Experimental study of hydrogen jet dynamics : Investigating free momentum and impingement phenomena

There is a growing interest in the utilization of hydrogen (H₂), as a zero-carbon fuel, in internal combustion engines (ICEs). Accordingly, the primary focus of this study is to investigate low-pressure H₂ jet dynamics, which play a vital role in air-fuel mixing especially in direct injection (DI) engines. High-speed z-type schlieren imaging is employed in a constant volume chamber to study the effect of nozzle geometry (single-hole, double-hole, and multi-hole), pressure ratios (PR = injection pressure (P_i)/chamber pressure (P_ch)), injection angle (10°, 15°, and 20°), and injection duration (ID) on the H₂ jet characteristics. Image post-processing is executed in MATLAB and Python to extract the H₂ jet characteristics, including penetration and cross-sectional area. The novelty stems from the comprehensive investigation of H₂ jet dynamics and impingement phenomenon under various engine-like conditions. The results indicate that apart from the fact that higher pressure ratios (PRs) improve the air-fuel mixing, the single-hole nozzle induces the fastest H₂ jet penetration and the smallest cross-sectional area. Conversely, the double-hole nozzle leads to the slowest penetration and the most expansive cross-sectional area. The performance of the multi-hole nozzle falls between that of the single-hole and double-hole nozzles. Additionally, changing the injection angle results in jet-piston impingement at the periphery, leading to higher H₂ concentration in those areas. This negatively affects the formation of an optimal air-fuel mixture. It is also found that changing the injection duration (ID) has no noticeable impact on the H₂ jet's behavior.