DaimlerChrysler BlueTec

BlueTec is DaimlerChrysler's name for its two nitrogen oxide (NOx) reducing systems, for use in their Diesel automobile engines. One is a urea based reductant called AdBlue, the other is called DeNOx and uses an oxidising catalytic converter and particulate filter combined with other NOx reducing systems. Both systems are designed to reduce pollutant emissions.

The BlueTec was on the Ward's 10 Best Engines list for 2007.



Uses

Mercedes-Benz introduced the systems in the E-Class (using the 'DeNOx' system) and GL-Class (using 'AdBlue') at the 2006 North American International Auto Show as the E320 and GL320 Bluetec vehicles. This system makes these vehicles 45-state and 50-state legal, respectively in the United States, and is expected to meet all emissions regulations through 2009.

A Jeep Grand Cherokee with the same Bluetec engine is also expected, and Mercedes announced tentative plans for a BLUETEC/electric hybrid S-Class.

Volkswagen has introduced the Jetta Clean TDI, the Tiguan concept and the VW Touareg BlueTDI as part of the BlueTec program. All are expected to be introduced in the American market in 2008. The Jetta and the Tiguan use NOx Adsorbers, while the Toureg uses a Selective Catalytic Reduction catalystic converter.

DaimlerChrysler has entered an into agreement with Volkswagen and Audi to share BlueTec technology with them in order to increase the Diesel passenger-vehicle market in the US.


Rationale

The BlueTec system was created because the processes that give diesel engines efficient fuel economy also creates extra emissions of certain pollutants. High compression ratios and lean air-fuel mixtures make high combustion temperatures, which results in more nitrogen oxides and Diesel Particulate Matter (also known as smoke) being released into the atmosphere. While the particulate matter can be controlled with higher injection pressures and particulate filters, the big challenge is limiting NOx (Tier 2 regulations in the US are 0.05 gram per mile of NOx, which is ⅛ of the 0.40 limit in the European Union).


Process

The Bluetec system will use two catalytic converters specifically targeting NOx. The first converter traps the NOx, and later releases it to the second converter which then converts it to nitrogen (N2) and water (H2O). This will make a diesel car legal in 45 states. But to make it pass the more stringent regulations of California, Maine, Massachusetts, New York and Vermont, AdBlue (NH4) will have to be introduced into the system, making the conversion more complete.



The whole exhaust system would work like so:

1. A Diesel oxidation catalyst reduces carbon monoxide (CO) and hydrocarbons (HC) released from the exhaust.

2. A DeNOx catalytic converter begins a preliminary removal of oxides of nitrogen.

3. A particulate filter will trap and store smoke particles, burning them off when the filter gets full.

4. If the above are not sufficient to meet the exhaust specifications, a Selective Catalytic Reduction (SCR) catalytic converter will take the remaining nitrogen oxides and covert them to nitrogen and water. AdBlue will be injected into it to help the conversion.