AbstractThe results of experimental studies into the hydrodynamics of the coolant at the outlet section of the cassette fuel assembly (FA) of the RITM-type reactor of a low-power ground-based nuclear power plant are presented. The purpose of the work is to analyze the distribution of the axial velocity and flow rate of the coolant at the exit from the fuel bundle, in the modernized head of the fuel assembly, near the coolant extraction pipe and the openings of the upper base plate as well as to determine those areas of the fuel bundle from which the coolant flow is most likely to enter the pipe selection to the resistance thermometer. To achieve this goal, experiments were carried out on a research stand with an air working medium on a model of the outlet section of a fuel cassette, which includes an outlet fragment of a fuel bundle with spacer grids, models of an upgraded fuel cassette head, an upper support plate, and a coolant extraction pipe. When studying the flow of the coolant flow in the outlet part of the fuel cassette, the pneumometric method and the method of injection of a contrasting impurity were used. An area covering the entire cross section of the model was chosen as the area under study. The picture of the coolant flow is represented by cartograms of the distribution of its axial velocity and flow rate as well as cartograms of the distribution of the contrasting impurity in the cross section of the experimental model. The results of the experiments can serve as a basis for making engineering decisions when designing new cores of RITM type reactors. The obtained database of experimental data can be used for validation of modern CFD programs and one-dimensional thermal-hydraulic codes used to justify the thermal reliability of cores.

AbstractIntegrated gasification combined-cycle (IGCC) units, which use solid fuels (coal, petroleum coke, etc.) for combined-cycle power generation, have been under development for approximately half a century. At present, the countries of the Asian region show the greatest interest in this type of power plants. Two large IGCC power units entered into commercial operation at Nakoso and Hirono thermal power plants (TPPs) in Japan; in addition, the Osaki CoolGen project is advancing greatly. The People’s Republic of China and the Republic of Korea are also improving their IGCC projects. Development of more efficient technologies for generator gas cleaning and application of the next generation of gas-turbine units (GTUs) at new IGCC units have cut down harmful emissions and increased the efficiency up to 48%. The 21st century has brought increased interest in IGCC units due to the ability of their equipment to capture CO2. Besides the above-mentioned advantages, IGCC units also have disadvantages, the biggest of which is their high cost. That is why, despite many IGCC projects to be deployed in the 2000s, most of these projects were subsequently canceled, and the plants built in the 1990s are being gradually decommissioned. The promising direction for future application of IGCC units is the production of hydrogen for fuel cells with simultaneous CO2 capture. The polygeneration technology already used at some facilities, which enable the generation and delivery to the consumer of not only electricity but also gasification by-products, will also render support to the solution of the economic problems of IGCC units.

AbstractIn Russia, boiler units at many coal-fired thermal power plants (TPPs) are being converted to operation on off-design fuel due to the introduction of more and more strict environmental regulations, changes in the economic situation, and also due to a decrease in design coal reserves. During the service life of the Artemovsk combined heat and power plant (TETs), the design coal deposit was exhausted. Therefore, a replacement solid fuel for BKZ-220-100F boiler units had to be found. Since conversion to off-design coals may induce negative factors, such as a decrease in the reliability of the heating surfaces and maintenance of the required superheated steam conditions, a variant analysis, including that on the basis of numerical simulation, of the processes occurring during coal burning in a combustion chamber (furnace) enjoys current interests. The objective of this study is to analyze the effect of furnace processes on operating reliability, efficiency, and environmental safety of a boiler unit when burning off-design coals. Numerical analysis was carried out using the ANSYS Fluent software package, and mathematical modeling of furnace processes was based on the Euler-Lagrange approach. The results of simulation are compared with check and zone-by-zone calculations of the furnace chamber. In the horizontal section, at the level of the burners, high-temperature zones are singled out in the near-wall region at the corners of the furnace chamber, which are formed by the waterwalls on the left side and front walls as well as the waterwalls on the right side and rear walls.1 The numerical simulation has revealed that the tangential arrangement of the burners induces a vertical vortex in the furnace chamber; however, the direction angles of the burner jets should be corrected. Combustion of El’ginsk coal considerably changes the furnace temperature conditions, thereby increasing the risk of heating surfaces slagging.

