This proposal describes a methodology to be used for efficient optimisation aimed at drag reduction of some components of a tiltrotor fuselage, i.e. nose, wing/fuselage junction, sponsons and tail surfaces. Specific objectives of such activity are to:
- set up a comprehensive and automatic design tool, integrating the software in use at the GRC Consortium and an in-house optimiser already developed by the applicants;
- implement efficient and robust optimisation strategies for obtainment of optimal geometries using reasonable computing time;
- implement, test and run such tool within the industrial design procedure currently available at the GRC Consortium;
- apply such tool for drag reduction of the above mentioned components in order to improve the overall aircraft aerodynamic efficiency, while guaranteeing compliance with industrial constraints and needs.
Objectives 1 and 3 will be achieved by means of a dedicated programming activity where the software tools will be integrated together and with the proprietary optimisation tool by the applicants. This will result in a procedure where geometrical and grid manipulation, as well as CFD analyses will form an automatic loop.
Objective 2 will be guaranteed by the capability of the optimiser to handle complex multiobjective problems; the optimisation chain will be conceived in such a way that the user can interact with the optimiser and monitor the whole process as it takes place.
Objective 4 will be pursued mainly by means of shape modifications for drag reduction, but, due to the product oriented character of this activity, also complementary techniques (i.e. riblets, vortex generators, Hybrid Laminar Flow Control, gaster bump, sweeping jets, winglets, wing strakes, upper surface spoilers) may be considered and discussed with the leading industry, if a pure numerical shape optimisation would lead to unfeasible solutions with respect to industrial constraints.
Paving the path to green tiltrotor designs
EU researchers are helping to develop a methodology in order to design a more environmentally friendly tiltrotor. Improving the aerodynamic design of tiltrotor fuselage and of other components should provide the European aircraft industry with a host of benefits in terms of efficiency and fuel consumption gains.
The green rotorcraft (GRC) is part of the Clean Sky initiative, focusing, amongst other research areas, on optimising the design and active flow control of airframe and other aircraft components. To this end, innovative software tools are required that should operate at reasonable computing times, and that will be fully compliant with manufacturing constraints.
In this context, the 'Contribution to design optimisation of tiltrotor components for drag reduction' (CODE-TILT) project is developing advanced design methodologies aiming to optimise overall tiltrotor efficiency by decreasing the drag force. The objective of this EU-funded project is twofold, namely to identify the optimum geometries that maximise the aerodynamic efficiency, and to evaluate the aerodynamic efficiency of the aircraft in its totality.
Effective aerodynamic design of fuselage components requires the accomplishment of multiple, and often conflicting, objectives in presence of multiple and multi-criteria constraints. The CFD model of the basic tiltrotor fuselage geometry was assessed for various flight conditions and validated against experimental data. In parallel, the set-up of a comprehensive optimisation strategy aimed at improving the efficiency of the tiltrotor fuselage components. This was achieved by means of a proper shape design. Finally, a study was made into the applicability of drag reduction concepts alternative to those related to shape optimisation to the wing/fuselage junction and empennages.
An optimisation tool was applied to the wing-fuselage junction. The geometrical shape optimisation of the wing/fuselage junction, which aimed at increasing the component efficiency, was addressed for a series of operating points. The impact of the rotor inflow on the overall efficiency was taken into account as well.
The optimised configuration of both the fuselage nose and landing gear sponsons was determined. The optimisation of nose and landing gear fairings was focused on the drag reduction of both the considered components. This took into account some constraints on the pilot visibility and aerodynamic moments of the overall tail-off configuration.
The optimised configuration for the empennage surfaces, including both the fin and the horizontal tailplane, was searched for. The main objective to be pursued was the efficiency improvement of the empennage in terms of increased Lift/Drag ratio at the selected design points. This was done while accounting for some constraints on the aerodynamic moments of the overall configuration, in order to guarantee the static stability requirements.
An overall decrease of tiltrotor fuselage drag of 9% is expected. Evaluating the benefits in terms of fuel saving is outside the scope of the project; however, they will be stated within GRC2.