Euro 6 emission standards call for massive cuts in pollution limits for trucks and buses. Dr. Christian Weiskirch from the MAN Truck & Bus Engine Competence Center in Nuremberg explains the innovative technologies used in MAN´s new engines.
Dr. Christian Weiskirch views the engine on the test bed in front of him with great satisfaction. This engine belongs to a new generation of Euro 6 engines which the head of heavy-duty production, engine department, at MAN Truck & Bus was responsible for developing. "These engines really do run super clean," announces Weiskirch proudly. He has spent a long time working with his team at the MAN Truck & Bus Engine Competence Center in Nuremberg to achieve this result.
As of January 2014, all newly registered trucks and buses must comply with the Euro 6 emission standards. By implementing the new guideline, engine manufacturers reduce pollution to a minimum. Under the new standards, the change in emission limits is as far-reaching as all the previous five levels put together. Compared to Euro 5, permissible nitrogen oxide emissions were reduced by 80%. In addition, soot particle emissions of commercial vehicles were cut by 66% in contrast to the previous standard.
The new ceilings for soot particle and nitrogen oxide emissions present a real technological challenge for vehicle manufacturers. This is especially the case because combustion in engines depends on an unalterable physical relationship. Specifically, a decrease in nitrogen oxide emissions generally results in increased fuel consumption.
But parallel with the Euro 6 developments, an increase in fuel efficiency was also required. Over the years, MAN has been able to continuously improve the fuel efficiency of its engines while simultaneously addressing more stringent nitrogen oxide requirements. “This is why our focus was on continuing to keep our customers’ operating costs as low as possible, while ensuring that our vehicles run with the utmost efficiency,” explains Weiskirch. And this was successfully achieved. The new Euro 6 engines are not only eco-friendly, but also cost-effective.
"For many years now, MAN has been implementing the key technologies needed to meet Euro 6 standards“, says Weiskirch. One of these is the common rail injection system that MAN has used in all its engine series since 2004. For the Euro 5 standard, in effect since 2008, MAN had two different solutions that were incorporated in production vehicles: exhaust gas recirculation (EGR) as an in-engine measure, as well as exhaust gas after-treatment with selective catalytic reduction (SCR) in combination with AdBlue (also known as “diesel exhaust fluid”, or DEF). “We used this knowledge and expertise in the design of the new Euro 6 engines. We made a point of tuning these processes to each other, and then added an oxidising catalytic converter and a particle filter,” explains Weiskirch.
As the EGR and SCR systems carry out their complimentary roles, the consumption of fuel and AdBlue is reduced. As a result, the regulated EGR enables an engine to emit less nitrogen oxide, and that means that less AdBlue is needed to reduce nitrogen oxide in the SCR system. To lower fuel consumption, fuel injection in the combustion system was designed in such a manner that combustion is optimised for maximum fuel efficiency and minimum particle emissions. “For our Euro 6 engines, we were able to further increase the efficiency of the exhaust gas aftertreatment by means of the SCR system,” says Weiskirch.
“The biggest challenge was getting the engine components and the exhaust gas after-treatment system to match up,” the expert reports. In addition, Euro 6 also requires an enhanced onboard diagnostics system that continually monitors the exhaust gas after-treatment as well as the nitrogen oxide values. “To make that happen, we had to once again substantially expand our existing system,” explains Weiskirch. In addition to a 66-percent reduction in particle mass emissions, Euro 6 standards also require, for the very first time, compliance with a particle number limit. This specification is fulfilled by an enclosed particle filter, which results in a particle mass reduction by more than 90% compared with Euro 5 standards. The SCR catalytic converter, enclosed particle filter, oxidising catalytic converter and the associated sensor of the SCRT system are compactly designed and housed in the exhaust muffler.
All the changes and modifications undertaken in the new engines were successful. The new Euro 6 trucks are just as fuel-efficient as the generation of vehicles fitted with Euro 5 engines. They are not only eco-friendly, but can also offer customers real value added. Many customers are already delighted with these new vehicles.
1. Exhaust Gas Turbocharger
The two-stage turbocharger increases the engine's efficiency, thereby ensuring lower fuel consumpton and clean low-particulate combustion.
2. Exhaust Gas Recirculation
Decreases the temperature at which fuel combusts in the cylinders, resulting in lower nitrogen oxide emissions.
3. Exhaust Manifold
Exhaust gas from the engine passes through the heat-insulated exhaust pipe into the exhaust muffler for exhaust gas after-treatment.
4. Diesel Oxidising Catalytic Converter
By means of a platinum coating, the oxidising catalytic converter transforms the polluting carbon monoxide and hydrocarbons into nontoxic CO² and water.
5. Particle Filter
The particle filter captures up to 99% of all soot particles from the exhaust gas flow. A chemical process enables the filter to continually reclean itself.
6a. AdBlue Tank
The aqueous urea solution is stored in the AdBlue tank and is used as a reduction agent for the exhaust gas after-treatment in the SCR catalytic converter.
6b. AdBlue Line
The urea solution passes through a heated line from the AdBlue tank to the AdBlue mixer.
7. AdBlue Dosing Module
The electronic dosing module uses sensors to determine the quantity of AdBlue required for nitrogen oxide reduction and injects it into the AdBlue mixer.
8. AdBlue Mixer
In a hydrolysis section in the AdBlue mixer, the injected urea solution turns into ammonia, which is required for the reaction in the subsequent SCR catalytic converter.
9. SCR Catalytic Converter
By the princliple of selective catalytic reduction, the SCR catalytic converter turns most of the nitrogen oxide into harmless nitrogen and oxygen.
10. Ammonia-Blocking Catalytic Converter
The blocking catlytic converter prevents excess ammonia from being emitted.
11. Exhaust Tailpipe (Or Outlet)
The purified exhaust is discharged from the tailpipe. Sensors continuously monitor the nitrogen oxide values.