PSI - Issue 57

Malik Spahic et al. / Procedia Structural Integrity 57 (2024) 833–847 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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The simplified model represents the slice bottom left corner of the 1 st stage of the rotor (see Figure 15), which based on the 2D model is the most critical location. The calibration is ensured by a correction factor used on the 1D model that enables to take into account the local geometry and the axial effects, not considered by the 1D model.

Figure 14: Stress distribution inside the rotor for Rotor B. The maximum stress is at the root of the disc

It can be seen that the 1D model is not always able to precisely match the temperature and stress outputs of the 2D model. A best estimate calibration is done in order to obtain comparable lifetime consumptions for both 2D and 1D models, following R5 or ASME assessments [2,3]. The parameters of the lifetime consumption calculation have been adapted based on experience and case studies with cracked rotors. Table 1 shows the final lifetime consumption values of the three rotors encountered so far, during their whole lifetime history.

Table 1: Final lifetime consumption of the Rotors A, B and C during their whole lifetime history

Name of the rotor

Rotor A

Rotor B

Rotor C

Lifetime consumption (in %)

250

14

72

As indicated in the introduction, for Rotor A, the methodology confirms the presence of a crack and also shows that crack propagation takes an important part of the total lifetime. For the two other rotors, the methodology estimates that no crack has yet initiated on these rotors which was confirmed by visual inspections done at the moment of these studies. For Rotor C however, the probability for a crack to appear before the next major overhaul was assessed to be high based on the expected future operational profile. A surface machining was therefore performed on the most critical areas (see also Section 5.3).

Figure 15: Location of the slice of the rotor that is simulated by the 1D model