Temperature measurement in a gas turbine engine combustor

A system for determining a temperature of a working gas passing through a duct defining passage to a turbine section of a gas turbine engine, the system comprising:

• at least one acoustic sensor on the duct located at a first axial location in the engine upstream from the turbine section, the at least one sensor sensing acoustic frequencies, and producing frequency signals corresponding to one or more acoustic frequencies generated within the working gas;
• a processor for determining, for each of the one or more acoustic frequencies, a first temperature value of the working gas at the first location based on a function, T, that is directly proportional to each of the one or more acoustic frequencies and a calculated constant value corresponding to each of the one or more acoustic frequencies;
• a temperature sensor located at a second location in the engine, the temperature sensor providing a temperature signal to the processor corresponding to a second temperature of the working gas at the second location in the engine;
• the processor operating to:
• determining a calculated temperature value for the working gas at the first location based on the second temperature;
• compare the first temperature value determined for each of the one or more frequencies to the calculated temperature value and, for each of the one or more frequencies, change the calculated constant values to recalculated constant values based on the comparison;
• and
• determine subsequent first temperature values at the first location based on the recalculated constant values and further identified acoustic frequencies sensed by the acoustic sensor.