| Delphi has developed a gasoline
direct injection (GDI) system and a “direct-acting” piezo
diesel injector.
The group believes that tightening emissions and CO2 legislation will
force OEMs to look more closely at powertrain strategies for 2012 and
beyond.
Delphi’s advanced diesel engineering chief, Stefan Zülch said:
“NOx, not CO2, is the challenge for diesel. Fuel consumption improvements
will drive developments in gasoline.”
Competitors such as Bosch and Siemens have established products on the
market. The actuators contain a ceramic element that reacts quickly to
an electrical charge, either moving or changing shape. Faster than solenoid
valves because it doesn’t have the inertia of a coil, it gives engineers
more precise control of injection events.
Delphi’s lack of piezo has kept it out of the growing GDI market.
The firm is compensating for this by using a “multicharge”
ignition system. The result is a GDI with 90 per cent of the ability and
50 per cent of the cost of a piezo system.
Gasoline engineering director Dr Sebastian Schilling said: “Delphi’s
solution for EuroV gasoline is stratified GDI at 200 bar with multicharge
ignition and NOx aftertreatment.”
The system creates stable, linear flow rates but ignition can only occur
directly in front of the injector. To address this, Delphi developed a
small spool 30mJ ignition system – 80mJ is usual – with a
charging time of just 15 microseconds. “More sparks means you don’t
make mistakes – if the first fails, the second gets it,” said
Schilling.
The system comes into play mainly at lower engine speeds and can also
decrease cold start emissions.
The GDI system has no customers yet, but Delphi will start series production
next year of its direct-acting diesel injector. It claims its piezo system
is three times faster than competitors’ servo-piezo injectors.
Current servo piezo systems require a 140V piezo actuator; the injector
opens when a long needle retracts. Delphi’s system requires a 12V
piezo actuator, reducing cost. The system’s magnetic valve requires
little effort and uses a shorter needle to open the injector.
Zülch said: “Our piezo actuator moves the needle directly –
there’s no high pressure chamber. It achieves speeds of 3m/s instead
of 1m/s.”
This makes it easier to optimise NOx emissions and noise. Delphi said
the injector can improve fuel consumption by up to five per cent and NOx
by 20 to 30 per cent, compared to competitors’ piezo injectors.
The injector still has a small motion amplifier between the piezo actuator
and the needle, but removing the control chamber also dispenses with its
leaks and fuel economy penalty.
Zülch said: “This is a high-end concept for heavy vehicles.
It won’t replace solenoid technology.” |
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