Short Answer:

Reaction turbines work in hydroelectric stations by using both the pressure and kinetic energy of water to generate electricity. Water flows through the turbine and applies force on the blades, causing them to rotate. This rotation turns the generator and produces electric power.

These turbines operate fully submerged in water, and the water pressure gradually reduces as it passes through the runner blades. Reaction turbines are commonly used in low to medium head hydroelectric projects and provide efficient energy conversion.

Detailed Explanation:

Working of reaction turbines in hydroelectric stations

Reaction turbines are an important type of water turbine used in hydroelectric power stations, particularly where the water head is low or medium. Unlike impulse turbines that rely solely on the speed or kinetic energy of water, reaction turbines make use of both pressure energy and velocity energy to generate power. They work by the principle of Newton’s Third Law—action and reaction.

These turbines are typically installed in a closed water flow system where water enters under pressure, flows through the turbine blades, and causes a reaction force that makes the runner spin. This movement is then transferred to a generator, which produces electricity.

Main Working Steps of Reaction Turbines

1. Water Inlet
   Water from the penstock enters the spiral casing or scroll case surrounding the turbine. The purpose of this casing is to distribute water evenly to the turbine blades.
2. Passing through Guide Vanes
   Water next passes through adjustable guide vanes (or wicket gates). These vanes control the direction and flow rate of water entering the runner. They ensure that water hits the blades at the correct angle for efficient operation.
3. Energy Conversion in Runner
   As water flows over the runner blades, both its pressure and velocity decrease. This change in pressure across the blades causes the runner to rotate. The design of the blades allows for smooth and continuous conversion of hydraulic energy into mechanical energy.
4. Mechanical to Electrical Conversion
   The rotating runner is connected to a shaft, which turns the generator. This converts mechanical energy into electrical energy. The power generated is then stepped up using transformers and sent to the grid.
5. Water Outlet (Draft Tube)
   After passing through the runner, water is discharged into a draft tube, which expands in size and reduces water velocity. This helps recover some of the remaining energy and ensures smooth water exit.

Key Features of Reaction Turbines

• They operate under hydrostatic pressure and are fully submerged.
• Energy conversion occurs gradually along the blade path.
• Suitable for low and medium head (10–300 meters).
• Common types include Francis and Kaplan turbines.
• Blade angles are often adjustable for variable flow conditions (especially in Kaplan).

Importance in Civil Engineering

Civil engineers are responsible for designing the structures around the turbine such as the spiral casing, draft tube, foundation, and flow control systems. Proper planning ensures minimal losses and maximum energy output from available water resources.

Conclusion:

Reaction turbines work by converting both the pressure and motion of water into mechanical rotation, which is then turned into electricity by a generator. They are efficient, reliable, and well-suited for hydroelectric stations with lower water heads. Their smooth operation and adaptability to changing water flows make them a key component in modern hydropower systems.