Machines. Technologies. Materials.
Vol. 17 (2023), Issue 1

Table of Contents

  • MACHINES

    • The influence of steam extractions operation dynamics on the turbine efficiencies and losses

      pg(s) 3-6

      In this paper are presented results of a low-pressure steam turbine energy and exergy analysis during turbine extractions opening/closing. All possible combinations of extractions opening/closing are observed. The highest mechanical power which can be produced by this turbine (when all steam extractions are closed) is 28017.48 kW in real and 31988.20 kW in an ideal situation. For all observed steam extractions opening/closing combinations is obtained that energy efficiency and energy losses range is relatively small (from 87.56% to 87.94% for energy efficiency and from 3360.46 kW to 3970.72 kW for energy losses). Trends in energy and exergy losses (destructions) are identical for all observed extractions opening/closing combinations. Analyzed turbine efficiencies (both energy and exergy) will decrease for a maximum 1% during the steam extractions closing. Turbine steam extractions closing decrease turbine efficiencies and increases turbine losses (destructions), what is valid from both energy and exergy aspects.

    • CFD simulation of airflow through the throttle body of the air intake system applied to the Formula Student vehicle

      pg(s) 7-11

      In this paper, a simulation of their flow through the throttle valve on the Formula Student vehicle was performed throttle valve is an element that, according to the regulations of the Formula Student competition, must be present in the intake installation of the vehicle’s power unit if it is a competition in class IC. The correct design of the throttle is of great importance anchor or the power unit to work properly, but also to extract the maximum performance of the power unit itself, and thus of the competition vehicle as a whole. One of the main tasks of the throttle is to allow air to flow with as little resistance to flow as possible. For the CFD simulation in this work, ANSYS Fluent was used, which proved to be a very powerful tool in the CFD simulation of the throttle body.

    • The prospects for the use of liquefied gas in maritime transport

      pg(s) 12-13

      If a fuel mixture consisting of a liquefied gas fuel is prepared in the water transport diesel engines, i.e. the gas-diesel process occurs, where methanol is used as an explosive fuel, resulting in the reduction of the self-ignition delay period and fuel combustion duration, the limits of the working mixture combustion are expanded (hybrid combustion), and the mixture formation process is improved, resulting in an increase in the combustion speed, i.e., the complete combustion of the fuel mixture occurs during the active combustion period, and the cycle in the engine is closer to the Otto cycle, which improves the environmental and efficient indicators of diesel engine compared to the gas-diesel engine, where the diesel fuel is used as an explosive fuel.

    • Improving wellbore stability by applying drilling mud with Fe2O3 nanoparticles

      pg(s) 14-17

      Since 90% of all problems related to the wellbore instability occur during drilling through shales, which are mostly consisted of clay minerals, the filtrate from drilling mud penetrate into shale rocks and lead to their destabilization, so the industry is considering the possible application of new types of additives because conventional additives, due to their size, cannot enter in pores of shales, plug them and reduce further filtrate penetration. The oil industry in last few years turns to investigate possible application of nanoparticles because they can enter in small shale pores and plug them, thus increasing the wellbore stability. In this paper the influence of the size (50 nm and between 20 and 30 nm) and concentration (0.5, 1, 3 and 5 wt%) of Fe2O3 nanoparticles on density, rheology, API filtration, and swelling of laboratory prepared pellets in contact with mud without and with nanoparticles was determined. Due to the fact that the rheological properties are significantly increased at higher concentrations, and that smaller particles give better results with an emphasis on increasing the wellbore stability further tests should be carried out with nanoparticles Fe2O3 which size is between 20 and 30 nm in maximum concentration of 1 wt%.

  • TECHNOLOGIES

    • Study of the radial shear rolling effect on the gradient microstructure formation in technical titanium and mechanical properties changes

      pg(s) 18-20

      The work is devoted to experimental studies of the influence of radial shear rolling on the microstructure evolution of the VT-1 titanium alloy and its gradient distribution over the cross section, as well as changes in mechanical properties. In the course of the conducted studies, two different types of microstructure were obtained. At the periphery of the bar near the surface, a relatively equiaxed ultrafine-grained structure with a grain size of 300-600 nm was obtained, while in the axial zone of the bar, an oriented striped texture was obtained. The resulting structure difference of the peripheral and central zones indicates the gradient nature of the structure distribution. This type of distribution is confirmed by the results of the microhardness study over the cross section of a bar rolled to a diameter of 15 mm. The ultimate strength after deformation increased by 58%, while the elongation decreased by 15%.

    • Welding technology of martensitic steel P91 and austenitic steel 304H – State of the art

      pg(s) 21-23

      Many industries nowadays with the development of technology require joints between different types of steel due to its various benefits such as production of lightweight machine parts, production of less expensive components with acceptable properties, high strength, acceptable corrosion resistance. One of the dissimilar welding challenges is the joint between martensitic steel P91 and austenitic steel 304H due to the dissimilarities in their chemical, physical and metallurgical properties. In this paper is going to be analysed the best way of joining the two different types of steel, the proper welding technique, the choice of filler material which according to carbon content can match only to one of the steels. At the end is discussed if the welding performance can meet the requirements of high-quality weld.

    • Visualization and analysis of gear drives parameters with the help of computer-aided mathematics systems

      pg(s) 24-27

      The visualisation capabilities of the main software systems for computer-aided mathematics are reviewed. The advantages of the software system Matlab are described. The system is appropriate when visualization and analysis of engineering data are required. The author sets out to highlight the three-dimensional graphics and optimization synthesis of gear drives.

