The Poncelet wheel is a type of

waterwheel A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a wheel (usually constructed from wood or metal), with a number of blades or buckets ...

invented by

Jean-Victor Poncelet Jean-Victor Poncelet (; 1 July 1788 – 22 December 1867) was a French engineer and mathematician who served most notably as the Commanding General of the École Polytechnique. He is considered a reviver of projective geometry, and his work ''Tr ...

while working at the École d'Application in

Metz Metz ( , , lat, Divodurum Mediomatricorum, then ) is a city in northeast France located at the confluence of the Moselle and the Seille rivers. Metz is the prefecture of the Moselle department and the seat of the parliament of the Grand E ...

. It roughly doubled the efficiency of existing undershot waterwheels through a series of detail improvements. The first Poncelet wheel was constructed in 1838, and the design quickly became common in France. Although the design was a great improvement on existing designs, further improvements in

turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating e ...

design rendered the Poncelet wheel obsolete by the mid-century.

Design

Traditional undershot waterwheels consisted of a series of flat blades fixed to the rim of a wheel. The blades were typically radial, i.e. mounted so that they pointed straight out along the

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

of the wheel. When water from the

headrace A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a wheel (usually constructed from wood or metal), with a number of blades or bucke ...

flowed past the wheel, it hit the blades, and some of its

kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...

was converted into

work Work may refer to: * Work (human activity), intentional activity people perform to support themselves, others, or the community ** Manual labour, physical work done by humans ** House work, housework, or homemaking ** Working animal, an animal t ...

by the wheel. However, much of the water was reflected off the blade and in the resulting turbulence a lot of the energy was converted to heat. This process was not efficient; much of the original velocity in the water remained in it, meaning that

was not being captured. Typical efficiency of water wheels exploiting only the kinetic energy was around 30%.Reynolds, pg. 227 These wheels are called stream water wheels, or kinetic water wheels. Instead, undershot water wheels are used in low head sites, like less than 1.5 m, and they also exploit the potential energy of the flow, with efficiencies of up to 84%. Typical examples are

Sagebien

Alphonse Eléonor Sagebien (1807-1892) was a French Hydrology, hyd ...

and Zuppinger undershot water wheels. Jean Charles de Borda was the first to directly characterize the efficiency of waterwheels by comparing the velocities of water before and after meeting the wheel. Poncelet was familiar with this work and started looking for ways to improve the design. He stated that "After having reflected on this, it seemed to me that we could fulfil this double condition by replacing the straight blades on ordinary wheels with curved or cylindrical blades, presenting their concavity to the current."O'Connor and Robertson His design used curved blades positioned so the water met the blade flat to its edge instead of the side. This eliminated the "bounce" that robbed power from the typical design. The water rose up into the channel between the blades for about 15 degrees of rotation, and then drained back out after another 15 degrees, where it dropped out of the channel, over the curve of the blade, imparting further impulse. By the time it left, the water had almost no velocity left. He estimated that practical wheels would reach as high as 80% for low velocity streams, and 70% for high velocity ones that fill the buckets too quickly.Reynolds, pg. 261 Poncelet developed the design in 1823 and built a small model in 1824 that demonstrated 72% efficiency. Several commercial models followed, including a large installation in Metz that delivered 33% more power than the traditional wheel it replaced, in spite of implementing only some of the design . He published a longer paper on the design in 1826, and a much more detailed version in 1827. The design won a Prix de Mecanique from the

French Academy of Sciences The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV of France, Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific me ...

, who were funding development of the waterwheel and also awarded several other designs similar awards. Poncelet wheels became common in France and Germany, where undershot designs were common. However, the large-scale installation of

steam engine A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be trans ...

s and

water turbine A water turbine is a rotary machine that converts kinetic energy and potential energy of water into mechanical work. Water turbines were developed in the 19th century and were widely used for industrial power prior to electrical grids. Now, t ...

s led to the Poncelet wheel falling from use.

References

Notes

Bibliography

* Terry Reynolds
"Stronger Than a Hundred Men: A History of the Vertical Water Wheel"
JHU Press, 2003

WaterWheelFactory * J. B. Calvert

23 July 2003 * J. J. O'Connor and E. F. Robertson

{{refend * Quaranta, E. and Muller, G, agebien and Zuppinger water wheels for very low head hydropower applications Journal of Hydraulic Research, 2017 * Quaranta, E. and Revelli, R FD simulations to optimize the blade design of water wheels Drinking Water engineering and science, 10, 27-32, 2017. https://www.drink-water-eng-sci.net/10/27/2017/dwes-10-27-2017.pdf Hydropower

Design

See also

References

Notes

Bibliography