may Picture US Navyexperience up to 200 launches/recoveriesper 12 hr duty shift. The goal of engines noise reduction is considered of high importance. von Karman Institute
  • 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 remarksvon Karman Institute
  • 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 noiseis comparable with the rearcomponent of compressor noise:directed roughly to the engine side. Rolls-Royce, 2006 von Karman Institute
  • 7. Tested HPT rotor DS re EA Pictu SNECMAvon Karman Institute
  • 8. Generalities Paniagua et al., 2008Uncooled cylindrical vanes and uncooled rotor leaned blades P01/Ps3 Re2c M2,is M3r,isLow 2.42 1.06×106 1.07 0.65Nom 3.86 1.07×106 1.24 0.97High 5.12 1.07×106 1.24 1.183 pressure ratios investigated at 6500 RPM von Karman Institute
  • 9. Experimental apparatusvon Karman Institute
  • 10. Generalities Test facilitySimilarity to engine conditions: Re, M, Tgas/Twall and Tgas/Tcooling ratios.Transient operation: lower cost, heat transfer measurementsAbsence of brake  turbine torque = Inertia×accelerationTest section diameter 800 mmFixed and rotation measurements, with an opto-electronic transmission systemvon Karman Institute
  • 11. Generalities Test facility Plane 1 Plane 3Nearly constant conditions during 0.3sAveraging region 40msP & T variation below 0.3%von Karman Institute
  • 12. ΔP [mbar] blade signature BPF =: 6.7 kHz 1st harmonicvon Karman Institute 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 RRotor flow field Mid-span P01/Ps3=3.86 von Karman Institute
  • 14. Analysis of Results Paniagua et al., 2008 Max Variation (gauge 3): 27 % of P01 S RRotor flow field Low Nom High Vane trailing edge shock 0! 50% von Karman Institute
  • 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-diskAngle Blade Force Disk ForceFmodulus[kN/m] [kN/m] Ftan-disk von Karman Institute
  • 16. Sound prediction technique – FWHSound prediction technique based on Ffowcs William-Hawkings equation Monopole Dipole Quadrupolevon Karman Institute
  • 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, 1975von Karman Institute
  • 18. Sound prediction technique -  Discussion of the predicted rotor noise emission -  Quadrupolar sources and collapsing sphere Brentner and Farassat, 1995 Ianniello, 1999von Karman Institute
  • 19. Sound prediction technique -  Limitations: -  quadrupolar sources -  duct modes -  Non-linearitiesvon Karman Institute
  • 20. Acoustic model input S R-  Time resolved unsteady pressure fluctuation-  Gauges @ 50% blade span-  Calculated local Mach number on the gauge 50% von Karman Institute
  • 21. Acoustic model input Vane Phase [I] 0.89→10.89→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 von Karman Institute
  • 22. Sound prediction – dipolar sources onlyObserver position at 30 m of distance in the rotor plane (Ianniello 1999) Observer time [s] Observer time [s] von Karman Institute
  • 23. Sound prediction – OSPL @dipole only20 dB BPF 2nd BPF 3rd BPFSPL [dB] Frequency [kHz] von Karman Institute
  • 24. Sound prediction – all sources Observer time [s] Observer time [s] Observer time [s] Observer time [s]von Karman Institute
  • 25. Sound prediction - OSPL20 dB 3rd BPF BPF 2nd BPF 23.5SPL [dB] 9.40 11.75 2.35 Frequency [kHz] von Karman Institute
  • 26. vane pressure vs far-field noise spectral comparison P2 3rd BPF BPF 1st harmonic 2nd harmonic 2nd 3rd harmonic blade signatureΔP [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 von Karman Institute
  • 27. Predicted spectra composition Farassat formulation + quadrupoleSPL [dB] Farassat formulation only (dipole) Frequency [kHz] Rolls-Royce - 2006 von Karman Institute
  • 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. von Karman Institute
  • 29. AMPLIFICATION OF THE FORCE AND THE TONAL NOISEIN TRANSONIC HIGH-PRESSURE TURBINES Stefano Bianchi1, Alessandro Corsini1, Guillermo Paniagua 2 1 Department of Mechanical and Aerospace Engineering, Sapienza – University of Rome, Roma, Italy, 2 Turbomachinery and Propulsion Department, von Karman Institute, Rhode Saint Genese, Belgium, Karman Institute
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