Vented Explosion Phenomena: Hydrogen Combustion Benchmark on Confined Vessel Experiments

2016 ◽  
Author(s):  
Giovanni Manzini ◽  
Ivo Kljenak ◽  
Mantas Povilaitis
Keyword(s):  
Large Scale ◽  
Hydrogen Combustion ◽  
Flame Spreading ◽  
Plant Safety ◽  
Fast Running ◽  
Lumped Parameter ◽  
Complex Boundary ◽  
Spreading Rates ◽  
Vented Explosion ◽  
Running Calculation

Confined vented explosion is a very complex topic as many parameters affect the phenomena, mainly because the flame front develops from an ignition source and travels through a medium which may involve complex boundary conditions and obstructions of various geometries. Therefore, in the plant safety assessing step, it is important to provide correct estimates of the flame spreading rates as well as overpressures which may result from various explosion initiation scenarios. This will help designers for plant layout optimisation with the aim to minimize the risk associated with those events. Although hydrogen explosion in unvented compartments was often simulated in the past, there were not many opportunities, so far, to simulate explosion in a vented room. With this purpose, a benchmark exercise was organized, based on simple hydrogen combustion experiments, performed in a vented compartment (Chamber for View of Explosion – CVE) at the Scalbatraio laboratory of University of Pisa (Italy). In that activity, many tests were performed by varying the initial hydrogen concentration and the obstacles inside the compartment. The numerical codes used in the benchmark were lumped-parameter (LP) ones (ECART, ASTEC), which remain, for the time being, the customary tools for simulating hydrogen combustion accidents in current NPPs, because of their fast-running calculation capabilities also for large-scale scenarios.

scholarly journals Thermodynamic consequences of hydrogen combustion within a containment of pressurized water reactor

2011 ◽  
Vol 32 (4) ◽  
pp. 67-79
Author(s):  
Tomasz Bury
Keyword(s):  
Nuclear Power ◽  
Large Scale ◽  
Nuclear Reactor ◽  
Computer Code ◽  
Hydrogen Combustion ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor ◽  
Lumped Parameter ◽  
Loss Of Coolant

Thermodynamic consequences of hydrogen combustion within a containment of pressurized water reactor Gaseous hydrogen may be generated in a nuclear reactor system as an effect of the core overheating. This creates a risk of its uncontrolled combustion which may have a destructive consequences, as it could be observed during the Fukushima nuclear power plant accident. Favorable conditions for hydrogen production occur during heavy loss-of-coolant accidents. The author used an own computer code, called HEPCAL, of the lumped parameter type to realize a set of simulations of a large scale loss-of-coolant accidents scenarios within containment of second generation pressurized water reactor. Some simulations resulted in high pressure peaks, seemed to be irrational. A more detailed analysis and comparison with Three Mile Island and Fukushima accidents consequences allowed for withdrawing interesting conclusions.

An Efficient Preconditioner for Linear System Solution in Multi-Domain Modeling of the Circulatory System

2013 ◽  
Author(s):  
Mahdi Esmaily Moghadam ◽  
Yuri Bazilevs ◽  
Tain-Yen Hsia ◽  
Alison Marsden
Keyword(s):  
Strong Coupling ◽  
Large Scale ◽  
Computational Cost ◽  
Circulatory System ◽  
Flow Simulation ◽  
Global Dynamics ◽  
Domain Modeling ◽  
Computationally Efficient ◽  
Lumped Parameter ◽  
System Solution

A closed-loop lumped parameter network (LPN) coupled to a 3D domain is a powerful tool that can be used to model the global dynamics of the circulatory system. Coupling a 0D LPN to a 3D CFD domain is a numerically challenging problem, often associated with instabilities, extra computational cost, and loss of modularity. A computationally efficient finite element framework has been recently proposed that achieves numerical stability without sacrificing modularity [1]. This type of coupling introduces new challenges in the linear algebraic equation solver (LS), producing an strong coupling between flow and pressure that leads to an ill-conditioned tangent matrix. In this paper we exploit this strong coupling to obtain a novel and efficient algorithm for the linear solver (LS). We illustrate the efficiency of this method on several large-scale cardiovascular blood flow simulation problems.

Numerical Analysis of Hydrogen Risk Related Severe Accident Scenario in Chinese PWR

2016 ◽  
Author(s):  
Yang Fan ◽  
Sergey Kudriakov ◽  
Studer Etienne ◽  
Zou Zhiqiang ◽  
Hongxing Yu
Keyword(s):  
Large Scale ◽  
Complex Geometry ◽  
Combustion Process ◽  
Structure Design ◽  
Hydrogen Combustion ◽  
Severe Accident ◽  
Combustion Model ◽  
Combustion Simulation ◽  
Integrity Analysis ◽  
Safety Applications

Based on the fact that the pressure loads generated in hydrogen combustion process may jeopardize the integrity of the containment during severe accident, and the changing rate as well as the maximum value of the pressure loads are governed by the flame propagation process, it is important to simulate the hydrogen combustion process with proper methodology. Due to the insufficiency understanding of the turbulent combustion and the difficulties of hydrogen combustion simulation in large scale and complex geometry, explosion safety applications are always based on simplified combustion model, for which the validation work and specified conservative parameter is required. In this study, an methodology combining CFD analysis and model validation based on large scale combustion experiments (HDR E12 and HYCOM01/02) is built up. And domestic hydrogen combustion process in the containment during severe accident is simulated. This study provides solid basis for structure design and integrity analysis of the containment.

