Reaktioturbiinissa

A reaction turbine is a type of hydraulic turbine that uses both the pressure drop and the kinetic energy of water to produce mechanical work. The water first passes through a stationary guide vanes assembly that directs a portion of the flow into the rotating rotor. The remaining flow then exits the turbine blades, creating a pressure decrease that further accelerates the fluid, thereby contributing to the turbine’s impulse. This dual action distinguishes reaction turbines from pure impulse turbines, which rely solely on the momentum change of the water.

Common designs include the Francis, Pelton‑type, Kaplan, and Turgo turbines, each suited to particular heads and flow conditions. Francis and Kaplan turbines are widely used in medium‑head and large‑head hydroelectric projects. Kaplan turbines feature adjustable blades for variable flow rates, making them ideal in low‑head installations. Turgo turbines are a hybrid design, combining aspects of impulse and reaction principles, and are typically employed in medium‑head sites.

Operation requires precise control of guide vanes and blade pitch to maintain efficiency and avoid cavitation, especially at high heads. The water flow pressure at the rotor inlet is below the upstream pressure, allowing the turbine to maintain a pressure differential. Because the turbine blades are exposed to flow from both upstream and downstream sides, reaction turbines typically have higher efficiency across a broader range of operating conditions. However, they are more complex, requiring careful design of the turbine case and casing to manage pressure losses and fluid dynamics.