Characteristics Of Transient Process Research Articles

Transient Process Analysis of Oscillating Motion in Oscillating Heat Pipes

Abstract During the startup phase, oscillating heat pipes (OHPs) exhibit a transient process in which the working fluid moves erratically until a steady-state oscillatory flow is attained. Understanding the transient process is important to predict how long it takes an oscillating heat pipe to reach normal operation and realize its heat transfer potential after it is started. In this paper, we perform a theoretical study of the transient process of oscillating heat pipes. Based on a one-dimensional mathematical model, we obtain an analytic solution that allows us to predict transient process characteristics of oscillating motions in an oscillating heat pipe, as well as the impact that different design and operating parameters have on this transient process.

TRANSIENT PROCESSES IN ELECTRICAL COMPLEX OF PRODUCTION WELL WITH DOWNHOLE COMPENSATOR OF REACTIVE POWER

Link for citation: Glazyrin A.S., Isaev Yu.N., Kopyrin V.A., Timoshkin V.V., Kladiev S.N., Khamitov R.N., Kovalev V.Z., Losev A.F., Leonov A.P., Popov E.I. Transient processes in electrical complex of production well with downhole compensator of reactive power. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 5, рр.168-180. In Rus. The relevance. At the present time at routine complication of technological processes to increase efficiency of production processes due to introduction of new equipment conflicts between functional capabilities of various technical means and their ability to function with specified quality, in specified electromagnetic environment and do not create inadmissible electromagnetic interference to other technical means. The electrical engineering complex for oil production includes a combination of ground and submersible electrical equipment assembled for receiving, transforming electrical energy, controlling its flow, converting electrical energy into mechanical energy and transmitting it to a submersible pump, including various electrical and electronic devices: a control station with a frequency converter, a step-up transformer, a cable line, a submersible electric motor, a downhole reactive power compensator and other devices. Any change in the layout of electrical systems for extracting oil or technical characteristics of the equipment used requires careful analysis of transient processes between the operating modes of electrical equipment in order to prevent the risks of false triggering of electrical equipment protection devices. The purpose: analysis of transient processes in the electrical system of the production well with the downhole reactive power compensator when the power supply is disconnected in order to prevent the risks of false operation of the compensator protection devices. The object: section of a power supply system for a cluster of oil producing wells equipped with electric centrifugal pump installations with downhole reactive power compensators. Methods: positions of theoretical bases of electrical engineering, theory of electric drive, theory of differential equations, numerical methods. Results. The authors developed the mathematical model of the electrical system of the submersible unit for oil production with a downhole reactive power compensator, which enables to investigate transient processes in start-up and shutdown mode of the submersible induction motor. Characteristics of transient processes are obtained in elements of electrical complex of submersible plant for oil production when power supply is switched on and disconnected. It is established that the maximum current surge in the downhole reactive power compensator is 2,56 times with the parameters of the electrical system of the production well accepted in the study. The inventive measures for reducing the number of false actuations of the protection devices are also disclosed.

THE DIFFERENT APPROACHES TO THE TRANSFORMATION OF REACTIVE POWER INTO AN ACTIVE POWER

The relevance of the development of modern problems of the electric power industry in connection with the depletion of the planet’s natural resources is undeniable and initiates the development of new physical and technical solutions with the practical use of known natural phenomena. The method of this work is to propose, justifying the expediency of a possible scheme of a resonant converter of reactive power into activity and conducting an analysis of the electromagnetic processes occurring in them. The proposed schemes combine the presence of resonant parallel and resonant circuit complexes. The difference is in the way they are implemented. For the data of the joint circuit, the feature is the presence of two inductively coupled active-reactive circuits, but different in the ways of creating resonance conditions. For a circuit without an additional power source, it is shown that the successful implementation of resonance conditions is possible by choosing the appropriate element base. For a circuit with an additional source of harmonic voltage, it is shown that for a suitable setting it is possible to completely eliminate the negative influence of the converter circuit on the source of reactive power. Calculations for the experimental model show that with the appropriate selection of the element base, it is possible to obtain a conversion factor of ~ 1.0 with a minimal effect on the current in reactive power sources. Given the calculated ratios, the mathematical apparatus of the theory of electric circuits was used to substantiate the principle possibility of resonant transformation of electrical energy. Thus, methods of calculating the characteristics of transient processes in closed circuits with active-reactive elements. For the first time, with the justification of practical power, we offer the possibilities of the scheme of resonant transformation of reactive power into active power, and an analysis of the electromagnetic processes occurring in them is carried out. The proposed work was initiated by the current needs of the electric power industry, caused by the depletion of natural resources and the rapidly growing needs of the world economy. The results of the work illustrate the practical possibilities of creating real schemes for converting reactive electricity into active electricity.

