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1 2017

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Numerical investigation on the effect of obstacles on DDT in hydrogen-air mixure using OpenFOAM

Porowski R., Siatkowski S.

Archivum Combustionis

2017

Vol. 37 nr 1

15--24

During past decades a lot of effort was put into DDT and detonation research both experimental and numerical. However the size of a domain, in which we can simulate DDT is very limited due to computer performance. In days to come, the next challenge will be to create numerical model that would allow us to simulate huge domains such as hydrogen leaks in nuclear power plants. An attempt to create such model was taken by Ettner (2014) who created ddtFOAM solver running on OpenFOAM package dedicated to simulate deflagration-to-detonation transition without resolving all microscopic details of the flow (only 2D simulations). According to Ettner (2014) it works on relatively coarse grid (1x1mm) and shows good agreement with experiments. The purpose of this paper was to investigate the influence of obstacles on DDT and detonation in tube filled with stoichiometric hydrogen-air mixture using ddtFOAM solver for the same geometry as Porowski’s experiments (2013). This work was restricted only to hydrogen-air mixture although in the future it is planned to be extended to other mixtures that Porowski (2013) used in his experiments. Simulated geometry included the tube with length L = 6 m and D=140 mm. Twelve different configurations of obstacle were used, various parameters as BR (Blockage Ratio) ranging from 0.4 to 0.7 and obstacle spacing between 1D and 3D. Our study showed that model captured general features of detonations such as velocity or pressure peak, fairly well. However not always results of simulation was in agreement with experimental studies. Main disagreement was in predicting if DDT occurred or not. Simulations showed steady-state detonation protruding in every case while in experiments sometimes flame propagated in quasi-detonation regime. It should be noted though, that this model is supposed to give more qualitative than quantitative results. Some possible causes for this disagreement of results are then analysed.