ulster.ac.uk

Workshop CFD and engineering tools for experimentsD. Makarov, D. Cirrone, V. Shentsov, S. Kashkarov, V. Molkov

4th Meeting PRESLHY project HSE, Buxton, UK

8 November 2019

e-Laboratory on hydrogen safety

e-LaboratoryEngineering tools for H2 Safety

The e-Laboratory (NET-Tools project 2017-2020) is aimed to support education of undergraduate and postgraduate students, training of engineers and technicians, etc., in the area of H2FC technologies

32 tools are planned to be delivered in total Hands-On Session on the use of e-Laboratory are

regularly organised to help users to understand the engineering tools. Next session will be on 15th January 2020

e‐Labo

ratory

e‐Labo

ratory

e‐Engineeringe‐Engineering

Renewable energy system (RES) toolsRenewable energy system (RES) tools 1. Design & Optimisation of hybrid RES – Hydrogen autonomous power systems for isolated communities and sites (islands, etc).1. Design & Optimisation of hybrid RES – Hydrogen autonomous power systems for isolated communities and sites (islands, etc).

Fuel cells (FC) toolsFuel cells (FC) tools

1. Simulation of SOFC based on natural gas as fuel1. Simulation of SOFC based on natural gas as fuel2. Energy balances and hydrogen costs for various electrolysis techniques2. Energy balances and hydrogen costs for various electrolysis techniques3. Cell and stack models for both fuel cells and electrolysis3. Cell and stack models for both fuel cells and electrolysis4. Thermo‐mechanical models to predict lifetime of high temperature FCs and electrolysis4. Thermo‐mechanical models to predict lifetime of high temperature FCs and electrolysis

Storage toolsStorage tools 1. Storage material properties estimation and performance assessment based on a “materials‐by‐design” multi‐scale approach1. Storage material properties estimation and performance assessment based on a “materials‐by‐design” multi‐scale approachFC integrated into 

CHP toolsFC integrated into 

CHP tools 1. Simulation of FC system integrated into mCHP application, including electrolyser operation1. Simulation of FC system integrated into mCHP application, including electrolyser operation

Safety engineering tools

Safety engineering tools

1. Jet parameters model1. Jet parameters model2. Adiabatic and isothermal model of blowdown of storage tank dynamics2. Adiabatic and isothermal model of blowdown of storage tank dynamics3. Flame length correlation and three hazard distances for jet fires3. Flame length correlation and three hazard distances for jet fires4. Similarity law for concentration decay in hydrogen expanded and under‐expanded jets and unignited jet hazard distances4. Similarity law for concentration decay in hydrogen expanded and under‐expanded jets and unignited jet hazard distances5. Pressure peaking phenomenon for unignited releases5. Pressure peaking phenomenon for unignited releases6. Passive ventilation in an enclosure with one vent: uniform hydrogen concentration6. Passive ventilation in an enclosure with one vent: uniform hydrogen concentration7. Mitigation of uniform mixture deflagration by venting technique7. Mitigation of uniform mixture deflagration by venting technique8. Forced ventilation system parameters8. Forced ventilation system parameters9. Blast wave from high‐pressure rupture without and with combustion9. Blast wave from high‐pressure rupture without and with combustion10. Effect of buoyancy on decrease of hazard distance for unignited releases10. Effect of buoyancy on decrease of hazard distance for unignited releases11. Pressure peaking phenomenon for ignited releases11. Pressure peaking phenomenon for ignited releases12. Upper limit of hydrogen inventory in closed space12. Upper limit of hydrogen inventory in closed space13. Mitigation of localised non‐uniform deflagration by venting13. Mitigation of localised non‐uniform deflagration by venting14. Effect of buoyancy on hazard distances for jet fires  14. Effect of buoyancy on hazard distances for jet fires  15. Calculation of fireball diameter for rupture in a fire of a stand‐alone and an under‐vehicle hydrogen storage tanks15. Calculation of fireball diameter for rupture in a fire of a stand‐alone and an under‐vehicle hydrogen storage tanks16. Choked flow calculation using NIST‐EoS16. Choked flow calculation using NIST‐EoS

