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).
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.
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.
The second dominant noise source of a Turboshaft engine is the noise component of engine modules. Installing acoustic liners on the exhaust can lead to considerable noise benefits on helicopter noise levels. The project suffered from a poor estimation of possible difficulties arising from the implementation of new instrumentation for the engine. As a result, many of the components used for the implementation had to be built from scratch which required the project to be extended from 3 years to 5 years. During the testing phase, the noise reduction components and the newly installed instrumentation proved successful.
TEENI's main deliverables were:
- Pressure and Temperature Probes measuring unsteady quantities, equipped for engine testing (6501400 degrees Celsius), with a bandwidth of more than 4kHz for Pressure Probes and a bandwidth of more than 1 kHz for Thermocouples.
- The first-ever comprehensive full-scale engine test database for this type of testing, with extensive internal measurements and farfield instrumentation.
- Development of a panel of original signal processing methods during the project, which realised noise breakdown by using internal measurements to understand the origin of noise measured in the farfield.
- Elements of understanding noise generation, propagation, and radiation through the exhaust.
Combustion noise was identified at low frequencies; the relative importance of this increasing after the HP Turbine. Broadband noise origin for frequencies above 2kHz were not fully explained.
First database of its kind, made for registering results of testing for broadband noise emission.
Development of new components and instrumentations.
Further testing is needed, but the project was a step towards the development of components and instruments that can reduce broadband noise emissions considerably.
1. Innovating for the future, technology and behaviour: The reduction of broadband noise emissions helps create a better urban environment, as it reduces noise pollution that could be both disturbing and damaging.
2. Modern infrastructure and smart funding: Aviation is a part of modern infrastructure, and as such the project has helped develop tools for improving aviation technology for the benefit of both cargo and passenger transport.