Fig. 3 shows a phantom view of a modern hydraulic turbine, giving the names and relative locations of different parts. The accompanying table contains a classification of water wheels. Furtherdescriptions of water wheels herein will be limited to the hydraulic turbine, which is practically the only type of hydraulic motor now in extensive use, excepting a limited number of impulse water wheels of the Felton type.
The word turbine, meaning pnmarlly a •wheel that revolves' does not of itself dis tinguish the class of water motors to which it is commonly applied. The word turbine appears to have been first applied to a water wheel by Burdin in 1825. Fourneyron, a pupil of Burdin, perfected the outward-flow wheel, and his use of the term turbine as describing such wheels led to its general adoption to distinguish water wheels operating by combined action and receiv ing their water supply to all the buckets simul taneously. We find the word turbine variously defined by different authors. Weishach includes impulse wheels in the class of turbines. Bjorling distinguishes a turbine from a water wheel in that it takes its water supply at the centre or bot tom of the fall. while a water wheel takes water from the top of the fall. Bodner says a turbine may be defined as a water wheel in which a mo tion of the water relative to the buckets is essen tial. \Ve also find a turbine defined as a water wheel having buckets which the water flows through instead of in and out at the same open ing, as in the, case of an overshot or impulse wheel. Again a turbine is defined as a water wheel in which the buckets are entirely filled instead of being partially filled as in the case of a water wheel or impulse wheel. The hydraulic turbine in all its vari ous forms is practically a development of the 19th century, and the modern high speed large capacity hydraulic turbine has • evolved from a somewhat crude prototype, mainly within the last 40 years. In the early part of the 19th century, parallel flow or Jonval turbines, and outward flow, or Fourneyron tur bines, both French inventions, were largely used. In the former the water flowed through the turbine runner in a direction generally parallel with the axis. In the latter the water flowed outward more or less radially through the runner. These simple types of hydraulic turbines were capable of application only 'to relatively small capacities and low speeds. Then came the development in America of the inward flow type of turbine. This was the work of na one inventor, although Samuel B. Howd of Geneva, N. Y., patented such a turbine in 1836, which closely resembles the most modern types in,t8Lprinciple of operation. While more comeact and giving a higher speed than the French turbine, 'it was still a wheel of sawn capatity. B. Francis of Lowell improved
the inechatedeal construction and efficiency of the Howd wheel, and further developments were made by Swain and others. Even before the advent of hydro-electric power developments and transmission, there came a demand for water wheels of higher speed and greater capac fty be supplied. Probably the greatest achievement qf any one man in advanc mg the development of the hydraulic turbine was that of John B. McCormick of Indiana County, Pa. About 1870 he found that by extending the bucket vanes of an inward flow turbine down ward and outward, making them ladle or spoon shaped, he was able to greatly increase the outlet openings of a turbine of a given diameter. At the same time the length or the depth of the inlet openings was proportionately increased, thus greatly increasing the capacity without in creasing the diameter of the runner. Since the speed of a turbine decreases as the diameter in creases, he thus produced a turbine of much greater capacity than any heretofore available without reducing the speed. It was also found that the use of curved vanes, providing for downward and outward flow, as well as inward flow, through the runner, increased the efficiency, since the water left the wheel in a direction op posite to that of the motion of the runner, and so dropped away from the runner • with very little absolute velocity.
McCormick's designs were, however, arbi trary, and each size or pattern was worked out by long and costly experimentation. While the theory of the hydraulic turbine had been de veloped mathematically many years before, it had never been successfully applied in practice to the design of turbines to meet specific con ditions until after the advent of hydro-electric power transmission. The next step in advance consisted in the modification of the combined flow or McCormick turbine, largely by means of theoretical deductions so as to adapt it to speeds, capacities and other conditions somewhat different from those for which the experinental designs were made. This process started in Europe, especially in Switzerland, where it was first applied to outward flow or Fourneyron tur bines, exemplified by the Swiss turbines installed in the Niagara power development of 1895. Scientific methods of design were soon extended to inward and combined flow turbines, chiefly in the United States until at the present time, combined inflow, or so-called Francis type tur bines are produced, not only of enormous capacity, high efficiency and speed, but of de sign so nicely adjusted as to give in practice almost precisely the required or pre-determined speed, power and efficiency to meet any desired condition, yet the form of runner and principle of its operation are almost precisely as McCor mick left it.