2488244 Diesel Fuel Injector for Scania DC09/DC13/DC16 Engines

Dynamic cavitation inside a high performance diesel injector – an experimental and CFD investigation （part 4）

In summary: 

High speed imaging of cavitation within a control orifice revealed a pulsing hydraulic effect not seen in previous studies. Large void cavitation was created along the orifice wall and once the conical section was reached, backfilling occurred upstream along the orifice. When the backfilling reached the orifice entrance, there was a flow structure transition, large void cavitation reformed and the process repeated

Advanced turbulence modelling in the CFD simulations produced results that are hugely more accurate than standard models when compared with experimental results. 

The CFD matched the pulsing large void cavitation along the orifice and the back-filling event. 

The frequency of this behaviour on the CFD results also agreed with that of the experiment. 

The CFD revealed that the flow rate was also pulsating, linked with the cavitation behaviour described above. The fact that the average Cd in the CFD agreed with that measured in the experiment gave confidence that the CFD flow rate pulsation was accurate. 

Using LSMs enabled the development of the LES CFD models in a manageable time-frame. This saved considerable time in developing the models for real-size components. 

In the case of the real injector, the frequency of the pulsing cavitation was too high to influence the engine performance. The awareness of the phenomenon provided by this work will enable any potentially adverse effects to be avoided in future design levels.

References
[1]C. Soteriou, M. Smith and R. Andrews, "Cavitation hydraulic flip and atomization in direct injection diesel sprays," in IMechE C465/051/93, 1993.
[2]C. Soteriou, M. Smith and R. Andrews, "Diesel injection - laser light sheet illumination of the development of cavitation in orifices," in IMechE C529/018/98, 1998.
[3]B. Befrui, P. Spiekermann, M. A. Shost and M.-C. Lai, "VoF-LES Studies of GDi Multi-Hole Nozzle Plume Primary Breakup and Comparison with Imaging Data," in ILASS Europe Conference on Liquid Atomization and Spray Systems, Chania, Greece, 2013.
[4]R. E. Bensow, "Simulation of the unsteady cavitation on the Delft Twist11 foil using RANS, DES and LES," in Second International Symposium on Marine Propulsors, Hamburg, Germany, 2011.
[5]C. Egerer, S. Hickel, S. Schmidt and N. Adams, "Analysis of turbulent cavitating flow in a microchannel," in SHF Conference on Hydraulic Machines and Cavitation / Air in Water Pipes, Grenoble, France, 2013.
[6]M. L. Shur, P. R. Spalart, M. K. Strelets and A. K. Travin, "A hybrid RANS-LES approach with delayed-DES and wall-modelled LES capabilities," in International Journal of Heat and Fluid Flow, 2008.
[7] C. Arcoumanis, J. M. Nouri and R. J. Andrews, "Application of Refractive Index Matching to a Diesel Nozzle Internal Flow," in 6th International Symposium on Applications of Laser Techniques to Fluid Mechanics, 1992. [8] D. Bush, C. C. E.Soteriou, M. Winterbourn and C Daveau, "Investigating hydraulic control components in high performance injectors" in Fuel Systems for IC Engines, IMechE 2015.