Journal of Loss Prevention in The Process Industries, Feb 1, 2023
Previous works (Daubech, Lecocq, 2019) were dedicated to gaseous flame acceleration along long pi... more Previous works (Daubech, Lecocq, 2019) were dedicated to gaseous flame acceleration along long pipes with a set of cases studied both experimentally and numerically. In these cases, the flammable mixture was initially quiescent and homogenously distributed. The impact of the tube diameter and material were studied trough both approaches for rather slow flames, the fuel being methane. While main features of the real flame were recovered by the chosen CFD method, some limits remained. A new experimental dataset is detailed and analyzed with a quicker flame, the fuel being hydrogen and the same experimental set-up as the one used for measuring slow flames. Thus, the fuel effect on the flame dynamics can be directly highlighted. A simple CFD approach is tested for recovering two distinct flame behaviors: a deflagration flame and another undergoing deflagration-to-detonation transition. Furthermore, the modelling results are used to propose elements of interpretation for flame acceleration.
GDF SUEZ, as a gas and LNG company, operates onshore and offshore facilities where accidental hig... more GDF SUEZ, as a gas and LNG company, operates onshore and offshore facilities where accidental high pressure releases of natural gas are likely to occur. To study this hazard, experiments have been performed in uncongested areas, focusing on fires and heat flux. In parallel, trials were carried out to assess overpressures generated by a gas explosion in a congested area. Most experiments were done with a quiescent stoichiometric gas cloud and not with a real turbulent release of methane or natural gas. The same assumption of stoichiometric gas cloud is then followed for quantitative risk assessment and influence land use planning, occupational safety, safety gaps definition and design. The following review endeavours to collect existing knowledge and recent experimental and numerical works on the influence of initial turbulence on methane explosions severity and to highlight the differences between explosions with initial turbulence and explosions with quiescent stoichiometric mixtur...
International audienceSince a few years, hydrogen appears as a practical energy vector and some h... more International audienceSince a few years, hydrogen appears as a practical energy vector and some hydrogen applications are already on the market. However these applications are still considered dangerous, hazardous events like explosion could occur and some accidents, like the Hindenburg disaster, are still in the mind. Objectively, hydrogen ignites easily and explodes violently. Safety engineering has to be particularly strong and demonstrative; a method of precise identification of accidental scenarios (“probabilities”; “severity”) is developed in this article. This method, derived from ARAMIS method, permits to identify and to estimate the most relevant safety barriers and therefore helps future users choose appropriate safety strategies
International audienceDelayed explosion of free field hydrogen releases at a high pressure is sub... more International audienceDelayed explosion of free field hydrogen releases at a high pressure is subject of multiple investigation performed by various authors in the past years. These studied considered various parameters such as pressures, flow rates etc., and their influence on the resulting overpressure. However, the influence of the ignition position on the maximum overpressure was not fully explored. Current investigation addressed by computational fluid dynamics (CFD) simulations and experimental measurement fills this gap. This work demonstrates that the ignition positions corresponding to 55%-65% of H2/air mixture give the maximum overpressure. This observation initially observed numerically and afterword confirmed experimentally. A simple model is also suggested
International audienceIf Hydrogen is expected to be highly valuable, some improvements should be ... more International audienceIf Hydrogen is expected to be highly valuable, some improvements should be conducted, mainly regarding the storage safety. To prevent from high pressure hydrogen composite tanks bursting, the comprehension of the thermo-mechanics phenomena in the case of fire should be improved. To understand the kinetic of strength loss, the heat flux produced by fire of various intensities should be assessed. This is the objective of this real scale experimental campaign, which will allow studying in future works, the strength loss of composite high-pressure vessels in similar fire conditions to the ones determined in this study. Fire calibration tests were performed on metallic cylinder vessels. These tests with metallic cylinders are critical in the characterization of the thermal load of various fire sources (pool fire, propane gas fire, hydrogen gas fire) so as to evaluate differences related to different thermal load. Radiant panels were also used as thermal source for r...
