A Case Study of the Contact Force and Stress in the Backup Bearing of a Generator: Experimental Study and Numerical Simulation of Dropdown

Performance evaluation of touchdown bearing using model-based approach

“…In that case, the rotor experiences coupled radial and axial movement that is even more unpredictable and difficult to repeat by means of simulation. An example of the axial displacement of the rotor during the dropdown can be found in the study of Neisi et al [24]. Furthermore, it is expected that the dropdown at the operation speed will be considerably influenced by the unbalance force and, as a result, the touchdown bearing experiences more chaotic force.…”

“…This process may involve several challenges since there are numerous parameters that are not measured and needed to be determined. The earlier study on the dropdown simulation of the rotor under investigation [24], considers that at the start of dropdown, the rotor is at the center of the coordinate system, while the measurement data reveals that due to the effect of the electromagnetic field, the rotor might not be located at the center. In this study, the initial conditions of the rotor are determined using measured signals and modal expansion.…”

“…After the first contact, when the rotor is bouncing back into the air, simultaneously Fig. 6 The prototype for gas turbine [24] moves horizontally and hits the inner ring which is caused by friction force during the contact. Then, the rotor moves back toward center.…”

“…According to study of Gouws [8] the delavitation severity indicators, safe envelope method and the linear extrapolation method can be considered as methods for evaluating severity of dropdown. The authors of the current study have applied the simulation model to study the force and stress in the touchdown bearing [24]. However, the previous study did not introduce methods to evaluate the severity of the dropdown.…”