1. 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, / Seeheim

2. 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, / Seeheim

3. 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, / Seeheim

4. 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, / Seeheim

5. 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, / Seeheim

6. 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 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, / Seeheim

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

8. 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 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, / Seeheim

9. 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 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, / Seeheim

10. 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 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, / Seeheim

11. 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 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, / Seeheim

12. 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 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, / Seeheim

13. Influence of engine speed
One-third-octave band spectra.
Slats/flaps 22°/15°, Landing gear up
Airspeed range 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, / Seeheim

14. Influence of engine speed
One-third-octave band spectra.
Slats/flaps 22°/15°, Landing gear up
Airspeed range 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, / Seeheim

15. 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, / Seeheim