Periodic Reporting for period 3 - BrEATHE (high capacity planet BEAring Technology for High Efficiency gearbox)
Reporting period: 2022-01-01 to 2022-04-30
The development of Ultra High Propulsive Efficiency (UHPE) engines is a promising challenge to fulfil the objectives of CleanSky 2 ITD ENGINES program and the potential for significant reduction in fuel burn, emissions and perceived noise to the level defined by “ACARE 2035”. Current engine designs are indeed reaching their limits in terms of efficiency (i.e. conventional bypass ratio (BPR) is about 9-10, future UHBR target is 12-15). This is mainly the reason why innovative architectures like the geared turbofan concept are the promising enablers for UHPE engine success. The development of such Integral Drive System raises different technological challenges at the system and component scales. BrEATHE project, standing for BEAring Technology for High Efficiency, will focus on the planet component, the central module of the transmission system of the high power gearbox, where the bearings are key elements. The specificity of the BrEATHE bearing remains in functional integration: a gear with integrated bearing outer raceway.
BrEATHE project objectives can be divided in these main steps:
1. Design of a bearing to be mounted in a high-power gearbox
2. Low TRL evaluation of high-performance steels.
3. Production of the prototype bearings
4. Testing of the bearings
5. Model correlation based on test results
The step 3 to 5 have not been performed in the framework of the project, although the project has not been completed, the continuation of the research is expected to provide key bearing technologies (material and design) and advanced computational models enabling the development of the innovative power gearbox of the future UHPE engine and other next generation engines to meet the objectives of the Clean Sky 2 programme in terms of environmental benefits and European competitiveness such as the reduction of aircraft CO2 & NOx emissions, the validation of innovative engine technology and employment.
BrEATHE project objectives can be divided in these main steps:
1. Design of a bearing to be mounted in a high-power gearbox
2. Low TRL evaluation of high-performance steels.
3. Production of the prototype bearings
4. Testing of the bearings
5. Model correlation based on test results
The step 3 to 5 have not been performed in the framework of the project, although the project has not been completed, the continuation of the research is expected to provide key bearing technologies (material and design) and advanced computational models enabling the development of the innovative power gearbox of the future UHPE engine and other next generation engines to meet the objectives of the Clean Sky 2 programme in terms of environmental benefits and European competitiveness such as the reduction of aircraft CO2 & NOx emissions, the validation of innovative engine technology and employment.
Objective 1
5 over 15 advanced steels materials have been selected through a weighted multi-criteria decision matrix. The most weighted criteria are the key characteristics to increase the contact pressure of +15%. Moreover, each of the material candidates have faced criteria to allow the Gear/Rolling bearing use: the functional integration of a gear with integrated bearing outer raceway pushes for a different prioritization in optimal metallurgical properties. Thanks to these 5 advanced steels materials, a good compromise has been found to manufacture a high-power density bearing.
The two following material routes have successfully achieved objective 1 criterion at TRL3
Objective 2
The selection of a polymer material for the bearing cage as well as the selection of ceramic rollers aim to reduce the heat generation and thus reduce the power loss by 30% compared to the baseline. The ceramic rollers have already been manufactured and the manufacturing of the cage has been performed Q1 2022.
The bearing compactness allowed by the increased loading capacity has been designed for back-to-back testing against current bearing technology.
Gearing definition of the outer ring have been developed in an iterative process with the manufacturer, SKF and the topic manager in order to ensure the manufacturability of the bearing definition
Validation simulations have been run to validate that the modification on the gearing will not impact the representativity of the testing conjointly with the test head manufacturer and the Topic Manager for gear design.
Objective 3
The manufacturing of the bearings has started beginning of 2022. Routes for manufacturing of TRL5 bearings have been done at the prototype shop.
The main work carried out during 3rd period was to converge towards a bearing definition.
Due to the delays occurred during the project, and since the request for extension was not accepted by the JU, the manufacturing was not completed by the end of the project (30/04/2022) and has been put on hold.
Objective 4
The test platform dedicated to BrEATHE is fully operational and ready to welcome BrEATHE test bench.
The detailed test head design is frozen and all the components in manufacturing or all purchase started.
Objective 5
Half of the objective have been carried out. D4.1 (DOE on planet bearing design report) and D4.2 (detailed planet bearing design modelling report) related to building simulations model for design definition of the planetary bearing have been delivered. The use of SKF internal calculation software have allowed to design a compact hybrid planetary bearing .
The rest of the work regarding this objective should have been happening during the correlation of the model with the tests performed.
Objective 6
In line with the Topic Manager, the choice of materials for raceway advanced steels has been done also in order to optimize the technology introduction time by choosing materials already available on the market.
BrEATHE project will benefit from SKF AEROENGINE protoshop where TRL5 bearings will be manufactured by serial production machines. Thus, thanks to product engineering working conjointly with the prototype shop, the BrEATHE bearings with new advanced steel for raceways technologies will be manufactured based on existing serial production process. This is a way to mitigate the latest raceway steel technologies introduction to market.
Moreover, the already operational test bench will optimize the confidence level of new introduced technologies and optimize the experimental - computation interaction and complementarity.
