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Wyświetlanie 1-15 z 39
Tytuł:
Effect of Hydraulic Characteristics on Fluid Transients Analysis under Different Types of Control Valves
Autorzy:
Al-Zaidi, Basim M.
Ismaeel, Abaas J.
Powiązania:
https://bibliotekanauki.pl/articles/2202314.pdf
Data publikacji:
2022
Wydawca:
Polskie Towarzystwo Inżynierii Ekologicznej
Tematy:
hydraulic characteristics
fluid transients
valve
Opis:
In this study, several types of valves were used to study the impact of the valves types and closure characteristics on fluid transients. The valve closure curves, which are the variation of the effective valve opening as a function of percentage opening area, were derived for different selected valves. Six different types of valves were selected to study the effect of the valves types on fluid transient conditions. For simplification, a very simple pipeline system was assumed and presented in this study. The system is about two pipes connected in a series junction and they take the water from a constant-level reservoir at upstream and a valve at downstream. The duration of valve closure was taken as six seconds which plays an important role in the pressure development in the system. A method of characteristics is applied to compute the transient conditions under gradual closure of the valves. Valve data of various forms were compiled and reported as discharge and headloss coefficients as a function of valve opening. The effect of valve geometry and operation on the relative valve opening were compared. Discharge and headloss coefficients were also compared between valve types. The study concluded that transient conditions depend on the valve type. The comparison between the results of all valve types indicated that the changes in pressure and discharges depend on valve type where there is a difference in effective valve opening. It can be concluded that the valve with the highest value of valve effective opening has less effect on transient conditions, i.e., the faster changes of effective valve opening the larger the effect on transient conditions (discharge and the greater the magnitude of the pressure wave). This study would help to select the property valve in pipeline design.
Źródło:
Journal of Ecological Engineering; 2022, 23, 12; 111--123
2299-8993
Pojawia się w:
Journal of Ecological Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The modeling of centrifugal pump transients
Autorzy:
Szymczyk, J.
Karaśkiewicz, K.
Powiązania:
https://bibliotekanauki.pl/articles/175255.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
rotodynamic pumps
complete pump characteristics
transients
Opis:
Centrifugal pumps are part of larger hydraulic systems. These hydraulic machines can work not only in the pumping mode but in a number of other modes whose job description is possible using complete characteristics. Some of these modes, such as the turbine mode and the reversed turbine mode, may have practical significance. Knowledge of the transition from one steady state to another state allows to estimate instantaneous values such as, e.g., flow current and torque, which may be even a few times higher than nominal. The principal issues in these transients are amplitudes of parameters of these pumps and the time constants associated with the characteristics of the system.
Źródło:
Transactions of the Institute of Fluid-Flow Machinery; 2015, 130; 83-92
0079-3205
Pojawia się w:
Transactions of the Institute of Fluid-Flow Machinery
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Output characteristics of step-down (Buck) power converter
Autorzy:
Janke, W.
Bączek, M.
Walczak, M.
Powiązania:
https://bibliotekanauki.pl/articles/201669.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
DC-DC converters
output characteristics
load transients
Opis:
The output characteristics of switched-mode dc-dc buck power converter are discussed. The shape of output characteristics is especially important for converters used for supplying modern processors. An output impedance is usually used for description of output characteristics. Many efforts are described in the literature to obtain the satisfastory features of closed-loop output impedance. Another approach, presented in the paper, is based on the concept of the output voltage response corresponding to the load conductance change, and is expressed by hr transmittance. Simulations of output characteristics of the buck converter in frequency and in time-domain have been performed for the ideal case as well as for a more realistic situation, with the parasitic resistances of converter elements included. The measurement results differ substantially from characteristics calculated for an ideal converter and are in good consistency with simulations including parasitics.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2012, 60, 4; 751-755
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of transformer modeling on riser pole arresters behavior during switching transients
Autorzy:
Abbaszadeh, A.
Abedi, M.
Doustmohammadi, A.
