Thermal Engineering最新文献

A brief overview of methanol-production technologies is presented. Methanol produced using Power-to-Fuels technology has been shown to be a promising fuel. Electrolysis of water generates hydrogen, which reacts with carbon dioxide. The result of this reaction is methanol. Flue gases from power plants can provide a fairly concentrated stream of CO₂ for this reaction. Particularly promising in such hybrid schemes is the use of biomass for the production of electricity using an electrolyzer as a source of CO₂. The schemes for producing methanol using fluidized bed technology during biomass combustion are considered in which the generated electricity is sent to an electrolyzer to generate hydrogen and the CO₂ flow is sent to the methanator. Another promising technology is gasification in chemical cycles. Technologies for producing methanol with a minimal carbon footprint are described. New schemes based on circulating fluidized bed (CFB) technology for combustion and gasification of biomass are proposed. Estimates of the performance of a system with a pressurized CFB boiler and a gas turbine for woodchip combustion in boilers, as well as a system using chemical cycles for woodchip gasification, have been performed. Technical and economic indicators, including the reduced cost of methanol, were determined during the life cycle of the plant. The scheme with allothermic gasification and chemical cycles for producing hydrogen seems to be the most promising. It allows to significantly increase the production of methanol. While the implementation of hybrid schemes with CFB boilers can use well-proven equipment, schemes with gas generators and chemical cycles require the use of new, as yet commercially untested solutions.

The results of modeling changes in the structure of electricity and district heat production on the horizon up to 2050 under the influence of scenarios of stagnation or rising gas prices in a wide range are presented. Estimates of changes in the cost-optimized scale of development of thermal power plants (TPPs) and their contribution to the production of electricity and centralized heat in Russia have been obtained. The influence of price scenarios in the gas market on the efficiency of the development of gas and coal-fired thermal power plants, including cogeneration (CHP), on the dynamics of increasing their energy efficiency, as well as on trends in reducing total greenhouse gas emissions from power plants, is analyzed. The dependencies of multidirectional changes in demand for gas and coal in the electric power industry and restrictions on the revenue growth of gas suppliers in the largest segment of the domestic market are obtained. The ranges of investment needs of the electric power industry and the required electricity prices are estimated. The effects of the transition to higher gas and electricity prices on the country’s GDP (including the impact of investment multipliers) have been determined using intersectoral multiagency models.

The article presents modern environmental requirements and the current state of the art in the field of cleaning flue gases from sulfur dioxide at thermal power plants in Russia and abroad. The most promising methods of flue gas desulphurization for implementation in the near future at thermal power plants in Russia are presented, and the experience of the All-Russia Thermal Engineering Institute (VTI) in the design and implementation of such installations is described. The experience of creating a domestic industrial highly efficient and waste-free installation for cleaning exhaust flue gases of thermal power plants from sulfur dioxide with a capacity of 1.5 million m³/h (under normal conditions) using ammonium sulphate technology, the final product of which is fertilizer, is considered. The technical solutions applied in the development of the basic design of this desulphurization system are presented based on the experience of developing a pilot industrial plant using ammonia-sulphate technology (AST) at the Dorogobuzhskaya TPP and taking into account the characteristics of the fuel being burned as well as the results of mathematical modelling of a device for introducing flue gases into a gas precooling apparatus (prescrubber). The article presents the results of the development of a project for a simplified “wet-dry” flue gas desulphurization unit with an efficiency of up to 50% for a boiler with a steam capacity of 670 t/h as well as the results of mathematical modeling of the process of injecting lime suspension droplets into the flue gas flow in the prechamber of an electrostatic precipitator and their evaporation. The article presents data on the preliminary feasibility study of the use of wet limestone desulphurization technology (WLDST) to reduce sulphur dioxide emissions taking into account the requirements of environmental legislation for a number of thermal power plants in Russia.

In immersion, two-phase cooling systems for micro- and power electronics, where the permissible heating temperature should not exceed 85°C, dielectric liquid HFE-7100 is widely used. To increase the heat-transfer coefficient (HTC) and critical heat flux (CHF) values during boiling of HFE-7100 liquid, mesh coatings are used. The results of systematic experiments on single-layer and multilayer mesh coatings made of stainless steel with boiling liquid HFE-7100 in horizontal layers are presented. The liquid layer height varied in the range from 1.5 to 25.0 mm at pressures of 100 and 50 kPa. The experiments were performed using wire meshes with a diameter of 100 and 220 µm with cell side of 230 and 401 µm, respectively. The heat-transfer coefficient values obtained on the multilayer mesh coating are higher than those on the surface without meshes by 35% at all pressures considered. At a saturation pressure of 100 kPa, the increase in the critical heat flux values q_cr on mesh coatings is almost 60%, while that at a saturation pressure of 50 kPa is approximately 214% compared to q_cr on surfaces without meshes. The maximum values of the critical heat flux on single-layer mesh coatings shifts towards thinner liquid layers of 8 mm in height compared to the value q_cr on a 16-mm-height layer on a smooth surface.

