CFD Simulation of Deflagration to Detonation Transition for Nuclear Safety

2014 ◽  
Author(s):  
Eduardo Hwang ◽  
Felipe Porto Ribeiro ◽  
Jian Su
Keyword(s):  
Shock Wave ◽  
Power Plants ◽  
Stokes Equations ◽  
Burning Velocity ◽  
Turbulent Flame ◽  
Flame Acceleration ◽  
Turbulent Flame Speed ◽  
Combustion Models ◽  
Deflagration To Detonation Transition ◽  
Detonation Transition

The present work aims to develop an efficient methodology for evaluating the Deflagration to Detonation Transition (DDT) in accidental scenarios from inherent hydrogen risk in water-cooled NPPs (Nuclear Power Plants). The physical problem is flame acceleration through a confined geometry congested with periodic obstacles, up to formation of a travelling shock wave. The problem was modeled by the Reynolds-averaged Navier-Stokes equations (RANS) with the standard k-ε turbulence model. There are two main combustion models: EDC (Eddy Dissipation Concept) whose equations are the transport equations for chemical species involved; and BVM (Burning Velocity Model) a transport equation for reaction progress (one scalar), to be used with three available turbulent flame speed correlations (Peters, Mueller and Zimont), and a new formulation based on Piston Action of the expanding burnt gas. The present work compared characteristics of these combustion models regarding flame acceleration in the midsize mc043 experiment, in order to apply the proposed combustion model in large scale DDT simulations. Experiment mc043 is consists of igniting a 12-meter long tube with 70 annular obstacles, filled with lean hydrogen-air mixture. The numerical results revealed that the proposed model is superior to BVM model correlations in predicting shock wave formation, and may provide a computationally more efficient option to the EDC model.

Flame acceleration and deflagration-to-detonation transition in narrow channels with thin obstacles

2018 ◽  
Vol 32 (29) ◽  
pp. 1850354 ◽  
Author(s):  
Jin Huang ◽  
Xiangyu Gao ◽  
Cheng Wang
Keyword(s):  
Turbulent Flame ◽  
Narrow Channels ◽  
Flame Acceleration ◽  
Deflagration To Detonation Transition ◽  
Smooth Channel ◽  
Detonation Transition ◽  
Run Up ◽  
Thin Obstacle ◽  
Strong Confinement ◽  
Small Spacing

The entire process of deflagration-to-detonation transition (DDT) in narrow channels with thin obstacle configurations is studied through high-resolution simulations. The results show that the confinement and disturbance of obstacles promote considerably the flame acceleration and DDT. There exist two modes of DDT associating with obstacle spacing S. For small spacing S, the flame acceleration depends on strong confinement and jet flow between obstacles; eventually DDT occurs due to early burning amplified by shocks in front of the flame. However, for large spacing S, the flame acceleration is mainly attributed to turbulence; DDT results from the interaction of reflection shock with turbulent flame. It is found that the run-up distance of DDT in the obstructed channels shortens significantly, as compared with that in the smooth channel.

Aerodynamic Quenching and Burning Velocity of Turbulent Premixed Methane-Air Flames

2015 ◽  
Author(s):  
Girish V. Nivarti ◽  
R. Stewart Cant
Keyword(s):  
Turbulence Intensity ◽  
Burning Velocity ◽  
Turbulent Flame ◽  
Premixed Flames ◽  
Experimental Studies ◽  
Flame Speed ◽  
Flame Surface ◽  
Turbulent Flame Speed ◽  
Combustion Models ◽  
Turbulent Premixed

Industry-relevant turbulent premixed combustion models continue to rely on empirical expressions for turbulent flame speed in closure modelling for the mean turbulent reaction rate. To date, an accurate sub-model for turbulent flame speed has not been proposed for flows with high turbulence intensities. Experimental studies in the pertinent combustion regime, known as the Thin Reaction Zones (TRZ) regime, are limited by the existing techniques of turbulence generation whereas, until recently, the high computational expense involved in solving such problems has restricted theoretical studies. We investigate the behaviour of premixed flames in the TRZ regime by conducting a parametric 3D Direct Numerical Simulation (DNS) study of stoichiometric methane-air mixtures using single-step chemistry in an inflow-outflow configuration. Inflow turbulence intensity is varied while keeping the integral length scale constant across six separate simulations which span altogether a significant portion of the TRZ regime. The resulting variation of turbulent flame speed with turbulence intensity demonstrates the well-known bending phenomenon and conforms with recent experimental observations of freely-propagating premixed flames in this regime. As turbulence intensity is increased, the calculated flame surface exhibits an increasing degree of wrinkling and pocket-formation. In addition, the internal thermo-chemical structure of the flame is greatly affected when the turbulence intensity is more than an order of magnitude higher than the laminar flame speed. These qualitative observations establish the present DNS framework as a powerful tool for capturing turbulence-chemistry interactions that influence the bending phenomenon. Hence, this work forms the basis for further analysis using a detailed chemical description to investigate these interactions and, thereby, improve combustion models of industrial relevance.

