W-8 Inlet In-duct Array Evaluation

Transcription

1 T15:19:18+:Z National Aeronautics and Space Administration W-8 Inlet In-duct Array Evaluation Rick Bozak NASA Glenn Research Center Acoustics Technical Working Group Meeting NASA Langley Research Center April 1-11, 218 NASA Advanced Air Vehicles Program Advanced Air Transport Technology Project Aircraft Noise Reduction Subproject

2 Outline W-8 Inlet In-duct Array Source Diagnostic Test - Rotor Alone Nacelle Comparison W-8 Background Noise Identification Evaluation of a BPF Cut-on Mechanism Summary 2

3 W-8 Single Stage Axial Compressor Facility Array Location Internal flow propulsor facility Electric drive motor provides up to 7 hp, 21,24 RPM Mass Flows up to lb m /sec 22 Rotor Alone or Stage Fan Models Dual Flow or Bypass only Atmospheric or Altitude Exhaust Capability 3

4 Source Diagnostic Test (SDT) Rotor Alone Nacelle (RAN) Comparison SDT RAN [4,5] 9x15 Low Speed Wind Tunnel Flight Inlet 6 sensor inlet circumferential array ½ circle, 3 spacing m +/- 6 W-8 Rotor Alone: Hardwall Configuration W-8 Internal Flow Compressor Straight 22 diameter duct 43 sensor inlet circumferential array ~½ circle, 4 spacing m +/- 44 4

5 SPL (db ref. 2 Pa) W-8 9x15 5% Speed Comparison Atmospheric Exhaust Low Frequency Broadband BPF and harmonics are cut-on and broad SDT RAN W SDT RAN - 5% Speed Spinning Mode (m) W-8-5% Speed < Aliased Co-rotating Modes Counter-rotating Co-rotating Spinning Mode (m)

6 Alpha In-duct Array Data Processing to In-duct Mode Powers Cross-Spectral Matrix Duct Wavenumber Space SPL Cuton Condition α = ± 1 1 M 2 k N k 2 Mode Powers Aft Propagating Forward Propagating Counter-rotating Modes Co-rotating Modes *To be presented at 218 AIAA Aviation: Dougherty, R. P., and Bozak, R. F., Two-dimensional Modal Beamforming in Wavenumber Space for Duct Acoustics. 6

7 Cuton Ratio ( ) In-duct Modal Decomposition Hardwall 5% Speed 115 Total Sound Power Total Forward Propagating Forward Propagating and Co-Rotating 15 Forward Propagating Plane Waves Sound Power Level (db ref. 1 pw) Counter-rotating Modes In-duct PWL: 1523 Hz Aft Propagating Forward Propagating Co-rotating Spinning Mode (m) Sound Power Level (db ref. 1 pw) 95 Modes Corrected Hardwall 5% Speed Corrected *Impact of treatments using this decomposition to be presented at 218 AIAA Aviation: Bozak, R. F., and Dougherty, R. P., Measurement of Noise Reduction from Acoustic Casing Treatments Over a Subscale High Bypass Turbofan Rotor. 7

8 Noise from Flow Through the Facility Utilized Altitude Exhaust to pull flow through the facility with a dummy hub installed (no fan blades). 15 Forward Propagating Aft Propagating Sound Power Level (db ref. 1 pw) lb/s 8 lb/s

9 Both Broad Cut-on Why is BPF Cut-on and Broad in W-8 Measurements? SPL (db ref. 2 Pa) SDT RAN W SDT RAN - 5% Speed 1. BPF could be cut-on from an inlet static pressure distortion. Circumferential 8 Mach number variation is not significant: measured to be less than.1 (see backup slide). BPF is not modulated about the shaft speed The 2 BPF tone could broaden as the sound propagates through a boundary layer turbulence to the sensors The tone broadness does not appear to vary with Spinning boundary Mode (m) layer thickness (see backup slide). 3. The 8 BPF frequency could be wandering, causing the appearance of a broad 12 tone 6 when averaged. Does not appear to be the case (see backup slide). 4 2 W-8-5% Speed 4. Increased freestream or boundary layer turbulence from the W-8 inlet Spinning Mode (m) bellmouth could create turbulence-rotor interaction tones that are not present with the 9x15 flight inlet

