Source Modelling I: Engine Noise Ulf Michel and Sébastien Guerin German Aerospace Center (DLR) Institute of Propulsion Technology Turbulence Research Section Berlin MIT / DLR / DLH Workshop on Noise Abatement Procedures 17 – 19 August 2004, Seeheim / Germany MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Research Project LAnAb Objectives of Research Project LAnAb: Determine quiet departure and approach procedures for modern aircraft like the A320 series aircraft. Optimization performed with numerical methods based on experimental data. Two contributions to flyover noise: Engine noise Airframe noise MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Sub-project “Source Modelling” Objectives of sub-project Development of noise source models for installed engines and airframe components for all aircraft configurations used during approaches and departures. Source models developed with the aid of dedicated flyover noise tests with a Lufthansa A319 (equipped with CFM56-5A engines). (Tests with a Lufthansa MD11 performed outside project LAnAb). Results of A319 will be valid for A320 series. Applicability of results to other aircraft must be investigated later. MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Analysis of Flyover Noise Data with respect to Engine Noise Noise emission of the engines of a specific aircraft depends on Engine speed Flight speed Emission angle (defined relative flight direction perpendicular to the flight direction) Aircraft mass (angle of incidence) Flap setting (installation effects) Goal is description of one-third-octave band levels in terms of these parameters. MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Analysis of Flyover Noise Data with respect to Engine Noise Test matrix was defined to include approaches and departures with different engine speeds, different airspeeds, and different flap settings. Some 120 flyovers recorded. Example: engine speeds for one approach configuration and one airspeed: 30% : flight idle 55% : normal approach engine speed 60% : used for corrective actions 65% : tested to increase range of engine speeds MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

De-dopplerized power-spectral densities, 50 deg Influence of engine speed Power-spectral density (dB/Hz) for distance 120 m Slats/flaps 22°/15°, Landing gear up Airspeed range 88.5 to 90.0 m/s Doppler amplification factor for pressure: 2 Loss-less atmosphere De-dopplerized power-spectral densities, 50 deg MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

De-dopplerized power-spectral densities, 90 deg Influence of engine speed distance 120 m Slats/flaps 22°/15°, Landing gear up Airspeed range 88.5 to 90.0 m/s Loss-less atmosphere De-dopplerized power-spectral densities, 90 deg MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

De-dopplerized one-third-octave spectra, Engine contribution, 50 deg Influence of engine speed Engine noise contribution in flight idle levels will be removed with the help of phased array results Slats/flaps 22°/15°, Landing gear up Airspeed range 88.5 to 90.0 m/s Doppler amplification factor for pressure: 2 Loss-less atmosphere De-dopplerized one-third-octave spectra, Engine contribution, 50 deg MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

De-dopplerized one-third-octave spectra, Engine contribution, 70 deg Influence of engine speed One-third-octave band spectra. Slats/flaps 22°/15°, Landing gear up Airspeed range 88.5 to 90.0 m/s Doppler amplification factor for pressure: 2 Loss-less atmosphere De-dopplerized one-third-octave spectra, Engine contribution, 70 deg MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

De-dopplerized one-third-octave spectra, Engine contribution, 90 deg Influence of engine speed One-third-octave band spectra. Slats/flaps 22°/15°, Landing gear up Airspeed range 88.5 to 90.0 m/s Doppler amplification factor for pressure: 2 Loss-less atmosphere De-dopplerized one-third-octave spectra, Engine contribution, 90 deg MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

De-dopplerized one-third-octave spectra, Engine contribution, 110 deg Influence of engine speed One-third-octave band spectra. Slats/flaps 22°/15°, Landing gear up Airspeed range 88.5 to 90.0 m/s Doppler amplification factor for pressure: 2 Loss-less atmosphere De-dopplerized one-third-octave spectra, Engine contribution, 110 deg MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

De-dopplerized one-third-octave spectra, Engine contribution, 130 deg Influence of engine speed One-third-octave band spectra. Slats/flaps 22°/15°, Landing gear up Airspeed range 88.5 to 90.0 m/s Doppler amplification factor for pressure: 2 Loss-less atmosphere De-dopplerized one-third-octave spectra, Engine contribution, 130 deg MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Influence of engine speed One-third-octave band spectra. Slats/flaps 22°/15°, Landing gear up Airspeed range 88.5 to 90.0 m/s Doppler amplification factor for pressure: 2 Loss-less atmosphere flight idle 55% 60% 65% Difference levels to engine flight idle in comparison to engine flight idle levels, 90 deg MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Influence of engine speed One-third-octave band spectra. Slats/flaps 22°/15°, Landing gear up Airspeed range 88.5 to 90.0 m/s Doppler amplification factor for pressure: 2 Loss-less atmosphere flight idle 55% 60% 65% Difference levels to engine flight idle in comparison to engine flight idle levels, 110 deg MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim

Conclusions Conclusion for contribution of engine Small broadband contribution below 3 kHz expected to be easy to model Large broadband contribution above 3 kHz expected to be easy to model Strong tonal contribution from engine tones probably very difficult to model Goal: Source models with as few constants as possible Precision within the range of measuring accuracy First step: Data base with measured one-third-octave band spectra for all configurations used during landing approach MIT/DLR/DLH-Workshop, 17-19.08.04 / Seeheim