The DEBRA project was aimed at developing novel, super hard, minimally lubricated air-cooled bearings that would give a step change in reducing the engine oil system and its complexity. An SFC improvement of 0.1 to 0.3% is anticipated following successful completion and maturation of all elements of this project.
The project aims were to achieve this by developing air cooled bearings using synthetic diamond. The novelty is in the surface finish of diamond rolling elements and mating raceways which can be improved substantially relative to today’s metallic bearing materials such that heat generation and frictional wear is minimised. Diamond offers superior thermal properties enabling thermal gradients and running clearances to be optimised.
This proposal aims to reduce oil system cost, weight and complexity by exploiting the properties of synthetic diamond material in the design and manufacture of novel bearings. The basic premise is that the surface finish of diamond rolling elements and mating raceways can be improved substantially relative to today’s metallic bearing materials such that heat generation and frictional wear is minimised. Diamond’s superior thermal properties enable thermal gradients and running clearances to be optimised using air rather than oil as the cooling medium.
The partners had assembled a consortium that has bearings expertise, unique European capability in the manufacture, forming and metrology of synthetic diamond materials, and a proven track record in the design and evaluation of gas turbine air cooling schemes, with test facilities that will allow for friction and integrity proving from technology readiness level (TRL) 2 to 4. The consortium believe that all aspects of demonstration and some aspects of industrialisation has been successfully delivered with the work packages that have been completed to TRL 4, with a final design complete for TRL 5 endurance tests.
The project demonstrated a world first by producing PCD rolling element bearings of 40mm diameter and validating these with air cooling to TRL 4 at high load and high speed. The PCD bearing was shown to outperform the steel and silicon nitride bearings when air cooled without oil lubrication.
DEBRA is a Clean Sky 2 Programme Project.
