RR1111 - CFD modelling of oil mists for area classification

Many types of industrial equipment can potentially produce an explosive oil mist if a fault develops. However, information on the conditions in which a mist can be ignited and continue to burn is limited. To help address this, HSE and 14 industry sponsors co-funded a Joint Industry Project (JIP) on oil mist formation and ignition.

This report, produced for the JIP, describes the assessment of Computational Fluid Dynamics (CFD) for modelling the oil mist clouds produced by small leaks in pressurised systems.

Some of the JIP experimental tests were modelled using CFD with a range of different droplet sub-models. For those experiments with good atomisation, where the mist was easy to ignite, CFD predicted the observed droplet size and concentrations well using a particular sub-model. The results using this sub-model broadly matched existing industry guidance on oil mist explosion hazards.

Other JIP experiments showed that some leaks produced sprays that were not fully atomised. Many of these could not be ignited easily. The CFD model over-predicted the hazards in these cases.

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Updated 2021-04-15