The temperature of condensed phase particles formed during flame combustion of peat from Kirov oblast in a BKZ-210-140F boiler was studied using a pyrometric method. The authors elaborated an experimental-and-calculation procedure for pyrometry of the furnace enabling determination of the temperature of condensed phase particles (of coke and ash) in the gas phase transparency band. The measurements were taken using Raynger R3I 2MSC and Kelvin 2300 PLTs pyrometers having radiation receivers operating at a wavelength of 1.6 µm and in a spectral range from 1.0 to 1.6 µm, respectively. Dependences are obtained of the temperatures measured at different heights from the boiler furnace bottom to the measurement point (hereinafter referred to the boiler furnace height) (H = 9, 14, and 16 m), on the emissivity set on the pyrometers in the range from 0.1 to 1.0. Spectral and integral radiative energy flux densities sensed by the pyrometers were calculated. Brightness temperatures observed during peat combustion were determined. The software package developed by the authors was used for computational studies of the condensed phase emissivity as a function of the specified temperature considering the fuel burnout along the furnace height by solving the radiative transfer equation for a multicomponent radiating, absorbing, and scattering medium. The intersection of the experimental and predicted functions gave the emissivity and true temperatures of the condensed phase particles. According the measurements taken by the Raynger pyrometer, the particle temperature in the flame root part (H = 9 m) is equal to 1453 K; it is 1226 K in the flame middle part (H = 14 m) and 1334 K in the flame tail part (H = 16 m). For the Kelvin pyrometer, these temperatures were 1471, 1265, and 1343 K, respectively. The obtained particle temperatures enabled us to assess the risk of melting of the mineral part of the fuel and slagging of the furnace.

The article presents a review of the embodiments, in terms of construction material used (or shortly material embodiments), of the main heat transfer devices, namely, a vapor generator, condenser, and regenerative heat exchanger in the case of their optimal—in the authors’ opinion—use in the design of a thermal oil ORC unit. A shell-and-tube type device was considered for implementing both the thermal oil heated vapor generator and the water cooled condenser. A semi-welded plate device was also considered as an alternative to the latter. For an air cooled condenser, the material embodiment versions of devices with finned tube and microchannel heat transfer surface, and for the regenerative heat exchanger, versions with a plate-and-finned surface were studied. The choice of the most rational heat transfer, thermal insulation, and structural materials is substantiated with due regard to the specific features of the working media used. The currently-in-force regulatory documents stipulating the material embodiment of heat exchangers with suitable process operating conditions are analyzed, and an attempt is made to put the information in a systematic order using the experience of manufacturers as a basis. It has been found that the published catalogs of industrial equipment do not contain sufficient data on the materials used, technologies for connecting heat transfer elements (tubes with the tube sheet, plates, and heat exchanger components), and working media. As regards the proposals on the choice of material embodiment, they are limited to just one or two solutions. On the contrary, the regulatory documents present more various versions of materials. In the scientific-technical literature, materials that have not been yet put in operation and have not been included in standards are considered; however, they form promising ways for the development of this area. The performed analysis of all of the above-mentioned information sources enabled us to draw up recommendations on the optimal material embodiments for each of the devices considered, which ensure compliance with the unit’s operating conditions, including the temperature ones.

An analysis of greenhouse gas emissions from Russian energy sector was carried out in accordance with the Energy Strategy until 2050, and they were compared with the target indicators of the Low-Carbon Development Strategy of Russia until 2050. It was shown that fundamental trends in the development of global energy—the energy transition associated with the decarbonization of the global economy—were not taken into account when developing the Energy Strategy. The actual refusal to develop renewable energy sources and the failure to use carbon dioxide capture and storage technologies make it impossible to achieve the goal of carbon neutrality for the national economy by 2060, even taking into account the new increased estimates of carbon absorption by Russian forests. Ignoring the global trend towards abandoning coal fuel, recorded by authoritative national and foreign energy agencies (the Institute for Energy Research of the Russian Academy of Sciences, the International Energy Agency), has led to inflated estimates of Russian exports of this type of fuel, the world trade of which will decrease several times by 2050. Refined estimates of methane leaks during oil and gas production in Russia correspond in specific values to the indicators of other major producers of oil and gas resources (the United States and Canada), but are approximately two times lower than those obtained from the Earth’s remote sensing data. The main provisions of the two strategic documents on Russia’s development until the middle of the century contradict each other to a certain extent and, therefore, cannot be implemented simultaneously. The result of these contradictions could be Russia’s refusal to fulfill its pledges to decarbonize the economy and its withdrawal from the Paris Agreement, which will undoubtedly exacerbate the confrontation with growing global trends.

