Experimental Characterization of the Geometrical Shape of ks-hole and Comparison of its Fluid Dynamic Performance Respect to Cylindrical and k-hole Layouts

摘要

Diesel engine performances are strictly correlated to the fluid dynamic characteristics of the injection system. Actual Diesel engines employ injector characterized by micro-orifices operating at injection pressure till 20MPa. These main injection characteristics resulted in the critical relation between engine performance and injector hole shape. In the present study, the authors' attention was focused on the hole geometry influence on the main injector fluid dynamic characteristics. At this purpose, three different nozzle hole shapes were considered: cylindrical, k, and ks nozzle shapes. Because of the lack of information available about ks-hole real geometry, firstly it was completely characterized by the combined use of two non-destructive techniques. Secondly, all the three nozzle layouts were characterized from the fluid dynamic point of view by a fully transient CFD multiphase simulation methodology previously validated by the authors against experimental results. The experimental characterization of the ks-hole geometry was a mandatory task to assure a good numerical simulation accuracy. From the fluid dynamic point of view, the three nozzle layouts were compared by the average fluid dynamic conditions recorded on the nozzle hole outlet sections and by the cavitating flow evolution inside the injector hole themselves.