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Статті в журналах з теми "Phase comparison relay"
1
Taher, Menna, Mohamed Abaza, Mostafa Fedawy, and Moustafa Aly. "Relay Selection Schemes for FSO Communications over Turbulent Channels." Applied Sciences 9, no. 7 (March 27, 2019): 1281. http://dx.doi.org/10.3390/app9071281.
Повний текст джерелаАнотація:
Free Space Optics (FSO) Communication has attracted the attention of the researchers in the last decade due to its high data rate, security, and low cost. Relay-assisted techniques are used to divide the distance to shorter hops in order to mitigate the effects of turbulence, weather attenuation, pointing error, and geometric loss. Choosing an active relay per time slot has been proven to enhance the performance of the system and decrease the loading effect on the system when compared to all active relays. This paper investigates the best relay that can be selected according to the source to relay (S-R) channel coefficient, relay to destination (R-D) channel coefficient, and source to destination (S-D) channel coefficient. A comprehensive comparison is applied to the three following cases: (a) Broadcast phase from source to relay to select the best (Proactive-Relay); (b) Broadcast phase from relay to destination after broadcasting to all relays then select (Reactive-relays); and, (c) Direct link from source-to-best relay-to-destination to conclude which method is better for different scenarios, such as turbulence regime, number of relays, different pointing error effect, and severity of S-R as compared to R-D and vice versa. The selection methods regard to four aspects: (1) Number of relays (two or three relays); (2) Distance between Source-Relay and Relay-Destination (D = 400–600 m, 500–500 m, and 600–400 m); (3) The different turbulence of Log-normal channel and Gamma-Gamma channel (with a refractive index coefficient( C n 2 = 0.5 × 10−14, 2 × 10−14 and 5 × 10−14)); and finally, (4) Beam waist ω z (pointing error).
2
Zubić, Siniša J., and Milenko B. Djurić. "A distance relay algorithm based on the phase comparison principle." Electric Power Systems Research 92 (November 2012): 20–28. http://dx.doi.org/10.1016/j.epsr.2012.05.017.
Повний текст джерела
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González-Cueto, José Antonio, Zaid García Sánchez, Gustavo Crespo Sánchez, Hernan Hernandez, Jorge Iván Silva Ortega, and Vicente Leonel Martínez Díaz. "A mho type phase comparator relay guideline using phase comparison technique for a power system." International Journal of Electrical and Computer Engineering (IJECE) 11, no. 2 (April 1, 2021): 929. http://dx.doi.org/10.11591/ijece.v11i2.pp929-944.
Повний текст джерелаАнотація:
This paper presents a mho distance relay simulation based on the phase comparison technique using a typical electrical power systems analysis software for two cases: when the operation state is close to the static voltage limit and during a dynamic perturbation in the system. The paper evaluates the impedance variations caused by complex voltage values, the mho polarization, and the comparator operating region into the complex plane. In addition, the paper found the information for the dynamic perturbations from the outputs considering a mid-term stability program. The simulation of the mho-phase comparator in the static voltage proximity limit detects unit distance elements with impedance measured close to reach the threshold in the steady-state. Dynamic mho simulations in the complex plane are successfully tested by plotting time phase difference curves on the comparator input signals. Relay programmers can use these curves to analyze other phase comparators applications and the corresponding models in the complex plane.
4
Qiu, Xiao, Blanca De la Fuente, Alberto Lorenzo, and Santiago Veiga. "Comparison of Starts and Turns between Individual and Relay Swimming Races." International Journal of Environmental Research and Public Health 18, no. 9 (April 29, 2021): 4740. http://dx.doi.org/10.3390/ijerph18094740.
Повний текст джерелаАнотація:
The present study investigated swimmers’ performances on the starting and turning segments between individual and relay races. A total number of 72 race performances of the same swimmers in both relay 4 × 100 m finals (freestyle, medley, and mixed freestyle) and individual 100 m finals or semi-finals (butterfly, breaststroke, and freestyle) from the LEN European Swimming Championships were compared with repeated measures MANOVA. Swimmers performed 5–7% faster starts in the relay than in the corresponding individual events, despite no differences in the flight phase and a lower performance (shorter distances and slower velocities) on the underwater start section. The 15 m turn times were slower in the butterfly relay races although no specific differences in the underwater parameters were observed. These results suggest that specific training of the starting and turning segments should be performed under relay conditions to optimise pacing and performance in the underwater sections.
5
Zhu, Yifan, Tao Zheng, Minghao Wang, Hongcheng Zhao, and Xingguo Wang. "An Improved Directional Relay Adapted to a Distribution Network with IIG Integration." Energies 12, no. 17 (August 30, 2019): 3345. http://dx.doi.org/10.3390/en12173345.
Повний текст джерелаАнотація:
The integration of distributed generation (DG) into a distribution network changes the network’s topology. Three-stage current protection for a radial distribution network cannot meet the requirements of relay protection for a distribution network with DG. A directional relay that is based on the positive sequence fault component (PSFC) can effectively identify faults in the positive and negative directions and can be used to solve the adaptability problem with three-stage current protection in a multi-source distribution network. However, DG and the traditional generators have different fault characteristics and are affected by different control strategies, which may lower the sensitivity of a directional relay based on the PSFC or even cause mal-operation. Focusing on this problem, this paper proposes an improved directional relay that is adapted to a distribution network with inverter-interfaced generation (IIG) integration. The improved scheme divides the operation zone of the directional relay based on the PSFC into sensitive and insensitive areas. If the result of a phase comparison is located in the insensitive area, further identification is needed according to a comparison of the current amplitudes. Simulation experiments are carried out based on PSCAD/EMTDC, and their results verify the correctness of the proposed scheme.