Powiązania:
https://bibliotekanauki.pl/articles/140474.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
arresters
ATP software
ferroresonance
transformer
power system transients
Opis:
Arresters are widely used in power systems to protect other equipment against overvoltages. However, in some conditions, they can’t operate successfully. One of the disturbances leading to the failure of the riser pole arresters is the ferroresonance overvoltages. In this paper, at first the influence of different transformer simulation models of ATP software on the occurrence of ferroresonance is studied and then the effect of ferroresonance on the riser pole arrester has been scrutinized through the thermal and electrical performance of the arrester in an underground distribution system. The results show that the arrester temperature rises due to energy dissipation in a ferroresonance circumstance, which indeed may result into the explosion of the arrester. Also, applying different models of the transformer in the ATP software and comparing the results, it is shown that the available models do not show the same effect on the arrester.
Źródło:
Archives of Electrical Engineering; 2017, 66, 4; 717-730
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Improved method for simulating transients of turbulent pipe flow
Autorzy:
Zarzycki, Z.
Kudźma, S.
Urbanowicz, K.
Powiązania:
https://bibliotekanauki.pl/articles/280935.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
unsteady pipe flow
transients
waterhammer
efficient numerical simulation
Opis:
The paper presents the problem of modelling and simulation of transients during turbulent fluid flow in hydraulic pipes. The instantaneous wall shear stress on a pipe wall is presented in the form of integral convolution of a weighting function and local acceleration of the liquid. This weighting function depends on the dimensionless time and Reynolds number. Its original, very complicated mathematical structure is approximated to a simpler form which is useful for practical engineering calculations. The paper presents an efficient way to solve the integral convolution based on the method given by Trikha (1975) for laminar flow. An application of an improved method with the use of the Method of Characteristic for the case of unsteady flow (water hammer) is presented. This method is characterised by high efficiency compared to traditional numerical schemes.
Artykuł przedstawia zagadnienie modelowania i symulacji przebiegów przejściowych podczas turbulentnego przepływu cieczy w przewodach ciśnieniowych. Chwilowe naprężenie styczne na ściance przewodu przedstawiono w postaci całki splotowej z funkcji wagi i przyspieszenia cieczy. Funkcja wagi dla naprężenia stycznego na ściance przewodu zależy od czasu bezwymiarowego i liczby Reynoldsa. Ma ona zawiłą postać matematyczną, dlatego aproksymowano ją do prostszej postaci, przydatnej do praktycznych obliczeń inżynierskich. Przedstawiono efektywny sposób rozwiązania całki splotowej, opierając się na metodzie podanej przez Trikha (1975) dla przepływu laminarnego. Podano zastosowanie ulepszonej metody symulacji naprężenia stycznego do metody charakterystyk podczas uderzenia hydraulicznego. Charakteryzuje się ona dużą efektywnością w stosunku do metody tradycyjnej.
Źródło:
Journal of Theoretical and Applied Mechanics; 2011, 49, 1; 135-158
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Technical solutions for the control and command system of a Plasma Focus device
Autorzy:
Martin, D. I.
Zoita, V. I.
Cotruta, D. A.
Jianu, A. V.
Ighigeanu, D. I.
Bestea, V. I.
Powiązania:
https://bibliotekanauki.pl/articles/147621.pdf
Data publikacji:
2001
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
control system
electromagnetic transients
galvanic separation
plasma focus
Opis:
The paper presents the technical problems related to the electrical control and command system (ECC system) for the plasma focus installation IPF-4/5A having the following main parameters: 1 MA plasma current and 40 kJ energy stored at 20 kV charging voltage. The ECC system applies 23 interlocked logical commands, acquires and processes 28 logical states, acquires, processes and displays continuously the main slow-varying signals coming from IPF-4/5A subassemblies. All the plasma focus installation operational sequences are governed by strict hard and soft interlocking using in parallel two control and command systems: one based on PC-control methods and another based on classical control techniques.
Źródło:
Nukleonika; 2001, 46, suppl. 1; 89-91
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transient recovery voltage analysis for various current breaking mathematical models: shunt reactor and capacitor bank de-energization study
Autorzy:
Oramus, P.
