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

Introduction:

This article is about to Pelton wheel turbine working principle, major components, and its different applications. So, a Pelton wheel water turbine is a well-known type of turbines from the impulse turbine category. So, the Pelton wheel turbine uses to generate electrical energy in hydropower plants. It is a high head turbine. Lester Allan invented the Pelton wheel turbine in the 1870s.

In the Pelton wheel turbine, water flow is tangential (the jet of water hits the wheel tangentially). These types of turbines are suitable for low water flow and high pressure (head) applications. It has a big runner or wheel with a “hub” (turbine blade) to absorb underwater energy. The blades are used in pairs to balance the wheels and work efficiently properly—the pressure at the outlet and inlet of this atmospheric pressure. There is a moveable spear jet at the entrance of the turbine.

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 stage of the turbine, unlike gas turbines which are worked with compressible liquids.

pelton wheel turbine

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 is stuck in high places. From there it reaches the nozzle of the Pelton wheel turbine via a pressure pipe (penstock). So, the nozzle improves the water’s kinetic energy and guides it in the kind of a jet.

The flow of water is tangent to the direction of the impeller. The nozzle directs a powerful water jet into a sequence of blades attached to the ends of the wheel. The nozzles direct a powerful jet of water into a sequence of blades attached to the ends of the wheel. Hence, the impeller revolves at an excessive velocity, and the amount of water that hits the nozzle or blade is regulated with the help of a spear 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 a “U-turn” slows the water down, causing it to drain off the other side of the bucket slowly. The impulse of the water is shifted to the Pelton wheel turbine. This “impulse” works in the turbine. For the highest efficiency and performance, this turbine system is planned to spray the jet of water at two times the speed of the blade.

Pelton turbine working, hydraulic head

Finally, a generator connected to the axis of the shaft of the Pelton wheel turbine converts the mechanical energy of the impeller (rotational energy) into electrical energy.

Main components of the Pelton Wheel Turbine:

The main components of the Pelton wheel turbine are given below.

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 does not act hydraulic functions. But you have to protect your impeller from different accidents. The casing also prevents the water from splashing.
  • The housing is usually manufactured by fabricated or cast parts.

3) Runner:

  • The impeller is a revolving component. A runner is a circular disc with a large number of blades evenly distributed around it.

4) Buckets:

  • The blade consists of two hemispherical shells that are connected with each other. Each blade has a wall between two hemispherical bowls called partitions.
  • The splitter divides the water flow hitting the bucket into two equal parts, and the water runs off the outside edge of the blade.
  • The construction of the vanes provides that the water jet hits the blades with a deflection angle of 160 to 170 degrees.
  • Pelton wheel turbine blades are made of stainless steel, bronze, cast steel, or cast iron.

5) Nozzle:

  • The nozzle is a circular controller device that guides the water flow in the design path and adjusts the water flow.
  • This water hits the bucket in a stream. 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 runner is observed to rotate for a considerable time before stopping.
  • A small nozzle directs the water jet behind the vanes so that the runner can rest for a short time.
  • It uses as a brake to slow down the runner’s speed of the turbine.
  • Breaking jet includes in the major components of the Pelton wheel turbine.

Advantages and Disadvantages of Pelton Wheel Water Turbine:

Advantages:

  • 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:

  • 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:

  • 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.

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. So, these turbines are most efficient at low head. The assembly of these turbines is very easy.

See More:

1) Different types of Turbine

2) Reaction Turbine and its types

3) Impulse Turbines

4) Francis Turbine

5) Kaplan Turbine

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