Water turbine

Water turbines were developed in the 19th century and were widely used for industrial power prior to electrical grids.

This additional component of motion allowed the turbine to be smaller than a water wheel of the same power.

Two helix-turbine mill sites of almost identical design were found at Chemtou and Testour, modern-day Tunisia, dating to the late 3rd or early 4th century AD.

The horizontal water wheel with angled blades was installed at the bottom of a water-filled, circular shaft.

[1] Fausto Veranzio in his book Machinae Novae (1595) described a vertical axis mill with a rotor similar to that of a Francis turbine.

In the 18th century, a Dr. Robert Barker invented a similar reaction hydraulic turbine that became popular as a lecture-hall demonstration.

[3] The only known surviving example of this type of engine used in power production, dating from 1851, is found at Hacienda Buena Vista in Ponce, Puerto Rico.

He also conducted sophisticated tests and developed engineering methods for water turbine design.

In 1876, John B. McCormick, building on Francis's designs, demonstrated the first modern mixed-flow turbine with the development of the Hercules turbine, initially manufactured by the Holyoke Machine Company and subsequently improved upon by engineers in Germany and the United States.

[6][7] Water turbines, particularly in the Americas, would largely become standardized with the establishment of the Holyoke Testing Flume, described as the first modern hydraulic laboratory in the United States by Robert E. Horton and Clemens Herschel, the latter of which would serve as its chief engineer for a time.

[8][9] Initially created in 1872 by James B. Emerson from the testing flumes of Lowell, after 1880 the Holyoke, Massachusetts hydraulic laboratory was standardized by Herschel, who used it to develop the Venturi meter, the first accurate means of measuring large flows, to properly measure water power efficiency by different turbine models.

[13][14]: 100 Around 1890, the modern fluid bearing was invented, now universally used to support heavy water turbine spindles.

It was an evolution of the Francis turbine and revolutionized the ability to develop low-head hydro sites.

[15][16] Inspired by the high pressure jet systems used in hydraulic mining in the gold fields, Knight developed a bucketed wheel which captured the energy of a free jet, which had converted a high head (hundreds of vertical feet in a pipe or penstock) of water to kinetic energy.

Since the turbine is spinning, the force acts through a distance (work) and the diverted water flow is left with diminished energy.

This type of system is used in El Hierro, one of the Canary Islands: "When wind production exceeds demand, excess energy will pump water from a lower reservoir at the bottom of a volcanic cone to an upper reservoir at the top of the volcano 700 meters above sea level.

When demand rises and there is not enough wind power, the water will be released to four hydroelectric turbines with a total capacity of 11 MW.

Affinity laws allow the output of a turbine to be predicted based on model tests.

A miniature replica of a proposed design, about one foot (0.3 m) in diameter, can be tested and the laboratory measurements applied to the final application with high confidence.

Differential head and flow can be plotted for a number of different values of gate opening, producing a hill diagram used to show the efficiency of the turbine at varying conditions.

A variety of flyball systems, or first-generation governors, were used during the first 100 years of water turbine speed controls.

[20] A wicket gate, or guide vane, is a ring of gates (or vanes) surrounding a water turbine which control the flow of water entering it; varying the aperture between them manages the rate of the turbine's spin, and thereby the amount of electricity generated.

Having a higher chromium concentration in the steel alloys allows for a much longer lifespan of the turbine blades.

[22] Along with corrosion resistance and strength, weld-ability and density are important criteria for turbine blade material selection.

[22] The SS(13Cr-4Ni) has been shown to have improved erosion resistance at all angles of attack through the process of laser peening.

[24] Turbines are designed to run for decades with very little maintenance of the main elements; overhaul intervals are on the order of several years.

Normal wear and tear includes pitting corrosion from cavitation, fatigue cracking, and abrasion from suspended solids in the water.

Old turbine runners may have a significant amount of stainless steel added this way by the end of their lifetime.

[25] Other elements requiring inspection and repair during overhauls include bearings, packing box and shaft sleeves, servomotors, cooling systems for the bearings and generator coils, seal rings, wicket gate linkage elements and all surfaces.

Dams alter the natural ecology of rivers, potentially killing fish, stopping migrations, and disrupting livelihoods.