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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Paper ETC9 089

  1. 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. 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. 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. 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. 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. 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. 7. Tested HPT rotor DS re EA Pictu SNECMAvon Karman Institute
  8. 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. 9. Experimental apparatusvon Karman Institute
  10. 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. 11. Generalities Test facility Plane 1 Plane 3Nearly constant conditions during 0.3sAveraging region 40msP & T variation below 0.3%von Karman Institute
  12. 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. 13. Analysis of Results Paniagua et al., 2008 S RRotor flow field Mid-span P01/Ps3=3.86 von Karman Institute
  14. 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. 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. 16. Sound prediction technique – FWHSound prediction technique based on Ffowcs William-Hawkings equation Monopole Dipole Quadrupolevon Karman Institute
  17. 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. 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. 19. Sound prediction technique -  Limitations: -  quadrupolar sources -  duct modes -  Non-linearitiesvon Karman Institute
  20. 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. 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. 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. 23. Sound prediction – OSPL @dipole only20 dB BPF 2nd BPF 3rd BPFSPL [dB] Frequency [kHz] von Karman Institute
  24. 24. Sound prediction – all sources Observer time [s] Observer time [s] Observer time [s] Observer time [s]von Karman Institute
  25. 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. 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. 27. Predicted spectra composition Farassat formulation + quadrupoleSPL [dB] Farassat formulation only (dipole) Frequency [kHz] Rolls-Royce - 2006 von Karman Institute
  28. 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. 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