The article is devoted to the analysis of the main parameters (pressure, power, torque, and speed) of the electrohydrostatic drive of ground-based transport and technological complexes, which include roadbuilding equipment.The authors develop a design algorithm and obtain dependencies characterized in the operation process of the specified drive type on the basis of a compiled method for calculating the basic parameters of hydraulic components that are part of an electrohydrostatic drive. These criteria include the drive’s ability to precisely process input signals; speed of rod travel at a specified load; total operating coefficient; unit power.The purpose of this calculation method is to develop an efficient electrohydrostatic drive for road construction machines that combines the advantages of hydraulics (high power, tremendous force with small components and easy reversing) with the flexibility of electronics, which allows positioning of the working parts of these machines (bucket, arm, excavator boom, manipulator, grader or bulldozer blade and the rotation of road roller rollers) with an accuracy of millimeter in fractions for a second.The combination of analytical and numerical methods allows designing a prototype (the digital model) of this drive with its main characteristics, and then simulate the entire system, studying the flows inside the pump and channels, as well as conducting thermal analysis to assess the heating of the liquid and the motor. An electrohydrostatic drive is a complex system that requires consideration of many factors. The article focuses on the optimal selection of hydraulic components (pumps, hydraulic motor), which are selected depending on the parameters of the electric motor of the drive.The research is aimed at establishing a basis for further experimental methods, which are conducted to validate theoretical (analytical) data and develop methods for diagnosing and monitoring electrohydrostatic drive. Experimental methods are used to determine the rigidity of the drive, the removal of amplitudefrequency characteristics and the measurement of currents and pressures in various operating modes.
In the design vertical scroll compressors, engineers often need to calculate an oil pump that influences the compressor’s features, performance and reliability. The article presents the first research stage for developing the method for calculating such pumps: development of an experimental method for investigating the oil pump; comparison of the physical experiment using the developed method with known patterns; testing the influence of the angle of the inlet nozzle on the pump’s performance.The authors analysed the publicly available materials and selected the structural elements that affect the pump or which effect needs to be checked. Moreover, the authors developed an experimental test bench and a method of conducting the experiment, which allowed considering the design features of the pump: the diameter of the channel; the diameter of the nozzle opening; the shape of the nozzle; the frequency of rotation of the shaft.The error analysis reveals that the experiment's relative error is less than 3 %. Based on experimental data, the following dependencies are formulated according to the developed method: there is an inverse dependence of the pump pressure from the ratio of the hole radius at the pump outlet to the radius of the pump duct; there is a quadratic dependence of the pump pressure on the speed. These dependencies are consistent with the known data, which leads to a conclusion about the adequacy of the developed methodology and its applicability in further studies. Moreover, the authors also verify that the shape of the nozzle does not affect the pump’s performance. The results of the experiment presented in the article can be applied for verifying mathematical models of scroll compressors.
The aim of the research is to explore the potential for enhancing heat transfer and reducing hydraulic losses in piping systems by employing structured surfaces.An evaluation of the thermal-hydraulic performance of rectangular riblets with a height of h = 1 mm and a height-to-width ratio of h/t = 1.1 is performed in comparison with a smooth surface and surfaces with equivalent sand-grain roughness (heights of 0.2; 0.3; 0.4; and 0.5 mm) under fully developed turbulent flow conditions at a Reynolds number of Re = 20 000. The authors conduct the research basing on CFD simulation results by the Ansys Fluent 19.1 R1 with periodic boundary conditions.The results show that, unlike other surface types, the investigated surface with rectangular riblets demonstrates high thermal-hydraulic efficiency among all considered pipe surface forms (86 % higher compared to the smooth surface). Therefore, the research clearly demonstrates the high potential for the widespread application of riblets in thermal-hydraulic systems.
The article is devoted to the study of the optimal use of a hybrid energy system, including solar and wind installations, a diesel generator, as well as a geothermal heat pump, to provide electricity and hot water to a medical center located in the city of Salmiya (Syria). This region is remote and is experiencing an acute shortage of electricity.The system was modeled and optimized using HOMER PRO software. The calculations took into account a variable daily load of 60 kWh and a peak power consumption of 5.9 kW. Solar and wind sources provide the base load, while a diesel generator is used during periods of low generation. The geothermal heat pump provides hot water supply with high energy efficiency. The study analyzed the technical and economic efficiency of the proposed solution. The results show that using a hybrid system can significantly reduce operating costs and increase the reliability of energy supply in remote regions.
