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

There is a growing interest in the utilization of hydrogen (H 2), as a zero-carbon fuel, in internal combustion engines (ICEs). Accordingly, the primary focus of this study is to investigate low-pressure H 2 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 H 2 jet characteristics. Image post-processing is executed in MATLAB and Python to extract the H 2 jet characteristics, including penetration and cross-sectional area. The novelty stems from the comprehensive investigation of H 2 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 H 2 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 H 2 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 H 2 jet's behavior. [Display omitted] • Double-hole nozzle layout offers jet expansion and enhanced mixing. • Smaller injection angles provide better mixture uniformity. • Pressure ratio significantly influences mixing efficiency. • Injection duration has minor influence on the jet characteristics and mixing. [ABSTRACT FROM AUTHOR]