The Hindu Business Line : Blue is the new Green

Mercedes Benz’s aim to take its diesel luxury passenger cars to the US, considered widely to be the most emissions-conscious market, where till now diesel (both the cars and the fuel) has nearly been entirely absent, is becoming possible due to its latest diesel engine technology.

Called BLUETEC, the purpose behind the development of this new technology for Mercedes Benz was to reduce substantially nitrogen oxides, a key polluting constituent of diesel engines. There are different polluting components in petrol and diesel engines. In the case of the latter, particulate matter (soot), un-burnt hydrocarbons and nitrogen oxides (NOx) are the main.

Reducing NOX

The central elements of Mercedes’ BLUETEC technology consist of two systems that focus on NOx reduction, even as these are combined with other systems to reduce the amount of particulate matter in the emissions.

The award winning modular BLUETEC technology package, which has seen progressive development since 2002, includes familiar systems such as the oxidation type catalytic converter and particulate traps, in addition to optimised, new generation common rail diesel engines.

Mercedes’ BLUETEC systems work to break down the NOx emissions into nitrogen and water vapour. For example, in the first production car equipped with this system, the E 320 BLUETEC, a complex catalytic converter system consisting of an improved storage-type nitrogen-oxide catalytic converter and an SCR (selective catalytic reduction) catalytic converter are in operation.

Under normal operating conditions, the NOx from the exhaust gas is collected in this storage-type catalytic converter cycle. Through regular adjustment of the fuel-air mixture inside the engine, the combustion process and, thus, the composition of the exhaust gases, is modified for a short period. The NOx is first separated and there is also a particulate filter that collects the soot and burns it off after the filter is full.

Perfecting the system

The SCR is complex catalytic converter, but Mercedes has further perfected the system, making it even more effective with the addition of what it calls Adblue injection. The process involved here requires the injection of ammonia (liquid urea), into the pre-treated exhaust gas. With the Adblue injection into the collected NOx, the ammonia reacts and breaks down the pollutant into harmless nitrogen and water in the downstream SCR catalytic converter. This is currently the most efficient method of exhaust gas after-treatment in diesel engines.

Mercedes Benz has used BLUETEC technology with Adblue injection successfully in its commercial vehicles in Europe. These vehicles are already capable of meeting Euro V emission norms that only come into effect by 2009.

At this year’s Geneva Motor Show, Mercedes has also showcased a new Vision C220 with BLUETEC technology. This new C-class sedan is capable of meeting the even stricter Euro 6 emission standard that will be applicable to all new vehicles Europe-wide only from 2015. The Vision C 220 BLUETEC is also extremely economical and consumes only 5.5 litres of diesel per 100 km.

Mercedes Benz India can bring in the E320 CDI BLUETEC, which has won the 2007 World Green Car award. But, unfortunately, for this E-class saloon to be driven in India, we will need supply of ultra low sulphur diesel of consistently high quality.

— S. Muralidhar