AIChE Spring Meeting 2007 & 3. Global Congress on Process Safety & 41. Loss Prevention Symposium, Apr 22, 2007
International audienceUsing numerical modelling is a "natural" step in today's engi... more International audienceUsing numerical modelling is a "natural" step in today's engineering work, even in safety. Up to a certain extent, solving more or less accurately the basic Navier-stokes equations has replaced the traditional analytical approximate solutions of the same equations. Doing this, we surely have gained in flexibility, sometimes in accuracy, but we may have lost in expertise and ergonomics. In this paper, different modelling ways are set in perspective for the specific case of explosions, trying to link them to a specific area. It is the opinion of the present authors that simple physical "modelling" is justified in areas where a consensus is required on "basic " approaches as for standards, that complex numerical modelling is particularly fruitful in research and that some intermediate "phenomenological" modelling is possible and proves profitable for process safety where some technical expertise is required. Example of such tools are given and compared to existing data
Accidental gas explosions represent an ever-present hazard for process industries handling flamma... more Accidental gas explosions represent an ever-present hazard for process industries handling flammable gases and liquids. There is also an increasing danger of vandals and terrorists using improvised explosive devices in industrial areas neighboring highly populated residential areas. The consecutive pressure wave generation and propagation can result in unacceptable risk exposition of citizens and infrastructures. Therefore, it is necessary to define design rules of protective barriers mitigating the effect of blast wave.
The use of hydrogen as an energy carrier is a real perspective in Europe since a number of breakt... more The use of hydrogen as an energy carrier is a real perspective in Europe since a number of breakthroughs obtained in the last decades open the possibility to envision a deployment at the industrial scale if safety issues are duly accounted. However, on this particular aspects, experimental data are still lacking especially about the explosion dynamics in realistic dimensions. The purpose of this paper is to provide a set of totally new and well instrumented hydrogen - air vented explosions. Experiments were performed in a large explosion chamber within the scope of the DIMITRHY project (sponsored by the National French Agency for Research). The 4 m3 rectangular experimental chamber (2 m height, 2 m width and 1 m depth) is equipped with transparent walls and is vented (0.25 and 0.5 m2 square vents).. Six pressure gauges were used to measure the overpressure evolution inside and outside the chamber. Six concentration gauges were used to control the hydrogen repartition in the vessel. ...
To define a strategy of mitigation for containerized hydrogen systems (fuel cells for example) ag... more To define a strategy of mitigation for containerized hydrogen systems (fuel cells for example) against explosion, the main characteristics of flammable atmosphere (size, concentration, turbulence...) shall be well-known. This article presents an experimental study on accidental hydrogen releases and dispersion into an enclosure of 4 m (2 m x 2 m x 1 m). Different release points are studied: two circular releases of 1 and 3 mm and a system to create ring-shaped releases. The releases are operated with a pressure between 10 and 40 bars in order to be close to the process conditions. Different positions of the release inside the enclosure i.e. centred on the floor or along a wall are also studied. A specific effort is made to characterize the turbulence in the enclosure during the releases. The objectives of the experimental study are to understand and quantify the mechanisms of formation of the explosive atmosphere taking into account the geometry and position of the release point and...
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific r... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Ingénierie de la sécurité appliquée à des applications hydrogène-énergie Audrey Duclos, Christophe Proust, Jérôme Daubech, Franck Verbecke
L'explosion a eu lieu le 11 decembre 2005 vers 6h30 sur le depot petrolier de Buncefield. Le ... more L'explosion a eu lieu le 11 decembre 2005 vers 6h30 sur le depot petrolier de Buncefield. Le debordement par le toit d'un bac d'essence entraine le deversement de 180 tonnes d'essence qui parvient a s'echapper de la cuvette de retention. Ce deversement s'accompagne de la formation d'un aerosol et d'une nappe de liquide s'evaporant sur une grande surface. L'atmosphere est tres stable avec une vitesse de vent inferieure a 1 m/s. La surface au sol du nuage inflammable a ete estimee a 120 000 m2, soit environ un rayon de 200 m autour du point de fuite. La hauteur estimee du nuage est de l'ordre de quelques metres. Les temoignages, des elements visuels (video surveillance) et l'examen de la chronologie des evenements suggerent fortement que l'inflammation aurait eu lieu dans la pomperie incendie adjacente au reservoir " fuyard " au moment du demarrage des pompes. L'environnement dans lequel se developpe l'explosion est...
