A recent form of the Jonval turbine is shown in fig.
99, p. 167), using Froude's turbine to obtain the highly resisting spiral vortices, and arranging passages in the casing for the entry of water at the hub of the wheel and its exit at the circumference.
2 The following statistics of turbine construction in Switzerland are taken from Schweizerische Bauzeitung (1901), p. 128, which, in the same volume at p. 53, contains a valuable article on the most important improvements in turbines and their regulation shown in the Paris Exhibition of 1901: - of one of these, which gave an efficiency of 87% at full load and 70% at about three-fifths full load.
Another turbine which has come into extensive use is the " Francis," an exceedingly efficient turbine on a low fall with large quantities" of water.
This turbine was designed to give 1250 H.P. with a fall of 25 ft.
Tests of a turbine of this slow-moving type showed an efficiency of 82% at full gate, and one of 75% when half of the passages in the guide-blades were closed by the shutters, as described above.
In the " Hercules " turbine, shown in fig.
At 150 revolutions, each turbine will have a nominal horsepower of woo.
P. 467, " Some Large Turbine Installations."
In turbine engines this method is inapplicable.
In July 1888 the Societe Metallurgique Suisse erected plant driven by a 500 h.p. turbine to carry out Heroult's alloy process, and at the end of that year the Allgemeine Elektricitais Gesellschaft united with the Swiss firm in organizing the Aluminium Industrie Actien Gesellschaft of Neuhasen, which has factories in Switzerland, Germany and Austria.
Another turbine of the mixed flow type is the " Victor," which consists of three parts - the outer guide case, and, inside this, the register gate, and the wheel.
The turbine FIG.
Efficiency of the Francis turbine being in this case 86% at full load and 77% at half load.
This difficulty may be overcome by using Rateau's arrangement of a low-pressure turbine between the engine and the condenser.