For STAR South East Asian Conference 2015

Transcription

1 Click to edit Master title style For STAR South East Asian Conference 2015 Prediction of noise emission from the NASA SR-2 Propeller 8-9 June 2015 Mr Voo Keng Soon Mr Tan Chun Hern Mr Lim Nee Sheng Winson Dr Siauw Wei Long 1 Slide 1

2 Click to edit Master title style A big thank you to CD-adapco for the provision of technical assistance and advice! Dr Mark Farrall Dr Fred Mendonça Dr Amel Boudjir Dr Jason Fernandes 2 Slide 2

3 Click to edit Master title style Motivation Fundamental study of noise emission from flow over propeller Second level Comparison of the usage of acoustics analogy and direct measurement method for computational aeroacoustics Fourth level Investigate the appropriate usage of Moving Reference Frame and Rigid Body Motion (sliding mesh) methodologies in the modelling of the propeller Study the behaviour of the propeller tip vortices in the presence of a generic wing NASA SR-2 propeller selected as validation case due to the availability of open source data 3 Slide 3

4 Click to edit Master title style Overview Propeller Basics Simulation Methodology Third level Generation of SR-2 propeller CAD Fourth Differences level between CFD Setups CFD Setup of SR-2 propeller SR-2: Analysis Propeller in the Presence of Generic Wing SR-2 + NACA0010: Analysis Summary 4 Slide 4

5 Click to edit Master title style Propeller Basics [1] held measured noise level and corresponding spectral representations on a Cessna 172N (twoblade to edit propeller) Master text while styles [2] tested the Cessna FR172F Click Second (three-blade level propeller) Third At level high propeller RPM, noise at the blade passing Fourth frequency level (BPF) is the dominant noise 2400rpm, 80Hz, 93.3dB 2400rpm, 120Hz, 91dB [1] D.Miljkovic, M.Maletic, M.Obad, Comparative Investigation of Aircraft Interior Noise Properties, 3 rd Congress of the Alps-Adria Acoustics Association. [2] D.Miljkovic, J. Ivosevic, T.Bucak, Two vs Three Blade Propeller Cockpit Noise Comparison, 5 th Congress of the Alps-Adria Acoustics Association. 5 Slide 5

6 Click to edit Master title style Propeller Basics 6 Slide 6

7 Click to edit Master title style Propeller Basics [3] J.E. Marte, D.w. Kurtz, A Review of Aerodynamic Noise From Propellers, Rotors, and Lift Fans, NASA CR [4] E.L. Chuan-Tau, J. Roskam, Airplane Aerodynamics and Performance, DARcorporation, USA. 7 Slide 7

8 Click to edit Master title style Propeller Basics [3] J.E. Marte, D.w. Kurtz, A Review of Aerodynamic Noise From Propellers, Rotors, and Lift Fans, NASA CR [4] E.L. Chuan-Tau, J. Roskam, Airplane Aerodynamics and Performance, DARcorporation, USA. 8 Slide 8

9 Click to edit Master title style Propeller Basics [3] J.E. Marte, D.w. Kurtz, A Review of Aerodynamic Noise From Propellers, Rotors, and Lift Fans, NASA CR [4] E.L. Chuan-Tau, J. Roskam, Airplane Aerodynamics and Performance, DARcorporation, USA. 9 Slide 9

10 Click to edit Master title style Propeller Basics D v a 10 Slide 10

11 Click to edit Master title style Propeller Basics [4][5] [4] E.L. Chuan-Tau, J. Roskam, Airplane Aerodynamics and Performance, DARcorporation, USA. [5] F.E. Weick, Aircraft Propeller Design, McGraw-Hill Book Company, USA 11 Slide 11

