Cavitation-Suppressing Orifice Design Applied to a Heavy-Duty Diesel Engine Injector Operating With Gasoline

Measurements of fuel injectors via non-destructive X-ray techniques can provide unique insights about an injector’s internal surface. Using real measured geometry rather than nominal design geometry in computational fluid dynamics simulations can improve the accuracy of the numerical models dramatically. Recent work from the authors investigated the influence of the injector design on the internal flow development and occurrence of cavitation in a production multi-hole heavy-duty diesel injector operating with a straight-run gasoline for gasoline compression ignition (GCI) applications. This was achieved by evaluating a series of design parameters which showed that the intensity and duration of cavitation structures could be mitigated by acting on certain injector parameters such as K-factor, orifice inlet ellipticity, and sac-to-orifice radius of curvature. In the present work, the findings from the previous parametric study were combined to generate two attempts at improving the injector design and numerically evaluate their ability to suppress cavitation inside the orifices at three levels of injection pressure (1000, 1500, and 2500 bar), while operating with the same high-volatility gasoline fuel. Qualitative and quantitative analyses showed that, compared to the results obtained with the original X-ray scanned geometry, the improved designs were able to prevent fuel vapor formation at the two lowest injection pressures and avoid super-cavitation at the higher pressure. It was shown that these results were due to the strong influence that the orifice shape can have on the pressure and fuel vapor volume fraction distributions within the orifices. The informed design choices proposed in this study can therefore be vital for extending the durability and reliability of heavy-duty injectors for GCI applications.