The article describes the procedure of the system assessment of air temperature of gas turbine compressors operating at linear stations of natural gas compression of gas pipelines in the southern regions of the Russian Federation.Analysis of statistical data shows that the operation of a number of centrifugal superchargers in the summer does not meet the regulatory and technical requirements of the gas industry, leading to abnormal operation of power machines and equipment. Therefore, the authors propose to cool the air before it is supplied to the gas turbine engines in a special system of absorption refrigeration machines. This additionally expands the functionality of gas turbine units, providing deep air purification, reducing natural gas pressure loss, preventing the entry of various precipitation into the engine, and significantly reducing noise levels.The article proposes and describes the operation of an original functional scheme that ensures efficient atmospheric air intake for the normal operation of gas turbine gas-pumping units during the summer season in the southern regions of the country. Moreover, the authors present new results of experimental studies of air cooling parameters in absorption refrigeration machines. The article also demonstrates a numerical example of analyzing the parameters of compressor stations with gas turbine units based on DG-90L2.1. The research also presents the dependence of the gas turbine engine power on the air temperature and the dependence of the gas compressor unit performance on the power.The experimental results at the compressor station confirm the preliminary calculations of the efficiency of the new gas turbine unit with an air cooling system and prove the necessity of its installation.
The paper considers the investigation of quartz sand as a filter material for water treatment systems of heat supply installations and to the development of quantitative criteria for forecasting its service life. The quartz sand filter is transformed into a composite material covered with aluminum and iron oxides, which are formed because of adsorption and deposition of ions from the source water during operation.With the methods of electron microscopy and energy dispersion analysis it has been found that when a filter is operated on source water with an Al ≈ 0.58 mg/l and Fe ≈ 0.44 mg/l, there is a significant change in the microlattice surface of the sand particles with the development of the micropore. The authors established that the achievement of mass proportions of aluminum and iron in quartz sand of the 11.78 and 7.11 % order is an indicator of the maximum capacity of the filter adsorption and a justification for planning its replacement.The proposed approach enables a transition from a calendar‑based maintenance schedule to a predictive management of the filter’s service life, prevents the exceedance of permissible concentration limits of contaminants in network water and the optimization of costs for water preparation.
Analytical review provides a comprehensive and systematic examination of scientific literature and regulatory documents published over the past five years (2020–2025) addressing the critical issue of electromagnetic interference from overhead power lines on the corrosion reliability of buried main pipelines.The paper categorizes and analyzes research across several key areas: the fundamental mechanisms of inductive coupling between alternating current sources and pipeline networks; the specific phenomena of alternating current induced corrosion and its distinction from direct current corrosion; the detrimental effects of induced alternating current voltages on the performance and effectiveness of cathodic protection systems; and the advancement of computational modeling techniques and risk assessment methodologies for predicting interference levels and corrosion likelihood. Key achievements in the field of negative impact standardization are identified, including the establishment of threshold alternating current density values for corrosion initiation and methods for its assessment. However, significant unresolved challenges persist, particularly the absence of universal, validated predictive models capable of accurately simulating complex field conditions involving heterogeneous soil structures, dynamic load variations from traction networks and high-voltage power lines, as well as the presence of coating defects and uneven deterioration of insulating coatings. Furthermore, the synergistic effects of combined alternating current and direct current interference over the long term remain insufficiently understood.Based on the synthesized analysis, priority directions for future research are formulated, emphasizing the necessity for developing intelligent, adaptive protection systems that integrate real-time monitoring of critical parameters, employ probabilistic risk-based approaches for integrity management, and leverage digital twin technologies to enhance the operational safety and corrosion reliability of energy transportation infrastructure.
The article discusses the structural features of low-consumption pump units of rocket and space modules: correction and detonation braking engines of spacecraft; pumps of auxiliary energy systems (supercharging, gas generation, systems for providing thermal regimes of aircraft, etc.).The main features of such pumps are low working rates (V/ω < 5 ∙ 10-7 м3); small dimensions of the flow path (< 0.1 m); low power (< 1 kW); high speed (up to 100 000 rpm). Open impellers are widely used in the design of impellers, which has determined significant difficulties in balancing power losses, considering the fact that the hydraulic and mechanical losses of the wheel do not have physical boundaries separating the relative movement in the flowing part of the impeller and the circumferential power losses in portable motion relative to the stationary wall of the pump housing. The traditional method of balance testing for closed wheels involves replacing the impeller with a “false” wheel with an identical boundary contour of cylindrical surfaces. In the case of open wheels, the authors propose a methodological technique for measuring the torque element by element on a fixed pump housing.The constructive implementation of a special meter in a balancing suspension required significant costs in the development of methodological and computational support for testing. These modifications resulted in changes to the relations in the mathematical power balance model, as well as the calculation and simulation algorithms for the low-flow centrifugal pump.As a result of testing, the resulting coefficient value for open-type impellers of the low-flow pump lies in the range of 0.8 to 0.9, which is slightly higher than the values for closed-type impellers.