10 Turbulence-Rotor Interaction Noise Honeywell engine test data shows a skirt around tones measured in an indoor test facility, while outdoor test data did not exhibit this skirt. An analytical model provided by Gliebe and Kerschen shows that the broadness turbulence rotor interaction BPF tones is driven by inlet turbulence length scales (larger length scales create broader tones). Honeywell Engine Test Data Analytical Model for Turbulence-Rotor Noise Marotta, T., Schuster, B., A Comparison of Fan Inlet Dynamic Wall Pressure Transducers from Rig and Engine Tests, AIAA , AIAA Aeroacoustics Conference, Colorado Springs, CO, June 212. Gliebe, P. R., and Kerschen, E. J., Analytical Study of the Effects of Wind Tunnel Turbulence on Turbofan Rotor Noise, NASA CR ,

11 BPF Tone Envelope Investigation Envelope = sqrt(lowpass(signal^2)) Power Spectral Density (db/hz) Pressure (Pa) Power Spectral Density (db/hz) % Speed Microphone Signal BPF BPF Modulation BPF Envelope Time (s) Frequency Content of BPF Envelope

12 Inlet Turbulence Spectral Comparison Flight Inlet 9x15 LSWT Inlet Bellmouth W SDT RAN Inlet Turbulence - lb/s 1 6 W-8 Inlet Turbulence - 87 lb/s Boundary Layer 1 4 Boundary Layer PSD, u' 2 (ft 2 /s) PSD, u' 2 (ft 2 /s) Free Stream 1-1 Free Stream

13 Summary In-duct noise levels were compared between the W-8 internal flow facility and the 9x15 LSWT with the R4 fan in a rotor alone configuration. Rotor alone measurements were found to be a few db louder than Source Diagnostic Test (SDT) Rotor Alone Nacelle in-duct measurements with a few exceptions: When running W-8 in the atmospheric exhaust configuration, up to 1dB of additional broadband noise from -2, Hz. This is believed to be due to flow over rods in the exhaust. In W-8, BPF tones are cut-on and broad. The broadness of the tones appear to be a product of inlet boundary layer turbulence differences between the flight inlet in the 9x15 and inlet bellmouth in W-8. The same characteristics are seen in Honeywell data 5 and in a Gliebe analytical model 7. Recommendations: Reduce W-8 background noise by modifying rods in the W-8 exhaust collector Further investigate facility inlet turbulence differences 13

14 References 1. Hughes, Christopher E., Jeracki, Robert J., and Miller, Christopher J., Fan Noise Source Diagnostic Test Rotor Alone Aerodynamic Performance Results, AIAA or NASA TM Van Zante, Dale E., Podboy, Gary G., Miller, Christopher J., Thorp, Scott A., Testing and Performance Verification of a High Bypass Ratio Turbofan Rotor in an Internal Flow Component Test Facility, GT Premo and Joppa, Fan Noise Source Diagnostic Test Wall Measured Circumferential Array Mode Results, AIAA Heidelberg, L., Fan Noise Source Diagnostic Test Tone Modal Structure Results, AIAA and NASA/TM Marotta, T., Schuster, B., A Comparison of Fan Inlet Dynamic Wall Pressure Transducers from Rig and Engine Tests, AIAA , AIAA Aeroacoustics Conference, Colorado Springs, CO, June Smith, E. B., Moore, M. T., and Gliebe, P. R., Distortion Rotor Interaction Noise Produced by a Drooped Inlet. AIAA Gliebe, P. R., and Kerschen, E. J., Analytical Study of the Effects of Wind Tunnel Turbulence on Turbofan Rotor Noise, NASA CR Bozak, R., Inlet Acoustic Data from a High Bypass Ratio Turbofan Rotor in an Internal Flow Component Test Facility NASA/TM Dougherty, R. P., and Bozak, R. F., Two-dimensional Modal Beamforming in Wavenumber Space for Duct Acoustics, To be presented at for 218 AIAA Aviation Forum. 1. Bozak, R., F., and Dougherty, R. P., Measurement of Noise Reduction from Acoustic Casing Treatments Installed Over a Subscale High Bypass Ratio Turbofan Rotor, To be presented at 218 AIAA Aviation Forum. 14

