Predicting Tungsten Oxide Reduction with the Extended Discrete Element Method

in Advances in Powder Metallurgy & Particulate Materials (2015), (Proceedings of the 2015 International Conference on Powder Metallurgy Particulate Materials), 0235--0248

During technical reduction of tungsten trioxide powder in hydrogen atmospheres, the local temperature and the ratio of water vapor to hydrogen partial pressures govern the conversion rate. Water vapor ... [more ▼]

During technical reduction of tungsten trioxide powder in hydrogen atmospheres, the local temperature and the ratio of water vapor to hydrogen partial pressures govern the conversion rate. Water vapor removal rate not only affects the conversion progress, but also drives the final metallic tungsten powder size distribution. The amount of water vapor inside the bed depends on the hydrogen flow, the height of powder beds and the size characteristics of the initial oxide. The chemically aggressive environment and high temperatures make it difficult to do the measurements inside the reactors for studying or control the process. On the other hand, multi-physics computational techniques help to understand the evolution of the complex phenomena involved in the process. This contribution presents the eXtended Discrete Element Method as a novel approach to investigate the complex thermochemical conversion of tungsten oxides into tungsten metal. The recently emerged technique is based on a coupled discrete and continuous numerical simulation framework. In the study, an advanced and consolidated two-phase Computational Fluid Dynamics (CFD) tool for porous media represents gaseous phase penetration and transport. The discrete feedstock description includes one-dimensional and transient distributions of temperature and species for each powder particle. This allows gaining a new and valuable insight into the process, which may lead into finer tungsten powder production, and consequently more resistant tungsten carbide products. Transient and spatial results for powder composition, gas species as well as a mass loss comparison with experimental data for non-isothermal hydrogen reduction of tungsten trioxide are demonstrated and discussed. [less ▲]

Experimental and numerical investigation into iron ore reduction in packed beds

in Chemical Engineering Science (2015)

ROS homeostasis in a dynamic model: How to save PD neuron?

Poster (2014, December)

Mechanism-based model of ROS management in health and disease

Poster (2014, September)

ROS-activated signaling network: dynamic modelling and design principles study

Poster (2014, June)

Comparison of ODE-based models for reactive oxygen species regulation system

in Proceedings of ICCSA 2014 (2014, June)

Reactive oxygen species (ROS) play important role in the functioning of any cell and especially in the lifecycle of mitochondria. Since the action of ROS can be both positive and negative then the ... [more ▼]

Reactive oxygen species (ROS) play important role in the functioning of any cell and especially in the lifecycle of mitochondria. Since the action of ROS can be both positive and negative then the remarkable role can be played by ROS regulation system. We constructed three different ODE based kinetic models of different complexity for the ROS management system and shown the difference in the dynamics of these systems under different conditions. Using results of numerical simulation we showed that extraction of some subsystems can make the model more unstable. We also introduced the objective function for comparison of the models with structure of different complexity [less ▲]

Detailed numerical modeling of pyrolysis in a heterogeneous packed bed using XDEM

in Journal of Analytical and Applied Pyrolysis (2014), 106

XDEM - FEM Coupling Simulations of the Interactions between a Tire Tread and Granular Terrain

E-print/Working paper (2014)

This study proposes an efficient combination of the Discrete Element Method (DEM) and the Finite Element Method (FEM) to study the tractive performance of a rubber tire in interaction with granular ... [more ▼]

This study proposes an efficient combination of the Discrete Element Method (DEM) and the Finite Element Method (FEM) to study the tractive performance of a rubber tire in interaction with granular terrain. The presented approach is relevant to all engineering devices interacting with granular matter which causes response forces. Herein, the extended discrete element method (XDEM) is used to describe the dynamics of the granular assembly. On the one hand, the discrete approach accounts for the motion and forces of each grain individually. On the other hand, the finite element method accurately predicts the deformations and stresses acting within the tire tread. Hence, the simulation domain occupied by the tire tread is efficiently described as a continuous entity. The coupling of both methods is based on the interface shared by the two spatially separated domains. Contact forces develop at the interface and propagate into each domain. The coupling method enables to capture both responses simultaneously and allows to sufficiently resolve the different length scales. Each grain in contact with the surface of the tire tread generates a contact force which it reacts on repulsively. The contact forces sum up over the tread surface and cause the tire tread to deform. The coupling method compensates quite naturally the shortages of both numerical methods. It further employs a fast contact detection algorithm to save valuable computation time. The proposed DEM-FEM Coupling technique was employed to study the tractive performance of a rubber tire with lug tread patterns in a soil bed. The contact forces at the tread surface are captured by 3D simulations for a tire slip of 5%. The simulations showed to accurately recapture the gross tractive effort, running resistance and drawbar pull of the tire tread in comparison to related measurements. Further, the traction mechanisms between the tire tread and the granular ground are studied by analysing the motion of the soil grains and the deformation of the tread. [less ▲]

The extended discrete element method (XDEM) applied to drying of a packed bed

in Industrial Combustion (2014), 14

A vast number of engineering applications involve physics not solely of a single domain but of several physical phenomena, and therefore are referred to as multi-physical. As long as the phenomena ... [more ▼]

A vast number of engineering applications involve physics not solely of a single domain but of several physical phenomena, and therefore are referred to as multi-physical. As long as the phenomena considered are to be treated by either a continuous (i.e. Eulerian) or discrete (i.e. Lagrangian) approach, numerical solution methods may be employed to solve the problem. However, numerous challenges in engineering exist and evolve; those include modelling a continuous and discrete phase simultaneously, which cannot be solved accurately by continuous or discrete approaches only. Problems that involve both a continuous and a discrete phase are important in applications as diverse as the pharmaceutical industry, the food processing industry, mining, construction, agricultural machinery, metals manufacturing, energy production and systems biology. A novel technique referred to as Extended Discrete Element Method (XDEM) has been developed that offers a significant advancement for coupled discrete and continuous numerical simulation concepts. XDEM extends the dynamics of granular materials or particles as described through the classical discrete element method (DEM) to include additional properties such as the thermodynamic state or stress/strain for each particle coupled to a continuous phase such as a fluid flow or a solid structure. Contrary to a continuum mechanics concept, XDEM aims at resolving the particulate phase through the various processes attached to particles. While DEM predicts the spatial-temporal position and orientation for each particle, XDEM additionally estimates properties such as the internal temperature and/or species distribution during drying, pyrolysis or combustion of solid fuel material such as biomass in a packed bed. These predictive capabilities are further extended by an interaction with fluid flow by heat, mass and momentum transfer and the impact of particles on structures. © International Flame Research Foundation, 2014. [less ▲]

Experimental and Numerical Evaluation of the Residence Time Characteristics on a Forward Acting Grate

in Condensed Matter 2014 (2014)