Development of a model evaluation - PowerPoint Presentation

Slide1

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 -

Areva

Stockage

d'Energie

SAS

6

th

International Conference of Hydrogen Safety

18-21 October – Yokohama, Japan

Slide2

European Commission | ICHS20152Background

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

Slide3

ContextComputational 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 phenomenathe capability of the CFD users to follow the correct modelling strategy.

The reliability/accuracy of the CFD results remains a significant concern. 3European Commission

|

ICHS2015

Slide4

Gaps in CFD modelling4

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

Slide5

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 modelsTo assess user capability of correctly using the codes

Gaps in CFD modelling

5

European

Commission

|

ICHS2015

Slide6

SUpport

to

SAfety

ANalysis

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

)

The SUSANA Project

6

European

Commission

|

ICHS2015

Slide7

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 safetyHyMEP is the first protocol including all relevant phenomena (release, dispersion, ignition, deflagrations, detonations and fires)

Existing Protocols in other fields

7

European

Commission

| ICHS2015

Slide8

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

HyMEP

Structure

8

European

Commission

|

ICHS2015

Slide9

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

9

HyMEP

Structure

European

Commission

|

ICHS2015

Slide10

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

10

HyMEP

Structure

European

Commission

|

ICHS2015

Slide11

Stage 4: Sensitivity study

Grid independency

Time-step

CFL sensitivity

Numerical scheme

Boundary conditions

Domain size

11

HyMEP

Structure

European

Commission

|

ICHS2015

Slide12

Stage 5: Quantitative Assessment Criteria

Identification of target variables for each phenomenon under consideration

Statistical analysis:

Performance parameters

Methodology

Quantitative criteria

Sensitivity and uncertainty

12

HyMEP

Structure

European

Commission

|

ICHS2015

Slide13

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

13

HyMEP

Structure

European

Commission

|

ICHS2015

Slide14

14HyMEP 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

Slide15

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)

The Model Validation Database

15

European

Commission

|

ICHS2015

Slide16

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

Benchmarking activities (ongoing)

16

European

Commission

|

ICHS2015

Slide17

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

)

Benchmarking activities (ongoing)

17

Release and Dispersion

GAMELAN

JRC, NCSRD, UU

SBEP_21

HSL,

JRC

Ignition

PRD (Pressure Relief Device

)

UU

Deflagrations

HyIndoor_WP3

KIT

Open atmosphere

deflagration

NCSRD, UU

Detonations

KI_RUT_hyd05

KIT

KI_RUT_hyd09

KIT

European

Commission

|

ICHS2015

Slide18

Example of statistical analysis

Release and dispersion: GAMELAN

18

European

Commission

|

ICHS2015

Slide19

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

Release and dispersion: GAMELAN

19

European

Commission

|

ICHS2015

Slide20

CFD RESULTS - NCSRD

ADREA-HF CFD code

The turbulence model is the standard k-ε including the buoyancy terms

Release and dispersion: GAMELAN

20

Steady state @ 400 s

European

Commission

|

ICHS2015

Slide21

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

Release and dispersion: GAMELAN

21

model overall over-predicts the

He conc. at

steady state

European

Commission

|

ICHS2015

Slide22

Example of model sensitivity

Release and dispersion:

SBEP21

22

European

Commision

|

ICHS2015

Slide23

CEA-GARAGE facility representing a realistic single vehicle private garage

Release phase (18 L/min for 3740 s) + diffusion phase

Release and dispersion:

SBEP21

23

European

Commission

|

ICHS2015

Slide24

CFD RESULTS - JRC

Release and dispersion:

SBEP21

24

European

Commission

|

ICHS2015

Slide25

CFD RESULTS – JRC (effect of the mesh type)

Release and dispersion:

SBEP21

25

European

Commission

|

ICHS2015

Tetra is not suitable for diffusion phase

Slide26

Example of validation

Investigation of the effect of a relevant parameter

Spontaneous ignition

26

European

Commission

|

ICHS2015

Slide27

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

.

Spontaneous ignition

27

European Commission | ICHS2015

High Pressure tubeHigh Pressure tube

PRD

Burst disk

Slide28

Spontaneous ignition28European Commission | ICHS2015

1.5MPa Initial P

2.9MPa Initial P

No combustion chemical reaction

Temperature

Temperature

hydroxyl concentration

hydroxyl concentration

Slide29

Example of

geometry model sensitivity

Deflagration

29

European

Commission

|

ICHS2015

Slide30

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

Deflagration

30

European

Commission

|

ICHS2015

Slide31

Deflagration31European Commission | ICHS2015

Initial simple CFD model

Intermediate complex CFD model

Slide32

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 developmentSome examples of benchmarking exercises have been shown

Conclusions

32

European

Commission

| ICHS2015

Slide33

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)

Next steps

33

European

Commission

|

ICHS2015