Completed Projects

The National Research and Development Institute for Gas Turbines COMOTI has been part of a European research program within the Framework Program 7, aimed at identifying the exhaust noise of a helicopter engine, in order to allow focusing future research efforts on the most significant noise sources.

The project, called "Turboshaft Engine Exhaust Noise Identification", acronym TEENI, involved 11 partners, from 10 European countries, as follows:

  • TURBOMECA SA (France) - COORDINATOR

  • DEUTSCHES ZENTRUM FUER LUFT - UND RAUMFAHRT EV (Germany)

  • ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE (Switzerland)

  • INSTITUTUL NATIONAL DE CERCETARE-DEZVOLTARE TURBOMOTOARE-COMOTI (Romania)

  • ANOTEC CONSULTING SL (Spain)

  • OFFICE NATIONAL D'ETUDES ET DE RECHERCHES AEROSPATIALES (France)

  • THE PROVOST, FELLOWS, FOUNDATION SCHOLARS & THE OTHER MEMBERS OF BOARD OF THE COLLEGE OF THE HOLY & UNDIVIDED TRINITY OF QUEEN ELIZABETH NEAR DUBLIN (Ireland)

  • AVIO S.P.A (Italy)

  • BRUEL & KJAER SOUND & VIBRATION MEASUREMENT A/S (Denmark)

  • INASCO - INTEGRATED AEROSPACE SCIENCES CORPORATION O.E. (Greece)

  • MICROFLOWN TECHNOLOGIES BV (The Netherlands)

It is well known that helicopters can generate a large amount of external noise, as their traditional missions –rescue, medical, law enforcement– are very close to populated areas. As emphasised in ACARE SRA2, increasing rotorcraft missions in the public vicinity should not lead to increasing public disturbance. Turboshaft engine is known as a major contributor to exterior noise for take-off conditions. ACARE SRA2 objectives imply that noise reduction must be maximised for the most dominant engine noise source in flight. An increased knowledge of the exhaust sound sources balance is then required. Broadband noise at a turboshaft exhaust is assumed to be a mix between combustion and turbine noise. TEENI (Turboshaft Engine Exhaust Noise Identification) will find the relationship between engine modules (combustion chamber, HP Turbine, Power Turbine) and their broadband noise signature and will give a recommendation about the noise source to be reduced in priority. But noise sources breakdown is an ambitious goal, due to the complexity of the physics involved, the harsh environmental conditions, and the small space available. TEENI carried out, in parallel, 4 objectives:

  1. To develop sensors for fluctuating quantities, adapted to such an environment;

  2. To develop noise sources breakdown methods;

  3. To understand broadband noise generation and propagation through blade rows;

  4. To discriminate engine exhaust noise sources.

TEENI’s work plan included:

  • Innovative sensors development,

  • New noise sources breakdown techniques,

  • Basic studies, including rig experiments, to understand the propagation effects of broadband noise through blade rows. These tests will also help to verify noise breakdown techniques.

  • New instrumentation and source breakdown techniques will be applied to a full-scale engine test - Development in HELENA (from Friendcopter) of the source breakdown capability

  • Estimation with HELENA of the engine noise source to be reduced in priority in flight

COMOTI's role in the project was to test part of the acoustic sensors, developed by DLR and INASCO in order to verify their integrity during their operation in a harsh environment, such as that in the hot regions of a turboshaft engine, and to design and manufacture the engine adaptation parts required to install the project developed sensors on a real engine, for the final testing session of the project.

Both tasks were successfully completed. A model and an actual photo of the test rig used for sensor testing is presented in Figures 1 and, respectively, 2, and a model of a new exhaust nozzle, designed and manufactured at COMOTI to replace the existing Turbomeca turboshaft engine nozzle, and to accommodate the newly developed sensors is shown in Figure 2.

Figure 1
Figure 2
Figure 3