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A wheel power divided by the initial jet power, is the turbine efficiency, η = 4u(V i − u)/V i 2. It is zero for u = 0 and for u = V i. As the equations indicate, when a real Pelton wheel is working close to maximum efficiency, the fluid flows off the wheel with very little residual velocity. [11]
With the help of these equations the head developed by a pump and the head utilised by a turbine can be easily determined. As the name suggests these equations were formulated by Leonhard Euler in the eighteenth century. [1] These equations can be derived from the moment of momentum equation when applied for a pump or a turbine.
Specific speed N s, is used to characterize turbomachinery speed. [1] Common commercial and industrial practices use dimensioned versions which are of equal utility. Specific speed is most commonly used in pump applications to define the suction specific speed —a quasi non-dimensional number that categorizes pump impellers as to their type and proportions.
Surprisingly, the turbine now moved faster. That was Pelton's great discovery. In other turbines the jet hit the middle of the cup and the splash of the impacting water wasted energy." [6] Experimenting and modelling, Pelton improved upon the efficiency of the Knight wheel (developed earlier by the Knight Foundry at nearby Sutter Creek).
A turbine (/ ˈ t ɜːr b aɪ n / or / ˈ t ɜːr b ɪ n /) (from the Greek τύρβη, tyrbē, or Latin turbo, meaning vortex) [1] [2] is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced can be used for generating electrical power when combined with a generator. [3]
The 1269 MW power plant is operated by Grande Dixence SA. [1] Production began in 1998, with two world records set upon its completion: the world's most powerful Pelton turbine as well as the highest head used to produce hydro-electric energy. A penstock rupture in 2000 forced the closure of the power plant and it was operational again in 2010.
The resulting impulse spins the turbine runner, imparting energy to the turbine shaft. Water exits with very little energy. Turgo runners are extremely efficient A Turgo runner looks like a Pelton runner split in half. For the same power, the Turgo runner is one half the diameter of the Pelton runner, and so twice the specific speed.
The speeds of different turbine units range from 70 to 1000 rpm. A wicket gate around the outside of the turbine's rotating runner controls the rate of water flow through the turbine for different power production rates. Francis turbines are usually mounted with a vertical shaft, to isolate water from the generator.