Lighter, safer aircraft engines thanks to improvements in friction phenomena

• The LUBGEAR project will generate the knowledge necessary to design lighter and more efficient gear and lubrication systems for the aviation engines of the future

The European aviation industry is aiming to become competitive in the civil aviation market and maintain its leadership position in the manufacture of short to medium passenger aircraft. The CleanSky2 programme is part of the European Union´s Research and Innovation funding programme Horizon 2020 and is managed by the Clean Sky Joint Undertaking (CSJU), a public and private initiative that coordinates and funds research and development activities in order to speed up the process of delivering quieter and more environmentally friendly aircraft. To achieve this, it will be essential to use innovative engine technologies that are increasingly efficient. The LUBGEAR project will be carried out within this context and one of its objectives is to advance knowledge about friction phenomena in gear systems, mainly when they operate with reduced lubricant supply, and even with loss of lubrication. This advance in knowledge will enable to design lighter gearboxes and lubrication systems, without compromising safety, thus reducing the aircraft greenhouse gas emissions.

Nowadays, the most commonly used engines in aviation are turbofan and turboprop ones, both based on the use of gas turbines. Under the European Clean Sky2 programme new generations of these engines are in development and they are characterised by low fuel consumption, high efficiency, lower noise levels and lower CO2 emissions. One of the key enabler to support these solutions is the power gearbox that will be required to be very efficient, light, compact and reliable. Power gearboxes are being studied extensively, but their behaviour in off-design conditions, such as temporary loss of lubrication, is still to be understood. Loss of lubrication is responsible for scoring of gears and bearings. To avoid damage to the gearbox when this occurs, and to guarantee safety, there are different solutions, among which is the use of an auxiliary or emergency lubrication system or the use of emergency cooling systems, involving an increase in the weight of the aircraft. The LUBGEAR project aims at offering innovative solutions based on a deeper understanding of friction phenomena between gears when there is reduced lubricant supply or even loss of lubrication.

The project is part of the Innovative Aircraft Demonstrator Platform (IADP) Large Passenger Aircraft (LPA) focus area within Clean Sky2. Avio Aero is the Topic Manager, the private member appointed by the CSJU as responsible for the topic, who will ensure that the project helps to deliver on the objectives of the Advanced Engine & Aircraft Platform and general objectives of Clean Sky2. Avio Aero is a GE Aviation business that designs, manufactures and maintains components and systems for civil and military aviation. The company has over 5,000 employees in 7 production sites in Italy, Poland and Czech Republic. With over 110 years of history, the company has always been at the forefront of technological innovation, as evidenced by its recognition as a pioneer of Additive Manufacturing in Europe.

Four entities are involved in the project, coordinated by CIDETEC Surface Engineering, which contributes with its experience in the development of new high added value surfaces such as, for example, self-lubricated surfaces. CIDETEC will be also in charge of the design of experiments and will make available its experience in the coordination of European Commission funded projects (coordinating 9 out of the 24 in which it has participated), especially for the aviation sector (12 projects in total, 5 of them coordinated). The Austrian Excellence Center for Tribology, AC2T, will be responsible for carrying out a complete test campaign to create a unique database and extend contact modelling tools. AC2T is one of the largest private tribology centres in Europe. The Technical University of Munich is also participating with its internationally recognised Gear Research Centre, FZG, specialised in gear and transmission design, optimisation and testing. FZG will be in charge of validating the most promising solutions for gears operating in off-design conditions on a TRL3 level test rig. The project will also count on the participation of ZOERKLER, an Austrian company that manufactures transmission systems, which has years of experience in the design and manufacture of gears for aircraft and helicopter engines. Its role in the project will be to manufacture the test articles and to provide its knowledge in gears design to optimise the geometry of the gears in order to improve their sustainability and efficiency.

"This project has received funding from the Clean Sky 2 Joint Undertaking (JU) under grant agreement No 101007713. The JU receives support from the European Union's Horizon 2020 research and innovation programme and the Clean Sky 2 JU members other than the Union".