The article aims at developing a digital model of a lathe and the related technology for its assembling. The study is based on analyzing the service purpose and technological capabilities of modern modular machine tools, justification and development of the machine tool design according to the specified production conditions, and development of a technological process for assembling the proposed modular machine tool. The geometric modeling techniques and the design documentation were implemented to justify the rational choice of design parameters of the machine tool design and its spatial model. The proposed approach also considers structural elements and the relationships between them. As a result, a conceptual approach was proposed to design technological processes of lathe assembly with a wide range of technological capabilities. It allows implementation of the up-to-date strategy from idea to finished product at industrial enterprises. The practical significance of the obtained results for the machine-building industry is in the proposed practical recommendations for developing the technological process for assembling lathes.

To produce competitive products, it is necessary to consider their permanent modernization and adaptation to the emerging needs of a consumer. This feature of up-to-date production inevitably leads to design complexities. As a result, the complexity of a technological assembly process increases, which is a new challenge for enterprises. Simultaneously, in most cases, assembly operations are performed manually due to the complexity or impossibility of automating the assembling process for an extensive range of products. This fact is due to the insufficient flexibility of automation systems. Remarkably, this approach has significant drawbacks, i.e., low productivity and risk of chronic diseases. To solve this problem, the use of collaborative systems was proposed. Such systems have the advantages of both humans and automation tools. As a result, industrial robots can be applied as automation tools. However, when using industrial robots next to workers, the safety requirements are significantly increased since the infliction of industrial injuries is unacceptable. After considering all the above, the article deals with a new scientific and methodological approach to designing security systems of collaborative production cells and their design and effectiveness verification.

Індекс рубрикатора НБУВ: Л111.62-51-031 + Л113.24-31

Рубрики:

Фільтрація

Іонообмінні процеси розділення і очищення

Шифр НБУВ: Ж101239 Пошук видання у каталогах НБУВ 

Investigating the behavior of asphalt concrete at low loading frequency is essential to understand the thermal fatigue damage due to cyclic day-night temperature cycles, where the loading frequency is usually very low. This study determines some properties (e.g., fatigue damage, dissipated energy, and stiffness) of asphalt concrete beam samples at a low frequency of loading using four-point bending test apparatus. Results show that fatigue damage is more significant at a lower frequency of cyclic loading and the number of cycles at failure becomes stable at a frequency equal to or lower than 0,01 Hz. The concept of initial stiffness at the 50th cycle of loading is inappropriate at a low frequency of loading as the stiffness reduction with a number of loadings is so considerable at a frequency of loading. In addition, the dissipated energy per loading cycle decreases with a decrease in loading frequency.

The article is devoted to studying the contra-rotating stages with different impellers and blade discs. Determining the reduction of volumetric losses by modeling the contra-rotating stages in the software package ANSYS CFX. The work aimed to create and study the flow and characteristics: semi-open, closed impellers, and blade discs. As a result of the work, the following contra-rotating stages were determined and compared: the semi-opened impeller with the semi-opened blade disc; the closed impeller with the closed blade disc; the semi-opened impeller with the closed blade disc; the closed impeller with the semi-opened blade disc. As a result of research, fluid flows in contra-rotating stages and their characteristics in the form of pressure and efficiency were obtained. According to the obtained data, the expediency of using contra-rotating stages as a working body of the pump is written.

The article is devoted to a pilot study of the reverse-bladed pump. The characteristics of the reverse bladed pump are the identical parameters on flow, the head, power, energy efficiency on direct and the return operating modes (at rotation of a rotor of the pump both in one and to the opposite side). The model reversible axial pump with two impeller versions was tested on an experimental bench. The impellers were distinguished by the shape of the profile in the blade sections. The model reversible pump was structurally a reversible axial impeller placed in a cylindrical chamber. Studies were carried out at different angles of rotation of the impeller blades. The power characteristics of tested versions of the pump (impeller) at the design and under loading (unstable operation) modes are given. Low efficiency of the tested versions of the reversible pump compared to the conventional axial pumps is noted, primarily due to the strong influence of the secondary gradients of the pressure factor. The second reason is the profile separation of the flow from the blade surface, to which the tested reverse pump screens are predisposed.

