An
engine or
motor is a
machine designed to convert energy into useful
mechanical motion.
[1][2] Heat engines, including
internal combustion engines and
external combustion engines (such as
steam engines) burn a
fuel to create
heat which is then used to create motion.
Electric motors convert electrical energy into
mechanical motion,
pneumatic motors use
compressed air and others, such as
clockwork motors in
wind-up toys use
elastic energy. In biological systems,
molecular motors like
myosins in
muscles use
chemical energy to create motion.
Terminology
Originally an engine was a mechanical device that converted force into motion. Military devices such as
catapults,
trebuchets and
battering rams are referred to as
siege engines. The term "gin" as in
cotton gin is recognised as a short form of the
Old French word
engin, in turn from the
Latin ingenium, related to
ingenious. Most devices used in the
industrial revolution were referred to as engines, and this is where the
steam engine gained its name.
[citation needed]
In modern usage, the term is used to describe devices capable of performing
mechanical work, as in the original steam engine. In most cases the work is produced by exerting a
torque or linear force, which is used to operate other machinery which can generate
electricity,
pump water, or
compress gas. In the context of propulsion systems, an air-breathing engine is one that uses atmospheric air to oxidise the
fuel carried rather than supplying an independent oxidizer, as in a
rocket.
In common usage, an
engine burns or otherwise consumes
fuel, and is differentiated from an electric machine (i.e.,
electric motor) that derives power without changing the composition of matter.
[3] A heat engine may also serve as a
prime mover, a component that transforms the flow or changes in pressure of a
fluid into
mechanical energy.
[4] An
automobile powered by an
internal combustion engine may make use of various motors and pumps, but ultimately all such devices derive their power from the engine.
The term
motor was originally used to distinguish the new
internal combustion engine-powered vehicles from earlier vehicles powered by
steam engines, such as the
steam roller and
motor roller, but may be used to refer to any engine.
[citation needed]
Devices converting heat energy into motion are commonly referred to simply as
engines.
[5]
History
Antiquity
Simple machines, such as the
club and
oar (examples of the
lever), are
prehistoric. More complex engines using
human power,
animal power,
water power,
wind power and even
steam power date back to antiquity. Human power was focused by the use of simple engines, such as the
capstan,
windlass or
treadmill, and with
ropes,
pulleys, and
block and tackle arrangements; this power was transmitted usually with the forces
multiplied and the speed
reduced. These were used in
cranes and aboard
ships in
Ancient Greece, as well as in
mines,
water pumps and
siege engines in
Ancient Rome. The writers of those times, including
Vitruvius,
Frontinus and
Pliny the Elder, treat these engines as commonplace, so their invention may be more ancient. By the 1st century AD,
cattle and
horses were used in
mills, driving machines similar to those powered by humans in earlier times.
According to
Strabo, a water powered mill was built in Kaberia of the
kingdom of Mithridates during the 1st century BC. Use of
water wheels in mills spread throughout the
Roman Empire over the next few centuries. Some were quite complex, with
aqueducts,
dams, and
sluices to maintain and channel the water, along with systems of
gears, or toothed-wheels made of wood and metal to regulate the speed of rotation. In a poem by
Ausonius in the 4th century AD, he mentions a stone-cutting saw powered by water.
Hero of Alexandria is credited with many such
wind and
steam powered machines in the 1st century AD, including the
Aeolipile, but it is not known if any of these were put to practical use.
Medieval
Medieval Muslim engineers employed
gears in mills and water-raising
machines, and used
dams as a source of water power to provide additional power to watermills and water-raising machines.
[6] Such advances made it possible for many industrial tasks that were previously driven by
manual labour to be
mechanized and driven by
machinery to some extent in the
medieval Islamic world.
In 1206,
al-Jazari employed a
crank-
conrod system for two of his water-raising machines. A rudimentary
steam turbine device was described by
Taqi al-Din[6] in 1551 and by
Giovanni Branca[7] in 1629.
[8]
In the 13th century, the solid
rocket motor was invented in China. Driven by gunpowder, this, the simplest form of
internal combustion engine was unable to deliver sustained power, but was useful for propelling weaponry at high speeds towards enemies in battle and for
fireworks. After invention, this innovation spread throughout Europe.
Industrial Revolution
Boulton & Watt engine of 1788
The Watt steam engine was the first type of
steam engine to make use of steam at a pressure just above
atmospheric to drive the piston helped by a partial vacuum. Improving on the design of the 1712
Newcomen steam engine,
the Watt steam engine, developed sporadically from 1763 to 1775, was a
great step in the development of the steam engine. Offering a dramatic
increase in
fuel efficiency,
James Watt's design became synonymous with steam engines, due in no small part to his business partner,
Matthew Boulton.
