Thermal Engineering最新文献

{"title":"Determining the Profile Loss of Flow Kinetic Energy in Turbine Cascades with the Use of Neural Networks","authors":"V. A. Tishchenko,&nbsp;A. A. Belousova,&nbsp;P. M. Nesterov,&nbsp;A. O. Smirnov","doi":"10.1134/S0040601525700053","DOIUrl":"10.1134/S0040601525700053","url":null,"abstract":"<p>The article addresses matters concerned with the use of neural networks for predicting the gas dynamic characteristics of turbine machinery cascades. The results of elaborating the architecture of deep machine learning models for determining the profile kinetic energy loss downstream of plane nozzle vane and rotor blade (impulse type) turbine cascades are presented. A procedure for preparing the training dataset with using numerical simulation of viscous flows is described. The dataset generated is analyzed; its shortcomings, which should be removed for improving the quality of trainable neural networks are identified. Work on selecting the architecture of neural networks for rotor and nozzle vane cascades was carried out. The studies have shown that the same structure of models is efficient for both nozzle vane and rotor blade cascades. The use of prepared models yielded good agreement between the predicted results and the data available for all types of the cascades considered. It is pointed out that the neural networks yield incorrect predictions in transonic and supersonic operation conditions near the theoretical Mach number downstream of the cascade equal to unity. This stems from the lack of information on such operation conditions in the training dataset. After the models had been additionally trained under supersonic operation conditions, it became possible to “trace” the influence of the flow wave structure on the power performance characteristics downstream of the cascade. The data obtained served as a basis for stating the importance of representing curvilinear blade passages in parametric form and the necessity to prepare the training data in a wide variation range of the majority of independent parameters. The neural networks have demonstrated high-efficient performance in solving the stated problem, which made it possible to formulate a number of algorithmic concepts for applying them in solving turbine stage design problems.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":"72 4","pages":"321 - 333"},"PeriodicalIF":0.9,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143888690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Second-Order Mixed Finite Element Method for Convection-Radiation Flows in Furnaces with Burners","authors":"Jaafar Albadr,&nbsp;Mofdi El-Amrani,&nbsp;Mohammed Seaid","doi":"10.1134/S0040601525700041","DOIUrl":"10.1134/S0040601525700041","url":null,"abstract":"<p>We present a class of simplified approximations for modelling heat transfer in a two-dimensional furnace with inclusions. The governing equations are the well-established thermal incompressible Navier–Stokes equations subject to the Boussinesq approximation for modelling the change in density. Simplified P_<i>N</i>-approximations are carried out for the radiative transfer which is coupled with convection. A Taylor–Hood finite elements technique has been adopted to solve the equations using triangular meshes. The Galerkin-characteristics method is accounted for the dominant advection. Numerical results are presented under the operation of different burners and comparisons between simulations without radiation and with radiation are discussed. Results show that the temperature on the sides of the furnace is not equal. This is due to the fact that the unsteady convection-radiation heat draws the unstable heat flow towards the sides at the chosen time. The effect of higher value of Reynolds number as far as heat transfer is concerned, is that an additional mechanism of heat transfer in the azimuthal and radial directions becomes available and higher. This is commonly termed “eddy transport” and is intense, providing much better transfer of energy across the flow at a given position than in lower value of Reynolds number. Another difference worth noting is the extent of the thermal entrance region in which the transverse temperature distribution becomes fully developed. This region is relatively short in operation with 7 and 9 burners (precisely because of the intense turbulent transverse transport of energy), whereas it tends to be long under the operation of 1 and 3 burners.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":"72 4","pages":"341 - 355"},"PeriodicalIF":0.9,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143888694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heat-Conduction Problems with Time-Variable Heat-Transfer Coefficients","authors":"V. A. Kudinov,&nbsp;E. V. Kotova,&nbsp;S. V. Zaitsev,&nbsp;E. V. Stefnyuk","doi":"10.1134/S0040601524700812","DOIUrl":"10.1134/S0040601524700812","url":null,"abstract":"<p>Based on the definition of additional boundary conditions and an additional sought function (ASF), an approximate analytical solution of the heat-conduction problem for an infinite plate subject to Newton’s symmetrical boundary conditions with a time variable heat-transfer coefficient is obtained. In accordance with the integral thermal balance method, the solution is subdivided into two stages in time. The first and the second stage include the time intervals corresponding to an irregular and a regular heat-transfer mode, respectively. At the first stage, a function characterizing the displacement with time of the temperature disturbance front along the ξ coordinate is adopted as the ASF. At the second stage, a function characterizing the change with time of the temperature at