Investigation of New Generation of Ceramic and Single Crystalline Piezo Materials for Helicopter Blade and UAV Actuation

2013 ◽  
Author(s):  
Devdas Shetty ◽  
Claudio Campana ◽  
Nikolay Nazaryan ◽  
Louis Manzione
Keyword(s):  
Large Scale ◽  
Lumped Parameter Model ◽  
New Approach ◽  
Helicopter Blade ◽  
Aerospace Applications ◽  
Actuation System ◽  
Lumped Parameter ◽  
Piezoelectric Stacks ◽  
New Generation ◽  
Piezoelectric Stack Actuator

A great amount of research is being conducted to incorporate smart material actuators in aerospace applications such as (1) turbo fan engines (2) servo flap actuators for helicopter rotor control. For example, a piezoelectric stack actuator, coupled with mechanical or hydraulic amplification could provide the actuation required for the variable pitch fan system with a potentially higher level of reliability. In addition, piezoelectric actuation system could do so at a lower overall weight. However, there are limitations with existing piezoelectric stack actuators relative to power requirements. Therefore, a new approach has been investigated to improve these characteristics in order for piezoelectric stacks to be a feasible solution for these types of large scale applications. A new configuration involving dielectric, conductor, piezoelectric material in a particular sequence of stack actuation is examined and experimented. A nonlinear lumped parameter model of a piezoelectric stack has been developed to describe the behavior for the purpose of control actuation analysis.

Distribution of large-scale detachment faults on mid-ocean ridges in relation to spreading rates

2013 ◽  
Vol 32 (12) ◽  
pp. 109-117 ◽  
Author(s):  
Zhiteng Yu ◽  
Jiabiao Li ◽  
Yuyang Liang ◽  
Xiqiu Han ◽  
Jie Zhang ◽  
...  
Keyword(s):  
Large Scale ◽  
Detachment Faults ◽  
Ocean Ridges ◽  
Spreading Rates

ASTEC, COCOSYS, and LIRIC Interpretation of the Iodine Behavior in the Large-Scale THAI Test Iod-9

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
G. Weber ◽  
L. Bosland ◽  
F. Funke ◽  
G. Glowa ◽  
T. Kanzleiter
Keyword(s):  
Mass Transfer ◽  
Large Scale ◽  
Saint Paul ◽  
Molecular Iodine ◽  
Severe Accident ◽  
Research Network ◽  
Lumped Parameter ◽  
Post Test ◽  
Iodine Test ◽  
Iodine Transport

The large-scale iodine test Iod-9 of the German Thermal hydraulics, Hydrogen, Aerosols, Iodine (THAI) program was jointly interpreted by means of post-test analyses within the THAI Circle of the Severe Accident Research NETwork (SARNET)/Work Package 16. In this test, molecular iodine (I2) was injected into the vessel dome of the 60 m3 THAI vessel to observe the evolution of its distribution between water, gas, and surfaces. The main processes addressed in Iod-9 are (a) the mass transfer of I2 between the gas and the two sumps, (b) the iodine transport in the main sump when it is stratified and then mixed, and (c) the I2 adsorption onto, and desorption from, the vessel walls in the presence and absence of wall condensation. The codes applied by the THAI Circle partners were the Accident Source Term Evaluation Code (ASTEC)-IODE (IRSN, Saint Paul Lez Durance, France), Containment Code System (COCOSYS)-Advanced Iodine Model (AIM) (GRS, Garching, Germany), and Library of Iodine Reactions in Containment (LIRIC; AECL, Chalk River, ON, Canada). ASTEC-IODE and the Advanced Iodine Model (AIM) are semi-empirical iodine models integrated in the lumped-parameter codes ASTEC and COCOSYS, respectively. With both codes multicompartment iodine calculations can be performed. LIRIC is a mechanistic iodine model for single stand-alone calculations. The simulation results are compared with each other and with the experimental measurements. Special issues that were encountered during this work were studied in more details: I2 diffusion in the sump water, I2 reaction with the steel of the vessel wall in gaseous and aqueous phases, and I2 mass transfer from the gas to the sump. Iodine transport and behavior in THAI test Iod-9 are fairly well simulated by ASTEC-IODE, COCOSYS-AIM, and LIRIC in post-test calculations. The measured iodine behavior is well understood and all measured data are found to be consistent. The very slow iodine transport within the stratified main sump was simulated with COCOSYS only, in a qualitative way. Consequently, this work highlighted the need to improve modeling of (a) the wet iodine adsorption and the washdown from the walls, (b) the I2 mass transfer between gas and sump, and (c) the I2/steel reaction in the gaseous and aqueous phases. In any case, the analysis of the large-scale iodine test Iod-9 has been an important validation step for the codes applied.

