Pulse cooled thermocouple system for high temperature measurement

Abstract

A pulsed coolant thermocouple temperature measuring system is arranged to measure temperature above a limit operating temperature of the thermocouple includes a rake which is disposed across a hot gas path combustion turbine. Multiple thermocouple are disposed in respective channels in the rake to sense the temperature of hot gas from surplus which enter the thermocouple channels through respective sampling ports in the rake. The sample gas flows merge with a common channel and exhaust through a hot gas sample valve. When any of the thermocouples reaches a limit temperature, a coolant valve is opened as the hot gas valve is closed so as to drive coolant air into the common channel over the thermocouple through the thermocouple channels and the sampling ports into the hot gas path. A microcomputer receives and records the thermocouple signals and generates control signals to sequence the coolant and gas sample valves on and off as a function of the thermocouple temperature signals so the system is cycled through successive temperature reading periods without exceeding a predetermined temperature limit of the thermocouples. The microcomputer extrapolates the actual gas temperature as the endpoint temperature computed by a fast integrating method from the recorded thermocouple readings.