the symmetry center, in which the boundary condition of no heat transfer is specified, is considered as the ASF. Owing to the use of ASFs at both stages, it becomes possible to boil down the solution of the initial differential equation with partial derivatives to integration of an ordinary differential equation with respect to the ASF. By solving this equation at the second stage, the eigenvalues are found, which are determined in the classical methods from the Sturm–Liouville boundary value problem, in which a transcendental trigonomertic equation is solved for each particular Biot number using a numerical method. Hence, in this case, another technique for determining eigenvalues is considered, which makes it possible to obtain a formula from which eigenvalues for each particular Biot number can be found. The form in which the additional boundary conditions are given is such that their satisfaction in finding the sought solution would be equivalent for the case of solving the initial differential equation at the boundary points. It is shown that the solution of the equation at the boundary points leads to its solution also inside the domain considered; in this case, direct integration of the equation along the spatial variable is excluded and is only limited to fulfilling the thermal balance integral, i.e., the averaged initial differential equation.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":"72 4","pages":"334 - 340"},"PeriodicalIF":0.9,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143888774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental Study of the Core Cooling at the Reflooding Stage of a Large Break Loss-of-Coolant Accident","authors":"A. N. Churkin,&nbsp;A. G. Karetnikov,&nbsp;M. A. Bykov,&nbsp;A. S. Bogdanov,&nbsp;Yu. A. Bezrukov","doi":"10.1134/S0040601525700065","DOIUrl":"10.1134/S0040601525700065","url":null,"abstract":"<p>The paper presents a description of the experimental facility at OKB Gidropress designed to study thermohydraulic phenomena during the core reflooding caused by a large break loss of a coolant accident in a water-moderated water-cooled (VVER) power reactor. The performed studies yielded a statistically significant amount of experimental data on the time-dependence of the temperature of the fuel-rod simulator cladding at several sections of the fuel-assembly (FA) model that is necessary for the validation of computer codes. The experiments were carried out with two fuel-assembly models with uniform and nonuniform heat release distribution along the height. Each model included 120 heated fuel-rod simulators, 13 spacer grids, six guide channel simulators, and a fuel assembly’s upper nozzle. In the experiments, five options of cooling water supply—bottom, gravity-driven bottom, top, combined, combined gravity-driven—were implemented. To confirm the reproducibility of the experiments, most of them were repeated three to five times. The fuel-assembly models, fuel-rod simulators, used instrumentation items, and experimental procedure are described. Examples are presented of the cooling dynamics of the fuel-rod simulators for different methods of cooling water supply to the reactor model, and the features of each flooding pattern are outlined. The data on the flooding time of the fuel-assembly model are generalized in the form of linear dependencies of this parameter on the relative power of the fuel-rod simulators.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":"72 4","pages":"298 - 308"},"PeriodicalIF":0.9,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143888693","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Horizontal Steam Generators: Design Improvement and Experimental-and-Computational Studies (Review)","authors":"V. N. Blinkov,&nbsp;A. V. Dedov,&nbsp;I. V. Elkin,&nbsp;V. I. Melikhov,&nbsp;O. I. Melikhov,&nbsp;S. M. Nikonov,&nbsp;A. S. Nikulin","doi":"10.1134/S004060152570003X","DOIUrl":"10.1134/S004060152570003X","url":null,"abstract":"<p>A review is presented of designs of horizontal steam generators (SG) for nuclear power plants (NPP) with water-moderated water-cooled reactors (VVERs) and of experimental-and-computational studies of thermohydraulic processes running in them. Horizontal SGs are examined from the first commercial design of the PGV-440 SG and the most widely used today PGV-1000M SG to the steam generators developed for the new generation reactor units of types VVER-1200 and VVER-TOI as well as for the high-power VVER-1500 reactor. A comparative analysis was carried out of the experimental facilities developed for the investigation of thermohydraulic processes occurring in a horizontal steam generator. Each of the examined experimental facilities has limitation related to the capabilities for the simulation of a full-scale SG caused by either geometric characteristics or thermohydraulic conditions. Nevertheless, it has been demonstrated that we have at present a sufficiently large experimental database suitable for validating computational codes simulating thermohydraulic characteristics of a horizontal steam generator. A review of the available computational codes is presented. The STEG code in which the two-phase flow is described by multifluid models is examined in more detail. The validation of the STEG code against experimental data on void fraction, pressure drop, and water velocity demonstrated high accuracy of the predictions. One of the problems to be solved in designing horizontal steam generators for new generation reactor units is the improvement of the equalization ability of the submerged and steam-receiving perforated sheets due to the enhanced nonuniformity of the steam load on the evaporation surface and of the steam flow in the steam space. The results are presented of the experimental-and-computational investigation of the equalization ability of perforated sheets, which corroborate the possibility of its improvement by application of a variable perforation ratio. The areas of further experimental investigations into thermohydraulic processes in a horizontal steam generator and ideas for improving the computational codes are formulated.