Improved turbine blade lifetime prediction

Algorithms for predicting the remaining lifetime of an engine play an important role in gas turbine monitoring systems. This paper addresses the improvement of models to determine the thermal boundary conditions that are necessary to calculate engine lifetime in critical hot components. Two methods for model development are compared. The first method uses physics-based models. The second method formulates the models based on a similarity concept. The object of analysis is a cooled blade of a high-pressure turbine. Two unmeasured thermal boundary conditions are considered: the heating temperature and the heat transfer coefficient. Instrumental and truncation errors are estimated for each model and 10 faulty conditions are considered to take into account the existing engine-to-engine differences and performance deterioration. The blade temperature and the thermal stress at the critical points are calculated using the results obtained by the developed models as boundary conditions. The results of the comparison show that the physics-based models are more robust to power plant faults. The best models for the heating temperature and the heat transfer coefficient were chosen. It is shown that the accuracy of the heating temperature model is more important for reliable lifetime prediction.