The problem of deep purification of industrial gases of various impurities is urgent. The purification is usually performed using adsorption and absorption technologies, which are implemented using two-phase turbomachines with bulk condensation of the impurity in the flow path. The study is devoted to numerical simulation of the process of bulk condensation in the flow path of a radial-type refrigeration turbomachine, which is controlled by changing the flow-expansion ratio in the turbine. It is a direct continuation of the work wherein control of the process by changing the initial flow temperature was investigated. The working fluid was a mixture of air as an incondensable gas carrier and carbon dioxide as an impurity. It has been demonstrated that the process of bulk condensation proper and its depth can be controlled by changing the flow-expansion ratio. The conditions have been determined at which the process is localized predominantly in the impeller channels thereby reducing the risk of erosive wear and subsequent damage to the stage elements. For the first time, the reduction in the isentropic efficiency caused by condensation controlled by changing the flow-expansion ratio was numerically estimated for refrigeration turbomachines. The obtained data are close to the values for wet steam turbines presented in the literature. A procedure for calculating the characteristic and analyzing the results has been developed. It yields the optimal regimes using a multicriteria search with the requirements for the region where the phase transition should occur, and for the mean radius of the particles. It is shown that changing the expansion ratio may be insufficient to meet the specified requirements for the degree of condensation and isentropic efficiency offering deep purification of gases of impurities. Therefore, assessment is required as to whether the process rate can be controlled by changing the expansion ratio, the initial flow temperature, and the impeller speed.

Considered are NHFR or net heat flux reduction data in order to illustrate and quantify turbulent thermal convection phenomena within a unique and intricate cooled film environment along the extremity end of a transonic turbine airfoil with a rim in the form of a squealer. Of particular focus are the consequences of modifying the magnitude of GAP (tip gap magnitude) which is adjacent to the outer end of the airfoil. Data are given for a variety of cooled film ratio of blowing conditions, as the coolant film is provided by two separate plenums that are connected to a row of holes which are located along the top segment of the concave surface of the blade, as well as to two dusting cooled film holes located on the end extremity of the blade. Line-averaged NHFR data show different dependence upon RoB_u and RoB_d ratios of blowing, depending upon the magnitude of GAP. Especially for the trailing edge portion of the squealer tip surface of the airfoil, NHFR data vary significantly with aft ratio of blowing RoB_d for the 1.2 mm or smaller GAP arrangement, whereas very little variation with RoB_d is present for the 2.0 mm or larger GAP environment. Here, GAP is the thickness of the flow gap at the blade tip. In addition, line-averaged NHFR data associated with the smaller GAP are often higher than values associated with the larger GAP, when compared for the same squealer surface airfoil tip locations, and at the same approximate RoB_u and RoB_d ratios of blowing. The flow and local static pressure variations within tip gap regions, which vary as the magnitude of GAP is changed, are less influential in regard to the data associated with the top portion of the concave surface of the two-dimensional airfoil. The impact of the present arrangements and configuration is new and unique NHFR results for different GAP values for complex boundary layer and separation flow environments, which are different from all other data which are available within the archival literature.

The article presents the results of an analysis of applied and fundamental research carried out by leading global universities and companies on burner devices designed for burning liquid hydrocarbon fuels in the presence of superheated water vapor used in thermal power engineering, including those developed taking into account patent information. Directions for increasing the efficiency of burner devices and their main developers and manufacturers have been identified. On the market of liquid fuel burners used in thermal power engineering, there are universal burners designed for burning different fuels, including substandard ones. Such burners are difficult to maintain, and their operation is accompanied by loud noise and emissions of harmful substances into the atmosphere. Despite the significant shortcomings of liquid fuel burners offered on the market, steam burners are not being introduced into industry, remaining at the stage of pilot industrial samples. Improvement of burner devices is aimed at solving such problems as energy saving, reduction of emissions of harmful substances, simplicity of devices, and their versatility in the type and quality of fuel burned. Companies in the United States, Japan, China, the Republic of Korea, and Russia are conducting research and actively filing patents for burner devices, with the Kutateladze Institute of Thermophysics (Siberian Branch, Russian Academy of Sciences (IT SB RAS)) being among the top ten patent holders. Steam burners are patented for use in 25 areas of technology, primarily in the field of “thermal processes and apparatuses.” Moreover, patent-holding companies hardly sell patents for burner devices and their elements and do not provide licenses for their use but use them in their own production. The work carried out by the authors allows us to determine the level of third-party technologies in comparison with the technologies of the Kutateladze Institute of Thermophysics (Siberian Branch, Russian Academy of Sciences) and to develop recommendations for further research based on patent, scientific, and other published information.