15 BACKUP SLIDES 15

16 W-8 Single Stage Axial Compressor Facility Internal flow propulsor facility Electric drive motor provides up to 7 hp, 21,24 RPM Mass Flows up to lb m /sec 22 Rotor Alone or Stage Fan Models Dual Flow or Bypass only Atmospheric or Altitude Exhaust Capability 1 6

17 W-8 Single Stage Axial Compressor Facility Schematic Internal flow propulsor facility Electric drive motor provides up to 7 hp, 21,24 RPM Mass Flows up to lb m /sec 22 Rotor Alone or Stage Fan Models Dual Flow or Bypass only Atmospheric or Altitude Exhaust Capability 17

18 Inlet In-duct Array Instrumentation 22-inch constant area inlet duct 85 sensors Kulite 25PSIA Installed into nylon inserts T-Array ½ Circle, 4 Spacing Long Axial Staggered Short Axial 18

19 SDT/R4 Hardware The Source Diagnostic Test hardware was tested in a rotor alone configuration in the 9x15 wind tunnel 1 and the W-8 Single Stage Axial Compressor Facility 2 in the early 2 s Parameter Value No. of Fan Blades 22 Fan Tip Diameter 22 in. (.56m) Hub/tip Ratio.3 Corrected Tip Speed 1215 ft/s (37 m/s) Fan Design Speed, corrected rpm 12,657 Fan Design Pressure Ratio Hughes, Christopher E., Jeracki, Robert J., and Miller, Christopher J., Fan Noise Source Diagnostic Test Rotor Alone Aerodynamic Performance Results, AIAA or NASA TM Van Zante, Dale E., Podboy, Gary G., Miller, Christopher J., Thorp, Scott A., Testing and Performance Verification of a High Bypass Ratio Turbofan Rotor in an Internal Flow Component Test Facility, GT

20 5% Speed Comparison Altitude (Choked) Exhaust SPL (db ref. 2 Pa) SDT RAN W SDT RAN - 5% Speed Fan Exit Rake Effect Spinning Mode (m) W-8-5% Speed Spinning Mode (m) 8 21

21 W-8 Noise Comparison at 5% Speed With no fan installed (only a dummy hub): Rotated a dummy hub up to expected fan speeds. Utilized Altitude Exhaust to pull flow through the facility up to choke at 87 lbm/s. 12 Rotation Flow Fan with Alt. Fan with Atmos. Sound Power Level (db ref. 1 pw)

22 Flow Noise 23

23 Effect of Choking the Exhaust Nozzle on Flow Noise Sound Power Level (db ref. 1 pw) lbm/s - Forward Propagating 8 lbm/s - Aft Propagating Choked - Forward Propagating Choked - Aft Propagating 85 lbm/s - Unsteady Shock Noise

24 W-8 Background Effects SPL (db ref. 2 Pa) Hardwall - 5% Speed W-8 Atmospheric Acoustic W-8 Atmospheric Rakes W-8 Altitude Rakes Effect of Fan Exit Rakes Spinning Mode (m) Effect of Exhaust Configuration Spinning Mode (m) -1 25

25 Background Subtracted SDT RAN Comparison 61.7% Speed SPL (db ref. 2 Pa) SDT RAN W SDT RAN % Speed Spinning Mode (m) W % Speed Spinning Mode (m) 8 26

26 Background Subtracted SDT RAN Comparison 75%, 77.5% Speed SPL (db ref. 2 Pa) SDT RAN W SDT RAN - 75% Speed Spinning Mode (m) W-8-75% Speed Spinning Mode (m) 8 27

