Analysis Of Transient Processes Research Articles

Метод расчета величины утечки сжатого воздуха из систем на основе анализа переходных процессов

Метод расчета величины утечки сжатого воздуха из систем на основе анализа переходных процессов

Transient processes in the parametric interaction of counter-propagating waves

We present a comparative analysis of transient processes in media with a negative refractive index for the parametric interaction of co- and counter-propagating waves. The transient time for the interaction of counter-propagating waves is shown to considerably exceed that for the interaction of co-propagating waves. In the case of counter-propagating waves, we present fitting results for the generated wave amplitude as a function of time and for the transient time vs. the amplitude of the pump wave and the length of the medium.

The Analysis of Electric Machines Electro-Mechanic Processes

The rapid development of modeling of various electromechanic energy transformers (power transformers, electric machines) over the past years created the necessity to develop the systematic method of quality and quantity model analysis. Typical analysis of model includes the following stages: the calculation of transient processes, the calculation of established processes, the evaluation of static stability, and the parametric sensitiveness defining. Nowadays, only the analysis of transient processes is performed continuously, i.e. in the state cognate with the physical nature of a process. Other stages are studied in discrete time. The variety of mathematical apparatus used on each stage complicates the analysis and requires significant expenses. In this article, the author describes the method of solving all four tasks on the basis of a unified mathematic apparatus - general theory of differential equations based on a unified algorithm. The completion of first three stages is illustrated on example of the induction machine, the mathematical model of which is arranged to the normal Cauchy form in order to avoid inversion of coefficient matrix on each integration step. By using the affine coordinate system the physical meaning of stator variables has been preserved and the rank of model equation system has been reduced. Stationary electromechanic process is defined by solv ing the twopoint Tperiodic boundary problem leaded do wn on period to Cauchy problem with initial conditions clarification by Newton iterations. The response matrix for the initial conditions, that is the basic element of the Newton formula, is defined from the analytical solving of homogeneous system of linear variation equations. The transient electro� mechanic process will result from the integration of state equations defining on time longer than period. The static stability of the process is defined by the multipliers of response matrix to the initial conditions. The matrix should be calculated for variables values of the last step in the integration process on period. The suggested method can be freely generalized for the analysis of complicated electromechanic schemes. Keywords: energy transformer, power transformer, electric machine, model analysis, unified mathematic apparatus, induction machine, electromagnetic proc ess, Tperiodic boundary problem, Cauchy problem.

Thermal response of transparent silver nanowire/PEDOT:PSS film heaters.

Thermal response behavior of transparent silver nanowire/PEDOT:PSS film heaters are intensively studied for manipulating heating temperature, response time, and power consumption. Influences of substrate heat capacity, heat transfer coefficient between air and heater, sheet resistance and dimension of Ag nanowire film, on the thermal response are investigated from thermodynamic analysis. Suggestion is given for practical applications that if other parameters are fixed, Ag nanowire coverage can be utilized as an effective parameter to adjust the thermal response. The heat transfer coefficient plays opposite roles on thermal response speed and achievable steady temperature. A value of ≈32 W m(-2) K(-1) is obtained from transient process analysis after correcting it by considering heater resistance variation during heating tests. Guidance of designing heaters with a given response time is provided by forming Ag nanowire film with a suitable sheet resistance on substrate of appropriate material and a certain thickness. Thermal response tests of designed Ag heaters are performed to show higher heating temperature, shorter response time, and lower power consumption (179 °C cm(2) W(-1)) than ITO/FTO heaters, as well as homogeneous temperature distribution and stability for repeated use. Potential applications of the Ag heaters in window defogging, sensing and thermochromism are manifested.

Using of shaping-filters in motion control system of high speed caterpillar machine

The article solves the problem of modeling of a nonlinear control system of motion of high-speed caterpillar machine using the algorithms of filtering. The main feature of the paper is the use of different shaping-filtering algorithms, which set the influence of driver and speed identifier. Special attention is paid to the analysis of transient processes overshoot and to the phase lag of machine response to the control action. The results of modeling are shown. Conclusions are made and recommendations for applying the idea are given.

