Contra-Rotating Open Rotor: towards the futur of flight propulsion

In the current economical and environmental context, efficiency and cost of aeroengines have become a major issue for airframers as well as engine manufacturers. One way to achieve such improvements is the counter rotating open rotor (CROR) architecture, also referred to as propfan, which consists of two propellers rotating in opposite directions, mounted on the aft part of a turbo engine.

This kind of configuration raises challenges in terms of aerodynamics, aeroacoustics and structural dynamics. Indeed, the two propellers are positioned very close to each other, hence in strong rotor/rotor interaction, which makes unsteady aerodynamics predictions mandatory. Furthermore, due to the absence of shroud, noise is an important issue for passengers and community confort. Finally, for obvious safety reasons, the structural integrity of the powerplant is a crucial problem.

In this context, the CERFACS is setting up a computational study of CROR based on several levels of modeling. The basic step is the assessment of the mixing plan approach, which will be further compared to full 360° unsteady simulations. Then, a single-passage modeling based on phase-lag boundary conditions will be evaluated. It is also planned to tackle the problem with an harmonic balance technique. The CFD approach will be coupled with a Ffowcs-Williams & Hawking acoustic approach to evaluate noise. Eventually, the structural aspect will be included by the mean of forced motion simulations.

Contacts: Guillaume Dufour, Jean-Fancois Boussuge