Том 52, № 2 (2018)
- Год: 2018
- Статей: 20
- URL: https://journals.rcsi.science/1570-145X/issue/view/15324
Hydrotechnical Construction
Improving Overall Performance of Propeller-Type Hydroturbines with the Use of Variable Rotational Speed
Аннотация
Reconstruction of axial hydroturbines by installing propeller-type blade runners with variable rotational speed is examined. The calculation methodology for energy indicators of such turbines according to their Hill chart is presented. The effectiveness of transferring hydroturbines to operation with variable rotational speed is shown, using the example of the Cheboksary HPP. In this case, power generation increased by 16% using the same volume of water passing through the turbines. At the same time, the turbine adjustment range widens in comparison with the traditional propeller-type units operating at constant rotational speed.
Article
Packing Density of the Sandy Soil of Foundations and Structures
Аннотация
Results of field and laboratory investigations on filling and deposition of sandy soil in water, the results of statistical sounding, and sampling of packed sandy soil in water in the absence of flow and in the case of a moving flow of water as well as following dynamic compaction of soil are presented.
Evaluation of Performance of the Water-Supply System of a Navigable Sluice with Short Bypass Galleries
Аннотация
An analysis of studies to improve the dissipating devices of the water-supply systems of navigable sluices is presented. Using as an example a projected low-pressure sluice, recommendations are given for determining the volume of the quenching chamber, the area of the outlet spaces of the galleries, the length of the stilling area, and the constructive layout of the outlet trenches and on the horizontal block screen
Calculation of Horizontal Pressure of Backfill on a Round Wall
Аннотация
Atechnique of designing a round wall in design by means of which the nature of the operation of the structures and the combined work of the backfill and the wall, the shift (displacement) of the wall, and the angle of internal friction may be taken into account is proposed. The proposed expressions are recommended for use in designing the retaining walls of embankment and fish protection structures.
Assigning the Packing Density of Skeletal Clay Soil in the Dam Core
Аннотация
The issue of compacting skeletal clay soil by generalizing the grain-size distributions of rock mass and gravel-pebble soil is considered. Soil grain-size distributions are described by Talbot’s exponential equation. Diameters of 1, 2, and 5 mm are chosen to differentiate between clay and coarse-grained soils. It is shown that this choice is of little applied value and a diameter of 5 mm can be definitely used. Clay soil and rock mass can be used in a 1:1 proportion while clay soil and gravel-pebble soil in a 2:3 proportion. There can be other ratios as well.
Seafloor Scour Near Gravity Platforms from the Frontal Impact of Regular Waves and Currents
Аннотация
The results of experimental investigations of seafloor scour near the foundations of gravity platforms under the frontal impact of regular waves and currents are presented. The effect of current velocities on the location of the scour zone relative to the structure is determined.
Accumulation of Corrosion-Fatigue Damage by Hydro Turbine Equipment Elements
Аннотация
Questions are considered for evaluating material damage and substantiation of life on the basis of corrosion-fatigue crack development kinetics. Linear fracture mechanics are used for this approach suitable for large and small cracks, which makes it possible to include a nominal initial crack l0 among basic material properties. Calculated curves for fatigue in an aqueous medium based on 1010 cycles, and the curves for fatigue damage accumulation corresponding to 106 and 1010 cycles are provided for specimens with a cross section of 180X200 mm of steel 06Kh12N3D in rolled and cast conditions. Results are provided for evaluation of the life of during action of two-stage loading and repeated overloading.
Effect of Waterproofing Penetrating Capillary Mixture on Concrete Waterproofness and Cement Stone Microstructure
Аннотация
Results are provided for a study of concrete waterproofness, structure, and properties of cement stone treated with penetrating water insulation system Penetron. It is shown that formation of waterproofed concrete facilitates formation within cement stone pores of an additional amount of low-basicity calcium hydrosilicate of acicular shape and also calcite.
Stress-Strain State in the Deformation of the Rogun Dam During the Construction Period
Аннотация
The stress-strain state and stability of the Rogun Dam are investigated under the action of static loads, taking into account the time and stage-by-stage construction in conditions of flat and spatial work. Three variants of the core width at the base of the dam are considered. Comparison of the options showed that the configuration of the canyon has significant effect on the efficiency.
Evaluation of Concrete Structure Condition of the Volzhskaya Hydroelectric Power Plant
Аннотация
During the reconstruction of the Volzhskaya HPP, it is very important to determine the properties of the concrete and the strength parameters of the structures and buildings of the HPP. During field studies, the durability of concrete under monoaxial compression was measured and the velocities of elastic waves were determined. Based on completed tests, a large amount of data that makes it possible to evaluate the strength parameters of the entire HPP building was selected. According to the results examined in this article, it is possible to predict the formation of defects in concrete. The tendency for the durability of concrete structures in the direction to decline in the direction from the right bank to the left is revealed.
Draft Tubes of Water Turbines in Underground and Semi-Underground Powerhouses
Аннотация
The effect of the centerline radius, bend angle, and diffuser length of high draft tubes in underground and semi-underground powerhouses on head losses is studied analytically. It is established that the dependence of the head losses on the diffuser length does not depend on the capacity, flow rate, and runner diameter of the water turbine; therefore, the diffuser length should be consistent with the construction conditions, but no greater than 35 – 40 m. The centerline radius r0 of the elbow increases with its bend angle α.
