Delphi Automotive has developed a common rail fuel system technology for heavy-duty diesel engines that combines proven hardware with an innovative architecture, allowing vehicle manufacturers to meet Euro VI emissions standards without significant modification to their base engines.
Delphi presented the work in a technical paper “Development of High-Pressure Common Rail Systems Incorporating Advanced Electronic Control Strategies for Future Heavy-Duty Vehicles,” at the 33rd Vienna Motor Symposium last week. At the same event, Delphi also revealed a new common rail system for small, one- to four-cylinder diesel engines, including non-automotive applications. This concept system is expected to be ideal for heavily downsized applications and developing markets.
A combination of injector design, configurable pump layout and advanced air and fuel control strategies has provided a highly-flexible, modular solution for engines between 7- and 16-liters displacement.
Delphi’s new heavy-duty common rail system will be available in three configurations: two Distributed Pump Common Rail Systems (DPCRS), in which the pressure is provided by a number of separate pumping units; and a Remote Pump Common Rail System (RPCRS), which is similar to traditional common rail layouts. Running initially at 2700 bar injection pressure, the technology is capable of operating at up to 3000 bar with at least 5 injections per cycle to meet the requirements of future legislation that might limit the permissible CO2 emissions from heavy commercial vehicles.
Delphi has been working on the Euro VI systems since 2005.
DPCRS technology is suited for engines currently using Electronic Unit Injector (EUI) systems or Electronic Unit Pump (EUP) systems because the installation envelope is the same as that for Delphi’s current products. The ultra-high rail pressure is provided by a flexible number of 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.
For the first time in the Heavy-Duty Diesel market, a latching outlet metering valve (OMV) is used on each of the pumping elements. Digital control of the pumping elements by their individual OMVs produces a very rapid transient response, typically 0.2s for a 2000 bar increase, while also providing selectable displacement functionality.
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 levels, Delphi says. Engine tests have demonstrated a 50% smoke reduction combined with engine-out NOx levels less than 2 g/kWh. Evolutions of the same technology will allow a cost-effective path to next-generation emissions compliance.
The key challenge for the Euro VI injectors is ensuring exceptional fueling accuracy at very high pressures, with no significant change over the lifetime of the system. Our new system has been proven to comfortably meet our service life target of 1.6 million km [994,000 miles]. —David Draper, engineering director, Delphi Heavy-Duty Diesel Systems and co-author
Delphi’s new Euro VI and US13 ECU (Electronic Truck Controller: ETC3) common-rail control system is an evolution of the proven Euro V and US10 engine and vehicle controller, capable of supporting 12V and 24V applications with the same hardware platform. ETC3 features a 32-bit processor with floating-point capability and can be operated in an environment of up to 105 °C without cooling, improving packaging and avoiding the additional cost and complexity of a fuel cooling circuit.
Software development for Euro VI has been driven by requirements to compensate for potential variation in engine performance and emissions, such as variations in injector performance over time. 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, since there is no dependency on combustion of the injected fuel for detection.
Delphi also showcased its light-weight new Unit Pump Common Rail (UPCR) system, a cost-effective concept specifically designed for diesel engines with one to four cylinders. Ideal for small-engine vehicles including non-automotive applications such as small agricultural and industrial machines, the technology provides a low-cost alternative to the high-pressure pump normally used on common rail systems.
Currently in production, the system operates at 1600 bar. Its key features include fast solenoid diesel injectors, a program-tailored engine control module (ECM), a low-cost fuel filter and a unit fuel pump with an inlet metering valve (IMV) to improve fuel economy. The UPCR system is expected to provide a high-value approach to meet the future requirements of Euro 7 regulations, due to a 2000 bar version that is under development.