Effects of contact interfaces on rotor dynamic characteristics of heavy-duty gas turbine generator set

The contact interfaces for the rod-fastened rotor of a heavy-duty gas turbine rotor were analyzed and classified into three kinds. In order to predict the effects of contact interfaces on the rotor dynamic characteristics of the heavy-duty gas turbine generator set, the torsional characteristics of the contact segments were studied firstly. The piecewise bilinear torsional deformation model for the contact segments was proposed through theoretical analysis, and was validated with 3D finite element model of the contact segments. Secondly, the bilinear torsional stiffness was obtained using finite element method. And the effects of the preload of the tie-bolts and friction coefficient of the contact interface on the bilinear torsional stiffness were studied. Results show that the preload almost has no effect on the bilinear torsional stiffness. The friction coefficient increases the first linear torsional stiffness obviously, but can decrease the second one slightly. Finally, the first linear torsional stiffness correction coefficients of the contact segments were used to modify the equation of rotor rotation established with finite element based on Timoshenko beam element and lumped element. And the first three torsional natural frequencies were calculated and compared with the results obtained with the unmodified rotor without considering the contact effects.