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":"72 4","pages":"265 - 288"},"PeriodicalIF":0.9,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143888691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computational and Experimental Studies of Reflooding Processes in a Large-Scale Model of a VVER Fuel Assembly","authors":"M. A. Bykov,&nbsp;Yu. A. Migrov,&nbsp;M. V. Sazontova,&nbsp;A. N. Churkin","doi":"10.1134/S0040601525700016","DOIUrl":"10.1134/S0040601525700016","url":null,"abstract":"<p>The paper presents a brief review of experimental and computational studies of the reflooding processes occurring during large break LOCAs in the primary circuits with subsequent supply of the coolant in pressurized water-moderated water-cooled power reactors (VVER). The results of the PREMIUM project, carried out by OECD (CSNI), on the assessment of the prediction of reflooding parameters using the most well-known computer codes (RELAP5, CATHARE, ATHLET, APROS, MARS) are analyzed. The calculations were performed using data from one of the experimental regimes simulated at the FEBA test facility (Germany) for reflooding simulation. It is stated that the uncertainty of the estimate of the maximum temperature of fuel rods obtained by known system computer codes can attain 100°С as follows from the results of validation calculations. Based on a statistically significant set of experiments conducted on a unique reflooding test facility at OKB Gidropress with several cooling water supply options, the domestic KORSAR computer code was validated, including the gravity reflooding when water is supplied to the upper part of the reactor pressure plenum model. It has been demonstrated that the KORSAR code is not worse than the best international codes in terms of the accuracy of the predicted maximum temperature of fuel-rod simulators and flooding time for the test fuel assembly.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":"72 4","pages":"289 - 297"},"PeriodicalIF":0.9,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143888692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Field of Acoustic Standing Waves in the VVER Reactor Coolant Circuits","authors":"G. V. Arkadov,&nbsp;M. T. Slepov","doi":"10.1134/S0040601525700028","DOIUrl":"10.1134/S0040601525700028","url":null,"abstract":"<p>Many research teams and groups pay much attention to matters concerned with hydrodynamic impacts exerted on the equipment of nuclear power facilities (NPFs), which is reflected in numerous publications: monographs, articles, and reviews. However, despite the availability of theoretical works on this problem, matters concerned with applied investigations, i.e., immediately with direct measurements, still remain beyond the scope of scientific interests of Russian and foreign scientists. The need of studying them for practical applications is mainly stemming from the complexity of interpreting various revealed abnormalities, requirements for precise adjustment of various models, and essentially different spectral images of equipment not only within the framework of various designs of reactor plants (RPs), but in the power units of the same type within one NPP. These problems cannot be solved using solely theoretical or calculation methods, or using simulation software tools. The situation is also aggravated by the fact that the process of carrying out investigations is an exceptionally complex problem in terms of both selecting the data sources and interpreting the information obtained. In all likelihood, it is exactly these factors due to which an essentially weakened interest in experimental works on vibroacoustic topic in various RPs both in Russia and other countries can be explained. The article briefly presents some results of studying the fields of acoustic standing waves (ASWs) in the reactor coolant circuit (RCC) of a reactor plant equipped with a pressurized water reactor (VVER-1200) taking as an example power unit 1 at the Novovoronezh-2 NPP; in addition, the main ASW types are described.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":"72 4","pages":"309 - 320"},"PeriodicalIF":0.9,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143888773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Study of the Possibility to Uprate an NPP with a VVER-1200 Reactor through Feedwater Heating in an Economizer with Installing an Additional Turbine","authors":"R. Z. Aminov,&nbsp;M. V. Garievsky,&nbsp;A. S. Sakharov","doi":"10.1134/S0040601524700794","DOIUrl":"10.1134/S0040601524700794","url":null,"abstract":"<p>A search of efficient ways for uprating the existing NPPs deserves close attention owing to significant saving of expenditures for implementing them in comparison with construction of new NPPs. In this connection, a new method for uprating an NPP with water-cooled reactors is proposed and discussed, which involves heating of feedwater in an economizer prior to supplying it to the steam generators by using the reactor coolant from the steam generator’s outlet. This results in an increased main steam output from the steam generator without changing its thermal power capacity, and a decrease in the average coolant temperature in the reactor core without changing it at the reactor outlet helps increase the core reactivity. With