e‐Sciencee‐Science

Property toolsProperty tools1. Normal Hydrogen thermo‐physical properties using the NIST‐EoS, (Helmholtz free energy based)1. Normal Hydrogen thermo‐physical properties using the NIST‐EoS, (Helmholtz free energy based)2. The Abel‐Noble EOS to calculate CGH2 mass in a volume at particular pressure and density2. The Abel‐Noble EOS to calculate CGH2 mass in a volume at particular pressure and density

Electrochemistry tools

Electrochemistry tools

1. Fundamental electrochemistry equations, design PEM, optimal porosity of gas diffusion electrodes, ionic conductivity: a. Electrochemical potential; b. Nernst equation; c. Faraday laws of electrolysis; d. Butler‐Volmer equation; e. Tafel equation; f. Ionic conductivity g. Levich equation1. Fundamental electrochemistry equations, design PEM, optimal porosity of gas diffusion electrodes, ionic conductivity: a. Electrochemical potential; b. Nernst equation; c. Faraday laws of electrolysis; d. Butler‐Volmer equation; e. Tafel equation; f. Ionic conductivity g. Levich equation

Storage toolsStorage tools 1. Comsol Multiphysics for simulation of tanks and integrated systems “tank‐FC”1. Comsol Multiphysics for simulation of tanks and integrated systems “tank‐FC”

FC toolsFC tools 1. Modelling of transport processes in electrodes and electrolytes:1. Modelling of transport processes in electrodes and electrolytes:

HyFOAMHyFOAM

1. Release and dispersion of horizontal under‐expanded hydrogen jet (HSL)1. Release and dispersion of horizontal under‐expanded hydrogen jet (HSL)2. Large scale deflagration in the open atmosphere (Fraunhofer ICT)2. Large scale deflagration in the open atmosphere (Fraunhofer ICT)3. Blast wave and fireball from high‐pressure tank rupture in a fire (Weyandt)3. Blast wave and fireball from high‐pressure tank rupture in a fire (Weyandt)4. Hydrogen/helium dispersion in vented enclosures (CEA)4. Hydrogen/helium dispersion in vented enclosures (CEA)5. Vented deflagration (FM Global)5. Vented deflagration (FM Global)

e-Laboratory overview

Example of application: H2 releasesSimilarity law for concentration decay This model predicts axial concentration decay of hydrogen for sub‐sonic, 

sonic, and super‐sonic momentum controlled jets.  It is also used for calculation of hazard distances formed by the size of the 

flammable envelope

= Axial distance from nozzle, m= Nozzle diameter, m= Density at nozzle exit, kg/m3= Air density, kg/m3= Mass fraction of hydrogen at 

axial distance  , ND

5.4∙

Under‐expanded jets: Utilises ‘Hydrogen jet parameters’ tool

Expanded jets: Utilises Isentropic pressure and density relationships

Example of application: H2 releasesSimilarity law for concentration decay

https://elab‐dev.iket.kit.edu/#/tools/similarity_lawsThis tool allows to calculate: hydrogen concentration decay

Application for experimentsDisCha hydrogen releases

r1=10 cmr2=25cm

Aim: assess the location of hydrogen concentration sensors

Fast blowdown release

Fast blowdown releaseCFD models overview

1. Notional nozzle modelUnderexpanded release

2. Blowdown dynamic modelfinite tank volume, unsteady release

3. Volumetric jet sourceDynamics notional nozzle diameter

1. Notional nozzle modelOverviewMathematical model: conservation of mass conservation of total energy the Abel-Nobel equation of stateAssumptions at notional nozzle: • atmospheric pressure• uniform sonic velocity• 100% vol. H2

Calculation scheme:

