Experimental and Numerical Investigation of H2-Air Deflagration in the Presence of Concentration Gradients

2013 ◽  
Author(s):  
S. Kudriakov ◽  
E. Studer ◽  
M. Kuznetsov ◽  
J. Grune
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Hydrogen Concentration ◽  
Concentration Gradient ◽  
Large Scale ◽  
Gravity Concentration ◽  
Concentration Gradients ◽  
Flame Acceleration ◽  
Institute Of Technology ◽  
Karlsruhe Institute

A set of experiments performed at Karlsruhe Institute of Technology (KIT) in the framework of the LACOMECO European project is devoted to flame propagation in an obstructed large scale facility A3 (of 8 m height and 33 m3 volume) with initially vertical hydrogen concentration gradients. Almost linear positive and negative (relative to gravity) concentration gradients are created prior to ignition in the range from 4% to 13%, and the process of flame acceleration is investigated depending on hydrogen concentration gradient and ignition positions. In this paper we describe the A3 facility and analyse the experimental data obtained during the project. The results of numerical simulation performed using Europlexus code are presented together with the critical discussions and conclusions.

Numerical Simulation of Oil-Droplet Cleavage by Surfactant

1996 ◽  
Vol 118 (2) ◽  
pp. 201-209 ◽  
Author(s):  
Xiaoyi He ◽  
Micah Dembo
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Surface Tension ◽  
Large Deformation ◽  
Concentration Gradient ◽  
Surface Tension Gradient ◽  
Oil Droplets ◽  
Numerical Computations ◽  
Oil Droplet ◽  
Pure Surface

We present numerical computations of the deformation of an oil-droplet under the influence of a surface tension gradient generated by the surfactant released at the poles (the Greenspan experiment). We find this deformation to be very small under the pure surface tension gradient. To explain the large deformation of oil droplets observed in Greenspan’s experiments, we propose the existence of a phoretic force generated by the concentration gradient of the surfactant. We show that this hypothesis successfully explains the available experimental data and we propose some further tests.

Hydrogen Detonation in a Flat Semi-Confined Layer

2012 ◽  
Author(s):  
M. Kuznetsov ◽  
J. Grune ◽  
T. Jordan ◽  
W. Rudy ◽  
A. Teodorczyk
Keyword(s):  
Hydrogen Concentration ◽  
Large Scale ◽  
Nuclear Reactor ◽  
Mechanical Response ◽  
Severe Accident ◽  
Critical Conditions ◽  
Significant Damage ◽  
Hydrogen Accumulation ◽  
Detonation Transition ◽  
Institute Of Technology

Hydrogen accumulation at the top of the containment or reactor building may occur due to an interaction of molten corium and water followed by a severe accident of a nuclear reactor (TMI, Chernobyl, Fukushima Dai-ichi). Hydrogen accumulates usually in a containment of nuclear reactor as a stratified semi-confined layer of hydrogen-air mixture. Detonation of such mixture may lead to significant damage of the containment structure. A series of large scale experiments on hydrogen combustion and detonation in a semi-confined layer of uniform and non-uniform hydrogen-air mixtures in presence of obstructions or without them was performed at the Karlsruhe Institute of Technology (KIT). Critical conditions for deflagration-to-detonation transition and then for steady state detonation propagation were experimentally evaluated in a flat semi-confined layer. The experiments were performed in a horizontal semi-confined layer with dimensions of 9×3×0.6 m with/without obstacles opened from below. The hydrogen concentration in the mixtures with air was varied in the range of 0–34 vol.% without or with a gradient of 0–1.1 mol. %H2/cm. Effects of hydrogen concentration gradient, thickness of the layer, geometry of the obstructions, average and maximum hydrogen concentration on critical conditions for detonation onset and then propagation were investigated with respect to the safety analysis. Blast wave strength and mechanical response of the safety volume was experimentally measured as well.

scholarly journals Experimental and numerical simulation on buried hot fuel oil pipelines in three modes flow regime considering temperature loss during a shutdown

2020 ◽  
pp. 345-345
Author(s):  
Mohsen Dehdarinejad ◽  
Morteza Behbahani-Nejad ◽  
Ebrahim Hajidavalloo
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Pour Point ◽  
Large Scale ◽  
Fuel Oil ◽  
Fluid Density ◽  
Temperature Dependent ◽  
Buried Pipelines ◽  
Temperature Loss ◽  
Oil Pipelines

