Vol 66, No 6 (2019)

For designing different heat and power equipment with a wide range of applications, it is necessary to measure the fields of thermophysical characteristics (temperature, pressure, velocities, etc.) in as much detail as possible. At the same time, the deployment of complex diagnostic methods is often impossible. Therefore, it is most practical to use movable probes that move in the flow and make measurements at separate points. The use of such scanning measurement methods is a complex task that requires the solution of many mechanical and thermophysical problems. The techniques of scanning probe measurements for determining thermal characteristics in the flows of various media are described. A review is given concerning the development of probe-based investigation methods since the 1960s. Joint probe developments concerning the probes made by the scientific group of the Engineering Thermophysics Department of the National Research University Moscow Power Engineering Institute and the Joint Institute for High Temperatures, Russian Academy of Sciences, for two-dimensional and three-dimensional temperature and velocity measurements in water and mercury flows are presented in detail. The experience in the development and use of scanning probes is summarized in three main designs, such as a hinged probe, a probe with eccentricity, and a longitudinal probe. Descriptions, methods of application, and the features of their operation are considered for these designs. The results obtained by using the probes of various designs in the course of experiments with water and mercury are considered. The choice of a required technique is substantiated depending on the preset conditions of the problem, such as the geometric characteristics of the investigated area, the presence of a magnetic field, the influence of thermal and gravity factors.

Among the methods for improving the performance of high-temperature gas turbines in gas-turbine engines (GTE) and gas-turbine units (GTU) is the implementation of transpiration cooling of the blades, since the maximum allowable temperature of blades with convective- or film-cooling ranges from 1800 to 1900 K. The basic advantage of this cooling method is in decreasing the required coolant flow due to extended-contact heat-transfer surface. Transpiration cooling systems employ porous metal materials. However, the effect of geometry of porous materials on air flow and heat transfer in them is still not clearly understood. The paper presents the results into investigation of models with a transpiration cooling system made of sintered stainless-steel fibers. The geometric characteristics of the investigated models depended on the material porosity. The thermal tests of the models were performed by the calorimetric method in a liquid-metal thermostat, while the hydraulic tests were carried out by the hot blow method under isothermal conditions. The experimental results can be entered into the database used by heat transfer software packages, thereby decreasing the labor intensity and time for designing a cooling system for gas turbine blades. The implementation of transpiration cooling offers the prospects for increasing the maximum allowable gas turbine temperature up to 2200 K.

This is the third paper on experimental research and optimization of combustion in the fuel-air mixture in the two-zone combustor at outlet gas temperatures of 1550–1700°C with meeting the requirements for harmful substances (NO_x and CO) emissions. The experimental results on combustion of gaseous fuel in the combustor with two consecutive combustion zones are presented. Each zone has its own burner: the first burner is traditional and located at the end of the flame tube, while the second burner is sequential and located downstream on side walls of the flame tube. Fuel combustion in the second zone occurs at a low oxygen content and high temperature. Zones with maximal CO values ​​are shown to be formed near the flame tube walls, while maximal NO_x concentrations are observed in the central zone of the flow recirculation. The penetration capacity of the fuel jets entering the second combustion zone was evaluated, and the jet trajectories in the blowing flow of hot gases in the first zone are shown. The results of optimization of the fuel distribution between two successive combustion zones, as well as the effect of the flow rate on the NO_x and CO formation at the outlet gas temperature of 1550–1700°C, are presented. The results were obtained by testing the model low-emission combustor at the test facility of the All-Russia Thermal Engineering Institute.

The effect of magnitude and direction of the axial thrust during steam turbine transients on the starting technology is investigated. The behavior of the axial thrust during start-up of a steam turbine with a combined high/intermediate pressure cylinder operating in a single-bypass or two-bypass thermal cycle is presented. At different stages of start-up, varying steam pressure at the turbine inlet and in its flow path can result in a change in the temperature of thrust bearing pads and the magnitude and direction of the axial thrust acting on them. During start-ups with a two-bypass thermal scheme for steam admission to the turbine and its rotor acceleration, connection of the steam turbine generator to a grid and its initial loading are performed with steam supply through intermediate pressure-control valves. In this case, the high-pressure cylinder (HPC) is under “negative pressure” or “countercurrent” conditions passing steam from the exhaust via the bypasses of the check valves in the “cold” reheat steam lines and removing this steam to the condenser via the drains of high-pressure crossover pipelines and from the high-pressure cylinder casing. Connection of the turbine HPC for normal steam supply and change-over to the once-through scheme of steam admission to the turbine are carried out after connection of the turbine generator to the grid and initial loading of the turbine by partial opening of the HP control valve and full opening of the intermediate pressure (IP) control valves. At the same time, the valves of quick-acting pressure-reducing and cooling units (QAPRCU) BROU-1 and BROU-2 are closed to maintain the specified high and intermediate pressure of steam upstream from them. These process operations change the axial thrust acting on the thrust bearing pads with a corresponding change in the pad temperature. The effect of variable axial thrust on the steam turbine maneuverability is examined. Methods are proposed for balancing the axial thrust during start-ups of steam turbines in combined-cycle units having different thermal schemes.

