TEENI - Turboshaft Engine Exhaust Noise Identification
Overview
Background & policy context:
TEENI dealt with experimental identification of engine modules' contribution on exhaust Broadband Noise emission. This noise component is the second most dominant noise source of Turboshaft engines, and installing acoustic liners on the exhaust can lead to significant benefits in reducing helicopter noise levels.
Turboshaft exhaust noise consists of a mix of combustion and turbine noise, with very little jet noise. It is representative of what is generally known as core noise on aircraft engines and can help in understanding this complicated subject matter because of its simpler geometry and absence of parasitic noise sources (such as jet and fan noise).
Objectives:
The TEENI work programme was divided into three interdependent Workpackages (WP):
- WP1: Innovative sensors development - to provide reference measurements of fluctuating quantities within the engine under harsh operating conditions;
- WP2: Noise Sources Breakdown Techniques (NSBT) development - to determine the dominant emission location(s) from external measurements. Several techniques were evaluated, both internal and external measurements were carried out, and various formalisms and approaches were considered. Propagation through turbine(s) and tools to help take into account individual engine noise sources were also developed;
- WP3: An Ardiden 1H Turboshaft engine full-scale test - to include and test the developed sensors, to verify (through correlation with internal sensors) and to assess the pertinence of the various NSBT, and to provide an initial example of noise decomposition per module.
In order to reduce development risks, both sensors and methods were tested within their relative WP before the engine test.
Methodology:
TEENI's major deliverables were:
- A set of sensors for measuring unsteady quantities, suitable for full-scale engine testing (650°<T<1000°C);
- A noise breakdown technique selected from a set of methods as a result of comparisons with data from an engine noise database;
- A thorough understanding of noise generation, propagation and radiation through the exhaust;
- A comprehensive full-scale engine test database;
- A ranking of exhaust noise sources, with a recommendation on the noise source to be reduced in priority, through appropriately tuned liners in the exhaust duct.
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