Chmielewski, T.
Kuczek, T.
Piasecki, W.
Szewczyk, M.
Powiązania:
https://bibliotekanauki.pl/articles/140943.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
arc modelling
overvoltages studies
EMTP-ATP program
transients analysis
Opis:
Electric arc is a complex phenomenon occurring during the current interruption process in the power system. Therefore performing digital simulations is often necessary to analyse transient conditions in power system during switching operations. This paper deals with the electric arc modelling and its implementation in simulation software for transient analyses during switching conditions in power system. Cassie, Cassie-Mayr as well as Schwarz-Avdonin equations describing the behaviour of the electric arc during the current interruption process have been implemented in EMTP-ATP simulation software and presented in this paper. The models developed have been used for transient simulations to analyse impact of the particular model and its parameters on Transient Recovery Voltage in different switching scenarios: during shunt reactor switching-off as well as during capacitor bank current switching-off. The selected simulation cases represent typical practical scenarios for inductive and capacitive currents breaking, respectively.
Źródło:
Archives of Electrical Engineering; 2015, 64, 3; 441-458
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation on ferroresonance due to power transformer energization in high voltage 400 kV transmission grid
Autorzy:
Polewaczyk, Mateusz
Robak, Sylwester
Szewczyk, Marcin
Powiązania:
https://bibliotekanauki.pl/articles/141509.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
ferroresonance
high voltage
Poincaré map
power system transients
PSCAD
Opis:
This paper presents a study on ferroresonance occurring in a high voltage 400 kV transmission grid due to energization of power transformer under no-load conditions. The system scenarios analyzed in the present paper are considered as critical for development and modernization plans as currently announced by the national grid operator in Poland. The PSCAD simulation model was developed and applied for several study cases of a system with double-circuit arrangement of a transmission line. It is shown that the ferroresonant oscillations can be initiated by two-phase switching operation of a line circuit breaker. The impact of the double-circuit length on the ferroresonance mode and severity is demonstrated with the use of the Poincaré map analysis and Short Time Fourier Transform. It is demonstrated that the length of the transmission line that is mutually coupled in the double-circuit arrangement has a significant impact on the ferroresonance occurrence and on its mode. As the ferroresonance can pose severe threat to the power system components due to the severe overvoltage and overcurrent oscillations, the analysis presented in this paper demonstrates the necessity of the ferroresonance analyses for any re-designed transmission system.
Źródło:
Archives of Electrical Engineering; 2019, 68, 4; 771-786
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modeling transients in MV resonantly grounded industrial grid during single line to ground faults
Autorzy:
Warecki, Jurij
Gajdzica, Michał
Powiązania:
https://bibliotekanauki.pl/articles/377060.pdf
Data publikacji:
2019
Wydawca:
Politechnika Poznańska. Wydawnictwo Politechniki Poznańskiej
Tematy:
electrical grid
grounding methods
transients overvoltage
transient intermittent faults
Opis:
Medium voltage distribution power grids mostly operate with ungrounded neutral points of transformer. The philosophy about these power supply systems based on the assumption that the electrical grid is more reliable. However the practice of operation showed that currents of single phase or multiple faults to ground depend mostly on the earth capacitances of cables connected to power grid and configuration and structure in relation to the main substation buses. Moreover, this kind of arcing ground faults on the ungrounded system causes transient overvoltages several times than nominal value. In the consequence, it may be dangerous for the electrical devices connected to the power system. The article focuses on the transient impact the equipment insulation due to faults in the middle voltage industrial grid with adjustable speed drives. The examination results of transient voltages across the system was presented. The Matlab/ Simulink Software was used to modeling system behavior during intermittent faults.
