Mercedes-Benz to introduce the first diesel models with AdBlue injection in America
As a modular concept for an effective reduction in the fuel consumption and emissions of diesel vehicles, the BlueTEC technology developed by Mercedes-Benz puts in place a number of coordinated measures which both minimise untreated emissions using in-engine features and ensure efficient exhaust gas aftertreatment. All relevant emissions components are successively and concertedly reduced to a minimum, in part by using an oxidising catalytic converter and a particulate filter. The most important goal is to achieve a drastic reduction in nitrogen oxide emissions, the only exhaust gas constituent which has inherently higher levels in diesel engines than in petrol engines.
Mercedes-Benz has developed two versions to this end. In the E 320 BlueTEC Saloon (introduced in October 2006) available in the USA and the E 300 BlueTEC sold in Europe, an oxidising catalytic converter and a particulate filter are combined with a particularly durable NOx storage-type catalytic converter and a special SCR (Selective Catalytic Reduction) converter. The second BlueTEC version is used for the new GL 320 BlueTEC, ML 320 BlueTEC and R 320 BlueTEC models. In this case AdBlue, an aqueous urea solution is injected into the stream of exhaust gases. This releases ammonia, of which 80 percent is reduced to form harmless nitrogen and water by the downstream SCR converter. The urea solution is held in a separate onboard tank, and fed to the metering module by means of a pump. As the average consumption of AdBlue is only around 0.1 litres per 100 kilometres (or 1 to 3 percent of diesel consumption), the tank can be of such a size that it only needs to be refilled at the workshop during regular service intervals. The tank capacity is 28 litres in the R 320 BlueTEC and ML 320 BlueTEC, and 32 litres in the GL 320 BlueTEC.
This innovative emissions control technology follows the following stages:
Optimisation of the engines and their combustion processes to reduce untreated emissions as far as possible. These measures include electronic engine management, four-valve technology, third-generation common-rail direct injection with piezo-electric injectors, a turbocharger with variable turbine geometry and exhaust gas recirculation.
Oxidising catalytic converters are used to minimise emissions of carbon monoxide (CO) and unburned hydrocarbons (HC).
A particulate filter, which has been standard equipment in all Mercedes-Benz diesel models in many countries since summer 2005, reduces particulate emissions to a barely measurable level. This easily meets both the current EU4 particulate limits (0.025 grams/kilometre) and the current US limits.
Nitrogen oxides are reduced by a storage-type NOx catalytic converter combined with an SCR catalytic converter, or by AdBlue injection combined with an SCR catalytic converter. These effective aftertreatment methods allow the nitrogen oxide emissions of BlueTEC vehicles to be reduced by up to 80 percent.
