Short Answer:
The Pelton turbine works on the impulse principle of water. In this principle, the high-pressure water from the reservoir is converted into a high-velocity jet using a nozzle. This jet strikes the buckets of the Pelton wheel tangentially, producing an impulse force that makes the wheel rotate. The change in momentum of water while deflecting from the buckets produces torque on the runner shaft.
In a Pelton turbine, the entire potential energy of water is converted into kinetic energy before it hits the turbine buckets. The impact of the water jet on the buckets converts this kinetic energy into mechanical energy, which is later used to drive an electric generator for producing electricity.
Detailed Explanation :
Working Principle of Pelton Turbine
The Pelton turbine operates on the impulse principle, which means it converts the kinetic energy of a high-velocity water jet into mechanical energy by the action of impact or impulse. It was developed by Lester Allan Pelton, an American engineer, in the 19th century and is mainly used for high-head and low-flow hydroelectric power plants.
The working of the Pelton turbine depends on Newton’s Second Law of Motion, which states that the rate of change of momentum produces a force. When a water jet strikes the bucket of the Pelton wheel, the direction of water flow changes drastically, resulting in a change in momentum. This change in momentum applies an impulse force on the bucket, causing the runner to rotate.
Step-by-Step Working Process
- Water Supply and Nozzle:
Water from the reservoir flows through a long pipe called the penstock. The penstock delivers water to the nozzle, which converts the pressure energy of water into kinetic energy. The nozzle forms a high-velocity water jet directed toward the Pelton wheel buckets. - Flow Control by Spear:
Inside the nozzle, there is a movable spear or needle that controls the flow rate of the water jet according to load requirements. By moving forward or backward, the spear changes the size of the jet opening, thus regulating the water flow. - Jet Striking the Buckets:
The high-speed jet from the nozzle strikes the double-cupped buckets mounted on the periphery of the runner. The water jet hits the center ridge (splitter) of each bucket, dividing it into two equal streams. - Impulse Force and Wheel Rotation:
When the jet hits the bucket, it changes direction by almost 180°. This change in direction of water flow produces a reaction force or impulse force on the bucket. The impact of the jet makes the bucket move, causing the runner (wheel) to rotate. - Energy Conversion:
During this process, the kinetic energy of the water jet is converted into mechanical energy of the rotating wheel. After striking the bucket, the water loses its energy and falls into the tailrace at atmospheric pressure. - Power Transmission:
The runner is connected to a shaft that transmits the mechanical power to an electric generator. The generator then converts the mechanical energy into electrical energy, which is supplied for various uses.
Main Principle Behind Working
The Pelton turbine completely relies on the impulse action of water. The pressure energy is converted into kinetic energy before the water reaches the buckets, and the flow is always at atmospheric pressure when it strikes and leaves the buckets.
The water jet transfers its momentum to the bucket, and the change in momentum results in a large impact force that makes the runner rotate. This conversion is efficient because the bucket shape ensures smooth deflection of water without much energy loss.
The efficiency of the turbine depends on how effectively the water jet is deflected by the bucket and how little energy is lost during this deflection. Ideally, the water jet should leave the bucket with zero velocity, meaning all the kinetic energy of the water has been converted into mechanical energy.
Key Points of Working Principle
- It is based on the impulse principle.
- Only the kinetic energy of water is used for producing power.
- The pressure of water remains constant before and after striking the bucket.
- The direction of water flow changes, creating an impulse force.
- Water jet strikes tangentially on the runner’s buckets.
Example of Energy Conversion
If the water at a height of 300 meters flows through a penstock to the nozzle, the high head converts potential energy into kinetic energy, forming a fast-moving jet. When this jet hits the bucket, its velocity reduces, and the impact generates torque that rotates the wheel. This rotational motion is further used to run the generator.
Applications
- Used in high-head hydroelectric plants (above 300 meters).
- Common in mountainous regions with steep slopes.
- Ideal for small-scale and micro-hydro power generation.
- Suitable for locations with low water flow but high pressure.
Conclusion:
The Pelton turbine works on the impulse principle, where the high-velocity water jet strikes the buckets of the wheel, causing rotation by changing the direction of flow and momentum. The turbine converts the kinetic energy of water into mechanical energy efficiently. It is especially suitable for high-head and low-discharge hydro power sites. Because of its simple construction, durability, and high efficiency, the Pelton turbine is one of the most widely used turbines for hydroelectric power generation.