The term internal combustion engine tends to refer to reciprocating piston engines in which combustion is intermittent, although continuous combustion engines, such as jet engines, rockets, and gas turbines are also internal combustion engines.
In the seventeenth century, Sir Samuel Morland, an English inventor, used gunpowder to drive water pumps, creating the first rudimentary internal combustion engine, but it was not until 1794 that Robert Street actually built a compressionless engine. In 1879 Karl Benz designed and built the four-stroke engine that powered the first automobiles.
The most significant distinction between modern internal combustion engines and the early designs is the use of in-cylinder compression. The first internal combustion engines did not have compression, but ran on an air, fuel mixture sucked in during the first part of the intake stroke.
Within the internal combustion engine, the combustion of fuel and an oxidizer (normally air) occurs in confined spaces, the combustion chambers. This exothermic reaction produces gases at high temperatures and pressures, which expand, resulting in the movement of pistons that slide within the combustion chambers. Steam engines, in contrast, use external combustion chambers to heat a separate working fluid, which in turn moves the pistons.
The most common internal combustion engines are the four-stroke, gasoline-powered, spark-ignition engines, which are also used in the aeronautics industry. Internal combustion engines, generally using petroleum, are used for mobile propulsion in automobiles, trucks, motorcycles, boats, and in a wide variety of aircraft and locomotives.