The Physics of Detonation Chemistry: A Radical Theory in Predicting the Deflagration to Detonation Transition and Environmental Explosions

2021 ◽  
Author(s):  
V.R. Sanal Kumar ◽  
Nichith Chandrasekaran ◽  
Vigneshwaran Sankar ◽  
Ajith Sukumaran ◽  
Sivabalan Mani ◽  
...  
Keyword(s):  
Shock Wave ◽  
In Silico ◽  
Pressure Ratio ◽  
Continuity Condition ◽  
Reacting Flow ◽  
Radical Theory ◽  
Flow Choking ◽  
Deflagration To Detonation Transition ◽  
Theoretical Finding ◽  
Detonation Transition

Abstract The theoretical finding of the Sanal-flow-choking [PMCID: PMC7267099] and streamtube flow choking (V.R.Sanal Kumar et al., Physics of Fluids, Vol.33, No.3, 2021, DOI: 10.1063/5.0040440) are methodological advancements in predicting the deflagration-to-detonation-transition (DDT) in the real-world-fluid flows (continuum/non-continuum) with credibility.[1,2] Herein, we provide a proof of the concept of the Sanal-flow-choking and streamtube-flow-choking causing DDT in wall-bounded and free-external flows. Once the streamlines compacted, the considerable pressure difference attains inside the streamtube and the flow gets accelerated to the constricted region for satisfying the continuity condition set by the conservation law of nature. If the shape of the streamtube in the internal/external flow is similar to the convergent-divergent (CD) duct the phenomenon of the Sanal-flow-choking and supersonic flow development occurs at a critical-total-to-static pressure ratio (CPR) in yocto to yotta scale systems and beyond, which leads to shock wave generation or detonation as the case may me. At the lower critical detonation or hemorrhage index, the CPR of the reacting flow and the critical blood-pressure-ratio (BPR) of the subjects (human being/animal) are unique functions of the heat-capacity-ratio (HCR) of the evolved gas in the CD duct (V.R.Sanal Kumar et al., Global Challenges, Wiley Publication, January 2021, DOI: 10.1002/gch2.202000076, PMCID: PMC7933821; Sanal Kumar V.R et al. Stroke, Vol. 52, Issue Suppl_11 March 2021, doi.org/10.1161/str.52.suppl_1.P804). In silico results are presented herein to establish the proof of the concept of the Sanal-flow-choking and streamtube-flow-choking causing shock-wave/detonation in diabatic flow systems and asymptomatic-hemorrhagic-stroke in biological systems. The physics of detonation chemistry presented herein sheds light for exploring environmental and supernova explosions.[107] In silico results reported herein provide an authentic answer to many unresolved research questions in Physics in general and aerospace, mechanical, biological, chemical, energy, environmental, nano and material sciences in particular.

scholarly journals Numerical Analysis for Hydrogen Flame Acceleration during a Severe Accident in the APR1400 Containment Using a Multi-Dimensional Hydrogen Analysis System

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 6151
Author(s):  
Hyung Seok Kang ◽  
Jongtae Kim ◽  
Seong Wan Hong ◽  
Sang Baik Kim
Keyword(s):  
Turbulent Flame ◽  
Hydrogen Combustion ◽  
Hydrogen Release ◽  
Severe Accident ◽  
Flame Acceleration ◽  
Turbulent Flame Speed ◽  
Analysis Methodology ◽  
Hydrogen Flame ◽  
Hydrogen Analysis ◽  
Analysis System

Korea Atomic Energy Research Institute (KAERI) established a multi-dimensional hydrogen analysis system to evaluate hydrogen release, distribution, and combustion in the containment of a Nuclear Power Plant (NPP), using MAAP, GASFLOW, and COM3D. In particular, KAERI developed an analysis methodology for a hydrogen flame acceleration, on the basis of the COM3D validation results against measured data of the hydrogen combustion tests in the ENACCEF and THAI facilities. The proposed analysis methodology accurately predicted the peak overpressure with an error range of approximately ±10%, using the Kawanabe model used for a turbulent flame speed in the COM3D. KAERI performed a hydrogen flame acceleration analysis using the multi-dimensional hydrogen analysis system for a severe accident initiated by a station blackout (SBO), under the assumption of 100% metal–water reaction in the Reactor Pressure Vessel (RPV), to evaluate an overpressure buildup in the containment of the Advanced Power Reactor 1400 MWe (APR1400). The magnitude of the overpressure buildup in the APR1400 containment might be used as a criterion to judge whether the containment integrity is maintained or not, when the hydrogen combustion occurs during a severe accident. The COM3D calculation results using the established analysis methodology showed that the calculated peak pressure in the containment was lower than the fracture pressure of the APR1400 containment. This calculation result might have resulted from a large air volume of the containment, a reduced hydrogen concentration owing to passive auto-catalytic recombiners installed in the containment during the hydrogen release from the RPV, and a lot of stem presence during the hydrogen combustion period in the containment. Therefore, we found that the current design of the APR1400 containment maintained its integrity when the flame acceleration occurred during the severe accident initiated by the SBO accident.

Hydrogen–Air–Steam Deflagration Experiment Simulated Using Different Turbulent Flame-Speed Closure Models

2018 ◽  
Vol 4 (3) ◽  
Author(s):  
Holler Tadej ◽  
Ed M. J. Komen ◽  
Kljenak Ivo
Keyword(s):  
Flame Propagation ◽  
Nuclear Power ◽  
Large Scale ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Energy Output ◽  
Combustion Model ◽  
Turbulent Flame Speed ◽  
Modeling Approach ◽  
Combustion Models

The paper presents the computational fluid dynamics (CFD) combustion modeling approach based on two combustion models. This modeling approach was applied to a hydrogen deflagration experiment conducted in a large-scale confined experimental vessel. The used combustion models were Zimont's turbulent flame-speed closure (TFC) model and Lipatnikov's flame-speed closure (FSC) model. The conducted simulations are aimed to aid identifying and evaluating the potential hydrogen risks in nuclear power plant (NPP) containment. The simulation results show good agreement with experiment for axial flame propagation using the Lipatnikov combustion model. However, substantial overprediction in radial flame propagation is observed using both combustion models, which consequently results also in overprediction of the pressure increase rate and overall combustion energy output. As assumed for a large-scale experiment without any turbulence inducing structures, the combustion took place in low-turbulence regimes, where the Lipatnikov combustion model, due to its inclusion of quasi-laminar source term, has advantage over the Zimont model.

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