Exhaust aftertreatment solutions for delivery and long-haul trucks support the move to ultra-low NOx emissions
29 Aug 2018 | 3487 Views | By Autocar Professional Bureau
At the 67th International Commercial Vehicle Show (IAA) to be held from September 20-27 in Hanover, Germany, technology company Continental will be presenting solutions to support even more efficient exhaust aftertreatment in trucks.
The primary aim is to ensure more efficient conversion of the nitrogen oxides (NOx) into harmless emissions, ...
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At the 67th International Commercial Vehicle Show (IAA) to be held from September 20-27 in Hanover, Germany, technology company Continental will be presenting solutions to support even more efficient exhaust aftertreatment in trucks.
The primary aim is to ensure more efficient conversion of the nitrogen oxides (NOx) into harmless emissions, whether on heavy-duty long-haul trucks, urban light trucks or municipal vehicles. The challenge centers on ensuring that the exhaust aftertreatment system reaches – and maintains – an efficient working temperature as quickly as possible after starting the engine. However, the possibilities for integrating catalysts and filters differ greatly from vehicle to vehicle. Not all models offer scope for close-coupled mounting of the catalyst and filter. On some models such a configuration may be out of question for many years to come, due to the long design cycles of heavy-duty truck frames.
Continental says it has developed solutions that make it possible to achieve further improvements in NOx conversion efficiency whichever of these two situations applies. At the IAA in Hanover, the company will present both types of solution – close-coupled systems and, alternatively, an architecture based on an innovative combination of diesel injection into the exhaust stream and an electric heating element mounted upstream of the catalyst.
Close-coupled catalyst and filter system. Use of a new ‘concertina-type folding technique’ in the catalyst makes it easier to implement asymmetrical catalyst dimensions that are more closely adapted to the available packaging space.
“In the future, ensuring real-world compliance with new standards will require a vast improvement in the NOx performance of both long-haul and urban commercial vehicles,” says Dr Markus Distelhoff, executive vice-president – Fuel & Exhaust Management Business Unit, Powertrain Division. “The exhaust aftertreatment solutions we are presenting in Hanover for these two different basic architectures contribute both to improved fuel efficiency and reduced NOx emissions.”
Exhaust system with reduced mass and efficient warm-up
In passenger cars, the catalytic converter is often mounted very close to the engine, ensuring that the interior of the catalytic converter reaches the necessary operating temperature as quickly as possible. The same approach is not always possible in a truck, however. On very large tractor units in particular, there is often not enough space to install a sufficiently large close-coupled diesel oxidation catalyst (DOC).
Continental says it has two solutions to this problem. Use of a new ‘concertina-type folding technique’ in the catalyst makes it easier to implement asymmetrical catalyst dimensions that are more closely adapted to the available packaging space.
“With the new folding technique, it is possible to maximize the scope for OEMs to accommodate a close-coupled DOC in heavy-duty trucks,” says Dr Manuel Presti, Program Manager Fuel & Exhaust Management Business Unit. At the same time the slanted metallic CS substrate (CS: crossversal structure), which is able to dispense with a flat intermediate layer, also allows the mass of the system to be reduced by approximately 20 percent.
Where this type of solution is still not possible due to space requirements, Continental alternatively offers a new type of architecture featuring diesel fuel injection into a mixing pipe upstream of the muffler box. A heating disc situated immediately downstream catalytically converts the fuel spray into heat, which is used to warm up the entire catalyst system. “With this configuration and this combination of technologies, only a small quantity of fuel is needed to achieve the necessary heating effect,” Presti adds.
The benefits of this system can be enjoyed in a range of applications – for example in delivery vehicles where ‘postal’-type driving cycles, with frequent engine shutdown, rarely allow adequate engine (and therefore exhaust) temperatures to be achieved. “Another example is refuse collection vehicles, where the engine is running almost constantly at idling speed. In such cases it is virtually impossible to achieve any improvement in NOx conversion without appropriate thermal management in the exhaust system,” says Manuel Presti.
For the actual selective catalytic reduction (SCR) of NOx emissions in the exhaust gas, an aqueous urea solution is injected into the exhaust stream. The new pump (Gen V) offers an optional purge function which empties the urea line when the vehicle is shut down, to avoid frost problems at the nozzle. Alternatively, if a frost-proof nozzle is used, the purge function is not required and faster system readiness can be given priority.
With a capacity of up to 20 kg/h, the pump can feed two injectors. A new filtration strategy protects against the risk of damage due to contaminated urea. The pump is suitable for installation in a variety of mounting positions, allowing easier integration in the vehicle. “In both architectures, our robust NOxsensors play a key role. These sensors can also be directly integrated in the catalyst substrate, allowing them to supply more accurate data from within the process itself, and therefore to provide even more precise NOx control,” says Presti.