卷 52, 编号 4 (2018)

Types of coastal protection structures are distinguished. Requirements imposed on wave parameters and sea levels when calculating structures of a certain type are examined.

The results of numerical modeling of the hydraulic operating regimes of the Bagaevskaya low-head hydro complex are presented. Three computer models of different scales are constructed: a local model of the hydro complex for checking and refining the layout solutions, investigating its conveying capacity, velocity regimes, and downstream bed deformation; model of the Bagaevskaya reservoir for determining the backwater curves, navigable depths, and rate of water exchange; global model of the Lower Don valley from the Kochetov hydro complex to the Taganrog Bay for determining the stage-discharge rating curve in the tailwater, zones and depths of floodplain flooding during passage of discharges of small exceedance probability, and effect of setup and setdown phenomena. The results of the calculations are used for developing the hydro complex project.

The essence of this technique is based on calculation of the spatial design of a segmental gate together with its bearing hinge. The study of the metal structure of a segmental gate and bearing hinge is performed for the obligatory three calculation combinations. The results of the calculation are: the stresses and strains at any point of the metal structure of a gate and the bearing hinge, the stresses at the welded seams, the reserve factors of stability and strength of the design, and the forces at the sites of suspension brackets and in base bolts.

Securing of temporary hydrotechnical structures (water-filled, panel-mounted, and other types of dikes) of different heights by means of flat earth anchors and screw piles designed to protect population centers and infrastructure against large-scale floods is considered.

Two methodologies for navigable lock chamber calculation are analyzed. Preliminary calculation was performed using the finite element model and Construction Specifications (CS) techniques. The feasibility of calculation using the finite element model was assessed and compared with manual calculation; the advantages and shortcomings of the techniques under consideration were manifested. Conclusions on the expediency of applying this method of lock chamber calculation of a dock design have been reached.

An estimate of the phase transition zone location in the flow section of the T-150-7.7 steam turbine operating as part of a 450 MW two-circuit combined cycle gas turbine unit during various modes of operation is provided. Stages were identified, in which stress corrosion cracking of the disks, as well as corrosion fatigue of the rotating blades are most likely to appear.

Features of noise emission from gas distribution stations (GDS) and their gas pipelines are considered. It is shown that the noise from the gas flow in the channels is substantially lower than the noise from the control valves at high flow rates. The noise from the GRS building is maximum. It is established experimentally that the noise level decreases with distance from the GRS at a constant distance (10 m) from the gas pipeline when the major noise source is the control valves.

The influence of the currents of higher harmonic components on the operation of the electrical equipment of a power system with a high fraction of electrical receivers with nonlinear volt-ampere characteristic is considered. It is shown the presence of transient currents of higher harmonic components in the stator coil of a synchronous generator leads to a substantial increase in the losses of power both in the stator coil and in the rotor coil. Results of an estimate of the influence of the currents of higher harmonics on the operating regime of the generator are presented. It is suggested that when a synchronous generator functions in a power system containing electrical receivers with nonlinear volt-ampere characteristic its power-carrying capacity should be reduced to prevent unacceptable heating of the generator. The thermal processes in a synchronous generator functioning with nonlinear loads are considered. The permissible power-carrying capacity of a synchronous generator with different fractions of electrical receivers with nonlinear volt-ampere characteristic is calculated.

Analysis is provided of the processes of change of magnetic induction in the magnetic core of power transformers during measurements of windings resistance to direct current. A methodology was developed to calculate the time needed for exit to measurement mode. It is shown that this time is proportional to the ratio of the rated winding voltage to the voltage from the power supply of the measuring device. It is noted also that the time needed for exit to the mode of measurement of windings resistance to direct current on the side cores is less than the analogous time for the winding on the central core. The methodology has been confirmed with practical measurements on the power transformers of the Donbass electrical power system.

Recognition of turn-to-turn faults in the series winding of an autotransformer is studied. At one time the conclusion had been drawn regarding a low, even zero, sensitivity of the transformer differential relay protection (TDP) series and distance remote protection to this type of damage. Modern microprocessor-based terminals for transformer protection, in addition to traditional differential current protection with percentage braking, provide sensitive differential protection on return sequence currents. Adaptive differential measurements can become a new tool for detection of developing internal damage. By means of a simulation model of the 500 kV autotransformer, measurements of the above-mentioned algorithms are constructed for turn-to-turn fault in a series winding. Analysis of the obtained results is carried out.

This paper is the third in the series of publications devoted to computational studies on optimization of the combustion of a fuel-air mixture with the gas temperatures at the outlet of the combustion chamber reaching about 1600îC or more, while satisfying the harmful emissions requirements. The paper provides the calculation results related to the combustion of gaseous fuel in a combustion chamber (CC) consisting of two consecutively positioned combustion volumes, each of which is provided with its own burner unit (BU). The first BU is typical for low-emission combustion chambers (LECC) and contains swirlers and zoned mixture preparation, as well as pilot and main burners. This unit is fed with an ideally mixed fuel-air mixture (FAM). The second BU is positioned downstream of the first combustion zone. It is fed with gaseous fuel (natural gas) without pre-mixing with air. In the second zone, a diffusion combustion process is realized. Two BU designs were considered for the second zone. In the first design, the fuel is supplied from behind a bluff body (throat) serving to create a flame stabilization zone. It also contains a fuel manifold. The fuel is supplied through the special openings in the mouth of the throat. The second design represents an annular manifold positioned around the flame tube and fuel supply tube embedded by 15 mm. This design does not provide for a special arrangement of the flame stabilization zone. In both cases, the combustion of fuel of the second zone occurs in the oxygen- deficient environment and at high temperature. The obtained results demonstrate the optimized fuel distribution between the two combustion zones, as well as optimized number and diameter of the fuel supply openings and length of the second combustion zone to ensure the lowest NOx emissions at the exhaust gas temperature of 1700°C and high fuel combustion efficiency. The results allow estimating the minimum possible concentrations of nitrous oxides in the dual-zone combustion chamber with a diffusion second zone. A comparison of the dual-zone fuel combustion schemes during kinetic and diffusion combustion in the second zone is provided. It is shown that kinetic combustion provides a significant benefit in terms of NOx concentrations, both with respect to a single combustion zone and two zones with the diffusion second zone. The simplicity of the design of the diffusion second zone is attractive, however, it provides a smaller reduction in NOx concentration.

The operating conditions of a turbine-generator with the stator winding short-circuited to the frame are analyzed. The features of the shape of the zero-sequence voltage during arcing in the damaged gap are described. The operation of the relay protection in these conditions is analyzed. The real oscillograms of the subsequent suppression of the rotor field are theoretically justified. It is shown that improving the thyristor excitation system is necessary and possible.