23 results on '"Hydrogen deflagration"'
Search Results
2. Modeling of hydrogen dispersion and explosion of a fuel cell vehicle in an underground parking garage.
- Author
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Huang, Teng, Yang, Fuyuan, Li, Xuefang, Wang, Tianze, and Ouyang, Minggao
- Subjects
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FUEL cell vehicles , *PARKING garages , *FUEL cells , *HYDROGEN , *TEMPERATURE distribution , *GEOMETRIC modeling - Abstract
Numerical simulations were conducted to investigate the hydrogen dispersion and deflagration in an underground garage, considering potential leaks from hydrogen fuel cell vehicles. This study constructed a geometric model based on vehicles equipped with 70 MPa hydrogen tanks and considered various accident scenarios by adjusting the orifice diameter and ignition time. The results indicated that the peak overpressure was influenced by the equivalence ratio, hydrogen distribution and ignition time. Specifically, increasing orifice diameter led to greater overpressure when ignition occurred 0.1 s after release, while the opposite trend was observed for ignition at 1 s or 10 s. Temperature and overpressure were measured to evaluate the hazard distances, revealing inconsistencies between distances determined by pressure and temperature, with the latter yielding larger results. This research contributes to determining affected areas and safety distances in hydrogen accidents, provides references for the design of parking intervals and the development of emergency plans. • Modeled hydrogen dispersion and deflagrations in an underground garage. • Examined the effects of orifice diameters and ignition times on hydrogen explosion. • Investigated the factors influencing peak overpressure. • Pressure and temperature distribution determine different Explosion-affected areas. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
3. Flame propagation characteristics of premixed hydrogen–air deflagration with low concentration in a pipeline.
- Author
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Wang, Qiuhong, Wan, Hongxiang, Gao, Wei, Deng, Jun, Luo, Zhenmin, Yang, Songping, Dai, Aiping, Peng, Bin, and Chen, Jianyi
- Subjects
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FLAME , *RADIANT intensity , *FLAME temperature , *PIPELINES - Abstract
This study used a visualized explosion propagation experimental system to investigate the flame propagation and hydroxyl (OH·) spectral radiation characteristics of hydrogen deflagration at the hydrogen concentration range of 7–17 vol%. The experimental results indicated that maximum flame propagation velocity, maximum explosion pressure, maximum flame temperature, and maximum relative spectral intensity of OH· gradually increased with hydrogen concentration. When concentration increased from 13 vol% to 17 vol%, the time to reach the maximum flame propagation velocity, the formation time of tulip flame, and the duration of the spectral radiation signal of OH· decreased by 52.9%, 55.6%, and 48.2%, respectively. In addition, flame propagation velocity oscillated when the tulip flame appeared, and maximum explosion pressure appeared later than the maximum temperature. Maximum flame propagation velocity, maximum explosion pressure, and maximum flame temperature positively correlated with maximum relative spectral intensity in the reaction system. These findings may serve as an essential reference for the safe and effective use of hydrogen and the research and development of radical targeted explosion suppressants. • Flame propagation velocity oscillates when tulip flame appears. • Maximum spectral intensity is exponentially related to hydrogen concentration. • The OH· content positively correlate with the maximum explosion pressure. • Maximum explosion pressure appears later than maximum temperature. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
4. GASFLOW-MPI analysis on deflagration in full-scale hydrogen refueling station experiments: H2-air premixed cloud and high-pressure H2 jet.
