Stationary Mode Of Operation Research Articles

THERMAL CONTROL OF THERMOELECTRIC COOLING DEVICES OF TRANSMISSION AND RECEIVING ELEMENTS OF ON-BOARDINFORMATION SYSTEMS

The work is a continuation of studies of the dynamic characteristics of thermoelectric coolers aimed at analyzing the influence of temperature differences, current operating modes, design parameters of the device and physical parameters of the material of thermoelements for a timeconstant. The article analyzes the effect of the heat sink capacity of the radiator on the dynamic characteristics, energy and reliability indicators of a single-stage thermoelectric cooler.A dynamic model of a thermoelectric cooler has been developed taking into account the weight and size parameters of the radiator, which relate the main energy indicators of the cooler with the heat removal capacity of the radiator, operating currents, the value of the heat load and the relative temperature difference. The analysis of the dynamic model shows that with an increase in the heat-removing capacity of the radiator at a given thermal load and various current modes, the main parameters of the cooler change. The required number of thermoelements, power consumption, time to reach a stationary mode, and relative failure rate are reduced.With an increase in the relative operating current, the time to reach the stationary mode of operation decreases for different values of the heat sink capacity of the radiator. It is shown that the minimum time to reach the stationary operating mode is provided in the maximum refrigerating capacity mode. The studies were carried out at different values of the heat sink capacity of the radiator in the operating range of temperature drops and the geometry of thermoelements.The possibility of minimizing the heat-dissipating surface of the radiator at various current operating modes and the relationship with the main parameters, reliability indicators and the time to reach the stationary operating mode areshown. Comparative analysis of weight and size characteristics, main parameters, reliability indicators and dynamics of functioning with rational design makes it possible to choose compromise solutions, taking into account the weight of each of the limitingfactors.

Transient process modeling in micrologistic transport systems

Micrologistic transport systems are ports, transport hubs, railway terminals (railway stations and marshalling yards), and other micro-level transport objects. Such systems are dynamic ones, whose parameters are time-dependent. Consequently, transient processes appear. These processes last for some time and then subside. Then the system goes into a stationary mode of operation. To solve most engineering problems, it is sufficient to find the stationary characteristics of the system. However, some problems require knowledge of the properties of transients. In this paper, we use the previously presented technology for modeling the operation of micrologistic transport systems to study transients in various transport objects. We consider two types of micrologistic transport systems, such as passenger and cargo, and design their models in the form of two-phase and three-phase queuing systems with BMAP flows. For these queuing systems, we compile Kolmogorov systems of ordinary differential equations. Their analytical study is difficult; therefore, to solve such systems, we use numerical methods. Overall, we find the transition probabilities of system states. We compare the obtained probabilities with stationary characteristics, which allows us to draw conclusions about the properties of transients in the considered systems.

К определению количественных параметров гидравлической модели систем комбинированного орошения на основе алгоритмизации компьютерных вычислений

Purpose: development of a computer algorithm for a quantitative assessment of the hydraulic parameters of an irrigation and drainage system with the possibility of integrating different irrigation methods. Materials and methods. The design of structures for combined irrigation is based on hydraulic calculation. A feature of such systems is the ability to change irrigation methods, which is associated with a significant change in hydraulic parameters and the complication of hydraulic design of structures. Automation of hydraulic calculations based on a universal computer algorithm is the most acceptable way to solve the problem and the basis for designing combined irrigation systems. Results. A feature of the proposed algorithm for determining the quantitative parameters of the combined irrigation system is the use of a step-by-step approach followed by the formation of a generalized hydraulic screenshot of the entire structure. A screenshot of hydraulic parameters here means a quantitative assessment of hydraulic indicators for all nodal points of a structure, implemented by a calculation method for given, stationary modes of system operation. A set of this kind of static screenshots allows you to evaluate the process in dynamics, as well as to carry out comparative assessments of hydraulic parameters under different operating modes of the combined irrigation system. The algorithm offers an original way to identify objects based on the use of a linear coordinate system. The method makes it possible to organize an enumeration of the structural elements of the system and a step-by-step calculation of hydraulic parameters from the inlet section of the design segment to any given nodal point. Conclusions. The calculation results according to the proposed algorithm make it possible to form a specially organized data array, which is a set of symbolic-numeric values that determine the pressure level and water flow rate and identify them with the nodal point of the system.

