Simultaneous shadowgraph/mie scattering imaging of liqid and vapor phases of diesel sprays and validation of a numerical model

Diesel sprays from an axially-disposed single-hole injector are studied under both non-vaporizing and vaporizing conditions in a constant-volume vessel. A hybrid shadowgraph/Mie scattering imaging set-up is used to acquire the liquid and vapor phases of the fuel distribution in a near-simultaneous visualization mode by a high-speed camera (40,000 fps). A diesel injector with k0 factor is used, having the exit-hole diameter of 0.1 mm and the ratio L/d =10. The studies are performed at the injection pressures of 70, 120, and 180 MPa, 25.37 kg/m3 ambient gas density, at the environment temperature of 373, 453 and 900 K. The instantaneous tip penetration of the liquid and vapor phases is extracted from the collected images and processed by a properly assessed software, under the various operating conditions. The AVL FIRE(TM) code is also used to simulate the spray dynamics. The model is validated on the ground of the collected experimental data. The results dependence upon the cell size of the computational mesh is preliminary discussed. Particular care is devoted to simulate the vaporizing conditions, where the performed combustion of an Acetylene/hydrogen mixture is properly simulated to well define not only the conditions of pressure and temperature within the vessel at the time of injection, but also the turbulent kinetic energy and dissipation rate, that allow correctly evaluating the relevant transport properties of mass, momentum and heat under turbulent flow conditions.