- Author
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Wang, Fangnian, Xiao, Jianjun, and Jordan, Thomas
- Subjects
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FUELING , *BURNING velocity , *HYDROGEN as fuel , *COMBUSTION products , *PARTICLE size determination , *HYDROGEN , *IDEAL gases , *BLAST effect - Abstract
Safety of the hydrogen refueling station under a postulated accident (e.g. leakage) is of great importance in hydrogen energy. The predictive CFD tool GASFLOW-MPI is utilized to simulate the full-scale hydrogen refueling station deflagration experiments with premixed H 2 -air cloud and high-pressure H 2 jet. The overpressures are predicted for an ignition between two dispensers in the premixed trial and a spark in the engine bay in the jet trial, which agree with the experimental data and validate the GASFLOW-MPI as well. Five turbulent burning velocity models are involved to investigate the explosion of the premixed H 2 –air cloud. The Zimont correlation is recommended for the combustion simulation of engineering full-scale H 2 refueling station. The turbulent flame speed is predicted after an ignition resulting in 50–200 m/s, and the flame acceleration happens due to the turbulence effect by obstacles. The developments of the pressure, temperature and H 2 concentration of premixed H 2 -air deflagration, indicate the pressure wave propagates with the reflections on obstacles, and the flammable H 2 cloud is enlarged by the push of combustion product. Moreover, the standard k − ε and DES model are adopted on the jet dispersion analysis. The local flow variables show some differences, but the global properties of average hydrogen concentration, the shape and size of the burnable cloud are similar, which indicates the hydrogen dispersion transient computed by k − ε turbulence model provides a reliable basis for estimating the combustion process. The evolutions of the jet resulting burnable H 2 -air mixture in the domain in terms of H 2 velocity field, concentration and mass are evaluated. The velocity field in jet trial explains that the momentum dominates hydrogen dispersion and result in a corresponding hydrogen concentration, however a large zone with high turbulence forms after combustion. The analysis of H 2 dispersed in the engine bay shows the growth and decay of the hydrogen concentration above some specified value of interest (4 and 10 vol% H 2). Most dispersed H 2 cloud is burnable, and half of the mass distributed in the cloud above 10 vol% may accelerate the flame to sonic. The comparison of the overpressure in k − ε and DES turbulence models with real and ideal gas release sources, shows in general no significant difference. The hydrogen release jet with higher turbulence generates the hydrogen cloud that can result in a large overpressure. • GASFLOW-MPI is validated comprehensively against the H2 deflagration experiments of a full-scale H2 refueling station. • Turbulent burning velocity correlations are investigated in the explosion of the premixed H 2 –air cloud. • Turbulence models are adopted and discussed in the analysis of the high-pressure H 2 jet release and dispersion. • Explosion overpressure and flame propagation in cases of both premixed H 2 –air cloud and high-pressure H 2 jet are presented. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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5. Hydrogen deflagrations in stratified flat layers in the large-scale vented combustion test facility.
- Author
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Liang, Zhe, Gardner, Lee, Clouthier, Tony, and MacCoy, Reilly
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COMBUSTION , *HYDROGEN , *FLUIDIZED-bed combustion , *TESTING laboratories , *ALTITUDES , *NUCLEAR facilities , *FLAME - Abstract
This paper examines the flame dynamics of vented deflagration in stratified hydrogen layers. It also compares the measured combustion pressure transients with 3D GOTHIC simulations to assess GOTHIC's capability to simulate the associated phenomena. The experiments were performed in the Large-Scale Vented Combustion Test Facility at the Canadian Nuclear Laboratories. The stratified layer was formed by injecting hydrogen at a high elevation at a constant flow rate. The dominant parameters for vented deflagrations in stratified layers were investigated. The experimental results show that significant overpressures are generated in stratified hydrogen–air mixtures with local high concentration even though the volume-averaged hydrogen concentration is non-flammable. The GOTHIC predictions capture the overall pressure dynamics of combustion very well, but the peak overpressures are consistently over-predicted, particularly with higher maximum hydrogen concentrations. The measured combustion overpressures are also compared with Molkov's model prediction based on a layer-averaged hydrogen concentration. • Vented deflagration in stratified flat layers. • GOTHIC simulation of vented combustion. • Comparison of combustion overpressure with Molkov's model prediction. • Higher risk of combustion with local high hydrogen. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
6. Experimental tests of inhomogeneous hydrogen deflagrations in the presence of obstacles.
- Author
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Schiavetti, M. and Carcassi, M.N.
- Subjects
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COMPUTATIONAL fluid dynamics , *GAS explosions , *HYDROGEN , *ENGINEERING models , *EXPLOSIONS , *TESTING laboratories - Abstract
Explosion venting is a frequently used measure to mitigate the outcome of deflagration in closed environments. Despite the effort to improve engineering formulas and CFD tools used to predict the vent area needed to meet the desired enclosure protection, work has still to be done to reliably predict the outcome of a vented gas explosion. Blind-prediction exercises recently published by the HYSEA project show a large spread in the predictions by engineering models, including semi-empirical correlations and computational fluid dynamics (CFD) tools. University of Pisa performed experimental tests in a 25 m3 facility in inhomogeneous conditions and with the presence of simple obstacles constituted by plates bolted to HEB beams. The present paper is aimed to share the results of hydrogen dispersion and deflagration tests and discuss the comparison of maximum peak overpressure generated with different blockage ratio and repeated obstacles rows. Description of the experimental setup includes all the details deemed necessary to reproduce the phenomenon with a CFD tool. • Experimental tests of hydrogen vented deflagration in a 25 m3 test facility. • Comparison of maximum peak overpressure with and without obstacles. • Comparison of maximum peak overpressure with different blockage ratio. • Comparison of maximum peak overpressure with repeated obstacles. • Comparison of maximum overpressure in homogeneous and non-homogeneous conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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7. 严重事故下氢气爆燃环境模拟试验.
