Effect of Crack Orientation and Notch Angle in the Performance of Francis Turbine in Hydropower Generation

摘要

Turbine in which the working fluid comes under immense pressure and the energy is extracted by the turbine blades from the working fluid. A part of the energy is given up by the fluid leads to change in pressure while water is gliding over the bladesis called 'reaction pressure' and is partly responsible for the rotation of the runner. Runner blades are the heart of any turbines. These are the centers where the fluid strikes and the tangential force of the impact causes the shaft of the turbine to rotate, producing torque. Turbines are frequently operated over an extended range of regimes. At this regime the pre-existing crack in the turbine blades majorly affects the power productions. Close attention in cracks of blade is necessary; hence the stress intensity should be continuously monitored so that precautions can be taken before it overshoots the critical value. For this purpose, a crack at different inclinations and different notch angles has been investigated using ANSYS for mixed mode. Fromthese investigations, for all notch angles of varying sharpness, it can be observed that when the inclination angle increases, since the Mode III stress intensity factor increases, the failure by Mode III becomes comparatively tougher. It is very much beneficial since the mode III failure is the most dangerous of all. The results showed that the in-plane cracks may reduce the out-of-plane strength of in fills up to 100% and the out -of-plane shear adds to the decreasing capacity of the component.