The turbine are mainly of two types – Impulse and Reaction Turbine. In Impulse Turbine the hydraulic energy of the fluid is converted to kinetic energy through a nozzle. The jet created by the nozzle runs the turbine blades. In reaction turbine no nozzle is used. A part of the total available energy is converted to the kinetic energy. Both pressure and velocity changes while the fluid passes the runner through a reaction turbine. The pressure – velocity curve of these two types of turbines will be explained in this article. Impulse Turbine has more hydraulic efficiency than the reaction turbine.
Here it is seen that steam passes the nozzles and there is an increase in the velocity. The pressure is dropped in the nozzle. When the steam enters the moving blades the velocity is decreased and the pressure remains constant.
The above figure shows a simple graph which represents pressure and velocity lines of a reaction turbine. In reaction there is no presence of nozzles sets of Fixed Blades and Moving Blades are arranged in an order. When the steam passes the fixed blades it’s velocity increases and there is a drop in the velocity after passing the moving blade. And pressure is dropped in the fixed blade and there is another drop of pressure in the moving blades . So it is seen that both pressure and velocity changes in the reaction turbine when the fluid passes the runner .