What happens when the blade is vibrated with higher force
Answers
Answer:
it starts vibrating
immediately
When blade is vibrated then faster the steam leaves the last stage blades, the greater the energy loss. Since the backpressure is a function of the plant cooling system, and the flow is a function of the initial plant design, the only cost-effective way to reduce the velocity is by increasing the area. This is achieved by increasing the length of last stage bucket. The two primary forces acting on the blades are the steady centrifugal force due to rotation and the fluctuating steam bending force. The best estimation of dynamic stresses in the blades due to the two known sources of vibration works out to be a small portion of the allowable value. But still, incidences of blade failure are regularly reported. Published reports on compilation of blade failures in power plants say that cause for large number of failure is not fully understood. One such cause on which very little is published is self excitation in long blades