Study of spray structure from non-flash to flash boiling conditions with space-time tomography

Abstract Flash boiling and plume interaction are common phenomena occurring in gasoline direct injection (GDI) spray at throttling and low load engine conditions. Combined with optical engines and low-pressure vessels, several optical techniques, such as backlight imaging, Mie-scattering, and laser sheet imaging have been employed to study the flash boiling morphology. However, in the 2D images resulting from these techniques (projection views or planar imaging), the 3D information is lost. Those methods are then incapable of providing satisfactory information, especially for the study of multi-plume interaction in flash boiling spray, since multi-plume interaction is not a 2D event. This paper reports the implementation of a 4D tomographic reconstruction method from multi-view diffused back illumination (DBI) images, used for the first time in spray characterization. This cost-effective and time-saving method with a simple experimental setup clarifies the 3D spray structure and fuel trajectory change from non-flashing conditions to flare flash conditions, and quantifies the 3D characteristics of individual plumes in non-flash conditions.