Ultrafast and quantitative X-tomography and simulation of hollow-cone gasoline direct-injection sprays

Gasoline direct injection (GDI) has the potential to greatly improve internal combustion engine performance through precise control of the injection rate, timing, and combustion of the fuel. A thorough characterization of the hydrodynamics of fuel injection has to come from a precise, quantitative analysis of the sprays, especially in the near-nozzle region. A lack of knowledge of the fuel-spray dynamics has severely limited computational modeling of the sprays and design of improved injection systems. Previously, the structure and dynamics of highly transient fuel sprays have never been visualized or reconstructed in three dimensions (3D) due to numerous technical difficulties. By using an ultrafast x-ray detector and intense monochromatic x-ray beams from synchrotron radiation, the fine structures and dynamics of 1-ms GDI fuel sprays from an outwardly opening nozzle were elucidated by a newly developed, ultrafast, microsecond computed microtomography (CT) technique. In a time-resolved manner, many detailed features associated with the transient fuel flows are readily observable in the quantitatively reconstructed 3D fuel spray density distribution as a result of the quantitative CT technique. More importantly, a computational fluid dynamics (CFD) simulation based on the Taylor analogy breakup (TAB) model has also been performed using the boundary and initial conditions obtained from the experiment data. The experimental and numerical results are in good agreement quantitatively. These results not only reveal the characteristics of the GDI fuel sprays with unprecedented detail, but will also facilitate realistic computational fluid dynamic simulations in highly transient, multiphase systems.