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Abstract: Based on hydraulic mathematical modeling, calculated dependencies are obtained to determine the parameters of seepage oozing out onto an earth slope. The proposed dependencies gave an acceptable fit (up to 5 – 6%) with experimental data obtained with the EGDAmethod and the exact solution for the vertical slope. The article also critically analyzes the existing similar formulas. PubDate: 2024-07-25
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Abstract: In traditional hydrodynamic automatic control systems (ACSs) of power steam turbines (STs), the protection scheme (PS) of the turbine unit is used according to the rotation frequency “1 of 2.” In modern electrohydraulic ACS (EhACS), a “2 of 3” PS or an “n – 1 of n” PS with a large number of channels is used, enabling the implementation of channel-by-channel testing of the PS and identifying the failure of one of the channels without stopping the ST. In EhACS, the PS is implemented in an electrohydraulic device-a protection unit (PU). Valve PU is preferable over spool PU in terms of cost and complexity of production. In valve PU, in case of the failure of one of the channels during an emergency stop, the residual pressure remains in the protection line the fewer the valves (and, accordingly, channels) in the PU. In the case of ST of the Ural Turbo Engine Plant, the residual pressure of the three-channel PU was unacceptably high (because of the characteristics of the automatic lock of the stop valve [ALSV]). During the reconstruction of the ST ACS of the Ural Turbo Engine Plant, five-channel PUs were used. ALSV reconstruction is thus proposed, which allows the use of three-channel PU on the ST of the Ural Turbo Engine Plant. This leads to an increase in the reliability of the PS operation by reducing the number of channels (and valves) of protection from five to three without increasing the cost of reconstruction of the ACS as a whole. PubDate: 2024-07-16
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Abstract: Murmansk oblast’ is briefly characterized. The stages of development of the Kola Power System, the consistent increase in its capacity, and changes in the mix of generating capacities are considered. The main performance indicators of the Kola NPP, Apatity and Murmansk CHPs, 17 HPPs, and Kola WPP are given. The power grid facilities of the power system are briefly described. Possible directions of further development of the electric power industry in the Murmansk region are proposed. PubDate: 2024-07-16
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Abstract: In this work, we present a conceptual framework for the development of relay protection and automation technologies, as well as dispatch and process control, for electric power systems. This concept allows flexible changes to be implemented in the set of functional tasks performed throughout the entire period of operation of power distribution networks, staged modernization of power facilities, and introduction of renewable energy sources and energy storage systems, taking into account the development of digital competencies of operating personnel. The structure of the “Distributed Intelligent Power System” demonstration site created for testing the technologies developed within the presented framework, where digital twins and cybersecurity solutions are implemented, is described. PubDate: 2024-07-16
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Abstract: Possible areas of application of polymer-film insulation (PFI) in high-voltage distribution equipment such as busways or busducts are considered. The main advantages of this type of insulation, specific features of the existing types of insulation, and possible alternative types of PFI are discussed. The thermal and electrophysical parameters of polymer films are compared. Approaches to the selection of electric-field strengths of PFIs allowable for use in busways or busducts are described. The electric-field strength in PFI during partial discharges in the gas space between polymer films is estimated. The dependence of the dielectric strength of SF6-film insulation on the thickness of the insulation, the pressure of the SF6 gas, and the radius of curvature of the conductor is analyzed. It is pointed out that it is expedient to use polymer films made from fluoroplast-4 or its copolymers as insulation for distribution equipment of busways or busducts. PubDate: 2024-07-16
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Abstract: A neural network surrogate model of a gas turbine engine (GTE) has been developed, which approximates a more complex physico-mathematical model. The results generated by the model are demonstrated. A method for assessing the technical condition of an object is proposed, which is based on back-propagation in the artificial neural network. The main use cases are described and conclusions are made about the potential advantages of neural network surrogate models. PubDate: 2024-07-16
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Abstract: The problem of evaluating the operational efficiency of low-voltage switching devices in shop-floor power supply systems is addressed. To solve the problem, the technical condition of modern electrical devices was studied, and an algorithm and models for determining the main performance characteristics of circuit breakers, magnetic starters, and contactors of different manufacturers were developed. The dependence of real-power losses in such devices on their rated currents was established. Approximation functions of real-power losses and resistances of electrical contacts and connections depending on the main rated parameters of circuit breakers, magnetic starters, and contactors were derived. An algorithm and models for evaluating the operational efficiency of low-voltage switching devices were developed, which allow determining more accurately the losses of real power and electric power in low-voltage electrical networks. The results of the study are recommended for improving the accuracy and reliability of the calculation of power losses in in-plant electrical networks. PubDate: 2024-07-16
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Abstract: The influence of various factors on logarithmic velocity profile is considered. The dependence of the parameters of the logarithmic velocity distribution on the location of flow gauges across the channel width, the geometrical parameter b/h, and the channel grade was studied by processing experimental data for smooth and rough flumes obtained in the Laboratory of Hydraulics and Hydromechanics of the National Research Moscow State University of Civil Engineering. PubDate: 2024-07-15
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Abstract: In development of previous studies of steel 15NiCuMoNb5 (WB36) service properties, the results of which are presented in previous publications by the authors, this article presents results of analysis to assess the effect of thermal ageing on microdistribution of the steel elemental composition and structural parameters. It is shown that quite long thermal exposures do not affect alloying element local distribution within steel, including a welded joint transition zone. Precise microstructural studies performed by means of electron microscopy reveal an increase in secondary phase precipitation dynamics in the form of carbides and copper-containing particles from solid solution during thermal ageing. PubDate: 2024-07-15
