Unit 6
Combinations of Machinery
Passive Voice
8.1. Combinations of Machinery
Advantage can sometimes be gained by forming a propulsion plant from disparate
elements. A memorable example was the Titanic, which was built in the early days of
steam turbine propulsion. The Titanic was propelled by a pair of reciprocating steam
engines that exhausted their steam into a single steam turbine. This technique was known
as turbo-compounding. Turbo-compounding, in the guise of turbo-charging, is common
in diesel technology. Absent an excessively long stroke, a diesel cylinder cannot fully
expand its working fluid. One remedy is to exhaust the cylinder gas into a turbine that
drives a compressor that in turn supplies the cylinder charge at high pressure. The major
benefit of turbo-charging is an increase in the power output of the engine without an
increase in its size, save for the small increase that the turbocharger represents. In some
instances the cylinder exhaust gas contains more energy than the turbocharger requires,
and the surplus may be applied to a second turbine whose output is added to that of the
engine's crankshaft. Such an arrangement is most likely to be found with low-speed
engines in ships built since 1980.Gas turbines also have been combined with diesel
engines as independent units, i.e., supplied with their own fuel and working fluid rather
than with diesel exhaust gas. This provides the opportunity to combine the high efficiency
of a diesel for cruising speeds with the high output of the comparatively light gas turbine
when bursts of speed are needed. Such needs rarely exist among commercial vessels, but
combined diesel and gas is appropriate for some military vessels.
8.1.1. The Gas Turbine Engine
A turbine is a rotary machine that converts the kinetic energy in a stream of fluid (gas
or liquid) into mechanical energy. The stream of fluid is guided to a rotor, a wheel that is
mounted to a shaft from which power is taken. The fluid strikes a series of buckets, fins,
or blades on the rotor, and the energy in the fluid makes the rotor spin. Turbines are an
example of Newton's third law of motion, which states that for every action there is an
equal and opposite reaction. The earliest known turbine was built (AD c.75) by the Greek
inventor Hero of Alexandria. His device was a hollow ball that spun in reaction to jets of
steam escaping from it. Although only a toy, it demonstrated the principle used in today's
jet engine.
The gas turbine engine, essentially a jet engine coupled to a turbine that is geared to a
propeller shaft, appeared to have found a niche in commercial ship propulsion about
1970. However, the fuel price increase of the 1970s, which gave diesel its dominance
over steam, gave it dominance over gas as well, and the niche for the latter suddenly
disappeared. On the other hand, the gas turbine remains the principal propulsion engine
among naval combat vessels because of the high power that can be produced from very
low weights and volumes of machinery. Steam propulsion survives in certain naval
vessels, particularly submarines, where the heat source is a nuclear reactor. Extreme
cruising range and independence from an air supply are advantages of using nuclear
energy as the heat source in naval propulsion, but these advantages are of little merit in
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commercial shipping. A few prototype cargo ships with nuclear propulsion were built in
the 1960s, but they did not lead to commercial application.
8.2. Passive Voice
8.2.1. Notes on the form of the passive
1. Formation: regular and irregular past participles
We form the passive with a form of be and a past participle. The past participle does
not necessarily refer to past time. Rules applying to the use of tenses in the active apply in
the passive. For example, an action in progress now requires the present progressive in:
Your steak is being grilled and will be ready in a minute.
2. Transitive and intransitive verbs
The passive occurs only with verbs used intransitively, that is, verbs that can be
followed by an object:
active: Someone found his wallet on the forecastle.
passive: This wallet was found on the forecastle.
Many verbs can be used transitively or intransitively:
The door opened. (perhaps by itself )
The door was opened. (perhaps by someone)
3. Direct or indirect objects
Verbs like bring and give which can have two objects, e.g. Tom gave me (indirect) a
pen (direct), can have two passive forms:
I was given a pen by Tom. (indirect object becomes subject)
A pen was given (to) me by Tom. (direct object becomes subject)
Because we are often more interested in people (or animals) than things, personal
subjects tend to be more common than impersonal ones. Thus, ‘I was given this pen’ is
more likely to occur than ‘This pen was given to me’. In sentences like the second
example, to (or for) can be omitted before a personal pronoun (This pen was given me)
but not usually otherwise: ‘This pen was given to my father’.
4. Stative verbs. Many stative verbs cannot be used in the passive, even when they are
transitive: I love beans on toast. (active voice only). Verbs like measure, which can be
stative or dynamic, can only be passive in their dynamic sense:
stative: This desk measures 125 × 60 cm.
dynamic: This desk has been measured.