Aiming to study the temperature distribution along buried pipelines containing hot fuel oil, a new large-scale laboratory is constructed from the perspective of the corresponding fluid thermophysical properties. Also, a modeling of the pipeline, and the soil around it, was performed along the pipeline for observation of all three modes of turbulent, laminarization, and laminar flow, which is validated by experimental results. Furthermore, the appropriate data are also gathered from the actual pipeline, 107 km of the 26? pipeline between Abadan Refinery and Mahshahr Port, and the results of the experiment and modeling are reconfirmed. The experiment shows that the viscosity and fluid density of fuel oil is strongly temperature-dependent. Many experiments are performed on the parameters affected by temperature according to their importance. The method chosen to simulate three flow modes along the pipeline shows less than 2% error in turbulent and laminar zones and reveals just a 3% error to experimental data in the laminar region. The maximum safe time during the stopping period of the pipeline (MSST) and holding fuel oil in it is calculated based on the pour point of fuel oil. This time is critical for the real pipeline in sudden shutdown and is calculated 41 hours.

Hydrogen-Air Deflagration in the Presence of Longitudinal Concentration Gradients

2013 ◽  
Author(s):  
S. Kudriakov ◽  
M. Kuznetsov ◽  
E. Studer ◽  
J. Grune
Keyword(s):  
Flame Propagation ◽  
Hydrogen Concentration ◽  
Concentration Gradient ◽  
Nuclear Reactor ◽  
Combustion Process ◽  
Pressure Sensors ◽  
Severe Accident ◽  
Critical Conditions ◽  
Local Concentration ◽  
Concentration Gradients

Hydrogen gathering at the top of the containment or reactor building may occur due to an interaction of molten corium and water followed by a severe accident of a nuclear reactor (like TMI, Chernobyl, Fukushima accidents). It accumulates usually in a containment of nuclear reactor as a stratified semi-confined layer of hydrogen-air mixture. Depending on the local concentration and/or presence and activation of mitigation devices, hydrogen may burn following different combustion regimes. Thus, there is a need to estimate the severity of a combustion process under given geometrical configuration, scale, ignition position, and uniformity and composition of combustible mixture. A series of experiments performed at Karlsruhe Institute of Technology (KIT) in the framework of the LACOMECO European project is devoted to flame propagation in an obstructed large scale cylinder vessel with vertical hydrogen concentration gradients. A 33 m3 volume divided in two sub-compartments, lower (21.6 m3) and upper (11.2 m3), separated by round duplex door of 1 m diameter with a metal structure with 6 layers of wooden plates reproduce real geometry of obstructions with a blockage ratio of 0.33–0.43. A sampling probes method is used to control real distribution of hydrogen. Practically linear positive and negative vertical concentration gradients in the range from 4 % to 13 % are created prior to ignition. Pressure sensors (PCB type), ion probes and thermocouples are used in the experiments to monitor dynamics of hydrogen combustion. The process of flame propagation is investigated depending on hydrogen concentration gradient and ignition positions. Critical conditions for flame acceleration-deceleration and quenching of the flame due to hydrogen concentration gradient are the main scopes of the work. The experimental data obtained during the project will be used for safety analysis, risk assessment and as benchmark experiments for CFD numerical codes validation.

scholarly journals Numerical Simulation of air Temperature and air flow Distribution in a Cabinet tray Dryer

2019 ◽  
Vol 8 (11) ◽  
pp. 1836-1840
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Air Temperature ◽  
Large Scale ◽  
Air Flow ◽  
Flow Distribution ◽  
Improve Quality ◽  
Air Movement ◽  
Drying Chamber

The quality of dried product can be enhanced in cabinet tray dryers through a uniform distribution of drying air flow and temperature. In this work, a numerical investigation is conducted to examine the consequence of air movement on the quality of product dried in a convective tray dryer. The temperature and velocity contours of air in the drying chamber are numerically determined for three different geometries of cabinet tray dryer and are compared. A good harmony is found between the predicted data from CFD and experimental data from the literature. This work will enable us to optimize the drying chamber design for uniform dispersal of air flow and temperature and to improve quality of dried product for large scale applications

Enhancement of the Concentration Gradients Generated in Microchambers Appended in Microfluidic Systems

2005 ◽  
Author(s):  
Yandong Hu ◽  
Jacky S. H. Lee ◽  
Carsten Werner ◽  
Dongqing Li
Keyword(s):  
Numerical Simulation ◽  
Concentration Gradient ◽  
Concentration Field ◽  
Cell Movement ◽  
Movement Control ◽  
Lab On A Chip ◽  
Concentration Gradients ◽  
Surface Patches ◽  
Gradient Based ◽  
Simulation Results

