INJECTION SYSTEMS
REQUIREMENTS
Outlook for electrostatic atomization in
automotive applications
Rodica A. Baranescu
Traditional requirements
• Accurate fuel metering per cycle for load control
• Provide vaporization and distribution in combustion space
• Provide the mixture in correct proportion under all conditions
(start/acceleration/full power)
• Protect sensible components in the injector from damage by
deposits in the fuel or by debris
Drivers for Fuel Injection
Revolution
• Stringent emission standards for NOx and particulates,
•
•
•
•
requiring combustion control
– Euro V; US 2007; US 2010
Fuel consumption and GHG reduction pressure
More stringent “sociability” requirements for CI engines
– driving fun: acceleration, low end torque
– improved comfort: low noise, easy start
Competition with SI and hybrids (for CI engines)
Fuel injection progress seen in both SI and CI engines
Advanced Requirements for Injection
• Increase of operating pressure
• Injection rate control and flexibility
• Multiple injections per cycle (of determined
•
duration and quantity)
Electronic control and management of injection
process
Dimensions of Modern Injection Technology
Challenges for injection systems
• Reduce injector deposits
•
•
•
•
•
•
•
– High temperature 1200C; 2000 bars; small clearances
Reduce oxidation due to heat entrainment in fuel system
Improve fuel quality worldwide to provide robustness to modern
fuel systems
Develop new additive technology for increased detergency
Deal with new fuels (biodiesel) and its poor oxidation stability
Develop new materials and technology for injectors
Develop new software for injection management
Strive for global fuel specifications matched to requirements
Injection Rate Flexibility
•
•
•
•
Provides:
combustion control
Rate of pressure rise
Noise
NOx formation
Development Targets for Injection Systems
•
•
•
•
Improved nozzle design (including orifices)
Enhanced metering accuracy
Increased injection pressure
Multi injection capability (for combustion control
in CI engines)
Gasoline Manifold Injection (external)
Gasoline Direct Injection (internal)
Gasoline Injection
Common Rail Fuel Injection System
from Delphi Common Rail System with Direct Acting Injector, MTZ 10/2008, Volume 69
Common Rail Fuel Injection System
from “2000 bar Diesel Common Rail by Bosch for Passenger Cars” , MTZ 10/2008, Volume 69
Common Rail System Features
•
•
•
•
•
High pressure - independent of injection cycle and engine speed
Constant high pressure during injection
Allows more than one injection per cycle
Square rate of discharge at full and low load
Penalty in noise and high pressure rise in combustion chamber
Multiple injections patterns
1 pre-injection; 2 main injection; 3 steep rise; 4 boot shape; 5 gradual
rise; 6 gradual drop; 7 steep drop; 8 close secondary; 9 late post-injection
Common Rail Fuel Injection System
from “Delphi Common Rail System with Direct Acting Injector”, MTZ 10/2008, Volume 69
Piezo Electric Injector
•
•
•
•
•
Needle hydraulically actuated by piezo stack
Weight reduced (two fold)
Up to 5 injections (closed coupled) per cycle
Allows precise injections of small quantities (1mm3)
Lower fuel leakage rates ( requires smaller pump)
Conclusions
• Fuel injection system complexity has increased substantially
• Design and packaging is additionally challenging
• Lower pressure injection systems seem more suitable to
electrostatic atomization
• Viscous fuels and liquids and large injection systems seem also
suitable to electrostatic charge
• Approach is interesting and improved atomization is worthwhile;
potential for new hardware designs is significant