Vol 31, No 3 (2023)
Information Technology and Communications
Modeling of the removal of combustion products in the pipe of a low-rise building as a control object
Abstract
The features of the formation and methods of preventing condensation in the chimney of an apartment low-rise building with an individual decentralized heat supply system are considered. A mathematical model of the technological process of removing flue gases from gas boilers in an apartment building through a collective chimney pipe as a multidimensional control object with distributed parameters, which is understood as a set of thermophysical processes occurring during the removal of combustion products. Numerical simulation of a collective chimney pipe is performed on the example of a three-storey apartment building with gas boilers installed in each apartment as a control object. A method of step-by-step experiments is proposed. At the first stage, the dependences of the distribution of the temperature field inside the chimney during non-stationary operation of boilers and changing ambient temperature are obtained. The phenomenon of condensate occurrence has been confirmed experimentally, and the most characteristic areas subject to its occurrence have been identified. During the second stage of research, it was found that it is most effective and economically feasible to prevent the formation of condensate by using a heating cable in the attic and chimney head sections. It is shown that the change of control actions has an effect on the temperature of adjacent sections of the chimney. The revealed non-stationarity is taken into account by inter-channel connections through the object in the block diagram. It is proved that, in relation to solving the problem of removing combustion products from the chimney, an object with distributed parameters can be represented by a model with concentrated parameters, for which the structure is synthesized and proper operators and operators of inter-channel connections are found in the form of transfer functions with variable parameters. The resulting model is problem-oriented to create a two-dimensional automatic temperature control system on the inner surface of the chimney in order to prevent the formation of condensate in the pipe.
6-21
Optimization of combined thermal circuits gas turbine expander power plants
Abstract
In this paper, thermal schemes are proposed and the principle of operation of combined power plants of a new type for a thermal power plant is given. Thermodynamic analysis of parameters of thermal circuits of combined power gas turbine expander plants was carried out depending on the outside air temperature, electric and thermal loads of the thermal power plant, as well as the flow rate of natural gas through the gas distribution point consumed by the thermal power plant. Based on the results of the calculation, optimization of the power plant cycle parameters was carried out, providing the specified electric power and efficiency of the gas power turbine. It has been found that its electric power and efficiency depend on the flow rate of natural gas supplied to the thermal power plant in different months of the year and the corresponding air temperatures. The most efficient combined plant is a system in which turbo expanders are connected to the turbocharger shaft of a typical GTU or complementary to a typical GTU by a turbo expander compressor unit. The use of a new type of combined gas turbine expander power plants seems to be the most effective solution for increasing the generation of electric energy and increasing the thermal efficiency of thermal power plants.
22-42
Feedback control of operating gates of a shipping lock using a system of rules
Abstract
The problem of positional control of the working gates of a shipping lock as a multidimensional control object with lumped parameters is considered. A general formulation of the problem is given, including requirements for the final and intermediate states. When solving the problem, it is proposed to use a productive model of the regulator in the form of a system of rules. The numerical method for solving the problem is based on representing the control algorithm in the form of an a priori non-fixed and time-varying system of rules determined during the control process. The presented results of numerical modeling confirm the effectiveness of the proposed method for determining the positional control of objects of this type.
43-54
Telematics and diagnosis system for autonomous cargo vehicle
Abstract
The article deals with the problem of managing the operation and maintenance of autonomous trucks KAMAZ using a telematics and diagnostics system. The functions and composition of the onboard module of a robotic vehicle are described. The main controlled values are determined. The presence of a developed system for monitoring the state of units and assemblies provides a solution to the problem of controlling the modes of the car operation. The structure of the telematics and diagnostics system has been developed and implemented. The main blocks of the proposed system are shown. The main diagnostic and forecasting functions are performed on a workstation with an analytical module. It is proposed to use an approach based on previous conditions matrixes. An example of matrix analysis for a car engine cooling system is given. Modeling of the engine cooling system was carried out and graphs of transient processes were obtained. The analytical module is designed using artificial neural networks to analyze time series of car parameter values. To conduct virtual tests of a car in various operating modes, a simulation model was developed on a stochastic time colored Petri net. The model simulates both the movement of the vehicle to the point of production operations and the change in the technical condition of the car. The model makes it possible to describe and study the influence of random factors on the time of execution of production tasks, to take into account the probabilistic characteristics of failure events or defects in vehicle components and assemblies. The use of an artificial neural network in the analytical module of the diagnostic system workstation makes it possible to predict the technical condition of vehicle components and systems in real time, followed by verification of the dynamics of processes on a simulation model on a Petri net.
