Progress in Aerodynamic and Aeroacoustic Integration of CROR Propulsion Systems

Transcription

1 Chart 1 Progress in Aerodynamic and Aeroacoustic Integration of CROR Propulsion Systems Rinie Akkermans, Olaf Brodersen, Jan Delfs, Arne Stuermer & Jianping Yin DLR Institute of Aerodynamics & Flow Technology Braunschweig, Germany RAeS Propulsion Conference Progress Towards Open Rotor Propulsion Technology November 21 st, 2012 Royal Aeronautical Society London, UK

2 Chart 2 Propeller & DLR-AS - History of experimental & numerical analysis, design & testing of propellers & helicopters - CFD-based propeller analysis experience built up during the past 9 years - Cooperation with Airbus on Single Rotation Propeller-related topics - CESAR: Cost Effective Small AiRcraft (Q4/2006- Q1/2010) - Contribution to Piaggio led Task Environmentally Friendly Propeller Propulsion - Low-noise high efficiency propeller-airframe integration - CROR activities since 2007: Internal research, Airbus contracts (2008-present), Lufo-IV OPERO project with RR ( ), EU-JTI SFWA activities (2008-present)

3 Chart 3 Recent Applications: Internal Research Activities on CROR Installation Effects Arne Stuermer & Dr. Jianping Yin DLR Institute of Aerodynamics & Flow Technology Braunschweig, Germany

4 Chart 4 Research Geometry: Sizing, Nacelle and Pylon - Generic pusher CROR, sized for 150-seat AC: - TO-thrust F x =88kN - Cruise thrust F x design point h=35,000ft - 10-bladed D=4.2672m front rotor, 8-bladed aft rotor with 15% diameter crop - Generic pylon: - Symmetric airfoil, t/c=0.1 - Untwisted for semi-installed case - x/d=0.15 distance to front rotor - Representative performance levels achieved: Cruise Performance of 10F2x8AC1 CROR h=35,000ft; J 1 =3.678, J 2 =4.203 Rotor 1 Rotor 2 Total F x [N] 10,566 8,424 18,990 η [%] Previous systematic configuration studies reported in AIAApapers , ,

5 Chart 5 Aerodynamic Analysis: Installation Impact on Blades - Installation leads to non-uniform inflow for front rotor: - Pylon wake leads to localized increase in AoA - Aircraft incidence angle further distorts rotor inflow Blade effective angle of attack variations - Overlapping impact of blade-blade interactions

6 Chart 6 The Case for Counter-Rotation of Installed Contra- Rotating Open Rotor Propulsion Systems Arne Stuermer & Jianping Yin DLR Institute of Aerodynamics & Flow Technology Braunschweig, Germany From: AIAA th AIAA Applied Aerodynamics Conference June 25th, 2012 New Orleans, LA

7 Chart 7 Introduction & Motivation: Non-Handed CRORs - Asymmetric Aircraft - Most likely engine-airframe integration scenario for empennage-mounted pusher CROR on notional T-tail aircraft configuration: - Same sense of CROR rotor rotation on both sides of the aircraft - Asymmetric aircraft and asymmetric aerodynamic and aeroacoustic CROR performance due to complex installation effects

8 Chart 8 Aerodynamic Analysis: Installation Impact on Blades - Aft blade shows full span unsteady loadings due to front rotor wake impingement - Pylon wake impact induced loading jump for both rotor blades - Aft blade shows tip vortex impingement on upward sweep: Front blades loading increase on downward sweep affects blade wake and tip vortex strength and trajectory α=4º

9 Chart 9 Aerodynamic Analysis: Impact on Front Blades - Spectral analysis of blade loading oscillations shows dominance of pylon wake impingement at rotor rotational frequency of f=n - Clear AoA-driven 1P-loading increases - Clear sense of rotation dependence of 1P loading amplitude - Front rotor DBP sense of rotation: Superposition of pylon wake impingement with AoA-induced loading rise increases overall amplitude of unsteady loading - Critical engine in terms of blade lifetimes - Rotor-rotor interaction: - Blade loading oscillations at even number higher harmonics of aft rotors BPF - Front rotor blades show only small impact of AoA increase

