What is Pelton Wheel Turbine? | How does a Pelton Wheel Turbine work?

The turbines are most commonly used all over the world for the production of electricity. There are multiple types of turbines that design according to the flow rate and head requirements. A Pelton wheel water turbine is also a well-known type of turbine from the impulse turbine category. This article is about to Pelton wheel turbine working principle, components, and its different applications.

What is a Pelton Wheel?

A turbine in which the water jet hits the wheel tangentially is called a Pelton wheel turbine. In simple words, in the Pelton wheel turbine, the water strikes the wheel or impeller in a tangential direction. An American developer Lester Allan Pelton invented the Pelton wheel turbine in the 1870s.

A Pelton wheel turbine is a best appropriate turbine for low water flow and high head (pressure) applications. This turbine has a big impeller or wheel that has multiple numbers of blades to absorb underwater energy. The blades are used in pairs to balance the wheels and work efficiently properly.

This turbine has atmospheric pressure at the suction and discharge section. There is a moveable spear jet at the entrance of the turbine. The Pelton wheel uses to generate electrical energy in hydropower plants. 

pelton wheel turbine, pelton wheel

Most liquids and water are almost incompressible, and almost all of the accessible energy is obtained in the early stages of the turbine. So, the Pelton wheel turbine has one only stage of the turbine, unlike gas turbines which are worked with compressible liquids (such as gas). Therefore, it extracts all the energy of the water in the early stage. 

Read also: Different types of Impulse Turbines

Pelton Wheel Turbine Working Principle

The working principle of the Pelton Wheel turbine is straightforward. 

Pelton wheel turbine working
                     Fig: Electricity Production Process

In the hydroelectric power plant, first of all, the water stores at high places (as shown in the above diagram). The water stored at the high head has maximum potential energy.

Pelton turbine working, hydraulic head

During the working of the Pelton wheel turbine, the water from the high head transfers into the nozzle of the turbine via a pressure pipe (penstock). As the water reaches in the nozzle,  the nozzle converts the potential energy of the water into kinetic energy and improves the water’s kinetic energy. After this, the nozzle guides the water toward the impeller in the kind of a jet.

The flow of the water jet is tangent to the direction of the impeller or wheel. As the nozzle directs a powerful water jet toward the impeller blades, the water jet hits the blades. The impeller starts revolving at an excessive velocity, and the amount of water that hits the blades is regulated with the help of a spear present in the nozzle.

When the jet of water hits the buckets of the Pelton water wheel turbine, the water puts pressure on the buckets, and its kinetic energy reduces. Due to the spherical design of the impeller blades, the water jet changes its direction and takes a “U-turn” and falls into the tailrace.

During this process, the momentum of the water is shifted to the Pelton wheel turbine. This “momentum” works on the turbine. For the highest efficiency and performance, this turbine system designs in such a way that the velocity of the water jet is two times more than the velocity of the impeller blade.

At the last, a generator is connected to the impeller shaft which converts the mechanical energy of the impeller (rotational energy) into electrical energy.

For a better understanding, watch the following video:

Main Components of the Pelton Wheel

The main components of the Pelton wheel are given below:

  1. Spear
  2. Casing or Housing
  3. Runner or Impeller
  4. Impeller Blades
  5. Nozzle
  6. Breaking jet

Pelton wheel turbine components, turbine wheels

1) Spear

  • The spear attaches to the nozzle. The main objective of the spear is to control the water flow that hits the runner blades. The above-given diagram shows a nozzle with a spear.
  • It is a conical needle that is available inside the nozzle. It can function automatically axially or with a handwheel.
  • The water flow reduces when the movement of the spear is forward. At the same time, the water flow rises when the movement of the spear is backward.
  • The primary purpose of this component is to control or adjust the amount of water flowing through the nozzle, as shown in the figure.

2) Casing or Housing

  • Pelton water wheel turbine housing doesn’t play any hydraulic function. It doesn’t perform any role in the production of electricity. It just works as a safety guard for the internal components of the turbine. Because you have to protect your impeller from different accidents. The casing also prevents the water from splashing. 
  • The housing or casing is usually manufactured by fabricated or cast parts.
  • It provides safety to the internal parts of the turbine if something falls on the body. 

3) Runner or Impeller

  • The impeller or runner is a revolving component. A runner is a circular disc with a large number of blades evenly distributed around it.
  • It directly connects with the generator through a shaft.

4) Impeller Blades

  • The blade consists of two hemispherical shells that are connected with each other. Each blade has a wall between two hemispherical bowls known as a splitter.
  • The splitter divides the water jet hitting the impeller blades into two equal parts, and the water runs off the outside edge of the blade.
  • The impeller blades design in such a way that the water jet coming from the nozzle hits the blades with a  deflection angle of 160 to 170 degrees.
  • These blades are made of stainless steel, bronze, cast steel, or cast iron.

5) Nozzle

  • It is a static component of the Pelton Wheel turbine.
  • The main objective of the nozzle is to convert the potential energy of the water into kinetic energy.
  • The nozzle is a circular guide device that directs the water flow in the design path and adjusts the water flow.
  • A nozzle produces a jet of water that has high kinetic energy. It guides the water jet toward the impeller blades or buckets. A spear runs axially within the nozzle.
  • The nozzle increases the K. E of the water, hitting the bucket or blade fixed to the impeller.

6) Breaking jet

  • When the turbine needs to be stopped, then the nozzle is fully fastened. Due to the inertia, the impeller is observed to rotate for a considerable time before stopping.
  • A small nozzle directs the water jet behind the blades so that the impeller can rest for a short time.
  • It works as a brake to slow down the turbine impeller’s speed.
  • Breaking jet includes in the major components of the Pelton wheel turbine.

