Engine

Some natural processes, such as atmospheric convection cells convert environmental heat into motion (e.g. in the form of rising air currents).

Mechanical energy is of particular importance in transportation, but also plays a role in many industrial processes such as cutting, grinding, crushing, and mixing.

Chemical heat engines designed to operate outside of Earth's atmosphere (e.g. rockets, deeply submerged submarines) need to carry an additional fuel component called the oxidizer (although there exist super-oxidizers suitable for use in rockets, such as fluorine, a more powerful oxidant than oxygen itself); or the application needs to obtain heat by non-chemical means, such as by means of nuclear reactions.

Pre-industrial weapons of war, such as catapults, trebuchets and battering rams, were called siege engines, and knowledge of how to construct them was often treated as a military secret.

[5] In some engineering jargons, the two words have different meanings, in which engine is a device that burns or otherwise consumes fuel, changing its chemical composition, and a motor is a device driven by electricity, air, or hydraulic pressure, which does not change the chemical composition of its energy source.

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.

Another way of looking at it is that a motor receives power from an external source, and then converts it into mechanical energy, while an engine creates power from pressure (derived directly from the explosive force of combustion or other chemical reaction, or secondarily from the action of some such force on other substances such as air, water, or steam).

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.

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.

More sophisticated small devices, such as the Antikythera Mechanism used complex trains of gears and dials to act as calendars or predict astronomical events.

[10] In the medieval Islamic world, such advances made it possible to mechanize many industrial tasks previously carried out by manual labour.

Driven by gunpowder, this 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.

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.

As for internal combustion piston engines, these were tested in France in 1807 by de Rivaz and independently, by the Niépce brothers.

[15] In 1877, the Otto cycle 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.

The first commercially successful automobile, created by Karl Benz, added to the interest in light and powerful engines.

However, in recent years, turbocharged Diesel engines have become increasingly popular in automobiles, especially outside of the United States, even for quite small cars.

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.

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.

Though a few limited-production battery-powered electric vehicles have appeared, they have not proved competitive owing to costs and operating characteristics.

Exhaust gas 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.

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.

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.

Historic military siege engines included large catapults, trebuchets, and (to some extent) battering rams were powered by potential energy.

A pneumatic motor is a machine that converts potential energy in the form of compressed air into mechanical work.

Pneumatic motors generally convert the compressed air to mechanical work through either linear or rotary motion.

Thrust is the force exerted on an airplane as a consequence of its propeller or jet engine accelerating the air passing through it.