1.A water wheel, commonly horizontal, variously constructed, but usually having a series of curved floats or buckets, against which the water acts by its impulse or reaction in flowing either outward from a central chamber, inward from an external casing, or from above downward, etc.; also called turbine wheel. Note: In some turbines, the water is supplied to the wheel from below, instead of above. Turbines in which the water flows in a direction parallel to the axis are called parallel-flow turbines.
2.A type of rotary engine with a set of rotating vanes, diagonally inclined and often curved, attached to a central spindle, and obtaining its motive force from the passage of a fluid, as water, steam, combusted gases, or air, over the vanes. Water turbines are frequently used for generating power at hydroelectric power stations, and steam turbines are used for generating power from coal- or oil-fired electric power stations. Turbines are also found in jet engines, and in some automobile engines. Note: In the 1913 dictionary, the turbine was further decribed thus: "There are practically only two distinct kinds, and they are typified in the de Laval and the Parsons and Curtis turbines. The de Laval turbine is an impulse turbine, in which steam impinges upon revolving blades from a flared nozzle. The flare of the nozzle causes expansion of the steam, and hence changes its pressure energy into kinetic energy. An enormous velocity (30,000 revolutions per minute in the 5 H. P. size) is requisite for high efficiency, and the machine has therefore to be geared down to be of practical use. Some recent development of this type include turbines formed of several de Laval elements compounded as in the ordinary expansion engine. The Parsons turbine is an impulse-and-reaction turbine, usually of the axial type. The steam is constrained to pass successively through alternate rows of fixed and moving blades, being expanded down to a condenser pressure of about 1 lb. per square inch absolute. The Curtis turbine is somewhat simpler than the Parsons, and consists of elements each of which has at least two rows of moving blades and one row of stationary. The bucket velocity is lowered by fractional velocity reduction. Both the Parsons and Curtis turbines are suitable for driving dynamos and steamships directly. In efficiency, lightness, and bulk for a given power, they compare favorably with reciprocating engines."
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