Page 133 - NAVAL SCIENCE 3 TEXTBOOK

138 NAVAL SKILLS

is called the collision lmlkhend. If one ship rams <mother head Oil, After being raised to high pressure and temperature in a super-
the bow structure would collapse, hopefully, somewhere fonvard heater in another part of the boiler, the steam flows through pipes
of the collision bulkhead, thus preventing flooding of compart- to turbines, called the "main engines." fresh water used to produce
ments aft of it. the steam in the boilers is distilled from salt water by evaporators.
ivlaintenance of watertight integrity is a function of damage A steam turbine consists of a central rotating shaft, to which are
cO/it mi. The purpose of damage control is to keep an}' damage from attached se\'eral rows of movable blades similar to those of a fan,
spreading elsewhere in the ship. All doors and hatches through with stationary blades between. The shaft and blading arc enclosed
watertight bulkheads or decks must be watertight. \Vherever steam, within a thick, airtight casing. As the steam passes through the tur-
oil, or air piping, electric cables, or ventilation ducts penetrate a bine, it is directed through the stationary blades onto the rotating
watertight bulkhead or deck, they go through a watertight sllIffillg ones, causing the shaft to spin rapidly.
tlIbe (a cylinder plugged with watertight filler material) or other Because turbines operate most elTicientl), ilt speeds of several
device to prevent leakage. All watertight doors and hatches carry thousand revolutions per minute (rpm) but propellers are not very
markings that indicate ,,,hen they ma}' or may not be opened. effective above a few hundred rpm, redllction genrs like a transmis-
sion in an automobile mllst be used to make the transition from
the high speed of the turbine to the necessarily slower speed of the
Propulsion Plants propeller shafts.
Today's naval ships are propelled mainly by conventional steam In recent years the gns lllrbille CIIgille has been adapted for ship
plants, gas turbine engines, or nuclear power plants, although the propulsion. Developed frOlil aircraft engines, this engine pow-
usc of diesel engines is steadily increasing. A conventional steam ers several classes of destroyers and frigates, Aegis cruisers, mine-
propulsion plant consists of boilers, main engines (steam tur- sweepers, Coast Guard cLitlers, and landing craft. The Navy's new
bines), reduction gears, propeller shafts, and propellers. Nuclear- littoral combat ships (LeSs) are powered by a combination of two
powered ships have steam propulsion also, but the steam is pro- gas turbine engines and two diesels.
duced by heat from a nuclear reactor instead of oil-fired boilers. Gas turbines ilrc made up of three basic parts; a compressor,
A boiler consists of a boxlike casing containing hundreds of a combustion chamber, and a turbine. Thc compressor draws in
water-filled steel tubes near the top, which arc arranged so that air, compresses it, and sends it under pressure to the combustion
heat from furnace-like fireboxes bene.:lth passes over them, turn- chamber, where it is combined with atomized (small droplets) fuel
ing the water into steam. Fuel oil, sprayed into the fireboxes under and burned. The combustion gases expand and flow through the
high pressure, ignites and burns intensely, producing the heat. turbine blades, causing the turbine to rotate and drive the shaft
and propeller.

hUI!!:'-
fun C~YUIUI ID I H~o.>IAI. ~NnGV
IN ~o;l [~ FII",,-,"=(
------ ~
D:R£C'~OF
REACtl~£ fO~£ - - - --,
r~\lSn ,
,
IAI« :
~~.c ___ _ ____ ,

1>I("""'l £NE lIGf Of
oW'"''''lIH''' I>iElOU.I. UlIOlIGTOF
CDHYUITEO 10 ~~lJl wrr (1)\,1,1)$1 11( ....
~[(H.I.);tQ.l f""'IIGT USlOHUI[ TO >I(A I AKI
Of.[ou.Tf fH OW~T U
Processes and components of the basic steam cycle of a conventional (oil-fired) steam-driven ship.