V. A. Pronin, P. A. Belov, V. A. Tsvetkov, M. H. Dzhumaev, P. A. Egorov
Profiling of operating elements of gerotor screw compressor
DOI: 10.25206/2588-0373-2025-9-2-5-12
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.

Keywords: gerotor screw compressor, operating elements, rotors, internal meshing, volumetric compression, front section, screw formers, CAD-model.

V. L. Yusha
On the applicability of semi-empirical methods for calculating the operating processes of a single-stage long-stroke reciprocating compressor in the sphere of wet steam
DOI: 10.25206/2588-0373-2025-9-2-13-24
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.

Keywords: reciprocating refrigeration compressor, low-speed long-stroke stage, operating processes, semi-empirical calculation method, wet steam, heat transfer coefficient, refrigeration coefficient, discharge temperature

S. S. Busarov, A. V. Nedovenchany, R. E. Kobylskiy, I. S. Busarov
Experimental study of the features of the working processes of low-speed intensively cooled long-stroke piston compressor stages
DOI: 10.25206/2588-0373-2025-9-2-25-32
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.

Keywords: long-stroke piston compressor stage, working processes, experimental studies, increased suction temperature, condensation of the working fluid, indicator diagrams, uncertainty.

A. D. Vanyashov, D. V. Bychkov, A. V. Belikov
Obtaining gas dynamic characteristics of the circulation centrifugal compressor of hydrogen-containing gas based on the analysis of actual operating modes
DOI: 10.25206/2588-0373-2025-9-2-33-40
The analysis of actual operating modes of a centrifugal compressor providing circulation of hydrogencontaining gas in a reactor block of catalytic isomerization of metaxylene and ethylbenzene into orthoxylenes and paraxylenes has been performed. The technological process, as well as the state and properties of the catalyst in the reactor block determine the concentration of hydrogen and the molecular weight of the gas mixture, which, accordingly, leads to the need to regulate the operating modes of the centrifugal compressor by throttling at the suction. The calculation method of the gas-dynamic characteristics of the compressor when regulating by throttling at the suction has been clarified, taking into account the features of operation in the circulation mode, namely, the change in pressure before the throttling device. It has been established that when regulating by throttling at the suction of a circulation centrifugal compressor, the function of the pressure ratio on the volumetric productivity changes. It is established that the actual surge limit is shifted relative to the theoretical limit to the left, into the zone of the descending part of the pressure characteristic

Keywords: centrifugal compressor, gas-dynamic characteristics, suction throttling, a hydrogen-containing gas, surge boundary, operating modes, operating points.

A. N. Liubimov, A. G. Lakhman
Methods of considering the balance piston line for calculating a centrifugal compressor performance map
DOI: 10.25206/2588-0373-2025-9-2-41-47
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.

Keywords: centrifugal compressor, passage, performance map, balance piston, balance piston line, gas dynamic calculation, overflow. 

Deeb Ali, A. N. Doroshin, Deeb Muhammad
Review of the application of geothermal heat pump systems in buildings
DOI: 10.25206/2588-0373-2025-9-2-48-60
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 fr om 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).

Keywords: geothermal heat pump, ground loop, ground heat transfer coefficient, open loop, horizontal drilling, vertical drilling, heat pump efficiency coefficient, required heat load.

A. S. Zolotukhin, L. N. Marenina, A. A. Drozdov, E. Yu. Zolotukhina, A. M. Yablokov
Verification of mathematical model of transonic axial compressor stage  
DOI: 10.25206/2588-0373-2025-9-2-61-70
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.

Keywords: NASA Stage 37, numerical modeling, model stage, axial compressor, validation, CFD, sound speed, gas-dynamic characteristics.

A. V. Burakov, A. A. Kotlov, L. G. Kuznetsov
Features of development of boil-off reciprocating compressors used in complexes for storage and transportation of liquid natural gas
DOI: 10.25206/2588-0373-2025-9-2-71-77
This article discusses complexes for the transportation, storage and transportation of liquefied natural gas, wh ere 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.

Keywords: compressor, liquid natural gas, boil-off gas, development, calculation, efficiency/

V. I. Kuznetsov, I. O. Kuznetsova, D. D. Shpakovskiy
Criteria base of the jet ejector operating process
DOI: 10.25206/2588-0373-2025-9-2-78-85
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.

Keywords: criterion base, jet ejector, degree of ejection, degree of pressure rise, kinetic energy, dynamic viscosity, velocity difference.

P. A. Bryzgunov, V. A. Grigorov, L. E. Grishin, E. A. Ivanova
Study of the small multicopters bladeless propulsors characteristics
DOI: 10.25206/2588-0373-2025-9-2-86-93
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.

Keywords: Coanda effect, Dyson fan, unmanned aerial vehicles (UAVs), thrust, small aircraft, engine, bladeless propulsion.

I. V. Kolganov
Review of electric rocket engines for small spacecraft propulsion systems
DOI: 10.25206/2588-0373-2025-9-2-94-103
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.

Keywords: ion engine, Hall effect, small spacecraft, propulsion system, anode, cathode, plasma, electric rocket motors, electric field, magnetic field.

A. N. Markushin, A. V. Baklanov
Test results of a two-zone combustion chamber in a gas turbine engine
DOI: 10.25206/2588-0373-2025-9-2-104-109
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.

Keywords: dual-zone combustion chamber, gas turbine engine, burner, testing, concentrations of harmful emissions, nitrogen oxides, carbon monoxide.

T. A. Duyun, Elmnifi Monaem Hamad
Comprehensive techno-economic analysis of solar photoelectric materials of different generations
DOI: 10.25206/2588-0373-2025-9-2-110-120
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.

Keywords: solar energy, photoelectric cell, solar panels, photoelectric elements, photoelectric effect, generations of solar photovoltaic materials, development of photovoltaic technologies, productivity, efficiency.