Cool control

A more accurate method for monitoring the heat treatment of jet engine components could lead to aircraft that produce fewer emissions.

Scientists at the

(NPL) have reduced the uncertainty of thermocouple temperature sensors used to track heat treatments to less than 1°C.

Aircraft engines work most efficiently and produce fewer emissions when they run at high temperatures, but this requires thermal treatment of their components at temperatures in excess of 1,300°C. If the treatment temperature deviates too much from the optimal temperature, it may be inadequate and a component might have to be scrapped.

Treatment progress is controlled by thermocouple temperature sensors, which are calibrated using materials with known melting or freezing points, known as fixed points. The difficulty up to now has been that there were no reliable low uncertainty fixed points in the high temperature region.

NPL scientists have established a new type of reference fixed point using a material made from a mixture of cobalt and graphite in a composition known as metal carbon eutectic. Graham Machin, head of temperature standards at NPL, said that it was selected for the application because the temperature of the process was around 1,300°C.