Delphi chooses common rail for future heavy diesel injection systems

  • 27-Oct-2008 09:26 EDT
Hanover show 2008 - 23.jpg

Delphi’s new heavy-duty common-rail system, with engine-oil-lubricated cam and plunger pump, should be in production in 2012. (John Kendall)

Delphi revealed its medium- and heavy-duty diesel fuel injection systems, designed to meet the needs of engine manufacturers for Euro 6, U.S. EPA 2010, Japan PNLTR, and future emissions requirements, at the recent IAA Commercial Vehicles show in Hannover, Germany. The new systems signal a change in strategy for the company, which relies on rate-shaping unit pump and injector technology for its current systems. Delphi will switch to common rail for future needs; the technology is better suited to the multiple injection pulses required to meet tightening emissions limits.

Three system architectures will be offered, enabling Delphi to provide a system for a wide variety of engine designs. There is a “conventional” common-rail system with rail pressure provided by a cam and plunger pump lubricated with engine oil. The system architecture draws on Delphi’s common-rail expertise gained from lighter-duty diesel systems.

The company will provide two other systems, which it describes as “distributed pump common rail.” Both draw on the company’s current electronic unit pump (EUP) and electronic unit injector (EUI) technologies. Delphi has developed EUP systems for cam-in-block engines, with a cam-actuated pump body mounted on the engine block, connected to the injector via a high-pressure pipe. The system shares the same fundamental components as the E3 EUI combined pump and injector designed for cam-in-head engines.

What Delphi has done for the common-rail systems is to adapt the EUP and EUI systems so that the pump elements feed a high-pressure common rail at pressures of 2400, 2500, 2700, or 3000 bar (34.8, 36.3, 39.2, or 43.5 ksi), as required.

For both variants of the system, up to one pump per cylinder can be used to charge the rail, depending on engine capacity. Delphi will provide two variants of each system: one designed for engines between 4.0- and 9.0-L capacity, and a larger system designed for engines between 9.0- and 16-L capacity. For an engine of 13 L, Delphi expects that a system equipped with three pumps should suffice, while two pumps should be able to handle the needs of smaller engines.

The EUP-derived system is known as F2 P. The three basic elements of the system are the cam-driven pumps, rail, and separate injectors. The EUI-derived system operates differently.

For example, consider a 13-L, six-cylinder engine fitted with three pumps. These would be driven from the overhead cam in the same way as Delphi’s current E3 injector, which can already deliver injection pressures of up to 2500 bar. Like the E3, the pump and injector are housed in the same body. The difference is that the two elements operate independently. The pump feeds pressurized fuel to the rail, which in turn supplies fuel back to the injector. For the three cylinders not fitted with the pump/injector body, a more conventional common-rail injector is used, effectively using the same injectors as the F2 P system. To help supply the fuel at the pressures needed, the camshaft carries two lobes, giving two pump strokes per revolution in place of the single stroke for current EUP and EUI systems. Each pump has a plunger diameter of 7 mm (0.28 in) and stroke of 18 mm (0.71 in).

To achieve the required injection pressures and also satisfy the B10 durability requirements of 1.6 million km (1 million mi), Delphi has had to design the valve hydraulics to reduce stress. This involved work around the geometry of the sealing cones, but no changes to the rail architecture were needed.

Delphi apparently sees the distributed pump systems as a short- to medium-term measure. Richard Green, Sales and Marketing Manager for Delphi Powertrain Systems, told AEI, “Oil lubricated systems are the way forward,” adding "there is no challenge on oil/fuel separation compared with 2500-bar systems.”

To drive the new common-rail systems, Delphi has developed ETC3, a new electronic truck controller. The air-cooled system will manage all engine and duty functions, including cruise control. A fuel-cooled option for extreme environments will also be available. Delphi says that the ETC3 will be ready for 2010 and expects the new heavy-duty common-rail systems to enter production around 2012.

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