55-68
Electronics, Photonics, Instrumentation and Communications
Development of software for information-measuring Systems for frequency analysis of binary-quantized Signals
Abstract
The article discusses the methodology and design template for a complex of structurally, functionally, informationally and metrologically compatible software modules that implement algorithms for calculating estimates of the PSD power spectral density based on binary-signed analog-stochastic quantization with reduced multiplicative complexity. Algorithmic support makes it possible to calculate PSD estimates by the method of averaged modified periodograms and by the correlogram method using time correlation windows based on a discrete-event representation of the results of binary-sign analog-stochastic quantization. This approach made it possible to perform integration operations analytically, which eliminates the methodological error caused by performing these operations in digital form. In addition, the multiplication operations degenerate into procedures that basically require the execution of logical operations and simple arithmetic operations of summing and subtracting the values of the correlation windows, which significantly reduces the complexity of estimating the PSD.
69-82
Energy and Electrical Engineering
Influence of nano-oil preparation conditions on its electrical strength
Abstract
This study presents the results of experiments aimed at determining the breakdown voltage of liquids containing carbon nanotubes and other microinclusions; which were dispersed in mineral insulating oil used in electrical transformers. The liquid was obtained by various methods with the mandatory use of ultrasonic dispersant. The electrical strength of the carbon nanotube-based nano-oil was found to be significantly less than the electrical strength of the zinc and titanium nano-oxide-based nano-oil. At low concentrations the values of electrical strength approximately correspond to the values of electrical strength of pure liquid; but with increasing concentration the electrical strength of all nanofluids decreases. It is shown that the nanofluid preparation technology has a strong influence on its breakdown voltage.
83-97
Selection of output inverter for microgrid
Abstract
The paper considers the problem of a microgrid output inverter selecting, when information about operating conditions is uncertain. The following factors are considered as sources of uncertainty in information about operating conditions: the possibility of the load increasing in the area, for which the microgrid is being designed, the prospects for its integration into the local power supply system, based on the microgrid, operating in the given region, as well as possible changes in the element base due to import substitution.
A system of criteria and a methodology for optimal selection have been developed, based on a combination of multi-vector optimization approaches and the hierarchy analysis method. The quality criterion of generated energy, the criterion of reliable operation in conditions of information uncertainty and the criterion of economic indicators were cho- sen as vector criteria. The total number of scalar criteria that are components of the specified vector criteria is seven. At the first stage of selection, an algorithm is used for expert assessment of the importance of vector criteria and their scalar components, as well as values of these criteria for compared alternatives, using of the hierarchy analysis method. At the second stage of selection, considered inverters are ranked according to a global criterion, calculated based on results of the first stage. The technique is demon- strated by choosing between three well-known schemes of autonomous inverters: a voltage inverter with PWM-shaping of the output curve, a current inverter with a variable struc- ture and a group multilevel inverter based on a universal source of levels, when they are operating in autonomous or integrated into the system of other microgrid modes. The de- scribed selection technique can be used, when other microgrid conversion equipment de- vices are selecting.
98-114
Determination of the rational shift value the center of the magnetic system electromagnetic bearing
Abstract
The article sets the task of determining the rational value of the displacement of the center of the magnetic system of an electromagnetic bearing relative to the axis of rotation, at which, with equal currents in opposite electromagnets, the weight force falling on one axis of the bearing will be completely compensated. To achieve the set, the equations of motion of the rotor in the field of electromagnets are considered. It is shown that the rational value of the displacement of the center of the magnetic system is determined from a fourth-order algebraic equation. The analytical solution of Descartes-Euler of this equation is applied. Analytical expressions are found that allow to determine the rational value of the displacement of the center of the magnetic system relative to the axis of rotation according to the known parameters of the electromagnetic bearing. A study was made of the stability of a three-circuit control system of an electromagnetic bearing when the center of the magnetic system is shifted by a rational value relative to the axis of rotation. It is proved that the displacement of the center of the magnetic system by the calculated value does not affect the stability of the control system of the electromagnetic bearing with the settings of the regulators selected for the central position of the rotor.
115-124