Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - PROBATE (Planet ROlling Bearing with Advanced TEchnologies)

Teaser

The development of Ultra High Propulsive Efficiency (UHPE) engines is a promising engine concept to fulfil the objectives of the Sustainable and Green Engines (SAGE) programme. From an engineering point of view, the significant environmental benefits of this new engine are...

Summary

The development of Ultra High Propulsive Efficiency (UHPE) engines is a promising engine concept to fulfil the objectives of the Sustainable and Green Engines (SAGE) programme. From an engineering point of view, the significant environmental benefits of this new engine are synonymous with the introduction of the Ultra High Bypass Ratio (UHBR) technology. Current engine designs are indeed reaching their limits in terms of efficiency (i.e. conventional BPR is about 9-10, future UHBR target is 12-15). This is why innovative architectures like the geared turbofan concept that decouples fan and turbine speeds by means of a high Power GearBox (PGB) are the promising enablers for UHPE engine success.

This PGB introduction raises different technological challenges at the system and component scales: PROBATE project will focus on the planet bearing component, the central module of the transmission system of the gearbox.

In terms of engine performance, the design, sizing and capacities of the planet rolling bearings can affect the whole engine architecture. The rolling bearings have been clearly identified as crucial components with respect to reliability.
Nowadays, new engine architecture developments are possible only if they take into account new technologies and developments for engine’s component parts.

The main scope of PROBATE project is “to predict bearing behavior (through dynamic, lubrication & thermal coupled modelling) and develop various planet rolling bearing technologies, overcoming current design rules of aero-engine bearings enabling the development of a UHPE engine (or other high performance architectures)”.

PROBATE project will also contribute to the raising of the Technology Readiness Level (TRL) of the proposed bearing technologies, meaning that the overall whole engine system reaching TRL6.

PROBATE is full in line with the Clean Sky 2 programme, since it will support the key Societal Challenge. It will enable cutting edge bearing solutions for further gains in decreasing fuel burn, CO2, NOX, noise emissions and strongly contribute to the renewed ACARE SRIA. PROBATE proposers are committed to support future global leadership of the European aeronautical industry supply chain, creating jobs through and reinforced competitiveness.

The new bearing technologies to be developed in PROBATE will demonstrate the following specific objectives (in comparison to current bearing baseline solution):
- To develop and provide a new numerical model able to predict heat generation and transfer in the planet bearing taking into account interactions between dynamics, lubricant and thermal behaviors
- To demonstrate a -30% in power loss & oil flow and a -15% of the bearing weight in comparison to the current baseline solution & increasing at the same time the reliability.
- To develop and provide an optimized rolling element profile, a specific polymer cage design and an optimized lubrication solution as well as their integration in the new planet bearing

Work performed

The PROBATE project is a 4.5-year project basically decomposed in two main activities related to two different architecture of the Power GearBox: STAR for fixed planet carrier and PLANETARY for rotating planet carrier configuration (involving centrifugal field).

Activities related to PLANETARY configuration will start in 2018 with a bearing design phase covering the development and introduction of a polymer cage and optimized lubrication path architecture. In parallel, modelling activities will be conducted to assess and validate the dynamic behavior of the bearing. In addition, some coating evaluation activities will be conducted to assess sliding and tribological performance of existing coating to identify potential improved solution for the cage guiding function.

Related to STAR configuration, a first bearing design solution introducing ceramic rolling element has been identified and preliminary assessed. Well-known design criteria are currently challenged in order to reach the space envelop and loading conditions targeted. In parallel, activities on numerical modelling has been started by the development of the coupling methodology. Relevant software interaction parameters have been identified and a first iteration of bearing dynamic calculation has been implemented using a simplified model of industrial bearing. Thermal and lubricant behavior considering oil bath has been added. Then an additional iteration has been done considering an increased oil bath level to study the impact on the force involved.
In the next steps, the final planet bearing design introducing optimized ceramic roller profile will be released, manufactured and tested at a subscale level to support the validation of the planet bearing numerical models developed. In addition, a second loop of with high coupling between experimental and computational resources will be performed considering the whole gearbox system.

Final results

The main impact of this proposal is to provide key bearing behavior predicting tool, rolling element, cage and lubrication path architecture technologies for the development of an UHBPE engine and other next generation engines to meet the objectives of the Clean Sky 2 programme in terms of environmental benefits and European competitiveness.
The technical impacts of PROBATE project are potentially extensive because several advances/ innovations will be necessary to achieve the technological step requested.

- The possibility offered by PROBATE project technologies to design new environmentally friendly aero-engines (such as a UHPE engine).
- A full exploitation of bearing potential in terms of performance and behavior through increased knowledge of the interactions between dynamic, lubricant and thermal aspects.

The envisaged technical exploitation of the results is significant as there will be:
a) Direct exploitation of cutting edge rolling bearing technologies (newly developed materials ceramics & polymer) and performance/design possibilities
b) A breakthrough in terms of planet bearing numerical model able to predict heat generation and transfer considering interactions between dynamics, lubricant and thermal behaviors
c) Additional exploitation of some stand-alone results: experimental database results and back-to back comparison on ring steel;

It is also important to note that the developed technologies in this project (material and numerical models) can be transferred, like elementary bricks, to improve performances of other engine technologies or in other sectors (i.e railwayautomotivemaritime).

Employment will be directly linked to the economic impact of PROBATE project at the European and global levels. PROBATE project will maintain and create jobs for aero-engine manufacturers and also for rolling bearing and material suppliers.
Employment of highly skilled personnel will be required for some of the proposed technologies.