Turbine

The idea of using naturally moving water or air to help do work is an ancient one. Waterwheels and windmills are the best examples of ancient mankind's ability to capture some of nature's energy and put it to work. The Romans were grinding corn with a waterwheel as early as 70 B.C., and modern-type windmills were being used in Persia around A.D. 700. Both are ancestors of the turbine. Both have large surfaces (paddles, buckets, or a sail) at their wheel edges that are struck by moving wind or water which forces the wheel to turn. It was through the turning of this large central wheel, which could turn other smaller wheels, that mechanical energy was obtained and work, like grinding corn or operating a pump, could be accomplished.

The most ancient of these methods was the undershot wheel or paddle wheel. On these old waterwheels, only the very lowest part of the wheel was submerged beneath a moving body of water, and the entire wheel was turned as the river flowed past it, pushing against its paddles. This was a prototype for what came to be called an impulse turbine, which is one that is driven by the force of a fluid directly striking it. The undershot waterwheel was followed during medieval times by the overshot wheel. This first made its appearance in Germany around the middle of the twelveth century and became the prototype for the modern reaction turbine. Contrasted to the impulse turbine whose energy source is kinetic energy (something striking something else and giving it some of its energy), the energy source for an overshot wheel (or reaction turbine) is known as potential energy. This is because it is the weight of the water acting under gravity that is used to turn the wheel. Renaissance engineers studied the waterwheel and realized that the action of water on a wheel with blades would be much more effective if the entire wheel were somehow enclosed in a kind of chamber. They knew very well that only a small amount of the water pushing or falling on a wheel blade or paddle actually strikes it, and that much of the energy contained in the onrushing water is lost or never actually captured. Enclosing the wheel and channeling the water through this chamber would result in a machine of greater efficiency and power. They were hampered, however, by a lack of any theoretical understanding of hydraulics as well as by a lack of precision machine tools with which they could carefully build things. Both of these problems were resolved to some degree in the eighteenth century, and one of the earliest examples of a reaction turbine was built in 1750 by the German mathematician and naturalist Johann Andres von Segner (1704-1777). In his system, the moving water entered a cylindrical box containing the shaft of a runner or rotor and flowed out through tangential openings, acting with its weight on the inclined vanes of the wheel.

A really efficient water turbine was now within reach it appeared, and a prize was offered in France by the Societe d'Encouragement pour l'Industrie Nationale. The prize was won by the French mining engineer Claude Burdin (1778-1873), who published his results in 1828. It was in this publication that Burdin coined the word "turbine" which he took from the Latin "turbo" meaning a whirling or spinning top. It was Burdin's student, Benoit Fourneyron (1801-1867), who improved and developed his master's work and who is considered to be the inventor of the modern hydraulic turbine. Four-neyron built a six-horsepower turbine and later went on to build larger machines that worked under higher pressures and delivered more horsepower. His main contribution was his addition of a distributor which guided the water flow so that it acted with the greatest efficiency on the blades of the wheel. His was a reaction type turbine, since water entering through the vanes of the distributor (that was fitted inside the blades) then acted on the blades of the wheel. Following Fourneyron's first turbine, which happened to be a hydraulic or water turbine, other turbines were developed that used the energy of a different material like gas or steam. Although these different types of turbines have different means of operation and certainly different histories, they still embody the basic characteristics of a turbine. They all spin, or receive their energy from some form of a moving fluid, and they all convert it into mechanical energy.