There are many different types of internal combustion engines. They can be classified by:
- Application : Automobile, truck, locomotive, light aircraft, marine, portable power system, power generation.
- Basic engine design : Reciprocating engine (in turn subdivided by arrangement of cylinder: e.g.,in-line, V, radial, opposed), rotary engines (Wankel and other geometris)
- Working cycle. Four stroke cycle: naturally aspirated (admitting atmospheric air), supercharged (admitting precompressed fresh mixture), and turbocharged (admitting fresh mixture compressed in a compressor driven by an exhaust turbine), two stroke cycle: crankcase scavenged, supercharged, and turbocharged.
- Valve or port design and location. Overhead (or I-head) valves, underhead (or L-head) valves, rotary valves, cross-scavenged porting (inlet and exhaust ports on opposite sides of cylinder at one end), loop-scavenged porting (inlet and exhaust ports on same side of cylinder at one end), through or uniflow scavenged (inlet and exhaust ports or valves at different ends of cylinder).
- Fuel. Gasoline (or petrol), fuel oil (or diesel fuel), natural gas, liquid petroleum gas, alcohols (methanol, ethanol), hydrogen, dual fuel.
- Method of mixture preparation. Carburetion, fuel injection into the intake ports or intake manifold, fuel injection into the engine cylinder.
- Method of ignition. Spark ignition (in conventional engines where the mixture is uniform and in stratified-charge engines where the mixture is non-uniform), compression ignition (in conventional diesels, as well as ignition in gas engines by pilot injection of fuel oil).
- Combustion chamber design. Open chamber (many designs: e.g., disc, wedge, hemisphere, bowl-in-piston), divided chamber (small and large auxiliary chambers; many designs: e.g., swirl chambers, prechambers).
- Method of load control. Throttling of fuel and air flow together so mixture composition is essentially unchanged, control of fuel flow alone, a combination of these.
- Method of cooling. Water cooled, air cooled, uncooled (other than by natural
convection and radiation)