Catalytic converter
1 - body
2 - seal
3 - cells of the catalytic converter
All engines are equipped with one or more exhaust gas aftertreatment catalytic converters.
The catalytic converter has a central ceramic part of a honeycomb structure -3- coated with a carrier layer. On the carrier layer are noble metal salts that act as converters. The catalytic converter is fixed in the housing -1- by means of an insulating support layer -2-, which simultaneously compensates for the thermal expansion of the catalytic converter.
In order to reduce harmful emissions with a catalytic converter, injection systems must accurately dose the amount of injected fuel required for combustion. The oxygen sensor is located in the exhaust pipe before the catalytic converter and is washed by the exhaust gas flow. The oxygen sensor is an electronic sensor that measures the oxygen content in exhaust gases and presents it as a voltage fluctuation. Information from the oxygen sensor is transmitted to the injection system control unit. The obtained value allows you to adjust the composition of the air-gasoline mixture. On the one hand, this is necessary, since operating conditions are constantly changing (idle, full throttle), on the other hand, since the optimal post-combustion of the fuel in the catalytic converter occurs only in this case, if the exhaust gases contain a sufficient amount of fuel.
In order for the afterburning of fuel to occur in the catalytic converter, it is necessary to have a temperature of 300-800°C. This requires a higher fuel content in the mixture than for clean combustion.
The catalytic converters used in gasoline engines are so-called three-function devices. In a regulated conversion process, carbon monoxide is oxidized (SO) and hydrocarbon (NS), as well as a reduction in the concentration of nitrogen oxides (NOx).