Thermocouple shows much lower high temperature drift 20 September 2013

A temperature sensor developed by researchers at the University of Cambridge could improve the efficiency, control and safety of high temperature engines.

The thermocouple has been shown to reduce drift by 80% at temperatures of 1,200°C and by 90% at 1300°C, compared to conventional Type K, N, R and S alternatives – potentially doubling the lifespan of engine components, according to the development team.

Accurate temperature control is critical at higher temperatures and a temperature error of 10°C can trigger engine failure, they warn.

However, with the temperature in a modern jet engine reaching 1,500°C, the drift in nickel based thermocouples increases to unacceptable levels.

To overcome this, thermocouples are generally placed away from the hottest part of the engine and the maximum temperature is extrapolated.

"A more stable temperature sensor provides several advantages – a better estimation of temperature can increase the lifetime of engine components and decrease maintenance costs to manufacturers, without any reduction in safety," explains Dr Michele Scervini, a postdoctoral researcher in the Department of Materials Science and Metallurgy, who developed the new thermocouple.

Dr Scervini, along with Dr Cathie Rae, has developed a thermocouple that features an outer wall of a conventional oxidisation resistant nickel alloy, which can withstand high temperatures, and an inner wall of another, impurity-free nickel alloy, which reduces drift.

Results from tests on a prototype device showed a significant reduction in drift at temperatures of 1,200°C and 1,300°C.

"Nickel is an ideal material for these applications as it is a good compromise between cost and performance," Dr Scervini.

"But there is a gap in the market for applications of more than 1,000°C. We believe our device could see widespread usage across a range of industries."

Brian Tinham

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