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TURNEX
Turbomachinery Noise Radiation through the Engine Exhaust

Background

Research is needed to develop innovative concepts and enabling technologies to reduce aeroengine noise at its source. Turbomachinery noise radiating from the bypass and core nozzles is becoming the dominant noise source on modern aircraft, but, while recent EU research programmes have made significant progress in reducing both the generation of turbomachinery noise and the radiation of noise from the intake, little work has been conducted on reducing the radiation of turbomachinery noise from exhaust nozzles. TURNEX will address this shortfall by delivering improved understanding and validated design methods, and by evaluating a number of low-noise exhaust nozzle configurations aimed at a source noise reduction of 2-3dB.

Project objectives

1. To test, through experiments at model scale, innovative noise reduction concepts and conventional engine exhaust configurations, which utilise novel simulated turbomachinery noise sources and innovative measurement techniques.

2. To improve computational prediction methods for turbomachinery noise radiation through the engine exhaust, and to validate these methods with experimental data.

3. To conduct a parametric study of real geometry/flow effects and noise reduction concepts as applied to current and future aircraft configurations.

4. To assess the relative technical merits of different approaches to testing fan rigs in European noise facilities.

Description of the work

Work Package 1: Turbomachinery noise radiation experiments on an engine exhaust rig in a Jet Noise Test Facility. The main objective is to test at model scale (a) innovative noise reduction concepts, including a scarfed exhaust nozzle, and (b) conventional engine exhaust configurations. The experiments will develop and utilise simulated turbomachinery noise sources and innovative measurement techniques in order to realistically evaluate the noise reduction concepts and to provide a high quality validation database. A secondary objective is to technically assess the relative merits of different methods of estimating far-field noise levels from in-duct and near-field noise measurements, using both models and the validation data, to enhance the capability of European fan noise test facilities to simulate fan noise radiation through the exhaust.

Work Package: 2 Improved Models and Prediction Methods. The objective is to improve models and prediction methods for turbomachinery noise radiation through the engine exhaust, to a level comparable with that being achieved for intake radiation, and validate these with the experimental data.

Work Package: 3 Assessment and Industrial Implementation of Results. The objective is to conduct a parametric study of real geometry/flow effects (pylons, flow-asymmetry) and noise reduction concepts (scarfed nozzles, acoustically lined after-body) as applied to current and future aircraft configurations of interest.

Expected results

TURNEX will deliver validated industry-exploitable methods for predicting turbomachinery noise radiation through exhaust nozzles, allowing European industry to leapfrog NASA-funded technology developments in the US. It will also deliver a technical assessment on the way forward for European fan noise testing facilities and an assessment of exhaust nozzle concepts for noise reduction at source.

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