Explain the difference between impulse and reaction turbines.

Short Answer:

Impulse and reaction turbines are two main types of hydraulic turbines used to generate electricity from water. The key difference is in how they work with water energy. Impulse turbines use the kinetic energy of fast-moving water jets to spin the blades, while reaction turbines use both pressure and kinetic energy of water to produce motion.

Impulse turbines work with water in air, and water strikes the blades at high speed. In contrast, reaction turbines stay fully submerged, and water flows over the blades, creating pressure difference. These differences decide where each type of turbine is used based on water flow and height.

Detailed Explanation:

Difference between impulse and reaction turbines

Impulse and reaction turbines are both used in hydroelectric power systems to convert water energy into mechanical energy. However, they operate based on different working principles, which make them suitable for different site conditions.

Impulse Turbines

Impulse turbines operate by using high-velocity jets of water that hit the turbine blades. The entire energy of the water is converted into kinetic energy through nozzles before it strikes the blades. The turbine is not completely filled with water; only the blades are hit by water jets.

The pressure of water remains constant during its flow through the turbine; only the velocity changes. This makes impulse turbines suitable for high-head and low-flow conditions. The most common example is the Pelton wheel, which has spoon-shaped buckets that catch water jets and spin due to the force of impact.

Impulse turbines are usually installed above the water surface and require precise nozzle design to control water direction. Maintenance is easier due to the turbine not being submerged.

Reaction Turbines

Reaction turbines work differently. In this type, water flows through the entire turbine and remains in contact with the blades. The turbine operates under pressure, and both the pressure and velocity of water are used to rotate the blades. As water passes over the blades, pressure drops and kinetic energy transfers to the rotor.

Reaction turbines are ideal for low to medium head and high-flow conditions. Common types include the Francis turbine (for medium head) and Kaplan turbine (for low head). These turbines are fully submerged in water and usually placed below the water level, requiring airtight casings and proper draft tubes to maintain pressure and flow.

The design and construction of reaction turbines are more complex than impulse turbines due to the need for tight seals and continuous water contact.

Key Differences at a Glance:

  • Energy Used: Impulse uses kinetic energy only; Reaction uses both pressure and kinetic energy.
  • Water Contact: Impulse is partially in water; Reaction is fully submerged.
  • Installation Site: Impulse for high head, low flow; Reaction for low/medium head, high flow.
  • Blade Action: Impulse blades struck by water jets; Reaction blades are moved by water pressure.
  • Examples: Pelton (impulse), Francis and Kaplan (reaction).

Each type of turbine is chosen based on the head (height of water fall), flow rate, and energy needs. Understanding the difference helps engineers select the right turbine for effective power generation.

Conclusion:

The main difference between impulse and reaction turbines lies in how they convert water energy into motion. Impulse turbines rely on the force of water jets and work well in high-head areas, while reaction turbines use both water pressure and flow, making them better for low to medium head situations. Knowing these differences is essential for choosing the right turbine for hydroelectric power systems.