Flow in injection systems

Department Fluid Systems

The problem of fuel injection has always been in the centre of new technological developments. The technical and economical requirements include decreasing formation of pollutants in emission and economical consumption with optimal reliability and performance. A great progress in this area has been obtained by the introduction of the Common-Rail-Systems and pump-injectors in the past two decades. Both methods use the advantages of high injection pressure. Parallel to further developments of efficient and conventional injection methods the new injection strategies are development.
One possible approach to solve this problem is the optimization of injection strategy by employment of Laval or coaxial nozzles (one example of Laval nozzle is shown in Fig. 1). The atomization process in such nozzles occurs by fragmentation between high velocity gas jet and fuel volume.


Fig. 1: Scetch of Laval nozzle

In order to answer industrial problems in the field of Multi-Phase Flow commercial methods of Computational Fluid Dynamics (CFD) are employed and supplemented. In the case of unsteady atomization process of liquid fuel in Diesel engine a numerical approach for the prediction of unsteady behavior of cavitation was developed. The dependences between the transient nozzle flow and spray formation are analyzed. The calculations for different types of nozzle configurations were carried out.
Lavaldüse - Kavitation

Fig. 2: Extension of cavitation within the nozzle and the associated spray formation


Dr.-Ing.habil. Mykhailo Konstantynov
German Aerospace Center

Institute of Aerodynamics and Flow Technology
, Fluid Systems
Tel: +49 551 709-2876

Fax: +49 551 709-2241

E-Mail: Mikhail.Konstantinov@dlr.de
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