Read also: Different types of Turbines

Efficiency of Pelton Wheel Turbine

Following are some formulas that are helpful to calculate different efficiencies of the Pelton wheel.

1) Mechanical Efficiency

The power delivered by the runner to the shaft is known as mechanical efficiency. The below-given formula uses to calculate the mechanical efficiency.  

mechanical efficiency of Pelton wheel turbine

2) Hydraulic Efficiency

The power generated by the turbine runner divided by the input power delivered to the runner blades is known as hydraulic efficiency. 

The below-given formula calculates the Hydraulic Efficiency of the Pelton wheel turbine:

hydraulic efficiency

3) Volumetric Efficiency

The fluid’s actual quantity on the impeller buckets divided by the fluid’s net quantity provided to the turbine is called volumetric efficiency. The formula for the volumetric efficiency is given below:

volumetric efficiency of pelton wheel

4) Overall Efficiency

The available power at the turbine’ shaft divided by the input power of the turbine inlet is known as the overall efficiency of the Pelton wheel turbine. The overall efficiency of the Pelton wheel turbine is given below:

overall efficiency

Mathematical Formula of Pelton Wheel

The below-given formula can calculate the specific speed of a Pelton wheel:

specific speed

The ratio between the water flow velocity at the turbine inlet to the inlet’s energy head is known as the flow ratio.

 In the above equation;

ρ = Density (kg/m3)

H = Water Head (m)

P = Power (W)

n = Frequency of rotation

Advantages and Disadvantages of Pelton Wheel Water Turbine

Advantages of Pelton Wheel Turbine: –

  • Pelton wheels are the most efficient hydraulic turbine.
  • The efficiency curve is very flat.
  • Each blade divides the water flow into two parts and balances out the side force or the thrust from the wheel and bearing.
  • Works at low discharge and high head (pressure).
  • There is a tangential flow. That is, there is a radial flow or an axial flow.
  • The assembly of Pelton water wheel turbines is very easy.
  • There is no water erosion as the jet of water only hits certain parts of the impeller.
  • This turbine has fewer parts compared to Francis turbines with fixed blades and guides.
  • It has a very high overall efficiency.
  • 1st and 2nd law of Newton both are applicable in the case of these impulse turbines.
  • The key benefit of these turbines is that the entire process of the water entering and leaving the impeller is carried out under atmospheric pressure.

Disadvantages of Pelton Wheel Turbines: –

  • Efficiency decreases rapidly over time.
  • The required size of the turbine power chamber, generator, and runner is large.
  • These turbines are less dependable as compare to cross-flow turbines.
  • The high head makes it difficult to control changes in operating altitude.
  • These turbines require a high head.

Applications of Pelton Wheel Turbines

  • Pelton wheel turbine works cleanly. Therefore, it can be settled in drinking water supply systems.
  • If you need water above the water inlet, the installment of this turbine is an easy and efficient way to pump water.
  • Pelton wheels are using in hydropower plants with high water levels between 150 m and 2000 m. In hydropower plants, Pelton turbines drive connected generators, which convert the mechanical energy of this turbine into electrical energy.

Difference between Pelton Wheel Turbine and Crossflow Turbine

           Pelton Turbine               Crossflow Turbine
Lester Allan invented it in the 1870s.  Anthony Michelle invented it in the 1903s.
It is a high head turbine. It is a low head turbine.
These turbines have a low flow rate These have a high flow rate.
It has high efficiency as compared to a cross-flow turbine. It has low efficiency than the Pelton wheel turbine.

FAQ Section

Who Invented Pelton wheel turbine?

In 1870, an American developer Lester Allan Pelton invented the Pelton wheel turbine.

What kind of turbine is a Pelton wheel turbine?

A Pelton wheel turbine is a famous kind of impulse turbine. In this turbine, the water jet moves tangentially to the impeller or wheel. The water jet in a Pelton turbine moves fast and the turbine obtains energy from the water by reducing its speed. And this process makes it an impulse turbine.  

Which turbine use for high head and low flow rate?

A Pelton wheel turbine is mainly used for high head and low flow rate applications.

What are the parts of the Pelton Wheel Turbine?

The Pelton wheel turbine has the following parts:

  1. Breaking jet
  2. Nozzle
  3. Impeller Blades
  4. Spear
  5. Runner
  6. Casing or Housing
  7. Spear
  8. Handwheel

What is the efficiency of Pelton turbine?

The efficiency of a Pelton turbine can reach up to 95%.  In the case of micro-scale hydropower plants, 90% highest efficiency is attainable by the Pelton turbine.

How much power can a Pelton wheel produce?

A Pelton wheel can produce up to 16.89 watts of power.

What are the Pelton wheel turbine used?

The Pelton wheel turbines are used for producing electricity in the hydroelectric powerplant. The Pelton turbine is mainly used in applications that have high head and low flow rates. These turbines work cleanly due to that these turbines can be settled for drinking water supply systems.

This whole article is about the Pelton wheels turbine. So, these are types of turbines that work more efficiently in the hydroelectric powerplant. Nowadays, these turbines most widely used in hydroelectric power plants for the production of electricity. Because these turbines are most efficient at low head. These turbines have an easy assembly.

If you need any more help related to this topic, you can let me know in the comment box. I will try my best to clear your concepts. And if you like the article then don’t forget to like and share it.

Read More
  1. Types of Reaction Turbines
  2. Different types of Impulse Turbines
  3. Working of Francis Turbine
  4. Working of Kaplan Turbine
  5. Types and working of Crossflow Turbine

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