Solving the hydroelastic problem by using Ansys System Coupling (Mechanical and CFX) for floating and fixed rings of a deformable annular seal made it possible to analyze the influence of the cylindrical shell thickness, the inlet and outlet edge dimensions, inlet pressure, and shaft radial displacement on the hydrostatic pressure distribution and the clearance value on length, leakages, stress-strain state, and radial force. The analysis of static stability at an inlet pressure of 10 MPa for the basic seal design showed that the static radial force in the range of radial movements of the shaft from 0 to 50 % of the clearance is centering, even though the inlet part of the seal clearance has a confusor, and the outlet part has diffuser form. However, the dynamic coefficients of the fixed sealing ring have a negative value of direct stiffness but positive values of direct and cross-coupled damping and cross-coupled stiffness. Verifying computational 2D and 3D models with experimental results from the literature showed that the maximum relative error does not exceed 10,7 % for the hydrostatic pressure, 18 % for the clearance, and 8,6 % for the leakage value. Simultaneously, according to the trend, all calculated dependencies are identical to the experimental results.

Індекс рубрикатора НБУВ: З368

Рубрики:

Теплообмінні апарати

Шифр НБУВ: Ж101239 Пошук видання у каталогах НБУВ 

The need to develop effective technology for the treatment of liquid effluent of dye-intensive industries such as textile, rubber, paint, and printing is synonymous with the need to save the life-threatening risks posed by these carcinogenic and mutagenic pollutants on human and aquatic lives. Isotherms of adsorption of crystal violet (CV) on activated carbon (AC) synthesized from rice husk are presented herewith to elucidate the mechanism of the adsorption process of crystal violet dye contaminated water on rice husk activated carbon. AC was synthesized from rice husk via a phosphoric acid activating agent at low temperatures. Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) isotherm studies were employed. The mean square values for Langmuir, Freundlich, Temkin and D-R models were 0,98, 0,91, 0,94, and 0,63, respectively. Analysis of the isotherms of the adsorption of crystal violet sorbate on the synthesized rice husk sorbent suggested that the adsorption process proceeded via a homogeneous monolayer mechanism. Langmuir isotherm gave the best fit of the adsorption process. Langmuir isotherm constant was -1,40 l/mg, and the equilibrium adsorption capacity was 13,53 mg/g.

The use of processing units for the production of mineral fertilizers in the industry in today's market requires improved product quality and increased productivity. As a result, there is a need to change the design of existing units or some structural elements. Rotary vibroprillers, having a relatively simple design, can be of different designs that directly affect the productivity indicators mentioned above. The study considers the influence of the shape of the basket bottom on the quality of the rotational vibroprillers. After using the governing equation of prills motion in the airflow, a program was developed for automatic control of the rotational speed of the priller based on changes in melt loads. It is established that the size of the spray swath can be changed by varying the rotational speed of the priller. There is a tendency to affect the vibropriller performance by controlling the rotational speed and shape of the basket bottom without performance degradation.

The article describes the prospects for experimental research of liquid-vapor jet devices with adaptable geometry of the flow part of the primary flow nozzle. To formulate the research objectives, a critical analysis of state-of-the-art studies was conducted among native and foreign scientists studying two-phase jet devices. As a result, of the literature survey, we saw that the working process of the two-phase jet devices, which include liquid-vapor jet devices, is quite complicated to study. So, the achieved results of theoretical studies require clarification and the conduction of additional experimental studies. The article provides a description and experimental research method on the liquid-vapor jet devices with a replaceable diffuser part of the primary flow nozzle. The program and the method contain the range of changing operational parameters while conducting experimental studies. The functional scheme of the experimental scheme and the devices to control and measure pressure in the critical points of the scheme are proposed.