Numerical investigation on characteristics of transient process in centrifugal pumps during power failure

Centrifugal pumps are widely applied in engineering practices. Power failure occurs occasionally and consequently the flow field inside the pump is extremely complex. Pump parameters fluctuate greatly with time during power failure, and such fluctuations cause high pressure pulsations in the flow and vibrations in the pump system. In this work, the transient process caused by the power failure of a centrifugal pump is simulated using ANSYS CFX, along with a user-defined function developed to solve iteratively the angular momentum equation for calculating pump rotational speed. Experiments are conducted to obtain the external characteristic curves and pump runaway parameters. Results show that the characteristic curves and runaway parameters of the pump predicted by numerical simulations are in good agreement with experimental ones. After power failure, the transient process experiences mainly four modes, namely, pump mode, braking mode, turbine mode and runaway mode. The variations of pump characteristic parameters with time are examined in detail. Furthermore, internal flow fields during the transient process are analyzed and compared to improve the understanding of flow behavior after pump power failure.

Improvement of the control process of the heat treatment of iron ore pellets in the preheating area of the conveyor-type roasting machine

The object of research is the process of heat treatment of iron ore pellets. To study it, a technological zone of pre-heating of a conveyor-type roasting machine was used. Technological process control is performed on the basis of fuzzy and incomplete information about the state of this zone. One of the main requirements regarding the functioning of the technological preheating zone is to ensure the regulatory values of the thermal and gas modes when changing the speed of movement of the conveyor belt carts. Efficiency improvement of control of these modes is provided thanks to the automatic control system, implemented on the basis of fuzzy and incomplete information on the state of the technological parameters of the zone.In the course of the study, the analysis of scientific and technical information was carried out and the analytical method determined the importance of improving the process of controlling the thermal process of processing iron ore pellets in the technological preheating zone. On the basis of experimental studies, the features of the technological process have been taken into account, it requires the improvement of the process of controlling the operation of the technological preheating zone. The mathematical model uses the temperature of the coolant of the gas-air flow, the flow rate of natural gas and air, the temperature of the pellet bed and their mass on the carriages of the conveyor belt of the machine. At the same time, the output technological parameters of the drying zone and the input parameters of the firing zone are taken into account.On the basis of solving systems of fuzzy functions and the principles of parametric identification, a mathematical model is proposed that approximates the dynamics of the thermal process of processing iron ore pellets in the technological preheating zone. The characteristics of transient processes of heat treatment of pellets obtained on mathematical models are analyzed taking into account the variable parameters of the adjacent technological zones of the machine, the consumption of natural gas and air. On the basis of mathematical modeling, studies have been carried out to determine the optimal distribution of the coolants of the gas-air flow over the technological preheating zone. The hardware and software for the automatic control system for the heat treatment of pellets taking into account the variable parameters of the coolants of the gas-air flows in the technological preheating zone has been implemented.

СИНТЕЗ LQG РЕГУЛЯТОРА ДЛЯ ИНТЕЛЛЕКТУАЛЬНОГО УПРАВЛЕНИЯ ТЕХНОЛОГИЧЕСКИМ ПРОЦЕССОМ ТОНКОГО ПОМОЛА

The article presents the development of a linear-quadratic Gaussian controller (LQG) for intelligent control of the fine grinding technological process. The LQG regulator was designed to control the quality of mill output. The developed LQG controller takes into account external disturbances (process noise) and noise in measurements modeled as white noise with a Gaussian distribution. The controller is developed on the basis of a combination of a stationary linear quadratic controller (LQR) and estimation of the state of the Kalman filter (LQE) in the stationary state by solving the matrix Riccati equation in order to determine the feedback gain and Kalman gain. In the course of work: a mathematical model of the grinding process is built, an analysis of the frequency characteristics of the obtained model is made; the model was checked for stability, controllability, and observability; on the basis of the model, the LQG regulator was synthesized. Transient process characteristics confirm precise control. Modeling is implemented in the MATLAB environment.

