Abstract
This research investigates and closes a number of knowledge gaps in the safety of the indoor use of fuel cell and hydrogen (FCH) systems. New analytical models were developed and validated for steady state release and dispersion of hydrogen in an enclosure with one and two vents. Jet fire phenomena were studied for different combustion regimes, including well-ventilated and under-ventilated regimes, self-extinction, re-ignition and an external jet flame.To identify aims and objectives a broad literature review of theoretical, experimental and modelling work relating to hydrogen releases and jet fires has been completed. Based on knowledge gaps identified a model for passive ventilation of a sustained gaseous leak in an enclosure with one vent has been developed on the assumption of perfect mixing. The model predictions are compared against experimental helium concentration for both uniform and non-uniform helium-air mixtures. The criterion for mixture uniformity in an enclosure with one vent is suggested. Model equations derived for passive ventilation aided for the developments of engineering tools in the form of nomograms. These nomograms can be used to calculate the mass flow rate limit leading to 100% hydrogen concentration and calculation of steady state hydrogen concentration in the enclosure. In situations where simple analytical formulas are not applicable use of CFD is required. For this reason Numerical and physical requirements were formulated for simulations of light gas release and dispersion in one vent enclosure based on a parametric study and are acceptable from hydrogen safety engineering point of view.
Hydrogen jet fire phenomenon requires numerical investigation therefore a study performed to identify general rules for hydrogen fire regimes in an enclosure. Two modes of under-ventilated fires were observed and identified: external flame and self-extinction of the flame. The phenomenon of the hydrogen flame “re-ignition” by termination of hydrogen supply in an enclosure with one and two vents was reproduced in numerical experiments and recommendations are given. An equation is proposed for the prediction of time when, two possible modes of under-ventilated regimes can occur: self-extinction or an external flame.
The results of the current research have contributed to the European guidelines deliverable D 5.1 of the “Pre-normative research on safe indoor use of fuel cells and hydrogen systems” HyIndoor project (www.hyindoor.eu).
| Date of Award | May 2015 |
|---|---|
| Original language | English |
| Sponsors | Fuel Cells and Hydrogen Joint Undertaking |
| Supervisor | Vladimir Molkov (Supervisor), Sile Brennan (Supervisor) & Dmitriy Makarov (Supervisor) |
Keywords
- safety
- indoor
- hydrogen
- release
- jet fire
- fire regimes
- ventilation
- CFD
- modelling
- guidelines
Cite this
- Standard