Fabrication Of Pelton Wheel Turbine | Mechanical Project
Fabrication Of Pelton Wheel Turbine | Mechanical Project
A Pelton-wheel impulse turbine is a hydro mechanical energy conversion device which converts gravitational energy of elevated water into mechanical work. This mechanical work is converted into electrical energy by means of running an electrical generator. The kinetic energy of the Water-jet is directed tangentially at the buckets of a Pelton-wheel. The Water-jet strikes on each bucket’s convex profile splitter and get split into two halves. Each half is turned backwards, almost through 180° relative to the bucket on a horizontal plane. Practically this angle may vary between 165° to 170°. Normally all the jet energy is used in propelling the rim of the bucket wheel. Invariably some jet water misses the bucket and passes onto the tail race without doing any useful work.
This hydro device is a good source of hydro-electrical energy conversion for a high water head. The present work in this research paper deals with some advanced modifications in the conventional Pelton-wheel so that it can be used for low-head and heavy-discharge applications. Both kinetic and potential energy of the water source is consumed by the runner wheel. Considerable gravitational effect of the water jet is exploited by means of some modifications in a conventional Pelton wheel. A comparatively heavy generator can be run by this modified Pelton-wheel turbine under low head and heavy-discharge conditions. The modified features provide enough promising opportunities to use this turbine for Mini and Micro hydro power plants.
Hydro-power is an ancient resource of green electricity. Water from the rivers, lakes, ponds and plants evaporates due to sunlight heating. This results in the rise of water vapor against the gravitational pull of the earth. In the atmosphere, it cools and condenses into drops of rain and snow, which falls on hills and mountains. A considerable amount of solar energy is still retained in the water in the form of gravitational potential energy. Therefore, solar energy is the ultimate source of hydro energy which basically represents stored gravitational energy. It is understood that water continuously flows on the earth surface to reach the sea. This happens because of the spherical shape of the earth that tenders a natural gravitational pull on surface water.
The amount of stored hydro energy is directly proportional to the height and amount of the water above sea level. A turbine is the mechanical device which consumes the hydro energy of an elevated water level by means of pressure energy (in the case of a reaction turbine) or by means of kinetic energy (in the case of an impulse turbine). The hydro energy consumed by a turbine is passed to the electrical generator shaft in the form of mechanical energy. A Pelton-wheel is a tangential flow free-jet-impulse turbine named after an American engineer, Lesser Pelton. It is simple, robust and the only hydraulic turbine which operates efficiently on high heads in excess of 450 m. The working pressure in this turbine remains atmospheric only. It possesses simple construction and smooth running features with good performance characters.
WORKING PRINCIPLE PELTON-WHEEL
The modified gravitational Pelton-wheel is designed in such a way that it consumes the potential head H1 between P1 and P5 in the form of stored water weight in the bucket-cups. The kinetic head is consumed during the striking of the jet on bucket. The location and position of the additional bucket-cup.
On the conventional Pelton-wheel is such that it consumes jet water at P1. The weight of this stored Water per second in the bucket-cup is the amount of potential energy per second from water jet. Further, This potential energy is converted into kinetic energy as this water filled bucket freely (assumed) falls During P1 to P5 position of the wheel. It is also possible to extract kinetic energy from the penstock nozzle discharge by means of a jet strike on the conventional Pelton-wheel vanes of the runner.
ADVANTAGES OF THE PELTON WHEEL TURBINE
- Among the most efficient of hydro turbines
- It operates with a very flat efficiency curve
- Ideal for operation in silted water.
- Each bucket splits the water jet in half, thus balancing the side-load forces or thrust on the wheel and thus the bearings.
1) Pelton wheels are the preferred turbine for hydro-power, when the available water source has relatively high hydraulic head at low flow rates, where the Pelton wheel is most efficient.
2) Thus, more power can be extracted from a water source with high-pressure and low-flow than from a source with low-pressure and high-flow, even when the two flows theoretically contain the same power. Also a comparable amount of pipe material is required for each of the two sources, one requiring a long thin pipe, and the other a short wide pipe.
3) Pelton wheels are made in all sizes. There exist multi-ton Pelton wheels mounted on vertical oil pad bearings in hydroelectric plants. The largest units can be up to 200 megawatts. The smallest Pelton wheels are only a few inches across, and can be used to tap power from mountain streams having flows of a few gallons per minute. Some of these systems use household plumbing fixtures for water delivery.
4) These small units are recommended for use with thirty meters or more of head, in order to generate significant power levels. Depending on water flow and design, Pelton wheels operate best with heads from 15 meters to 1,800 meters, although there is no theoretical limit.
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