12 Click to edit Master title style Simulation Methodology The following was employed for this aeroacoustics study of the NASA SR-2 propeller 1. Generation of propeller geometry, followed by meshing within the domain 2. Second Upon completion level of volume meshing, simulation is setup to run steady state with Moving Reference Frame (MRF) 3. Converged steady solution is then used to calculate the propeller power coefficient, C p 4. Fifth Calibration level of blade angle through a series of steady state simulations at varied propeller blade angle, so as to match the predicted C p to the experimental C p 5. Upon calibration of the propeller blade angle, the simulation is then setup to run transiently with rigid body motion (sliding mesh) 6. The transient simulation is allowed to run for at least 10 propeller rotations to transit to a steady condition 7. Simulation is subsequently ran for a further 10 propeller rotations in order to record the pressure signal at the receivers 8. Pressure data recorded at the receivers processed to acquire sound pressure levels at the blade passing frequency (BPF) 12 Slide 12

13 Click to edit Master title style Simulation Methodology The following was employed for the physics modelling Steady Click to State edit Master Simulation text styles Steady Segregated flow Ideal Fifth gas level Segregated fluid enthalpy K-Ω SST All Y+ wall treatment Cell quality remediation Transient Simulation Implicit unsteady Segregated flow Ideal gas Segregated fluid enthalpy Detached Eddy Simulation (K-Ω based) All Y+ wall treatment Cell quality remediation Time step of 2.5e-5 seconds utilized to capture propeller rotation rate of 1 per time-step 10 inner iterations for convergence of time-step 13 Slide 13

14 Generation of SR-2 propeller CAD [6] Click to edit Master title style [6] G.L.Stefko, R.J.Jeracki, Wind Tunnel Results of Advanced High Speed Propellers in Takeoff, Climb & Landing Operating Regimes, AIAA Slide 14

15 Generation of SR-2 propeller CAD Click to edit Master title style Root portion (r/r from to 0.367) of propeller utilized modified NACA 65 series airfoil profiles having a circular arc mean camber line [7][8] NACA 16 series airfoil profiles [4] are utilized at the outer portion (r/r from to 1.0) of the propeller. [4] E.L. Chuan-Tau, J. Roskam, Airplane Aerodynamics and Performance, DARcorporation, USA. [7] N.A. Cumpsty, Compressor Aerodynamics, Longman Scientific & Technical, USA r/r t/b Corrected b/d Corrected CLD Corrected delta β Corrected β [8] D.C. Mikkelson, B.J. Blaha, G.A. Mitchell, J.E. Wikete, Design and Performance of Energy Efficient Propellers for Mach 0.8 Cruise, NASA TM X Slide 15

16 Generation of SR-2 propeller CAD Click to edit Master title style Fine tuning of digitalized data a) Blade thickness ratio, t/b was fine-tuned, knowing t/b at tip is 2% [8] b) Blade width ratio, b/d was fine-tuned, knowing blade activity factor AF=203 [8][9] c) Blade design lift coefficient, C LD was fine-tuned, knowing integrated design lift coefficient C LI = [8][9] d) Change in blade angle with respect to that at 75% blade radius, Δβ was fine-tuned, knowing Δβ=0 at 0.75 r/r [8][9] [8] D.C. Mikkelson, B.J. Blaha, G.A. Mitchell, J.E. Wikete, Design and Performance of Energy Efficient Propellers for Mach 0.8 Cruise, NASA TM X [9] G.L. Stefko, R.J. Jeracki, Wind-Tunnel Results of Advanced High-Speed Propellers at Takeoff, Climb, and Landing Mach Numbers, NASA TM Slide 16

17 Generation of SR-2 propeller CAD Slide 17

18 Generation of SR-2 propeller CAD Geometry generation of area-ruled spinner and turbine sting [9] The area-ruled spinner and turbine sting were designed to alleviate blade-root choking and to minimize compressibility drag rise. turbine sting [9] G.L. Stefko, R.J. Jeracki, Wind-Tunnel Results of Advanced High-Speed Propellers at Takeoff, Climb, and Landing Mach Numbers, NASA TM Slide 18

19 Generation of SR-2 propeller CAD The generated propeller blades fitted nicely with the spinner Inboard portion of propeller operates as a cascade rather than isolated blades Slide 19