Method development of statistical modeling for the description of welding fume emissions in gas metal arc welding using transient process characteristics

In the past, most approaches to reduce welding fume emissions were primarily based on welding consumables, whereas in the context of the present work, a new concept with direct reference to the welding process technology is pursued. Many other measures to improve occupational health and safety, such as use of extended personal protective equipment (e.g., forced air ventilated helmets) and extraction systems, relate to the reduction of immissions of welding fumes already emitted. In comparison, the selection of optimized parameter settings in terms of gas metal arc welding (GMAW) provides a process-related possibility to reduce welding fume emissions without the need for additional equipment. In order to illustrate and quantify the functional interdependencies between process parameterization and the resulting fume emission generation, a model relationship is developed which is primarily based on empirical investigations. Via post-process analysis, certain features are extracted from the transient measurement data and correlated with the process-specific emission rates. With the help of the model, individual parameters can be iteratively set on the basis of representative process features. Besides parameter optimization with regard to emission-reduced processes, a forecast of the expected fume emission rate can be derived based on the selected settings. The methodology described and examined is applicable to different process spaces of GMAW or even other fume-emitting welding processes.

SYNTHESIS OF THE NOISE IMMUNE ALGORITHM FOR ADAPTIVE CONTROL OF ORE CONCENTRATION

Annotation Context. Consideration of the transient process characteristics under current industrial conditions, i.e. a controlled object’s static and dynamic characteristics when forming controlling impacts in automatic control systems of ore grinding and sizing is one of the advanced ways to increase their efficiency. Variations in characteristics of initial materials and equipment conditions while changing a command value in closed-loop automatic control systems (ACS) result in transient processes when the granularmetric composition of output products of grinding and sizing aggregates change in a wide range. It leads to additional losses of the recovered grade. Duration of transient processes depends on how the controlled object’s current condition (its static and dynamic characteristics) corresponds to the controller’s adjustment in the ACS. It causes the necessity to readjust the controller’s parameters from time to time that is done in the adaptive ACS to the best advantage. The authors suggest an algorithm of noise immune correction of the controller’s parameters in the closed-loop automatic control system, which is based on preliminary identification of the controlled object’s static and dynamic characteristics in accordance with parameters of the transient process starting in the closed-loop ACS of the transient process. There are determined limits to its applicability at concentration plants. Objective. The research aims to develop a noise immune algorithm of adaptive control over objects with variable static and dynamic characteristics on the basis of the controlled parameter value and the rate of its changes on the initial stage of transient processes in the closed-loop ACS. Method. Current approaches and methods of improving ore concentration control are analyzed to substantiate the research topicality, goals and objectives. The adaptation algorithm for local ACS of ore concentration is synthesized and analyzed by methods of analytical design and computer simulation. Conclusions. The theory of forming specified parameters of transient processes in the closed-loop ACS by means of objects with variable static and dynamic characteristics on the basis of the controlled parameter value and the rate of its changes on the initial stage of these processes is developed in the present research. It allows synthesizing adaptive ACS, in which the error ratio in the transient process reaches zero in a minimum of time without changing its sign subject to disturbances and noises.

Characteristics of transient processes in a silver nanowire with optically dynamic shell

Fundamental theoretical understanding of the process of the time domain dynamics of the surface plasmon excitation in the structure, consisting of a metal nanowire coupled with the optically dynamic shell is presented. Details are described of the dynamics in the metal nanowire by means of meticulous and exact mathematical calculations that found from the semi-analytic solution into the Laplace transform domain and its accurate inversion into transient domain by virtue of residues assessment at singular points that correspond to the excited plasmons of the structure.This problem is a 2D model of nanolaser and has applications in the most growing areas of nanophotonics that require technologies, which can stimulate coherent plasmon fields in subwavelength domain.

GEFEST800 Software Complex for Performing Real-Time Neutron-Physical Calculations of the BN-800 Reactor in a Stationary Regime