- Author
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姜韶堃, 赵罗生, 杨志义, 詹惠安, 陶志勇, 赵 宁, and 丁 超
- Abstract
Copyright of Nuclear Safety is the property of Nuclear & Radiation Safety Center and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2020
8. Small scale experiments and Fe model validation of structural response during hydrogen vented deflagrations.
- Author
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Pini, T., Hanssen, A.Grønsund, Schiavetti, M., and Carcassi, M.
- Subjects
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MODEL validation , *HYDROGEN as fuel , *HYDROGEN , *DISPLACEMENT (Mechanics) , *MIXTURES , *DATA analysis - Abstract
Abstract University of Pisa (UNIPI) conducted a series of vented deflagration tests at B. Guerrini Laboratory. The tests were part of the experimental campaign performed by UNIPI for the European HySEA project (Hydrogen Safety for Energy Applications). Experiments included homogeneous hydrogen-air mixture contained in an about 1 m3 enclosure, called SSE (Small Scale Enclosure). The mixture concentration was variable between 10% and 18% vol. During the deflagrations, structural response was investigated by measuring the displacement of a test plate. The collected data were used to validate the FE model developed by IMPETUS Afea. In this paper experimental facility, displacement measurement system and FE model are briefly described, then comparison between experimental data and simulation results is discussed. Highlights • Experimental tests of hydrogen-air homogeneous mixture vented deflagration. • Experimental measurement of different test plates displacement. • Data analysis and discussion of experimental data collected during tests. • FE model set up and description. • Comparison between experimental data and FE model results. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
9. Non-homogeneous hydrogen deflagrations in small scale enclosure. Experimental results.
- Author
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Carcassi, M., Schiavetti, M., and Pini, T.
- Subjects
- *
HYDROGEN as fuel , *FUEL cells , *SMALL scale system , *PLASTIC sheets - Abstract
Abstract University of Pisa performed hydrogen releases and deflagrations in a 1.14 m3 test facility, which shape and dimensions resemble a gas cabinet. Tests were performed for the HySEA project, founded by the Fuel Cells and Hydrogen 2 Joint Undertaking with the aim to conduct pre-normative research on vented deflagrations in enclosures and containers used for hydrogen energy applications. The test facility, named Small Scale Enclosure (SSE), has a vent area of 0,42 m2 which can host different types of vent; plastic sheet and commercial vent were tested. Realistic levels of congestion are obtained placing a number of gas bottles inside the enclosure. Releases are performed from a buffer tank of a known volume filled with hydrogen at a pressure ranging between 15 and 60 bar. Two nozzles of different diameter and three different release directions were tested, being the nozzle placed at a height where in a real application a leak has the highest probability to occur. Three different ignition locations were investigated as well. This paper is aimed to summarize the main features of the experimental campaign as well as to present its results. Highlights • Experimental tests of hydrogen vented deflagration in a 1.14 m3 test facility. • Release from a pressurized buffer tank from a known diameter nozzle. • Effect of release direction, pressure, nozzle diameter and obstacles on the stratification. • Effect of the bottles, and the ignition location on the maximum achieved overpressure. • Study of the dynamic opening pressure of commercial vents. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
10. Combined effect of ignition position and equivalence ratio on the characteristics of premixed hydrogen/air deflagrations.
