\Tur"bine\, n.
A form of steam engine analogous in construction and action
to the water turbine. 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.

\Tur"bine\, n. [L. turbo, -inis, that which spins or
whirls round, whirl.]
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.