Influence of the nozzle geometry of a diesel single-hole injector on liquid and vapor phase distributions at engine-like conditions

The paper describes an experimental activity on the spatial and temporal liquid- and vapor-phase distributions of diesel fuel at engine-like conditions. The influence of the k-factor (0 and 1.5) of a single-hole axial-disposed injector (0.100 mm diameter and 10 L/d ratio) has been studied by spraying fuel in an optically-accessible constant-volume combustion vessel. A high-speed imaging system, capable of acquiring Mie-scattering and Schlieren images in a near simultaneous fashion mode along the same line of sight, has been developed at the Michigan Technological University using a high-speed camera and a pulsed-wave LED system. The time resolved pair of schlieren and Mie-scattering images identifies the instantaneous position of both the vapor and liquid phases of the fuel spray, respectively. The studies have been performed at three injection pressures (70, 120 and 180 MPa), 23.9 kg/m3 ambient gas density and 900 K gas temperature in the vessel. A pre-combustion of reactants filling the vessel generated the required high-temperature and high-pressure conditions typical of diesel engine at the injection time. This pre-combustion mixture consists of C2H2, H2, O2 and N2 gases in order to obtain inert conditions (0% O2). The results obtained in the non-vaporizing conditions have been compared with those obtained on a different facility at Istituto Motori. In this paper the influence of the k-factor on the measurements of liquid and vapor penetration will be presented with the comparison of liquid penetration obtained by both the acquisition techniques and the two facilities. Then the liquid and vapor mass fraction has been estimated for several experimental conditions. Finally, fuel injection rates determinations using a meter working on the Bosch tube principle have been carried out to measure the injected mass