    • Basic Analytical and Geometric Synthesis of Conic Convolute Helical Surfaces of Spatial Rack Drives. Software and Graphic Study

      pg(s) 28-34

      This study treats a study oriented to the basic synthesis of the conic convolute helicoid. On the base of the elaborated mathematical model, the written equations show a theoretical possibility, depending on the basic geometrical characteristics of the designed conic convolute worm, to generate the active flanks of the helical teeth as parts of these conical convolute helicoids. Analytical dependences of the cross-section and the axial section of the conic convolute surfaces are obtained. These relations, as well as the performed studies of the graphic images of these sections, precede the process of constructing the algorithms for computer synthesis and design of these conic helical surfaces. The realized studies of the graphic images of these sections are the basis of the algorithms for computer synthesis and design of these conical helical surfaces. The appearance of singular points on these surfaces is examined, which is of particular importance for their technological synthesis. Based on the developed algorithm, a computer program for the synthesis and visualization of conic helical surfaces is realized and illustrated.

    • Design for Sustainability: A Review

      pg(s) 35-37

      Sustainability is topic of great concern since the last decade and still today does not lose of its popularity. Reason for that is that the contemporary way of living is causing great damages to the environment. Designers have been talking about changing the ways in which the products are designed in order to have sustainable product. But, for achieving sustainability many aspects need to be addressed, such as: cultural, social, economical and technological. Nowadays, we believe that these aspects are on higher level and we can talk about sustainable design.
      Every product development process starts with the design phase and this is why we believe that it is most important for making improvements of the products. In this paper we have the premise that good and appropriate design can have positive influence on the sustainability. In order to check the validity of the premise we are reviewing paper dealing with sustainability, eco design, and engineering materials.

  • MATERIALS

    • Eco-inspired synthesis and photocatalytic application of novel ZnO nanoparticles from peel extract of banana

      pg(s) 38-39

      The time being, one of the greatest concerns is the environmental pollution. Nowadays, various dangerous compounds reach to the air, soil and water. Pharmaceuticals, such as 17α-ethinylestradiol (EE2), are one of the most emerging pollutants in water ecosystems. Hence, powerful but green approaches should be developed in order to completely remove the pollutants. Heterogeneous photocatalysis is a sustainable and efficient process in the removal of organic pollutants, such as pharmaceuticals. ZnO is one of the most commonly used semiconductors but also possess some drawbacks. In this study novel synthesis pathway of ZnO nanoparticles from banana peel extract was
      obtained. Besides, the photocatalytic efficiency of the newly synthesized ZnO was examined in the degradation of EE2. Both the eco-friendly ZnO nanoparticles, as well as pure banana peel extract showed a promising photocatalytic activity in the degradation of EE2 under simulated solar irradiation (SSI). Namely, EE2 was completely degraded after 60 min of SSI.

    • Effect of solanine on corrosion of steel 3 in lactic acid

      pg(s) 40-42

      The object of research – the natural glycoalkaloid solanine as a possible inhibitor of acid corrosion of steel St3. Modern data on the structure and physico-chemical properties of solanine, such as amphiphilicity, surface activity, basicity, characteristic of modern organic corrosion inhibitors, are presented. The basic concepts are defined: basic nitrogen, solanine amphiphilicity, mass and volume corrosion indicators, corrosion inhibitor, degree of protection, corrosion inhibition coefficient. The literature data on the corrosive activity of lactic acid (MC) are presented and characterized.

    • Complex electrical impedance and dielectric spectroscopy studies of BaTiO3- BaSnO3 ceramics obtained via sol-gel method.

      pg(s) 43-45

      In view of the practical applications of the piezoelectric ceramics produced from barium titanate (BaTiO3) and barium stannate (BaSnO3), (the BT-BS system), the dielectric behavior of such materials was studied. The starting components (powder of both BaTiO3 and BaSnO3) were synthesizedand structurally characterized in аdvance. Bulk samples of BT-BS (formed as tablets with addition of PVA plasticizer) were prepared using the sol-gel method by varying the BT-BS composition percentage. The samples were characterized by complex electrical impedance spectroscopy and dielectric spectroscopy in the frequency range from 0.1 Hz to 1 MHz. As compared to BaTiO3, an increase with at least 50 % was measured for the value of the room-temperature dielectric constant (e′ – the real part of the dielectric permittivity) of the BT-BS samples containing 15 wt% BaSnO3. In contrast, the 50 wt% content of BaSnO3 led to a decrease of ′ value of BT-BS by a factor of 3.5, due to relatively low e′ value of BaSnO3. Analyses of the frequency spectra of complex electrical impedance and complex dielectric permittivity revealed the dielectric relaxational behavior of the BaTiO3+BaSnO3 system. The results obtained for ′ of BT-BS dielectrics as a function of the temperature were correlated with the data from structural studies. In particular, a specific enhancement of e′ was observed in temperature range around 120C for the BT-BS samples containing 15 wt% BaSnO3. Corresponding conclusions were done. The effects observed show that the synthesized BaTiO3-BaSnO3 ceramics are promising materials for piezoelectric and dielectric applications, e.g., in energy storage devices.

    • Study of aluminum content on the structure and phase composition of synthesized aluminum-matrix composites

      pg(s) 46-49

      The work shows that there is no significant change in the phase composition of composites with a change in the synthesis temperature, so we can use pre-synthesized heats at a temperature of 950 oC to obtain hot-stamped aluminum-based composites. The best characteristics of the synthesized titanium carbide were obtained for the composition 45Al-11C-44Ti (%, wt.). The lattice period of titanium carbide for this sample is 0.4324, and the particle size of titanium carbide formed after sintering is 0.8-1.5 μm. The influence of the component composition of the initial charge on the features of the structure and the phase composition of the thermally synthesized heat of the Al-C-Ti system was established.