Developing a Model Evaluation Protocol for CFD Analysis of Hydrogen Safety Issues: The SUSANA Project

1. Development of a model evaluation protocol for CFDanalysis of hydrogen safety issues the SUSANA project D. Baraldi (1), D. Melideo. (1), A. Kotchourko (2), K. Ren (2), J. Yanex(2), O. Jedicke (2), S.G. Giannissi (3), I.C. Tolias (3), A.G. Venetsanos(3), J. Keenan (4), D. Makarov (4), V. Molkov (4), S. Slater (5), F. Verbecke (6), A. Duclos (6) 1 - European Commission, Joint Research Centre (JRC), 2 - Karlsruhe Institute for Technology (KIT), 3 - Environmental Research Laboratory, National Center for Scientific research Demokritos, 4 - HySAFER Centre, University of Ulster, 5 - Element Energy Limited 6 - ArevaStockaged'Energie SAS 6th International Conference of Hydrogen Safety 18-21 October – Yokohama, Japan

2. Background • Hydrogen safety issues is a crucial aspect for a wide spread deployment and use of hydrogen and fuel cell technologies • Hydrogen technologies must have the same or lower level of hazard and associated risk compared to conventional fossil fuel technologies European Commission| ICHS2015

3. Context • Computational Fluid Dynamics (CFD) is increasingly used to perform safety analysis of potential accident scenarios (production, storage, distribution of hydrogen and its use in fuel cells) • CFD is a powerful numerical tool that can provide useful data and insights but it also requires a high level of competence and knowledge in order to be used in a meaningful way • To apply CFD with a high level of confidence on the accuracy of the simulation results, two main issues have to be addressed: • the capability of the CFD models to accurately describe the relevant physical phenomena • the capability of the CFD users to follow the correct modelling strategy. • The reliability/accuracy of the CFD results remains a significant concern. European Commission| ICHS2015

4. Gaps in CFD modelling • Workshop with recognised experts in the field of hydrogen safety • Identification of gaps in CFD modelling and simulation of hydrogen release and combustion European Commission| ICHS2015

5. Gaps in CFD modelling • One of the main gaps: the lack of a Model Evaluation Protocol (MEP) for hydrogen technologies safety • HyMEP: • The first MEP for hydrogen technologies safety • To be beneficial for all the CFD developers (academia and research institutes) and users (like industry and consultancy companies) but also for regulatory/certifying bodies • To evaluate the accuracy of the CFD models • To assess user capability of correctly using the codes European Commission| ICHS2015

6. The SUSANA Project • SUpport to SAfetyANalysis of Hydrogen and Fuel Cell Technologies (www.support-cfd.eu) • The SUSANA project (co-funded by the Fuel Cell and Hydrogen Joint Undertaking): producing a Model Evaluation Protocol for hydrogen technologies safety (HyMEP) European Commission| ICHS2015

7. Existing Protocols in other fields • Model Evaluation Group (MEG) established by the EC in 1994 for consequence models • Evaluation protocol in specific areas like heavy gas dispersion (HGD) and gas explosions (MEGGE, 1996) • Scientific Model Evaluation Techniques for Dense Gas Dispersion Models in Complex Situations (SMEDIS) (Daish et al., 2000) • Evaluation protocol for LNG dispersion models (Ivings et al., 2007) • HyMEP is the first protocol for hydrogen technologies safety • HyMEP is the first protocol including all relevant phenomena (release, dispersion, ignition, deflagrations, detonations and fires) European Commission| ICHS2015

8. HyMEP Structure • Stage 1: Scientific Assessment • Initial critical analysis of the model based on available knowledge in the field • Critical review: physical, mathematical and numerical model basis • Identify the known and/or expected weakness and strengths from available literature and knowledge • Scientific content: Assumptions/simplifications/applicability range European Commission| ICHS2015

9. HyMEP Structure • Stage 2: Verification • Verification is used to ensure that a mathematical model has been correctly implemented in software i.e. the equations are correctly solved • Verification Database European Commission| ICHS2015

10. HyMEP Structure • Stage 3: Validation • Model outputs are compared with measurements of physical parameters to demonstrate that the model captures “real world” behaviour across its intended range of applicability. • Quantitative comparison of experimental observations vs. model predictions • Validation Database European Commission| ICHS2015

11. HyMEP Structure • Stage 4: Sensitivity study • Grid independency • Time-step • CFL sensitivity • Numerical scheme • Boundary conditions • Domain size European Commission| ICHS2015

12. HyMEP Structure • Stage 5: Quantitative Assessment Criteria • Identification of target variables for each phenomenon under consideration • Statistical analysis: • Performance parameters • Methodology • Quantitative criteria • Sensitivity and uncertainty European Commission| ICHS2015

13. HyMEP Structure • Stage 6: Assessment Report • Analysis of information supplied by model developer/expert user. • Detailed model description • Scientific assessment • Verification and validation • Sensitivity study • Statistical analysis • Conclusions European Commission| ICHS2015

14. HyMEP supporting documents • D2.1: State of the art in physical and mathematical modelling of safety phenomena relevant to FCH technologies. • D2.2: Critical analysis and requirements to physical and mathematical models. • D3.2: Guide to best practices in numerical simulations European Commission| ICHS2015