Primorskaya Thermal Power Plant: Construction of Modern Pulverized Coal-Fired Boilers
Аннотация
The main design solutions for coal-fired boilers of the Primorskaya TPP under construction are described. Boilers E-240-13.8-560KT with a tangentially fired furnace were designed to burn Kuznetsk bituminous coal and operate as part of 65 MW units. Features of the design coals, main design solutions for coal pulverizing systems, design features of the boiler, and a low-NOx combustion system are considered. The layout of the boiler and boiler auxiliaries in the main building of the power plant is presented. Particular attention is paid to the aspects of emission reduction and the environmental compatibility of the boiler. The main design solutions for the integrated dry bottom ash removal system that allow using resulting ash and slag materials as saleable by-products are described. The results of 3D-simulation of the burning processes and expected NOx emissions and unburned carbon are given.
Parametric Computational Studies of NOx Emission Reduction in Staged Combustion of Ideal Fuel-Air Mixtures1
Аннотация
This paper is the second of series of articles devoted to computational studies for optimization of the combustion of fuel-oxygen mixtures with combustion chamber exhaust temperatures of 1600°C or more while meeting pollution emission standards. Calculations of the combustion of ideally mixed fuel-air mixtures in a combustor consisting of two sequentially positioned (staged) combustion volumes, each with its own burner, are presented. The first burner is a traditional low-emission combustion chamber with combustion of a pre-mixed fuel-air mixture with a swirler and a pre-mixing chamber, and pilot and main burners. The second burner lies downstream in the flow and a fuel-air mixture with a different composition is fed into it through a special aperture; this mixture is burnt in a medium with reduced oxygen content and a high temperature. The distribution and composition of the fuel-air mixture feeds between the two burners are optimized to attain minimum NOx emissions for outlet temperatures of 1700°C. The optimum length of the second combustion volume is determined for complete burnup of the fuel with minimum concentrations of the oxides of nitrogen and carbon at its outlet. The results can be used to evaluate the minimum possible level of nitrogen oxide emissions attainable in the sequential combustion scheme for ideally mixed fuel-air mixtures.
Method of Numerical Simulation of the Vibrations of a Stator Core
Аннотация
An analytic method of calculating the eigenfrequencies of the vibrations of a stator core based on its representation as a lengthy thick-walled cylinder is proposed. The effective physical and mechanical properties of the core are determined with the use of the method of direct homogenization in order to reduce the dimension in direct numerical simulation of the heterogeneous composite structure of the core.
Wave Simulation Model of an Electrical Network Using the Operator Method
Аннотация
Amethod of creating a wave model of an electrical network is examined, taking into account key components of the network: objects with lumped and distributed parameters. The model can be easily adapted for a specified electrical circuit. A solution is proposed using the operator method. The model parameters can be determined based on experimental data.
Recognition of Weak Harmonic Signal Components in Generator Protection Against Single-Phase Earth Fault
Аннотация
For single-phase earth faults (SEF) in a generator network, the higher harmonic components are a good information base for relay protection of the generator against single-phase earth faults. Because of the low signal-to-noise ratio, they are not available for direct measurement. Anew method of active-adaptive recognition of similar signals is proposed. The results of testing a prototype of the generator protection device with an active-adaptive analog-to-digital converter (ADC) path confirm the high effectiveness of the proposed method.
Statistical Methods of Mode Recognition in Relay Protection and Automation of Power Supply Networks
Аннотация
Microprocessor relay protection and automation (RPA) devices open up broad opportunities for realization of the most complex algorithms. Since traditional power system overcurrent RPAs have insufficient sensitivity and speed, this paper proposes new multi-hypothesis methods of recognizing modes of operation in RPA of power systems, based on statistical principles. An example is given of using the developed algorithms of relay protection (RP) with an assessment of their effectiveness.
Verification of Distance Relay of Relay Protection and Emergency Control Automation Equipment in Asynchronous Mode by Standard Devices of the RETOM Test Complex
Аннотация
A technique of calculating the parameters of a mathematical model of a power system that forms part of the standard software package of the RETOM-51(61) device is considered. The goal is to verify the remote element of the relay protection equipment and emergency control automation system in asynchronous mode. A numerical example is presented of the calculation of the parameters of the model for verifying the serial automation device to exit asynchronous mode of operation in remote mode.
Thermal Power Plants
Properties and Pulverized Coal Combustion of Low-Reactivity Fuels. Part II. Furnace and Burner Equipment1
Аннотация
In case of the low volatile content and low heat of combustion of the volatile matter, external factors play a more important role in stabilization of the flame, than in the case of reactive coals. The paper offers a review of solutions for improving the design of the swirl burners, their arrangement and furnace layout.
Power Systems and Electric Networks
Electromagnetic Situation Near Gas-Insulated and Cable Power Lines
Аннотация
Gas-insulated and XLPE cable power lines can be used as high-power outputs from power plants and deep inputs of power to big cities. When laying power cables in a populated area, it is important to ensure a low level of electromagnetic field. The magnetic-flux density for specific designs of gas-insulated and XLPE cable lines is calculated for different shield-grounding methods and arrangements of cables. The calculated results are analyzed.