Are you wanting to measure the combustor for a reference of flashback? We normal see type K thermocouple there. Type k measure up to 2300 DEG. F and only for a very short period of time. I believe there is one that will measure approx. 300 Deg. f more than type K and it has a melting point of 3190 DEG. F useful range is 0 to 2600 DEG. F. In the Combustion Turbines today they are equipped with DLN system and they are equipped to measure a an area of the basket and this is the flashback thermocouple area whick stick in the basket about 1/16 of inch.I don't know if there is any newer techknowledge that measure the actual flame temps in a combustion chamber with in a basket or can. We do measure Blade path temps and they two are Type K. They see normal temps of 1200 deg F continues.. This is only speaking of 70 to 300 MW combustion turbines which I have had the privileg to work with.. Note that Flashback is only a reference because when dealing with flashback you also take into affect the combustion shell pressure.
Florida,USA