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Demonstration of a Decontamination Device Protoype for buisness jets and Experimental Validation

Periodic Report Summary 1 - CLEANLE2 (Demonstration of a Decontamination Device Protoype for buisness jets and Experimental Validation)

Project Context and Objectives:
CleanLE2 is part of the Cleansky FP7 European research program which develops breakthrough technologies to significantly increase the environmental performances of airplanes and air transport. Aim of the CleanLE2 project is to validate the concept of a wing leading edge cleaning device moving on the wing. The interest of such a cleaning device is to remove debris, for example insects, that accumulate on the wing during the taxi and take-off phase which can disrupt the aerodynamic flow and promote transition to turbulent flow on wings designed for low drag laminar flow. Indeed contaminants with a height as small as 0.05 mm can cause turbulent flow on wings cruising at high speed and increase total drag and thus fuel consumption.
The present project is a follow up of the first CleanLE project in which several methods for cleaning the wing have been analysed and the working principles of such a system (kinematics, cleaning methods, structure of the system) have been defined.
First step of the project (WP2) is the design of a prototype for the CleanLE system which consists of 2 cleaning shuttles moving on the wing and performing the cleaning, a driving system inside the wing and 2 carts moving inside the wing on the driving system which ensure the (magnetic) coupling with the cleaning shuttles. In parallel preliminary tests (WP3) are performed to support the design work of WP2 (cleaning efficiency, magnetic coupling, etc.)
Two types of experimental tests (WP6) are planned : wind tunnel tests to assess the aerodynamic forces experienced in flight on the cleaning devices and ground tests to investigate the cleaning efficiency and the mechanics (kinematics, magnetic coupling). WP4 is a work package dedicated to the preparation of the tests and covers both the design of the test benches, the definition of the test matrices and the adaptation of the CleanLE device for the tests, while WP5 is dedicated to manufacturing of the hardware necessary for the tests. After the tests, needed improvements will be designed and integrated (WP7) and tested in a second campaign (WP8). Finally, WP9 will sysnthetise the work done.
The main objective of the project is to bring the cleaning system concept defined in the first project from a TRL of 2-3 (proof of concept) to a TRL of 5 (technology tested on relevant environment).
Project Results:
The system has been designed in WP2 with extensive use of numerical engineering methods: computational fluid dynamics (CFD) software for estimating the aerodynamic forces encountered in flight, computational magnetostatic to size the magnets holding the cleaning devices on the wing and computational solid mechanics to size the components and estimate the loads on the structural parts. The design phase of WP2 has been extended to M8 in order to integrate all conclusions from WP3.
In WP3 (Pre-tests) a method for contaminating wing surfaces with flies has been devised and built. It consists on a modified leaf-blower which « shoots » fruit flies (Drosophilae) at a speed of 130 Km/h and can thus contaminate surfaces in a representative way. Additionally a laser based sensor has been chosen to measure contaminants height before and after the tests. Cleaning tests have been performed on aluminium sheets contaminated with the aforementioned procedure. Various cleaning tools (brushes, sponges, cloths) have been used for cleaning in both dry and wet conditions using 3 different liquids. For the best combination of sponge and liquid it was possible to clean sufficiently the wing after 4 passes. Using a more abrasive sponge leads to scratches on the aluminium sheet. However it is assumed that a painted wing will be more resistant to scratches, allowing the use of more abrasive sponges and/or more pressure applied on the sponges). This will be tested in WP6. An important result of WP3 is that dry cleaning proves ineffective, so that a cleaning liquid is necessary.
Scraping the wing leading edge with a nylon string has been tested on an aluminium cylinder and proved successful. This method will be used to clean the high curvature part of the leading edge.
For the ground tests it has been decided to « shrink » the reference wing leading edge. 3 test zones have been selected (which correspond to wing root, mid wing and wing tip) which are connected with transition zones. The wing will be built from scratch and mounted on a structure which allows rotation of the wing to ease the contamination process and the application of weights that simulate the aerodynamic loads. Transition zones will be built with wood and covered with aluminium sheets to limit the cost. The CleanLE prototype has been updated to take into account comments of the experimental test team (ZHAW), to increase the mechanical stability of the prototype (various CSM simulation have been performed), to ease manufacturing of the parts and to limit cost by choosing as many off-the-shelf parts as possible. CleanLE prototype manufacturing is completed, manufacturing of the wing is ongoing.
The setup for the wind tunnel test bench consists in two endplates 4.7m long, 2.6m height, placed 1.0m apart and installed in the main test section. The wing, equipped with the prototype cleaning device, will be hold by the rotating guiding devices integrated in the endplates in order to vary precisely the angle of attack. PPMA plane disks attached to and rotating with the guiding devices will allow the fixation of the wing. The wing geometry is constructed by taking a representative section of the reference wing (at 1/3 of the span) and extruding it for 1m with a 10° sweep. The devices are then placed on both sides of the wing in the central section. An adaptation is necessary along the span of the model to be able to test the three angles of sideslip and keep the device in the middle of the test section. Flat plates mounted on the wing near the endplates will be used to « trap » the boundary layer developing on the endplates. To gather information about the flow 64 pressure sensors will be used whose positioning has been decided after extensive CFD simulations. Additionally oil flow visualisation will be performed. The wing has been manufactured and the mounting of the experimental setup is ongoing.

WP 5 is delayed until M17 instead of M14 due to longer than expected test bench design phase in WP4; timeline has been compressed to fit into the time line of the project (24 months). Testing (WP's 6 and 8) and Optimisation ( WP7 ) are being now run in parallel with cross-iterations to achieve completion of the Project within 24 months.

Potential Impact:
It is expected to bring the technology readiness level of an in-flight wing decontamination device to a level of 5, by testing the device on a realistic wing geometry and integrating the operating conditions as much as possible, in particular in terms of aerodynamic loads, which will be determined using CFD simulations and validated through wind tunnel tests. Design choices and trade-offs in terms of components, materials and system architecture will be documented and will prove useful for a later industrialization of the system. Additionally, information gathered throughout the project will be useful for the future certification process of the device.
Development of an innovative device for cleaning the wing leading edges of new commercial airplanes which have natural laminar flow wings will improve the fuel efficiency and therefore will reduce the costs and the impact on the environment.
Companies operating regional aircrafts in European extra-territorial areas for humanitarian missions, or transport between islands (such as Azores which are part of Portugal), are daily confronted to the problem of clouds of flying insects. Flying at low altitudes, in take-off and landing configurations, can influence notably their planes performances. For this sector, the conclusions coming from this project will be particularly important.
The new device system might be also source for patents, which increases competitiveness of the European aviation industry and is a plus-value for European countries from an economic point of view.