Protection of the containment integrity is one of the key objectives pursued in managing a severe accident at an NPP. Possible hydrogen inflammation in the containment can be regarded as the most dangerous threat for the containment integrity. Inert state of a steam–air–hydrogen mixture can be secured by maintaining a high steam concentration. With a steam concentration above 55%, the mixture is in an non-flammable state whatever the concentrations of its other components. The containment reinforced concrete walls lined with metal sheets behave as heat sinks with a very high thermal inertia. Heat removal through walls may have a significant influence on the mixture composition in the containment or in its individual part (especially if the rooms have comparatively small volumes) if part of steam from the mixture undergoes long-term condensation, as a result of which its concentration in the mixture decreases. The article presents an investigation, by means of detailed modeling, of the heat transfer processes through the walls of containment rooms with a view to reveal factors that are of importance in considering hydrogen challenge. It is found that the wall surface area to the room volume ratio is a factor having an effect on the formation of dangerous hydrogen-containing mixture compositions. It is shown that the wall heat absorption capacity decreases only slightly in the course of an accident. In rooms with a small volume, there may be a real risk that the medium in them may quite quickly lose its inertness as a result of heat removal through the walls. The possibility of a detonation mixture to form is not even excluded. In the case of a severe accident, there will be a risk of dangerous hydrogen-containing mixture compositions formation in small rooms within the containment irrespectively of the strategies implemented for the containment’s main rooms unless special measures and means are taken, e.g., application of accident management strategies or installation of hydrogen recombiners.

The power industry, primarily its branch based on fossil fuel resources, is the major source of anthropogenic carbon dioxide emissions into the atmosphere of the planet. Based on direct measurements and some paleogeophysical data, it is shown that the carbon dioxide content in the atmosphere is currently increasing at a rate that exceeds by an order of magnitude its increase over the last several thousand years. Some methods for solving the global problem of reducing CO₂ emissions caused by combustion of fossil fuels and basic technologies used for this purpose are considered. The main CO₂ emission sources are identified. Based on the analysis of international statistical data, it is shown that large-scale fossil-coal-fired power-generating plants account for the greater part of the emissions. The existing CO₂ capture technologies and those under development and intended for use in industrial power generation are compared and the prospects of their practical implementation are evaluated. The increase in the cost of the electric power generated within the full cycle of capturing CO₂ from flue gases of large-scale power stations and storing it using the best-established technologies ready for introduction has been assessed. The basic factors that increase the cost of the power generated using the technologies for carbon dioxide emission sequestration have been determined and potential change in the prices in the future have been considered. The presented results suggest that the problem of drastic reduction in CO₂ emissions requires a comprehensive approach and cannot be solved by efforts of only a limited number of industrially developed countries. The necessity of coordinated introduction of measures aimed at carbon dioxide emission sequestration not only in the “large-scale” power generation but also in other industries is shown.

It is demonstrated that reverse osmosis (RO) technology with two stages with respect to filtrate and without any additional water treatment is adequate for makeup water treatment for natural circulation drum boilers with an operating pressure as high as 13.8 MPa. Production of filtrate with electric conductivity below 2 μS/cm, which can be used for the preparation of make-up water without ion exchange processes, can reduce capital and operating expenditures and improve the reliability of water treatment systems at thermal power stations where feasible and appropriate. Application of monotechnology, i.e., reverse osmosis, can reduce the load of engineering personnel and improve the operation stability of a water treatment unit even under conditions of seasonal variation in the analysis of raw water. The paper demonstrates that a stable decrease in the salt content by a factor of 1000 can be achieved under certain conditions with a salt content in natural raw water as high as 1 g/dm³. The effect of carbon dioxide that makes it more difficult to produce water with very low electrical conductivity is considered. Methods are described for effective removal of carbon dioxide, including decarbonization with the use of an ejector. The presented expressions enable us to quickly evaluate the salt content of the filtrate depending on the selectivity of a membrane element (ME), even determined experimentally; to solve the inverse problem, i.e., calculate the true selectivity of ME based on the measured parameters that cannot be calculated using standard software of ME manufacturers; in developing new projects, consider a decrease in the ME selectivity during operation using available experimental data on ME performance; and to predict quality and improve operation of the overall demineralization system in water treatment plants (WTP). The mathematical substantiation and the theoretical limit for application of the examined technology with respect to the salt content of the source water are presented. The results of the experiments on the use of this technology at the sites of operating thermal power stations (TPS) without decoding the latter are given.