Principle Investigator: Prof Kam Chana

Post Doc: Dr Vikram Sridhar

Sponsors: Peter Smout Rolls Royce, CleanSky

Partners: Dutch Diamond

Hybrid Polycrystalline Diamond Bearing

Polished diamond spheres

Project Overview

This project is aimed at developing novel, super hard, non-lubricated air cooled bearings that would give a step change in minimising the engine oil system and its complexity. An SFC gain of 0.1 to 0.3% is anticipated as a result of this project.

The project aims 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 project 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 have 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 industrialisation can be successfully delivered with the work packages that have been assembled to TRL 4, with a final design complete for TRL 5 endurance tests.

Lapped Polycrystalline Diamond spheres to nanometre accuracy

Objectives of the project

  • Capture the key requirements for current UltraFan® engine designs.
  • Use optimised polycrystalline diamond material (PCD) that has properties suitable for rolling elements in high-speed precision bearings.
  • Optimise the manufacturing route including green body processing and high pressure high temperature (HPHT) sintering for PCD bearing elements; develop non-destructive testing techniques to assess microstructural uniformity and consistency.
  • Investigate and develop novel processing routes for large PCD rolling elements to achieve required dimensions, tolerances and surface finish; develop the metrological capability to control dimensional tolerances, and to quantify the surface finish.
  • Model the thermal and mechanical behaviour of potential configurations of PCD elements in aerospace bearings to support the design of prototype bearings and cooling systems for testing at TRL 4 and above.
  • Investigate the interaction between rolling elements and races to allow the design, development and testing of air-lubricated and cooled bearings.
  • Fully instrument an air-cooled bearing rig for testing and characterising of rolling elements and interchangeable races to TRL 3.
  • Fully instrument a TRL 4 test facility to allow air cooled operation for aero engine sized bearings and characterise rolling elements
    Use the knowledge developed to design PCD bearings for engine architectures such as UltraFan® or Advanced to feed into future TRL 5 testing.