Internal Combustion Engine

History

The term internal combustion engine (ICE) refers to an engine where expansion of gases, produced by the combustion, apply force to a movable component of the engine.  The combustion of fuel occurs in a chamber with an oxidiser, typically air.  An exothermic reaction occurs that produces a gas at high pressure and temperature. The increasing hot gases will immediately put pressure on solid engine parts causing them to move.  Pistons, rotors or the engine itself then begins moving, causing the entire automobile to be propelled.

The first internal combustion engine was designed by the Dutch scientist Christian Huygens in 1678;  it was to have been fueled with gunpowder, but it was never built.  About 1860 a French inventor, Etienne Lenoir (1822-1900), built the first practical internal combustion engine; it burned illuminating gas.  In 1866 two German engineers, Eugen Langen (1833-1895) and Nikolaus August Otto (1832-1891), developed a more efficient gas engine, and in 1876 Otto built a four cycle engine, a prototype of the so-called Otto-cycle engines used in most modern automobiles and airplanes.

Operation 

The typical internal combustion engine uses a four-stroke cycle or Otto cycle. The cycle involves four phases namely:  induction, compression, power and exhaust.  These phases combine to generate an exothermic chemical process causing vehicle propulsion. During induction, oxygen or other oxidizers are introduced into the cylinder to act with the fuel.  Compression occurs as the gases start a response that continuously increase temperature and pressure within the cylinder.

When enough pressure is applied on the corresponding engine parts, the engine begins to gain power through movement coming from direct force application. The aftermath of the entire compression process will lead to exhaustion of by products like carbon monoxide, carbon dioxide and nitrogen wastes. These gases are freely emitted into the atmosphere. The combustion process is started through engine ignition using the spark ignition method or the compression ignition system.

Gasoline

Electric/gasoline systems use a combination of lead-acid battery plus an induction coil to create a high-voltage electrical spark.  The spark ignites the mix of air and fuel within the cylinder.  Gasoline engines get an air and gasoline mixture to be compressed to less than 185 psi.   The spark plug ignites the mixture during compression within the cylinder.  The battery is recharged during operation through an alternator or generator driven by the engine itself.  

As for diesel engines, these require only heat and pressure produced by the engine during the compression process for ignition. Diesel compression is approximately three times higher compared to a gasoline engine. Diesel engines use air only. Some diesel fuel is sprayed into the cylinder with the use of a fuel injector just before peak compression to start ignition immediately.  Homogeneous charge compression ignition (HCCI) engines also require only heat and pressure but take in fuel as well as air.  The compression process for diesel and HCCI engines is less robust for cold starts.

The Polluting Effects

Combustion products or the hot gases ignited and burnt inside the engine will have higher amounts of energy compared to the compressed fuel and air mixture. After available energy are used up to drive the engine pistons, remaining combustion products will be vented or exhausted through a valve or the exhaust outlet to bring back the piston in its original state also called top dead center (TDC).  Any heat which is not used up will become a waste product due to be removed from the engine via a liquid or air cooling system.

Air pollution emissions then result from incomplete combustion of carbonaceous fuel.  Examples of engine by products are carbon monoxide, soot, nitrogen wastes, sulfur and uncombusted hydrocarbons. These also result if the products did not operate near the stoichiometric ratio required for effective combustion.  The fuel would not have burnt very well due to factors like cool cylinder walls or lack of air. 

Both gasoline and diesel engines emit harmful gases that can be dangerous to humans as well as the environment. The greenhouse gases are trapped within the atmosphere leading to global warming.