Les explosions sont des phenomenes particulierement complexes a la croisee de disciplines diffici... more Les explosions sont des phenomenes particulierement complexes a la croisee de disciplines difficiles comme la chimie de la combustion, la mecanique des interfaces (les flammes), la mecanique des fluides transitoire et compressible... Le recours a des codes numeriques destines a la resolution des equations fondamentales semble a priori une perspective raisonnable initiee, pour le domaine considere, voici une trentaine d'annee. Il existe aujourd'hui quelques logiciels (de type " CFD ") dont plusieurs sont accessibles (FLUENT, FLACS, AUTOREAGAS,...). Quelques exercices d'intercomparaison ou de confrontation a des experiences " realistes " ont ete realises qui temoignent d'une grande disparite des performances et suggerent que la predictivite n'est pas assuree et que les incertitudes ne sont guere maitrisees. Devant cette situation (qui perdure depuis 20 ans), de grands instituts nationaux, comme HSL en Grande-Bretagne, suggerent que les codes CFD...
The use of hydrogen as an energy carrier is a real perspective for Europe since a number of break... more The use of hydrogen as an energy carrier is a real perspective for Europe since a number of breakthroughs now enable to envision a deployment at the industrial scale. However some safety issues need to be further addressed but experimental data are still lacking especially about the explosion dynamics in realistic dimensions. A set of hydrogen-air vented explosions were thus performed in two medium scale chambers (1m3 and 10m3). Homogeneous mixtures were used (10% to 30% vol.). The explosion overpressure was measured inside the chamber and outside on the axis of the discharge from the vent. The incidence of the external explosion is clearly seen. All the results in this paper and the predictions from the standards differ greatly meaning that a significant effort is still required. It is the purpose of the French project DIMITRHY to help progressing.
Turbulence is a key aspect in hydrogen explosions. U fortunately, only limited experimental data ... more Turbulence is a key aspect in hydrogen explosions. U fortunately, only limited experimental data is available and the current understanding of flame tu rbulence interactions is too limited to permit safe predictions. New experimental data are presented in which the flame trajectory and pressure history are interpreted for unconfined explosions of H2/O2/ N2 clouds of 7 m. The intensity of the turbulence is varied between 0 and 5 m/s and the integral scal e of the turbulence is on the order of 10 cm which is at least an order of magnitude larger than lab scal e.
This document describes and presents the results of a pneumatic bursting test of a CORNING AFR G4... more This document describes and presents the results of a pneumatic bursting test of a CORNING AFR G4 industrial silicon carbon reactor performed at INERIS in France. The reactor burst beyond 150 bar, well above its design pressure of 18 bar. The kinetic energy of fragments ejected during the bursting and the pressure effects were measured. The observed effects are below the minimum levels of significant injury for human body.
Explosion modelling tools improved significantly during the last thirty years. They become steadi... more Explosion modelling tools improved significantly during the last thirty years. They become steadily more and more predictive but often important simplifications are made such as assuming a homogeneous combustible cloud. In real situations, heterogeneities exist. For instance, turbulent jets, induced by massive leaks, are characterised by a much larger concentration near the breach than further downstream. As explosion effects are linked to the history of the flame through the cloud, a reactivity gradient may modify significantly the pressure evolution, maximum levels reached and impulse [1] .The purpose of this work is to evaluate the influence of a reactivity gradient of combustible cloud upon the subsequent perturbations of explosion effects.