20 Differences between CFD Setups Differences between earlier and current aeroacoustics studies of the NASA SR-2 propeller Improved CAD modelling of the propeller blades [4][7][8][9][10] Obtaining geometry data of spinner and turbine sting [9] Revised simulation conditions with inference from new literature [11][12] Inclusion of the acoustic plate in the modelling [13] previous setup current setup [10] T.A. Egolf, O.A. Anderson, D.E. Edwards, A.J. Landgrebe, An Analysis for High Speed Propeller-Nacelle Aerodynamic Performance Prediction, NASA-CR [11] J.H. Dittmar, and P.L. Lasagna, A Preliminary Comparison Between the SR-3 Propeller Noise in Flight and in a Wind Tunnel, NASA-TM [12] J.H. Dittmar, R.J. Jeracki, and B.J. Blaha, Tone Noise of Three Supersonic Helical Tip Speed Propellers in a Wind Tunnel, NASA-TM [13] J.H. Dittmar, R.J. Burns, D.J. Leciejewski, An Experimental Investigation of the Effect of Boundary Layer Refraction on the Noise From a High-Speed Propeller, NASA TM Slide 20

21 CFD Setup of SR-2 propeller Click to edit Master title style [13] J.H. Dittmar, R.J. Burns, D.J. Leciejewski, An Experimental Investigation of the Effect of Boundary Layer Refraction on the Noise From a High- Speed Propeller, NASA TM Slide 21

22 CFD Setup of SR-2 propeller Modelled geometry of plate (holding the installed pressure transducers) [13] Patches of 16mm diameter were imprinted on the base of the CAD geometry of the plate to represent the pressure probe points [13] J.H. Dittmar, R.J. Burns, D.J. Leciejewski, An Experimental Investigation of the Effect of Boundary Layer Refraction on the Noise From a High- Speed Propeller, NASA TM Slide 22

23 CFD Setup of SR-2 propeller Click to edit Master title style Trimmed hexahedral mesh with prism layers 97.3 million cells Wall Y+ < 1 at critical areas Unknown mass flow exiting from rear of air turbine sting Tangent ogive cylinder added to the rear to minimize undesirable noise generation due to abrupt flow separation (section Y=0) 23 Slide 23

24 SR-2 : Analysis Fixed Conditions Setup Propeller diameter (m) Cruise Mach 0.6 Environmental Conditions Pressure, P (Pa) Temperature, T (K) 279 speed of sound (m/s) corresponding to above P & T air density (kg/m 3 ) corresponding to above P & T Propeller Conditions Propeller rotation rate (RPM) Propeller rotation speed (m/s) propeller helical tip speed (m/s) propeller helical Mach advance ratio, J Simulation Output Propeller Torque, Q (Nm) P, shaft power (W) Power Coefficient Cp 1.32 from literature [8][9][10][11][12][13] Inferred from literature [11][12] US Standard Atmosphere 1976 Matched literature [14] Delta blade angle of -0.4 utilized to match experimental C p of 1.32 [14] [11] J.H. Dittmar, and P.L. Lasagna, A Preliminary Comparison Between the SR-3 Propeller Noise in Flight and in a Wind Tunnel, NASA-TM [12] J.H. Dittmar, R.J. Jeracki, and B.J. Blaha, Tone Noise of Three Supersonic Helical Tip Speed Propellers in a Wind Tunnel, NASA-TM [13] J.H. Dittmar, R.J. Burns, D.J. Leciejewski, An Experimental Investigation of the Effect of Boundary Layer Refraction on the Noise From a High-Speed Propeller, NASA TM [14] J.H. Dittmar, Cruise Noise of the SR-2 Propeller Model in a Wind Tunnel, NASA-TM Slide 24