1 2 3

Blowdown simulation drawbacks:Notional nozzle diameter is a function of vessel pressure

Inflow boundary would require continues change of calculation domain

2 vessels of 98 litres capacity each Initial pressure was P1=208 bar Initial temperature was estimated as T1=288 K Hydrogen mass stored in the facility mH2=3.025 kg Minimum orifice in the pipeline Ø9.5 mm Discharge pipeline installation: horizontal, at the height 1.2 m

2. Blowdown modelValidation case (1/2)HSL hydrogen release experiment

2. Blowdown modelValidation case (2/2)Experimental vs. simulated pressure dynamics

3. Volumetric release Solution for jet release CFD

Jet generation via volumetric source terms: Constant volume for source terms application No alterations to calculation domain

Mass conservation equation:

Momentum conservation equation:

Energy conservation equation:

Hydrogen conservation equation:

Turbulent kinetic energy equation:

Turbulent kinetic energy dissipation equation:

⁄

⋅ ⁄

⋅ ⋅ ⁄

⁄

⋅ ⁄

⋅ ⁄

3. Volumetric release Volumetric release validation (1/2) Quasy-steady state underexpanded jet

(HSL/SHELL experiment, HySafe SBEP)Experiment: Roberts P.T., Shirvill L.C., Roberts T.A. // Dispersion of hydrogen from high-pressure sources. Hazards. Proc. of Hazards XIX Conference, 28-30 March 2006, Manchester, UK

Underexpanded jet experiment setupPressure 10.0 MPaNozzle 3 mmDischarge mass flow rate: 0.045kg/s

Notional nozzleNotional nozzle 22 mm

Calculation domainDimensions: L x W x H=18 x 7.0 x 5.33 m. Discretisation 51 × 51 × 70 hex CVs (total number: 181,935)

Inverse problem: constant , varying release volumeL × D × H=1 deff; 2 deff; 4 deff; 8 deff;

3. Volumetric release Volumetric release validation (2/2)

Measured vs simulated hydrogen fraction(constant , varying release volume)

HSL blowdown simulation

Simulation setupRelease duration t=0-10 sCalculation time t=0-17 sPressure 10.0 – 0.59 MPa (gauge)Notional nozzle 0.100 – 0.019 m (5 times!)Discharge mass flow rate: 0.947 - 0.056 kg/s

Calculation domainDimensions: L W H= 101.4 39.8 21.2 m . Discretisation: hex CVs, total number: 784,204

Release volumeL D = 0.1 0.1 m

HSL blowdown simulationResults 1

HSL blowdown simulationResults 2

Fire CFD with chemical kinetics

Indoor fire regimes: Well-ventilated (complete combustion of hydrogen inside) Under-ventilated (insufficient air to completely burn H2)

Chemical kinetics dictates underventilatedfire dynamics: Self-extinction and micro-combustion External flame Re-ignition, etc.

Underventilated fires modelling is challenging

Fire CFD with chemical kineticsModelling challenges

Fire CFD with chemical kineticsModel brief

The Reynolds averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) model.

The model is based on the renormalization group (RNG) k-ε turbulence model (Yakhot and Orszag).

The eddy dissipation concept (EDC) model by Magnussen et al. for simulation of non-premixed combustion at large scale with chemistry.

The 18-step reduced chemical reaction mechanism of hydrogen combustion in air with 8 species (subset of the Peters and Rogg’s mechanism that excludes H2O2 formation and consumption).

The in-situ adaptive tabulation (ISAT) algorithm by Pope that accelerates the chemistry calculations by 2-3 orders of magnitude.