Journal of Loss Prevention in the Process Industries, 2022
The case of a gas explosion occurring in a geometrically simple enclosure, equipped with a vent i... more The case of a gas explosion occurring in a geometrically simple enclosure, equipped with a vent is considered. It is well known in the gas explosion scientific community that the calculation of the reduced explosion overpressure, determinant in safety studies, is not trivial. Not only there is a strong dependency on the chemical kinetics of the combustible but also on the enclosure geometry, the fluid flow, the vent mechanical behaviour, shape, etc… As a result, the modelling of the physics at stake is challenging, a wide range of models are proposed in the scientific literature and this reference situation is still the object of extensive research. A new simulation approach ignoring a large part of the underlying physics is investigated. It is based on the use of an artificial neural network (ANN). The focus is given on the method of use and results obtained with the ANN rather than on the neural network itself. Our observations are discussed within the scope of industrial safety problems. Calculations performed with the relatively simple ANN proposed in the official TensorFlow tutorial, on a vented explosion database containing 268 tests, led to surprisingly good results considering the ANN implementation efforts. The tool might look promising but is also far from being as trivial as it seems at a first glance: not only the results of simulations obtained with this type of model must be examined with the greatest care but also the initial data base must be very well controlled. Routes are proposed to enhance the initial database and perform relevant analyses of the neural network predictions.
Journal of Loss Prevention in the Process Industries, 2019
This paper is the second part of a global work investigating the physics of premixed flame propag... more This paper is the second part of a global work investigating the physics of premixed flame propagation in several kinds of long pipes. It focuses on the potential of CFD for modelling such cases and on the key issues for being able to address generic cases. Four tests among the database detailed in the first part are selected. In each case, the pipe is straight, open at one end and closed at the other where ignition is triggered. The pipe is filled with a stoichiometric methane/air mixture at rest. Varied parameters are the inner pipe diameter and the pipe material. CFD computations, based on a URANS framework were carried out and enabled to recover several physical trends, such as the role of acoustics and boundary layer turbulence on the flame dynamics. Although most overpressure peaks orders of magnitude of the measured overpressure signals can be predicted numerically, the computed flames are quicker than the measured ones. It could be explained by the chosen turbulent model, the k-ω SST model, known to be adapted for wall-bounded flows but producing too much turbulence for accelerating flows. The criterion for the near wall cells (y + <200) might be too loose as well.
Journal of Loss Prevention in The Process Industries, Feb 1, 2023
Previous works (Daubech, Lecocq, 2019) were dedicated to gaseous flame acceleration along long pi... more Previous works (Daubech, Lecocq, 2019) were dedicated to gaseous flame acceleration along long pipes with a set of cases studied both experimentally and numerically. In these cases, the flammable mixture was initially quiescent and homogenously distributed. The impact of the tube diameter and material were studied trough both approaches for rather slow flames, the fuel being methane. While main features of the real flame were recovered by the chosen CFD method, some limits remained. A new experimental dataset is detailed and analyzed with a quicker flame, the fuel being hydrogen and the same experimental set-up as the one used for measuring slow flames. Thus, the fuel effect on the flame dynamics can be directly highlighted. A simple CFD approach is tested for recovering two distinct flame behaviors: a deflagration flame and another undergoing deflagration-to-detonation transition. Furthermore, the modelling results are used to propose elements of interpretation for flame acceleration.
GDF SUEZ, as a gas and LNG company, operates onshore and offshore facilities where accidental hig... more GDF SUEZ, as a gas and LNG company, operates onshore and offshore facilities where accidental high pressure releases of natural gas are likely to occur. To study this hazard, experiments have been performed in uncongested areas, focusing on fires and heat flux. In parallel, trials were carried out to assess overpressures generated by a gas explosion in a congested area. Most experiments were done with a quiescent stoichiometric gas cloud and not with a real turbulent release of methane or natural gas. The same assumption of stoichiometric gas cloud is then followed for quantitative risk assessment and influence land use planning, occupational safety, safety gaps definition and design. The following review endeavours to collect existing knowledge and recent experimental and numerical works on the influence of initial turbulence on methane explosions severity and to highlight the differences between explosions with initial turbulence and explosions with quiescent stoichiometric mixtur...