It enabled rapid development of efficient semi-automated factories on a
previously unimaginable scale in places where waterpower was not
available. Later development led to
steam locomotives and great expansion of
railway transportation.
As for
internal combustion piston engines, these were tested in
France in 1807 by
de Rivaz and independently, by the
Niépce brothers . They were theoretically advanced by
Carnot in 1824.
[citation needed] The
Otto cycle in 1877 was capable of giving a far higher
power to weight ratio than steam engines and worked much better for many transportation applications such as cars and aircraft.
Automobiles
The first commercially successful automobile, created by
Karl Benz,
added to the interest in light and powerful engines. The lightweight
petrol internal combustion engine, operating on a four-stroke Otto
cycle, has been the most successful for light automobiles, while the
more efficient
Diesel engine is used for trucks and buses.
Horizontally opposed pistons
In 1896, Karl Benz was granted a patent for his design of the first
engine with horizontally opposed pistons. His design created an engine
in which the corresponding pistons move in horizontal cylinders and
reach top dead center simultaneously, thus automatically balancing each
other with respect to their individual momentum. Engines of this design
are often referred to as flat engines because of their shape and lower
profile. They are or were used in: the
Volkswagen Beetle, some Porsche and Subaru cars, many
BMW and
Honda motorcycles, and
aircraft engines (for propeller driven aircraft), etc.
Advancement
Continuance of the use of the internal combustion engine for
automobiles is partly due to the improvement of engine control systems
(onboard computers providing engine management processes, and
electronically controlled fuel injection). Forced air induction by
turbocharging and supercharging have increased power outputs and engine
efficiencies. Similar changes have been applied to smaller diesel
engines giving them almost the same power characteristics as petrol
engines. This is especially evident with the popularity of smaller
diesel engine propelled cars in Europe. Larger diesel engines are still
often used in trucks and heavy machinery, although they require special
machining not available in most factories. They do not burn as clean as
gasoline engines, however they have far more
torque.
The internal combustion engine was originally selected for the
automobile due to its flexibility over a wide range of speeds. Also, the
power developed for a given weight engine was reasonable; it could be
produced by economical mass-production methods; and it used a readily
available, moderately priced fuel - petrol.
Increasing power
The first half of the 20th century saw a trend to increasing engine
power, particularly in the American models. Design changes incorporated
all known methods of raising engine capacity, including increasing the
pressure in the cylinders to improve efficiency, increasing the size of
the engine, and increasing the speed at which power is generated. The
higher forces and pressures created by these changes created engine
vibration and size problems that led to stiffer, more compact engines
with V and opposed cylinder layouts replacing longer straight-line
arrangements.
Combustion efficiency
The design principles favoured in Europe, because of economic and
other restraints such as smaller and twistier roads, leant toward
smaller cars and corresponding to the design principles that
concentrated on increasing the combustion efficiency of smaller engines.
This produced more economical engines with earlier four-cylinder
designs rated at 40 horsepower (30 kW) and six-cylinder designs rated as
low as 80 horsepower (60 kW), compared with the large volume V-8
American engines with power ratings in the range from 250 to 350 hp (190
to 260 kW).
[citation needed]
Engine configuration
Earlier automobile engine development produced a much larger range of
engines than is in common use today. Engines have ranged from 1- to
16-cylinder designs with corresponding differences in overall size,
weight, piston displacement, and cylinder bores. Four cylinders and
power ratings from 19 to 120 hp (14 to 90 kW) were followed in a
majority of the models. Several three-cylinder, two-stroke-cycle models
were built while most engines had straight or in-line cylinders. There
were several V-type models and horizontally opposed two- and
four-cylinder makes too. Overhead camshafts were frequently employed.
The smaller engines were commonly air-cooled and located at the rear of
the vehicle; compression ratios were relatively low. The 1970s and '80s
saw an increased interest in improved fuel economy which brought in a
return to smaller V-6 and four-cylinder layouts, with as many as five
valves per cylinder to improve efficiency. The
Bugatti Veyron 16.4 operates with a
W16 engine meaning that two
V8 cylinder layouts are positioned next to each other to create the W shape sharing the same crankshaft.
The largest internal combustion engine ever built is the
Wärtsilä-Sulzer RTA96-C, a 14-cylinder, 2-stroke turbocharged diesel engine that was designed to power the
Emma Maersk,
the largest container ship in the world. This engine weighs 2300 tons,
and when running at 102 RPM produces 109,000 bhp (80,080 kW) consuming
some 13.7 tons of fuel each hour.
