CFD modelling of hydrogen safety aspects for a residential refuelling system
thesisposted on 06.07.2017 by Thomas Beard
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
This work concerns the modelling of scenarios for a residential hydrogen refuelling system. Such a system is under construction within the Engineering Safe and Compact Hydrogen Energy Reserves (ESCHER) project. Non-reacting and reacting simulations are compared against experimental data before being applied to a residential garage scenario. The non-reacting simulations utilise natural ventilation, which utilises the natural buoyancy of hydrogen and vent locations to disperse flammable mixtures. This is favoured over mechanical ventilation, which could fail. The non-reacting work focuses on investigating the most suitable venting configuration for a release of hydrogen from a refuelling system located within a residential garage. Different vent configurations are examined initially before proceeding to take into account atmospheric conditions, wind, and the presence of a vehicle for the two best venting configurations. This is to determine the venting configuration that would diminish the accumulation of a flammable mixture, as well as dissipating the mixture quickest after the release has stopped. The modelling strategy utilised for this work is validated against two different sets of experimental data, prior to the investigation into residential garages. The predicted and experimental results show good agreement for the modelling procedure suggested. The reacting investigations are for both premixed and non-premixed combustion. The non-premixed combustion investigates the temperature distributions and as such the possible harm to people for such a scenario, compared against experimental data. The results show some over predictions of the temperatures. The premixed combustion investigates the potential overpressures that may occur if a homogeneous mixture was to form and ignite, within a residential garage. This work is preceded by a validation of the combustion model with the predicted results compared to data from The University of Sydney. The validation results show that the modelling strategy matches the peak overpressures accurately. The non-reacting studies show that having a lower vent opposite the release and an higher vent near the release produces the smallest flammable mixture as well as dissipating the mixture to the external surroundings quickest. The non-premixed reacting work shows good agreement with experimental results. The premixed reacting work shows that the garage would destruct with major consequences to people and surroundings. This work would be applicable to any potential usage of indoor refuelling for hydrogen vehicles, helping to determine a suitable configuration for mitigating hydrogen releases. It should be noted that all such work is geometrically dependent and as such the strategy proposed would be useful for investigating individual scenarios.
- Mechanical, Electrical and Manufacturing Engineering