- Author
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Zheng, Ligang, Zhu, Xiaochao, Wang, Yalei, Li, Gang, Yu, Shuijun, Pei, Bei, Wang, Yan, and Wang, Wei
- Subjects
- *
SUPERCONDUCTIVITY , *HYDROGEN , *SPARK plugs , *COMBUSTION , *LASER plasmas - Abstract
Premixed hydrogen/air deflagrations were performed in a 100 mm × 100 mm × 1000 mm square duct closed at one end and opened at the opposite end under ambient conditions, concerning with the combined effect of ignition position IP and equivalence ratio ∅. A wide range of ∅ ranging from 0.4 to 5.0, as well as multiple IPs varying from 0 mm to 900 mm off the closed end of the duct were employed. It is indicated that IP and ∅ exerted a great impact on the flame structure, and the corresponding pressure built-up. Except for IP 0 , the flame can propagate in two directions, i.e., leftward and rightward. A regime diagram for tulip flames formation on the left flame front (LFF) was given in a plane of ∅ vs. IP. In certain cases (e.g. the combinations of ∅ = 0.6 and IP 500 or IP 700 ), distorted tulip flames were also observed on the right flame front (RFF). Furthermore, the combinations of IP and ∅ gave rise to various patterns of pressure profiles. The pressure profiles for ignition initiated at the right half part of the duct showed a weak dependence on equivalence ratio, and showed no dependence on ignition position. However, the pressure profiles for ignition initiated at the left half part of the duct were heavily dependent on the combination of IP and ∅. More specifically, in the leanest (∅ = 0.4) and the richest (∅ = 4.0–5.0) cases, intensive periodical oscillations were the prime feature of the pressure profiles. With the moderate equivalence ratios (∅ = 0.8–3.0), periodical pressure oscillations were only observed for IP 900 . The maximum pressure peaks P max were reached at ∅ = 1.25 rather than at the highest reactivity ∅ = 1.75 irrespective of ignition position. The ignition positions that produced the worst conditions were different, implying a complex influence of the combination of IP and ∅. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
11. Experimental tests of inhomogeneous hydrogen deflagrations in the presence of obstacles
- Author
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M. Schiavetti and Marco Nicola Mario Carcassi
- Subjects
Work (thermodynamics) ,Hydrogen ,Computer science ,Nuclear engineering ,Enclosure ,Measure (physics) ,Energy Engineering and Power Technology ,chemistry.chemical_element ,02 engineering and technology ,Computational fluid dynamics ,010402 general chemistry ,01 natural sciences ,Hydrogen deflagration ,Inhomogeneous mixtures ,Obstacles ,Dispersion (water waves) ,Renewable Energy, Sustainability and the Environment ,business.industry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Overpressure ,Fuel Technology ,chemistry ,Deflagration ,0210 nano-technology ,business - Abstract
Explosion venting is a frequently used measure to mitigate the outcome of deflagration in closed environments. Despite the effort to improve engineering formulas and CFD tools used to predict the vent area needed to meet the desired enclosure protection, work has still to be done to reliably predict the outcome of a vented gas explosion. Blind-prediction exercises recently published by the HYSEA project show a large spread in the predictions by engineering models, including semi-empirical correlations and computational fluid dynamics (CFD) tools. University of Pisa performed experimental tests in a 25 m3 facility in inhomogeneous conditions and with the presence of simple obstacles constituted by plates bolted to HEB beams. The present paper is aimed to share the results of hydrogen dispersion and deflagration tests and discuss the comparison of maximum peak overpressure generated with different blockage ratio and repeated obstacles rows. Description of the experimental setup includes all the details deemed necessary to reproduce the phenomenon with a CFD tool.
- Published
- 2021
- Full Text
- View/download PDF
12. The role of CFD combustion modelling in hydrogen safety management – VI: Validation for slow deflagration in homogeneous hydrogen-air-steam experiments.
- Author
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Cutrono Rakhimov, A., Visser, D.C., Holler, T., and Komen, E.M.J.
- Subjects
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COMPUTATIONAL fluid dynamics , *COMBUSTION , *HYDROGEN , *TURBULENCE , *DYNAMIC pressure , *SAFETY - Abstract
Large quantities of hydrogen can be generated during a severe accident in a water-cooled nuclear reactor. When released in the containment, the hydrogen can create a potential deflagration risk. The dynamic pressure loads resulting from hydrogen combustion can be detrimental to the structural integrity of the reactor. Therefore, accurate prediction of these pressure loads is an important safety issue. In previous papers, we validated a Computational Fluid Dynamics (CFD) based method to determine the pressure loads from a fast deflagration. The combustion model applied in the CFD method is based on the Turbulent Flame Speed Closure (TFC). In our last paper, we presented the extension of this combustion model, Extended Turbulent Flame Speed Closure (ETFC), and its validation against hydrogen deflagration experiments in the slow deflagration regime. During a severe accident, cooling water will enter the containment as steam. Therefore, the effect of steam on hydrogen deflagration is important to capture in a CFD model. The primary objectives of the present paper are to further validate the TFC and ETFC combustion models, and investigate their capability to predict the effect of steam. The peak pressures, the trends of the flame velocity, and the pressure rise with an increase in the initial steam dilution are captured reasonably well by both combustion models. In addition, the ETFC model appeared to be more robust to mesh resolution changes. The mean pressure rise is evaluated with 18% under-prediction and the peak pressure is evaluated with 5% accuracy, when steam is involved. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
13. Investigations of hydrogen hazard mitigation by deliberate ignition in small modular reactor during severe accident using GASFLOW-MPI.