15. The Model Validation Database • First version (www.support-cfd.eu) including ~30 experiments • Type of experiments: • release and dispersion (indoors and outdoors, small enclosures and garage facilities, and vented configurations): performed with gaseous hydrogen (or helium) and only one with liquid hydrogen • ignition: investigation of the self-ignition of gaseous hydrogen in a pressurized tube at different pressures with a T shaped pressure relief device • deflagrations (different hydrogen concentrations, an open environment, a closed or vented box, and the presence of obstacles) • detonations (detonations of lean hydrogen-air mixtures (20%, 25%) in a closed large scale facility) • DDT: first set with hydrogen in straight pipes of three different diameters and with different gas concentrations; second set explosions in an obstructed 12 m long tube with a 15% hydrogen-air mixture • Fires (in the next version of the database) European Commission| ICHS2015

16. Benchmarking activities (ongoing) • Some experiments have been selected from the Validation database for benchmarking activities • To test the stages of the HyMEP • Indication of the accuracy • Range of applicability of each modelling approach • Assessment or the performance of each model for each kind of phenomena • To suggest values for the statistical performance measures European Commission| ICHS2015

17. Benchmarking activities (ongoing) • Release and Dispersion (HELIUM) • He is often used in release experiments for safety reasons • He is the most similar element to H2 in terms of buoyancy • See presentation on Tuesday: "Comparisons of helium and hydrogen releases in 1 m3 and 2 m3 two vents enclosures: concentration measurements at different flow rates and for two diameters of injection nozzle" (Gilles Bernard-Michel, Deborah Houssin) European Commission| ICHS2015

18. Release and dispersion: GAMELAN • Example of statistical analysis European Commission| ICHS2015

19. Release and dispersion: GAMELAN • CEA-GAMELAN facility with size 0.93x0.93x1.26 m • Helium source centred horizontally is located at 21 cm from floor • Release rate 180 NL/min (nozzle = 5 mm) • The vent (180 x 180 mm) located in the middle of the wall and 20 mm below the ceiling • He concentration (v/v) was measured at various heights from floor European Commission| ICHS2015

20. Release and dispersion: GAMELAN • CFD RESULTS - NCSRD • ADREA-HF CFD code • The turbulence model is the standard k-ε including the buoyancy terms Steady state @ 400 s European Commission| ICHS2015

21. Release and dispersion: GAMELAN • CFD RESULTS – Statistical analysis • ADREA-HF CFD code • The turbulence model is the standard k-ε including the buoyancy terms "Good" model (in terms of atmospheric dispersion): • FB abs value < 0.3 • 0.7 < MG < 1.3 • FB negative • MG < 1 model overall over-predicts the He conc. at steady state European Commission| ICHS2015

22. Release and dispersion: SBEP21 • Example of model sensitivity European Commision| ICHS2015

23. Release and dispersion: SBEP21 • CEA-GARAGE facility representing a realistic single vehicle private garage • Release phase (18 L/min for 3740 s) + diffusion phase European Commission| ICHS2015

24. Release and dispersion: SBEP21 • CFD RESULTS - JRC European Commission| ICHS2015

25. Release and dispersion: SBEP21 • CFD RESULTS – JRC (effect of the mesh type) Tetra is not suitable for diffusion phase European Commission| ICHS2015

26. Spontaneous ignition • Example of validation • Investigation of the effect of a relevant parameter European Commission| ICHS2015

27. Spontaneous ignition • University of Ulster has simulated the experiments carried by Golub et al. [1] • H2 released from a high pressure system into a channel ending in a T-shaped nozzle mimicking a Pressure Relief Device (PRD) • Initial H2 pressures of 1.5 MPa and 2.9 MPa [1] V.V. Golub, V.V. Volodin, D.I. Baklanov, S.V.Golovastov, D.A. Lenkevich, Experimental investigation of hydrogen ignition at the discharge into channel filled with air. In: Physics of extreme states of matter, ISBN 978-5-901675-96-0; 2010, 110-113. Chernogolovka. High Pressure tube PRD High Pressure tube Burst disk European Commission| ICHS2015

28. Spontaneous ignition Temperature No combustion chemical reaction 1.5MPa Initial P hydroxyl concentration Temperature 2.9MPa Initial P hydroxyl concentration European Commission| ICHS2015

29. Deflagration • Example of geometry model sensitivity European Commission| ICHS2015

30. Deflagration • The experiment HyIndoor_WP3 performed by KIT • Reproduced numerically with the code COM3D by KIT • The KIT facility is a chamber similar to a garage box with glass walls filled with a 18% hydrogen-air mixture • The ignition was triggered at the centre of the wall opposite to a 0.5mx0.5m vent European Commission| ICHS2015

31. Deflagration Initial simple CFD model Intermediate complex CFD model European Commission| ICHS2015

32. Conclusions • Intermediate results from the collaborative SUSANA project • Aim of the project is to develop a Model Evaluation Protocol (HyMEP) for CFD models for safety analyses of hydrogen and fuel cell technologies • HyMEP draft document is almost ready • The HyMEP structure with the main stages have been shown • A verification database and a validation database under development • Some examples of benchmarking exercises have been shown European Commission| ICHS2015

33. Next steps The SUSANA project will finish in August 2016 • Would you like to participate to the review of the HyMEP draft document in the first months of 2016? • Would you like to participate to the final dissemination workshop probably in June 2016 (Exact date and place to be defined)? • Would you like to receive the final version of the document? If interested in any of the above possibilities, please get in contact with daniele.baraldi@ec.europa.eu ACKNOWLEDGEMENTS The authors would like to thank the Fuel Cell and Hydrogen Joint Undertaking for the co-funding of the SUSANA project (Grant-Agreement FCH-JU-325386) European Commission| ICHS2015