Abstract—The need of traversing the flow gas-dynamic parameters, when trying out new last stages of a steam turbine’s low-pressure cylinders (LPC), is shown. The specific features of pressure measurements according to the pneumometric method by means of probes in the last stages operating in a wet steam (two-phase) medium, with the probe’s receiving holes and pneumatic lines becoming blocked with condensate, are shown. The changeover for using small-size probe heads featuring better measurement accuracy in comparison with large-size heads is substantiated. A universal algorithm for purging the pneumatic lines periodically with atmospheric air for various probes with receiving holes of certain diameters is proposed. The universal algorithm is obtained by supplementing the system with a subroutine that automatically monitors the time delay after closing the purging valves prior to carrying out measurements at the traversing point. At that, excluded are incomplete removal of residual purging air with condensate from the pneumatic lines and excessive time delay before measurements. The algorithm is implemented in improving the previously developed traversing system. Better accuracy of measuring the pressures and flow meridian angles is achieved owing to the use of high-precision transducers in each of the probe measurement channels with the absolute pressure range 0–30 kPa with the accuracy equal to 0.05% of the upper measurement limit. The time taken to process the traversing results is decreased by adding three measurement channels to the system, which operate synchronously with the probe and characterize the turbine operation mode. A modern system for traversing the flow in the gap between blade rings of the last stages has been developed. The results of this development are used in studying the advanced steam turbine LPC compartment on the full-scale test bench at JSC Power Machines.

AbstractMain results are presented of the trial tests of a closed loop with natural circulation (NC) of a light-water coolant under supercritical pressure (SCP), which is a part of the thermal engineering test facility at the site of the National Research Centre (NRC) Kurchatov Institute. Experimental data on a change in the distilled water heat transfer were obtained for an upward flow in a ∅6.0 × 1.5 mm stainless-steel tube with indirect electric heating at a specific heat load as high as 0.5 MW/m2 and a mass velocity of up to 300 kg/(m2 s) and also for a downward flow in a vertical tube bundle consisting of seven finned stainless-steel tubes with a size of ∅12.0 × 2.5 mm each in an upward natural convection air flow in the shell side. In addition, experimental data were obtained on the dynamics of heating of main equipment items in the loop circuit with natural convection of distilled water at supercritical pressure. These data were used to validate a code for calculation of the heater, cooler, and overall loop. The paper analyzes the features of the heating dynamics of the main equipment items in the closed loop with natural circulation of supercritical pressure water (SCW) as well as the specific of SCW heat transfer in four sections of the heater and cooler. In the experiments, the following main stages of SCW heating were experimentally revealed: heating of the pseudo-liquid, pseudo-phase change (pseudo-boiling), and heating of the pseudo-steam; in the cooler: cooling of the pseudo-steam, pseudo-phase change (pseudo-condensation), and cooling of the pseudo-liquid. The work was performed for substantiation of engineering and process solutions for a nonreactor loop of a supercritical pressure light water power reactor (VVER-SCP) under an order of AO Concern Rosenergoatom.

AbstractSchemes of high-temperature turbines operating on hydrogen-oxygen and methane-oxygen fuels, the design of an experimental prototype of such a turbine with a capacity of 100 kW, and the results of its testing are described. A combustion chamber for burning methane-oxygen fuel in steam was developed, manufactured, and tested in a laboratory test setup. A unit for additional gas superheating of the working fluid was designed, manufactured, and tested on the basis of the T-25-90-4PR-1 turbine at the cogeneration power plant TETs-16 of the branch of JSC Mosenergo. The experimental studies have demonstrated stable combustion of the methane-oxygen mixture in a steam environment and confirmed the serviceability of the technology for additional gas-fired superheating of the working fluid in a real thermal power plant. Temperature distributions in the metal of the flame tube and casing during start-up and under the design conditions were obtained. The technical characteristics of the high-temperature gas-steam-turbine unit and the classical K-300-23.5-3 version are compared. Unavailability of regulations required for the implementation of an unconventional project at a real thermal power plant is noted. The required technical basis was obtained, and the procedure for elaboration of a demonstration model of a high-temperature gas-steam turbine with a capacity of 25 MW at a temperature of 1000°C and a prototype of a power unit with a capacity of 300–500 MW for a pressure of 30 MPa at a temperature of 1250/1450°C was proposed.

