Numerical Simulation On Vibration Of The Tip-shrouded Turbine Blade With Dry Friction Damper

Turbine blade is key component of the turbine. It is very important to the safety of the turbine. Blade will vibrate under the periodic exciting force of the steam turbine, which will lead to the high frequency and low frequency fatigue failure. The dry friction damper between shrouds of the blades could restrain the vibration of the blades and reduce the dynamic stress of the blades, so it is necessary to research the principle of the dry friction damper. The main contents of the paper are as following:(1) The hysteretic spring friction model is introduced to transfer the dry friction force between shroud contacts to equivalent stiffness and damping. Mathematic model of the dry friction damper between shrouds is built by using element MATRIX27.According to this model, the influences of friction coefficient and gap between shrouds are analyzed. And the optimized normal force is calculated, which could make the vibration of the blade smallest.(2)The finite element model of turbine blade with parallelogram shroud is built. The modal and natural frequencies of the blade are calculated. Different factors are considered to analyze their influences on the turbine, such as the temperature and rotation speed. The first natural frequencies under different conditions (room temperature and zero rotation speed, work temperature and rotation speed) are 1436Hz and 1330Hz respectively. The temperature load and centrifugal load have greater influences on natural frequencies of the blade, compared to pressure load. The Campbell chart is drawn to analyze the resonance speed of the turbine blade.(3) The finite element model of turbine blade with zigzag shroud is built. The stress of the blade is analyzed under different work rotation speeds. The modal and natural frequencies of the blade are calculated by using different models (single blade, rows of blades and circled blades model). The results of the modal analysis of the turbine blade with zigzag shroud show that the first natural frequencies of the blades under zero and 100% rotation speeds are 100Hz and 140Hz.(4) Harmonic responses of the turbine blade with parallelogram shroud and zigzag shroud are calculated. Considering the dry friction damper between the shrouds, the dynamic stress value of the parallelogram shroud reduces about 40% compared to that without dry friction damper. The dynamic stress value of zigzag shroud reduces about 55% compared to that without dry friction damper.