Математична модель теплонасосної системи охолодження матеріалу після сушіння і термообробки

The article considers the issue of increasing the efficiency of coolers of the material heated during drying by using a heat pump unit to produce artificial cold. The scheme of use of a thermal pump in a complex with the drying installation and the portable cooler of material is offered. A mathematical description of the stationary modes of operation of the drying unit, material cooler and heat pump elements on the basis of a steam compressor refrigeration unit is formulated. At creation of physical and mathematical models of heat and mass transfer in the course of drying and cooling of material (grain) the following conditions are accepted simplifying the mathematical description, but without changing real process: moisture from the material is removed according to Dalton's evaporation law, while the moisture in the material evaporates and is removed simultaneously; moisture content and temperature in the volume of the material are evenly distributed, heat and mass transfer occurs only between the surface of the material and the drying agent; the effects of radiation and contact heat transfer are taken into account by heat transfer coefficients; stationary fields of temperature and moisture content are assumed to be one-dimensional, which vary according to the coordinate calculated in the direction of movement of the material; when cooling the moisture removal material is not taken into account for low residual moisture; the size of the surface of the material in the process of drying and cooling does not change; the heat exchange equipment of the heat pump is an object with concentrated parameters. Using the obtained mathematical dependences, graphical dependences of changes in grain and air temperature are constructed, which allow to evaluate the expediency of using a heat pump. The formulated mathematical model of stationary modes of the heat pump drying unit with artificial cooling of the dried material can be used to evaluate the feasibility and energy efficiency of the used refrigeration machines for grain cooling, especially after high-temperature processing. The obtained analytical dependences in the form of a closed system of equations can be used to optimize the parameters of the heat pump drying unit by the criterion of minimizing energy consumption.

Incorporation of Fluid Compressibility into the Calculation of the Stationary Mode of Operation of a Hydraulic Device at High Fluid Pressures

This paper is concerned with assessing the correctness of applying various mathematical models for the calculation of the hydroshock phenomena in technical devices for modes close to critical parameters of the fluid. We study the applicability limits of the equation of state for an incompressible fluid (the assumption of constancy of the medium density) to the simulation of processes of the safety valve operation for high values of pressures in the valve. We present a scheme for adapting the numerical method of S. K. Godunov for calculation of flows of incompressible fluids. A generalization of the method for the Mie – Grüneisen equation of state is made using an algorithm of local approximation. A detailed validation and verification of the developed numerical method is provided, and relevant schemes and algorithms are given. Modeling of the hydroshock phenomenon under the valve actuation within the incompressible fluid model is carried out by the openFoam software. The comparison of the results for the weakly compressible

Numerical method for solving the problem of the gas-dynamic state of a main gas pipeline section relief of a variable cross-sectional area

The paper proposes a numerical method for solving the problem of the gas-dynamic state of a main gas pipeline linear section, which is characterized by a path change in the diameter and leveling height of the pipeline axis. The quasi-one-dimensional equations of gas pipeline transport are derived with account for the local and convective components of the inertia force, the quadratic law of resistance and the force of gravity at a variable cross-sectional area of the pipeline. At the inlet to the section, a time change in hydrostatic pressure is set, and at the outlet from the section a mass rate of gas flow is set. The initial distribution of gas-dynamic indices was taken for a stationary mode of operation. The equations were transformed to the equations of direct and reverse traveling waves presented in dimensionless variables, and approximated by an implicit scheme, taking into account the direction of excitation propagation. The iterative processes were formed by virtue of the nonlinearity of equations and boundary conditions, A calculation program was developed that allowed studying the process dynamics depending on the time change in the inlet pressure and the outlet mass flow rate under a path change in the diameter and leveling height of the pipeline axis. The results of separate calculations on transient processes were presented, when, at the section outlet the mass flow rate increases abruptly, and the pipe diameter has a local increase according to a sinusoidal law.

