HIGH TECH LABS
ACOUSTIC

CROR - COUNTER ROTATIVE OPEN ROTOR

What is the level of interest of aircraft builders in reducing the noise pollution from their machines?

It is critical, because the regulatory framework is growing stricter all the time. The noise level authorised by the International Civil Aviation Organisation has been lowered by 40 decibels in recent decades, even as airplane wingspans and global fleet sizes have continued to increase. This also places pressure on the noise perceived both by residents living near airports and by personnel at these airports.

What does simulation have to offer compared to physical tests?

Simulation significantly reduces testing costs and enables more analysis of innovative configurations: changes in designs, materials, location of engines on the aircraft, etc. It also helps aircraft builders determine the optimal flight conditions. For instance, knowing how to adjust the take-off and landing phases, the pitch settings of high-lift devices and the engine speed in order to reduce the overall noise footprint.

 

What innovations are you working on?

One of the main challenges lies in the evaluation of new engine setups based on the coupling of rotors that turn in opposite directions, known as CROR (Contra-Rotative Open Rotor). These technologies are promising in terms of performance and thus also in reducing fuel consumption. Sources of noise associated with this type of engine setup are complex and still poorly understood, which means the acoustic modelling and analysis work is substantial.


May we discuss the thesis project dedicated to this topic?

In 2013, in partnership with Sogeti High Tech and Airbus Operations, a doctorate student at the "École centrale de Lyon" engineering school took on the task of improving the tool for predicting rotor-rotor interaction lines, at low speeds. The existing tool is limited to noises emitted by the propeller downstream of the impact of the wake generated by the upstream propeller. This noise is known as "wake interaction".

This research project aims to extend the analytic approach developed in the case of pairs installed on aircraft. Influence from installation effects (strut, fuselage, wing surface) is taken into account at each step in the calculation process: viscous wake produced by the upstream propeller, aeroacoustic response of the blade and radiated noise. The plan is to create a second model including the physical mechanisms absent from the initial tool which could complete the description of the interactions between propellers (tip vortices formed at the ends of the upstream propeller blades and potential interaction)."

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Contact
  • Myriam Bouvier
    Myriam Bouvier
    Acoustic Manager
    +33 (0)5 34 46 92 23