Machines. Technologies. Materials.
Vol. 17 (2023), Issue 8

Table of Contents

  • MACHINES

    • Energy evaluation of a three-cylinder steam turbine which operates in combined cycle power plant

      pg(s) 294-297

      This paper presents an energy analysis of a three-cylinder steam turbine from a combined cycle power plant. Observing all the cylinders from the analyzed turbine, it is found that the dominant mechanical power producer is Low Pressure Cylinder (LPC), followed by the Intermediate Pressure Cylinder (IPC), while High Pressure Cylinder (HPC) is the cylinder which produces the lowest mechanical power. Whole observed steam turbine develop 119.41 MW of useful mechanical power. Energy loss and energy efficiency of all cylinders are reverse proportional – higher energy efficiency will result with lower energy loss and vice versa. IPC is the cylinder which has the lowest energy loss (equal to 2.59 MW) and the highest energy efficiency of 93.32%. Whole observed steam turbine has energy loss equal to 23.43 MW, while its energy efficiency is equal to 83.60%, what falls in the expected range of such low power steam turbines. Steam mass flow rate through each cylinder is the main element which defines produced mechanical power and energy flows.

    • Innovative mill complex for processing glass waste, applicable to the production of foam glass and composite materials

      pg(s) 298-301

      An innovative mill complex has been developed for the processing of glass waste applicable to the production of granular foam glass and fire-resistant, energy-saving, acoustic and thermal insulation composite building elements. The presented design solution is in accordance with the necessary technological characteristics of the ground vitreous raw material for use in the production process. It is envisaged that the grinding will be carried out in two stages and will be combined with homogenization of the batch being prepared. The first stage is the initial grinding of the raw material in a vibrating mill with metal grinding bodies, allowing grinding for a shorter period of time to a certain size of the particles with minimal contamination. In the second stage, the final grinding (up to a technological size of the particles) and homogenization is carried out in a ball mill with non-metallic grinding bodies. The main production equipment necessary for the realization of the presented technological process was considered.

    • Classification of variants of suspended ropeways lines

      pg(s) 302-304

      In the present work, a classification of the suspended ropeways has been made according to purpose and structural composition feature. They are mainly chair and cabin aerial ropeways. The structure of passenger ropeway structures and the standards they must meet are described in more detail. The chemical composition of the ropes, the types of tangles and the standards for their production, maintenance and operation are specified. The classification made gives a multi-criteria optimization, which aims to support the choice in the design of ropeways.

    • Industry 4.0 Approach for Development of Automatic Sanitation Unit

      pg(s) 305-307

      In wet wipe machines, equipment such as tanks, pumps, pipes, and valves that come into contact with the wet wipe solution, conveyor belts, and steel surfaces with which the liquid comes into contact, must be disinfected at regular intervals under hygienic production rules. Disinfection is carried out using hot water, alcohol-based disinfectants, surfactants, detergents, oxidizing agents, or a mixture of all these methods. In current applications, liquids are drained manually from preparation units or tanks, and machine surfaces are cleaned manually. Cleaning and sanitation is done by hand. At the same time, performing some cleaning scenarios is harmful to human health because of hot steam or water, chemical cleaning steam, etc. So, it is impossible to ensure the hygiene level of systems. In this study, safe by design and prevention approaches were used and a system equipped with several measurement sensors was designed to work with different sanitary liquids and their preparation units according to sanitary recipes, producing a report at the end of the cleaning process. There are devices such as pH meters, temperature sensors, pressure sensors, and several water analyzers in the system, and it is decided that cleaning is completed by processing the data from these sensors. This article describes the system developed in compliance with industry 4.0 applications

    • Permissible number of switches on per hour of electric motors for horizontally moving crane mechanisms

      pg(s) 308-313

      Paper deals with determining the permissible number of switches on per hour depending on the load and operating mode parameters – starting and stopping times, pause duration, etc. The criterion is that the overheating of the stator winding does not exceed the overheating at nominal mode and load. The basis of the chosen method is the assumption that the electric motor is assumed to be a conditionally uniform body, i.e. a body made of the same material with an infinitely large thermal conductivity and therefore having the same temperature throughout its volume under all possible modes and loads. The results of the calculations with a computer program
      implemented are presented in tabular form.