- Author
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Wang, Fangnian, Zou, Zhiqiang, Deng, Jian, Qin, Huan, and Zhang, Ming
- Subjects
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HAZARD mitigation , *EXPLOSIONS , *WATER cooled reactors , *COMPUTATIONAL fluid dynamics , *HYDROGEN analysis , *HYDROGEN - Abstract
• Analysis methodology of hydrogen mitigation by ignitors is improved according to CFD features. • Code validation against the H2 flame propagation experiments shows good agreements. • Hydrogen 3D distribution and hazard mitigation by ignitors in SMR containment are investigated. • Hydrogen deflagration caused by accidental ignition could lead to containment pressure over design. Hydrogen explosion, which represents a complex safety issue in the water-cooled Small Modular Reactors (SMRs), could lead to over-pressurization and threaten the integrity of the reactor containment in case of severe accidents. In order to mitigate this hydrogen hazard, ignitors could be used as an option in SMRs by deliberately burning the hydrogen. Computational Fluid Dynamics (CFD) tool GASFLOW-MPI has been developed and validated to perform hydrogen safety analysis of the SMR with steel containment during severe accidents, including the hydrogen distribution, hydrogen explosion risk assessment, hydrogen removal by deliberate ignition and hydrogen combustion. The combustion models implemented in GASFLOW-MPI have been validated against the THAI-HD hydrogen deflagration experiments. The relevant analysis methodology is improved according to the GASFLOW-MPI features. The calculation results show that the ignitor system can effectively reduce the hydrogen and mitigate the hydrogen explosion risk. However, H 2 -air-steam mixtures could be inerted by the extremely high steam concentration near the ignitors. A large amount of hydrogen could be accumulated in containment, which will become flammable due to the condensation of steam. To study the consequences of the failure of the deliberate ignition, accidental ignitions at various locations are triggered in the SMR containment. Depending on the turbulence intensity and the geometrical complexity of the internal structures, a pressure peak higher than the design pressure occurs. It indicates that the capability of deliberate ignition system is restricted by the burnable limit of the mixtures. It seems that a combination of deliberate ignition system and passive hydrogen removal system is more preferable to eliminate the hydrogen risks in the SMR containment. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
14. Non-homogeneous hydrogen deflagrations in small scale enclosure. Experimental results
- Author
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Marco Nicola Mario Carcassi, T. Pini, and M. Schiavetti
- Subjects
Leak ,Hydrogen ,Nuclear engineering ,Nozzle ,Enclosure ,Energy Engineering and Power Technology ,chemistry.chemical_element ,02 engineering and technology ,7. Clean energy ,law.invention ,Pressurized release ,law ,0502 economics and business ,Gas cabinet ,Renewable Energy ,050207 economics ,Hydrogen stratification ,Sustainability and the Environment ,Renewable Energy, Sustainability and the Environment ,05 social sciences ,Hydrogen deflagration ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Ignition system ,Fuel Technology ,Volume (thermodynamics) ,chemistry ,Hydrogen fuel ,Environmental science ,0210 nano-technology - Abstract
University of Pisa performed hydrogen releases and deflagrations in a 1.14 m3 test facility, which shape and dimensions resemble a gas cabinet. Tests were performed for the HySEA project, founded by the Fuel Cells and Hydrogen 2 Joint Undertaking with the aim to conduct pre-normative research on vented deflagrations in enclosures and containers used for hydrogen energy applications. The test facility, named Small Scale Enclosure (SSE), has a vent area of 0,42 m2 which can host different types of vent; plastic sheet and commercial vent were tested. Realistic levels of congestion are obtained placing a number of gas bottles inside the enclosure. Releases are performed from a buffer tank of a known volume filled with hydrogen at a pressure ranging between 15 and 60 bar. Two nozzles of different diameter and three different release directions were tested, being the nozzle placed at a height where in a real application a leak has the highest probability to occur. Three different ignition locations were investigated as well. This paper is aimed to summarize the main features of the experimental campaign as well as to present its results.
- Published
- 2018
- Full Text
- View/download PDF
15. Start-up behavior and the ignition limit of passive hydrogen recombiners with various catalytic elements.
- Author
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Bezgodov, Evgenii, Davletchin, Yuriy, Kryukov, Vyacheslav, Moshkin, Dmitriy, Pasyukov, Sergei, Platonov, Evgenii, Popov, Ilya, Simonenko, Vadim, Tararykin, Aleksandr, and Ushkov, Aleksandr
- Subjects
- *
NATURAL heat convection , *HYDROGEN , *GAS mixtures - Abstract
For the first time, separate catalytic particles individually igniting the mixture have been observed (flame front contour is given in yellow). [Display omitted] The paper gives the results of experiments aimed to study start-up characteristics and the ignition limit of recombiners containing two various types of catalysts, namely ceramic rods and high porosity cell material. Both types of catalysts were produced by Redkino Catalyst Company. Experiments were carried out using a 15 m3 BM-P chamber located at the FSUE "RFNC-VNIITF named after Academ. E.I. Zababakhin" test site. The recombiner was tested in a homogeneous hydrogencontaining gas mixture under the quasi-stationary conditions with a stepwise increase in hydrogen concentration. Experimental results demonstrated that similar physical processes were observed for both types of catalysts. The recombiner was shown to start up when natural convection flow was activated through its case. Ignition was proved to be caused not only by a heated catalyst, but also by particles escaping from catalytic surface due to spallation and thus decreasing the ignition limit from 10% down to 5%. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
16. Experimental study of hydrogen release accidents in a vehicle garage
- Author
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Merilo, E.G., Groethe, M.A., Colton, J.D., and Chiba, S.