5 over 15 advanced steels materials have been selected through a weighted multi-criteria decision matrix. The most weighted criteria are the key characteristics to increase the contact pressure of +15%. Moreover, each of the material candidates have faced criteria to allow the Gear/Rolling bearing use: the functional integration of a gear with integrated bearing outer raceway pushes for a different prioritization in optimal metallurgical properties. Thanks to these 5 advanced steels materials, a good compromise has been found to manufacture a high-power density bearing.
The two following material routes have successfully achieved objective 1 criterion at TRL3
Objective 2
The selection of a polymer material for the bearing cage as well as the selection of ceramic rollers aim to reduce the heat generation and thus reduce the power loss by 30% compared to the baseline. The ceramic rollers have already been manufactured and the manufacturing of the cage has been performed Q1 2022.
The bearing compactness allowed by the increased loading capacity has been designed for back-to-back testing against current bearing technology.
Gearing definition of the outer ring have been developed in an iterative process with the manufacturer, SKF and the topic manager in order to ensure the manufacturability of the bearing definition
Validation simulations have been run to validate that the modification on the gearing will not impact the representativity of the testing conjointly with the test head manufacturer and the Topic Manager for gear design.
Objective 3
The manufacturing of the bearings has started beginning of 2022. Routes for manufacturing of TRL5 bearings have been done at the prototype shop.
The main work carried out during 3rd period was to converge towards a bearing definition.
Due to the delays occurred during the project, and since the request for extension was not accepted by the JU, the manufacturing was not completed by the end of the project (30/04/2022) and has been put on hold.
Objective 4
The test platform dedicated to BrEATHE is fully operational and ready to welcome BrEATHE test bench.
The detailed test head design is frozen and all the components in manufacturing or all purchase started.
Objective 5
Half of the objective have been carried out. D4.1 (DOE on planet bearing design report) and D4.2 (detailed planet bearing design modelling report) related to building simulations model for design definition of the planetary bearing have been delivered. The use of SKF internal calculation software have allowed to design a compact hybrid planetary bearing .
The rest of the work regarding this objective should have been happening during the correlation of the model with the tests performed.
Objective 6
In line with the Topic Manager, the choice of materials for raceway advanced steels has been done also in order to optimize the technology introduction time by choosing materials already available on the market.
BrEATHE project will benefit from SKF AEROENGINE protoshop where TRL5 bearings will be manufactured by serial production machines. Thus, thanks to product engineering working conjointly with the prototype shop, the BrEATHE bearings with new advanced steel for raceways technologies will be manufactured based on existing serial production process. This is a way to mitigate the latest raceway steel technologies introduction to market.
Moreover, the already operational test bench will optimize the confidence level of new introduced technologies and optimize the experimental - computation interaction and complementarity.
The expected results of BrEATHE projects are potentially huge, because of the several major advances/innovations necessary to achieve the project technological objectives as well as the next generation UHPE engines. The BrEATHE bearing technology and modelling solution will lead to:
- the increase of design compactness and the reduction in bearing weight while keeping the same load level in comparison with the current state of the art; this will lead to a reduction in the engine size (mass saving) and therefore a direct reduction of fuel consumption and CO2/NOX emissions.
- the decrease of the power loss of the PGB bearings (-30%), by using advanced design for lubrication and roller, thermal mapping and low friction materials/coatings.
- run at higher rotational speeds (>9,000 rpm) for the planetary bearing using low density material, advanced lubrication system and high surface resistance raceways leading to a significant reduction in fuel burn, noise (-30%) and emissions (-25%) while allowing a reasonable core and engine size.
- bring substantial advantages in terms of bearing/system reliability using a high accuracy dynamic modelling of the whole PGB.
Other environmental/economic/social impacts include:
- The possibility offered by BrEATHE project technologies to develop and implement new environmentally friendly aero-engines (such as a UHPE engine).
- A full exploitation of components with increased lifecycle.
- The reduction of the bearing heat generation is also a way to reduce the whole lubrication system (pump, tank, pipe…), which leads to an indirect weight saving.
- Employment of highly skilled personnel in the aerospace industry as the development of bearing design based on dynamic and thermal models will demand high skills and expertise for both design and production in the next 10 years.
- the increase of design compactness and the reduction in bearing weight while keeping the same load level in comparison with the current state of the art; this will lead to a reduction in the engine size (mass saving) and therefore a direct reduction of fuel consumption and CO2/NOX emissions.
- the decrease of the power loss of the PGB bearings (-30%), by using advanced design for lubrication and roller, thermal mapping and low friction materials/coatings.
- run at higher rotational speeds (>9,000 rpm) for the planetary bearing using low density material, advanced lubrication system and high surface resistance raceways leading to a significant reduction in fuel burn, noise (-30%) and emissions (-25%) while allowing a reasonable core and engine size.
- bring substantial advantages in terms of bearing/system reliability using a high accuracy dynamic modelling of the whole PGB.
Other environmental/economic/social impacts include:
- The possibility offered by BrEATHE project technologies to develop and implement new environmentally friendly aero-engines (such as a UHPE engine).
- A full exploitation of components with increased lifecycle.
- The reduction of the bearing heat generation is also a way to reduce the whole lubrication system (pump, tank, pipe…), which leads to an indirect weight saving.
- Employment of highly skilled personnel in the aerospace industry as the development of bearing design based on dynamic and thermal models will demand high skills and expertise for both design and production in the next 10 years.