Engine Overview:

  • Engines convert various forms of energy into mechanical work.
  • Available energy sources for engines include potential, heat, chemical, electric, and nuclear energy.
  • Mechanical heat engines convert heat into work through thermodynamic processes.
  • Electric motors convert electrical energy into mechanical motion.
  • Biological systems use chemical energy to create motion.

Engine Types and Components:

  • Engines can be categorized based on energy input and output motion.
  • Heat engines are driven by the heat of a combustion process.
  • Combustion engines use the heat of a combustion process.
  • Internal combustion engines use fossil fuel combustion for power.
  • External combustion engines operate through an external heat source.
  • Engines exert torque or produce thrust.
  • Examples of torque-producing engines include automobile gasoline and diesel engines.
  • Examples of engines producing thrust include turbofans and rockets.

Historical Development:

  • Simple machines like the lever date back to prehistoric times.
  • Engines using human, animal, water, wind, and steam power existed in antiquity.
  • Water-powered mills were built in the 1st century BC.
  • Use of water wheels in mills spread throughout the Roman Empire.
  • Notable advancements in medieval and industrial eras contributed to engine evolution.

Environmental Impact and Efficiency:

  • Engines negatively impact air quality and ambient sound levels.
  • Growing emphasis on pollution from automotive power systems.
  • Interest in alternate power sources and engine refinements.
  • Diesel engines are becoming more popular due to their efficiency.
  • Hybrid engines combining gasoline and electric components are gaining popularity.
  • Efficiency, emissions, and air quality are key considerations in engine design and use.

Performance and Technology:

  • Speed, thrust, torque, power, and efficiency are key performance metrics.
  • Sound levels vary based on engine type and operation.
  • Different types of engines are used in various applications like aircraft, automobiles, and marine propulsion.
  • Hybrid engines offer flexibility in energy sources and improved efficiency.
  • Various resources and links provide additional information on engines and related technologies.
Engine (Wikipedia)

An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy.

An animation showing the four stages of the four-stroke gasoline-fueled internal combustion cycle with electrical ignition source:
  1. Induction (Fuel enters)
  2. Compression
  3. Ignition (Fuel is burnt)
  4. Emission (Exhaust out)
Jet engines use the heat of combustion to generate a high-velocity exhaust as a form of reaction engine. Mechanical energy to power the aircraft's electrical and hydraulic systems can be taken from the turbine shaft, but thrust is produced by expelled exhaust gas.

Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power generation), heat energy (e.g. geothermal), chemical energy, electric potential and nuclear energy (from nuclear fission or nuclear fusion). Many of these processes generate heat as an intermediate energy form, so heat engines have special importance. 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.

Mechanical heat engines convert heat into work via various thermodynamic processes. The internal combustion engine is perhaps the most common example of a mechanical heat engine, in which heat from the combustion of a fuel causes rapid pressurisation of the gaseous combustion products in the combustion chamber, causing them to expand and drive a piston, which turns a crankshaft. Unlike internal combustion engines, a reaction engine (such as a jet engine) produces thrust by expelling reaction mass, in accordance with Newton's third law of motion.

Apart from heat engines, electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air, and clockwork motors in wind-up toys use elastic energy. In biological systems, molecular motors, like myosins in muscles, use chemical energy to create forces and ultimately motion (a chemical engine, but not a heat engine).

Chemical heat engines which employ air (ambient atmospheric gas) as a part of the fuel reaction are regarded as airbreathing engines. 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.


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