Graz, Austria
Graz, Austria

Time filter

Source Type

Raic K.T.,University of Belgrade | Rudolf R.,University of Maribor | Ternik P.,Bresterniska ulica 163 | Zunic Z.,AVL AST | And 3 more authors.
Materiali in Tehnologije | Year: 2011

This work presents the possibility of numerical modelling using Computational Fluid Dynamics (CFD) in the field of nano-foils. The governing equations were solved using a Finite Volume Methodology (FVM). The computational domain was discretized using a uniform Cartesian grid with the appropriate mesh size along the x and y directions employing the corresponding number of grid points. The field variables were discretized at the cell centres and the spatial, as well as the time, derivatives were approximated using the second-order accurate numerical scheme. The time-evolution of the temperature and concentration fields, as well as the atomic diffusion coefficient, will be presented for the appropriate Al-Au nano-foil geometry and boundary conditions.


Ternik P.,Bresterniska ulica 163 | Rudolf R.,University of Maribor | Zunic Z.,AVL AST
Materiali in Tehnologije | Year: 2013

The present work deals with the natural convection in a square cavity filled with a water-based Au nanofluid. The cavity is heated from the lower and cooled from the adjacent wall, while the other two walls are adiabatic. The governing differential equations have been solved with the standard finite volume method and the hydrodynamic and thermal fields have been coupled using the Boussinesq approximation. The main objective of this study is to investigate the influence of the nanoparticles' volume fraction on the heat-transfer characteristics of Au nanofluids at a given base-fluid (i.e., water) Rayleigh number Rabf. Accurate results are presented over a wide range of the base-fluid Rayleigh numbers (102 ≤ Rabf ≤ 105) and the volume fraction of Au nanoparticles (0 % ≤ φ ≤ 10 %). It is shown that adding nanoparticles to the base fluid delays the onset of convection. Contrary to what is argued by many authors, we show, with numericalsimulations, that the use of nanofluids can reduce the heat transfer instead of increasing it.


Ternik P.,Bresterniska ulica 163 | Rudolf R.,University of Maribor | Zunic Z.,AVL AST
Materiali in Tehnologije | Year: 2012

A numerical analysis is performed to examine the heat transfer of colloidal dispersions of Au nanoparticles in water (Au nanofluids). The analysis used a two-dimensional enclosure under natural convection heat-transfer conditions and has been carried out for the Rayleigh number in the range of 10 3 ≤ Ra ≤ 10 5, and for the Au nanoparticles' volume-fraction range of 0 ≤ φ ≤ 0.10. We report highly accurate numerical results indicating clearly that the mean Nusselt number is an increasing function of both Rayleigh number and volume fraction of Au nanoparticles. The results also indicate that a heat-transfer enhancement is possible using nanofluids in comparison to conventional fluids. However, low Rayleigh numbers show more enhancement compared to high Rayleigh numbers.


Mikulcic H.,University of Zagreb | Von Berg E.,AVL AST | Vujanovic M.,University of Zagreb | Priesching P.,AVL AST | And 2 more authors.
Chemical Engineering Transactions | Year: 2012

Cement calciners are pyroprocessing units found in modern cement plants. Inside of them occurs a strong endothermic reaction known as the calcination process, and the combustion of pulverized solid fuels. Controlling the mixing of limestone and pulverized fuel particles is of particular importance because it directly affects the energy consumption. The paper analyzes the impact of an axial and a swirl burner on the mixing of the particles, pollutant emissions and the operating conditions of a newly designed cement calciner. All necessary numerical models were developed and implemented into a commercial computational fluid dynamics code FIRE, which is then used for the analysis. This code is used to simulate turbulent flow field, temperature field, concentrations of the reactants and products as well as the interaction of particles with the gas phase, by solving the set of conservation equations for mass, momentum and enthalpy governing these processes. The results gained by these simulations can be used for the optimization of cement calciner's operating conditions. Copyright © 2012, AIDIC Servizi S.r.l.


Mikulcic H.,University of Zagreb | von Berg E.,AVL AST | Vujanovic M.,University of Zagreb | Priesching P.,AVL AST | And 3 more authors.
Chemical Engineering Science | Year: 2012

Calcination is a thermo-chemical process, widely used in the cement industry, where limestone is converted by thermal decomposition into lime CaO and carbon dioxide CO 2. The focus of this paper is on the implementation and validation of the endothermic calcination reaction mechanism of limestone in a commercial finite volume based CFD code. This code is used to simulate the turbulent flow field, the temperature field, concentrations of the reactants and products, as well as the interaction of particles with the gas phase, by solving the mathematical equations, which govern these processes. For calcination, the effects of temperature, decomposition pressure, diffusion and pore efficiency were taken into account. A simple three-dimensional geometry of a pipe reactor was used for numerical simulations. To verify the accuracy of the modelling approach, the numerical predictions were compared with experimental data, yielding satisfying results and proper trends of physical parameters influencing the process. © 2011 Elsevier Ltd.