Źródło:
Poznan University of Technology Academic Journals. Electrical Engineering; 2019, 98; 65-75
1897-0737
Pojawia się w:
Poznan University of Technology Academic Journals. Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Control of operability of Peltier modules in cooling systems based on the analysis of transient operating modes
Autorzy:
Kuzichkin, Oleg Rudolfovich
Konstantinov, Igor Sergeevich
Vasilyev, Gleb Sergeevich
Surzhik, Dmitry Igorevich
Powiązania:
https://bibliotekanauki.pl/articles/1845461.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
thermoelectric system
agriculture
complex
transients
peltier effect
identification algorithms
Opis:
The paper is devoted to the control of operability of Peltier modules based on the analysis of transient modes of their operation. Advantages of using low-power thermoelectric modules for the development of thermoelectric plants with adaptive control systems for the needs of the agricultural complex, which significantly reduce their cost characteristics, are shown. The problem of using the stationary mode of their operation, associated with the low efficiency of the modules, as well as the dynamic mode, associated with the presence of transient processes, is indicated. It is noted that overcoming this problem requires solution of the task of automation of reliability providing the well-known approaches to its solution are shown, for which the key advantages and disadvantages are given. An approach is proposed to complex control of the operability and quality of thermoelectric modules during their expluatation in three components of the physical process of thermoelectric conversion (Peltier thermoelectric effect, electrical and thermal transfer phenomena) by analyzing transients in the system based on identification algorithms. To justify it, the necessary equations and mathematical relations are given. Aprobating of the proposed approach was carried out experimentally by determining the time constants for operable and defective commercially available modules and showed its significant advantages over the standard verification procedure.
Źródło:
Archives of Thermodynamics; 2021, 42, 2; 31-42
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Rho-associated kinase inhibition on actin cytoskeleton structure and calcium response in glioma C6 cells
Autorzy:
Targos, Berenika
Pomorski, Paweł
Krzemiński, Patryk
Barańska, Jolanta
Rędowicz, Maria
Kłopocka, Wanda
Powiązania:
https://bibliotekanauki.pl/articles/1041182.pdf
Data publikacji:
2006
Wydawca:
Polskie Towarzystwo Biochemiczne
Tematy:
glioma C6
actin cytoskeleton
RhoA
ROCK
calcium transients
Opis:
The role of actin cytoskeleton functional state in glioma C6 cell morphology and calcium signaling was investigated through modification of myosin II activity by blocking Rho-associated kinase with the specific inhibitor Y-27632. Treatment of glioma C6 cells with ROCK inhibitor resulted in actin cytoskeleton reorganization and also in the changed shape and distribution of mitochondria. Changes in the distribution of ER, the main calcium store in glioma C6 cells, were not visible. The inhibition of myosin II activity influences the first phase of calcium signaling evoked by agonist, and both phases of thapsigargin-evoked calcium response. We suggest that the observed increase in Ca2+ release from intracellular stores induced by IP3 formation as well as inhibition of SERCA ATPase is at least in part related to severely affected mitochondria. Enhancement of capacitative calcium entry evoked by thapsigargin is probably associated with the reorganization of the acto-myosin II system. ATP-induced calcium response presents no changes in the second phase. We observed that ATP stimulation of Y-27632 pretreated cells leads to immediate morphological rearrangement of glioma C6 cells. It is a consequence of actin cytoskeleton reorganization: formation of stress fibers and relocation of phosphorylated myosin II to actin filaments. It seems that the agonist-evoked strong calcium signal may be sufficient for myosin II activation and the stress fiber organization. This is the first work showing the dependence between the functional state of the acto-myosin II system and calcium signaling stressing the reversible character of this relationship.
Źródło:
Acta Biochimica Polonica; 2006, 53, 4; 825-831
0001-527X
Pojawia się w:
Acta Biochimica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of Transients in a 4-Level Flying Capacitor Converter: Time Domain Approach. Part 2: Small Normalised Voltage Command
Autorzy:
Reznikov, Boris
Ruderman, Alex
Galanina, Valentina
Powiązania:
https://bibliotekanauki.pl/articles/1193863.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
4-level DC–DC converter
flying capacitor
natural balancing
transients
Opis:
A 4-level flying capacitor converter (FCC) operation is considered on a base of discrete state-space model. A transition matrix is obtained for a pulse width modulation (PWM) period for small normalised voltage command values [0, 1/3]. The transition matrix elements are expanded into power series by small parameters. The matrix eigenvalues are presented in the form of power series as well. Six separate transients are constructed for six possible initial FCC states on a PWM period. Inductor current and capacitors’ voltage transients are found for the voltage source power-up as the arithmetic average of the six separate transients. Finally, the discrete solutions are replaced by equivalent continuous ones. Simple and accurate formulas for inductor current and capacitors’ voltage transients demonstrate good agreement with simulation results.
