Analysis of the stress state of the runner pit of a high-head Kaplan turbine

The stress state is examined under the assumptions of: the pit is considered a ring of constant thickness, ribbing is not taken into account; the pressure diagram is considered constant over the height of the ring; the edge effect is not taken into account. In addition to purely tensile stresses, flexural stresses occur in the pit lining from the pressure varying according to the harmonic law depending on the central angle. Since the course of the solution is the same for all harmonics, only the first harmonic is examined. The steel lining of the runner pit is considered to be a ring located in a concrete mass. It is concluded that the main cause of the fatigue damages of the runner pit is the presence of tensile stresses in concrete adjacent to the pit which are not taken into account.