Heat engine
Main article:
heat engine
Combustion engine
Combustion engines are
heat engines driven by the heat of a
combustion process.
Internal combustion engine
Animation showing the four stages of the
4-stroke combustion engine cycle:
1. Induction
(Fuel enters)
2. Compression
3. Ignition
(Fuel is burnt)
4. Emission
(Exhaust out)
The
internal combustion engine is an engine in which the
combustion of a
fuel (generally,
fossil fuel) occurs with an oxidizer (usually air) in a
combustion chamber. In an internal combustion engine the expansion of the high
temperature and high
pressure gases, which are produced by the combustion, directly applies
force to components of the engine, such as the
pistons or
turbine blades or a
nozzle, and by moving it over a distance, generates useful mechanical
energy.
[9][10][11][12]
External combustion engine
An
external combustion engine (EC engine) is a
heat engine where an internal working
fluid is heated by combustion of an external source, through the engine wall or a
heat exchanger. The
fluid then, by expanding and acting on the
mechanism of the engine produces motion and usable
work.
[13]
The fluid is then cooled, compressed and reused (closed cycle), or
(less commonly) dumped, and cool fluid pulled in (open cycle air
engine).
"
Combustion" refers to
burning fuel with an
oxidizer,
to supply the heat. Engines of similar (or even identical)
configuration and operation may use a supply of heat from other sources
such as nuclear, solar, geothermal or exothermic reactions not involving
combustion; but are not then strictly classed as external combustion
engines, but as external thermal engines.
The working fluid can be a
gas as in a
Stirling engine, or
steam as in a
steam engine or an organic liquid such as n-pentane in an
Organic Rankine cycle. The fluid can be of any composition;
gas is by far the most common, although even single-phase
liquid is sometimes used. In the case of the
steam engine, the fluid changes
phases between liquid and gas...
Air-breathing combustion engines
Air-breathing engines are combustion engines that use the
oxygen in atmospheric air to
oxidise ('burn') the fuel carried, rather than carrying an
oxidiser, as in a
rocket. Theoretically, this should result in a better
specific impulse than for rocket engines.
A continuous stream of air flows through the
Air-breathing engine. This air is compressed, mixed with fuel, ignited and expelled as the exhaust gas.
- Examples
Typical air-breathing engines include:
- duct jet engine
- Turbo-propeller engine
Environmental effects
The operation of engines typically has a negative impact upon
air quality and ambient
sound levels.
There has been a growing emphasis on the pollution producing features
of automotive power systems. This has created new interest in alternate
power sources and internal-combustion engine refinements. Although a few
limited-production battery-powered electric vehicles have appeared,
they have not proved to be competitive owing to costs and operating
characteristics. In the 21st century the diesel engine has been
increasing in popularity with automobile owners. However, the gasoline
engine, with its new emission-control devices to improve emission
performance, has not yet been significantly challenged.
Air quality
Exhaust from a spark ignition engine consists of the following:
nitrogen 70 to 75% (by volume),
water vapor 10 to 12%,
carbon dioxide 10 to 13.5%,
hydrogen 0.5 to 2%,
oxygen 0.2 to 2%,
carbon monoxide: 0.1 to 6%, unburnt
hydrocarbons and partial
oxidation products (e.g.
aldehydes) 0.5 to 1%,
nitrogen monoxide 0.01 to 0.4%,
nitrous oxide <100 ppm,
sulfur dioxide
15 to 60 ppm, traces of other compounds such as fuel additives and
lubricants, also halogen and metallic compounds, and other particles.
[14] Carbon monoxide is highly toxic, and can cause
carbon monoxide poisoning, so it is important to avoid any build-up of the gas in a confined space.
Catalytic converters can reduce toxic emissions, but not completely eliminate them. Also, resulting greenhouse gas emissions, chiefly
carbon dioxide, from the widespread use of engines in the modern industrialized world is contributing to the global
greenhouse effect – a primary concern regarding
global warming.
Noncombustive heat engines
Main article:
heat engine
Some engines convert heat from noncombustive processes into
mechanical work, for example a nuclear power plant uses the heat from
the nuclear reaction to produce steam and drive a steam engine, or a gas
turbine in a rocket engine may be driven by decomposing
hydrogen peroxide.
Apart from the different energy source, the engine is often engineered
much the same as an internal or external combustion engine.
Nonthermal chemically powered motor
Nonthermal motors usually are powered by a chemical reaction, but are not heat engines. Examples include:
Electric motor
Main article:
electric motor
An
electric motor uses
electrical energy to produce
mechanical energy, usually through the interaction of
magnetic fields and
current-carrying conductors. The reverse process, producing electrical energy from mechanical energy, is accomplished by a
generator or
dynamo.
