| slovo | definícia |
de Laval turbine
(gcide) | Turbine \Tur"bine\ (t[^u]r"b[i^]n), n. [L. turbo, -inis, that
which spins or whirls round, whirl.]
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.
[1913 Webster]
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.
[1913 Webster]
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."
[Webster 1913 Suppl. +PJC] |
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