Engine

An engine or motor is a <a href="/facts/Machine/Dq1W2kwI">machine</a> designed to convert one or more forms of <a href="/facts/Energy/wd8PrQM7">energy</a> into <a href="/facts/Motion_(physics)/dCnP7MlB">mechanical energy</a>.
Available energy sources include <a href="/facts/Potential_energy/I03KLbmn">potential energy</a> (e.g. energy of the Earth's <a href="/facts/Gravitational_field/K1uTmJFy">gravitational field</a> as exploited in <a href="/facts/Hydroelectric_power_generation/zEeJIK2B">hydroelectric power generation</a>), heat energy (e.g. <a href="/facts/Geothermal_energy/ClKR9sTL">geothermal</a>), <a href="/facts/Chemical_energy/Y3VP3Ifq">chemical energy</a>, <a href="/facts/Electric_potential/Nmqm6hm5">electric potential</a> and nuclear energy (from <a href="/facts/Nuclear_fission/LfkIylvm">nuclear fission</a> or <a href="/facts/Nuclear_fusion/hP0gLDqj">nuclear fusion</a>). Many of these processes generate heat as an intermediate energy form; thus <a href="/facts/Heat_engine/t1gq4r5d">heat engines</a> have special importance. Some natural processes, such as atmospheric <a href="/facts/Convection_cell/4QTnSGww">convection cells</a> convert environmental heat into motion (e.g. in the form of rising air currents). Mechanical energy is of particular importance in <a href="/facts/Transportation/npstdhvc">transportation</a>, but also plays a role in many industrial processes such as cutting, grinding, crushing, and mixing.
Mechanical heat engines convert <a href="/facts/Heat/e9QqQ0B2">heat</a> into work via various thermodynamic processes. The <a href="/facts/Internal_combustion_engine/Ju4BXzj0">internal combustion engine</a> is perhaps the most common example of a mechanical heat engine in which heat from the <a href="/facts/Combustion/ohQoWj8z">combustion</a> of a <a href="/facts/Fuel/H8DIRL1j">fuel</a> causes rapid pressurisation of the gaseous combustion products in the combustion chamber, causing them to expand and drive a <a href="/facts/Piston/z7pN46u7">piston</a>, which turns a <a href="/facts/Crankshaft/oYCe9nB3">crankshaft</a>. Unlike internal combustion engines, a <a href="/facts/Reaction_engine/wgAGHSEz">reaction engine</a> (such as a <a href="/facts/Jet_engine/CJjFpeqt">jet engine</a>) produces <a href="/facts/Thrust/EM04CqV7">thrust</a> by expelling <a href="/facts/Reaction_mass/xQ8dToB5">reaction mass</a>, in accordance with <a href="/facts/Newton%2527s_third_law_of_motion/XKzGTXK1">Newton's third law of motion</a>.
Apart from heat engines, <a href="/facts/Electric_motor/ArD7BGDa">electric motors</a> convert electrical energy into <a href="/facts/Machine_(mechanical)/wTCxFRfs">mechanical</a> motion, <a href="/facts/Pneumatic_motor/GmH8tW1U">pneumatic motors</a> use <a href="/facts/Compressed_air/KEjxE7DG">compressed air</a>, and <a href="/facts/Clockwork_motor/ofYRa6kD">clockwork motors</a> in <a href="/facts/Wind-up_toy/N1agzAPC">wind-up toys</a> use <a href="/facts/Elastic_energy/dI07J3PI">elastic energy</a>. In biological systems, <a href="/facts/Molecular_motor/bQeNM8cy">molecular motors</a>, like <a href="/facts/Myosin/7zGeRkpS">myosins</a> in <a href="/facts/Muscle/dmxrL8pH">muscles</a>, use <a href="/facts/Chemical_energy/Y3VP3Ifq">chemical energy</a> 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. <a href="/facts/Rocket/b6j4keIl">rockets</a>, deeply submerged <a href="/facts/Submarine/6fhcAKHV">submarines</a>) need to carry an additional fuel component called the <a href="/facts/Oxidizer/1FQzB8pQ">oxidizer</a> (although there exist <a href="/facts/Superoxidant/gnjCMvcx">super-oxidizers</a> suitable for use in rockets, such as <a href="/facts/Fluorine/YUV0Fb8m">fluorine</a>, a more powerful oxidant than oxygen itself); or the application needs to obtain heat by non-chemical means, such as by means of <a href="/facts/Nuclear_reaction/202yClUr">nuclear reactions</a>.

Engine open-in-new

Engine