Concentration gradient in a chamber appended to a microchannel is important to cell movement control and to the concentration gradient based assays on Lab-on-a-Chip devises. In this paper, the effects on the concentration field of the asymmetrical injection, the Peclet number, the mobility ratio of electrophoresis to electroosmosis, the chamber’s downstream position, and the chamber’s geometry parameters, are investigated. The most sensitive parameter is the asymmetrical injection, which can increase the concentration gradient twice as large as to that in the symmetrical injection. Furthermore, using heterogeneous surface patches is a very effective way to enhance the concentration gradient generated in the chamber. Different patches for certain chambers are investigated. Finally, experimental visualization of the concentration fields was conducted, and good agreements were found between the numerical simulation results and the experimental results of the concentration fields generated in a micro-chamber with/without a heterogeneous patch.

Cost- und Monitoring-Projekt: Zwei neue forstliche Meinungsumfragen im Vergleich | The Cost- and Monitoring-Projects: A Comparison of Two New Forestry Opinion Polls

2000 ◽  
Vol 151 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Stephan Wild-Eck ◽  
Willi Zimmermann
Keyword(s):  
Large Scale ◽  
Forest Policy ◽  
Forest Economics ◽  
Positive Attitudes ◽  
Federal Institute ◽  
Swiss Confederation ◽  
Institute Of Technology ◽  
The Cost ◽  
Near Future ◽  
Opinion Polls

Two large-scale surveys looking at attitudes towards forests, forestry and forest policy in the second half ofthe nineties have been carried out. This work was done on behalf of the Swiss Confederation by the Chair of Forest Policy and Forest Economics of the Federal Institute of Technology (ETH) in Zurich. Not only did the two studies use very different methods, but the results also varied greatly as far as infrastructure and basic conditions were concerned. One of the main differences between the two studies was the fact that the first dealt only with mountainous areas, whereas the second was carried out on the whole Swiss population. The results of the studies reflect these differences:each produced its own specific findings. Where the same (or similar) questions were asked, the answers highlight not only how the attitudes of those questioned differ, but also views that they hold in common. Both surveys showed positive attitudes towards forests in general, as well as a deep-seated appreciation ofthe forest as a recreational area, and a positive approach to tending. Detailed results of the two surveys will be available in the near future.

Flight Path Planning of Robot for Environmental Measurement Considering Accuracy Assurance

Impact ◽  
2019 ◽  
Vol 2019 (10) ◽  
pp. 90-92
Author(s):  
Kae Doki ◽  
Yuki Funabora ◽  
Shinji Doki
Keyword(s):  
Large Scale ◽  
Highway Bridge ◽  
Climate Research ◽  
Small Uav ◽  
Inspection Process ◽  
Aerial View ◽  
Aerial Vehicle ◽  
Infrastructure Inspection ◽  
Institute Of Technology ◽  
Small Team

Every day we are seeing an increasing number of robots being employed in our day-to-day lives. They are working in factories, cleaning our houses and may soon be chauffeuring us around in vehicles. The affordability of drones too has come down and now it is conceivable for most anyone to own a sophisticated unmanned aerial vehicle (UAV). While fun to fly, these devices also represent powerful new tools for several industries. Anytime an aerial view is needed for a planning, surveillance or surveying, for example, a UAV can be deployed. Further still, equipping these vehicles with an array of sensors, for climate research or mapping, increases their capability even more. This gives companies, governments or researchers a cheap and safe way to collect vast amounts of data and complete tasks in remote or dangerous areas that were once impossible to reach. One area UAVs are proving to be particularly useful is infrastructure inspection. In countries all over the world large scale infrastructure projects like dams and bridges are ageing and in need of upkeep. Identifying which ones and exactly where they are in need of patching is a huge undertaking. Not only can this work be dangerous, requiring trained inspectors to climb these megaprojects, it is incredibly time consuming and costly. Enter the UAVs. With a fleet of specially equipped UAVs and a small team piloting them and interpreting the data they bring back the speed and safety of this work increases exponentially. The promise of UAVs to overturn the infrastructure inspection process is enticing, but there remain several obstacles to overcome. One is achieving the fine level of control and positioning required to navigate the robots around 3D structures for inspection. One can imagine that piloting a small UAV underneath a huge highway bridge without missing a single small crack is quite difficult, especially when the operators are safely on the ground hundreds of meters away. To do this knowing exactly where the vehicle is in space becomes a critical variable. The job can be made even easier if a flight plan based on set waypoints can be pre-programmed and followed autonomously by the UAV. It is exactly this problem that Dr Kae Doki from the Department of Electrical Engineering at Aichi Institute of Technology, and collaborators are focused on solving.

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