A parametric study of autoigniting hydrogen jets under compression-ignition engine conditions

• Published in: International journal of hydrogen energy 2022-06, Vol.47 (49), p.21307-21322
• Main Authors: Yip, Ho Lung, Srna, Aleš, Wehrfritz, Armin, Kook, Sanghoon, Hawkes, Evatt R., Chan, Qing Nian
• Format: Article
• Language: English
• Subjects: Flame evolution; H2 autoignition; H2 direct injection; High-pressure H2 jet
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2022.04.253

This study examines the flame evolution of autoigniting H2 jets with high-speed schlieren and OH∗ chemiluminescence optical methods in a constant-volume combustion chamber over a wide range of simulated compression-ignition engine conditions. Parametric variations include the injector nozzle orifice diameter (0.31–0.83 mm), injection reservoir pressure (100–200 bar), ambient temperature (1000–1140 K), density (12.5–24 kg/m3) and O2 concentration (10–21 vol.%). The jet ignition delay was found to be highly sensitive to changes in ambient temperature while all other parameter variations resulted in minor ignition delay changes. Optical imaging reveals that in most cases, the reaction front of the H2 jet initiates from a localised kernel, before engulfing the entire jet volume downstream and recessing towards the nozzle. The flames attach to the nozzle, except at the lowest ambient oxygen condition of 10 vol.% O2 for which a lifted flame is observed. The H2 diffusion flame length shows a dependence on both the mass flow rate and the level of O2 entrainment that follows the same correlations as previously established for atmospheric H2 jet flames. •Parametric study of H2 jet autoignition in high-pressure high-temperature environment with optical investigation.•H2 jet autoignition is mainly sensitive to ambient temperature variation.•Localised combustion kernel initiates and spreads to engulf entire jet volume.•Very short lift-off length (1–3 nozzle diameter) at quasi-steady flame, except at low ambient O2 concentration.•H2 diffusion flame length is sensitive to parametric changes that affect higher mass flow rate and O2 entrainment.