How are turbomachines classified?
Turbomachines can be classified in different categories depending on their geometry and the way they work. We can find:
Today we are going to focus on PELTON turbines.
You have probably heard about this part before. After all, Pelton Turbines have been with us since the 1870s when Lester Allan Pelton invented this wheel that today we are going to get to know in-depth.
Since then, of course, these turbines have been incorporating significant improvements by other inventors. Here we are going to study their characteristics and solve all the doubts about these very special parts.
In this post you will learn:
- What is a Pelton Turbine
- What are its most important parts
- How it works
- Use and classifications
What is a Pelton Turbine?
Simply put, a Pelton Turbine is an impulse hydro turbine generally used in hydroelectric power plants with high vertical heads.
To understand these parts properly, we must pay attention to the definition of a turbomachine: It is a machine whose main element is a rotor through which a fluid passes steadily, changing its quantity of movement due to the action of the machine. In this way, a transfer of energy is obtained between the machine and the fluid, which can be either in the machine-fluid or fluid-machine direction.
Pelton Turbines are a further development of the traditional water wheel. Their aim is clear: To convert the hydraulic energy in the impulse of one or more jets of water at a very high speed into mechanical energy.
They are high-performance parts, as they are 92% efficient in terms of hydraulic energy use.
5 advantages of Pelton Turbines:
- They are useful for high jumps and relatively small flow rates.
- They are more robust.
- They are less prone to erosion of their buckets.
- Easier to repair.
- Very efficient.
Parts of a Pelton Turbine
Learn about the main components of these turbines:
- A pipe is known as a pressure gallery to convey water to the turbine from great heights.
- Flow regulation arrangement and nozzle that accelerates the speed of the inlet flow.
- Rotor and blades are responsible for converting the force of the water into mechanical energy.
- The casing in which the rotor is housed. It is filled with air at atmospheric pressure.
- The braking jet is used to stop the running wheel when it is not running. This occurs when the nozzle inlet is closed with the help of a lance and then the water jet is stopped in the buckets.
How do these parts work?
The Pelton Turbine is connected to a pressure pipe from a high dam. Water enters one or more nozzles causing a violent acceleration in the water flow. At this point, the water jet hits several bowl-shaped blades (bucket) causing the turbine and shaft to rotate.
The turbine shaft is connected to a generator that produces electrical energy.
In earlier versions of these turbines, the water still had a high velocity when it left the wheel, so much of the kinetic energy of the water was not fully exploited.
Its inventor Pelton designed the blades so that the water jet turns almost 180° after leaving the buckets. The water leaves the turbine wheel at a very low speed.
For more information about desalinated water see this article.
What is the optimum number of buckets that a turbine should have?
When looking at the pictures of these parts, the turbine buckets stand out. Is there an exact number of buckets that should be incorporated?
This question has been raised by many manufacturers. According to a study by Lancaster University Renewable Energy Group and Fluid Machinery Group “By identifying the best combination of the radial and angular position for each number of buckets, it is shown that reduction in the number of buckets beyond the limit suggested by the available literature can improve the runner efficiency and be beneficial from the manufacturing complexity and cost point of view.”
In a nutshell: the reduction of the number of buckets reduces the complexity and the cost of runner manufacturing.
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