- Subjects
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RISK assessment , *HYDROGEN , *AUTOMOBILE repair shops , *GAS leakage , *IGNITION of gas appliances , *PLASTIC films , *VEHICLES , *VENTILATION , *THERMOCOUPLES - Abstract
Abstract: Storing a hydrogen fuel-cell vehicle in a garage poses a potential safety hazard because of the accidents that could arise from a hydrogen leak. A series of tests examined the risk involved with hydrogen releases and deflagrations in a structure built to simulate a one-car garage. The experiments involved igniting hydrogen gas that was released inside the structure and studying the effects of the deflagrations. The “garage” measured 2.72 m high, 3.64 m wide, and 6.10 m long internally and was constructed from steel using a reinforced design capable of withstanding a detonation. The front face of the garage was covered with a thin, transparent plastic film. Experiments were performed to investigate extended-duration (20–40 min) hydrogen leaks. The effect that the presence of a vehicle in the garage has on the deflagration was also studied. The experiments examined the effectiveness of different ventilation techniques at reducing the hydrogen concentration in the enclosure. Ventilation techniques included natural upper and lower openings and mechanical ventilation systems. A system of evacuated sampling bottles was used to measure hydrogen concentration throughout the garage prior to ignition, and at various times during the release. All experiments were documented with standard and infrared (IR) video. Flame front propagation was monitored with thermocouples. Pressures within the garage were measured by four pressure transducers mounted on the inside walls of the garage. Six free-field pressure transducers were used to measure the pressures outside the garage. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
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17. The role of CFD combustion modelling in hydrogen safety management – VIII: Use of Eddy Break-Up combustion models for simulation of large-scale hydrogen deflagration experiments.
- Author
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Holler, Tadej, Komen, Ed M.J., and Kljenak, Ivo
- Subjects
- *
COMBUSTION , *FLAME , *FLAME spread , *TRANSPORT equation , *HYDROGEN , *EDDIES , *SIMULATION methods & models - Abstract
• Three modifications of the Eddy Break-Up combustion model are considered: basic with Said-Borghi correction, extended to quasi-laminar flame propagation, and augmented with weighted laminar flame speed. • The models are assessed by simulating two upward flame propagation combustion experiments, performed in large-scale vessels of different volumes. • Differences between results, obtained with different models, are much larger in the wider vessel than in the narrower one. • The quasi-laminar term in the progress variable transport equation source term may exert considerable influence when simulating deflagration in large vessels. Hydrogen deflagration in experimental containment vessels is simulated by introducing a modified Eddy Break-Up model, with the aim to apply it for hydrogen combustion in containment vessels. First, an additional term is introduced in the source term of the progress variable (non-dimensional fuel concentration) transport equation to extend its applicability from the turbulent to the quasi-laminar flame propagation region. The model is then modified further by introducing the weighted laminar flame speed, which decreases the influence of this quasi-laminar term in the same equation. The models are assessed by simulating two experiments, performed in different large-scale facilities. Simulated axial and radial flame propagation, pressure and pressure increase rate, and flame shapes are compared to experimental results. The comparisons reveal that the model differences affect mostly the simulations in the wider vessel. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
18. Small scale experiments and Fe model validation of structural response during hydrogen vented deflagrations
- Author
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A.Grønsund Hanssen, T. Pini, M. Schiavetti, and Marco Nicola Mario Carcassi
- Subjects
Hydrogen ,Scale (ratio) ,Nuclear engineering ,0211 other engineering and technologies ,Enclosure ,chemistry.chemical_element ,Energy Engineering and Power Technology ,02 engineering and technology ,Hydrogen safety ,FE simulations ,11. Sustainability ,Renewable Energy ,Structural response ,Hydrogen deflagration ,021110 strategic, defence & security studies ,Sustainability and the Environment ,Renewable Energy, Sustainability and the Environment ,System of measurement ,Experimental data ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Fuel Technology ,chemistry ,Environmental science ,Deflagration ,0210 nano-technology ,Displacement (fluid) - Abstract
University of Pisa (UNIPI) conducted a series of vented deflagration tests at B. Guerrini Laboratory. The tests were part of the experimental campaign performed by UNIPI for the European HySEA project (Hydrogen Safety for Energy Applications). Experiments included homogeneous hydrogen-air mixture contained in an about 1 m3 enclosure, called SSE (Small Scale Enclosure). The mixture concentration was variable between 10% and 18% vol. During the deflagrations, structural response was investigated by measuring the displacement of a test plate. The collected data were used to validate the FE model developed by IMPETUS Afea. In this paper experimental facility, displacement measurement system and FE model are briefly described, then comparison between experimental data and simulation results is discussed.
