Temat: transients - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Effect of Hydraulic Characteristics on Fluid Transients Analysis under Different Types of Control Valves
Autorzy:: Al-Zaidi, Basim M.
Ismaeel, Abaas J.
Tematy:: hydraulic characteristics
fluid transients
valve; Pokaż więcej
Data publikacji:: 2022
Powiązania:: https://bibliotekanauki.pl/articles/2202314.pdf Link otwiera się w nowym oknie
Źródło:: Journal of Ecological Engineering; 2022, 23, 12; 111--123
2299-8993
Pojawia się w:: Journal of Ecological Engineering
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.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 2.

Tytuł:: The modeling of centrifugal pump transients
Autorzy:: Szymczyk, J.
Karaśkiewicz, K.
Tematy:: rotodynamic pumps
complete pump characteristics
transients; Pokaż więcej
Data publikacji:: 2015
Powiązania:: https://bibliotekanauki.pl/articles/175255.pdf Link otwiera się w nowym oknie
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
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.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 3.

Tytuł:: Output characteristics of step-down (Buck) power converter
Autorzy:: Janke, W.
Bączek, M.
Walczak, M.
Tematy:: DC-DC converters
output characteristics
load transients; Pokaż więcej
Data publikacji:: 2012
Powiązania:: https://bibliotekanauki.pl/articles/201669.pdf Link otwiera się w nowym oknie
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
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.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 4.

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.
Tematy:: control system
electromagnetic transients
galvanic separation
plasma focus; Pokaż więcej
Data publikacji:: 2001
Powiązania:: https://bibliotekanauki.pl/articles/147621.pdf Link otwiera się w nowym oknie
Źródło:: Nukleonika; 2001, 46, suppl. 1; 89-91
0029-5922
1508-5791
Pojawia się w:: Nukleonika
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.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 5.

Tytuł:: Comparison of transformer modeling on riser pole arresters behavior during switching transients
Autorzy:: Abbaszadeh, A.
Abedi, M.
Doustmohammadi, A.
Tematy:: arresters
ATP software
ferroresonance
transformer
power system transients; Pokaż więcej
Data publikacji:: 2017
Powiązania:: https://bibliotekanauki.pl/articles/140474.pdf Link otwiera się w nowym oknie
Źródło:: Archives of Electrical Engineering; 2017, 66, 4; 717-730
1427-4221
2300-2506
Pojawia się w:: Archives of Electrical Engineering
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.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 6.

Tytuł:: Improved method for simulating transients of turbulent pipe flow
Autorzy:: Zarzycki, Z.
Kudźma, S.
Urbanowicz, K.
Tematy:: unsteady pipe flow
transients
waterhammer
efficient numerical simulation; Pokaż więcej
Data publikacji:: 2011
Powiązania:: https://bibliotekanauki.pl/articles/280935.pdf Link otwiera się w nowym oknie
Źródło:: Journal of Theoretical and Applied Mechanics; 2011, 49, 1; 135-158
1429-2955
Pojawia się w:: Journal of Theoretical and Applied Mechanics
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.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 7.

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
Tematy:: glioma C6
actin cytoskeleton
RhoA
ROCK
calcium transients; Pokaż więcej
Data publikacji:: 2006
Powiązania:: https://bibliotekanauki.pl/articles/1041182.pdf Link otwiera się w nowym oknie
Źródło:: Acta Biochimica Polonica; 2006, 53, 4; 825-831
0001-527X
Pojawia się w:: Acta Biochimica Polonica
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.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 8.

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.
Tematy:: arc modelling
overvoltages studies
EMTP-ATP program
transients analysis; Pokaż więcej
Data publikacji:: 2015
Powiązania:: https://bibliotekanauki.pl/articles/140943.pdf Link otwiera się w nowym oknie
Źródło:: Archives of Electrical Engineering; 2015, 64, 3; 441-458
1427-4221
2300-2506
Pojawia się w:: Archives of Electrical Engineering
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.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 9.

Tytuł:: Investigation on ferroresonance due to power transformer energization in high voltage 400 kV transmission grid
Autorzy:: Polewaczyk, Mateusz
Robak, Sylwester
Szewczyk, Marcin
Tematy:: ferroresonance
high voltage
Poincaré map
power system transients
PSCAD; Pokaż więcej
Data publikacji:: 2019
Powiązania:: https://bibliotekanauki.pl/articles/141509.pdf Link otwiera się w nowym oknie
Źródło:: Archives of Electrical Engineering; 2019, 68, 4; 771-786
1427-4221
2300-2506
Pojawia się w:: Archives of Electrical Engineering
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.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Skocz do pozycji: 10.

Tytuł:: Modeling transients in MV resonantly grounded industrial grid during single line to ground faults
Autorzy:: Warecki, Jurij
Gajdzica, Michał
Tematy:: electrical grid
grounding methods
transients overvoltage
transient intermittent faults; Pokaż więcej
Data publikacji:: 2019
Powiązania:: https://bibliotekanauki.pl/articles/377060.pdf Link otwiera się w nowym oknie
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
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.
Dostawca treści:: Biblioteka Nauki

Artykuł

na półce

Informacja

Wyszukujesz frazę "transients" wg kryterium: Temat