25 Click to edit Master title style SR-2 : Analysis suction side suction side pressure side pressure side 25 Slide 25

26 Click to edit Master title style Pressure-time trace (probe on tunnel wall) Sinusoidal waveform observed in CFD Click Sinusoidal to edit waveform Master text observed styles in wind Second tunnel data level (SR-2, M0.6, J3.06) [15] Third Steep level fronted wave (approaches classic N Fourth wave shock level pattern) observed in wind Fifth tunnel level data (SR-2, M0.8, J3.07) [15] The latter is a good indication on the presence of sharp pressure rises normally associated with supersonic helical tip speed SR-2 : Analysis smaller peak to peak amplitude Helical tip mach 1.14 Helical tip mach [15] J.H. Dittmar, R.J. Jeracki, and B.J. Blaha, Tone Noise of Three Supersonic Helical Tip Speed Propellers in a Wind Tunnel, NASA-TM Slide 26

27 Click to edit Master title style Comparison with previous setup (using direct measurement) the Third current level setup exhibited a closer match in the sound pressure when With the updated geometries, compared to the experimental data A delta of db at probe 6 (@ X=0.3in) as compared to experimental data Pre-processing is important! Whenever possible, usage of better geometry CAD representation will lead to peace of mind SR-2 : Analysis previous setup current setup 27 Slide 27

28 Click to edit Master title style Comparison with previous setup (using FW-H Impermeable) Measurement locations are too close to source, noise does not necessarily meet farfield conditions Click to edit Master [11] text styles Ffowcs Williams-Hawkings (FW-H) method Second is a form level of acoustic analogy applied Third to reduce level aeroacoustics sound sources to simple emitter type Such Fourth methods level rely on near-field information gathered over surface(s) enclosing as much as possible the noise sources These methods propagate noise from source to receiver via analytical solution of the wave equation In the far field, sound behaves as in open air without reflecting surfaces to interfere with its propagation The near field is the area very close to the noise source where the sound pressure level may vary significantly with a small change in position Advantage of FW-H: Only require CFD solution around source, not expensive Disadvantage of FW-H: Cannot account for reflection [16] Acoustic analogy not recommended for this CFD setup SR-2 : Analysis Near Field Noise Sources FW-H (solve wave equation) CFD (solve Navier-Stokes) acoustic receiver Far Field [11] J.H. Dittmar, and P.L. Lasagna, A Preliminary Comparison Between the SR-3 Propeller Noise in Flight and in a Wind Tunnel, NASA-TM [16] A. Zinoviev, Application of Ffowcs Williams and Hawkings Equation to Sound Radiation by Vibrating Solid Objects in a Viscous Fluid: Inconsistencies and the Correct Solution, ISBN @2002 AAS 28 Slide 28

29 Propeller in the Presence of Generic Wing Click to edit Master title style Propeller generates noise Airfoil generates noise Propeller + Airfoil = more noise??? 29 Slide 29

30 SR-2 + NACA0010 : Analysis Click to edit Master title style Comparison with and without NACA10 wing (using direct measurement) SR-2 SR-2 + NACA10 Addition of NACA10 wing Slightly reduced db at probe 5-6 Reduced db from probe 3 to 11 Increased db at Probe 1,2, 12 Propeller + Airfoil = less noise?!? drop of 0.66dB perhaps only at the BPF??? 30 Slide 30

31 SR-2 + NACA0010 : Analysis Click to edit Master title style Comparison with and without NACA10 wing (using direct measurement) SR-2 SR-2 + NACA10 Addition of NACA10 wing Slightly reduced db at probe 5-6 Reduced db from probe 3 to 11 Increased db at Probe 1,2, 12 Propeller + Airfoil = generally lesser noise at probes near to propeller! why??? 31 Slide 31

32 SR-2 + NACA0010 : Analysis Click to edit Master title style Pressure coefficient contour plots Sections of blades coloured blue shows area of suction Areas coloured red shows high pressure stagnation Presence of wing causes significant reduction in rotation (swirl velocity) [17] Viewing from front, the propeller is rotating clockwise angle of angle, leading to higher lift force Viewing from front, wing to the left of propeller experienced positive local Viewing from front, wing to the right of propeller experienced negative local angle of attack, leading to lower lift force [17] L.L.M. Veldhuis, Propeller Wing Aerodynamic Interference, Delft University of Technology. 32 Slide 32

