Abstract
The present study reports a modular phenomenological model for predicting peak pressure in vented explosions. Modelling assumptions are explained in detail and model components are validated against experimental and computational results. A basic version of this model is reported in our earlier paper (Sinha et al., 2019). Previous experimental and modelling efforts on vented explosion have primarily focussed on idealized condition of empty container with uniformly mixed fuel. However, in real accidents, there are often obstacles in flame path, and a leaked fuel may not get enough time to mix uniformly. These realistic accidental scenarios are accounted for in this extended model. First the model components are assessed using available experimental results. Comparison of flame arrival time and flame propagation inside the enclosure are made, which demonstrate the ability of the model to capture flame propagation accurately. Suggestions are also made for vent panel installation to reduce peak overpressure in accidental explosions.
Predictions for external cloud radius and pressure generated by external explosion are found to be in close agreement with the experimentally measured values. The model is further simplified, and a final equation is proposed which depends on two fuel related parameters and two geometric parameters. Fuel dependent parameters are pre-tabulated, and geometric parameters are easy to compute. Procedure to calculate pressure generated by external explosion and internal pressure are outlined in detail. Experimental results available in literature are used to evaluate model predictive capabilities. The model, in principle should be applicable for any gaseous fuel. However, the focus of the present investigation is to assess it for hydrogen explosions. Experimental repeatability is also discussed, and role of wall deflection is highlighted.
In parallel to the modelling effort, a dedicated in-house CFD solver HyFOAM is developed utilizing OpenFOAM platform. The HyFOAM predictions are validated against experimental results from the recently published test data involving hydrogen explosion in a 20-foot ISO container (Skjold et al., 2017, 2018, 2019). Moreover, as experimental investigations are expensive and require significant testing and safety infrastructure, a limited number of scenarios can be tested experimentally. In addition to the experimental results, few more cases are simulated using HyFOAM. Phenomenological model results are compared with the CFD results, and a reasonably good match is observed.