CFD Gap Analysis: Accidental Hydrogen Release Modeling

1. Gap Analysis of CFD Modelling of Accidental Hydrogen Release and Combustion D. Baraldi (Joint Research Centre – European Commission) E. Papanikolaou (Joint Research Centre – European Commission) M. Heitsch (Joint Research Centre – European Commission) P. Moretto (Joint Research Centre – European Commission) R.S. Cant (Cambridge University) D. Roekaerts (Delft University) S. Dorofeev (FM Global) A. Kotchourko (Karlsruhe Institute of Technology) P. Middha (Gexcon) A.V. Tchouvelev (H2Can) S. Ledin (Health Safety Laboratory) J. Wen (Kingston University) A. Venetsanos (National Center Scientific Research Demokritos) V.V. Molkov (University Of Ulster)

2. CFD Gap Analysis

3. Computational Fluid Dynamics CFD is a numerical method to solve the fluid governing equations that can not be solved in analytical form. By means of numerical simulations of potential accident scenarios, CFD can provide relevant data for risk assessment of hydrogen technologies (estimates of accident consequences e.g. pressure and thermal loads of hydrogen explosions and jet fires) CFD can provide a valuable contribution to the engineering design of safer hydrogen infrastructures and technologies

4. To achieve the required level of accuracy, the CFD codes/models must undergo an assessment procedure Computational Fluid Dynamics

5. Type of Modeling Gaps • lack of fundamental knowledge or understanding of some aspects of the physical phenomenon resulting in inadequacies and deficiencies of the models; • inability of the CFD model to reproduce and predict the phenomenon from the qualitative and/or quantitative point of view • lack of experiments for validation;

6. Hydrogen Accident Scenarios • Release and dispersion: - gaseous hydrogen - liquid hydrogen - permeation • Auto-ignition • Jet fires • Deflagrations • Detonations and Deflagration to Detonation Transition(DDT)

7. Release/dispersion: Gaseous H2 HySafe Standard Benchmarking Exercise Problem SBEP20: In garage with vents, helium was released under the vehicle for 2 h with 7.200 l/h flow rate E.A. Papanikolaou, A.G. Venetsanos, et al., SBEP-V20: Numerical studies of release experiments inside a naturally ventilated residential garage, Int. Jou. Hydrogen Energy 35 (2010) 4747–4757 Another HySafe SBEP (SBEP21) on similar topic will be presented by A.G. Venetsanos et al, IA-HySafe Standard Benchmark Exercise SBEP-v21: Hydrogen Release And Accumulation Within a Non-ventilated Ambient Pressure Garage At Low Release Rates

8. Release/dispersion: Gaseous H2

9. Release/dispersion: Liquid H2

10. Release/dispersion: permeation History of hydrogen distribution by height above the tank 2D-slice of distribution of hydrogen in a half of the typical garage Molkov V., Bragin M., Brennan S., Makarov D., Saffers J-B., Hydrogen Safety Engineering: Overview of Recent Progress and Unresolved Issues, Proceedings of the International Congress on Combustion and Fire Dynamics, Santander, Spain, 20-23 October 2010.

11. Release/dispersion: permeation

12. Predicted contours of temperature (K) with a rupture time of 5 μs Spontaneous Ignition for a 150 bar release case through a 6 cm long tube Auto-Ignition Predicted contours of OH mass fraction J.X. Wen*, B.P. Xu, V.H.Y. Tam Numerical study on spontaneous ignition of pressurized hydrogen release through a length of tube. Combustion and Flame 156 (2009) 2173–2189

13. Auto-Ignition in T-shape channel T-shape channel - mock-up of Pressure Relief Device (PRD). Spontaneous ignition at storage pressure 29 bar. LES EDC model with inertial membrane (University of Ulster). Ignition initiated in the radial vent channel and extinguished. Combustion is reinitiated in a number of spots outside the PRD. Concentration of hydrogen in these spots just before the ignition is in the range 29-36% by vol. Details to be presented at ICHS 2011 (Bragin M, Makarov D, Molkov V. Paper 171)

14. Auto-Ignition

15. Jet fires Pressure vessel = 20 bar Leak diameter ~ 8 mm Comparison of simulation results with experimental data Zhang, J., Dembele, S. and Wen J. X., Exploratory Study of Under-expanded Sonic Hydrogen Jets and the Resulting Jet Flames, 5th International Seminar on Fire and Explosion Hazards, April 2007, Edinburgh, UK. Contours of the predicted mean temperature by the two-domain approach (left) and the Pseudo Diameter approach -Ewan and Moodie- (right). Over-prediction of temperatures with the PD model inside the jet fires.

16. Jet fires

17. Effect of Lewis number (ratio of thermal and mass diffusivity). Deflagrations: DNS of Planar Flames Le = 0.8 Le = 1.2 Instantaneous pictures of c = 0.8 isosurface coloured by local non-dimensional temperature N.Chakraborty, R.S.Cant: Phys. Fluids 17, 034510, 1-20, 2005.

18. Fluid Structure interactions Deflagrations G.Caretta, R.S.Cant, A.C.Palmer: 9th International Conference on Numerical Combustion, 2002.

19. Deflagrations

20. Deflagrations

21. Numerical simulations of detonations in the RUT facility: CJ parameters are well captured Detonations and DDT A. Heidari, S. Ferraris, J.X. Wen, V.H.Y. Tam, Numerical simulation of large scale hydrogen detonation, International Journal of Hydrogen Energy, 36 (3), pp. 2538-2544

22. Detonations and DDT

23. Conclusions Beyond the specific issues for each accident stage, some general modelling issues can be found in all stages: • Turbulence • Lack of an extensive validation of CFD codes/models that covers all the relevant range of conditions that can be found in hypothetical accident scenarios. • In some cases, lack of complete and accurate experimental data for the CFD validation, especially for real-case configurations. • Lack of a database of experiments for validation of hydrogen models. Experimental matrix for CFD validation for H2 technologies • Lack of a CFD validation protocol for hydrogen like it exists for Liquefied Natural Gas (LNG): the Model Evaluation Protocols (MEP) for assessment of models for accident consequences.