PIV-LIF study of different hydrogen injectors for mixture preparation comparison

Green hydrogen is increasingly considered as a promising solution for reducing greenhouse gas emissions in the transport sector. Among the different hydrogen-powered technologies, hydrogen internal combustion engines offer a rapid pathway toward the decarbonization of heavy-duty and off-road applications. However, their performance and pollutant emissions strongly depend on mixture preparation during the injection process. Owing to the low density and high diffusivity of hydrogen, understanding the interaction between the fuel jet and the surrounding airflow is essential for optimizing injector design and operating conditions. In this study, the development of hydrogen jets issued from three medium-pressure injectors is investigated in a constant-flow chamber. Simultaneous Laser-Induced Fluorescence (LIF) and Particle Image Velocimetry (PIV) measurements are employed to characterize both the concentration field and the surrounding flow structures. The combined diagnostics provide detailed information on jet penetration, air entrainment mechanisms, vortex formation, and the resulting mixture distribution. The results highlight significant differences in the flow dynamics generated by the investigated injector geometries. The single-hole injector produces a highly penetrating jet that preserves a coherent core over a longer distance, leading to deeper fuel transport into the chamber. In contrast, outward-opening injectors generate stronger shear-layer instabilities and vortical structures in the vicinity of the jet. These flow structures enhance air entrainment and promote the deformation of the fuel-air interface, accelerating the mixing process. The simultaneous LIF-PIV measurements reveal a clear relationship between vortex dynamics and mixture homogenization. These findings provide valuable insights into the influence of injector design on hydrogen mixture preparation.