Research on numerical simulation and protection of transient process in long-distance slurry transportation pipelines

The calculation of water-hammer pressure phenomenon of single-phase liquid is already more mature for a pipeline of uniform characteristics, but less research has addressed the calculation of slurry water hammer pressure in complex pipelines with slurry flows carrying solid particles. In this paper, based on the developments of slurry pipelines at home and abroad, the fundamental principle and method of numerical simulation of transient processes are presented, and several boundary conditions are given. Through the numerical simulation and analysis of transient processes of a practical engineering of long-distance slurry transportation pipeline system, effective protection measures and operating suggestions are presented. A model for calculating the water impact of solid and fluid phases is established based on a practical engineering of long-distance slurry pipeline transportation system. After performing a numerical simulation of the transient process, analyzing and comparing the results, effective protection measures and operating advice are recommended, which has guiding significance to the design and operating management of practical engineering of longdistance slurry pipeline transportation system.

Numerical analysis of transient processes in molten carbonate fuel cells via impedance perturbations

In this paper, the dynamic response of a molten carbonate fuel cell is studied by means of computational fluid dynamics. First, a rigorous three-dimensional, transient and non-isothermal model is developed through a comprehensive inclusion of various transport phenomena. Next, a sinusoidal impedance approach is used to examine the dynamic response of the unit cell to inlet perturbations at impedance frequencies of 1, 0.1, 0.01 and 0.001 Hz. This analysis is further used to determine the phase shifts and time scales of the major dynamic processes within the fuel cell. The load-following capability of the unit cell is studied by examining the dynamic responses of the average current density, electrochemical reactions rates, heat and mass transfer, mass fractions and temperature. The results show that the electrochemical reactions and the charge transport process adjust within a millisecond. The mass transport process shows a comparatively larger time scale that is about 1 s. The heat transport process is the slowest process in the cell and takes about an hour to reach its steady-state. The developed model along with the dynamic analysis results can be used to design process control strategies.

Application of an operational method of non-classical type for the analysis of transient processes in nonlinear dynamic systems of whole and fractional order

Application of an operational method of non-classical type for the analysis of transient processes in nonlinear dynamic systems of whole and fractional order

Nonlinear Analysis of Phase-Locked Loop

New method for the rigorous mathematical nonlinear analysis of PLL systems is suggested. This method allows to calculate the characteristics of phase detectors and carry out a rigorous mathematical analysis of transient process and stability of the system.

Software simulation and analysis of transient processes in engineering problems of induction-motor design

It is shown that the use of simulation programs for induction motors is revalent in engineering problems. The information about the in-house design of simulation software for the simulation of induction motors (including applied mathematical models) is presented.

On Convergence Rate of Second-Order Sliding Mode Control Algorithms

Transient processes in the systems controlled by second-order sliding mode (SOSM) algorithms are analyzed in the frequency domain. A methodology of the frequency-domain analysis of transient processes that feature a decaying oscillation of variable frequency is developed. A simple criterion of the existence of finite-time convergence is proposed. It is shown that the convergence rate in a system controlled by a relay or SOSM controller depends on the angle between the high-frequency asymptote of the Nyquist plot of the plant and the low-amplitude asymptote of the negative reciprocal of the describing function of the controller, which is called the phase deficit. Examples of analysis are given.

Transient phenomena and control of such phenomena in a generator with a delay

Results of the numerical analysis of transient processes in a mathematical model describing a generator with a time lag and delayed action are presented. Regular and chaotic oscillation modes under chaotically varying initial conditions are considered. The possibility of controlling a generator’s chaotic oscillations via a radio pulse is analyzed in the case when there are one or two attraction basins.

Simulation of dynamic speckle sequences and its application to the analysis of transient processes

Dynamic speckle has been used in recent years to analyse several transient processes that are produced in industrial and biological applications. We present here a numerical simulation to generate a temporal sequence of dynamic speckle patterns which is based on a model used for speckle formation by the superposition of waves from discrete scattering centres. It is demonstrated that the first and second statistics of the intensity of each speckle image, the time history of the speckle pattern, the temporal evolution of the correlation coefficient, and the power spectral density of the intensity generated by the proposed model reproduce quite well those obtained from experimentally recorded data. The process of a fast drying paint is presented as an example of the application of the proposed numerical model.

Transient processes and noise in a tomography system: an analytical case study

This paper presents an analysis and optimization of an ac-based electric capacitance tomography system. The existing system can capture image data up to 250 frames/s. However, even higher acquisition rates, say 2000 frames/s are desirable for some applications. To optimize the system design, a transient process analysis is performed for every analog stage to determine the settling time and an approach is suggested to minimize it. Noise analysis is also performed to ensure that the signal-to-noise ratio of the system does not degrade. In both cases, results are validated by simulation using PSpice and/or by experiment, showing that the settling time of the overall system could be reduced from 4.4 to 1 ms, offering a faster data acquisition rate of 1000 frames/s.

