• Concept of an energy system emulator

    pg(s) 59-62

    Research, optimization and practical implementation of the optimization processes of energy subsystems of power, heating and industrial plants is a relatively complex task that is unimaginable today without specialized computer support tools. The energy system emulator itself represents a tool for development and application work with energy systems, which is based on today’s standard decentralized control systems. The basic principles of the modular construction of the emulator and an example of its implementation based on the Siemens SIMATIC-S7 DCS system are shown. In addition to the design of the energy systems emulator concept, the article also presents a design of a hydraulic turbine model as the most important subsystem of a hydropower plant, the efficiency calculation of which is analytically demanding and dependent on parameters that are often obtained only by a theoretical estimation. In this article, a fuzzy system was used to create the model based on measured operating data of the turbine flow rate and the height of its water column without any need to know the exact turbine parameters.

  • Experimental and statistical models for determining the critical values of external action parameters on optical elements in extreme conditions of their operation

    pg(s) 55-58

    The study has been carried out and experimental and statistical models have been developed to determine the critical values of external extreme action parameters (intense heat flows, times of their action, increased external pressures) on optical elements made of glass and ceramics, the excess of which leads to their surface destruction (the appearance of cracks, chips and other defects) and, ultimately, to the failure of optoelectronic devices.

  • Optimization of the rubber forming process for the sheet metal part using numerical simulation

    pg(s) 51-54

    This article focuses on the optimization of manufacturability for the aluminium cover produced by rubber forming. Aluminium Al6016 was considered as a material for the cover and its constitutive equations Hill 48 and Hollomon described its properties. The Mooney-Rivlin hyperelastic material model defined material properties for a punch made of rubber. Pam stamp software was used to create the simulation model and evaluation. Results were optimized from the view of thickness reduction and punch stroke when two different rubber hardness were selected.

  • Numerical investigation of wind-assisted ship propulsion systems

    pg(s) 47-50

    The paper studies three of the most applicable wind-assisted ship propulsion systems: soft sails, Dynarig sails and Flettner rotors, in particular the wind forces on the sails. Traditionally, and still most reliably, these forces are determined by model testing in wind tunnels. Unfortunately, experimental results of different WAPS are quite scarce. On the other hand, the intensive development of Computational Fluid Dynamics (CFD) nowadays allows faster and more economical evaluation of aerodynamic forces and optimization of shapes. CFD modelling is applied here for evaluation of the aerodynamic forces on sails.

  • Study of binary liquid capillary bridges stretched between two solid flat surfaces

    pg(s) 13-16

    Liquid capillary bridges (CBs), created between two flat solid surfaces, parallel to each other, are of significant importance for number of scientific and industrial applications. In this paper, we present our experimental investigation of the liquid CBs at stretching, created by two immiscible liquids: cedar oil–water and paraffin-water with common interface. The behaviour of these binary structures was studied and compared with that of the single liquid CBs. It was found that the binary liquid CBs exist in the same definition domain as the single liquid CBs. Moreover, the current paper is focused not only on static, but also on non-equilibrium behaviour of CBs. We demonstrate that the binary liquid CBs can be engineered by the proper combination of polar (water) and non-polar (oil) fluids and these CBs exist within the theoretically predicted domain. The experimental results of water/cedar oil and water/paraffin binary CBs shows that the paraffin spreads in water surface and modifies the overall surface tension of the system, while the cedar oil and water retain their surface properties within the binary structure.

  • Verified model of plasticization of polymers during injection moulding as a tool optimizing the design of injection moulding machine components

    pg(s) 9-12

    The article briefly presents the possibilities of the created and verified model of polymer plasticization during injection molding. Exemplary characteristics generated by the model are presented and examples of applications of the described model for supporting the design of plasticizing systems of injection molding machines are indicated.

  • Behaviour of SPP waves frequency spectrum for dielectric/metal/dielectric structures

    pg(s) 6-8

    In this paper, the authors studied the influence of different phenomena and materials properties on the frequency spectrum of the surface plasmon-polariton (SPP) waves behaviour in “dielectric/metal/dielectric” structures. Among them are spatial dispersion, quantization of energy levels, electron-electron interaction (Coulomb correlations) thickness of a metal layer. Established that for atomically thin metal films mentioned effects affect the frequency spectrum significantly. Mentioned that taking into account quantum-sized effects reveals a specific oscillatory picture of the spectrum that repeats one obtained for chemical potential. Proposed model yields results that have a quite good agreement with an experimental data.

  • Numerical modeling of impact interaction between an active element and a deformable barrier

    pg(s) 139-140

    A methodology for calculating the impact interaction between an active element and a deformable barrier is developed on the basis of approximated analytical results. As an active element is considered a hemisphere smoothly shaped into a cylinder. Results from calculations using the proposed methodology are applied. The examples presented here are two extreme cases of interaction that differ from each other by the initial angle of contact of the active element with the barrier.

  • Implementation of simulation tools in optimization of traffic flows – case study City of Zagreb

    pg(s) 136-138

    Urbanization and population growth in cities around the world have increased the degree of motorization, which ultimately results in congestion of the transport network within these cities. Traffic simulation tools are essential for the optimization and evaluation of variant solutions in road traffic. By analysing traffic parameters from simulation results it can be decided which variant solution is optimal without high financial inputs. In this paper, the most important simulation tools are explained. As a case study, one district in the City of Zagreb was chosen to present possibilities of simulation tools and their implementation in the evaluation of traffic solutions.

  • Multicriterial optimization strategies for electron beam grafting of corn starch

    pg(s) 133-135

    Grafting is the most effective way of modifying and regulating the properties of natural polysaccharides for the production of highly efficient graft copolymers, which have applications as flocculating agents for the treatment of different wastewaters. An experimental investigation connected with the modification of starch by grafting acrylamide with the application of electron beam irradiat ion is performed. In this paper the implementation of different multi-criteria optimization strategies, solving the problem with the choice between several compromise Pareto-optimal solutions are presented and compared for the process of electron beam grafting of corn starch. The compromise Pareto-optimal solutions are obtained by implementation of genetic algorithm and a set of requirements for the desired reference direction (minimum or maximum) and the constraints of the investigated quality characteristics and their variances under production conditions, which ensure the fulfilment of several goals – economic efficiency, assurance of low toxicity and high copolymer efficiency in flocculation process.