Delphi high-pressure common rail systems see breakthrough 01 May 2012
Delphi Automotive revealed details of its 'breakthrough' common rail fuel system technology for heavy-duty diesel engines at last month's Vienna Motor Symposium (April 26-27).
Delphi says that a combination of class-leading injector design, configurable pump layout and sophisticated air and fuel control strategies has provided a highly-flexible, modular solution for engines between 7 and 16 litres displacement.
It also says that, as a result, vehicle manufacturers will be able to meet tough Euro 6 emissions standards "without significant modification to their base engines".
Three configurations will be available: two distributed pump common rail systems (DPCRS), in which pressure is provided by several separate pumping units, and a remote pump common rail system (RPCRS), which is similar to traditional common rail layouts.
Running initially at 2,700bar injection pressure, Delphi says the technology is capable of operating at up to 3,000bar to meet the requirements of future legislation, beyond Euro 6 that might limit the permissible CO2 emissions from heavy commercial vehicles.
"For Delphi, Euro 6 represents evolution, not revolution," comments David Draper, engineering director, Delphi Heavy-Duty Diesel Systems.
"We have substantial experience with very high pressures and already manufacture some of the most sophisticated control valves available," he continues.
"Combining this with innovative new architectures and control systems has allowed us to significantly reduce the cost of Euro 6 compliance for our customers while continuing to improve fuel economy and CO2 emissions," adds Draper.
DPCRS technology is aimed at engines currently using electronic unit injector (EUI) systems or electronic unit pump (EUP) systems, he explains, because the installation envelope is the same as Delphi's current products.
The ultra-high rail pressure is provided by separate pumping elements that can operate from either cam-in-block (F2P system) or cam-in-head (F2E system) engines.
The overhead cam arrangement allows all high-pressure elements of the system to be contained within the rocker cover and neither system requires significant change to the castings of an engine already using EUI or EUP, he insists.
Meanwhile, for the first time in the heavy-duty diesel market, a latching outlet metering valve (OMV) is used on each of the pumping elements. Draper says that digital control of the pumping elements by their OMVs produces an exceptional transient response, typically 0.2sec for a 2,000bar increase, while also providing selectable displacement functionality.
Further, the improved spray penetration and in-cylinder mixing achieved with high rail pressures results in significant reductions in smoke and NOx emissions when operating at high EGR (exhaust gas recirculation) levels," he says.
Engine tests have demonstrated a 50% smoke reduction combined with engine-out NOx levels down at less than 2g/kWh. Evolution of the same technology will allow a cost-effective path to next-generation emissions compliance, says Draper.
"The key challenge for the Euro 6 injectors is ensuring exceptional fuelling accuracy at very high pressures, with no significant change over the lifetime of the system," explains Draper.
"Our new system has been proven to comfortably meet our service life target of 1.6 million km."
As for Delphi's new Euro 6 and US13 ECU (Electronic Truck Controller: ETC3) common-rail control system, this is an evolution of the Euro 5 and US10 engine and vehicle controller, for 12V and 24V applications.
Software development for Euro 6 was driven by requirements to compensate for potential variation in engine performance and emissions, such as variations in injector performance over time.
Draper says Delphi has developed a methodology for monitoring and tracking each injector's minimum drive pulse (MDP) by measuring the corresponding drop in rail pressure. The MDP method has proven considerably more precise than traditional crank speed-based monitoring, he explains, since there is no dependency on combustion of the injected fuel for detection.
"The success of this technology proves the enthusiasm of the heavy-duty vehicle manufacturers and operators for a sensible, highly-durable system that can be implemented cost-effectively," comments Draper.
"We have to help our customers produce the vehicles the operators need, and that means clean, economical, robust and affordable."
Author
Brian Tinham
Related Companies
Delphi Diesel Systems
This material is protected by MA Business copyright
See Terms and Conditions.
One-off usage is permitted but bulk copying is not.
For multiple copies
contact the sales team.