Siemens' Next Generation Common Rail System To Incorporate Modular Design, Advanced Valving Technology
12 January 1998
Siemens' Next Generation Common Rail System To Incorporate Modular Design, Advanced Valving Technology
Piezohydraulic Technology Expected to
Further Reduce Diesel NOx Emissions; Improve NVH Performance
AUBURN HILLS, Mich., Jan. 12 -- Siemens Automotive is
developing a second generation common rail system for high-pressure diesel
fuel injection -- a technology aimed at further reducing the nitrous oxide
(NOx) emissions and noisy operation of diesel engines.
Common rail (CR) fuel injection is the latest breakthrough in diesel
engine technology. High-pressure fuel injection resulting from CR technology
is a key to better diesel spray atomization, improved fuel/air mixing and more
efficient combustion of fuel in the engine cylinder.
Siemens' next generation CR system -- now under development at the
company's Regensburg, Germany automotive engineering operation -- will use a
modular design and incorporate piezohydraulic valve technology to precisely
regulate the high-pressure injection of diesel fuel into the engine cylinder.
The system's modular design will combine the rail, valves, fuel injectors,
sensors and actuators into a single, easy-to-apply package that will provide
design flexibility and cost savings.
"We're now working at full capacity to make modular common rail technology
applicable for volume production," said Dr. Klaus Egger, Siemens project
leader for diesel systems.
"Compared to conventional fuel injection systems, the common rail system
offers greater design flexibility, and considerable cost advantages resulting
from easier integration in the engine compartment," added Egger.
The use of the piezohydraulic valves marks the next generation in CR
technology -- they are expected to improve high-speed fuel injection over the
solenoid valves used on current CR systems.
According to Siemens' engineers, piezohydraulic valves react up to four
times faster than the solenoids currently used, bringing more exact fuel
quantity injection and more precise injection timing.
Piezohydraulic valves react to voltage pulses (sent from an engine
management system) within 0.1 milliseconds. At the heart of the injector is a
ceramic-based piezoactuator that expands on application of an electric charge.
"The piezohydraialic valve technology will lead to extremely precise control
of injection rates," said Dr. Egger.
"As a result, diesel fuel combustion is almost as quiet as in a gasoline
engine, the diesel powertrain gains more pulling power at the lower end of the
speed range, and the efficiency advantages of the diesel remain unchanged."
"Hydrocarbon, NOx, and particulate emissions are reduced using existing CR
technology -- and the next generation of piezohydraulic valves are expected to
help reduce these diesel emissions even further," Egger said.
"The new valve technology improves the preciseness of pilot injection (the
spray that initiates combustion and precedes the main spray), main fuel
injection, and various injection pressures used up to 1500 bar," Egger
explained.
"Noise and vibration harshness will be improved due to enhanced electronic
control of individual injections -- especially at low loads and speeds."
Fuel injected diesel engines are considered to be the most fuel and heat
efficient of the internal combustion engines, however NOx and particulate
emissions along with poor noise performance have been the powerplant's biggest
drawbacks.
For more information on Siemens solutions for improved vehicle emissions
and fuel economy, please visit us on the internet at http://www.siemensauto.com.
SOURCE Siemens Automotive
