The article examines the characteristics of looped propellers compared to conventional (traditional) propellers. Numerical modeling is used to obtain integral characteristics of the main parameters and construct propeller performance curves to analyze the performance of various propeller types under various operating conditions. A comparison of conventional and looped propellers is conducted, and the comparative analysis demonstrates increased efficiency and improved cavitation performance of looped propellers across a wide range of operating conditions.

One of the key tasks in the design of high-efficiency screw compressors is the reasonable assignment of working gaps, which are subject to significant thermal deformations under operating conditions. In the presented work, the thermal deformations of the working elements of a gerotor screw compressor with internal gearing are estimated using numerical modeling methods. The study is based on sequential thermal structural analysis in the ANSYS engineering package, which includes the calculation of a stationary temperature field and the subsequent determination of thermoelastic deformations. It is established that, despite the significant magnitude of thermal deformations, their consistent direction leads to a slight resulting change in the working gaps. Based on the vector analysis of displacement fields, a method for assigning minimum safe operational gaps is proposed. The developed approach makes it possible to optimize the design of gerotor compressors by assigning gaps without the risk of jamming, which leads to increased energy efficiency.

Various options of soil temperature stabilization systems and corresponding roadbed structures consisting of a number of unified modules used for freezing wet peat during construction of temporary driveways along the trunk pipeline route are considered. The required time for freezing moist peat soil to the required depth is estimated with various layout solutions for temperature stabilization systems and roadbed module structures. Technological schemes of thermal stabilization systems are presented, design features of modules of the formed roadbed are reflected. Field of application — roadbed and systems for freezing and temperature stabilization of peat soil.  

The article examines thermodynamic characteristics of a single-stage, low-speed, long-stroke piston refrigeration compressor with a linear drive. Theoretical studies are conducted using a method for calculating the actual operating process of a single stage of such a compressor, considering account transient heat conduction processes under mixed boundary conditions. The coefficient of performance and the discharge temperature of the single-stage, low-speed, long-stroke piston compressor with a linear drive are considered as integral parameters. Condensation and boiling temperatures, the main dimensions and parameters of the stage, and the heat flux density on the outer cylinder surface are considered as independent parameters. A comparative analysis of the energy efficiency of the operating process and the temperature regime of the stage in question is performed at a boiling temperature of 203 K in a condensing temperature range of 273 K to 343 K and at various heat flux densities on the outer cylinder surface. The relations between heat flux density, ammonia boiling and condensation temperatures, and the integral characteristics of a single-stage, low-speed, long-stroke piston compressor with a linear drive, as well as the temperature field distribution across the cylinder bore and the cylinder wall thickness, was studied. The research demonstrates that a rational combination of the external cooling mode of a cylinder of a single-stage low-speed reciprocating long-stroke compressor with a linear drive and its wall thickness makes it possible to ensure a cooling coefficient value higher than that of high-speed two-stage reciprocating compressors.

The article considers the possibility of using a complex drying and cleaning unit with separate drying with active aluminum oxide and cleaning with synthetic zeolite of the NaX type in the air separation unit AK1.5, and also considers several circuit solutions for the layout of the complex cleaning unit. As a result of the calculations, the optimal scheme is selected. Such a technical solution will reduce energy consumption for the regeneration of adsorbents, and due to the optimal geometry of the adsorbers and minimal cyclicity of the processes (adsorption-regeneration-cooling) reduce the hydraulic resistance of compressed air.

The paper presents the results of a comprehensive study on the reverse engineering process of a highspeed centrifugal compressor impeller ICK KCK-01-100-1-8-А, pecial attention is paid to the complexity of reproducing a part, including the selection of a material with a significant difference in state standards and the choice of a substitute material, the selection of solder for vacuum soldering, and the technological aspects of vacuum soldering. A simulation of gas dynamic characteristics is carried out — the pressure ratio and the temperature difference, the results of which showed satisfactory results. The stress-strain state is estimated. The simulation is performed in accordance with the requirements of API 617 and INTI S.60.2–2023 standards, taking into account the MCS and TRIP speeds of the impeller. Based on the calculation results, the diagrams of the stress-strain state and the diagrams of the plastic deformation of the rotor are given. At the end of the project, the impeller is manufactured and bench acceleration tests are carried out, according to the results of which size control is performed and deformations are evaluated using flaw detection methods. It is shown that successful restoration of the impeller requires a deep understanding of many nuances. The results obtained confirm that the use of domestic analogues of materials, as well as modern methods of analysis, makes it possible to create an impeller with characteristics close to the best examples of modern technology.

