An approach to indirect estimation of high pressure turbine inlet temperature of turbofan engines based on gas path thermodynamic relations

The most important boundary condition that will allow calculating the temperature and stress distribution of High pressure turbine (HPT) blades and discs is HPT inlet temperature ( T 4 *). Therefore, to calculate accurately the life usage of HPT blades and discs, it is essential to estimate this unmeasured boundary condition for actual engine operation as precisely as possible. This paper proposes an approach to indirect estimation of T 4 * of turbofan engines. Using different thermodynamic relations of a turbofan engine, six models to calculate T 4 * are presented and built with the engine’s performance model. Truncation errors of the coefficients and the temperature models are comparatively analyzed. Then, multiple engines’ testing data as well as 187h endurance testing data are used to further validate and compare the accuracy of these models. Results show that the best model can estimate T 4 * in real time with good accuracy and robustness for engine-by-engine difference and engine operation, which indicates a considerable application prospect for life usage monitoring.