Unique elements of the working processes of a low-speed piston compressor, not typical for high-speed piston machines, are considered. It has been experimentally proven that under operating modes with an elevated gas temperature at the inlet of a low-speed compressor (above the temperature of the cooling medium), a noticeable decrease in the gas temperature is observed during the suction process. That is, the first part of the cycle in the stage, the gas is cooled, and the beginning of the compression process will occur at a lower temperature than the gas temperature at the standard suction point. In addition, the assumption that when a low-speed compressor operates on refrigerants, operating modes in the wet steam region are possible, in which condensation of the working fluid is observed at the end of the compression process, has been experimentally confirmed. Such operating modes can be used in compact low-capacity refrigeration machines with a decrease in the weight and size parameters of the condenser unit. The conducted studies have shown the need to verify the calculation methodology for the types of piston compressors considered in the article and to refine the latter taking into account the features of the working processes of low-speed piston machines
The issues of applicability of well-known semi-empirical methods for calculating the operating processes of low-speed reciprocating compressors for the theoretical study of these processes in the field of wet steam are considered. It is shown that there are significant uncertainty factors in such calculations, suggesting the need to create new semi-empirical calculation methods and the inapplicability of existing ones. The latter is determined by the lack of reliable experimental results, both in terms of the empirical dependencies used to determine the instantaneous heat transfer coefficient in the flow part of a low-speed reciprocating compressor, and in terms of verification of the obtained computational and theoretical results. It is shown that the use of simplifying assumptions such as the absence of leakage through leaks in the working chamber; the constancy of the heat transfer coefficient in the cylinder during the compression process; the equality of the temperature of the cylinder mirror and the boiling point of the working fluid; the calculation of the heat transfer coefficient based on unverified empirical dependencies obtained for other technical facilities, and a number of others are unacceptable, since they lead to unacceptable results. At the same time, given the theoretical attractiveness of the issue under consideration, it can be assumed that in the future a wide range of experimental and theoretical studies of low-speed reciprocating compressors workflows in the field of wet steam, including those aimed at determining empirical dependencies for calculating heat transfer coefficients in the flow part of the low-speed reciprocating compressors stage.
The gerotor screw compressor with internally meshing rotors is an innovative type of machines of the volumetric principle of compression of various gas media, which has a significant potential for expanding the applications of screw compressor technology. The main component of this compressor model is an internally meshed screw pair, the methodology of profiling of which has remained insufficiently studied. The paper presents a computational model for the operating element profiling based on the theory of cycloidal meshing, including the generation of front profile coordinates and helical formations for rotors with different profile types. The article develops an algorithm for generating geometric 3D models using solid modeling software.
This article discusses complexes for the transportation, storage and transportation of liquefied natural gas, where compressors for the utilization of boil-off gas play a key role. The authors describe main features of boil-off compressors, the required parameters of reciprocating steam gas compressors, the main problems of calculating compressors in various systems, design methods for reciprocating compressors that improve the reliability of steam gas compressors to improve efficiency of liquefied natural gas storage and transportation systems.
A possible solution to the global energy crisis is to use sunlight to generate electricity. Solar cells that convert solar energy into electricity have to be reliable and cost-effective to compete with conventional energy sources. The aim of the article is to describe the different generations of photoelectric cells and the current and future technologies used in photoelectric systems. The article covers the basics of photoelectricity, including the principle of operation and basic features. All generations of solar cells are reviewed. Special attention is focuses on the efficiency of converting sunlight into electricity, used materials, and economic analysis. As photoelectric technology advances, opportunities for efficiency improvements, lower manufacturing costs, and innovation are also demonstrated. The paper analyzes the current limitations of modern photoelectric technologies and suggests possible ways to meet them based on the recent scientific developments.
