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Explosion Mitigation Using Water Curtains

I developed and validated a CFD model to capture air-entrainment caused by water spray curtains and study their effect on the dispersion of heavy gases. The purpose of this model was to assist with the design of fire and explosion mitigation systems for gas and chemical processing plants.

This work was presented at the Mary Kay O'Connor Symposium for Process Safety in 2014.

Contributions

  • Research
  • Simulation
  • Analysis

Collaborators

  • Bharat Tulsyan

See Presentation

Motivation

The release of dense gases presents a high risk of fire and explosion because they spread on the ground where they are less affected by dispersion by winds. The Buncefield Vapour Explosion of 2005, considered to be the largest explosion in Europe since the end World War II (BBC), was caused by the spread of such a gas-cloud to a diameter of ~360 m (COMAH, UK).

Deluge or water curtain systems have been proposed as an effective means for entraining air and causing forced mechanical dispersion of the gas-cloud.

Methods

We analyzed how effectively Eulerian-Lagrangian Multiphase CFD could predict the dilution capability of water curtains and compared it to experimental results. The gas mixture and air was represented by the Eulerian phase, while the water droplets were represented by the Lagrangian Phase.

The CFD model was developed using CD-Adapco's Starm CCM+. The geometry of the experimental set-up used by Hald (2005) was replicated. For each simulation, the ratio of the momentum between the water flow from the spray curtain to the momentum of the gas cloud (RM) was varied. The ratio of the average gas-cloud concentration before and after the spray-curtain, known as the dilution factor (FD), was measured.

Results

CFD was found to over-predict the dilution factor (FD) but captured the relationship with the momentum ratio (RM) well. More importantly, the transition in the behaviour from low RM to high RM (at RM = ~3) was also captured by the model.

A visual comparison of the CFD results to Hald's experiment also indicated good agreement between the modelled and actual interaction between the gas cloud and the water spray curtain.