Engineering news
In a world first, a team from Heriot-Watt University in Edinburgh successfully demonstrated an optical analysis method which reveals weak areas in thermal barrier coatings on jet turbines. The technique could predict how long the coatings last and lead to improvements, eventually making engines more efficient and reducing costs.
The barriers protect turbines from wear and high temperatures but their lifetime varies wildly from 1,000 hours to 10,000 hours at full thrust, even when applied in the same way. Because of the unpredictability and the potential for failure to be catastrophic, companies replace turbine blades after the shortest estimated lifetime.
In their new method, the Scottish team slowly put strain on pieces of metal sprayed with the same ceramic coatings used by their collaborators Rolls Royce. The researchers then applied gigahertz illumination, which travelled through the coating and bounced off the metal. The reflected light was then measured using a polariscope, showing changes in the ceramic’s refractive index and revealing areas of weakness.
“If we can correlate how the strain distribution is related to the coating's lifetime, then we could determine which coatings will fail first and shouldn't be put into an aircraft and which ones will last much longer,” said research leader Andrew J. Moore. “This would increase the time between services significantly, which would bring huge savings.”
The new technique could help create more heat-resistant coatings, allowing engines to run more efficiently and therefore with less pollution. The team said the automotive and nuclear power sectors, which use similar thermal barriers, could also use the method.
Better reliability will mean fewer delays for passengers, said James McMicking, chief strategy officer at the Aerospace Technology Institute.
“Aircraft engines are expensive to build and to overhaul,” he added to Professional Engineering. “Keeping an engine in service and operating longer therefore reduces the overall cost of ownership and operation for the airline, which flows through to passengers as lower ticket prices.”
The research was published in the Optical Society’s journal Optics Express.