10 Chart 10 Low-Speed Aerodynamics: Rotor 1P-Loads - Non-uniform inflow leads to 1P-loads, an important consideration for structural design & handling qualities - α=4º: Lift-dominated 1P-loads - UBP: 4.01% and 6.76% of front and aft rotor thrust respectively - DBP: 5.60% and 5.56% of front and aft rotor thrust respectively - Lateral and longitudinal trim required - Flight control system handling of dynamic asymmetric 1P-loads during maneuvers

11 Chart 11 Aeroacoustic Analysis: Tools & Approach - Noise radiation analysis using DLR FW-H Code APSIM (Acoustic Prediction System based on Integral Method) for farfield noise predictions - Permeable surface approach used based on nacelle Chimera data: - Analysis for farfield polar microphone 10D from front rotor center - Flyover noise simulation using DLR HEMISPHERE-Code: - Simulation for twin-cror powered aircraft flying at constant speed of M=0.2, constant altitude of h=150m and constant (CROR)-AoA of α=4º over rectangular area of 1200x500m - Comparison of co-rotating CROR (left DBP, right UBP) and counter-rotating UBP CROR installation Perturbation Nearfield CFD APSIM (Blade) Surface Pressure

12 Chart 12 Aeroacoustic Analysis: Farfield Polar Directivities - Farfield polar directivities show CRORcharacteristic flat noise directivities - Rotor tones dominate near planes of rotation - Pylon wake impingement leads to front rotor tone increases in upstream arc - Strong interaction tone contributions in the up- and downstream arc - Higher (front rotor) blade loadings cause for most of the DBP cases noise penalty versus the UBP sense of front rotor rotation - UBP case shows higher upstream front rotor tone levels, possibly due to stronger pylon wake - Acoustically optimum sense of rotation of the (front) rotors with respect to the pylon (here: UBP) for community noise

13 Chart 13 Aeroacoustic Analysis: Flyover Noise Analysis - Flyover noise contours show asymmetry for CROR co-rotation, with amplified secondary noise peaks in sideline direction vs. counterrotating CROR case - Effective Perceived Noise Level accounts for tone peak levels, annoyance as well as duration of exposure to levels near peak, which lead to strong weighting of interaction tones - Aft rotor tone fundamental has lowest frequency and directivities important primarily in plane of rotors - Front rotor tone levels have highest peak levels, higher frequency content but still relatively focused directivities - Interaction tones have high frequency content, relatively high peak levels and flat directivities (long exposure times)

14 Chart 14 Pylon Trailing Edge Blowing for the Control of CROR Unsteady Blade Loads Arne Stuermer & Jianping Yin DLR Institute of Aerodynamics & Flow Technology Braunschweig, Germany From: 17. DGLR-Fach-Symposium der STAB November 9th-10th, 2010 Berlin, Germany

15 Chart 15 Pylon Blowing: Rotor Inflow Distortion -Slot for pylon wake filling along blunt trailing edge 0.5<r/R<1.2, Blowing rate: ~2kg/s -Study for SL, M=0.2, α=0º -Blade settings for equal blade power absorption n 1 =n 2 [rpm] J F J A β 75,F [ ] β 75,A [ ] Isolated CROR inflow dominated by flow acceleration -Installation leads to non-uniform inflow -Blade effective angle of attack variations between -1.5º<α<1.5º -Distinct pylon wake -Pylon TE blowing reduces pylon wake deficit -Close coupling limits available mixing length -Overall inflow distortion remains