Abstract—Possible outcomes from the decisions adopted at the COP26, the latest Conference of the Parties to the UN Framework Convention on Climate Change (UNFCCC), for the world energy and upcoming climate changes are studied. The article suggests a group of scenarios for man-induced impacts on the global climatic system, which includes implementation of the COP26 decisions in the field of world economy decarbonization, reduction of methane emissions, and reforestation as well as alternative world energy development scenarios based on a low globe population growth level from the viewpoint of preventing dangerous global climate changes. By using the global carbon cycle and climate models developed at the National Research University Moscow Power Engineering Institute (NRU MPEI), changes in the chemical composition and thermal radiation balance of Earth’s atmosphere, as well as the global average air temperature, are evaluated for each scenario. It is shown that global warming by 1.5°С can only be kept if the entire range of measures suggested at COP26 on reducing the man-induced impact on Earth’s climatic system is implemented in the full scope while keeping the energy consumption and world population growth rates at the contemporary levels; however, there are serious doubts as to whether the proposed world economy decarbonization program can really be implemented. At the same time, the natural demographic processes are able to curb the growth of carbon dioxide concentration in the atmosphere and decrease it even before the end of this century. In that case, the increase in the global average temperature by 1.8°С in comparison with that in the preindustrial period (1850–1900) may be quite safe and will not require large-scale reformation of the world energy sector.

Abstract—The HG-2100/25.4-YM16 boiler, manufactured by Harbin Boiler Co., operates as part of the 660‑MW power unit at the Troitsk district power plant (DPP). An analysis of the boiler design showed that many technical solutions adopted in the boiler differed from those commonly used by Russian manufactures. The aim of the study is to simulate and optimize the boiler startup technology without using the circulation pump (CP) but with ensuring reliable operation of the boiler components. For achieving this aim, the following main tasks must be solved: to substantiate reliable operation criteria of boiler components during the startup, to develop adapted static and adapted dynamic boiler analysis models (SM and DM, respectively), and to study the possibility of boiler starting without using the CP. The main criteria for reliable operation of the boiler’s lower and upper radiant parts (LRP and URP, respectively) are the absence of a scale formation process (the design temperature of the metal outer surface must be below its permissible value) and stable motion of medium. However, the results of predicting the steam superheating surface metal temperature in a dynamic mode are not sufficiently accurate. Therefore, the reliability criterion adopted for these surfaces was the steam flowrate downstream of the separator, the values of which in the boiler starting modes with and without the pump should be close to each other. The reliable operation criterion of the low-pressure steam superheater outlet stage (LPSS2) is the gas temperature at the furnace outlet, which shall not be higher in starting without the CP. The numerical analyses were carried out using the Boiler Designer software package. The boiler adapted static model was developed taking into account the authors' previous works and with comparing them with the results of manufacturer’s calculations. After that, the boiler adapted dynamic model was developed on the basis of its static model. To this end, the trends of real startup modes with participation of the circulation pump provided by Troitsk DPP specialists were used. Based on these data, taken together with the experience gained from the authors' previous numerical analyses and expert estimates, the dynamic model tuning was performed. Three boiler starting modes from its cold state were studied in detail: one with the pump (at the feed water temperature tf.w = 104°С) and two modes without the pump (at tf.w = 104 and 150°С). In all cases, the following startup stages were considered: hot flushing, turbine kicking, kicking mode end, and reaching the boiler once-through operation mode. The last stage corresponded to 30% of the boiler maximum continuous rating (BMCR). An analysis of the obtained results has shown that the adopted reliability criteria are fulfilled for all boiler operation modes and stages.