ASTEC, COCOSYS, and LIRIC Interpretation of the Iodine Behaviour in the Large-Scale THAI Test Iod-9

2009 ◽  
Author(s):  
G. Weber ◽  
L. Bosland ◽  
F. Funke ◽  
G. Glowa ◽  
T. Kanzleiter
Keyword(s):  
Mass Transfer ◽  
Large Scale ◽  
Molecular Iodine ◽  
Measured Data ◽  
Lumped Parameter ◽  
Post Test ◽  
Iodine Test ◽  
Iodine Transport ◽  
Semi Empirical ◽  
Water Gas

The large-scale iodine test Iod-9 of the German THAI programme was jointly interpreted by means of post-test analyses within the THAI Circle of the SARNET/WP16. In this test, molecular iodine (I2) was injected into the vessel dome of the 60 m3 THAI vessel to observe the evolution of its distribution between water, gas, and surfaces. The main processes addressed in Iod-9 are (a) mass transfer of I2 between the gas and the two sumps, (b) iodine transport in the main sump when it is stratified and then mixed, and (c) I2 adsorption onto, and desorption from, the vessel walls in the presence and absence of wall condensation. The codes applied by the THAI Circle partners were ASTEC-IODE (IRSN), COCOSYS-AIM (GRS) and LIRIC (AECL). IODE and AIM are semi-empirical iodine models integrated in the lumped-parameter codes ASTEC and COCOSYS respectively. With both codes multi-compartment iodine calculations can be performed. LIRIC is a mechanistic iodine model for single stand-alone calculations. The simulation results are compared with each other and with the experimental measurements. Special issues that were encountered during this work were studied in more detail: I2 diffusion in the sump water, I2 reaction with the steel of the vessel wall in gaseous and aqueous phases, and I2 mass transfer from the gas to the sump. Iodine transport and behaviour in THAI test Iod-9 are fairly well simulated by ASTEC-IODE, COCOSYS-AIM and LIRIC in post-test calculations. The measured iodine behaviour is well understood and all measured data are found to be consistent. The very slow iodine transport within the stratified main sump was simulated with COCOSYS only, in a qualitative way. Consequently, this work highlighted the need to improve modelling of (a) the wet iodine adsorption and the washdown from the walls, (b) the I2 mass transfer between gas and sump, and (c) the I2/steel reaction in the gaseous and aqueous phases. In any case, the analysis of the large-scale iodine test Iod-9 has been an important validation step for the codes applied.

scholarly journals A Dialogic Perspective on Managing Knowledge Differences: Problem-Solving while Building a Nuclear Power Plant Safety System

2021 ◽  
pp. 017084062110618
Author(s):  
Chia-Yu Kou ◽  
Sarah Harvey
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Large Scale ◽  
Knowledge Integration ◽  
Safety System ◽  
Problem Situation ◽  
Plant Safety ◽  
Nuclear Power Plant Safety ◽  
Large Scale Project

To manage knowledge differences, existing research has documented two sets of practices: traversing and transcending knowledge boundaries. What research has yet to explore, however, is the dynamics through which traversing or transcending practices emerge in response to a particular problem situation. Using a qualitative, inductive study of the problem episodes encountered by groups of experts working on a large-scale project to build the safety system for a nuclear power plant, we observed that the emergence of traversing or transcending depended on how experts interpreted problems and initiated dialogues around specific problems. Our work provides insight into the condition through which knowledge integration trajectories may emerge.

scholarly journals Modeling and Validation of an Electrohydraulic Power Take-Off System for a Portable Wave Energy Convertor with Compressed Energy Storage

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3378
Author(s):  
Hao Tian ◽  
Zijian Zhou ◽  
Yu Sui
Keyword(s):  
Energy Storage ◽  
Wave Energy ◽  
Large Scale ◽  
Ocean Waves ◽  
Small Scale ◽  
Test Results ◽  
Traditional Architecture ◽  
Power Circuit ◽  
Lumped Parameter ◽  
Efficient Power

Small-scale, portable generation of electricity from ocean waves provides a versatile solution to power the ocean sensors network, in addition to the traditional large-scale wave energy conversion facilities. However, one issue of small-scale wave energy convertor (WEC) is the low capturable power density, challenging the design of the efficient power take-off (PTO) system. To tackle this challenge, in this paper, an electrohydraulic PTO system with compressed energy storage was proposed to boost output power of a portable WEC. Lumped-parameter kinematics and dynamics of the four-bar mechanism, the fluid dynamics of the digital fluid power circuit, and the mechanical and volumetric power losses were modeled and experimentally validated. Initial test results of the 0.64 m2 footprint prototype showed that the inclusion of storage improved the averaged electric power output over 40 times compared to the traditional architecture, and the proposed device can deliver up to 122 W at peaks.

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