NASA Technical Reports Server (NTRS) 20150010401: Prediction of Tone Noise from Open Rotors PDF
Preview NASA Technical Reports Server (NTRS) 20150010401: Prediction of Tone Noise from Open Rotors
National Aeronautics and Space Administration Ed Envia NASA Glenn Research Center osu January 30, 2012 This work has been supported by the Subsonic Fixed Wing (SFW) and Environmentally Responsible Aviation (ERA) Projects. www.nasa.gov Un-ducted Fan (UDF) Model in NASA Wind Tunnel (1985) PW/AIIison 578-DX Engine on MD-80 Aircraft (1989) •!• Open rotors have proven fuel efficiency advantage over conventional turbofans. •!• The feasibility of open rotor technology and its fuel burn advantage were demonstrated in the 1980's. So what is new? 2 Advances in 3D aerodynamic design tools have made possible open rotor systems than can meet the current noise rules while maintaining their fuel burn advantage. The goal is to make them acoustically competitive with the next generation turbofans. 30 NASA Ultra High Bypass Ratio Turbofan N+l Goal Note: Icons·r epresent notional numbers based on published information. Open Rotors Baseline Turbofan G> ·- U) 0 z 0 0 10 20 30 % Fuel Burn Reduction 3 ~----------------------~--~~----~. Approach ........ How is the noise impact quantified? Reference 1 .... Lateral ........................................ .... .... .... Reference ................................ .... ........................ ~ ........ \ ................................ "-450 m .... 2,000 m ........ ~k-(6,562 ft) ~--- (1,476 H) ........................ ................ 6,500 m .... .... .... .... (21 ,325ft) .... I Flyover Lateral Approach - ~~ Aircraft MTOW Certification Certification Certification Noise Level Noise Level Noise Level Flyover Lateral Approach Flyover (with Cutback) I Aircraft Design ~~ Measured Measured Measured Reference Noise Level Noise Level Noise Level J Flyover Lateral Approach - - Noise Margin ~~ Noise Noise Noise Margin Margin Margin Current internationally agreed Certification Rule = "- ~ ~------------- ~------------~ ~ is called Chapter 4. Before entering service, all Cumulative noise (CUM) margin is the ) new aircraft must meet the rule to be certified. sum of the individual margins. 1 = (Airbus 380-842 CUM Margin 16.4 EPNdB) 4 = - ~ •!• Among other diagnostic data, benchmark sideline acoustic measurements were acquired for a scale I model open rotor configuration called F31 A31, which is also referred to as the historical baseline blade set. The open rotor test campaign was a collaborative effort between NASA and GE. Sideline Microphone Traverse Track _____ // ---------i------------- ~ ,~ 60" Flow (M = 0.2) NASA Open Rotor Rig Plan View of the Wind Tunnel Installation '· 5 Measured F31/A31 Sideline Narrowband Acoustic Spectrum at 90° Angle Open rotors have a preponderance of tones in their acoustic spectra. 110 ~~~~~~~~~~==========~~====~~ How is the tone co '"'C spectrum predicted? ·_-6100 tl) 0 Cl) 0 4BPF ~ 1 BPF +3BPF ~ro 2 5r2 1 2 90 ~ ..j...J u Cl) Clot UJ ~ Cl) 80 ~ 0 ~ Cl) ~ ;J tl) 70 C/) Cl) ~ ~ F31 /A31 has a 12-bladed front & aJO-bladed aft rotor. Relevant S. 0. are 12m+ 1O n, m, n integers Shaft Order 6 •!• The fundamental challenge of aeroacoustic modeling . and prediction is the large difference between the aerodynamic and acoustic scales: Aerodynamic I 0(1) P Pamb. --- I Acoustic p 0(1 1 Pamb. --- Q-3, Q-6) •!• As an example, GE-90 produces roughly 25 MW of aerodynamic power at the takeoff condition while producing less than 1 KW of radiated acoustic power at the same condition. 7 •!• This difference necessitates the development of specialized modeling techniques to adequately resolve the acoustic perturbations. This is most often done by separating the two scales through linearization of the equations of motion~ •!• In linearized methods, the mean flow and some aspects of the source description (e.g., amplitude, length/time scales, etc.) are specified, measured, or computed a priori and are introduced as boundary conditions or source terms in the equations governing the acoustics. CFD is most often used for that purpose. 8 ------------. NASA Tool Box of Aircraft Noise Prediction Codes Geometry, Flight Path APET, RNM RNM, ANOPP & Operating Conditions ANOPP (Modules), V072, RSI, LINFLUX, LINPROP, QPROP, ASSPIN, CRPFAN, ... ponent Source Atmospheric Propagation Community Noise iction -~ & Terrain Modeling Prediction Airframe Scattering & Shielding Prediction ____ .__ Cabin Noise ~ Prediction 9 --------------------------------------------------------------------------------------- Geometry, Op. Conditions r--------- ------------- -------------------- Acoustic Analogy, Linearized Methods Empirical Linearized Comp. Direct Num. Sim. Noise Models Noise Models LES, VLES, DNS Noise Spectra ~~~~ ~~~ I I I -------------------~~~~~~~~~~-~-~-:-~~~~~~~-~----~-~~~~~::::::::-~-~-------------------lll-~
The list of books you might like
