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EULOSAM Report Summary

Project ID: 325940
Funded under: FP7-JTI
Country: Germany

Periodic Report Summary 2 - EULOSAM (Design and Manufacturing of Baseline Low-Speed, Low-Sweep Wind Tunnel Model)

Project Context and Objectives:
The project is part of a development campaign driven by a business jet aircraft manufacturer since several years. It aims at increasing the aircraft performances in terms of low harmful gas and noise emissions during all flight phases: take-off, climb, cruise, approach, and landing in accordance with the "clean sky" objectives. Lower emission of harmful gases is equivalent to lower fuel consumption and, therefore, is also a very important factor for economic aircraft exploitation. As theoretical predictions must always be confirmed by experimental results, the present project is devoted to manufacturing a wind tunnel model. High speed tests simulating cruise conditions have already been performed, it is now necessary to prepare the low speed testing for the other flight conditions. Fuel consumption decreases if the drag created by the air flow over the aircraft, in particular, over the wings decreases. Since the beginning of human flight, reducing the drag - for a given lift that sustains the aircraft weight - has always been a challenge for aircraft designers and has resulted in highly sophisticated modern wing geometries. Nevertheless, during the last years, a new challenge appeared: A further drag reduction could be realised by maintaining the flow within the so-called "boundary layer" in a laminar state for the longest possible distance from the wing leading edge along the wing chord. However, flow laminarity is very sensible against surface imperfections like roughness, gaps, and steps. The challenge applies particularly to the manufacturing technology for real wings. It can be won by using new composite materials and sophisticated assembly methods. As it is important to quantify the potential of a hypothetical perfect "laminar wing" for predicting the performance of a real industrial wing, the present project aims at producing a wing at reduced scale for wind tunnel tests that approaches the before-mentioned "hypothetical wing". Worldwide it is impossible, for economic and for technical reasons, to place a wing in its real flight dimensions in a wind tunnel and to simulate the real flight conditions with respect to speed. The real wing must be simulated by a down-scaled model with the consequence that a dimensionless characteristic number, the Reynolds number, is down-scaled in the same proportion. The Reynolds number, however, is decisive for the break-down of the laminar state of the flow in the boundary layer. In order to get reliable results with respect to laminarity, the Reynolds number decrease due to scaling down the tested wing is compensated for by a pressure increase within the wind tunnel. In fact, the wind tunnel used for the experiments will be pressurised to round about 4 bar. This fact opens two new challenges, one with respect to design, the other with respect to manufacturing. As far as design is concerned, the aerodynamic loads increase proportionally to the wind tunnel pressure. They are four times higher as they would be in a wind tunnel at atmospheric pressure. For this reason, the "wing box" of the model is not at all a box, it is a massive steel billet. It is only named "box" because the structure of real wings is made like a box. As far as manufacturing is concerned, the reduction of the real wing dimensions to the model dimensions reduces the permissible surface imperfections in the same proportion. In other words, the model surface must be finished like a mirror in order not to precipitate the break-down of flow laminarity and thus falsifying the test results. Furthermore, due to the fact that the wing is not a box, hundreds of very long channels must be drilled into the wing billet for conducting the pressure from the measurement points at the wing surface to the rear of the billet where a flexible tube can be connected for further transport to the pressure sensors. Summarising the project context, it must be stated that the study of flow laminarity over ta wing model creates challenges with respect to design and manufacturing that will be taken up by the consortium.

Project Results:
RP1: Continuing work from the status achieved at the end of period 1, the objective was to manufacture and to deliver the model as foreseen in the Description of Work, namely: - Manufacturing each part should start on the basis of the received CATIA data set (essentially WP 4). In parallel to manufacturing, the measurement equipment and its implementation in the model should be studied, the needed material ordered and installed (essentially WP3).- Once both the foregoing items would have been accomplished, finishing the model should take place with respect to its mechanical condition (dimensions, absence of surface irregularities, ...) and to the correct functioning of the measurement equipment (correct numbering of the flexible pressure tubes, tightness of the pressure lines, check of the strain gauges by applying loads to the model, ...)
RP2: In autumn 2014 it became obvious that, for manufacturing purposes, all design data provided within the frame of a foregoing Clean Sky project must still be translated into drawings in pdf-format. This matter had been discussed between the designer (ARA), the Topic Manager (DA) and the Coordinator (IBK). The designer declared to be unable providing these drawings. Hence, the EULOSAM consortium came in charge of this task. The extra amount of work was compensated by relieving the consortium of the task to perform extensive stress calculations as initially planned. Due to a perfect cooperation between the manufacturer Revoind who had to define the requirements and the partners NHOE and IBK who divided the task on a fifty/fifty basis, many hundreds of drawings have been established and transmitted to the manufacturer until June 2015. This task created an unexpected positive side effect: A lot of discrepancies were found in the form of clashes and drilling concentricity defaults between adjacent parts. With the Topic Manager's help the design was systematically checked in order to detect them all. On the other hand, manufacturing could not start before all the drawings had really been delivered to the manufacturer. In order to cope with the anticipated delay, an extension of the project duration until 30th November 2015 has been approved by the Clean Sky Administration. As explained in item 3, the material for the eight small parts had still to be chosen. Finally, three of them will be manufactured in RAMAX II steel, the five others in much stronger MARAGING steel. In parallel to the establishment of all the drawings and to the choice of appropriate steel qualities for the parts, the equipment of the model was studied. In particular, the needed material to realise more than 300 pressure taps and to install strain gauges at four points on the wing box has been quantified and chosen. At the end of June / beginning of July 2015 a serious accident happened at the Manufacturer's big milling machine that is needed to work on the wing box. Since the accident the machine is unavailable. It was immediately clear to all instances involved in the EULOSAM project that by no means the project can be finished until 30th November 2015. This fact and the advice received on 15th September 2015 from the Clean Sky Administration that only one ultimate request of duration extension will be accepted until 25th September 2015, and in order to have a certain margin, after consultation with the Topic Manager, the request to extend the project duration until 31th December 2016 has been sent to the Project Officer and has been accorded since then.

Potential Impact:
Until the end of period 2 no solution could be found to cope with the unavailability of the damaged machine. The attempt to find a subcontractor wasn't successful. It is anticipated that the partner in charge of all manufacturing work must be replaced by a new partner disposing of the required machines. Also, time constraints and loss of money due to the replacement of a partner will prevent to achieve all the objectives originally defined. It must be anticipated that only a part of the whole model can be delivered at the project end.
The potential impact of the proposal EULOSAM corresponds to some of the medium/long-term objectives advocated in “European Aeronautics: A Vision for 2020”, namely
- to address society’s need for a more affordable, safer, cleaner and quieter Air Transport,
- to win global leadership for European aeronautics.
Successful completion of the present project will contribute - in pushing forward the design of future jet aircraft based on natural laminar flow technology increasing and strengthening the competitiveness of the European manufacturing industry,
- to the success of the SFWA ITD,
- to the need to improve the environmental impact of aircraft with regards to emissions.
As a result, EULOSAM will have a direct impact on the development of new concepts and technologies towards greener and more fuel-burn efficient regional aircraft. Participating in the project is an important opportunity for the companies - all SMEs - forming the consortium
- to get insight into high fidelity test results for an advanced technology aircraft wing,
- to gain a reference project that shows their competence on an international level by winning the call for
proposal against competitors as well as successfully working together as a multi-disciplinary team,
- to increase their know-how and their competences by exploiting the generated IP and by transferring it to
their own industrial applications.

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