Geothermal heat pumps are an energy-efficient and environmentally friendly technology applicable both in the construction of new facilities and in the modernization of existing buildings. They operate using renewable thermal energy from the Earth, which reduces the impact on the environment. The article considers theoretical and practical aspects of using geothermal heat pumps in heating systems of buildings for various purposes. The main attention is paid to the analysis of design solutions, operating principles, as well as factors affecting the efficiency of the systems, such as thermal conductivity of the soil and climatic features of the region. Various types of geothermal systems are considered: horizontal, vertical and open loops. Also provided are examples of implemented projects in climatically diverse regions of Russia (Moscow, Murmansk region, Kamchatka, Sochi). The article emphasizes the need for a comprehensive assessment of the economic feasibility of implementing systems, taking into account long-term performance indicators and regional conditions (Climatic conditions — geological and hydrological characteristics — economic factors such as the cost of electricity or fuel, the cost of labor and building materials, as well as government financial support).
The research presents the results of verification and validation of the mathematical model of the flow path transonic model NASA Stage 37 axial compressor using the data of the experiment conducted by NASA in the 1970s. The work presents the sequence of constructing a mathematical model of the flow path, as well as geometric models of the blade units. The mathematical model of the impeller blades is constructed based on the geometry of the blade airfoil obtained from the results of calculating the stress-strain state using the finite element method. When calculating the stress-strain state of the blade, the effect of gas-dynamic loads and centrifugal forces is considered. For gas-dynamic calculations, a study is conducted on grid independence with a description of the calculation method for the first near-wall layer and a justification for the choice of the turbulence model. A numerical study of the viscous gas flow in the flow path of the model stage is carried out considering the distribution of flow parameters and the position of the measurement control points according to the NASA report. As a result of numerical studies, gas-dynamic characteristics of the stage are constructed, and the distribution of flow parameters in the calculated sections along the height of the flow part is investigated. The obtained gas-dynamic characteristics based on the developed mathematical model quantitatively and qualitatively correspond to the results of NASA gas-dynamic tests. The obtained model can be used for further optimization or other calculations using the finite element method.
The study examines the fundamental technical characteristics of bladeless propulsors intended for advanced turbofan propulsion systems in multicopter unmanned aerial vehicles. The research identifies optimal aspect ratios that maximize thrust and thrust efficiency while analyzing the impact of fan radius and annular gap thickness on propulsion efficiency under constant flow rate and length conditions. The findings indicate that the most efficient configuration features a fan radius of 175 mm, a length of 150 mm, and an air mass flow rate of 0,3 kg/s, yielding an exit Mach number of 0,42. This configuration generates a thrust of 44 N while maintaining high-speed jet momentum conservation at 92 %, under a total inlet pressure of 17,800 Pa
The article considers the question of creating a criterion base of the jet ejector operating process on the basis of a closed mathematical model. The basic parameters affecting the degree of ejection and total pressure rise at the discharge from the mixing chamber of the jet ejector are determined. Finding dimensionless complexes using the modeling theory allows determining the criterion base of the operating process of the jet ejector. At full geometrical similarity, without considering heat exchange and using “natural” and “model” gas, the number of similarity criteria is reduced to Reynolds number.
The calculation of a centrifugal compressor is a complex iterative process in which various factors must be taken into account. One of these factors is the consideration of the balance piston line, which can significantly affect the performance map and efficiency of the compressor. The article considers the consideration of a two-phase overflow, its effect on the parameters of the main gas flow inside the passage. A technique is presented that makes it possible to calculate the performance map of a compressor, taking into account in each operating mode: the balance piston overflow, an increasing in the temperature of the gas at the inlet to the flow part, as well as the resistance of the pipeline to the balance piston line. This technique improves the accuracy of mathematical modeling of the flow part of a centrifugal compressor in both design and nondesign operating modes.
The article analyzes the current state of global development of low-energy plasma propulsion systems for guided small spacecraft. The aim of the research is to review the main types and constructions of electric rocket engines, to identify the problems arising in the development process affecting the energy and design features. One of the most demanded and promising directions in the field of propulsion for small spacecraft is ion engines. The use of electrical energy to create propulsion, as well as high-frequency electromagnetic radiation, allows minimizing power losses. A key advantage of plasma propulsion units is this utilization of energy in the propulsion creation process. The use of units of pneumohydraulic systems is the main way of supplying the operating body and their replacement by a wick infiltrated with organosilicon oil allows minimizing the mass of the propulsion system and increasing reliability.
The paper presents the results of tests of the NK-16ST engine with an experimental two-zone combustion chamber. The design features of the combustion chamber, the engine fuel system, the testing methodology and the results of measuring the environmental characteristics are described. The combustion chambers differed in the design of the main zone burners. Based on the results of the work, a combustion chamber version with a burner having an axial swirler at the nozzle outlet is selected. It provides low nitrogen oxide emissions compared to other tested chambers.
