Exit Flow Conditions

Abstract

In the design of Pelton turbines, it is extremely important to arrange the flow out of the bucket to freely leave the buckets and the Pelton wheel. The exit flow thus contains the kinetic energy which cannot be further exploited and thus will be lost. This type of flow loss is called (see Chap. 9). The associated exit flow conditions depend on the installation form, geometries, and the operation point of the turbine. They are, for instance, differently specified for horizontal and vertical Pelton turbines. At Pelton turbines with vertical axes, the water out of the upper bucket halves should not drop back onto the Pelton wheel. For this installation form of Pelton turbines, therefore, special exit conditions are required. Before this is discussed in detail, it should first be shown how the exit flow velocity and its distribution generally look like along the trailing edge of a bucket. This serves to derive the general exit flow condition.