Fuel injection technology represents one of the main drivers towards improving current characteristics of diesel engines and identifies future enhancements to reduce engine exhaust emissions, combustion noise and fuel consumption. In parallel to the continuously growing injection pressure, the number of injection events has been increased and the tolerances of the injected quantities has been reduced, a trend that will be followed in the future.

FEV, for over 20 years, has provided piezo-electrically actuated injection systems as development tools for identification of Fuel Injection Equipment (FIE) related demands within advanced combustion development. FEV has also been one of the key developers of modern production piezo injection systems. In addition to typical diesel injection systems, FEV has continued to develop and investigate gasoline tailored injection systems, as well as dedicated injectors for exhaust aftertreatment devices or fuel cell systems.

Injection System Development

CORA RS is one significant example of FEV’s prototype injectors for combustion system

development. CORA RS uses a conventional spring loaded nozzle needle, which allows a much higher opening and closing velocity of the nozzle than current production common-rail systems. The higher velocities are possible because the rear side of the nozzle is not pressurized by the rail pressure.

The CORA RS injector also combines the common-rail system’s degree of freedom regarding injection pressure and multiple injection capability with the flexible forming of the injection rate and minimized nozzle seat throttling.

Production System Investigation

Standard production engine development projects are supported by dedicated fuel injection system investigations, in addition to the innovative research work that is performed on unique prototype injection systems.

Using computerized injection test benches, the performance of the injection system is automatically measured and documented through the following methods:

• Injected quantity vs. Energizing duration
• Standard deviation of injected quantities
• Influence of the intervals between pilot, main and post injection
• Injector stability (aging and coking)
• Full system durability investigations

Special Sensors for Fuel Injection System Analysis

The size, dynamic and environmental boundary conditions of fuel injection systems often require the application of specially developed sensors, because these sensors are not commercially available. The retroaction of these sensors on the injection performance has to be reduced as far as possible. Some examples of special sensors that have been developed:

• Nozzle needle and/or valve lift sensors
• Pressure measurement in a servo control chamber or at the nozzle side
• Dynamic pump drive torque and/or power consumption
• Temperature measurement
• Actuator force measurement