A Mathematical Model of a Three-Phase Induction Motor with a Phase Rotor

A mathematical model of an induction motor (IM) with a phase rotor is developed on the basis of the usual assumptions that does not use the supposition that there is an annular rotating field in its air gap and various transformations of coordinates. The model is valid for both transient and steady-state modes and with various ways of control by changing the parameters of the three-phase feeding voltage system of the IM stator coil. It is shown that the desired stationary operation mode that exists in the developed nonlinear IM model at a constant feeding voltage of the stator and load torque corresponds to the constant electromagnetic torque and spinning frequency of the rotor at sine-wave rotor and stator currents. A digital IM model is developed in the MATLAB system. An analytical solution is derived for the system of linear differential equations that describes the IM with a retarded rotor and allows evaluating the nonlinear digital model for correctness. Examples of applying the IM model in analyzing transient and steady-state operation modes of this motor are provided.

Assessment of Residual Service Life of Cast Bodies of Control Valves of 220 MW Power Units

In the regulatory documents of the Ministry of Energy and Coal Industry of Ukraine, the beyond-design operating life of the high-energy equipment of 220 MW power units is limited to the operating life of 220 thousand hours and 800 start-ups. To date, the high-temperature cast bodies of the control valves for the high- and intermediate-pressure cylinders of the K-200-130 200 MW steam turbines of DTEK Lugansk TPP have operated about 305–330 thousand hours with the total number of start-ups from 1438 to 1704, which exceeded the beyond-design service life characteristics. Therefore, it is necessary to assess the residual operating life of the control valve bodies of the high- and intermediate-pressure cylinders of K-200-130 steam turbines in order to determine the possibility of their further operation. These calculations were carried out on the basis of our earlier studies of the thermal and stress-strain states of cast turbine equipment. This paper establishes the values of stress intensity amplitudes, the values having been reduced to a symmetric loading cycle for the most typical variable operating modes. Using the experimental low-cycle fatigue curves for the 15Kh1M1FL steel, we established the values of the permissible number of start-ups and the cyclic damage accumulated in the base metal. We also determined the value of the static damage accumulated in the course of stationary operating modes according to our previously obtained experimental data on the long-term strength of the 15Kh1M1FL steel. The calculations showed that the total damage to the control valve bodies of the K-200-130 steam turbine of power unit 15 of DTEK Lugansk TPP is 97 and 98%. The residual operating life of the metal of the control valves of high-pressure cylinders is practically exhausted, being equal to 10 thousand hours. The residual life of the control valves of intermediate- pressure cylinders is 7 thousand hours, i.e. it is also practically exhausted, with safety factors for the number of cycles and strains at the level of 5 and 1.5, as well as the permissible 370,000 operating hours of the metal. With an increase in the permissible operating life of the metal to 470 thousand hours, according to experimental studies of Igor Sikorsky KPI, the total damage to the metal of cast valve bodies is reduced to 80%, and the residual metal life increases to 79,000 h and 75,000 h for the control valves of the high- and intermediate-pressure cylinders, respectively.

Numerical simulation and study of thermal characteristics of a lightweight floor heating system

