a b s t r a c tSafety studies for production and use of hydrogen reveal the importance of accurate prediction of the overpressure effects generated by delayed explosions of accidental high pressure hydrogen releases. Analysis of previous experimental work demonstrates the lack of measurements of turbulent intensities and lengthscales in the flammable envelope as well as the scarceness of accurate experimental data for explosion overpressures and flame speeds. AIR LIQUIDE, AREVA STOCKAGE ENERGIE and INERIS join in a collaborative project to study un-ignited and ignited high pressure releases of hydrogen.The purpose of this work is to map hydrogen flammable envelopes in terms of concentration, velocity and turbulence, and to characterize the flame behaviour and the associated overpressure. These experimental results (dispersion and explosion) are also compared with blind FLACS modelling.
Some years ago, one of the authors (Proust, 2015) published the conclusions of a rather large experimental work devoted to the gas flame acceleration down a long pipe. It was concluded that the flame propagation could be represented by a constantly accelerating piston. The acceleration parameter seems to be primarily linked to the expansion velocity of the burnt product. Other parameters seemed of secondary importance questioning in particular the respective roles of the turbulence of the flame and of the instabilities. Further experiments were performed using perfectly smooth and rough tubes (figure 1), varying the diameter of the pipe (150 and 250 mm) and the reactivity of the mixtures (methane-air and hydrogen air at various equivalence ratios). The smooth pipe is transparent enabling a direct visualization of the flame during the flame propagation and a refined resolution of the flame trajectory (in the steel pipes standard flame sensors were used). The pressure was measured at various locations but also the flow velocities in the boundary to try and detect any turbulence development. Only homogeneous and quiescent mixtures were studied and the flame was propagated from a closed ignition end toward the other open end. The results of the parametric study are presented in this paper.
This paper summarises the results from a blind-prediction study for models developed for estimating the consequences of vented hydrogen deflagrations. The work is part of the project Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations (HySEA). The scenarios selected for the blind-prediction entailed vented explosions with homogeneous hydrogen-air mixtures in a 20-foot ISO container. The test program included two configurations and six experiments, i.e. three repeated tests for each scenario. The comparison between experimental results and model predictions reveals reasonable agreement for some of the models, and significant discrepancies for others. It is foreseen that the first blind-prediction study in the HySEA project will motivate developers to improve their models, and to update guidelines for users of the models.
Since the pioneering work of Harrison and Eyre (1986), the existence of secondary or external explosion outside explosion vents is recognized. It was later shown (Proust, 2004(Proust, , 2010) that the phenomenon is rather systematic and that this explosion can be much more powerful than the internal explosion particularly when the mixture is very reactive. But today, the understanding of the formation of the external cloud and its subsequent combustion remains largely outstanding. Very rapid burning was noticed and significant UVCE pressure effects. In some circumstances, a preexisting flammable cloud encompasses the vented vessel, like in Buncefield for instance. What would happen if the cloud is ignited inside the vessel resulting in an external explosion developing inside the preexisting flammable cloud ? In this paper, new information is presented about the physics of the external explosion and the subsequent combustion of outside cloud. Experiments and numerical simulations were performed.
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