TURNEX - Turbomachinery Noise Radiation through the Engine Exhaust
Overview
Background & policy context:
Research is needed to develop innovative concepts and enabling technologies to reduce aero engine noise at the source. Turbomachinery noise radiating from the bypass and core nozzles is a 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 addressed 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.
Objectives:
The goal of TURNEX was to develop concepts and enabling technologies for reduction of engine noise at the source through an improved understanding, modelling and prediction of fan and turbine noise radiation from exhaust nozzles, and through the evaluation of a number of low-noise exhaust nozzle configurations. To achieve that goal, TURNEX had four focussed, ambitious objectives:
- To test experimentally at model scale:
- innovative noise reduction concepts, including a scarfed exhaust nozzle, and
- conventional engine exhaust configurations. The experiments were carried out to develop and utilise novel simulated turbomachinery noise sources and innovative measurement techniques in order to evaluate the noise reduction concepts and to provide a high quality validation database.
- 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, to address specific shortcomings associated with such methods, and to validate those methods with the experimental data.
- To conduct a parametric study of real geometry/flow effects (pylons, wings, flow-asymmetry) and noise reduction concepts (scarfed nozzles, acoustically lined after- body and wing) as applied to current and future aircraft configurations of interest, aimed at achieving a 2-3dB source noise reduction.
- To assess technically 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, in order to enhance the capability of European fan noise test facilities to investigate and simulate fan noise radiation through the exhaust.
Methodology:
The project work was organised into three Work Packages encompassing the following tasks and methods:
Work Package 1: Turbomachinery noise radiation experiments on an engine exhaust rig in a Jet Noise Test Facility. The main objective was to test at model scale:
- innovative noise reduction concepts, including a scarfed exhaust nozzle, and
- conventional engine exhaust configurations.
The experiments developed and utilised 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 was 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 was 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 was 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.
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