The use of underfloor heating systems is an effective way to achieve thermal comfort for users in energy-efficient buildings. There are two kinds of such systems: traditional and dry-assembled. The first type is researched more deeply than the second one. The paper presents theoretical studies of the thermotechnical parameters of a water underfloor dry-assembled heating system. The design of the underfloor dry-assembled heating system, considered in the work, consists of a heat insulation (expanded polystyrene), on which the pipes of the heating system are located, in contact with an aluminum heat distribution plate. The system is covered with floor finishing. The calculation for a stationary operating mode of the floor heating system was carried out on the basis of a system of equations for momentum and energy. The model was validated using the results of experimental studies. The calculation results cause some overestimation of the experimental data, possibly, beecause of deviations in thermotechnical characteristics of materials. But the simulation model correctly estimates the behaviour of the system at change of its parameters. The paper concludes that this configuration of the underfloor heating system can be used in heating systems for residential and non-residential premises. The aluminum heat distribution plate significantly affects the heat transfer processes in the system. Due to the plate, the heat flux is made uniform in the plane of the floor surface, which has a positive effect on heat distribution and reduces thermal tension in the finish coating. The use of ceramic tiles increases the overall heat exchange efficiency of the system with the room air. An increase in the thickness of the expanded polystyrene board increases the value of the heat flux from the surface of the heated floor. An increase in the flow rate and temperature of the heat carrier also cause an increase in the density of heat flux from the floor surface.

Calculation of the speed characteristics of an upward swirling gas flow under conditions of side wind

The paper presents the results of numerical modeling of lateral wind effects on three-dimensional unsteady air flows in an upward swirling stream of an artificially created tornado in a stationary mode of operation. The mathematical model is the complete system of Navier-Stokes equations taking into account the viscosity and thermal conductivity of a moving gas, as well as the action of gravity and Coriolis. Using an explicit difference scheme and an appropriate choice of initial and boundary conditions, solutions are obtained numerically for the complete system of Navier-Stokes equations in the computational domain in the form of a rectangular parallelepiped. All components of the gas flow velocity were calculated at fixed time instants and
 instantaneous streamlines were constructed with constant horizontal wind direction taken into account. The calculations showed that the result of the wind effect on the upward swirling flow is an asymmetric change in peripheral speed, its uneven
 deformation in opposite sections, and the total displacement of the vortex in the direction of the wind. In addition, the displacement and curvature of the vertical part of the vortex in the direction of the wind was established, a “detachment” of some instantaneous streamlines from the vertical rotating part and the appearance in the center of the vortex of an area that is free of streamlines increasing in diameter were recorded. In the studied time variation range, the stability of the air vortex to wind action and the stable operation of the used computational scheme are observed.

Peculiar properties of transient processes in cascades with additional product flow

One of the important stages in the campaign for separation of multicomponent isotopic mixtures is bringing the separation cascade to a stationary mode of operation. This process, depending on the applied separation method, can be characterized by a relatively long time with associated consumption of the working substance and operating costs. Therefore, the search for the values of the control parameters of the cascade at which it is possible to reduce the transient process time is practically a significant problem in the theory of isotope separation in cascades. One of the current trends in the modern theory of cascades is the study of physical laws of stationary mass transfer in cascades with additional outgoing flows. Such cascades can find application for solving a number of urgent problems, in particular, obtaining relatively high concentrations of isotopes with intermediate masses. At the same time, the laws of unsteady mass transfer in such cascades remain poorly understood. The paper analyses the key patterns of transient processes in a square cascade with an additional product flow. The interconnections between the time of bringing such a cascade to the stationary mode and the external conditions under which the process of separation of the mixture occurs are revealed.

Cyclic and square-wave voltammetry for selective simultaneous NO and O<sub>2</sub> gas detection by means of solid electrolyte sensors