16 Chart 16 Pylon Blowing: Installation Impact on Blades - Spectral analysis of blade loading oscillations shows strong effect of pylon blowing: - 1P-loading remains, so marginal impact on fluctuation f=n - All higher harmonic oscillations thereof reduced significantly for front rotor - Exception: Interaction frequency with aft rotor f=2*b A, 4*B A, - Similar differences seen for aft rotor, but some additional higher frequency oscillation induced

17 Chart 17 Pylon Blowing - Aeroacoustic Analysis Tone Contributions - CROR-characteristic flat noise directivities - Rotor tones dominant near planes of rotation - Interaction tones dominate up & downstream - Pylon-wake impact: - Strong increases in front rotor tone levels, especially upstream - Moderate aft rotor tone level increases - Little impact on interaction tones - Blowing impact: - Notable reductions in front rotor tone levels, some aft rotor tone reductions - Benefits of pylon blowing: - Blade fatigue and vibration benefits - Small overall noise reductions but significant amelioration of front rotor tone levels, benefitting overall noise characteristics ( annoyance, EPNdB)

18 Accurate Noise Emission Predictions for Non-Periodic Contra-Rotating Open Rotor Cases Rinie Akkermans, Jan Delfs DLR Institute of Aerodynamics & Flow Technology Braunschweig, Germany From: AIAA th AIAA/CEAS Aeroacoustics Conference Colorado Springs, CO, USA

19 Chart 19 Non-Periodic CROR Noise Analysis: A Challenge for CFD-CAA n F =n A - Unique problems for the numerical analysis of CROR configurations featuring unequal rotor rotational speeds: - Periodic pressure time-histories readily obtainable for equal rotation speed CROR cases - Typical rotor rotational speed ratios for nonperiodic CRORs lead to obtainment of true signal periodicity for unfeasibly long urans simulation times - Simple DFT/windowing of non-periodic urans data a possible source of error in results - DLR-AS Technical Acoustics Department development of correction method in DLR-AS FWH-Code APSIM+: - Relevant frequencies are known a-priori - Simultaneous least-square minimization approach: n F n A

20 Chart 20 CAA Analysis of Non-Periodic CROR Noise: Reconstruction of Artificial Signals DFT without correction With correction - Application of correction approach to artificial signal allows for reconstruction of original time history with an error approaching machine accuracy p p reconstruc ted

21 Chart 21 CAA Analysis of Non-Periodic CROR Noise: Application to WTT Results: Impact on Spectra Rotor plane, near field Upstream, near field - Utilizing the developed method for the numerical analysis of a CROR WTT shows significant corrections of individual tones are necessary versus a straight DFT analysis

22 Chart 22 CAA Analysis of Non-Periodic CROR Noise: Application to WTT Results: Impact on Directivities Without correction: With correction: WTT, isolated CROR WTT, installed CROR CAA, isolated CROR CAA, installed CROR - Use of uncorrected DFT yields CAA directivity results with large discrepencies towards WTT data - Corrections greatly improve correclation between numerics and experiment - Installed case: large influence of corrections on CAA-predictions - Conclusion: DLR-AS FWH-Code APSIM+ applicable to the predicition of arbitrary CROR configuration noise emissions

23 Chart 23 Summary & Conclusions - Broad scope of CFD/CAA investigations have improved understanding of CROR-airframe installation effects - Further extension of multi-disciplinary analysis under way to include blade aeroelasticity - Robust validation of all components in the process chain slated to be completed in the frame of Airbus-led Clean Sky JTI SFWA project

24 Chart 24 Progress in Aerodynamic and Aeroacoustic Integration of CROR Propulsion Systems Rinie Akkermans, Olaf Brodersen, Jan Delfs, Arne Stuermer & Jianping Yin DLR Institute of Aerodynamics & Flow Technology Braunschweig, Germany Thank you for your attention! Questions? RAeS Propulsion Conference Progress Towards Open Rotor Propulsion Technology November 21st, 2012 Royal Aeronautical Society London, UK