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ELUBSYS
Engine LUBrication SYStem technologies

Tags: Air

State of the Art - Background

In aeronautics, gas turbine engines need the assistance of systems that guarantee performance throughout the whole flight envelope of the aircraft for which they are designed. One of these systems is the lubrication system and its role is twofold: firstly to remove (via heat exchangers) the heat generated in the highly loaded rolling bearings and gears found in the power and accessory gearboxes; secondly to lubricate these parts.

The current trend of developing aircraft turbine engines that consume less fuel increases the cooling requirements from the lubrication systems due to higher speeds, loads and temperatures in engines, as well as the integration of high-power gearboxes and high-power starter-generators. Current lubrication systems in turbine engines are based on architectures and technologies that have not significantly evolved over the last 30 years. Despite improvements and advances made on the components of these systems, the technological limit is being reached. In other words, new technologies are required to face the challenge of future engine requirements (higher cooling, higher thermal efficiency, lower specific fuel consumption (SFC) impact, same high-level of reliability, improved mass).

Objectives

The overall objective of ELUBSYS is to research, develop and validate a new architectural approach towards the design of high performance aircraft lubrication systems with the aim of reducing fuel and oil consumption. There are four key goals:

- reduce engine SFC and CO2 emissions by significantly reducing (target: 60%) the requirement for bleed air from the engine to pressurise the bearing chambers via the introduction of new high performance seals and by improving thermal management of housings (and ports) by adapting these to the presence of high performance seals;

- reduce the oil quantity rejected overboard by 60%, thus reducing both the consumption of oil, which is a non-renewable energy, and the associated atmospheric pollution by introducing high performance brush seals and improving the supply pump capability;

- optimise the architecture of lubrication systems by reducing their complexity and mass. This will be done by integrating several lubrication functions into one single component and by re-designing other external components;

- develop solutions to improve the monitoring of engine oil quality with a particular focus on the anti-coking capabilities of the lubrication system. This will allow higher oil temperatures to be sustained for longer periods of time, and contribute towards higher engine turbine inlet temperatures.

Description of Work

The proposed work is divided into five technical work packages (WP).

WP1 will address the sealing element of the bearing chambers by:

- investigating the performance of advanced brush seals for the bearing chamber sealing;

- studying the two-phase flow behaviour, heat transfer and pressure loss in the scavenge pipe when brush seals are used and the vent pipes removed;

- investigating the effect on the bearing chamber's thermal behaviour to the reduced air flow anticipated through the brush seals, compared to the labyrinth, and optimising the bearing chamber thermal design.

WP2 aims at a better understanding and modelling of the complex two-phase flows in bearing chambers, scavenge and vent ports, and adjacent pipes.

The objective of WP3 is to produce rules for the different parts of the oil system (supply and scavenge systems and all the related components) in order to improve or optimise their performance and adapt them to the advanced bearing chamber architectures proposed in WP1 and WP2.

The objective of WP4 is to develop and validate numerical methods of characterising and predicting oil ageing and degradation in complex aero-transmission systems, develop a method and a device to monitor oil health in the engine and develop an anti-coking coating.

The overall assessment of the integration of every single improvement will be performed using a global 0D model (WP5).

Expected Results

The anticipated results are:

- the development of design rules in terms of housing architecture, heat management and associated external equipments that will lead to the implementation of advanced seals in aircraft engine lubrication systems;

- a simplified architecture for engine lubrication systems that results in fewer components and reduced mass;

- a set of design rules describing the method of developing more efficient bearing chambers, vent and scavenge pipes, seals and other external elements of the lubrication system;

- accurate methods and rules to predict heat transfer from the hot engine parts inside the lubrication system with a particular emphasis on bearing chambers;

- accurate rules for the design of the external system (pipes, pumps) compliant with advanced housing architectures incorporating tight seals;

- validated methods to predict and detect oil coking.

These results will produce significant technological advances in the area of lubrication for aircraft engines which will fully support the needs of future engine generations. These advances will increase the competitiveness of Europe's aviation industry and airlines because of the improved technologies and savings on operating costs that they will enable, thus offering more reliable and safer aircraft engines and cheaper air travel.

Elubsys rationale

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