Abstract. Solid electrolyte gas sensors (SESs) based on yttria-stabilized zirconia (YSZ) are suitable to detect traces of redox components in inert gases. Usually, their signals are generated as a voltage between two electrodes at open circuit potential or as a current flowing between constantly polarized electrodes. In these rather stationary modes of operation, SESs often lack the desired selectivity. This drawback can be circumvented if SESs are operated in dynamic electrochemical modes that utilize the differences of electrode kinetics for single components to distinguish between them. Accordingly, this contribution is directed to the investigation of cyclic voltammetry and square-wave voltammetry as methods to improve the selectivity of SESs. For this, a commercial SES of the type “sample gas, Pt|YSZ|Pt, air” was exposed to mixtures containing NO and O2 in N2 in the temperature range between 550 and 750 ∘C. On cyclic voltammograms (CVs), NO-related peaks occur in the cathodic direction at polarization voltages between −0.3 and −0.6 V at scan rates between 100 and 2000 mV s−1 and temperatures between 550 and 750 ∘C. Their heights depend on the NO concentration, on the temperature and on the scan rate, providing a lower limit of detection below 10 ppmv, with the highest sensitivity at 700 ∘C. The O2-related peaks, appearing also in the cathodic direction between −0.1 and −0.3 V at scan rates between 100 and 5000 mV s−1, are well separated from the NO-related peaks if the scan rate does not exceed 2000 mV s−1. Square-wave voltammograms (SWVs) obtained at a pulse frequency of 5 Hz, pulses of 0.1 mV and steps of 5 mV in the polarization range from 0 to −0.6 V also exhibit NO-related peaks at polarization voltages between −0.3 and −0.45 V compared to the Pt–air (platinum–air) electrode. In the temperature range between 650 and 750 ∘C the highest NO sensitivity was found at 700 ∘C. O2-related peaks arise in the cathodic direction between −0.12 and −0.16 V, increase with temperature and do not depend on the concentration of NO. Since capacitive currents are suppressed with square-wave voltammetry, this method provides improved selectivity. In contrast to cyclic voltammetry, a third peak was found with square-wave voltammetry at −0.48 V and a temperature of 750 ∘C. This peak does not depend on the NO concentration. It is assumed that this peak is due to the depletion of an oxide layer on the electrode surface. The results prove the selective detection of NO and O2 with SESs operated with both cyclic voltammetry and square-wave voltammetry.

Calculation of the speed descrioptions of the upward swirling gas flow in conditions of lateral wind action

The paper presents the results of numerical simulation of lateral wind impact on three-dimensional non-stationary air flows in ascending vortex flow of artificially created tornado in the stationary operating mode. The mathematical model represents a complete system of Navier-Stokes equations taking into account the viscosity and thermal conductivity of the moving gas, as well as the effects of gravity and Coriolis. Using the explicit difference scheme and the corresponding choice of initial and boundary conditions, the solutions of the complete system of Navier-Stokes equations in the computational domain representing a rectangular parallelepiped are numerically obtained. All components of gas flow speed are calculated at fixed time points and instantaneous current lines are built taking into account the constant horizontal wind speed. The calculations showed that the result of the wind action on the ascending vortex flow is an unsymmetrical change in the circumferential velocity, its uneven deformation at opposite sections, and the total displacement of the vortex in the wind direction. Besides, the displacement and the curvature of the vertical vortex part in wind direction are established, the “separation” of some instantaneous current lines from vertical rotating part and the area in the vortex center increasing in diameter, free from current lines is fixed. In the studied time change range, the wind resistance of the air vortex and stable operation of the used computational scheme are observed.

Estimation of creep of the turbine control valve body at increased steam temperature

The influence of the temperature of the supplied steam on the operating and strength characteristics during creep of the control valve body of the steam turbine K-325 is considered. Currently, the valves are operated with steam supply with a pressure of 24 MPa and a temperature of 540°C. The analysis of the effect of increasing the temperature of the supplied steam up to 565°C. The study was carried out in connection with a possible increase in steam temperature to increase the power of the turbine. The temperature and pressure of steam on the walls of the vessel are determined based on the numerical solution of the Navier-Stokes equations in a three-dimensional setting. It was found that an increase in the temperature of the supplied steam has little effect on the nature of the distribution of temperature and pressure on the walls of the valve body. Temperature fields and steam pressure on the walls of the valve body are used to further solve the problems of the strength of the control valve bodies of the K-325 turbine in a stationary mode of operation. The stress-strain state of the valve body of a steam turbine in a stationary mode of robots is numerically determined. The problem was solved by the finite element method in a three-dimensional setting. The results showed that the maximum elastic stresses on the outer surfaces are observed in the region of the upper transition of the inlet pipe. On the inner surfaces, the maximum values of elastic stresses are observed in the area of the branch pipes in front of the control valves. It was determined that an increase in the temperature of the supplied steam up to 565°C insignificantly affects the stress state of the valve body. The creep of the body was calculated using a model of implicit creep with hardening, taking into account the variable and constant creep components. The influence of the temperature of the supplied steam on the creep of the valve body is estimated. The results indicate that an increase in the temperature of the supplied steam by 25°C leads to an increase in creep deformation by a factor of 2.3 after 200 thousand hours of operation. Temperatures, pressures, and equivalent stresses are plotted at the body surfaces and creep curves are plotted at 540°C and 565°C.

