PSI - Issue 24

14

Vincenzo D’Addio et al. / Procedia Structural Integrity 24 (2019) 510–525 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

523

5. Results on preliminary design In this section some of the main results coming from the application of the described methodologies to the pump rotating assembly are summed up. It is important to specify that the stiffness value of the bearings is not a precise number but it statistically varies within two limit values corresponding to the minimum and maximum internal clearance (given by the tolerances of the bearing itself); since the system is pretty sensitive to the stiffness value, the results related to the whirl natural frequencies for both Kr min and Kr max cases are reported in Table 2. Table 2. Natural whirl frequencies as ratios of the operating rotational frequency (case Krmin and Krmax).

K r min

K r max 1 BW = 2.70 ω̅ 1 FW = 3.15 2 BW = 4.35 ω̅ 2 FW = 4.78 3 BW = 11.89 ω̅ 3 FW = 12.93 4 BW = 15.78 ω̅ 4 FW = 16.99

ω̅ 1 BW = 2.56 ω̅ 1 FW = 2.99 ω̅ ω̅ 2 BW = 4.29 ω̅ 2 FW = 4.70 ω̅ ω̅ 3 BW = 11.31 ω̅ 3 FW = 12.38 ω̅ ω̅ 4 BW = 15.63 ω̅ 4 FW = 16.84 ω̅

Fig. 14. Dimensionless Campbell diagram (case Krmin and Krmax) (see nomenclature).