Behavior of hydrogen hollow-cone spray depending on the ambient pressure

Abstract

Hydrogen as a fuel is feasible for future sustainable mobility. Because hydrogen has a low-volumetric energy density, high-pressure hydrogen is required for high-speed fuel injection. The objective of this research is analysis of the hydrogen spray behavior depending on the ambient pressure. A high-pressure (10 MPa) hydrogen spray is visualized in a constant volume combustion chamber in which the ambient pressure and injection duration are varied. The schlieren method is utilized to capture the hydrogen spray with a high-speed camera. The characteristics of the hydrogen hollow-cone spray are investigated using high-speed spray images. High ambient pressure decreases the vertical extent of the spray penetration and its area. The centroid of the spray is contracted toward the axis of the injector until the ambient pressure reaches 2.0 MPa, and the pressure difference between the inner and outer sections of the spray is larger for high ambient pressures. At high ambient pressure, the heterogeneity of the hydrogen mixture increases. Owing to the aerodynamic effect, the contracted spray reconstructs the main hydrogen plume at the center of the injector. Moreover, hydrogen travels toward the top of the injector because of the generation of a vortex at the inner side of the spray. Based on the findings, hydrogen direct injection can contribute to sustainable mobility in the future.