Mathematical modeling of gas-liquid flow in compressed air foam generation systems

The object of research is the compression foam supply system. One of the most problematic areas in the design of compression foam supply systems is the need to obtain a certain type of foam with the necessary properties, depending on the class of fire for which it will be used to extinguish. It is necessary to take into account the technological process of foam formation, namely, the regulation of the flow of the foaming agent solution and compressed air, which are fed into the mixing chamber, where the foam is generated directly. It is important to ensure optimal parameters depending on the purpose of the foam outlet flow installation: flow rate, foam ratio and foam stability. In order to design a compression foam supply system with certain technological parameters, it is necessary to obtain these parameters analytically in advance, for which it is necessary to construct an appropriate mathematical model.In the course of the research, let’s use the Simulink graphical simulation environment (integrated into the MatLab software environment), which allows building dynamic models using separate blocks in the form of directed graphs. The structure of such a model is built on the basis of separate, independent blocks, which in themselves are separate mathematical models.New is the development of a mathematical model of a two-phase flow: a liquid phase consisting of a mixture of water with a foaming agent and a gas phase - air in the foam generator path as part of a block diagram of an installation for the case of generation of compression foam. And also the development of a scheme and communication algorithm for serially connected blocks of a common block diagram. This ensures the receipt of the calculated output data of the stationary mode of operation of the installation.The mathematical model developed in this work allows solving the following applied and scientific problems:– to carry out calculations of the input parameters of the installation, which will provide the required output parameters: flow power, frequency ratio, continuous generation time, foam resistance, determined by the purpose and features of the installation in conditions of extinguishing various types of fires;– to investigate the influence of the parameters of the foam generation insert of the installation on the expansion of the compression foam.

Evaluation of the efficiency of a small-sized electrothermal micro-thrusters with autonomous heating elements

The work is aimed at solving urgent tasks – improving the efficiency of electrothermal micro-thrusters (ETMT) for microsatellites weighing up to 50 kg. The purpose of this work is to evaluate the effectiveness of a small-sized ETMT with Autonomous heating element (AHE) with a diameter of 4 mm on the basis of experimental studies. In the course of experimental studies, the ETMT temperature characteristics were determined for electrical power consumption in the range of 3-30 W using “cold” and “hot” switching schemes. The effectiveness of small ETMT with AHE diameter of 4 mm is a significant increase in temperature AHE and, as a result of heating of the working fluid and reducing the time of reaching the stationary mode of operation compared to ETMT with AHE diameter of 6 mm. The results of experimental studies have shown that a small-sized ETMT be successfully used in microsatellites correction propulsion system (CPS) with a power output of 10-30 W.

Computer modeling of electrochemical processing of waste nuclear fuel

The purpose of the work is to study the influence of the electrodes geometry and the mutual arrangement of functional elements in the working space of a metallization electrolyzer on the distribution of the oxygen flux density in the electrolyte, as well as on the distribution of electric and temperature fields. In a computer model, the stationary operation mode of the electrolyzer for processing spent nuclear fuel immersed into the LiCl molten salt with the addition of Li2O was studied. The calculations were performed using the ANSYS software package. We studied eight designs of the electrolyzer, which differ in the immersion depth of the anodes into the melt as well in the types anode protective covers and the cathode baskets. Verification based on the comparison of the computer modeling with experimental data indicates the adequacy of the models used. The electrolyte velocity field and the temperature field are calculated, as well as the steady-state picture of the distribution of electric current density over the working space of the electrolyzer. The efficiency of the electrochemical cell is determined.