AbstractA scheme of a combined-cycle unit with thermochemical recuperation of flue gas heat using methane steam reforming is considered. The essence of thermochemical recuperation is the recovery of flue gas heat for the endothermic methane reforming yielding a new synthetic fuel. The results are presented of a thermodynamic analysis of the combined-cycle unit thermal cycle with a gas turbine inlet temperature of 1500 and 1600°C at a pressure in the combustion chamber from 2 to 4 MPa. The thermodynamic analysis of the thermal cycle of a combined cycle unit was performed using the Aspen HYSYS software package, and the thermodynamic analysis of methane steam reforming was performed using the Gibbs free energy minimization method. The efficiency of thermochemical recuperation of flue gas heat has been demonstrated to depend on the process conditions, such as pressure, temperature, and composition of the initial reaction mixture. Increasing the temperature and the steam to methane ratio increases the reaction enthalpy and the efficiency of methane reforming, while an increase in the pressure decreases these parameters. It has been found that the thermochemical recuperation of heat can increase the effectiveness of a conventional combined-cycle unit by 3–5%. For example, the efficiency of a combined-cycle unit is 59% without thermochemical recuperation or 64% with thermochemical recuperation at a turbine inlet temperature of 1600°С and a compression ratio of 30. The thermal and material balances of a combined-cycle unit with thermochemical heat recuperation are presented in the form of energy and material flows, according to which 45% of the exhaust gas heat is recuperated in the fuel cycle of the gas turbine unit and approximately 45% of the exhaust gas heat is consumed in the steam turbine cycle.

AbstractThe processes of film condensation of stagnant and moving vapor on a single tube and various tube bundles were examined in many studies. Nevertheless, the local characteristics of heat transfer and the details of the interaction of the flowing down condensate with a moving vapor flow, which can have a significant effect on the characteristics of the condensation process in tube bundles, are not well understood. The paper presents the results of simulation of the condensation of practically stagnant and of moving saturated vapor on a horizontal cylinder. The mathematical model of a two-phase flow is based on the Volume of Fluid (VOF) method, which is implemented in the in-house CFD-code ANES. The main advantage of the proposed simulation method is that it can capture the interface without any assumptions. The modified Lee model was used to model interfacial mass transfer. An algorithm is proposed for the automatic selection of a constant in this model on the basis of the specified properties of the coolant and parameters of the computational grid. The model was validated against the classical Nusselt solutions for a vertical plate and a horizontal cylinder, known calculating correlations, and predictions obtained using a simplified condensation model proposed by the authors of this paper in previous studies. Information is presented on the drip-off diameters of droplets, the dynamics of heating of subcooled condensate droplets after their drip-off from the tube surface, and the effect of external tube spraying on the condensation rate. The obtained data are compared with the available experimental results.

AbstractShell-and-tube type heat exchangers (STHE) are the most important part of non-combustion heat transfer equipment in industrial processes. The literature provides extensive information on various methods of optimizing the design of STHE, however, as a rule, it is carried out only with the aim of minimizing costs as an objective function. In this paper, it is proposed to use multi-purpose optimization of STHE using new thermodynamic and environmental expressions as objective functions. Its implementation is possible with the use of genetic algorithms of the second generation. The paper presents a procedure and a mathematical model for multi-purpose optimization, in which five objective functions are proposed to be used: the coefficient of thermal resistance, thermal efficiency, environmental function, total cost, including operating costs, and the total amount of dissipated entransy. The concept of entransy is proposed for the first time to create a new ecological function used as a criterion for optimizing STHE. The novelty of the proposed work lies in the fact that it optimizes simultaneously taking into account mechanical and vibration limitations, the design of the heat exchanger, as well as taking into account the parameters of thermohydraulic processes occurring in it. The approbation of the methodology was carried out on the basis of a specific case study, which had previously been repeatedly used by various authors to verify the results obtained. The multi-purpose optimization of the STHE made it possible to develop design options with minimal costs at a given thermal load and with geometric options that are adaptable to the space available for installation and the availability of auxiliary systems.

