How Frictional Heat Affects the Performance of Underplatform Dampers: Interface Temperature and Dynamic Behaviors

Underplatform dampers (UPDs) not only dissipate vibration energy of turbine blades, but also generate substantial frictional heat. The heat may potentially elevate the interface temperature beyond the melting point. Moreover, the increased interface temperature can alter the friction coefficient and contact normal force, significantly affecting the damping performance of UPDs. Consequently, the blade dynamics are highly coupled with frictional thermal effect. The interface temperature and corresponding dynamic behaviors (e.g. forced response, nonlinear mode) should be assessed considering the effect of frictional heat. In this paper, we develop a multi-physics model of turbine blades with UPDs, which integrates the contact nonlinearity and frictional heat transfer. The thermomechanical contact constitutive relationship is modeled at the contact interface. Two numerical methods are improved and utilized: Dry Friction Thermo-Mechanical Coupling Response Prediction (DFTMCP) and Thermo-Mechanical damped Nonlinear Normal Mode (TM-dNNM). DFTMCP predicts the interface temperature rise and nonlinear forced response, while TM-dNNM facilitates the identification of nonlinear modal characteristics and predicts the detailed temperature distribution. Results indicate quantitatively that frictional heat has a significant effect on the interface temperature and damping performance of UPD.