- Published
- 2019
- Full Text
- View/download PDF
19. GOTHIC simulations of OECD/NEA THAI multi-vessel hydrogen deflagration tests.
- Author
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Lebel, Luke and Liang, Zhe
- Subjects
- *
FLAME stability , *FORCED convection , *HYDROGEN analysis , *HYDROGEN , *FLAME - Abstract
• GOTHIC simulation of hydrogen deflagrations in the THAI vessel. • Deflagration in single or multiple volumes under quiescent or turbulent environments. • Application of a global burn enhancement factor to account for flame instabilities. This paper presents GOTHIC analyses of hydrogen deflagration tests performed in the framework of the OECD/NEA THAI program. The experiments were performed in one or two interconnected vessels under similar conditions, including cases with forced convection loops and both upward- and downward-propagating burns. To capture the influence of initial turbulence and flame wrinkling, a global burn enhancement factor was employed in the calculations. The simulations captured the overall propagation of the hydrogen burns and the pressurization rate. Overall agreement was reasonably good for the upward-propagating flames, but some dynamics in the second interconnected vessel were more challenging for GOTHIC to replicate, as the flame propagation speed was generally over-predicted with the global burn enhancement model. The benchmark exercise has helped to better understand the requirements for modeling hydrogen deflagrations in multiple interconnected volumes with initial turbulence, and can be used to improve guidance on hydrogen issues in nuclear safety analysis. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
20. Analyses of THAI 1 hydrogen deflagration using MELCOR code version 2.1 and 2.2.
- Author
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Flores y Flores, A. and Mazzini, G.
- Subjects
- *
NUCLEAR energy , *HYDROGEN , *NUCLEAR power plants , *EXPLOSIONS , *FISSION products - Abstract
• Modelling and Simulation of two experiments using MELCOR code version 2.1 and version 2.2. • Benchmarking of the MELCOR code. Code-Experiment and Code-to-Code (different versions). • Assess of the MELCOR code capabilities to modelling and simulate hydrogen deflagration scenarios. The Fukushima Daiichi NPP (Nuclear Power Plant) accident pointed out the hydrogen explosion issue as one of the main problems that can affect the NPP containment integrity. During a severe accident scenario, the hydrogen combustion can occur and lead to containment integrity failure, since it generates local and global pressure and heat spikes. Such topic was analysed in several research programs addressed all around the world. An important series of test campaigns was done in OECD/NEA WGAMA (Organisation for Economic Co-operation and Development/Nuclear Energy Agency Working Group on Analysis and Management of Accidents) program called THAI (Thermal-hydraulics, Hydrogen, Aerosol and Iodine). The THAI goal is to simulate several phenomena related on hydrogen and Fission Product behaviour in the containment to obtain data relevant for the code benchmarking and validation. Therefore, theoretical analyses are needed, in order to obtain a reliable prediction of the accidental scenario. The facility allows to investigate safety relevant effects under thermal-hydraulics conditions of severe accidents. The experiments performed cover from hydrogen deflagration to iodine and aerosol behaviour under different thermal-hydraulics conditions. Three representative experiments were chosen from the THAI campaign to be modeled and simulated using the MELCOR code with versions 2.1 and 2.2 and compare the results with the experimental ones. This work aims to assess the MELCOR code capability pointing out on the limitation in simulating the hydrogen deflagration and underling possible method to reduce their effect on the simulate results. The benchmarks were addressed with old version of MELCOR however the new version presented slightly different results due to the modification in the parametric model and the default sensitivity coefficients. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
21. A study on the scaling features for mixing and deflagration potential of stratified layer of hydrogen due to molecular diffusion
- Author
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Sarit K. Das, Nilesh Agrawal, and K. Velusamy
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Diffusion in liquids ,Materials science ,General Chemical Engineering ,Combustion ,Thermodynamics ,Hydrogen safety ,symbols.namesake ,Flammability ,Mixing ,Diffusion in solids ,Mitigation measures ,Diffusion (business) ,Scaling ,Confined space ,Molecular diffusion ,Accident investigation ,Hydrogen deflagration ,Mechanics ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Deflagration ,Fourier number ,Enclosures ,Accidents ,Volume fraction ,symbols ,Long term behaviours ,Temporal information ,Hydrogen - Abstract
Hydrogen deflagration in confined spaces is an important safety issue. The dispersion of a stratified layer of hydrogen due to molecular diffusion is studied. It represents an important class of problems related to long term behaviour of hydrogen release in confined spaces. Diffusion being a slow process, gives an upper bound on the time taken for the stratified layer to mix with air below. A method, based on four indices, namely, average mole fraction (of hydrogen), non-uniformity index, deflagration volume fraction and deflagration pressure ratio, developed recently by the authors, is used to provide vital temporal information on mixing of the stratified layer with air below and formation of flammable cloud in the enclosure. In the present paper, stratified layers of different thickness are considered and the temporal evolutions of the above indices are plotted against diffusion Fourier number. The results in non-dimensional form provide an upper bound of the time that would be required to form a uniform mixture and to attain a state with respect to deflagration potential for enclosures of different sizes. This estimate is an important input for planning mitigation measures before the accident and for post accident investigations. � 2013 Elsevier Ltd.
