Introduction to Pelton wheel turbine
In the last blog, we discussed the Classification of turbines according to various types. In our today’s blog, we will discuss Components of the turbine namely Nozzle, Flow regulating arrangement, Runner, Buckets, Splitters, Casing, Breaking Jet. also the working of the Pelton wheel turbine.
The Pelton wheel was invented by Lester Allan Pelton, who was the father of hydroelectric power. He created the first water wheel to take advantage of kinetic energy. He developed the first Pelton wheel turbine in the 1870s
Pelton wheel turbine is constructed in the high hilly area because it is preferable for the high head. The high head is considered when the height of standing water is above 300 meters. Sometimes in the high head, water flow is low (flow is nothing but the rate of water at which it falls on the turbine).
Pelton wheel turbine is an impulse turbine. Impulse is a pattern in which water flows. Water pressure is converted into kinetic energy, and a jet is formed, which drives the wheel. In short, impulse flow only has kinetic energy. For this kind of flow, Impulse turbines are used.
In our today’s blog, we will discuss Components of the turbine namely Nozzle, Flow regulating arrangement, Runner, Buckets, Splitters, Casing , Breaking Jet. also the working of the Pelton wheel turbine.
Components of Pelton wheel turbine
Following are the components used for a Pelton wheel turbine.
- Nozzle
- Flow regulating arrangement
- Runner
- Buckets
- Splitters
- Casing
- Breaking jet
Specification of components and their use varies according to the requirement of generation and the size of the plant.
These are the components used inside a casing of a Pelton wheel turbine. The assembly of these components is known as a Pelton wheel turbine. These small parts help in smoothing operations, reduce losses, and increase the process’s efficiency.
Now we will discuss these components and their functions in detail.
Nozzle
A nozzle is simply a narrow tube with a varying cross-sectional area, which serves to control the fluids. That is why it is connected to the end of the pipe.
Also, it is used to control the flow rate, speed, and pressure of water that flows from penstock. The nozzle is connected between penstock and turbine so that it can act as a controlling device.
The whole assembly of the nozzle is arranged. Water from the source (dam or reservoir) is carried through the penstock, and the penstock is connected to a nozzle where the high-speed water jet is formed. The output of the nozzle is connected to the turbine.
Flow regulating arrangement
The flow is regulated by using a spear. The spear is a movable needle that is placed inside the nozzle.
As you can imagine nozzle is already a narrow tube. If we place a spear inside the nozzle according to the position of the spear, the water flow varies.
The direction of movement of a spear is back and forth in an axial direction. If the direction of the spear is forward, then the flow gets reduced, and if the direction of a spear is backward, the flow rate increases.
Runner
Runner, it is not a person who runs neither door runner. In the case of a hydroelectric power plant, the runner is a circular disc on the periphery. The number of buckets is mounted with equal spacing.
A runner is the specific part of a turbine that provides a motion wheel when water strikes the turbine. It is the heart of the turbine where the water energy is transferred into the rotational force that is mechanical energy that drives the generators.
Buckets
No, no, it is not the same thing we use to carry water.
Buckets are cup-shaped blades that are mounted on a runner. The buckets are only used in the Pelton wheel turbine. The primary function of buckets is when the high-speed jet injected from the nozzle hits the buckets of the Pelton wheel turbine. This causes the creation of impulsive force; this same force is responsible for the turbine rotating.
Each bucket splits the water jet in half so that thrust on the wheel gets balanced. The buckets used are generally double hemispherical or double ellipsoidal. These buckets are made from cast iron or steel, or bronze to withstand all the pressure of the water jet.
Splitters
The primary function is to provide a dividing wall for each bucket; however, this separated buckets into two parts. Due to the splitter turbine being rotated with more velocity and also the impulse force is get created.
Casing
The casing is the protective covering of the turbine. The casing prevents the splashing of water while working. While the other function of the casing is that it helps to discharge the water that is wastage from turbine wastage in the sense of no use at tailrace.
Inside the covering runner, buckets, breaking jets, the nozzle is placed. High strength material such as cast iron or cast steel is used for casing to sustain any physical harm.
Breaking Jet
The function of breaking jet is, as its name suggests, it breaks the jet of water; breaking jet stops the runner wheel when a turbine is not working or when we need to stop the turbine.
As you can see in the figure, the breaking jet is placed in the opposite direction of the nozzle and other water arrangements. Whenever the condition occurs in which the nozzle inlet is closed, placing the spear in the forwarding direction inside the nozzle, then the water jet is stopped on buckets.
As we all know, when we switch off the button of the fan, the blades still move due to the same inertia thing that happens with the turbine’s runner. After blocking the water jet, it continues to move.
To stop the turbine, a break nozzle directs the jet of water on the back of buckets to stop the wheel friction freely or without causing any damage. The water jet we induce for this purpose is known as breaking jet.
Working of Pelton wheel turbine
If you understood the function of components, then working is just a combination of all these functions in a proper sequence.
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Water stored in reservoir or dam is at the high head, the turbine, and all other assembly is at the lower end.
Water is transferred from the high head to the lower end with the help of a long conduit of the penstock.
Nozzle arrangement is at the end of the penstock, which increases pressure and water flow that strikes a bucket mounted on a runner.
In technical language, accelerated water flows out a high-speed jet with high velocity from the nozzle’s output, which strikes on a runner that converts water energy into mechanical energy.
Due to the shape of buckets, the jet gets split. This directed jet changes its direction by taking the U-turn and falling into the tailrace through the casing.
In this way, water completes its cycle, and electricity is getting generated.
In our next blog, I will discuss the Francis turbine. For more updates, stay connected with our website.
