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.

Read the text again. Look at the picture and with the help of your facilitator; label the parts of this

engine.

Learn more about main engines.

More and more of the larger merchant vessels are being powered by

medium-speed diesel engines. These operate between 150 and 450 r.p.m.,

therefore they are connected to the propeller by gearing. This type of engine

was once restricted to smaller cargo ships, but now they are used in fast

cargo liners as well as in tankers and bulk carriers.

The marine engineer concerns about

the engine and is responsible for the

various systems which propel and

operate the ship.

The steam turbine has until recently been the first

choice for very large power main propulsion units. Its

advantages of little or no vibration, low weight, minimum

space requirements and low maintenance costs are

considerable. In steam turbines high pressure steam is

directed into a series of blades or vanes attached to a shaft,

causing it to rotate. This rotary motion is transferred to the

propeller shaft by gears. Steam is produced by boiling

water in a boiler, which is fired by oil. Recent

developments in steam turbines which have reduced fuel

consumption and raised power output have made them

more attractive as an alternative to diesel power in ships.

They are 50 per cent lighter and on very large tankers

some of the steam can be used to drive the large cargo oil

pumps. Turbines are often used in container ships, which

travel at high speeds.

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

Arrange the words below into the pairs of synonyms:

Read the text and answer the following questions.

1. What main types of marine engine can be found at sea today?

2. Why must the propeller shaft rotate at a relatively slow speed?

3. What is the difference between steam and gas turbine?

4. Is the nuclear power used in merchant ships?

Grammar.

restrict self-sustained

output plant navy

conventional combustion (to) power

remove maintenance

power reverse explore

produce drive

energy traditional opposite service

installation limit

warships investigate

burning independent

take-off

Expressing differences

Steam turbines are different from gas turbines

Steam turbines differ from gas turbine in that

gas rather than steam is used to turn a shaft

While/Whereas diesel engines are cheap,

nuclear plants are not.

Diesel engines are cheap. On the contrary,

nuclear plants are expensive.

Expressing similarities

Both steam turbines and gas turbines are light.

A steam turbine is as light as the gas turbine.

The parts of a steam turbine are similar to the

gas turbine

Neither ferries nor carriers are nuclear-powered

ships

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"