SCR-system
Function Principle
The SCR-System works in the following way: An aqueous urea dilution according to DIN 70040 is sprayed to the exhaust gases and provides a reduction of NOx up to 80%. This dilution is also well-known under the brand name "AdBlue“. This HWL acts as a reducing agent and is transformed with the help of a catalytic converter into ammonia (NH3). The ammonia is then reacting with the NOx gases into harmless water and nitrogen. This special system has to be created, because a normal three-way catalytic converter can only be used in petrol engines due to the oxygen overplus in the exhaust gases of a diesel engine. The urea dilution is located in a separate tank, which is heated electrically or through the waste heat of the en-gine. A pump-/ dosing unit conditions the dilution and sprays it into the exhaust gases during the operation mode. The quantity depends on load and engine revolutions.
This aerosol meets afterwards a special coated SCR-catalytic converter. The converter is enabling the chemical reduction which reduces the NOx gases by 80%. The entire process is supervised by the SCR-Control Unit.
Because of the great demand the urea dilution is today available at nearly all filling stations and can be refilled in an easy way. By the way the HWL consumption is approximatly 5% of the fuel consumption. Furthermore the latter ought to be reduced by the use of a SCR-System.
Function principle
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