The ERACLE project is aimed to perform a WT test campaign to measure the near-field and far-field acoustic propagation of a pushing and wing mounted propeller-based propulsion.

The configuration is parameterized w.r.t. propeller design features, installation configurations, and different kind of aerodynamic flows generated by the wing through controlled boundary layers. The projects aims to collect and post-process WT test data, as well as to further develop/ validate a fast engineering toolset for the preliminary design of propeller-wing arrangements vs. acoustic performance.

It is well known that pushing propellers are critical from an acoustic point of view. Actually, in this context, installation effects play an important role.

Two main types of installation effects can be discerned: aerodynamic installation effects leading to modification of the aerodynamics of the pushing propeller by the aircraft body and wing. Indeed, noise emissions result from the impingement of the turbulent wake shed from the upstream wing and nacelle onto the leading edge of the propeller blades and from the ingestion of turbulence from various sources (atmospheric, wing boundary layer, etc.); and acoustic installation effects due to noise reflection and refraction on the aircraft.

However, apart from possible drawbacks in terms of acoustic performance, there is one thing in favour of the pusher configuration which needs a better evaluation: a pusher propeller picks up airflow that is already decelerated by the wing and fuselage to generate thrust, while a puller propeller picks up undisturbed air to blow it onto the fuselage and wings, which in turn decelerate the airflow. This difference means that a pusher propeller may be more efficient at higher speeds.

Different prototypes of twin pusher were developed in the last decades, some of them entered into service (Piaggio P180 Avanti), and the experience with that airplanes points in this direction.

The ERACLE consortium will design, manufacture and integrate a 2D wing equipped with a boundary layer suction & blowing system; new sets of propeller blades, hub, spinner, fairings, shaft and suitable mechanism(s) for varying the propeller installation configuration; and a complete HW/ SW system comprehensive of an electrical motor to drive the propeller(s).

Boundary layer velocity profiles will be evaluated and subsequently characterized experimentally by means of a suitable pressure probe rake. This implies dedicated studies for the WT instrumentation setup definition being carried out by ERACLE partners.

As a further step of the project activities, a WT test campaign aimed at characterizing near- and far-field noise produced by different propeller design and installation configurations has been planned in the acoustic large low speed wind tunnel of Pininfarina, subcontractor of ERACLE for WT test services. During acoustic tests, the consortium will perform acoustic characterization by means of near/far field measurements. WT test data collection and post-processing conclude the WT test campaign.

The final phase of the project is the further development and final validation of an existing toolset provided by the topic leader (the industrial partner, Airbus Defence & Space) and devoted to the preliminary design of novel turbo-prop wing/ engine/ propeller arrangements with a special focus on acoustic performance. Wing wake-propeller interactions will be studied in depth with respect to the nature of the boundary layer and the relative distance of wing and propeller(s), namely flow conditions and engine installation.

This kind of effects are still very complex in their nature and therefore very challenging to simulate using numerical analysis. Indeed, within ERACLE, all these effects will be characterized though dedicated WT tests, and will be used to feed the further development of a fast toolset to pre-design wing-engine-propeller configurations towards a better acoustic performance.

The following partners are part of ERACLE:

  • NHOE for WT model systems design leader
  • UNIROMA3 for Acoustic pre-design toolset and WT test campaign management
  • Eligio Refraschini (ERF) for WT model manufacturing, instrumentation and implementation into the WT
  • IBK for Coordination/ WT model design leader

ERACLE has a duration of 24 months and started 01.07.2018

The ERACLE project has received funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 687015.