CFD modelling of hydrogen and hydrogen-methane explosions-Analysis of varying concentration and reduced oxygen atmospheres

This paper evaluates the predictive capabilities of the advanced consequence model FLACS-CFD for deflagrations involving hydrogen. Two modelling approaches are presented: the extensively validated model system originally developed for hydrocarbons included in FLACS-CFD 22.1 and a Markstein number dependent model imple-mented in the in-house version FLACS-CFD 22.1 IH. The ability of the models to predict the overpressure and the flame arrival time for scenarios with different concentrations of hydrogen, and thus different Lewis and Markstein numbers, is assessed. Furthermore, the effect of adding methane or nitrogen on overpressure for different regimes of premixed combustion are investigated. The validation dataset includes deflagrations in the open or in congested open areas and vented deflagrations in empty or congested enclosures. The overpressure predictions by FLACS-CFD 22.1 IH are found to be more accurate than those obtained with FLACS-CFD 22.1 for scenarios with varying hydrogen concentrations and/or added nitrogen or methane in the mixture. The pre-dictions by FLACS-CFD 22.1 IH for lean hydrogen mixtures are within a factor of 2 of the values observed in the experiments. Further development of the model is needed for more accurate prediction of deflagrations involving rich hydrogen mixtures as well as scenarios with other fuels and/or conditions where the initial pressure or temperature deviate significantly from ambient conditions.

Automated summary

This study evaluates the predictive capabilities of the advanced consequence model FLACS-CFD for deflagrations involving hydrogen. Two modelling approaches were presented: the extensively validated model system originally developed for hydrocarbons and a Markstein number dependent model. The models' ability to predict overpressure and flame arrival time for scenarios with different hydrogen concentrations was assessed. The study found that FLACS-CFD 22.1 IH provided more accurate overpressure predictions than FLACS-CFD 22.1, especially for scenarios with varying hydrogen concentrations and/or added nitrogen or methane. However, further development of the model is needed for more accurate predictions involving rich hydrogen mixtures or scenarios with significant deviations from ambient conditions.