What is the working principle of Pelton wheel turbine?
Working principle of Pelton turbine is simple. When a high speed water jet injected through a nozzle hits buckets of Pelton wheel; it induces an impulsive force. This force makes the turbine rotate. The rotating shaft runs a generator and produces electricity.
How the Pelton wheel is stopped when rotation is not required?
Braking Jet Braking jet is used to stop the running wheel when it is not working.
How can the efficiency of Pelton wheel turbine be improved?
To maximise efficiency the jet must hit precisely the centre of each Pelton bucket. That way the jet gives the maximum drive to each bucket as noted earlier in the design of the buckets that the rotation of the turbine depends on the water jet velocity.
How does a Pelton wheel generate electricity?
The water in a Pelton turbine is moving quickly (high velocity head, figure 2) and the turbine extracts energy from the water by slowing the water down, which makes this an impulse turbine. When used for generating electricity, there is usually a water reservoir located at some height above the Pelton turbine.
Why Pelton turbine has high efficiency?
`Pelton wheel turbine has high overall efficiency. The first law in addition to the second law of motion are applied in this kind of turbine. In this turbine, the main advantage is that the whole process of the water jet hitting and leaving the runner occurs at atmospheric pressure.
What is the purpose of notch on the Pelton wheel bucket?
A notch made near the edge of the outer rim of each bucket is carefully sharpened to ensure a loss-free entry of the jet into the buckets, i.e., the path of the jet is not obstructed by the incoming buckets.
Why are Pelton turbines double cupped?
This balances the side-load forces on the wheel and helps to ensure smooth, efficient transfer of momentum of the fluid jet of water to the turbine wheel.
What affects efficiency of Pelton turbine?
There are several factors that may affect the power and efficiency of a Pelton model turbine, such as nozzle diameter, nozzle number, blade shape, the blade number, and water head [4].
What is deflector in turbine?
Jet deflectors have the function of diverting the water flow or part of it between the nozzle and the rotor in such a way that it does not hit the buckets. These may be used for an emergency stop or to regulate the turbine.
Is a Pelton turbine the most efficient?
Advantages of Pelton Wheel The Pelton wheel turbine is the most efficient available hydro turbine. It operates at a very flat performance curve. It works on low discharge and high head. It has fewer parts in comparison with Francis’s turbine, which has both guided vanes and fixed vanes.
How efficient is a Pelton wheel?
Pelton turbines can reach up to 95% efficiency, and even on ‘micro’ scale systems 90% peak efficiency is achievable. Also the efficiency is maintained at a high level even for part-flow rates, mainly because of the low-loss design of the spear-jet.
What is the pressure inside the turbine casing?
Most modern turbines, with steam pressures over 100 bar and ratings greater than 100 MW, have HP casings of double-shell design. This has been adopted because of the difficulty of designing a single casing to withstand the thermal and pressure stresses and yet is capable of flexible operation.
Why is Pelton wheel less efficient?
The overall efficiency of Pelton wheel is approximately 0.85. Because there are losses like mechanical friction loss, aerodynamic drag on the buckets or windage loss, friction along the inside walls of the buckets, nonalignment of the jet and bucket when bucket turns, back splashing and nozzle losses.
What is jet ratio in Pelton wheel?
Concept: In Pelton wheel jet ratio is defined as ratio of pitch diameter of wheel and jet diameter. i.e. J = D/d.
What is Pelton wheel turbine?
The Pelton wheel or Pelton wheel turbine is a tangential flow impulse turbine used for high heads of water. The Scientist who named Pelton wheel turbine is L A Pelton, an American Engineer.
What are the disadvantages of Pelton turbine?
Disadvantages of Pelton turbine Decrease in efficiency with time Components have large size Variation in the operating head is very difficult to control The operating head cannot be utilized even when the variation in the tail water level is relatively large when compared to total head
What is the function of the casing on a pelton wheel?
The Pelton wheel casing prevents the splashing of water and it will provide a discharge of water from the nozzle to the tailrace. The casing surrounding the wheel has no hydraulic function to perform, unlike the reaction turbine where the casing plays an important hydraulic function.
What are the parts of oil pressure Governor of Pelton turbine?
Governing of Pelton turbine is done by means of oil pressure governor, which consists of the following parts: Oil sump. The spear rod or needle. Pipes connecting the oil sump with the control valve and control valve with servomotor. The centrifugal governor or pendulum which is driven by a belt or gear from the turbine shaft.