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O.R. Hansen; J. Renoult; M.P. Sherman; S.R. Tieszen


The FLACS CFD-tool for consequence prediction has been developed continuously since 1980. Theinitial focus was explosion safety on offshore oil platforms, in recent years the tool is also applied tostudy dispersion, hydrogen safety, dust explosions and more. A development project sponsored byNorsk Hydro, Statoil and Ishikawajima Heavy Industries (IHI) was carried out to improve themodelling and validation of hydrogen dispersion and explosions. In this project GexCon carried out200 small-scale experiments on dispersion and explosion with H2 and mixtures with H2 and CO or N2.Experiments with varying confinement, congestion, concentration, and ignition location wereperformed. Since the main purpose of the tests was to produce good validation data, all tests weresimulated with the FLACS-HYDROGEN tool. The simulations confirmed the ability to predictexplosions effects for the wide range of scenarios studied. A few examples of comparisons will beshown. To build confidence in a consequence prediction model, it is important that the scales used forvalidation are as close as possible to reality. Since the hazard to people and facilities, and the risk, willgenerally increase with scale, validation against large-scale experiments is important. In the 1980s aseries of large-scale explosion experiments with H2 was carried out in the Sandia FLAME facility andsponsored by the US Nuclear Regulatory Commission. The FLAME facility is a 30.5m x 1.83m x2.44m channel, tests were performed with H2 concentrations from 7%2to 30%2 with varying degree oftop venting (0%2 13%2and 50%2 and congestion (with or without baffles blocking 33%2of the channelcross-section). A wide range of flame speeds and overpressures were observed. Comparisons are madebetween FLACS simulations and FLAME tests. The main conclusion from this validation study is thatthe precision when predicting H2 explosion consequences with FLACS has been improved to a veryacceptable level.