excess steam supplied to an additional steam turbine unit, it becomes possible to decrease the total costs for a power unit’s modernization and enhance the NPP safety through providing backup power supply for power plant auxiliaries in case of an emergency involving station blackout. A process cycle circuit of an NPP with a VVER-1200 reactor involving feedwater heating in an economizer upstream of the steam generator is developed and substantiated. The economizer main characteristics required for feedwater heating to 245 and 265°C are determined. The effect from installing the economizer on the reactor coolant pump operation and on the reactor coolant circuit as a whole is determined. It is shown that the power output of the NPP unit with a VVER-1200 reactor and with an additional turbine increases by 37.17 and 95.88 MW, respectively, with feedwater heated to 245 and 265°С.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":"72 3","pages":"192 - 202"},"PeriodicalIF":0.9,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809187","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Design of Turbine Blade Internal Cooling: a Thermofluidic Study on the Influence of Varying Cooling Channel Numbers and Configurations","authors":"A. Otmani,&nbsp;N. Benmehidi,&nbsp;M. S. Kahaleras,&nbsp;H. Khatir,&nbsp;S.-E. Azzouz","doi":"10.1134/S0040601524700782","DOIUrl":"10.1134/S0040601524700782","url":null,"abstract":"<p>This paper explores the effect of varying the number and configuration of internal cooling channels on the thermal performance of gas turbine blades. The findings demonstrate the significance of this parameter for improving blade cooling efficiency. Actually, such a study is lacking in the currently available literature. Therefore, six internal cooling configurations were designed using Autodesk Inventor employing the real turbojet airfoil RS1S. The high-pressure gas turbine rotor blades were designed with an 11° twist angle in order to predict the actual behavior of the blade cooling under operating conditions. A series of numerical tests were carried out by coupling the CAD software with COMSOL Multiphysics. A conjugate heat transfer and computational fluid dynamics model were performed. Convective heat flux (CHF), temperature, Nusselt number, air velocity, Reynolds number, and friction force were evaluated for each studied case. The findings showed that adding a second cooling channel to the trailing edge improved the convective heat flux by 63%. On the other hand, creating a new cooling channel increased the blade’s thermal inertia, leading to a cooling limitation. It was also observed that hot spots on the blade surface can develop as a result of air thermal saturation due to extended residence time in the blade channels. In fact, the blade average temperature decreased by 8% using five disconnected channels rather than five serpentine channels. The blade temperature and CHF were reduced by 16 and 22%, respectively, as a result of adding a third channel in the blade mid-zone. Overall, this paper highlighted the potential for improving blade internal cooling through the careful optimization of the number and configuration of internal channels.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":"72 3","pages":"181 - 191"},"PeriodicalIF":0.9,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Acoustic-Aerodynamic Processes in the Macroporous Modules Used in the Silencers of Noise from Steam Dumps at Thermal Power Plants","authors":"Yu. G. Sukhorukov,&nbsp;E. O. Tass,&nbsp;L. R. Yablonik","doi":"10.1134/S004060152470085X","DOIUrl":"10.1134/S004060152470085X","url":null,"abstract":"<p>Steam dumps from thermal power plants (TPPs) into the atmosphere are among the most powerful man-induced noise sources. The protection, by means of silencers, against the noise produced by high-pressure steam dumps includes, in the general case, implementation of low-noise throttling and installation of sound-absorbing components. The comparative efficiency of the silencer throttling and sound-absorbing components depends on the location and intensity of physical noise sources, which are determined by the steam dumping pipeline’s operating and geometrical parameters. The use of macroporous modules in steam dump silencers is of significant interest owing to their relative simplicity and good performance. Such modules can be used as continuously operating throttling devices; in addition, they have certain sound-absorption properties. The aerodynamic and acoustic properties of macroporous modules used as part of the silencers of noise produced by the TPP steam dumps are analyzed. The main sources causing noise from the TPP steam dumps are considered, and analytical relations for comparing their intensities are formulated. Proceeding from the performed assessments, methods for protection from the noise produced by steam dumps are suggested, which involve the use of silencers equipped with macroporous modules. In discussing matters concerned with the aerodynamics relating to continuous throttling of gaseous medium in macroporous channels of various shapes, it is shown that correct profiling of channels in coordination with the characteristic pore sizes is important for practical applications. Assessments of sound absorption in a macroporous medium are carried out. Recommendations on shaping the macroporous modules of silencers are given, and methods for calculating their efficiency in solving problems of protection from noise caused by dumping high-pressure steam into the atmosphere are presented.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":"72 3","pages":"221 - 228"},"PeriodicalIF":0.9,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}