November 18, 2008

The Internal Combustion Engine

Internal Combustion Engine

The engines in vehicles is a rather broad but interesting subject. People may be amazed to know that the ones currently in use today were drawn on several hundreds of blueprints before they were distributed to the market. The present models are the result of over a century worth of brainstorming and experience and will further influence the models of the future.

What is the ICE (Internal Combustion Engine)?

ICE stands for internal combustion engine wherein the combustion of fuel and an oxidizer occurs. The combustion chamber is the space where everything happens causing an exothermic reaction that produces gas at a high pressure and temperature. The expanding hot gases will directly put pressure on solid engine parts causing them to move. Pistons, rotors or the engine itself then begins movement which propels the entire vehicle.

The very first models of the ICE ran on an air/fuel mixture rather than compression. The initial part of the intake stroke sucks or blows in the mixture. Modern ICEs already incorporates in-cylinder compression. The engines were used in a variety of methods and industries like generators, boats, aircrafts and most particularly, automobiles.

The Operation

The internal combustion engine operates using a four-stroke cycle or the Otto cycle. The cycle involves four phases namely: induction, compression, power and exhaust. All of these aim to create an exothermic chemical process to start vehicle propulsion. During induction, oxygen or other oxidizers are introduced into the cylinder to act with the fuel. Compression then begins as the gases start a reaction 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 byproducts 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.

Where Does Gasoline Come In?

There are electric/gasoline-type systems that use a combination of lead-acid battery plus an induction coil to create a high-voltage electrical spark. The spark will then ignite the mix of air and fuel within the cylinder. The battery is rechargeable even during operation through an alternator or generator driven by the engine itself. 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.

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. HCCI engines also require only heat and pressure but take in air and fuel. This process makes diesel and HCCI engines more prone to 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 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 byproducts 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. This is also known as quenching of the flame.

Both gasoline and diesel engines emit harmful gases that can be dangerous to humans as well as the environment. The greenhouse gases start trapping hot air within the atmosphere instead of allowing them to exit to space leading to global warming. The rise of the ICE or internal combustion engine finally showed its major flaw which is pollution.

No comments: