Volkswagen has now advanced the following evolutionary degree of the SCR (selective catalytic aid) components – so-called ‘dual dosing’. Adblue is injected selectively upstream of 2 SCR catalytic converters that are organized in collection. The components is used within the new Passat 2.0 TDI Evo with 110 kW (150 PS), which already meets the technical necessities of the long run Euro 6d emission same old in consequence.
Volkswagen confirms that the present RDE (actual riding emissions) measurements within the new 2.0 TDI Evo with dual dosing reduces NOX ranges via round 80 % as in comparison to the former era of the respective fashions.
Volkswagen will now progressively introduce the brand new era to all fashions with 2.0 TDI Evo engines. Following the two.0 TDI Evo with 110 kW (150 PS) recently fitted within the Passat, the brand new Golfing – quickly to look its global premiere – will likewise characteristic dual dosing in all TDI variants.
Double-checking ammonia slip
The dual dosing procedure calls for a 2d SCR catalytic converter which is situated within the underbody of the automobile. Because the distance to the engine is larger, the exhaust temperature upstream of the second one catalytic converter may also be 100 levels Celsius decrease. This expands the window for the aftertreatment of exhaust gases: whilst exhaust fuel temperatures come on the subject of greater than 500 level Celsius, the components remains to be ready to succeed in very top conversion charges. As well as, a blockading catalytic converter downstream of the SCR components prevents extra ammonia slip.
The cutting edge dual dosing procedure compensates for a system-based drawback of diesel engines. Trendy diesel engines emit much less CO2 than petrol engines as a result of diesel gas has the next power density and the combustion procedure is extra environment friendly. Diesel engines also are matter to big necessities, alternatively, since gas combustion takes position with extra air. The primary constituent of air is nitrogen and this reacts with oxygen right through combustion, thereby forming nitrogen oxides.
Ammonia is had to cut back the nitrogen oxides produced in diesel engines. It’s injected as an aqueous decreasing agent (AdBlue) by means of a dosing module into the exhaust fuel upstream of an SCR catalytic converter. Right here, the answer evaporates; the decreasing agent is divided, combining with steam to shape ammonia. Within the SCR catalytic converter, the ammonia (NH3) then reacts on a distinct coating with the nitrogen oxides (NOx) to shape water and innocuous nitrogen (N2) – the principle constituent of the air we breathe.
In present exhaust fuel remedy methods, a close-coupled SCR catalyst is situated between the turbocharger, the diesel oxidation catalytic converter – which converts uncombusted hydrocarbons – and the versatile connecting piece to the silencer pipe. The SCR coating is implemented to the honeycomb construction of the diesel particulate clear out, thereby enabling a unmarried element to accomplish a number of purposes. The close-coupled association implies that the exhaust fuel temperatures required for prime conversion charges may also be completed briefly after a chilly get started – the perfect vary for conversion charges of greater than 90 % is between 220 level Celsius and 350 level Celsius. Those stipulations are met in lots of working eventualities.
Conversion charges don’t drop above 350 level Celsius – due to dual dosing-system. Temperatures at this degree happen, as an example, when riding at top speeds at the dual carriageway, at top engine speeds over extended classes of time and when riding uphill, particularly if the automobile is totally loaded or towing a trailer.
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