An experimental and numerical study on liquid fragmentation induced by an accidental industrial explosion

In a process involving hazardous liquids, if a chemical runaway reaction happens inside a tank, an explosion may occur and spreads the bulk liquid around the exploded vessel. Following the rapid ejection, the liquid will be fragmented into droplets both by the high-speed gas flow and blast propagation. The droplets dimension are directly related to the extent of the dispersion of toxic liquids and/or the combustion risk of a flammable aerosol thus produced. Therefore, it is of crucial relevance to study the phenomena involved in fragmentation, understanding the role played by hydrodynamic instabilities occurring at the liquid-high-pressure gas interface. Moreover, liquid fragmentation is supposed to be strongly dependent on the blast overpressure and the amount of liquid affected by the explosion. The present work analysed these aspects, simulating the impact of an explosion over a liquid layer using the shock tube facility. Firstly, a 1-D numerical model has been implemented to simulate the shock tube problem. Although the presence of viscosity effects was detected, a good match between model and experimental data was found in simulating the closed shock tube. Subsequently, the original shock tube set-up has been appropriately modified to accommodate the liquid on the top. Thus, the different overpressure behaviour in presence of water instead of a closed wall at the end of the tube was investigated. The comparison with the numerical model has allowed appreciating the water layer acts as a solid wall when reflecting the incident shock wave. Direct visualization of the fragmentation phenomenon and the instabilities has been achieved by using high-speed cameras. Several tests have been performed changing the mass of water involved and the pressure impulse impacting it, observing the correlation interacting between these parameters and the liquid acceleration throughout an image processing software.