Fire CFD with chemical kineticsWell ventilated fire performanceHydrogen release 60 m/s (0.11 g/s), vertical vent 30×3 cm

H2 T

Fire CFD with chemical kineticsUnderventilated fire performance

H2 T

Fire CFD with chemical kineticsIndoor jet temperature

Fire CFD with chemical kineticsOutdoor jet temperature

Localised fire under a vehicle

Localised fires under a carCar and tank geometry, TCs and fire location

5.2 m 1.82 m

1.47 m

Fire source (No.1, No.2) coverslocalised area of tank 0.25 m

0.25 m

Conjugate heat transfer from fire to700 bar Type 4 tank (LxD=0.91x0.325 m).

25 mm

Localised fire area250 mm

TC1 TC2 TC4 TC6TC5TC3

In-situ fire dynamics

Case 2: HRR/A=1 MW/m2Case 1: HRR/A=0.2 MW/m2

600°C (GTR#13 min required)1030°C

Video

Ulster LES deflagration model

LES deflagration modelIntroduction

Large Eddy Simulation (LES) may provide a more reliableturbulence model than Reynolds-Averaged Navier-Stokes(RANS) approach for large-scale unsteady motions.

The rate-controlling processes are determined for non-reacting flows by the resolved large scales.

In turbulent combustion (high Reynolds and Damkohlernumbers) the rate-controlling processes of molecularmixing and chemical reaction occur at the scales thinnerthan the resolved scales (Peters, 2000). Hence, theseprocesses have to be modelled.

Modelling is particularly challenging for safety applicationswith characteristics scales tens and hundreds of meters

LES deflagration modelNumerical requirements There is a numerical requirement to a minimum number of

computational cells through any numerical “front”, e.g. flame or shock wave.

The flame front thickness of at least 4 control volumes of rectangular grid was recommended by Catlin et al. (1995).

For tetrahedral unstructured grids 4-5 points through the numerical flame front thickness can be “collected” at a distance equal to 2-3 edges of tetrahedral control volume.

It means that LES can resolve elements of a flame front structure with a size larger than at least 4-6 edges of the tetrahedron.

Smaller sub-grid structures and relevant phenomena can only be modelled.

LES deflagration modelModelling flame acceleration phenomena

Four mechanisms responsible for the increase of flame front surface area in large-scale deflagrations:

Flow turbulence (Yakhot’s sub-grid scale model)

Turbulence generated by the flame front itself (ΞK)

Preferential diffusion (Ξlp )

Fractal-like flame wrinkling (Ξf)

Rayleigh-Taylor (RT) instability (ΞRT)

LES deflagration modelValidation (Shell SOLVEX experiment)Puttock et al. (1996):“the external explosion …increasing the internal pressure by about a factor of four…”

Shell SOLVEX facility:547-m3

Mixture: 10.5% CH4-air,initially quiescentIgnition:centre of the rear wall

LES deflagration modelValidation …

Ulster LES model

Shell 4

Shell 3

LES deflagration modelValidation (pressure dynamics)Internal - external combustion interaction: additional intensification factor a=12 in 100 ms outside the enclosure

Time, ms

Gau

ge p

ress

ure,

Pa

0 200 400 600 800 1000 1200 1400-4000-3000-2000-1000

0100020003000400050006000

Experiment, inside the enclosureSimulation, inside the enclosureSimulation, outside the enclosure

Externalexplosion

Simultaneous pressure rise

Negative pressure wave

atuc cgradSS ~

LES deflagration modelValidation (pressure dynamics)Pressure outside the enclosure at locations 6.1, 30.3, 53.9 m from the vent

Time, ms

Gau

ge p

ress

ure,

Pa

0 200 400 600 800 1000 1200 1400-2000

-1000

0

1000

2000

3000

4000Experiment, 6.1, 30.3, 53.9 mSimulation, pressure at 6.1 mSimulation, pressure at 30.3 mSimulation, pressure at 53.9 m

ConclusionsEngineering toolsSimplicity of application and immediacy of

calculation.CFD modelling Simulation of diversified scenarios that can not

be represented by the engineering tool assumptions.

Expand range of applicability of the engineering model by using simulations as verification tool.

Give insights into the dynamics of the scenario investigated.

Any questions?

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