International audienceSince a few years, hydrogen appears as a practical energy vector and some h... more International audienceSince a few years, hydrogen appears as a practical energy vector and some hydrogen applications are already on the market. However these applications are still considered dangerous, hazardous events like explosion could occur and some accidents, like the Hindenburg disaster, are still in the mind. Objectively, hydrogen ignites easily and explodes violently. Safety engineering has to be particularly strong and demonstrative; a method of precise identification of accidental scenarios (“probabilities”; “severity”) is developed in this article. This method, derived from ARAMIS method, permits to identify and to estimate the most relevant safety barriers and therefore helps future users choose appropriate safety strategies
International audienceDelayed explosion of free field hydrogen releases at a high pressure is sub... more International audienceDelayed explosion of free field hydrogen releases at a high pressure is subject of multiple investigation performed by various authors in the past years. These studied considered various parameters such as pressures, flow rates etc., and their influence on the resulting overpressure. However, the influence of the ignition position on the maximum overpressure was not fully explored. Current investigation addressed by computational fluid dynamics (CFD) simulations and experimental measurement fills this gap. This work demonstrates that the ignition positions corresponding to 55%-65% of H2/air mixture give the maximum overpressure. This observation initially observed numerically and afterword confirmed experimentally. A simple model is also suggested
International audienceIf Hydrogen is expected to be highly valuable, some improvements should be ... more International audienceIf Hydrogen is expected to be highly valuable, some improvements should be conducted, mainly regarding the storage safety. To prevent from high pressure hydrogen composite tanks bursting, the comprehension of the thermo-mechanics phenomena in the case of fire should be improved. To understand the kinetic of strength loss, the heat flux produced by fire of various intensities should be assessed. This is the objective of this real scale experimental campaign, which will allow studying in future works, the strength loss of composite high-pressure vessels in similar fire conditions to the ones determined in this study. Fire calibration tests were performed on metallic cylinder vessels. These tests with metallic cylinders are critical in the characterization of the thermal load of various fire sources (pool fire, propane gas fire, hydrogen gas fire) so as to evaluate differences related to different thermal load. Radiant panels were also used as thermal source for r...
AIChE Spring Meeting 2007 & 3. Global Congress on Process Safety & 41. Loss Prevention Symposium, Apr 22, 2007
International audienceUsing numerical modelling is a "natural" step in today's engi... more International audienceUsing numerical modelling is a "natural" step in today's engineering work, even in safety. Up to a certain extent, solving more or less accurately the basic Navier-stokes equations has replaced the traditional analytical approximate solutions of the same equations. Doing this, we surely have gained in flexibility, sometimes in accuracy, but we may have lost in expertise and ergonomics. In this paper, different modelling ways are set in perspective for the specific case of explosions, trying to link them to a specific area. It is the opinion of the present authors that simple physical "modelling" is justified in areas where a consensus is required on "basic " approaches as for standards, that complex numerical modelling is particularly fruitful in research and that some intermediate "phenomenological" modelling is possible and proves profitable for process safety where some technical expertise is required. Example of such tools are given and compared to existing data
Accidental gas explosions represent an ever-present hazard for process industries handling flamma... more Accidental gas explosions represent an ever-present hazard for process industries handling flammable gases and liquids. There is also an increasing danger of vandals and terrorists using improvised explosive devices in industrial areas neighboring highly populated residential areas. The consecutive pressure wave generation and propagation can result in unacceptable risk exposition of citizens and infrastructures. Therefore, it is necessary to define design rules of protective barriers mitigating the effect of blast wave.
The use of hydrogen as an energy carrier is a real perspective in Europe since a number of breakt... more The use of hydrogen as an energy carrier is a real perspective in Europe since a number of breakthroughs obtained in the last decades open the possibility to envision a deployment at the industrial scale if safety issues are duly accounted. However, on this particular aspects, experimental data are still lacking especially about the explosion dynamics in realistic dimensions. The purpose of this paper is to provide a set of totally new and well instrumented hydrogen - air vented explosions. Experiments were performed in a large explosion chamber within the scope of the DIMITRHY project (sponsored by the National French Agency for Research). The 4 m3 rectangular experimental chamber (2 m height, 2 m width and 1 m depth) is equipped with transparent walls and is vented (0.25 and 0.5 m2 square vents).. Six pressure gauges were used to measure the overpressure evolution inside and outside the chamber. Six concentration gauges were used to control the hydrogen repartition in the vessel. ...
