The occurrence of DANGEROUS INGREDIENTS IN THE ENGINE

Formation of hazardous components in the engine

Formation of hazardous components in the engine

Internal combustion engines are far from being perfect machines. Therefore, despite very modern fuel injection systems, as a byproduct of combustion, substances harmful to our health appear.

The main characteristic of an internal combustion engine is combustion in its cylinders. The combustion is exposed to a mixture of fuel, consisting of hydrocarbons and oxygen from atmospheric air, with the release of mechanical energy, which is the main purpose of the existence of an internal combustion engine.

Ideally, combustion products should be made carbon dioxide (CO2) i water vapor (H2O).

engine

The DPF filter serves to remove soot particles from the diesel engine exhaust

However, in real conditions, in addition to the above ingredients, the exhaust gases also contain excess oxygen (O2) and nitrogen (N2), as well as undesirable ingredients such as carbon monoxide (CO), unburnt carbon (HC), oxides of nitrogen (NOx) ) and particulate matter (PM).

Carbon monoxide is produced by the incomplete combustion of carbon from hydrocarbons in a fuel. Theoretically, in the presence of excess oxygen, that is, in a "lean mixture", there should be no carbon monoxide in the combustion products, but only non-toxic carbon dioxide.

Proper combustion of the engine is a prerequisite for low emissions

Proper combustion of the engine is a prerequisite for low emissions

The measurements, however, showed a carbon monoxide concentration of 1 percent even with a stoichiometric mixture, which theoretically has enough oxygen for complete combustion, and to a lesser extent for a lean mixture, when there is excess air for complete combustion. At high temperatures, CO2 dissociation into CO occurs and the balance of these two compounds is adjusted during the expansion cycle.

Carbon monoxide has a very pronounced toxic effect on humans, so it causes death at a concentration of only 0,3 percent in 30 minutes.

Much of the unburned carbon (HC) that the car releases into the atmosphere is present due to incomplete combustion during the combustion process and also occurs in the presence of sufficient oxygen for complete combustion.

Spark plugs should be changed at the prescribed interval

Spark plugs should be changed at the prescribed interval

This is thought to be due to the extinguishing of the flames in contact with the cold walls of the cylinder, due to the high dilution of the fuel mixture by the residual gases of the previous cycle or the low temperature of the current cycle.

The source of the unburnt carbon may be a mixture in narrow slits, such as the space between the piston and cylinder fire zone, until the flame can reach. Part of the carbon is oxidized during expansion and exhaust.

The allowable concentration of carbon-hydrogen is very low due to their effect on the occurrence of cancerous diseases. Most of the atmospheric air is a mixture of nitrogen and oxygen, which are chemically very stable under normal conditions. However, at temperatures of hundreds of degrees, the oxidation of nitrogen to nitrous monoxide (NO) occurs in part.

Proper valve clearance also affects engine combustion

Proper valve clearance also affects engine combustion

The intensity of this reaction depends on the height of the temperature and pressure in the cylinder, the composition of the mixture and the time available for it to take place. At ambient temperature, cooled nitrogen monoxide is rapidly oxidized in the atmosphere to nitrogen dioxide (NO2). Low temperatures and very high air dilution allow for a long lifetime of nitrogen oxides in the atmosphere. Nitrogen oxides are one of the most responsible compounds for the destruction of forests by acid rain.

Particulate matter occurs predominantly in diesel, while in conventional OTO engines the occurrence of particulate matter is negligible.

During incomplete combustion, solids occur in the form of particles. They consist, depending on the combustion process and the state of operation of the engine, mainly the connected chain of hydrocarbon beads, or soot with a very large specific surface area. Unburned or partially combusted hydrocarbons are deposited on soot, including aldehydes of characteristic odor.

Direct fuel injection systems have noticeably reduced emissions

4-Cylinder Gasoline Engine (04/2011)

Soot is bound to aerosols of fuels and lubricants, as well as sulfates. These solids are also associated with the occurrence of cancerous diseases.

Dipl. Eng. Milan Popović
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