Nondestructive Testing of Mechanical Systems Based on Autoregression Models of the Response to a Sinusoidal Input Signal

A method for determining dynamic characteristics of mechanical systems based on the analysis of transient processes that represent responses to a sinusoidal input signal is considered. The essence of the method is in expressing the sought parameters through the coefficients of the autoregression model of a uniformly sampled signal. The obtained solutions are suggested for implementation in special-purpose devices or a microcomputer.

3526 稠密格子ロッドバンドルにおける限界出力相関式の改良と過渡限界出力試験の解析(S49-3 流動,原子炉用機器(2),S49 原子炉システムおよびその要素技術)

To develop the design correlation for the critical power in rod bundles is indispensable for R&D of Reduced-Moderation Water Reactor (RMWR) which adopts a triangular tight-lattice fuel rod configuration. In this research, critical power correlation developed for tight-lattice rod bundles is improved by using newly obtained 37-rod bundle data with 1.0mm gap between rods. Compared to the existing correlation, which based on the data obtained in 37-rod bundle data with 1.3mm gap, the improved one expands its adaptability to tighter rod bundles whose rod gap is 1mm, by revising the dependencies on mass velocity and equivalent heated diameter. The improved correlation is confirmed being able to give good critical power predictions to both its based datasets and Bettis Atomic Power Laboratory (BAPL) data. The standard deviation of ECPR (Experimental Critical Power Ratio) to JAERI 37-rod data and BAPL data are 7.3% and 8.4%, respectively. Moreover, the improved correlation is implemented into TRAC code, with which the analyses of transient processes postulated for the RMWR are carried out. For the postulated transients for the RMWR, it has been confirmed that BTs can be predicted within the accuracy of the implemented critical power correlation.

Analysis of transient processes in a radiophysical flow system

Transient processes in a third-order radiophysical flow system are studied and a map of the transient process duration versus initial conditions is constructed and analyzed. The results are compared to the arrangement of submanifolds of the stable and unstable cycles in the Poincaré section of the system studied.

RELAP5-3D code validation in the neutron-dynamic analysis of transient processes taking place in RBMK-1500 reactors

The paper presents an evaluation of RELAP5-3D code suitability to model-specific transients that take place during RBMK-1500 reactor operation, where the neutronic response of the core is important. Certain RELAP5-3D transient calculation results were benchmarked against calculation results obtained using the Russian complex neutronic-thermal-hydraulic code STEPAN/KOBRA, specially designed for RBMK reactor analysis. Comparison of the results obtained, using the RELAP5-3D and STEPAN/KOBRA codes, showed reasonable mutual agreement of the calculation results of both codes and their reasonable agreement with the real plant data.

Further developments in an ac-based capacitance tomography system

An ac-based electrical capacitance tomography (ECT) system has been developed at UMIST, with sinusoidal excitation and phase-sensitive demodulation (PSD). In this article the overall system design is briefly described and then discussed in detail are the key design features, needed to achieve a high signal-to-noise ratio and a high data acquisition rate, including transient process analysis of the first stage, design of an analog Butterworth low-pass filter and optimization of the data acquisition process. The experiments show that the ac-based system has signal variance 19 times better than the previous design, the charge/discharge ECT system, and that a data acquisition rate of 140 frames per second is achieved for a 12-electrode system.

Time-resolved spectral analysis of transient processes in Fabry-Perot interferometers

Parameters of a spectrochronograph that represents a Fabry-Perot interferometer combined with a spatial-time analyzer (a streak camera) are analyzed. Using numerical simulation, time scans of interferograms for bandwidth-limited and phase-modulated pulsed optical signals are obtained. The conditions are determined under which a Fabry-Perot interferometer represents a high-accuracy instrument for measuring the timeresolved spectral dynamics of short optical signals. In particular, an adequate representation of relatively smooth and monotone changes in amplitude and phase characteristics of an optical signal in a spectrochronograph requires that the mode lifetime in a Fabry-Perot interferometer be matched to the time scale of changes in the spectral structure of a pulse being studied. The character of distortions formed in the time-resolved spectral patterns in the case where these conditions are not fulfilled is qualitatively determined, and quantitative estimates of the distortions are presented. The results of the analysis and the numerical calculations show that a spectrochronogram obtained using a Fabry-Perot interferometer and a time analyzer (a streak camera) with parameters corresponding to the criteria formulated in the paper enable one to obtain information on the initial amplitude-phase pattern of a light pulse.