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A complete multiple-scale solution is constructed for the one-dimensional problem of an oscillating flame in a tube, ignited at a closed end, with the second end open. The flame front moves into the unburnt mixture at a constant burning velocity relative to the mixture ahead, and the heat release is constant. The solution is based upon the assumption that the propagation speed multiplied by the expansion ratio is small compared with the speed of sound. This approximate solution is compared with a numerical solution for the same physical model, assuming a propagation speed of arbitrary magnitude, and the results are close enough to confirm the validity of the approximate solution. Because ignition takes place at the closed end, the effect of thermal expansion is to push the column of fluid in the tube towards the open end. Acoustics set in motion by the impulsive start of the column of fluid play a crucial role in the oscillation. The analytical solution also captures the subsequent interaction between acoustics and the reaction front, the effect of which does not appear to be as significant as that of the impulsive start, however. [ABSTRACT FROM AUTHOR]

Abstract: In many areas European research has been largely fragmented. To support the required integration and to focus and coordinate related research efforts the European Commission created a new instrument, the Networks of Excellences (NoEs). The goal of the NoE HySafe has been to provide the basis to facilitate the safe introduction of hydrogen as an energy carrier by removing the safety related obstacles. The prioritisation of the HySafe internal project activities was based on a phenomena identification and ranking exercise (PIRT) and expert interviews. The identified research headlines were “Releases in (partially) confined areas”, “Mitigation” and “Quantitative Risk Assessment”. Along these headlines existing or planned research work was re-orientated and slightly modified, to build up three large internal research projects “InsHyde”, “HyTunnel”, and “HyQRA”. In InsHyde realistic indoor hydrogen leaks and associated hazards have been investigated to provide recommendations for the safe use of indoor hydrogen systems including mitigation and detection means. The appropriateness of available regulations, codes and standards (RCS) has been assessed. Experimental and numerical work was conducted to benchmark simulation tools and to evaluate the related recommendations. HyTunnel contributed to the understanding of the nature of the hazards posed by hydrogen vehicles inside tunnels and its relative severity compared to other fuels. In HyQRA quantitative risk assessment strategies were applied to relevant scenarios in a hydrogen refuelling station and the performance was compared to derive also recommendations. The integration process was supported by common activities like a series of workshops and benchmarks related to experimental and numerical work. The networks research tools were categorised and published in online catalogues. Important integration success was provided by commonly setting up the International Conference on Hydrogen Safety, the first academic education related to hydrogen safety and the Hydrogen Safety Handbook. Finally, the network founded the International Association for Hydrogen Safety, which opens the future networking to all interested parties on an international level. [Copyright &y& Elsevier]