The effect of the hydrochlorofluorocarbon (HCFC) and hydrofluorocarbon (HFC) refrigerants on the environment through the attack of its halogen contents-chlorine and fluorine, on the ozone layer and the toxic nature of such refrigerants, has paid the attention of researchers to work towards getting suitable alternatives using hydrocarbons (HC) or its blends with HFC refrigerants. This study was centered on getting a suitable retrofit of R-134A with a good coefficient of performance (COP) and low global warming potential (GWP) using the blends of R-290 and R-600 HCs for use in refrigeration systems. An experimental testing rig was developed by assembling various measuring devices to the operational points of a vapor compression refrigerator. A mixture design was developed using the simplex lattice design (SLD) of design expert software 11,0. The response variables considered were COP and GWP. The experimental design was meticulously followed using 1kg for each refrigerant run, and the temperature and pressure values at the operating points were noted. From the results obtained, blend A had the highest COP of 2,5 and the highest GWP value of 3,93. Blend D had the lowest value of C.O.P. of 1,33, while blend B had the lowest value of GWP of 3,51. Also, the optimal blend was achieved at a mixture factor of 59 % R-290a and 41 % R-600. The response values obtained at this optimal mixture level were COP-2,05182 and GWP - 3,59. Therefore, the optimal blend obtained would be a better retrofit to R-134a and could be used in refrigeration systems.

The study aims to define the potential and technological aspects of the digestate treatment for its application as a biofertilizer. Life cycle assessment methodology was used in terms of digestate quality management. The potential of nutrients, organic carbon, and useful microelements in the digestate allows for its consideration as a mineral fertilizer substitute and soil improver. The valorization of digestate as fertilizer requires quality management and quality control. Based on the research focus, the successful soil application of digestate post-treatment technologies was analyzed. Among the different commercial options for digestate treatment and nutrient recovery, the most relevant are drying, struvite precipitation, stripping, evaporation, and membranes technology. Comparing the physical and chemical properties of the whole digestate, separated liquid, and solid liquor fractions showed that in the case of soil application of granular fertilizer, nutrients from the digestate are released more slowly than digestate application without granulation. However, realizing this potential in an economically feasible way requires improving the quality of digestate products through appropriate technologies and quality control of digestate products. To support the manufacture of quality digestate across Europe, the European Compost Network developed a concept for a pan-European quality assurance scheme.

The study discussed the use of phosphogypsum by-product waste in anaerobic digestion processes. Besides the production of biogas from plant substrate with the addition of phosphogypsum, the focus was placed on the enrichment of digestate with phosphogypsum as a mineral additive to increase the concentration of valuable macro- and microelements. The component composition of the obtained digestates was analyzed, and opportunities for additional research were determined. Research on the use of mineral additives in anaerobic digestion is considered promising. Phosphogypsum favors the quality of digestate as an organic mineral fertilizer with a higher content of mineral components. Furthermore, the contribution of phosphogypsum to plant substrate to achieve higher biogas production is not apparent, but with an impact on the component composition of biogas; however, there is an opportunity to consider the potential benefits of using the additive with another type of substrate waste for the anaerobic digestion process.

This paper aims to present a new application of TOPSIS with an automated decision-making process for the analysis of drinking water. For this purpose, the algorithm was modified with a fuzzy disjunction, and the maximal output values were set to one. The properties of drinking water, such as total dissolved solids, hardness, electrical conductivity, and cost, were the criteria analyzed in this study. These criteria were analyzed with unmodified and modified algorithms. Therefore, the modified TOPSIS was also used to optimize the parameters of the candidates. The appearance of the value of 1,0 in the algorithm's output was due to the confusion of an individual's categories of drinking water and undrinkable water. The advantage of this investigation was that, for the first time, it allowed automated decision-making to detect the drinking water in different samples and analyze them according to their characteristics. This would be important in developing new technologies for detecting and analyzing drinking water in the environment. The results of this paper can be applied in materials sciences and engineering.