LUXEMBOURG — Delphi Automotive has developed a breakthrough in NOx control for diesel engines with a new selective catalytic reduction (SCR) system that improves the performance, packaging and long-term reliability of the system as well as reduces vehicle CO2 emissions by up to 1g/km over any comparable system, according to the company.
By injecting aqueous urea solution into a SCR system at up to four times the pressure of
any previous system, which allows the catalyst to be close coupled to the engine, Delphi says it has solved many of the issues associated with other SCR systems.
"As the EU regulations for CO2 emissions take effect, every additional gram of CO2 could potentially cost the manufacturer up to 95 euros per vehicle in future emissions-related penalties," said Peter Spadafora, Delphi product team leader, SCR Systems. "The Delphi SCR system reduces both NOx and CO2 emissions in order to add maximum value for our customers."
The system consists of three basic modules. The SCR doser (an injector with integrated
high-pressure pump) is mounted in the exhaust line just ahead of the SCR catalyst and injects the urea solution at 20 bar directly into the exhaust stream. The solution is supplied to the injector by a low pressure pump within the Urea Delivery Module (UDM) in the remote urea tank. The third element of the system is the electronics and software used to control the dosing subsystem.
The high pressure of the dosing injector, combined with an innovative insulation
arrangement, prevents the urea solution from boiling within the doser, allowing its tip to be directly exposed to the hot exhaust. This architecture puts more energy into the urea spray, which requires less mixing energy from the exhaust and eliminates deposit formation at the nozzle tip. It also ensures consistent spray performance over the entire life of the system. The superior performance of the Delphi doser allows exhaust designers to move the SCR catalyst closer to the engine which in turn saves on CO2 as catalyst heating and light-off strategies can be reduced, the company says.
Unlike alternative systems that use timed injector opening, the Delphi system uses a
positive displacement solenoid pump that delivers an accurate, metered quantity of urea through the injector, regardless of supply pressure, throughout the lifetime of the system.
"As an experienced diesel fuel injection supplier, Delphi has the ideal combination of design and high-volume precision manufacturing expertise necessary to develop this new system," said Spadafora. "In total, we now have 52 SCR patents and another 20 applications pending."
Additionally, the Urea Delivery Module (UDM) can be customized to integrate the functions of urea level sensing, lifetime filtration, heating for defrosting in winter and a delivery pump, packaging conveniently into the base of the tank. The delivery pump is only required to pressurize the urea solution to prevent boiling in the feed lines.