33 SR-2 + NACA0010 : Analysis Click to edit Master title style SR-2 SR-2 + NACA Slide 33

34 SR-2 + NACA0010 : Analysis Click to edit Master title style SR-2 SR-2 + NACA10 [18] M.M. Hand, Unsteady Aerodynamics Experiment Phase VI: Wind Tunnel Test Configurations and Available Data Campaigns, NREL/TP Slide 34

35 SR-2 + NACA0010 : Analysis Click to edit Master title style [19] R.T. Johnston, J.P. Sullivan, Unsteady Wing Surface Pressures in the Wake of a Propeller, Journal of Aircraft Vol. 30, No. 5. [20] A.D. Thom, Analysis of Vortex-Lifting Surface Interactions, University of Glasgow. 35 Slide 35

36 SR-2 + NACA0010 : Analysis Click to edit Master title style Outwards spanwise flow Inwards spanwise flow Y = -R +2cm Local deformation of propeller tip vortex at wing leading edge [19][20] As vortex approaches wing, it will be displaced outwards from the turbine sting Bending around the leading edge, vortex moves inwards towards sting Vortex leaves trailing edge at different span locations and time, resulting in shearing of propeller wake Y = -R Y = -R -2cm [19] R.T. Johnston, J.P. Sullivan, Unsteady Wing Surface Pressures in the Wake of a Propeller, Journal of Aircraft Vol. 30, No. 5. [20] A.D. Thom, Analysis of Vortex-Lifting Surface Interactions, University of Glasgow. 36 Slide 36

37 SR-2 + NACA0010 : Analysis Click to edit Master title style Acoustic field measurements carried out in the framework of the European SIROCCO project found that all the array results reveal that besides a minor source at the rotor hub, practically all noise (emitted to the ground) is produced during the downward movement of the blades [21] [21] S.Oerlemans, P.Sijtsma, B.M. López, Location and quantification of noise sources on a wind turbine, Journal of Sound and Vibration Slide 37

38 SR-2 + NACA0010 : Analysis Click to edit Master title style Acoustic plate located above propeller propeller rotating clockwise (view from front) Upward stroke of propeller blades at region left of spinner (view from front) liable for noise detected by probes on acoustic plate Proximity of airfoil wing to the propeller plane affecting the air flow in the vicinity of the propeller Presence of wing near the propeller may have shielded some of the propeller acoustic effect recorded on probe 4 to 11 Probe 12, located further down the airfoil chord, detected a higher noise Perhaps a higher noise contribution from airfoil further downstream of Probe 12? Literature review on the aeroacoustics impact of tractor configuration with varied test conditions returned ambiguous findings [22][23] [22] P.J.W. Block, Experimental Study of the Effects of Installation on single- and Counter- Rotation Propeller Noise, NASA-TP [23] R.P. Woodward, Measured Noise of a Scale Model High Speed Propeller at Simulated Takeoff/Approach Conditions, NASA-TM Slide 38

39 Click to edit Master title style Summary Aeroacoustics simulation of the SR-2 with updated geometries detected noise at a closer fit to the experimental data, registering a difference of 1.173dB at probe 6 One has to recognize that pre-processing is of utmost importance, especially if one intends Second to invest level in DES or LES Whenever possible, usage of better geometry CAD representation is recommended Appropriate modelling of propeller with MRF or rigid body motion (sliding mesh) is vital Direct measurement of probe points and acoustic analogy serve different purposes Direct measurement for near field probe points are highly recommended if the probe points are located within the simulation domain Acoustic analogy is an effective method to reduce aeroacoustics sound sources to simple emitter type for detection in the far field Noise (emitted to ground) is produced during downward stroke of propeller blades [21] DES simulation of a generic wing aft of the SR-2 propeller at Mach 0.6 had reduced the noise level recorded on most of the probe points in the near field Literature review on the aeroacoustics impact of tractor configuration with varied test conditions returned ambiguous findings [22][23] Scientific research findings can be vague at times One has to keep an open mind and continue one s research 39 Slide 39

40 Click to edit Master title style Thank you 40 Slide 40