Internal combustion engines are used to power a variety of motorized systems, including automobiles, generators, farm equipment, aircraft, and more. There are several different types of internal combustion engine designs, each with specific applications and functionality.
What are Reciprocating Engines?
The largest category of internal combustion engines is reciprocating engines. Some specific designs include:
- Four-stroke engine – This type of engine is one of the most widely used engine types, as it is used in most automobile, truck, and propeller aircraft. In this design, the four phases of the engine process take place within four stroked, or two cycles of piston motion.
- Two-stroke engine – The functionality of a two-stroke engine is very similar to that of a four-stroke engine, but in this case all four phases of the engine process take place in two strokes, or one cycle of piston motion. Some of the most common applications for two-stroke engines are small motor craft, gas-powered landscaping equipment, and electrical generators.
- Five- and Six-stroke Engine – Engines with higher “stroke” counts can be more accurately classified as having more phases, rather than strokes. A five-stroke Delatour engine adds a refrigeration cycle and designers claim improved efficiency. There are two types of six-stroke engines. The first type captures heat from the compression ignition phase to generate steam and allow for an unpowered third piston cycle. The second type is actually a combination of two opposing pistons, one operating on a four-stroke design and the other operating on a two-stroke design.
What are Rotary Engines?
Rotary engines, such as the Wankel Engine, do not have pistons, so they are classified as “four-phase” engines rather than “four-stroke” engines. A rotary engine basically contains an ovoid housing and a triangular rotor. The engine phases occur in the spaces between the rotor surfaces and the housing. The design directly generates rotary motion of the rotor, as opposed to translating the reciprocating motion of pistons to rotary motion via a crankshaft.
What Are Sustained Combustion Engines?
Sustained combustion engines perform the same engine processes as other types of internal combustion engines, but the processes occur in different portions of the engine simultaneously. There are two primary categories of sustained combustion engines: gas turbines and jet engines.
- Gas turbines – A gas turbine has dedicated components for the compression, combustion, and expansion, allowing for a continuous power output, unlike reciprocating engines that alternate between phases and provide increments of power. Gas turbines are primarily found in power plants and naval vessels, but do have other minor applications.
- Jet Engines – Jet engines expel the expanded gas from the compression process through a nozzle to create thrust. Most, but not all jet engine designs are considered internal combustion engines. Jet engines can be based on a gas turbine with a liquid fuel, or a rocket, using either solid or liquid propellants. A traditional jet engine has a variety of moving parts, while a rocket has very few moving parts. Jet engines are primarily used for high speed aircraft, while rockets are used for spacecraft and missiles.
Internal combustion engines convert fuel to mechanical motion for a variety of applications. While a variety of engine designs exist, each design has its own benefits when viewed in terms of its specific application.
Sources
Singer, Charles Joseph; Raper, Richard, A History of Technology: The Internal Combustion Engine, edited by Charles Singer ... [et al.], Clarendon Press, 1954-1978
"Inside Bruce Crower’s Six-Stroke Engine". Autoweek website, December 26, 2006.
US Patent 2,988,065 Rotary Internal Combustion Engine, June 13, 1961.
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