AbstractThe prospects for the use of new, two-dimensional nanomaterials (2D materials) for the intensification of heat and mass transfer processes in power equipment are considered. The main types of 2D materials are presented, and their physical and technological properties and unique characteristics are described. Separate technological methods for the manufacture of 2D materials and films, composites, and nanofluids for various energy applications have been studied. Special attention is paid to materials based on single-layer and multilayer graphene, characteristics of materials based on graphene components, and their physicochemical and other parameters. The effects that are observed when using nanofluids as heat carriers and when applying coatings based on 2D materials on heat-transfer surfaces during various heat-transfer processes are described: single-phase convection, evaporation, boiling, condensation. It is shown that, in all cases, the heat-transfer efficiency increases significantly. Specific examples of the use of 2D materials in heat pipes and thermosiphons are given, and ways to improve the characteristics of these devices are described. Some mathematical and physical models of functioning of two-dimensional materials in power engineering are considered. Particular attention is paid to the peculiarities of the mechanisms of heat transfer, evaporation, boiling, and condensation in energy systems. However, it is indicated that there are certain difficulties in choosing 2D materials for use in the energy sector. It is concluded that, due to additional research and the active use of 2D materials, unprecedented opportunities are opening up for the development of promising energy, construction, electronic, and other technologies as well as the creation of next-generation materials with unique mechanical, optical, electromagnetic and thermal properties.

AbstractThe development of domestic gas turbine units designed for driving electric generators or mechanical equipment at gas-pumping stations has become a crucial technological area for the power industry. At present AO Power Machines is developing the GTE-65.1 gas turbine unit (GTU), whose prototype is the GTE-65.0 GTU designed in the early 2000s. The boundary conditions adopted in designing the flow path in the modified GTE-65.1 were the shapes of the meridional outline and of the blade rows in the GTE-65.0 turbine and the main parameters under the rated operating conditions. The possibility of creating a stage two unshrouded blade for the modified GTE-65.1 turbine is examined. This solution will reduce the cooling air mass flow, decrease the cooling losses and aerodynamic losses in the tip area, and eliminate problems of bringing the strength of the cooled shroud and of the blade proper to the required level by reducing stresses in the blade body and contour stresses in the rotor disk. The operating (service) costs in this case are the comparative costs for the restoration (reconditioning) of the blade with or without a cooled shroud to be incurred after the first interval of the operating cycle corresponding to approximately 25 000–33 000 equivalent gas hours. The results of computational studies performed by the 3D NS and Fluent software packages have demonstrated that an efficient rotor blade for stage two of the GTE-65.1 GTU can be designed without any shroud.

Abstract—Efficient operation of turbine condensers is an important prerequisite for economically efficient and reliable operation of the turbine units at thermal- and nuclear power plants. Noncondensable gases entering the condenser shell space significantly affect the heat transfer intensity and, hence, the pressure at the end of the steam expansion process in the turbine. Therefore, it is important to take measures for constantly removing these gases with the minimal energy expenditures. The article considers the operation principles and operational and design characteristics of air evacuation devices used in the condensers of thermal- and nuclear power plant turbine condensers, such as water jet and steam jet ejectors, and liquid-packed ring pumps. Comparison of these devices in terms of their energy performance criteria is carried out. Conditions for ensuring adequate energy performance of water jet ejectors are shown. Based on the results obtained from the tests of water jet ejectors and liquid-packed ring pumps, it is shown that liquid-packed ring pumps do not have any essential advantages in using them as devices for evacuating noncondensable gases from steam turbine condensers. The characteristics of steam jet ejectors used at Russian thermal and nuclear power plants are given. The notion of a steam jet ejector energy efficiency is introduced. The reserves for improving the energy performance of steam jet ejectors are shown. It can be seen from the numerical analysis results that the use of steam jet ejectors is more energy efficient for the power units of nuclear power plants constructed on the basis of the AES-2006 and VVER-TOI conceptual designs than the use of liquid-packed ring pumps. In addition, liquid-packed ring pumps are essentially more costly and complex in operation. In view of a long-standing positive experience of using water jet and steam jet ejectors at thermal and nuclear power plants and their good performance, it is recommended to consider them as air evacuation devices for advanced nuclear power plant turbine units.