Traction motors
used on vehicles often perform both tasks. Electric motors can be run
as generators and vice versa, although this is not always practical.
Electric motors are ubiquitous, being found in applications as diverse
as industrial fans, blowers and pumps, machine tools, household
appliances,
power tools, and
disk drives. They may be powered by direct current (for example a
battery powered portable device or motor vehicle), or by
alternating current
from a central electrical distribution grid. The smallest motors may be
found in electric wristwatches. Medium-size motors of highly
standardized dimensions and characteristics provide convenient
mechanical power for industrial uses. The very largest electric motors
are used for propulsion of large ships, and for such purposes as
pipeline compressors, with ratings in the thousands of
kilowatts. Electric motors may be classified by the source of electric power, by their internal construction, and by their application.
The physical principle of production of mechanical force by the
interactions of an electric current and a magnetic field was known as
early as 1821. Electric motors of increasing efficiency were constructed
throughout the 19th century, but commercial exploitation of electric
motors on a large scale required efficient electrical generators and
electrical distribution networks.
To reduce the electric
energy consumption from motors and their associated
carbon footprints,
various regulatory authorities in many countries have introduced and
implemented legislation to encourage the manufacture and use of higher
efficiency
electric motors. A well-designed motor can convert over 90% of its input energy into useful power for decades.
[15] When the efficiency of a motor is raised by even a few percentage points, the savings, in
kilowatt hours (and therefore in cost), are enormous. The electrical energy efficiency of a typical industrial
induction motor can be improved by: 1) reducing the electrical losses in the
stator windings (e.g., by increasing the cross-sectional area of the
conductor, improving the
winding technique, and using materials with higher
electrical conductivities, such as
copper), 2) reducing the electrical losses in the
rotor coil or casting (e.g., by using materials with higher electrical conductivities, such as
copper), 3) reducing magnetic losses by using better quality magnetic
steel, 4) improving the
aerodynamics of motors to reduce mechanical windage losses, 5) improving
bearings to reduce
friction losses, and 6) minimizing manufacturing
tolerances.
For further discussion on this subject, see Premium efficiency and Copper in energy efficient motors.)
By convention,
electric engine refers to a railroad
electric locomotive, rather than an electric motor.
Physically powered motor
Some motors are powered by potential energy, for example some
funiculars,
gravity plane and
ropeway conveyors
have used potential energy of water or rocks, and some clocks have a
weight that falls under gravity. Other forms of potential energy include
compressed gases (such as
pneumatic motors), springs (
clockwork motors) and
elastic bands.
Historic
military siege engines included large
catapults,
trebuchets, and (to some extent)
battering rams were powered by potential energy.
Pneumatic motor
A
pneumatic motor is a machine which converts potential energy in the form of
compressed air into
mechanical work.
Pneumatic motors generally convert the compressed air to mechanical
work though either linear or rotary motion. Linear motion can come from
either a diaphragm or piston actuator, while rotary motion is supplied
by either a vane type air motor or piston air motor. Pneumatic motors
have found widespread success in the hand-held tool industry and
continual attempts are being made to expand their use to the
transportation industry. However, pneumatic motors must overcome
efficiency deficiencies before being seen as a viable option in the
transportation industry.
Hydraulic motor
A
hydraulic motor is one that derives its power from a
pressurized fluid. This type of engine can be used to move heavy loads or produce motion.
[16]
Sound levels
In the case of sound levels, engine operation is of greatest impact with respect to mobile sources such as
automobiles
and trucks. Engine noise is a particularly large component of mobile
source noise for vehicles operating at lower speeds, where aerodynamic
and tire noise is less significant.
[17] Petrol and diesel engines are fitted with
mufflers (silencers) to reduce noise.
Efficiency
Depending on the type of engine employed, different rates of efficiency are attained.
The energy of traditional heat engine, doing work only
one-dimensional in three-dimensional thermal motion, mechanics, 1/3, so
the efficiency of heat engine, usually 1/3, 33% = η, the rest of the
2-D, 66%, as uselessthe heat is wasted.
[18][19]
Engines by use
Particularly notable kinds of engines include:
Engine speed
Engine speed is measured in
revolutions per minute
(RPM). Engines may be classified as low-speed, medium-speed or
high-speed but these terms are inexact and depend on the type of engine
being described.
See also
BRASILIA
– Beberapa bagian mesin pesawat DC-10 jatuh, padahal pesawat itu sedang
mengudara di langit Brasil. Akibatnya 22 rumah rusak akibat tertiban
bongkahan mesin seberat ratusan kilogram itu.