Model Predictive Controller-Based Optimal Slip Ratio Control System for Distributed Driver Electric Vehicle

The slip ratio control is an important research topic in in-wheel-motored electric vehicles (EVs). Traditional control methods are usually designed for some specified modes. Therefore, the optimal slip ratio control cannot be achieved while vehicles work under various modes. In order to achieve the optimal slip ratio control, a novel model predictive controller-based optimal slip ratio control system (MPC-OSRCS) is proposed. The MPC-OSRCS includes three parts, a road surface adhesion coefficient identifier, an operation mode recognizer, and an MPC based-optimal slip ratio control. The current working road surface is identified by the road surface adhesion coefficient identifier, and a modified recursive Bayes theorem is used to compute the matching degree between current road surfaces and reference road surfaces. The current operation state is recognized by the operation mode recognizer, and a fuzzy logic method is applied to compute the matching degree between actual operation state and reference operation modes. Then, a parallel chaos optimization algorithm (PCOA)-based MPC is used to achieve the optimal control under various operation modes and different road surfaces. The MPC-OSRCS for EV is verified on simulation platform and simulation results under various conditions to show the significant performance.

Improving reliability of turbine units of TPPs and NPPs with mixing heaters in regeneration system

When developing designs of mixing heat exchangers used in low-pressure regeneration system for turbines with power from 200 to 1200 MW of TPPs and NPPs, special attention is paid to protecting the turbine flow parts from dripping moisture. Many years of work of JSC "NPO CKTI" on the research, development and implementation of low-pressure heaters (LPH) have shown that their installation in the vacuum zone of the condensate path, as well as in the zone of relatively low overpressure, ensures the maximum cost-efficiency and reliability of the turbine plant regeneration systems. However, an insignificant difference in operating pressures in the LPH and the heating steam from steam turbine extractions, typical for connection options for heaters, requires the development of additional organizational and technical measures to prevent water from entering the turbine. For stationary operating modes, there are two stages of protection against rising levels in the apparatus, providing reliable removal of water through the emergency overflow system or by stopping condensate pumps. In cases of emergency load dump of a turbine unit, the process of increasing the level in the LPH is much faster, up to boiling the entire volume of condensate. The article discusses the possible conditions for the formation and penetration of droplet moisture into the flow part of the turbine. Analysis of well-known field and laboratory studies of the operation of LPH in the most unfavorable operating conditions (in particular, load shedding of a turbine unit) is carried out. A description of the process of boiling water in mixing LPH during turbine load shedding is given. A variant of methodology for estimating the time of swelling of the water level in mixing LPH is proposed. The presented theoretical justifications make it possible to estimate the time of formation and growth of bubbles in deaerated water. The physical process under study is characteristic of the operating conditions of mixing heaters of the low-pressure regeneration system of turbine units and is of interest from the point of view of substantiating the action speed of the system for turbine protection from moisture entering the turbine with a return steam flow.

Non-Cryogenic Technology of Production of Helium Concentrate from Natural Gas

A non-cryogenic technology has been developed for the extraction of helium from natural gas in a membrane installation operating in an unsteady mode. The separating membrane in this setup consists of microcapsules – cenospheres. The microscopic dimensions of the walls of such capsules provide a high diffusion rate of helium, unattainable in installations with a stationary mode of operation. A wave technique for calculating membrane installations with an unsteady mode of operation has been developed. The calculation is carried out by expanding the input concentration signal in a Fourier series according to the eigenfrequencies of this periodic process. Moreover, each of its concentration eigenwaves, independently of the others, passes through a layer of microcapsules. At the output, all solutions for individual eigenwaves are added up. Using a specific example of the extraction of helium from natural gas, the capabilities of the new technology are demonstrated. It is shown that the transmission of natural gas through an installation with three apparatuses 10 m long filled with cenospheres makes it possible to achieve a helium recovery coefficient of 33%.