The catalytic converter has a central ceramic part of a honeycomb structure -3-, covered 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.
Catalytic converter
- 1 building
- 2 seal
- 3 cell catalytic converter
Gasoline engines
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 optimal afterburning of the fuel in the catalyst occurs only in this case, if the exhaust gases contain a sufficient amount of fuel.
In order for the fuel to be burned in the catalyst, 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).
Gases at the inlet of the catalytic converter and products at its outlet
Catalytic Converter and Diesel Exhaust Gas Recirculation System
The exhaust gases of the diesel engine are also cleaned in the catalytic converter. This is an unregulated oxidation catalytic converter. Such a catalytic converter converts carbon oxides and hydrocarbon compounds contained in the exhaust gases into CO2 and H2O.
Reducing the concentration of nitrogen oxides in the exhaust gases of a diesel engine (NOx) achieved through the presence of an additional exhaust gas regeneration system (EGR system).
On the exhaust manifold of the engine is a recirculation valve controlled by vacuum. Its task is to direct part of the exhaust gases into the combustion chambers of the engine, which helps to reduce the temperature of the exhaust gases and thereby reduce the concentration of harmful substances.
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