A Review of Exhaust Gas Temperature Sensing Techniques for Modern Turbine Engine Controls

The exhaust gas temperature (EGT) is typically defined as the gas temperature at the exit of the turbine; the sensors used to measure this parameter are considered the most vulnerable elements of the entire turbine engine instrumentation. EGT measurement is considered a key parameter for optimizing fuel economy, diagnosis, and prognosis. The reason is that turbine blade temperature is a good indicator for normal life consumption of that blade. Currently, direct sensor measurements made on turbine modules are limited due to the extremely hot environment. Exhaust gas temperature (EGT) sensors located downstream from the highest temperature sections provide a means to roughly infer the temperatures seen by the turbine blades/disks. But these sensors, which themselves are subject to frequent failures, provide a fairly inaccurate indication of the actual metal temperature profiles. This is of particular importance for high performance military turbine engines where the margin between hot-section operating conditions and material limitations is shrinking. A future state is envisioned that would use emerging pyrometric, fiber optic, and laser-based sensing to accurately assess the condition and life usage of the hot section, on a blade-by-blade basis.