Vibration Analysis Of The Steam Turbine Blade With Dry Friction Damper

Turbine blade is the key component of the steam turbine. It is very important to the safety of the steam turbine. Turbine blade will vibrate under the periodic exciting force of the steam, which will lead to the high frequency and low frequency fatigue failure. The dry friction damp between the shroud of the blades could restrain the vibration of the blades and reduce the dynamic stress of the blade, so it is necessary to research the principle of the dry friction damper. The main contents are as following:(1) Finite element method is used to study the modal of the turbine blade with parallelogram shroud. Under the working conditions, the first natural frequency of the 1st and 13th stage turbine are 1027.2Hz and 199.66Hz respectively, which meets the experiment result very well.(2) Finite element method is also used to study the modal of the turbine blade with zigzag shroud. The contact stress and the variation of contact zone between the zigzag shroud is studied by using the contact analysis function of the ANSYS software. The result shows that the first natural frequency of this blade is 100.9Hz and 139.7Hz under zero and 100% working rotation speed respectively. The shroud begins to contact at the rotation speed about 35% working rotation speed.(3) Mathematic model of the dry friction damper between shroud is built to transfer the dry friction force to equivalent stiffness and damp. A test case is calculated by using this model, and the result meets good with that of some reference, which shows the validity of this model. (4) Harmonic response of the two types blade are carried out. Fortran language and ANSYS parametric design language are used to develop a program which could construction the damp matrix and stiffness matrix automatically and then calculate the dynamic stress of the blade under periodic exciting force. The result shows that the dynamic stress value reduces about 50% compared to that without dry friction damp.