Machines. Technologies. Materials.
Vol. 16 (2022), Issue 3

Table of Contents

  • MACHINES

    • Energy evaluation of a steam turbine from solar-based combined cycle power plant

      pg(s) 86-89

      In this paper is performed energy evaluation of steam turbine from the solar-based combined cycle power plant which includes analysis of each cylinder and the whole turbine. Steam turbine has three cylinders – high, intermediate and low pressure cylinders (HPC, IPC and LPC). Observed turbine is interesting because it possesses steam cooling before its expansion through the last cylinder (LPC). Due to unknown steam mass flow rates through each cylinder, for the evaluation are used specific variables. The highest specific work is obtained in LPC, while the lowest specific work is obtained in IPC. The highest loss of a specific work is obtained in LPC (29.8 kJ/kg), followed by HPC (24.5 kJ/kg), while the lowest loss of a specific work is obtained for the IPC (19.5 kJ/kg). Regardless of higher loss in specific work, HPC has higher energy efficiency in comparison to IPC (95.08% in comparison to 95.02%), while the lowest energy efficiency of all cylinders has LPC (94.92%). For the whole observed steam turbine loss of a specific work is equal to 73.8 kJ/kg, while the energy efficiency of the whole turbine is 95.00%.

    • On pressure drop and airflow directivity ability of air vents on automobile cabinets

      pg(s) 90-92

      In this study, airflow directivity ability and pressure drop values of air vents where placed on the front console of automobile cabinet were investigated with computational fluid dynamics analysis. One of the aims of these studies is the airflow performance impact of design changes on air vents. Therefore, parametric studies were conducted with diffuser structures having 3, 4, 5 blades and 16mm, 20mm, 24mm blade width and 3mm, 4mm blade thickness. These variations were created to determine the effects of the number of blades, blade width and blade thickness on air flow and pressure drop performances of automobile diffusers. The impact of automobile diffusers on thermal comfort inside of the cabinet has been detected—correlations which give pressure drop and airflow angle were obtained according to analysis results. Thus, equations giving airflow direction angle and pressure drop within specific parameters were obtained without computational fluid dynamics analysis. In this way, a faster approach was provided to reach related performance values on automobile diffuser design.

  • TECHNOLOGIES

    • Optimization of the synthesis of mesoporous titanosilicate ETS-10: Problems and unexpected difficulties

      pg(s) 93-95

      We focused on the synthesis and subsequent use of mesoporous titanosilicate ETS-10 for industrial water purification. Numerous attempts have been made to optimize the conditions and reagents used for the synthesis of the ETS-10. The main problem we faced in the synthesis of ETS-10 is the production of “pure” phase and it was related to the type of titanium source. Various sources of titanium were used – titanium tetrachloride, anatase (anatase 92% and rutile 6%), nanosized titanium dioxide (Degussa P25) etc. The use of liquid titanium tetrachloride, due to its high hydrophilicity, leads to difficulties in reproducible control of the quantities of used reagents, which leads to the formation of unwanted crystalline phases, especially if the synthesis is carried out in small volumes. In addition, the optimized by us synthesis attempts included a reduced reaction time – up to 24 hours – and lower temperatures (up to 200 oC). For comparison standard synthesis is carried out for 72 h at 230 oC. As a result of the experiments, ETS-10 with minimal SiO2 residues was obtained in 24 hours at 200 oC using nanosized anatase.

    • Technology for production of reduced yellow paving stones on the basis of modified marl clay from the Alexandra quarry, the village of Lovets, Bulgaria (Part 1)

      pg(s) 96-99

      Due to the specifics of marl clays, research to date has shown the need to stabilize these clays with respect to their critical melting point. The research is based on a previous analysis of pure raw material from marl clay, located in the area of the village of Lovets, which is modified by various additives. On the one hand, the modification is used to stabilize the ceramic mass and on the other hand, by adding various agents, the aim is to lighten the composition and obtain the required color pattern. For the purposes of production, the experimental part includes laboratory development of a scale model of yellow paving stone. The development presents the entire process of creating instrumental equipment – model making and matrix construction, and molding of finished products – pressing process for paving stones productionfrom modified marl clay. The technological cycle that can be implemented in the real conditions for yellow paving stones production will rely on the present study.

    • Application of augmented reality to the teaching process in the field of Computer Aided Design

      pg(s) 102-104

      The aim of this article is to point out the needs of the implementation of augmented reality in the educational process in the field of computer modelling. This topic addresses issues in the field of mechanical engineering, where it focuses mainly on the needs of education using innovative augmented reality approaches. With the help of modern visualization methods, all practical and theoretical knowledge of computer aided manufacturing technologies ware applied in a suitable electronic form and thus the pedagogical process was facilitated for students. This method of visualization significant supports education. As part of increasing the quality of the educational process through augmented reality techniques, the study is more interesting and focuses mainly on the development and creation of conditions for the use of such technologies in technical practice

  • MATERIALS

    • Obtaining abrasives on the base of composite Ni-P coatings for surface treatment of rock materials

      pg(s) 105-107

      The electroless deposition of Ni-P coatings is well known classic method for production of metal coatings on polymers. The addition of dispersed particles of different types and sizes to the base solution for electroless deposition significantly improves the properties of the coating by increasing its wear resistance and micro-hardness. Thereby, the metallized polymers find new and different applications. By using a device, designed and developed in IPC-BAS, tribological tests of composite Ni-P coatings deposited on substrate of polyethylene terephthalate (PET) are performed. Three types of dispersed particles (diamond (D), BN and SiC) are co-deposited in the Ni-P coatings. Their application as abrasive material for surface treatment of rock materials is evaluated. The structure, morphology and elemental composition of Ni-P coatings are characterized by SEM and EDS.

    • Temperature regime in obtaining BaTiO3-BaSnO3 system and study of dielectric properties

      pg(s) 108-110

      A system based on BaTiO3 – BaSnO3 (BT-BS) has been developed in search of highly efficient lead-free piezoelectric ceramics. The powder samples were mixed and homogenized in a ratio of 50%: 50% and 15%: 85%. From the compositions thus obtained, tablets with the presence of a PVA plasticizer were formed, which were further annealed in a furnace with a corundum backfill. The temperature regime is in two steps. Drying time up to 800oC with a delay of 1h 30min. and additional heating to 1150°C with one hour delay. The results were characterized by XRD analysis, the relative dielectric constant of the two samples was determined.

    • Monolayer FeSe Superconductor on Si(001): Electronic Structure Calculations

      pg(s) 111-113

      Iron-based unconventional superconductors have attracted intense interest after the critical temperature of FeSe was enhanced by more than one order of magnitude. This was achieved for FeSe placed on top of an insulating oxide substrate with its thickness reduced to the nanometer limit. There are numerous indications of the critical importance of specific features of the FeSe electronic structure in the vicinity of the Fermi surface. Here, we explore how the FeSe band topology changes when located on a Si(001) surface, by first-principles calculations based on the density functional theory. We determine which interface arrangement is preferred and what is the optimal distance between FeSe and Si. Our calculations reveal interesting effects of Si proximity on the FeSe band structure. Bands corresponding to hole pockets at the Γ point in NM FeSe are generally pushed down below the Fermi level. We explain these changes by a redistribution of electrons between different Fe orbitals rather than charge transfer to/from Si.