5. Progressive forms. Only present and past progressive forms are common:
He is being interviewed now.
He was being interviewed at 10.
However modals with progressive passive sometimes occur:
Combination of Machinery; Passive Voice 69
I know Mark was going to have an interview some time this afternoon. He may
be being interviewed at this very moment.
6. Phrasal verbs. Transitive constructions with the pattern verb + adverb particle (A gust
of wind blew the flag down) can be used in the passive:
The flag was blown down. (by a gust of wind).
7. Verb + preposition:
The newsagent’s has been broken into.
Only a few verbs of the type verb + particle + preposition (We have done away with the
old rules) can be used in the passive:
The old rules have been done away with.
8. The –ing form and the to-infinitive. Passive constructions are common after verbs
followed by the –ing form, such as enjoy, like and remember:
Most people don’t like being criticized.
And after verbs followed by a to-infinitive:
He hates to be criticized.
We can use the passive (-ing form only) after conjunctions such as on and after:
On/After being informed that her mother was seriously ill, she hurried back to
England. (i.e. When she was informed…)
9. Verbs generally used in the passive. A small number of verbs are used more
frequently in the passive than in the active: e.g. be born, be married, be obliged:
I’m not obliged to work overtime if I don’t want to.
10. Adverbs of manner in the passive sentences. Adverbs of manner can occur before
or after the participle:
This room has been badly painted/painted badly.
11. We often use abbreviated passive constructions when expressing:
• wishes: I’d like it (to be) fried/cleaned/repaired. etc.
• preferences: I like it (when it is) fried/ boiled. etc.
8.2.2. Uses of the passive
a. Spontaneous and deliberate use of the passive
In fluent English, passives occur naturally and spontaneously, without a conscious change
from ‘active’ to ‘passive’. In fact, active equivalents would be hard to produce for
sentences like:
The origins of the universe will probably never be explained.
The ship was not built in a day.
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The passive is sometimes deliberately chosen in preference to the active, especially
when speakers do not wish to commit themselves to actions, opinions, or statements of
fact of which they are not completely certain:
This matter will be dealt with as soon as possible.
Thousands of books are published every year and very few of them are noticed.
b. The passive for focus
We use the passive when we wish to focus on a happening which is more important to
us than who or what causes the happening – or when there is simply no need to mention
the doer. If we say:
The hold was damaged in last night’s storm.
We are mainly concerned with the hold and what happened to it.
c. The use of ‘by’ + agent after passive
An agent is a ‘doer’, i.e. the person or thing that performs the action indicated by the
verb.
By + agent in passive constructions tells us who or what did something:
The window was broken by the boy who lives opposite.
The window was broken by a stone.
By + agent is only necessary when the speaker wishes to say who or what is responsible
for the event in question. The position of by + agent at the end of a clause or sentence
gives it particular emphasis:
The window was broken by a slate that fell off the roof.
By + agent is often used with the passive of verbs like build, compose, damage, design,
destroy, discover, invent, make, wreck and write. Note how a subject-question in the
active is often answered by a passive, so that the important information is emphasized by
being at the end:
Who composed that piece? It was composed by Mozart.
What destroyed that village? It was destroyed by a bomb.
8.2.3. Some typical contexts for the passive
1. Formal notices and announcements:
Candidates are required to present themselves fifteen minutes before the
examination begins. They are asked to be punctual.
2. Press reports:
Often the agent is not known or does not need to be mentioned:
The search for the bank robbers continues. Meanwhile, many people have been
questioned and the owner of the stolen getaway car has been traced.
3. Headlines, advertisements, notices, etc:
TRADE AGREEMENTS BROKEN!
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PRICES SLASHED!
ALL GOODS GREATLY REDUCED!
PETROL COUPONS ACCEPTED!
4. Scientific writing (to describe ‘process’):
The mixture is placed in a recipient and is heated to a temperature of 300˚ C. It is
then allowed to cool before it can be analysed.
8.3. Vocabulary
propulsion plant = instalaţie de propulsie
steam turbine propulsion = propulsie cu turbină cu abur
single steam turbine = turbină simplă cu abur
turbo-compounding = turbo-mecanism
compressor = compresor
engine's crankshaft = arborele motorului
cruising speed = viteză de croazieră
burst of speed = creştere bruscă a vitezei
jet engine = motor cu reacţie, reactor
geared = angrenat, cuplat
propeller shaft = axul elicei
naval combat vessel = navă militară de luptă
nuclear reactor = reactor nuclear
extreme cruising range = rază maximă de croazieră