- Published
- 2013
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22. Combustion Characteristics for Non-homogeneous Segregated H2-Air Mixtures
- Author
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Manoubi, Maha
- Subjects
Physics::Fluid Dynamics ,Non-homogeneous media ,Flame propagation ,Hydrogen deflagration ,Physics::Chemical Physics ,Soap bubble ,Spherical flame - Abstract
The work presented in this thesis is an investigation of the dynamics of unconfined hydrogen-air flames in the presence of buoyant effects and the determination of an ignition criterion for flame propagation between adjacent pockets of reactive gas separated by air. The experimental work was conducted using the soap bubble technique and visualized with high speed schlieren or large scale shadowgraph systems. A study was first conducted to determine the most suitable soap solution additive among glycerol, guar and polyethylene oxide for conducting the experiments, isolating guar as the best candidate. The soap solution was then used to study the dynamics of flames in single or multiple soap bubbles filled with reactive mixtures of different compositions. The soap bubble method was also further improved by designing a soap dispenser that can maintain a bubble indefinitely and a method to burst the soap solution prior to an experiment using timed heated wires. In the experiments with single bubbles, it was found that for sufficiently lean hydrogen-air mixtures, buoyancy effects become important at small scales. The critical radius of hemispherical flames that will rise due to buoyancy was measured and estimated using a model comparing the characteristic burning speed and the rise speed of the flame kernel. Excellent agreement was found between the model predictions and the measured critical flame radii. The experiments with multiple bubbles provided the scaling rules for flame transition between neighboring pockets of hemispherical or spherical shape separated by an inert gas. The test results demonstrated that the separation distance between the bubbles is mainly determined by the expansion ratio when the buoyancy effects are negligible, corresponding to near stoichiometric mixtures. For leaner mixtures with stronger buoyant effects, the critical separation distance was no longer governed by the expansion ratio alone, as buoyancy forces render the flame propagation across the inert gas more difficult. Visualization of the ignition dynamics confirmed that buoyancy forces tend to accelerate the first kernel up before ignition of the second kernel can be achieved.
- Published
- 2015
- Full Text
- View/download PDF
23. An intercomparison exercise on the capabilities of CFD models to reproduce a large-scale hydrogen deflagration in open atmosphere
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Open atmosphere ,Defence ,Intercomparison exercise ,Explosions ,Experimental data ,Hydrogen deflagration ,Hydrogen safety ,Deflagration ,Flame speed ,Simulation result ,Statistical analysis ,Combustion modeling ,Hydrogen-air mixture ,Rate of pressure ,Explosives ,Maximum pressure ,CFD ,Hydrogen ,CFD models - Abstract
Within the HySafe Network of Excellence, several organizations with experience in numerical combustion modeling participated to Standard Benchmark Exercise Problem 2 (SBEP-V2), trying to reproduce numerically the explosion of a stoichiometric hydrogen-air mixture in a 10 m radius balloon. Different codes and models have been applied in the validation exercise. The simulation results and experimental data for the flame speed, the maximum pressures, the rate of pressure rise and the maximum impulse are discussed and compared by means of statistical analysis. An overall satisfactory agreement for the flame speed and maximum pressure is found. © 2010 Professor T. Nejat Veziroglu.
- Published
- 2010
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