To define a strategy of mitigation for containerized hydrogen systems (fuel cells for example) ag... more To define a strategy of mitigation for containerized hydrogen systems (fuel cells for example) against explosion, the main characteristics of flammable atmosphere (size, concentration, turbulence...) shall be well-known. This article presents an experimental study on accidental hydrogen releases and dispersion into an enclosure of 4 m (2 m x 2 m x 1 m). Different release points are studied: two circular releases of 1 and 3 mm and a system to create ring-shaped releases. The releases are operated with a pressure between 10 and 40 bars in order to be close to the process conditions. Different positions of the release inside the enclosure i.e. centred on the floor or along a wall are also studied. A specific effort is made to characterize the turbulence in the enclosure during the releases. The objectives of the experimental study are to understand and quantify the mechanisms of formation of the explosive atmosphere taking into account the geometry and position of the release point and...
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific r... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Ingénierie de la sécurité appliquée à des applications hydrogène-énergie Audrey Duclos, Christophe Proust, Jérôme Daubech, Franck Verbecke
L'explosion a eu lieu le 11 decembre 2005 vers 6h30 sur le depot petrolier de Buncefield. Le ... more L'explosion a eu lieu le 11 decembre 2005 vers 6h30 sur le depot petrolier de Buncefield. Le debordement par le toit d'un bac d'essence entraine le deversement de 180 tonnes d'essence qui parvient a s'echapper de la cuvette de retention. Ce deversement s'accompagne de la formation d'un aerosol et d'une nappe de liquide s'evaporant sur une grande surface. L'atmosphere est tres stable avec une vitesse de vent inferieure a 1 m/s. La surface au sol du nuage inflammable a ete estimee a 120 000 m2, soit environ un rayon de 200 m autour du point de fuite. La hauteur estimee du nuage est de l'ordre de quelques metres. Les temoignages, des elements visuels (video surveillance) et l'examen de la chronologie des evenements suggerent fortement que l'inflammation aurait eu lieu dans la pomperie incendie adjacente au reservoir " fuyard " au moment du demarrage des pompes. L'environnement dans lequel se developpe l'explosion est...
Les explosions sont des phenomenes particulierement complexes a la croisee de disciplines diffici... more Les explosions sont des phenomenes particulierement complexes a la croisee de disciplines difficiles comme la chimie de la combustion, la mecanique des interfaces (les flammes), la mecanique des fluides transitoire et compressible... Le recours a des codes numeriques destines a la resolution des equations fondamentales semble a priori une perspective raisonnable initiee, pour le domaine considere, voici une trentaine d'annee. Il existe aujourd'hui quelques logiciels (de type " CFD ") dont plusieurs sont accessibles (FLUENT, FLACS, AUTOREAGAS,...). Quelques exercices d'intercomparaison ou de confrontation a des experiences " realistes " ont ete realises qui temoignent d'une grande disparite des performances et suggerent que la predictivite n'est pas assuree et que les incertitudes ne sont guere maitrisees. Devant cette situation (qui perdure depuis 20 ans), de grands instituts nationaux, comme HSL en Grande-Bretagne, suggerent que les codes CFD...
The use of hydrogen as an energy carrier is a real perspective for Europe since a number of break... more The use of hydrogen as an energy carrier is a real perspective for Europe since a number of breakthroughs now enable to envision a deployment at the industrial scale. However some safety issues need to be further addressed but experimental data are still lacking especially about the explosion dynamics in realistic dimensions. A set of hydrogen-air vented explosions were thus performed in two medium scale chambers (1m3 and 10m3). Homogeneous mixtures were used (10% to 30% vol.). The explosion overpressure was measured inside the chamber and outside on the axis of the discharge from the vent. The incidence of the external explosion is clearly seen. All the results in this paper and the predictions from the standards differ greatly meaning that a significant effort is still required. It is the purpose of the French project DIMITRHY to help progressing.