27 Background Subtracted SDT RAN Comparison 87.5% Speed SPL (db ref. 2 Pa) SDT RAN W SDT RAN % Speed Spinning Mode (m) W % Speed Spinning Mode (m) 8 28

28 MPT/Buzzsaw Noise Difference Axial Mach Number Circumferential Mach Number Tip Relative Mach Number % Span % Span % Span W-8 - Uniform Flow Assumption W-8 - Straight Inlet 9x15 SDT RAN - Flight Inlet Axial Mach Number Circumferential Mach Number 82 W-8 - Uniform Flow Assumption W-8 - Straight Inlet 9x15 SDT RAN - Flight Inlet Tip Relative Mach Number Fan tip goes sonic sooner with a cleaner boundary layer (SDT RAN data). 29

29 Measured BPF Timeseries - Zoom Bandpassed BPF with Skirt Pressure (Pa) Time (s) Pressure (Pa) Time (s) Pressure (Pa) Time (s) 3

30 Is BPF Broad because the tone is wandering? no 1 second sample broken into -.1 second samples. Average of all in black Sound Pressure Level (db ref. 2 Pa)

31 SPL Variation Over Axial Array - 5% Speed If the tone were broadened when propagating through the boundary layer turbulence, we d expect to see variation over the axial array as the boundary layer grows Sound Pressure Level (db ref. 2 Pa)

32 Is there an inlet static pressure distortion? Ring of 8 static pressures upstream of the fan. For each pressure, a Mach number is calculated: M = 2 γ 1 p p t 1 γ γ 1.5 Inlet Static Pressure Variation from Mean.5 Inlet Mach Number Variation Pressure (PSIA).2.1 Cond Cond. 2 Cond Cond. 4 Cond Cond. 6 Cond Cond. 8 Cond Location (degrees) Mach Number Location (degrees) *Smith, E. B., Moore, M. T., and Gliebe, P. R., Distortion Rotor Interaction Noise Produced by a Drooped Inlet. AIAA

33 Analytical Model of Turbulence-Rotor Interaction Given by Gliebe and Kerschen (1979 NASA CR ) Variation with Axial Turbulence Length-Scale Variation with Tangential Turbulence Length-Scale *Gliebe, P. R., and Kerschen, E. J., Analytical Study of the Effects of Wind Tunnel Turbulence on Turbofan Rotor Noise, NASA CR

34 Inlet Turbulence Comparison 3 SDT Flight Inlet ~ lb m /s 3 SDT Flight Inlet ~ lb m /s W-8 Inlet ~ 87 lb m /s W-8 Inlet ~ 87 lb m /s Immersion (inches) 1.5 Immersion (inches) u/u Turbulence Intensity (%) 35

35 Comparison with Inlet Turbulence Measurements (Hotfilm) Acoustic BPF Envelope - 5 lb/s W-8 Boundary Layer Turbulence - 87 lb/s W-8 Free-stream Turbulence - 87 lb/s SDT RAN Boundary Layer Turbulence - lb/s SDT RAN Free-stream Turbulence - lb/s PSD [db/hz] PSD [log(u1 2 )/Hz]

36 Recreation of Turbulence-Rotor Interaction Tone Broadening Each boundary layer source is modelled as a Shannon wavelet (sinc), as shown below. The noise from boundary layer impingement with the fan blades is modulated at the BPF. Many of these sources are present at any given time, and have are give a random distribution of amplitudes, length-scales, and phases. Amplitude (db) Amplitude (db) Amplitude 1 BPF Wavelet BPF * Wavelet Time (s) 5 BPF 3 - BPF * Wavelets BPF - BPF * Wavelets

37 Recreation of the spectra analytically BPF 1 - BPF * Wavelets Amplitude (db) BPF - BPF * Wavelets Amplitude (db) Wavelets with a uniform random distribution of widths, phases, and amplitudes. 38

38 Recreation of the BPF Modulation Analytically Amplitude BPF BL Turbulence Time (s) Amplitude BPF BL Turbulence Time (s) Amplitude (db) 8 6 BPF BL Turbulence