The GEFEST800 software-hardware system was developed for performing real-time neutron-physical calculations of the BN-800 sodium-cooled fast reactor, viz. calculations of the effective breeding ratio, maximum reactivity excess, effi ciency of single and groups of control rods, total, specifi c, and linear density of power release in fuel assemblies, coeffi cients of nonuniformity of energy release in fuel assemblies and the reactor, damaging dose of irradiation of fuel assemblies, fuel burnup, reactivity coeffi cients (temperature, power, density) and void effect of reactivity, effective delayed-neutron fraction, characteristics of transient processes for normal operating regimes, residual energy release, activity of spent fuel assemblies, and others. The software-hardware system provides for calculations of normal operating regimes (stationary and nonstationary regimes at the lowest controllable power level and at power while controlling transient processes with rods, fuel burnup). The software-hardware system for computational tracking of BN-800 reactor operation was developed to determine the neutron-physical and thermohydraulic characteristics of BN-800 and to automate the process of collecting, analyzing, storing, and furnishing information on all fuel assemblies in the core from the start to fi nish of the operation of the reactor facility. The GEFEST800 software-hardware system was developed for performing real-time neutron-physical calculations of the BN-800 sodium-cooled fast reactor, viz. the effective breeding ratio, maximum reactivity excess, effi ciency of single and groups of control rods, total, specifi c, and linear density of power release in fuel assemblies, coeffi cients of nonuniformity of energy release in fuel assemblies and the reactor, damaging dose of irradiation of fuel assemblies, fuel burnup, reactivity coeffi cients (temperature, power, density) and void effect of reactivity, effective delayed-neutron fraction, characteristics of transient processes for normal operating regimes, residual energy release, activity of spent fuel assemblies, and others. The software-hardware complex provides for calculations of normal operating regimes (stationary and nonstationary regimes at the lowest controllable power level and at power while controlling transient processes with control rods, fuel burnup). The present variant of the GEFEST800 system is an elaboration of its preceding versions for the BN-600 reactor [1]. The software-hardware system has a modular structure. The primary modules are modules for preparing the neutron 1 Institute of Problems in the Safe Development of Nuclear Energy, Russian Academy of Sciences (IBRAE RAN), Moscow, Russia. 2 State Science Center of the Russian Federation – Leipunskii Institute for Physics and Power Engineering (GNTs RF – FEI), Obninsk, Russia. 3 All-Russia Research Institute for Operation of Nuclear Power Plants (VNIIAES), Moscow, Russia.

Onset of the Portevin-Le Chatelier Effect: Role of Synchronization of Dislocations

The problem of the onset of the Portevin-Le Chatelier (PLC) effect is revised by combining a study of the kinetics of the flow stress evolution upon abrupt changes in the applied strain rate and acoustic emission (AE) accompanying plastic deformation of an AlMg alloy. The kinetic measurements allow evaluating the strain-rate sensitivity of the flow stress and the time characteristics of transient processes as functions of plastic strain. Using known criteria of plastic instability, domains of instability are constructed in the (strain, strain rate) plane. A particular accent is put on the strain-rate range corresponding to the so-called “inverse” behavior. The comparison of such maps with experimental data on the critical strain testifies to the insufficiency of these criteria for explaining the onset of the PLC effect. Moreover, the slow transient kinetics contradicts observations of the fast development of stress drops. The AE measurements bear witness that the stress serrations are associated with bursts in duration of acoustic events generated by the collective motion of dislocations. The possible role of synchronization of dislocation dynamics on the onset of plastic instability is discussed.

Parameterising hydrological models – Comparing optimisation and robust parameter estimation

In most conditions, calibration is a prerequisite for successfully applying conceptual and physically based rainfall–runoff models. The goal of this paper is to comparatively analyse the potential of both event-based automatic calibration (PEST) as described in Skahill and Doherty (2006) and robust parameter estimation (ROPE) as proposed by Bardossy and Singh (2008). The results of our modelling study in the Rietholzbach catchment (Switzerland) show that ROPE performs better in validation of small to medium sized events. This indicates that ROPE might be better suited to parameterise models when the modellers intention is focussed on a maximising the generalisation capacity of the model, e.g. for evaluating transient process characteristics. We base our study on the hydrological model WaSiM-ETH, using a combined ROPE and automatic parameter estimation approach to investigate optimal parameter sets. The PEST algorithm used in this study outperforms the ROPE application by a factor of roughly 100 in terms of time required for computation.

Influence of an oscillating circuit on the radiation of transient acoustic waves by an electroelastic cylinder

The problem of nonstationary wave radiation in an infinitely long thick-wall piezoelectric cylinder in fluid medium is considered. The influence of an oscillating circuit with lumped parameters on characteristics of transient process is taken into consideration. Problem formulation is executed within the forced electrostatic theory, acoustic approximations, and quasistatic theory for electric circuit. The solution method is based on the integral Laplace transform in time. This allows analytically reducing the problem to solving a system of Volterra integral equations with retarded arguments. The numerical results of calculations are presented and analyzed.

