The Emission System

By: Kevin Chung

Picture Credit: repairpal.com

              As global warming continues to be a pressing matter for us, systems and energy conservative inventions have been created to reduce the amount of pollutants released into the atmosphere. One of these is the emission systems in our cars. The purpose of the emission system is to limit the amount of discharge of noxious gases like carbon monoxide, hydrocarbons, and oxides of nitrogen, from the internal-combustion engine. So, a variety of systems have been created to deal with these emissions.

              The crankcase- a portion of the of the engine block below the cylinder where the crankshaft is located- leaked gases are combined with ventilating air to be returned to the intake manifold for re-burning. The part that performs this function is the PCV valve. The PCV valve acts like a small calibrated vacuum leak, allowing it to siphon air through the crankcase, taking moisture and leaked gases that would pollute the atmosphere.

              To control the exhaust emissions, two types of systems are used: the air injection system, and the EGR system (exhaust gas recirculation). In an air-injection system, the engine drive pump combines air with unburned hydrocarbons and carbon monoxide at high temperatures and continues the combustion process. This is so that unburned hydrocarbons aren’t released into the atmosphere and conserves energy. Now in an EGR, a portion of exhaust gas is taken back to the cylinder head. This is so they’re combined with the fuel-air mixture for combustion. The recycled gas’ purpose is to lower the temperature of combustion, so that less nitrogen oxides are produced during combustion.

              Lastly, the catalytic converter, which is used for additional combustion. It has an insulted chamber of a ceramic honeycomb structure coated with a thin layer of metals like platinum. As the exhaust gases pass through the honeycomb structure, the metal acts as a catalyst to convert the gases into water vapor, carbon dioxide, and nitrogen, which aren’t as harmful to the environment. If you liked this post or want to add something, leave a comment, and I’ll try to respond as soon as I can.

                                                                     Sources

"Emission Control System." Encyclopedia Britannica Online. Encyclopedia Britannica, n.d. Web. 23 Oct.      2016.