Large scale wind tunnel turboprop aircraft model integrating morphing devices for aerodynamic experimental assessment

Project Information

WTM-RECYCLE

Grant agreement ID: 755605

DOI

10.3030/755605

Project closed

EC signature date 7 July 2017

Start date 1 September 2017

End date 31 July 2021

Funded under

• SOCIETAL CHALLENGES - Smart, Green And Integrated Transport

Total cost

€ 1 534 250,00

EU contribution

€ 1 295 875,00

Coordinated by

KUNGLIGA TEKNISKA HOEGSKOLAN
Sweden

Periodic Reporting for period 2 - WTM-RECYCLE (Large scale wind tunnel turboprop aircraft model integrating morphing devices for aerodynamic experimental assessment)

Reporting period: 2018-12-01 to 2021-07-31

Summary of the context and overall objectives of the project

Existing turboprop configurations are very efficient at cruise speeds up to about Mach 0.65 providing a fuel savings of 10 to 20 percent with respect to equivalent technology turbofan aircrafts. On the other hand, above this speed, the increased drag due to compressibility losses on the propeller blades causes efficiency to fall rapidly. Now, with the use of composite materials and advanced construction techniques, it is possible to construct propeller blades with thinner airfoil sections and more optimum shapes (sweeping the blade leading edge, scimitar geometry, etc) that can operate in high subsonic conditions (up to M=0.8). The integration of turboprop engines into the airframe, and the design of high-lift devices for landing and take-off, presenting some unique aerodynamic challenges in particular when utilizing natural laminar flow wings for additional drag reduction.

Regional mobility is of fundamental importance for regional economic and social development by connecting countries, people and cultures. Here, regional air transportation is of crucial importance by integrating with the global network of air transportation. In this respect, novel turboprop designs will contribute to environmentally friendly and sustainable means of transportation.

WTM-RECYCLE – Large scale wind tunnel turboprop aircraft model integrating morphing devices for aerodynamic experimental assessment – addresses the call JTI-CS2-2016-CFP04-REG-01-05 and contributed to the knowledge base and technical development for sustainable regional air transportation. The overall objective of the project was to support the development and assessment of new and conceptual versatile aerodynamic control surfaces, and high lift technologies as well as turboprop integration effects. The WTM-RECYCLE project focused on the Upgrade of an existing wind tunnel model for delivering aerodynamic data that allows analyzing the aerodynamic performance of innovative control surfaces and high-lift devices including powered propellers. In specific, the objective was to study the effect of morphing devices for drooped wing leading edge, geometry morphed flaps and winglets in landing and take-off configurations including propeller installation effects. The main outcomes are detailed wind-tunnel measurements as well as complementary numerical CFD analyses for studying the flow details and scaling to real conditions.

An existing wind-tunnel model was redesigned, with the aim of maximizing the use of the existing hardware with consequent reduction of new components and therefore reducing waste production, energy consumption and pollutions emissions within the project itself. A large-scale demonstrator was designed and build in an upfront project. Using it here effectively halved the resources needed to generate high-value results and significantly de-risked the WT campaign.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The geometrical design of the wind-tunnel model was performed in the first project phase. The original plan was extended by introducing exchangeable wing geometries in order to fully take advantage of outcome from parallel activities on the design of natural laminar wing. This required a careful redesign of the wind tunnel model due to the complex design of the inboard wing core structure which carries the hydraulic high-pressure connections. This has been achieved in a way that a fast exchange in the wind tunnel between both wing geometries is ensured. The desired droop nose was implemented by interchangeable wing leading-edge elements.

The old LOSITA wind tunnel model was restored and reused considering the fuselage, tail and outer wings. Existing pressure taps have been verified and tested. New parts were manufactured mainly related to the new design including the internal core with complex hydraulic routings, the interchangeable wing cowers with pressure taps as well as updated control surfaces with flap balances. All configurations were assembled and checked including detailed laser measurements before shipping to RUAG.

A modularized and parametric meshing procedure was designed in order to enable fast and automatic CFD analysis for WT comparisons and extrapolation to free flight. The surface mesh was virtually structured on the critical regions for highest possible accuracy, convergence as well as efficient high-performance computing. The CFD analysis included the full geometry because of asymmetry due to the co-rotating propeller installation, which was included in the CFD model by a propeller disk model.

The test campaign in RUAG's Large Wind Tunnel Emmen (LWTE) was successful for producing aerodynamic forces and moments as well as surface pressure distributions over the wings and tail. The two different wing designs were tested in cruise, landing and take-off configurations. The effects of deflected control surfaces like ailerons, spoilers, rudder and elevator were assessed with and without thrusting propellers. Moreover, tail-off effects, lift hysteresis and surface friction patterns were derived. In total more than 400 polars were measured. CFD analyses show in general good comparison with measurements for all six configurations. In addition, as complement to the measurements, CFD analyses were made for establishing the wind-tunnel installation effects and for extrapolation to full-scale conditions. Moreover, the influence of boundary-layer transition to turbulence was concluded from perturbation instability analysis. In total around 500 CFD analyses were made.

The aerodynamic database, in terms of wind-tunnel and CFD data, has been delivered to the PM Leonardo and the CleanSky2-REG IADP giving valuable input for the design of high-lift devices enabling natural laminar wing technology for reduced environmental impact from regional air transportation. Moreover, the challenges in testing two different wing designs forced us to invent new methods for designing and manufacturing of modularised WT models including instrumentation. The same concept was used for the CFD model as well when designing and generating the computational mesh, which has been communicated and disseminated at international conferences. These methodologies will be utilised in further studies by the involved partners.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The core activity was to achieve an aerodynamic database of the innovative turboprop aircraft model integrating innovative leading-edge and trailing-edge high-lift devices for enabling natural laminar wing technology. This was achieved by performing a large-scale wind-tunnel tests in 2021, which completed the assessment of the GRA turboprop aircraft configuration by providing relevant data about the effectiveness of such promising high lift morphing concepts. The related CFD analyses provided important additional information about the scaling to free-flight conditions as well as details about the flow.

The Clean Sky program aims to develop innovative and environmentally friendly products. The knowledge derived from the wind tunnel test and CFD study in this project will help to validate the work done within the Clean Sky REG-ITD and to develop future innovative solutions. Morphing is a key technology for laminar wing technology which, applied for the present regional aircraft, has an estimated benefit of around 7% increase in L/D resulting in approximately 3% fuel saving. A large-scale demonstrator such as the WTM-RECYCLE model has now demonstrated the benefits that can be obtained and therefore push the work of the ITD.

cfd.png

windtunnel.png