AbstractViolations in water- and steam-quality standards cause emergencies at thermal power plants. In such conditions, chemical monitoring provides reliable and quick information about the normalized parameters of water and steam quality by direct measurement or indirect determination of the quality indicators of the analyzed medium. The expansion of functionality and effective detection of fast-flowing disturbances in cycle-chemistry monitoring systems is possible by predicting and analyzing the behavior of impurities along the path of the power unit. However, a large volume of chemical control performed with the help of laboratory chemical control analyzers reduces the reliability of water- and steam-quality monitoring systems. In the early stages, it is advisable to carry out the occurrence of violations of the quality of water and steam at the expense of automatic devices, including conductometers and pH meters, since such devices are the most reliable in industrial operation. Currently, algorithms for calculating pH and ammonia concentration based on continuous measurements of electrical conductivity continue to be improved. Within the framework of the work, the possibility of using an indirect algorithm based on the measurement of specific electrical conductivity in conditions of deterioration of feed water quality is investigated. The pH and concentration of ammonia were determined on the basis of measurements of specific electrical conductivity with dosing of hydrocarbonates in laboratory conditions. An experiment was performed, as a result of which it was revealed that, in case of water-quality deterioration, the error in calculating pH and ammonia increases.

AbstractThe development of computer codes for modeling accidents in a reactor unit requires validation of the models built into these codes. In this work, the EUCLID/V2 integrated code developed at IBRAE RAS was validated as applied to the simulation of severe accidents with a failure of the core of liquid-metal cooled fast breeder reactors (LMFBR), against experiments on melting of the cladding of fuel-rod simulators carried out at the Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences (IT SB RAS), and SCARABEE BE + 3 experiments performed at the Commissariat à l’Energie Atomique (CEA) in France. The investigations performed at IT SB RAS included measurements of the cladding surface temperatures without liquid-metal cooling of the fuel-rod simulator, which is typical for accidents involving an instantaneous blockage of the flow section in the fuel assembly (FA) or with loss-of-coolant for type BN-1200M reactor units (RUs). To create such conditions, experiments with fuel rods were carried out in an argon atmosphere at room temperature (25°C) and a pressure of approximately 105 Pa, and the surface temperature of the fuel-rod simulator was recorded with a pyrometer. In France, the SCARABEE BE + 3 series experiments were carried out in the SCARABEE reactor to study the consequences of a hypothetical accident with a complete instantaneous blockage of the flow cross-section in a sodium-cooled fast reactor. To determine the effect of uncertainty in the initial data, diversified calculations were made. The validation was done by comparing the predictions with the experimental values of temperatures in the range between 500 to 1800 K (experiments of IT SB RAS). The maximum calculation error did not exceed 200 K. For the experiments in the SCARABEE reactor, it was not greater than 88 K for the fuel-rod claddings and 100 K the coolant. The obtained data will be used to estimate uncertainty in the predictions by the models of severe accidents with thermal destruction of fuel rods in fast reactors.

AbstractThe effect of the operating conditions on the quality of saturated steam in stationary natural circulation boilers with a superheated steam pressure at the boiler outlet of 3.9 MPa or higher (up to 15.5 MPa) is examined. At present, the need is still urgent in the domestic power industry for thermochemical testing of boilers of various pressures to standardize the quality of boiler water and steam in accordance with the requirements of the applicable regulations for water chemistries. The demand for such testing results from the need to find the cause of salt deposition in the flow path of steam turbines and develop measures to prevent the formation of deposits on turbine blading. The results of these tests have confirmed the correlation among the boiler water salt content, entrainment factor, water level in the boiler drum, and steam quality. In high-pressure drum boilers, the main impurities are iron and copper oxides, i.e., the products of corrosion of power equipment provided that the demineralized water has a high quality with a maximum specific conductivity of 0.5 µS/cm and nо cooling water inleakage occurs in the condenser. Results of the effect of a correcting chemical on the distribution coefficient of iron and copper are presented. The use of ammonia as a correcting chemical decreases the distribution coefficient for iron and copper and, hence, reduces the contamination of steam with corrosion products. The water chemistry has been demonstrated to affect the concentration of corrosion products of iron and copper in the boiler water, i.e., the blowdown efficiency, which is related with changes in the form of these compounds in water. It is pointed out that the contamination of steam with corrosion products is related with droplet entrainment since the saturated steam pressure hardly has any effect on the distribution coefficients for iron and copper. How one and the same impurity enters the steam depends on the water chemistry controlling the form of existence of this compound.

