Realizing Robust Combustion with High Response Diesel Injector with Controlled Diffusive Spray Nozzle and Closed Loop Injection Control

The Diesel engine performance was drastically improved since the introduction of the Common Rail system in 1996. Over the years, the Common Rail technology was continuously improved to reduce the fuel consumption, engine-out emissions and enhance the drivability. However further technical improvement steps for a precise control of combustion are required to satisfy the increasing stringent worldwide emissions limits and to contribute to attractively performing Diesel powered vehicles. Common Rail injectors significantly contribute to improve the combustion. This improvement can be achieved by precisely controlling the injected fuel quantity and increasing the injection pressure. In addition to those features, a more rectangular injection rate, the capability of stable multiple injections at shorter intervals and the control of the spray shape, are required to achieve an optimized fuel mixture. Furthermore, the various fuel qualities world-wide must be considered when attempting to achieve an optimized injection and combustion. This paper reports the following two innovative injector technologies to realize the objectives mentioned above.

1. 1
   The combustion is improved thanks to the 4th generation Piezo injector (G4P) and a new nozzle design that includes a special hole shape denoted as CDS (Controlled Diffusive Spray). The presented benefits include the reduction of wall heat loss, which in-turn increases the combustion efficiency.
2. 2
   By a Closed loop control the accuracy of the injection quantity is improved to achieve a robust combustion. The approach is based on a pressure sensor built-in to the injector by which the actual injection rate and fuel properties are detected.

Both technologies are key features for the advanced engine performance and improved combustion robustness for a world-wide fuel usage that includes variability in the fuel properties.