Unraveling the influence of turbulence on hydrogen explosion dynamics: a comparative study of nozzle-induced turbulence in 20-l and 250-l spherical chambers

Hydrogen has already gained importance as a sustainable fuel because of its high energy content and zero carbon emissions. However, its high flammability and low ignition energy make it a serious explosion risk, especially in turbulent and enclosed conditions. This thesis looks at how pre-ignition turbulence affects hydrogen-air explosion dynamics using different nozzle dispersion methods in two spherical chambers: 20-L and 250-L. Experiments were carried out at various turbulence levels (5, 10, and 20 barg) and with different nozzle types (rebound, perforated annular, mushroom, and mushroom cup), focusing on key explosion parameters like maximum pressure (Pmax) and pressure rise rate ((dP/dt)max). Results show that turbulence has a strong effect on the pressure rise rate, especially near stoichiometric hydrogen concentrations, while the effect on Pmax is smaller and depends on the concentration. The shape of the nozzle and the dispersion pressure had a big impact on how well the mixture was distributed and how the flame spread, especially near the lower and upper explosion limits. The rebound nozzle created the strongest turbulence and combustion intensity but showed issues with ignition at low hydrogen levels. In contrast, the mushroom cup nozzle worked better at lower concentrations thanks to its gentler and symmetrical flow. The larger 250-L experiments confirmed that turbulence still affects explosion behavior at scale. Overall, the results highlight the importance of controlling turbulence in hydrogen systems and the need for updated standards when testing hybrid mixtures of gas and dust.