Absorption refrigeration machines that use the heat of secondary energy resources and renewable energy sources for operation have found wide application in refrigeration systems in the chemical, petrochemical, textile, metallurgy and other industries. Heat conversion in absorption refrigeration machines is accomplished using direct and reverse cycles, so three external heat sources are required to generate cold: a heating source, a source being cooled (the source of the cooled object), and a cooling source. Lithium bromide absorption refrigeration machines are used to generate cold at above-zero temperatures. Many proposed cycles for lithium bromide absorption refrigeration machines have not yet been studied. The paper presents the results of a study of the parameters of a real combined thermodynamic cycle of lithium bromide absorption refrigeration machines with double-stage generation (type 3) depending on the temperatures of external sources. The cycle's efficiency indicators, heat exchanger loads, and the optimal degassing zone for an aqueous lithium bromide solution are determined. The efficiency indicators of the studied cycle, the loads on heat exchangers, and the optimal value of the degassing zone of an aqueous solution of lithium bromide were determined. A study was carried out to determine the influence of the values of incompleteness of solution saturation in the absorber and incompleteness of solution evaporation in the generator on the cycle efficiency.

In case of the wildly using of screw compressors in modern industries, the compressor efficiency improving methods’ development are actual. The main advance of the «dry» screw compressor comparing with oilinjected compressors is their compact due to the no needs huge oil system, which includes oil separation system and additional filters, which leads to improving an ecology and reducing the exploitation coast. One of the way of the compressor capacity and energy efficiency improving is developing of the rotor profile gaps’ calculation methodic by taken into account different factors determined by the compressor working conditions. The heating load on the «dry» screw compressor parts higher than on the oil-injected compressor parts, because their working conditions lead to the highest value of the discharge temperature. Therefore, it is necessary to take into account compressor rotors’ temperature fields to calculate rotors’ profile gaps correctly. This paper presents the methodic of the rotors’ temperature field calculation with the aim to reduce the rotors’ profile gaps and improve the «dry» screw compressor efficiency.  

The article examines the main causes of reduced reliability of shut-off and control equipment in condensate pipelines, which are associated with uneven flow of petroleum products transported under various operating conditions of the process equipment. The study focuses on a condensate pipeline used for transporting unstable gas condensate from the primary separation plant to the processing unit, both located at gas condensate field facilities. The subject of the study is an in-line diode element, which is proposed for integration into the condensate pipeline to reduce both pressure drop and shock loads on the shut-off and control equipment. The feasibility of using an in-line diode element is analyzed using numerical modeling of petroleum product flow by a modern software package. The obtained results are of practical value to engineering and technical specialists at gas transportation companies, pipeline system designers, and equipment developers for the oil and gas industry.

В работе представлены результаты 3D-сканирования геометрии проточной части центробежного компрессора ТС-21, а также результаты численного исследования течения вязкого газа в проточной части компрессора. Построены газодинамические характеристики компрессора на основе отсканированной оригинальной геометрии проточной части. Проведена оценка использования реверс-инжиниринга в энергетической и авиационной промышленности. Было выявлено, что помимо использования 3D-сканирования для лопаток рабочих колес необходимо проводить дополнительные операции, так как входные кромки лопаток получались более острые в результате погрешности обработки, вследствие чего возникает ударное обтекание и некорректное проектирование, модернизация промышленного и авиационного динамического оборудования.

The article examines the physical conditions of the thermosphere in the field of very low orbits, analyzes the features of free molecular flow around spacecraft. Special attention is paid to models of the interaction of a molecular stream with the surface of a spacecraft, including issues of energy and momentum accommodation. An analysis of the physical parameters of the thermosphere in very low Earth orbit is presented, including the distribution of density, temperature, and chemical composition, as well as their dependence on solar and geomagnetic activity. The theoretical foundations of the free molecular flow regime are analyzed, where the equations of particle motion and the conditions of reflection from the surface are considered. Methods of experimental and computational determination of energy accommodation coefficients are considered. The influence of atmospheric parameters and surface characteristics on the aerodynamics of ultralow orbiters is analyzed.

Electric propulsion rocket engines are widely used on board modern spacecraft. To ensure the efficient use of such engines, it is important to diagnose the plasma plume of the engine. Measuring the parameters of the plasma plume is used for the determining its efficiency, and calculating the impact of the engine plasma plume on the onboard devices of spacecraft. One of the most important tasks is to study the charge state composition of the ions in the plasma plume of an electric propulsion. The article presents a computational study of the method for measuring the charge composition of the plasma plume of a Hall effect thruster. The operation of probes of various geometries in plasma plume of the Hall effect thruster with discharge voltages from 100 to 2000 V, the propellant of which is xenon, is simulated. Using calculations, the features of this technique are shown, and the optimal geometry is selected for studying the fraction of two-charge ions in the Hall effect thruster.