A spin-out company from Imperial College London has developed a thermal barrier coating for gas turbine parts that can optically feed back its temperature and ageing status even while the engine is running at full speed.
The main application for the technology is in power-generating gas turbines, where the coating could help to achieve significant efficiency savings.
Ceramic thermal barrier coatings, including yttria-stabilised zirconia, are used for the so-called ‘hot section components’ of gas turbines, such as the blades.
They allow the underlying metal components to operate at a much higher temperature, thereby achieving greater performance and efficiency. Nevertheless, Dr Joerg Feist, managing director of Southside Thermal Sciences (STS), claims that many gas turbines still operate within their potential.
‘People are not going to the limits of their engines and people don’t know what the accurate temperature is on their components,’ he said. ’Our technology can provide this. By increasing the temperature, you increase the efficiency, but you can’t increase this indefinitely.’
The company developed a method of doping ceramics with phosphorescent molecules and applying the novel coating with a plasma deposition technique. When irradiated with ultraviolet light, it gives out a characteristic signature depending on its current temperature, corrosion status or other phases.
‘That is what the whole technology is about,’ said Feist. ’You have a multifunction coating that protects in the first instance and in the second acts as a sensor — it senses its own status.’
Sensors for high-temperature environments already exist but Feist stressed that embedding luminescence materials into an existing protective coating provides sensing inside the coating on the component.
‘We can see the material temperature online or offline , we can see changes inside the material when it starts restructuring during thermal exposure and cycles,’ he said.
The company recently purchased two Rolls-Royce Viper 201 engines to test its latest generation of coatings.
‘We modified the engine so it has six windows,’ added Feist. ’We installed two windows to look into the combustion chamber, two windows to look onto the nozzles that are getting the hot air into the turbines and then two windows looking at the rotating turbines blades — we have a system to monitor these environments.’
Two weeks ago, the team successfully gathered temperature data from the coatings on a test engine while it was running at 13,800rev/min — a first for the gas turbine industry, according to Feist.
The company recently performed a trial for RWE npower at the Didcot B power station (a natural gas facility) on its Siemens V94.3(A)1 turbine. It is also in talks with aerospace manufacturers — chiefly for engine research and development applications — and a Formula One team.