A study of two optical fibre probe designs for use in high-temperature combustion gases

The difficulties of using thermocouples in combustion environments above 1500-1600 C over extended periods are well known. This work investigates the use of high-melting-point optical fibres acting as emissive sources, as a means of meeting the real engineering needs of the combustion environment. Two designs are reported, the first based on a water-cooled low-temperature transmitting fibre and the second on an all-ceramic construction. The probes have been subjected to an extended operating period with repeated cycling in gas environments up to 2600 C and tip temperatures up to 1850 C and their performance, in terms of reproducible output in the 1400-1600 C range , is presented.