Abstract—The salt hideout phenomenon of boiler water attracted the close attention of specialists as long ago as the 1940s–1950s. By the end of the 1980s, the majority of researches had arrived at the conclusion that the governing role in the hideout phenomenon is played by the deposits of structural material corrosion products (crud) on the steam-generating surfaces of the equipment of nuclear and thermal power plants. The steam-generation process takes place under confined conditions, which causes degraded mass transfer between the flow core and the heat-transfer surface. This results in that water impurities concentrate in the pores of deposits and even precipitate in a solid phase form. As the steam boiler/steam generator power output increases, the concentrations of certain impurities and chemical agents in boiler water decrease; this effect is called hideout, and as the load decreases, their concentrations increase (hideout return). In the last decades, a few physical and mathematical models have been developed in which the hideout phenomenon is considered from the viewpoint of boiler water impurities becoming concentrated not in the layer of permeable deposits but in the viscous sublayer of liquid at the steam-generating surface. Thus, the thermodynamic model rests on the postulates of nonequilibrium thermodynamics and is descriptive in nature. The mass-transfer model based on the laws of mass and energy conservation in the viscous sublayer incorporates an analytical expression for the impurity concentration ratio. However, this model also in fact contains only a qualitative description of the hideout process without performing its detailed comparison with experimental data. The article presents an analysis of these models and their comparison with reliable data obtained by domestic and foreign researchers, and it is shown that the key statements laid down at the essence of models based on impurity concentration in the liquid viscous sublayer are erroneous in nature. Adequate fundamental principles of mass transfer under hideout conditions are of significant theoretical and practical importance for working out operation regulations and securing reliable operation of installations with boiling coolant at nuclear and thermal power plants.

AbstractThe study of steam-condensation processes inside pipes of different orientation in space is an urgent task for many industrial applications, including the creation of heat-recovery plants based on the organic Rankine cycle. This paper presents the results of the validation of a mathematical model of a two-phase flow, which is based on the Volume of Fluid (VOF) on experimental data on the condensation of the downward flow of freon R-113 in a vertical round pipe. The data obtained by numerical simulation, both in terms of integral and local characteristics, are compared with experimental data for regimes with mass flux from 26 to 294 kg/(m2 s), saturation pressures from 105 to 3 × 105 Pa, and heat flux up to 80 kW/m2 for pipes with diameters of 9.0, 14.0, and 20.8 mm. The validation results showed the efficiency of the algorithm previously proposed by the authors for determining the relaxation coefficient in the Lee model for calculating condensation inside pipes. The best agreement between the calculations and the experimental data was found when using versions of Menter’s SST turbulence model. Several simplified one-dimensional models of steam condensation inside pipes have been tested. Recommendations on the choice of the computational grid for the studied class of problems are presented. To describe the processes of halon condensation by the VOF method, the characteristic thickness of the liquid film should account for at least ten control volumes (computation mesh cells), and the longitudinal size of the cells should not exceed half the capillary constant. It is shown that it is possible to calculate the heat-transfer characteristics using a coarser grid (with a longitudinal step of up to two capillary constants); however, in this case, waves do not appear on the film surface, which significantly affects the hydraulic characteristics of the flow.

AbstractDuring operation, all components of a gas-turbine unit (GTU), including the blading of the axial compressor, are affected by the flow in the GTU flowpath, which results in the development of defects and deterioration of the main performance characteristics (efficiency, effective power, etc.). One of the most serious defects is erosive wear since it can cause destruction of one blade or all the blades in the compressor. This can lead to preliminary removal of a GTU from operation. Therefore, the erosion resistance of compressor blades is one of the main parameters controlling the service life of a gas-turbine unit. That is why studies of the erosive wear of axial compressors during operation of GTUs are urgent. This paper provides a review of the available publications on the erosive wear of blades and vanes in an axial compressor of gas-turbine units. The major erosion mechanisms classified by the type of particulates acting on blade material are examined. The geometric parameters of the compressor blading are found whose change due to erosive wear can disturb the flow aerodynamics and deteriorate the performance of individual elements and the overall GTU. The main three lines of erosive wear studies may be listed as follows: prediction of erosive wear, assessment and prediction of erosion consequences, and development of protective measures to control erosion during operation of a gas-turbine unit. The most frequently examined and promising subjects of erosion studies are outlined as applicable to gas turbine and compressor machine building. The state-of-the-art of studies in this field is analyzed.