ABSTRACT
This chapter deals with three hydraulic turbines, namely, Pelton, Francis, and Kaplan turbines. The first is an impulse turbine while the latter are reaction turbines. The chapter discusses the general setup of a hydroelectric power plant and selection of turbines based on head and power requirements. The characteristics of a Pelton wheel are discussed, and it is shown that for ideal cases the maximum power is obtained when the wheel velocity is half the jet velocity. The design features of Pelton wheels including number and orientation of nozzles, blade shapes, and wheel diameter are discussed. The chapter also deals with the features of Francis and Kaplan turbines. It is seen how they are useful for medium and low heads and why a draft tube becomes an essential feature of reaction turbines. Finally, the concept of cavitation is discussed using the concept of Thoma coefficient. Limitations on the head of the turbine or placement of the exit of turbines above the tails are discussed in the context of cavitation and how these parameters change with specific speed.
