Thermocouple shows lower high temperature drift

The thermocouple sensor has been shown to reduce drift by 80% at temperatures of 1200°C and by 90% cent at 1300°C, potentially doubling the lifespan of engine components, says the team. Accurate temperature control is critical at higher temperatures and a temperature error of 10°C can trigger engine failure. However, with the temperature in a modern jet engine reaching 1500°C, the drift in nickel based thermocouples increases to unacceptable levels. To overcome this, the thermocouple is 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," said 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 which features an outer wall of a conventional oxidisation resistant nickel alloy which can withstand high temperatures, and an inner wall of a different, impurity free nickel alloy, which prevents contamination while reducing drift. Results from tests on a prototype device showed a significant reduction in drift at temperatures of 1200°C and 1300°C. "Nickel is an ideal material for these applications as it is a good compromise between cost and performance, but there is a gap in the market for applications of more than 1000°C," said Dr Scervini. "We believe our device could see widespread usage across a range of industries."