Źródło:
Power Electronics and Drives; 2020, 5, 40; 41-57
2451-0262
2543-4292
Pojawia się w:
Power Electronics and Drives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of Transients in a 4-Level Flying Capacitor Converter: Time Domain Approach. Part 1: Large Normalised Voltage Command
Autorzy:
Reznikov, Boris
Ruderman, Alex
Galanina, Valentina
Powiązania:
https://bibliotekanauki.pl/articles/1193906.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
4-level DC-DC converter
flying capacitor
natural balancing
transients
Opis:
A 4-level flying capacitor converter (FCC) operation is considered on a base of discrete state-space model. A transition matrix is obtained for a pulse width modulation (PWM) period for large normalised voltage command values [1/3, 1). The transition matrix elements are expanded into power series by small parameters. The matrix eigenvalues are presented in the form of power series as well. Six separate transients are constructed for six possible initial FCC states on a PWM period. Inductor current and capacitors’ voltage transients are found for the voltage source power-up as the arithmetic average of the six separate transients. Finally, the discrete solutions are replaced by equivalent continuous ones. Simple and accurate formulas for inductor current and capacitors’ voltage transients demonstrate good agreement with simulation results.
Źródło:
Power Electronics and Drives; 2020, 5, 40; 27-40
2451-0262
2543-4292
Pojawia się w:
Power Electronics and Drives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vibration transients of reservoir-pipe-valve system caused by water hammer
Autorzy:
Miao, Yang
Jiang, Yuncheng
Qiu, Zaihui
Pan, Jun
Wang, Lu
Han, Zhenrong
Li, Kun
Zhang, Li
Zhang, Xiaolu
Powiązania:
https://bibliotekanauki.pl/articles/1839616.pdf
Data publikacji:
2020
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
reservoir-pipe-valve system (RPV system)
water hammer
vibration
transients
Opis:
A severe oscillation, accompanied with an abnormal “click” sound, of a fuel feeding pipe system during valve closing, when the feeding flowrate reaches a certain value, is observed experimentally. A fluctuation model in which stiffness and damping coefficients of the vibration system are time varying is proposed. Each coefficient is composed of two parts, one of which is constant and the other is time varying. Based on this model, simulation transients of the vibration displacement, velocity and pressure in the pipe are presented. Simulations of the pressure transients are compared with experimental data detected by pressure transducer, which shows that both have fluctuations in the transient process at a large flowrate.
Źródło:
Journal of Theoretical and Applied Mechanics; 2020, 58, 4; 1037-1048
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of the stator inductances of the expanded Park model and an approach on parameter identification using the evolution strategy
Autorzy:
Schmuelling, Ch.
Kreischer, Ch.
Gołebiowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/141147.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
evolution strategy
FEM
Park equations
Park theory
synchronous machines
transients
Opis:
Commonly, the Park model is used to calculate transients or steady-state operations of synchronous machines. The expanded Park theory derives the Park equations from the phase-domain model of the synchronous machine by the use of transformations. Thereby, several hypothesis are made, which are under investigation in this article in respect to the main inductances of two different types of synchronous machines. It is shown, that the derivation of the Park equations from the phase-domain model does not lead to constant inductances, as it is usually assumed for these equations. Nevertheless the Park model is the most common analytic model of synchronous machines. Therefore, in the second part of this article a method using the evolution strategy is shown to obtain the parameters of the Park model.
Źródło:
Archives of Electrical Engineering; 2016, 65, 3; 585-599
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
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