ROSAS Final Meeting: Overview of achievements

3rd March 2005

ROSAS Final MeetingMain Achievements

ROSAS

Presented by

Eric MAURYAIRBUS Engineering – Future Projects

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WP1 Definition of Silent Aircraft concepts (1/2)

• Innovative design process toward noise reduction

• OWN & RFN configurations defined including reference engine and nacelle

Noise-shielding efficiency

Handling qualities (stability)

Engine installation

aerodynamic efficiency

Engine installation structure

Thermal interaction with

empennage / wing

RFN / OWN Configuration

Main driver

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WP1 Definition of Silent Aircraft concepts (2/2)

• Engine definition including acoustic data base

Thrust Class (0/0,25/ISA+15K Thrust*1,275) 44,2kArchitecture 1+4+6+0+1+4Fan 85.5 inExhaust SDSFCruise 35kft/0.8/ISA/0hp/No Air/0.998 intake BPR 10

• Impact of new engine installation analysed (preliminary)

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WP2 Aerodynamic Investigations (1/2)

• CAD Model shape design & identification of critical phenomena

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WP2 Aerodynamic Investigations (2/2)

•Initial RFN configuration shows ̃ 25% drag increase,small flow separation

• Initial OWN configuration shows ̃ 90% drag increase,strong flow separation

• Redesign was successful for RFN

• No acceptable OWN redesign possible

• Low speed:- RFN does not show critical effectsRFN does not show critical effects- OWN again shows strong flow separation

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WP3 Acoustic characterization (1/3)

• Successful WTT campaign performed in ONERA CEPRA 19 facility (Jet and Fan noise )

• Unique experimental data base now available in Europe on installation/shielding effect of engine noise sources by airframe surface

• Results started to be exploited and used to derive noise reduction potential for RFN & OWN platform as proposed in ROSAS

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WP3 Acoustic characterization (2/3)

• Turbulent jet noise prediction based on FfowcsWilliams and Hawkings analogy (NLR)

4Acoustic sources distribution ( two-point correlations) scaled in using RANS data (WP2 provided - ENFLOW).

• Assessment of flow inhomogeneities effect on installed engine noise (DLR)

4Application of an existing CAA code (PIANO) on numerical simulation of inviscidperturbations of a pre-computed RANS

4mean flow (WP2 provided).

• Fuselage, wing and empennage shielding effects assessment using BEM (ONERA)

4Extension towards the high frequency (1st

BPF) of an improved method (BEMUSE)4comparison with analytical methods (task 3.2).

30

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100 1000 10000 100000

f [Hz]

SP

L [

dB

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Spectrum at 90°

Shieldingclean & HL airfoil, directscattering

RAIN (CEPRA19), RAIN (CEPRA19), VjVj = 235 m/s= 235 m/s

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WP3 Acoustic characterization (3/3)

RR• Wave theory • Semi-empirical ray theory method

AI-F (semi-empirical methods)Ø Shielding by lifting surfacesØ Shielding by cylinders

TCD (Modelling&Numerical methods)• full field Wave Envelope Method (2D

flyover simulations, 3D empennage –iterative)

• Boundary Integral Method (3D Iterative)• Jet Source Modelling (Equivalent

source )

IST (Theoretical methods)3 Methods : 3 Methods : FresnelFresnel Theory 2D and 3D, Theory 2D and 3D,

Simultaneous shielding and reflectionSimultaneous shielding and reflection

TCD, IST and DLR methods well benchmarked

Z

Shadow zone

Microphone

X

A

Point source

Observer in far field

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WP4 Assessment of Silent Aircraft(1/3)

• Preliminary assessment of RFN & OWN aircraft performances (not optimised aircraft!) with weight, Aero and handling qualities estimates

• OWN is aerodynamically challenging; RFN is less but weight needs to be carefully addressed

vs.RFN

RFN

UWN

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WP4 Assessment of Silent Aircraft(2/3)

Noise reduction potential• OWN concept acoustic reductions are limited due to aircraft performance

issues43.5 EPNdB cumulative reduction, average of RR, SN and A-F

results– 7.8 EPNdB maximum reduction

• RFN shows similar shielding to OWN and similar aircraft performance to UWN leading to the largest noise reductions 46 EPNdB cumulative reduction, average of RR, SN and AI-F results

– 9.7 EPNdB maximum reduction

• RFN has opportunities for further significant acoustic optimisation4 fuselage and empennage shaping4wing positioning4matching of shielding surfaces to source directivities4 reduced airframe noise4engine noise source balance

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WP4 Assessment of Silent Aircraft(3/3)

Recommendations for further investigations

• Shielding of engine noise sources using airframe is a possible efficient option to reduce aircraft noise (between up to 7 EPNdB reduction)

• Supportive ROSAS platform i.e. OWN & RFN concepts have similar noise reduction potential (with advantage to RFN)

• However, preliminary performance assessment shows more potentialfor the RFN concept than the OWN

• A number of issues related to the RFN concept (detailed acousticinstallation effect, aerodynamics performance, maintainability,..) need to be addressed to get a fair overall aircraft balance

• This is proposed within the NACRE FP6 projectNACRENACRENACRE

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Thank you!

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