Turbulence is a key aspect in hydrogen explosions. U fortunately, only limited experimental data ... more Turbulence is a key aspect in hydrogen explosions. U fortunately, only limited experimental data is available and the current understanding of flame tu rbulence interactions is too limited to permit safe predictions. New experimental data are presented in which the flame trajectory and pressure history are interpreted for unconfined explosions of H2/O2/ N2 clouds of 7 m. The intensity of the turbulence is varied between 0 and 5 m/s and the integral scal e of the turbulence is on the order of 10 cm which is at least an order of magnitude larger than lab scal e.
This document describes and presents the results of a pneumatic bursting test of a CORNING AFR G4... more This document describes and presents the results of a pneumatic bursting test of a CORNING AFR G4 industrial silicon carbon reactor performed at INERIS in France. The reactor burst beyond 150 bar, well above its design pressure of 18 bar. The kinetic energy of fragments ejected during the bursting and the pressure effects were measured. The observed effects are below the minimum levels of significant injury for human body.
Explosion modelling tools improved significantly during the last thirty years. They become steadi... more Explosion modelling tools improved significantly during the last thirty years. They become steadily more and more predictive but often important simplifications are made such as assuming a homogeneous combustible cloud. In real situations, heterogeneities exist. For instance, turbulent jets, induced by massive leaks, are characterised by a much larger concentration near the breach than further downstream. As explosion effects are linked to the history of the flame through the cloud, a reactivity gradient may modify significantly the pressure evolution, maximum levels reached and impulse [1] .The purpose of this work is to evaluate the influence of a reactivity gradient of combustible cloud upon the subsequent perturbations of explosion effects.
Journal of Loss Prevention in the Process Industries, 2022
The case of a gas explosion occurring in a geometrically simple enclosure, equipped with a vent i... more The case of a gas explosion occurring in a geometrically simple enclosure, equipped with a vent is considered. It is well known in the gas explosion scientific community that the calculation of the reduced explosion overpressure, determinant in safety studies, is not trivial. Not only there is a strong dependency on the chemical kinetics of the combustible but also on the enclosure geometry, the fluid flow, the vent mechanical behaviour, shape, etc… As a result, the modelling of the physics at stake is challenging, a wide range of models are proposed in the scientific literature and this reference situation is still the object of extensive research. A new simulation approach ignoring a large part of the underlying physics is investigated. It is based on the use of an artificial neural network (ANN). The focus is given on the method of use and results obtained with the ANN rather than on the neural network itself. Our observations are discussed within the scope of industrial safety problems. Calculations performed with the relatively simple ANN proposed in the official TensorFlow tutorial, on a vented explosion database containing 268 tests, led to surprisingly good results considering the ANN implementation efforts. The tool might look promising but is also far from being as trivial as it seems at a first glance: not only the results of simulations obtained with this type of model must be examined with the greatest care but also the initial data base must be very well controlled. Routes are proposed to enhance the initial database and perform relevant analyses of the neural network predictions.
Journal of Loss Prevention in the Process Industries, 2019
This paper is the second part of a global work investigating the physics of premixed flame propag... more This paper is the second part of a global work investigating the physics of premixed flame propagation in several kinds of long pipes. It focuses on the potential of CFD for modelling such cases and on the key issues for being able to address generic cases. Four tests among the database detailed in the first part are selected. In each case, the pipe is straight, open at one end and closed at the other where ignition is triggered. The pipe is filled with a stoichiometric methane/air mixture at rest. Varied parameters are the inner pipe diameter and the pipe material. CFD computations, based on a URANS framework were carried out and enabled to recover several physical trends, such as the role of acoustics and boundary layer turbulence on the flame dynamics. Although most overpressure peaks orders of magnitude of the measured overpressure signals can be predicted numerically, the computed flames are quicker than the measured ones. It could be explained by the chosen turbulent model, the k-ω SST model, known to be adapted for wall-bounded flows but producing too much turbulence for accelerating flows. The criterion for the near wall cells (y + <200) might be too loose as well.
Uploads
Papers by Jérôme Daubech