Mikulcic H.,University of Zagreb | Von Berg E.,AVL AST | Vujanovic M.,University of Zagreb | Priesching P.,AVL AST | And 2 more authors.
Clean Technologies and Environmental Policy | Year: 2013

Efficient mixing of pulverized fuel and limestone particles inside cement calciners is important due to the reason that the calcination process directly affects the final fuel consumption. The focus of this paper is on the numerical analysis of cement calciner's operating conditions and pollutant emissions. The paper analyzes the influence of different amounts of fuel, mass flow of the tertiary air and the adiabatic wall condition on the decomposition rate of limestone particles, burnout rate of coal particles, and pollutant emissions of a newly designed cement calciner. Numerical models of calcination process and pulverized coal combustion were developed and implemented into a commercial computational fluid dynamics code, which was then used for the analysis. This code was used to simulate turbulent flow field, interaction of particles with the gas phase, temperature field, and concentrations of the reactants and products, by solving the set of conservation equations for mass, momentum, and enthalpy that govern these processes. A three-dimensional geometry of a real industrial cement calciner was used for numerical simulations. The results gained by these numerical simulations can be used for the optimization of cement calciner's operating conditions, and for the reducing of its pollutant emissions. © 2013 Springer-Verlag Berlin Heidelberg.


Jankovic D.,AVL AST | Mihajlovic Z.,University of Zagreb
MIPRO 2011 - 34th International Convention on Information and Communication Technology, Electronics and Microelectronics - Proceedings | Year: 2011

Terrain models typically contain huge amount of data so they are very time consuming for visualization purposes. This especially comes to the forefront when urban environments are included. The main compromise in representation of the complex environments is between achieved quality and time consumption. With the simple texture representation of complex environments we will accomplish fast application, and with the large polygonal meshes, high quality of the rendered scene. In this paper we propose rendering of urban and natural environments using parallax and relief mapping. This approach combines benefits of the rendering of polygonal meshes and texture approach. Thereby, in the proposed approach improved quality on the one side and increased speed on the other side is combined. The applicability of the method is demonstrated trough parallax and relief mapping within the Irrilicht open source graphics engine. The shaders programs were made with the GLSL shader language. As the result, the tests were made to determine the possible usage of parallax and relief mapping in the display of natural and urban environments. © 2011 MIPRO.


Mikulcic H.,University of Zagreb | Von Berg E.,AVL AST | Vujanovic M.,University of Zagreb | Duic N.,University of Zagreb
Waste Management and Research | Year: 2014

The use of waste wood biomass as fuel is increasingly gaining significance in the cement industry. The combustion of biomass and particularly co-firing of biomass and coal in existing pulverized-fuel burners still faces significant challenges. One possibility for the ex ante control and investigation of the co-firing process are computational fluid dynamics (CFD) simulations. The purpose of this paper is to present a numerical analysis of co-firing pulverized coal and biomass in a cement calciner. Numerical models of pulverized coal and biomass combustion were developed and implemented into a commercial CFD code FIRE, which was then used for the analysis. Three-dimensional geometry of a real industrial cement calciner was used for the analysis. Three different co-firing cases were analysed. The results obtained from this study can be used for assessing different co-firing cases, and for improving the understanding of the co-firing process inside the calculated calciner. © The Author(s) 2014.


PubMed | AVL AST and University of Zagreb
Type: Journal Article | Journal: Waste management & research : the journal of the International Solid Wastes and Public Cleansing Association, ISWA | Year: 2016

The use of waste wood biomass as fuel is increasingly gaining significance in the cement industry. The combustion of biomass and particularly co-firing of biomass and coal in existing pulverized-fuel burners still faces significant challenges. One possibility for the ex ante control and investigation of the co-firing process are computational fluid dynamics (CFD) simulations. The purpose of this paper is to present a numerical analysis of co-firing pulverized coal and biomass in a cement calciner. Numerical models of pulverized coal and biomass combustion were developed and implemented into a commercial CFD code FIRE, which was then used for the analysis. Three-dimensional geometry of a real industrial cement calciner was used for the analysis. Three different co-firing cases were analysed. The results obtained from this study can be used for assessing different co-firing cases, and for improving the understanding of the co-firing process inside the calculated calciner.


Costa M.,CNR Istituto Motori | Sorge U.,AVL AST | Merola S.,CNR Istituto Motori | Irimescu A.,CNR Istituto Motori | And 2 more authors.
Energy | Year: 2016

The effects of splitting the injection event in a GDI (gasoline direct injection) engine operating with a HOS (homogeneous stratified) lean charge are analysed through experimental and numerical techniques. Injection is assumed as divided in two parts, each delivering the same gasoline amount, the first occurring during intake, the second during compression.The work is initially focused on the experimental characterization of the engine under study for the collection of data concerning the in-chamber combustion development. Beside measurements of in-cylinder pressure, UV chemiluminescence is applied to follow the OH radicals formation from spark ignition up to the late combustion phase, thanks to the optical accessibility to the combustion chamber. The collected data serve to the validation of a properly formulated three-dimensional (3D) CFDs model for the simulation of the whole engine working cycle.The definition of the control strategy leading to the greatest combustion efficiency and lowest pollutants emission is made in two steps through numerical optimization: the 3D CFD model is first run to build a low number of samples to be used within a Gaussian RSM (response surface method) to reconstruct, in the DOE (design of experiments) space, the integral of the in-cylinder pressure over volume in the closed valve period; in the second step, the coupling between the 3D engine model and the Simplex algorithm is performed in a restricted DOE subdomain defined according to the first step analysis. The assessed methodology highlights the synchronization of both spark ignition and split injection leading to the highest power output and the lowest pollutants release. The experimental verification of the numerical findings is finally carried out. © 2016 Elsevier Ltd.

Loading AVL AST collaborators
Loading AVL AST collaborators