Investigation of Transient Processes in Nematic Liquid Crystal Cells with Semiconductor Substrate, Caused by the Electric Field Applied to Semiconductor

In the present work the results of detailed researches on characteristics of transient processes, appearing by application of DC field to semiconductor substrate of liquid crystal cell have been carried out. It is shown, that oscillations, caused by longitudinal DC field applied to the semiconductor differ from the oscillations, caused by the Freedericksz transitions. The dependences of character and number of these oscillations on the applied DC field value, the type and thickness of nematic liquid crystal are investigated. The probable mechanisms explaining the observable phenomena are discussed.

Spatial dependence of the dynamic optical transfer function of a transparent medium perturbed by an acoustic signal

Based on a spatially dependent (SD) dynamic optical transfer function (DOTF) of a medium perturbed by an acoustic signal, a dynamic theory has been developed of the acousto-optical interaction (AOI) of light beams in the field of an arbitrary acoustic signal under conditions of the diffraction distortion of its amplitude profile (DDAP). A system of integro-differential equations is derived for angular and frequency DOTF spectra of coupled waves in the AOI region. An analytical DOTF model has been constructed for a weak acousto-optical coupling. The characteristics of transient processes (TPs) in the diffracted-beam field have been investigated for the spatially dependent DOTF. It is demonstrated that in most practical situations this dependence is manifested rather strongly; however, it does not always affect the TP. Thus, when the light and acoustic beam apertures exceed some characteristic values d* and L*, related to the acoustic frequency and speed and the AOI geometry, the effect of the SD DOTF on the transient process can be neglected. Otherwise, the DDAP leads to the asymmetry of the dynamic dependences of the field amplitude of the off-axis angular-spectrum components of the diffracted beam. The parameters d* and L* have been calculated for the AOI of several types in lithium niobate and paratellurite crystals. The TP characteristics are illustrated by plots calculated for the DDAP in the case of the AOI in paratellurite.

The engineering method of superconducting rectifiers computation

The developed engineering method of superconducting rectifiers (SCR) for magnet systems (MS) computation is based on analytical mode of linearized converter circuits investigation. The method makes it possible to determine actual and integral characteristics of transient processes at any time, commutation mode, control algorithms, under rectangular and sinusoidal forms of supply voltage, constant switch resistance and leakage current, etc. during MS pumping. Computation of rectifier elements main parameters is possible at required efficiency and some other parameters of pumping process. The method is realized in software package based on SuperCalc spreadsheet processor which makes it easy available.

Transient processes in canals with pumping stations

Changes in the operating regimes of pumping stations substantially affect dynamic processes in the canals of irrigation systems and lead to intense fluctuations of the levels and discharges. The experimental characteristics of transient processes in the pools of canals obtained correspond to the results of numerical calculations on a computer and obey mathematical modeling laws.

Investigation of transient stimulated emission from optically coupled lasers

A theoretical and experimental investigation was made of transient switching of stimulated emission between bistable states in optically coupled lasers. A computer calculation of the transient process characteristics is reported. The experimental results give the frequency of switching which is of the order of 1 GHz. A further increase in the switching frequency (reduction in the response time) can be achieved by reducing the laser dimensions.

Some characteristics of transient processes in encapsulated units

Transient processes in encapsulated units are characterized by a number of distinctive properties in comparison with axial-flow turbines in vertical units with cylindrical guide apparatus, namely: 1. In the case of load drops the most significant characteristics are: rapid rundown of the unit: increase in discharge at the start of the transient process and, as a consequence, a negative water hammer: major role of the virtual mass of the water: unique character of the relation nmax(Ndr), when the maximum rundown can correspond to a partial load drop: the magnitude of the positive axial forces throughout the transient does not exceed their initial values; the maximum negative axial forces occurring in the braking zone can exceed in absolute value by severalfold the value of Pax corresponding to the rated output, especially in those cases when small opeings of the guide apparatus are combined with a high (0.6–0.8)no unit rotational speed. 2. During stopping the axial forces directed toward the lower pool can be greater than in the rated steady regime; the negative force can exceed the maximum values during drops. 3. Stopping of the unit with deceleration from full speed produces large negative forces, but they are not determining when selecting the design loads. 4. During starting comparatively small axial forces are observed, and the starts, as a consequence of the lightness of the unit, are accompanied by small starting discharges and starting moments. 5. By changing the regulating conditions it is practically always possible to operate the unit in a manner whereby a safe regime is provided from the standpoint of flow discontinuity in the turbine section and the axial loads in both directions do not exceed the prescribed values.