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Abstract: The article presents the results of comprehensive field and theoretical computational studies aimed at clarifying the discharge capacity of the dam of the Rublevsky water supply station. They are based on the data from actual measurements of flow velocities and mathematical modeling of water flow through a spillway dam using a model developed in a two-dimensional vertical formulation. Drawing from the results of the studies performed, we bring forward proposals for calculating the discharge capacity of spillway dams. PubDate: 2024-07-15
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Abstract: This article discusses the approaches to the combustion of high hydrogen fuels in dry low NOx (DLN) combustion chambers of gas turbine units produced by two leading manufacturers of power equipment: Mitsubishi and General Electric. The designs of burner devices addressing key challenges in traditional DLN are analyzed, including flame flashback into the premixing zone, combustion process instability, and high-pressure losses on burners. These designs feature the absence of a vane swirler and the organization of separate small mixing and flame zones within the combustion chamber. The stages of research on such burner devices are discussed, and a comparative evaluation is provided. The results of full-scale tests conducted during the combustion of fuels with a high hydrogen content are presented. PubDate: 2024-07-15
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Abstract: The advantages of the FCAW-S technology when making circumferential welded joints of pipes with a diameter of up to 2520 mm are indicated. The rational shape of edges prepared for welding pipes with a wall thicknesses of up to 40 mm is proposed. It is shown that it is possible to construct assembly and welding areas (jigs) for site assembly of products at extremely low temperatures using exclusively domestic main equipment. PubDate: 2024-07-15
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Abstract: The article considers the specific features of the concreting process using shrinkage-compensating cast-in-place concrete mixtures when replacing hydraulic power equipment at the Saratov Hydroelectric Power Station in the context of changing the raw material base and the working conditions. PubDate: 2024-07-15
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Abstract: A comparative experimental study of the structure and properties of 25Kh1M1FA steel rotor metal from a PT-60-90 turbine is conducted after operation for approximately 400 thousand hours and appearance of a crack in the axial channel, and from a PT-60-130 turbine after additional thermal aging equivalent 600 thousand hours at a live steam temperature of 555°C. Despite the absence of obvious signs of recrystallization within the metal microstructure, after ageing there is a significant, up to ~1.5 times, decrease in metal hardness and other short-term strength mechanical properties. Weakening is not related to the diameter and distance between relatively large (over 1 μm) particles. A negative effect of decreasing molybdenum content in solid solution on strength is demonstrated. Stress-rupture strength for 100 thousand hours at 525°C decreases by a factor of 1.4, due to which the value of the guaranteed service life of a PT-60-130 turbine rotor after ageing at 650°C decreases from 1.7 × 105 to 1 × 105 h. Brittle failure resistance increases, i.e., the metal critical brittleness temperature decreases from 56 to 42°C. It is found that appearance of a crack in an axial channel is not necessarily accompanied by a large degree of bainitic component spheroidization (more than 3 points). A reduction in PT-60-90 turbine rotor metal hardness to a lower permissible level of 180 HB occurs after about 50 thousand hours, which indicates that the PT-60-90 turbine may be operated up to 450 thousand hours. PubDate: 2024-07-15
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Abstract: The numerical hydrodynamic experiments on SolidWorks modeling of a pile grillage made it possible to determine the loads on and the reactions of structures taking into account the time factor. The grillage design is optimized so that the distribution of pressure over the lateral surface of the piles is uniform. PubDate: 2024-07-13
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Abstract: Within the framework of the nonlinear dispersion theory of shallow water, a technique and a computer program were developed to model wave propagation in the sea coastal zone. The study took into account wave breaking in the presence of heterogeneous bottom topography and wave-permeable hydraulic structures. The article provides examples of calculations. PubDate: 2024-05-01
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Abstract: The article presents the results of in situ tests of a concrete massive buttress dam under dynamic impacts of varying intensity. The study analyzes the dynamic response of the structure to impulse excitation from a vibration generator, from underwater explosions, and from the action of minor earthquakes. The dynamic buttress dam characteristics are evaluated. The damping parameters and natural frequencies of the structure are specified. PubDate: 2024-05-01
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Abstract: This study compares samples of erosion resistant coatings made of geomat filled with crushed stone with bituminous and bitumen-polymer binders. The comparison was made several years after the production of the coatings under study. The article provides conclusions about the coating durability and the specific features of its application, as well as recommendations for using roughness coefficient. PubDate: 2024-05-01
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Abstract: In the study, compliance with the requirements of regulatory documents for the filtration regime of the Chirkey dam and its rocky base is assessed, as well as the degree of effectiveness of grout curtains and drainage barriers in terms of filtration rates in a fractured rocky base, hydraulic pressure on the dam and on the tunnel lining of the operational spillway, and pressure drops on grout curtains and drainage barriers. PubDate: 2024-05-01
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Abstract: The article discusses methodological approaches to the generation of long-term time series of water balance elements to assess and forecast river waters in the outlet section of a river catchment area. The study relies on the example of the Volga River basin. New approaches are proposed to determine difficult-to-measure water balance elements, such as evapotranspiration and changes in the basin soil moisture storage. PubDate: 2024-05-01