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H2020

DECOROUS Report Summary

Project ID: 715796
Funded under: H2020-EU.3.4.5.1.

Periodic Reporting for period 1 - DECOROUS (Design, test, and manufacturing of robust fluidic actuators)

Reporting period: 2016-06-01 to 2017-11-30

Summary of the context and overall objectives of the project

While, for decades, mechanical devices resolved the dilemma of having to cover efficiently for high- and low-speed flight, recent developments in aircraft design have turned up new problems that might require a different solution. Those developments, driven by spiking energy prices, fierce competition and environmental responsibility of the aircraft manufacturers, aim at increasing the aircraft’s fuel efficiency to reduce direct operating costs and the its ecological footprint. In particular, one novel design features conflicts with the local integration of mechanical high-lift devices at the wing’s leading edge: ultra-high-bypass ratio fans (UHBR). The large nacelles of UHBR engines need to be installed close to the wing to provide sufficient ground clearance without increasing the size of the aircraft’s landing gear. In consequence, a slat would collide with the nacelle when deployed, resulting in the need of a slat cut-out, the fraction of the wing’s span above the engine where no slat is installed. This leaves regions of the wing unprotected by a slat and prone to separation at incidence angles much lower than for the remaining sections of the wing. It is in those regions where Active Flow Control (AFC) might be introduced to delay local separation to higher angles of attack and therefore to augment the overall high-lift system.
The aim of flow control is to modify this original state of flow in such a manner that beneficial effects are achieved. Besides the in-depth understanding of the flow physics involved, successful application of active flow control requires the availability of robust, reliable and potent flow control actuators. The project DECOROUS addresses the development of such actuators, namely of a two-stage no-moving-parts fluidic actuator system for use in active flow control applications at the wing-pylon junction of civil airliners. The work is based on the technology researched in the EC-funded projects DT-FA-AFC, FloCoSys, and robustAFC, but goes vastly beyond the scope of those projects by broadening the view to include real-aircraft constraints, considerations from other-than-aerodynamics disciplines, and harsh environment conditions.

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

During the first half of the project DECOROUS the majority of the work focused on the the provision of flow control hardware for cryogenic testing on a realistic half-model wing and the preparation and conduction of this test campaign. The main challenge was to device the core components of a flow control system: a pulsed jet fluidic actuator (PJA) and a steady blowing actuator (SBA) for wind tunnel tests in cryogenic conditions. Both actuator types were manufactured using 3D microprinting from stainless steel powder.
Besides the core actuator components, the flow control system delivered comprises:
• a wing leading edge insert for a specified 3D half-model
• a heating system for pre-heating the fluid used for actuation
• unsteady pressure sensors for health and performance monitoring of the AFC systems
• thermocouples for measuring the fluid temperature in the AFC system plenum
The finalized AFC systems were tested and qualified in bench-top experiments and supplied in-time to project partners for installation on the wing.
Despite the very limited available space for the installation of components, the AFC hardware was successfully integrated, and the AFC inserts were exchanged during the test within the foreseen time frame of one shift. The test campaign was completed successfully.
Lessons learnt from this first small-scale integration attempt, such as challenges with respect to ensuring airtightness and actuator health monitoring, will be exploited towards any further small scale cryogenic wind tunnel tests.

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)

Local active flow control as a tool to amend the high-lift system of civil airliners has increasingly become a focus point of aeronautical industry development. This is underpinned by recent successful flight testing of an active flow control system by the US-American private enterprise Boeing and the continuous research on this topic in EC funded projects such as Clean Sky, AFloNext, and Clean Sky2. The ultimate aim of this research is to enable this technology to contribute to reduce the ecological and socioeconomic impact of air traffic and to increase the competitiveness of the European aeronautical industry including its supply chain. This tool allows to increase eco-efficiency and decrease direct operating costs (DOC), as it enables the designer to force the flow to behave in a manner, which cannot be achieved by purely passive shape optimization. The specific challenge to the present work is to enable the integration UHBR-fans, as the size of those engines will require a novel treatment of the wing-pylon interaction. The installation of UHBR-fans on aircrafts is desirable, as they exhibit higher fuel efficiency and cause lower noise emissions (both resulting in decreased direct operating costs) than concurrent aero-engines. As conventional high-lift systems cannot be used to overcome all hindrances on the way to the integration of UHBR fans, the use of active flow control in the wing-pylon-junction region is expected to impact the integration of UHBR-fans in a technology enabling sense. The core element of any such flow control system is a control actuator: a device, which must provide the control authority necessary to force the flow to behave in a favorable manner, while its integration into an aircraft must be feasible from an economic and legal (certification) point of view. The work of this project will beneficially impact the industrialization of local active flow control by contributing substantially to making such a flow control actuators available on aircraft system level.

While the research in the first Clean Sky program focused on pushing the actuator technology TRL by researching its functionality and scalability (DT-FA-AFC), its integration (FloCoSys), and its robustness (robustAFC), the project DECOROUS will push for higher system readiness levels (SRL), as its multidisciplinary optimization is one major part of the work. In consequence, at the end of this project, an aircraft scale actuator design fulfilling all relevant physical and legal requirements will be available for flight testing – therefore enabling the validation of local active flow control on TRL6.
In addition, the concept of the two-stage fluidic actuator will enable TRL3 wind tunnel tests, i.e. testing in cryogenic conditions, without requiring to compromise on the physics of flow control. The fluidic-no- moving-part system is the only actuator concept that allows for testing with a velocity ratio similarity on top of Mach number and Reynolds number similarity, as the system can be operated with fluids of any temperature (i.e. cold fluid).
It is therefore believed that the work will impact the current state of the art of local active flow control, providing an enabling technology for maturing this technology stream towards industrialization.

In summary, the project DECOROUS will enable higher TRL experiments to thoroughly validate the concept of local active flow control by pulsed air blowing, provide a flow control system, which fulfils real-aircraft integration requirements and thus contribute to the industrialization of an AFC strategy to the end of UHBR integration, allowing to increase eco-efficiency and reduce DOC.

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