  • TECHNOLOGIES

    • Types of Lasers used in metal processing

      pg(s) 314-316

      This paper elucidates the salient features of CO2, Nd: YAG, and fiber lasers in the context of their application in metal processing. Operating at 10.6 micrometers, CO2 lasers exhibit variable power outputs, crucial for tasks such as cutting and welding. Nd: YAG lasers, working at 1.064 micrometers, demonstrate versatility in pulse modes, with their efficiency intricately linked to quantum defect and thermal effects. Fiber lasers, with an operational wavelength of 1.07 micrometers, showcase heightened efficiency (30-40%) owing to superior pump light absorption. While mathematical models provide foundational insights, the practical efficacy of these lasers’ hinges on nuanced factors, necessitating advanced empirical investigations for optimized application.

    • Morphology and structure of oxide thin films obtained by the sol-gel method: a review

      pg(s) 317-323

      One-component CeO2 coatings and bi-component CeO2/ZrO2 multilayer coatings were obtained by a sol gel process. The phase composition, surface morphology and roughness of the samples were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Atomic force microscopy (AFM) and X-ray scanning electron microscopy (XPS). The corrosion resistance and protective ability were characterized by using salty solution of 3.5% NaCl at 25 C. The multilayer configuration of CeO2 and ZrO2 ensure enhanced protection of the steel in comparison to the single CeO2 coatings and uncoated steel. The surface morphology and anticorrosion properties depend significantly on the treatment temperature of both CeO2 underlayer and ZrO2 top layer. At lower treatment temperatures, they are relatively dense and smooth. The corrosion resistance of the multilayers slows down, when ZrO2 coatings were heated above 500oC. This probably is due to the more pronounced crystallization of cubic zirconium dioxide, resulting in deeper boundaries between the individual grains. The protective properties of a CeO2/ZrO2 multilayers could be attributed to the low crystallized structure with very fine crystallites.

  • MATERIALS

    • A study on deflections of GFRP reinforced concrete beams.

      pg(s) 329-333

      Steel reinforcing bars have not performed well in applications where members were subject to corrosive environments. Alkaline concrete protection can provide relatively good protection of the steel reinforcement, but when these are exposed to an aggressive environment or the protection breaks down, the reinforcement starts the corrosive process and it leads to rupture and fragmentation of the protective layer of concrete.
      These reasons lead to high maintenance costs, repairing or even replacing them. This problem prompted a lot of researchers to seek alternative materials with characteristics better than steel to be used in construction. GFRP bars, which are fibers with high resistance immersed in a polymer resin matrix, with a high tensile resistance and also resistant to corrosion, emerged in the 1990s as an alternative to replace steel rods. The use of GFRP is increasingly accepted by the countries, which are trying to create or adopt special codes for their use in building structures.
      This paper will take a quick look over GFRP materials and their mechanical properties, but also will aim to provide some ideas on the study of concrete members reinforced with GFRP bars and their design based on SLS method as it rapresents the most problematic one, focusing on deflections of GFRP reinforced beams.

    • Preparation and adsorption properties of mixed zinc-calcium phosphates

      pg(s) 337-338

      Here we present data on the preparation and adsorption properties of mixed zinc-calcium phosphates in aqueous dispersions. The phosphates were prepared by co-precipitation from aqueous solutions followed by autoclaving. The effects of various Ca/Zn initial molar ratios and the type of Ca- and Zn-precursor salts (chlorides and acetates) on the structure, morphology and adsorption properties of the obtained phosphates were investigated. Preliminary data on the adsorption of methylene blue indicated that the as obtained mixed zinccalcium phosphates are promising candidates for application as adsorbents.