¡Descarga Marine Engines: Types, Components, and Applications y más Traducciones en PDF de Inglés Técnico solo en Docsity!
Unit III. Identifying marine main engines.
Speaking.
Look at the pictures.
What type of marine engines do you think they are?
Look at the figure shown below. Write TRUE or FALSE
1. A ship propulsion system includes at least one marine propeller
2. A ship propulsion system has three main components
3. The components are main engine, auxiliary machinery and the propeller
Label the three components of a ship propulsion system.
A. Propeller
B. Main engine
C. Shaft
Universidad Nacional Experimental Marítima del Caribe
Vicerrectorado Académico
Cátedra de Idiomas
English VI. Maritime Engineering
Marine facilities
Remember!
Reading. Read the following text
Marine main engines
There are four main types of marine engine: the diesel engine, the steam turbine, the gas turbine and the marine nuclear plant. Each type of engine has its own particular application.
The diesel engine is started by means of compressed air admitted into the cylinder at high pressure via a special starting valve. There are two main types of diesel engines: one is the two-cycle and the other is the four-cycle. The power output of a modern marine diesel engine is about 40,000 brake horse power (bhp). This is now expressed in kilowatts. Large diesel engines, which have cylinders near 3 ft in diameter, turn at the relatively small speed of about 108 r.p.m. These are known as slow-speed diesel engines. They can be connected directly to the propeller without gearing. Although higher power could be produced by higher revolutions, this would reduce the efficiency of the propeller, because a propeller is more efficient the larger it is and the slower it turns. These large slow-running engines are used in the larger merchant ships, particularly in tankers and bulk carriers. The main reason is their low-fuel consumption.
Ships are large, complex vehicles which must be self-sustaining in their environment for long periods with a high degree of reliability. A ship is the product of two main areas of skill, those of the naval architect and the marine engineer. The naval architect is concerned with the hull, its structure, form, habitability, and ability to endure its environment. The marine engineer is responsible for the various systems which propel and operate the ship. More specifically, this means the machinery required for propulsion, steering, anchoring and ship securing, cargo handling, air conditioning, power generation and its distribution.
What marine systems have you already learnt about? What do you know about marine main engines?
A diesel engine is a ship's reciprocating machine, the internal combustion engine. To understand how a diesel engine works imagine the piston just near the top of its upstroke. All access from the outer air is closed but a given volume of air has been drawn in and trapped in between the bottom of the cylinder top and the top of the piston. Air is compressed and it heats. At the point of maximum compression a needle valve in the cylinder head opens, a spray of fuel enters. An explosion takes place and the piston is driven down the cylinder. Working via the piston rod, crosshead and connecting rod , it rotates the crankshaft. No diesel engine is a single cylinder engine, there may be as many as twelve driving one crankshaft, but each cylinder is self-sufficient in operation.
A nuclear-powered ship differs from a conventional turbine ship in that it uses the
energy released by the decay of radioactive fuel to generate steam. The steam is used to
turn a shaft via a turbine in the conventional way.
Complete this diagram to form a summary of the basic types of marine engine.
What’s the difference between steam turbines and gas turbines?
Gas turbines differ from steam turbines in that gas rather than steam is used to turn a shaft. These have also become more suitable for use in ships. Many naval vessels are powered by gas turbines and several container ships are fitted with them. A gas turbine engine is very light and easily removed for maintenance. It is also suitable for complete automation. The gas turbine efficiency being low, its main advantage is its small weight and size which makes a gas turbine installation very attractive for naval applications. Most of modern warships of about 5,000 ton displacement are powered with gas turbines usually combined with diesel engines. Gas turbines are easier to start and reliable in operation. However, the use of astern gas turbines is a rather complex problem; therefore ships powered with main gas turbine units are equipped with either controllable pitch propellers (c.p.p.) or other reversing gears.
Nuclear power in ships has mainly been confined to naval vessels, particularly to submarines. But this form of power can be used more in merchant ships as oil fuels become more expensive. The atomic ice-breakers opened new
possibilities in exploring the
northern areas. They can sail for a
long time without refueling.
Fill in this box to summarize the applications of these engines.
Words and terms to be remembered
power-plant habitability nuclear reciprocate combustion piston stroke cylinder valve explosion piston rod crosshead connecting rod crankshaft cycle
output
gear
efficiency
fuel
power
steam
turbine
blade
vane
shaft
rotate
astern
pitch
reverse
release
Type of engine Application
Slow-speed diesel
Medium-speed diesel
Steam turbine
Gas turbine
Marine nuclear plant
Match the following words (terms) with their explanations.
1) force used for driving machines ___ a) pitch
2) any powerful self-working machine ___ b) bed plate
3) any substance (e.g. oil), by which a fire is kept going ___ c) turbine
4) a foundation framework for a marine engine___ d) power
5) the distance the propeller will advance during one revolution ___ e) fuel
6) a screw with a set of blades ___ f) nuclear reactor
7) a shaft turned by cranks which changes reciprocation motion into
circular motion ___
g) crankshaft
8) vapour from boiling water ___ h) propeller
9) apparatus for producing atomic energy___ i) piston
10) machine or device for forcing liquid into or out of or through
something ___
j) pump
11) engine or motor whose driving wheel is turned by a flow of water,
steam or gas ___
k) shaft
12) the rod which turns the propeller ___ l) steam
13) a connection by means of toothed wheels ___ m) valve
14) a mechanical device for controlling the flow of air, gas, liquid in
one direction ___
n) gear
15) a cylinder fitting closely inside another cylinder used in engines,
pumps to pass on motion ___
o) engine
"...If the wheelhouse is the brain of the ship, the engine room may be called the heart of the ship".
W. Somerset Maugham "Mister Know-All"