6
Tseng, Kuo-Hsiung, Ching-Lin Huang, and Wei-Zhe Li. "Global Positioning System Application in Current Phase Comparison of Differential Protection Relay of Power Transmission Line." Electric Power Components and Systems 39, no. 15 (October 28, 2011): 1621–31. http://dx.doi.org/10.1080/15325008.2011.608768.
Повний текст джерела
7
Mohammed, Ali Abdulwahhab, Li Yu, Manar Al-Kali, and Desheng Wang. "Analysis of Amplify-and-Forward Cooperative Networks with Nakagami-m fading Channels For MRC Diversity Combining." TELKOMNIKA Indonesian Journal of Electrical Engineering 16, no. 3 (December 1, 2015): 546. http://dx.doi.org/10.11591/tijee.v16i3.1646.
Повний текст джерелаАнотація:
In this paper we study the effect of diversity combining for Nakagami -m fading Channels in the amplify-and-forward cooperative networks.We derive the cumulative density function (CDF), probability density function (PDF) and moment generating function (MGF) for the multiple relay amplify-and-forward network with single half duplex channel maximal ratio combiner (MRC). In this network we investigate the cases of MRC at the destination, as well derive the exact Symbol Error Rate (SER) of M-ary phase-shift keying (M-PSK), and quadrature amplitude modulation (M-QAM) in Nakagami -m fading environment. We present a comparison between M-PSK and M-QAM modulation schemes in some representative scenarios where an arbitrary number of cooperative relays is considered.
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Smith, Gregory D., Charles L. Cox, S. Murray Sherman, and John Rinzel. "Fourier Analysis of Sinusoidally Driven Thalamocortical Relay Neurons and a Minimal Integrate-and-Fire-or-Burst Model." Journal of Neurophysiology 83, no. 1 (January 1, 2000): 588–610. http://dx.doi.org/10.1152/jn.2000.83.1.588.
Повний текст джерелаАнотація:
We performed intracellular recordings of relay neurons from the lateral geniculate nucleus of a cat thalamic slice preparation. We measured responses during both tonic and burst firing modes to sinusoidal current injection and performed Fourier analysis on these responses. For comparison, we constructed a minimal “integrate-and-fire-or-burst” (IFB) neuron model that reproduces salient features of the relay cell responses. The IFB model is constrained to quantitatively fit our Fourier analysis of experimental relay neuron responses, including: the temporal tuning of the response in both tonic and burst modes, including a finding of low-pass and sometimes broadband behavior of tonic firing and band-pass characteristics during bursting, and the generally greater linearity of tonic compared with burst responses at low frequencies. In tonic mode, both experimental and theoretical responses display a frequency-dependent transition from massively superharmonic spiking to phase-locked superharmonic spiking near 3 Hz, followed by phase-locked subharmonic spiking at higher frequencies. Subharmonic and superharmonic burst responses also were observed experimentally. Characterizing the response properties of the “tuned” IFB model leads to insights regarding the observed stimulus dependence of burst versus tonic response mode in relay neurons. Furthermore the simplicity of the IFB model makes it a candidate for large scale network simulations of thalamic functioning.
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Feofilov, S. V., and A. V. Kozyr. "Stability of Periodic Motions and Synthesis of Relay Sampled Data Control Systems." Mekhatronika, Avtomatizatsiya, Upravlenie 20, no. 11 (November 7, 2019): 655–62. http://dx.doi.org/10.17587/mau.20.655-662.
Повний текст джерелаАнотація:
This article is devoted to research and design of relay systems with control of data sampling. It is shown that the time sample has a significant effect on the parameters of periodic oscillations. We propose an exact method for analyzing periodic modes in digital self-oscillatory control systems with a two-position relay element and a linear piecewise-linear part is proposed. The proposed approach extends the phase hodograph method to the class of systems operating in discrete time. Two approaches have been developed to assess the stability of periodic motions in such systems. In the first approach, a discrete representation of a plant is considered and areas of stability are defined for each possible limit cycle. The sampling of the control system causes a delay in the switching of the relay in a batch mode in comparison with the continuous case. The second approach assumes the replacement of a discrete system by an equivalent continuous system with a time delay. Further, the asymptotic orbital stability of self-oscillations in a relay control system (RCS) with a delay is estimated. We consider the linearization of relay systems with digital control of the input signal. It is also shown that when linearizing a relay element in a digital RCS using a useful signal, the relay transfer ratio will belong to a certain range of values. Synthesis of corrective devices for relay control systems with regard to digital implementation has been reviewed. At the stage of optimization of parameters of the relay control system, the sample is taken into account. The model example demonstrates an advantage in the synthesis of digital technologies. It is shown that when optimizing the controller parameters with regard to time discretization, it was possible to provide the desired frequency of self-oscillations, which ensures the best accuracy of the tracking mode.
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Sofwan, A., A. Multi, R. Soleman, Sugianto, and A. Kusuma Septian. "Leak Current Monitoring System On The Ground Cables Medium Voltage Transformer 150/20 kV." MATEC Web of Conferences 218 (2018): 01008. http://dx.doi.org/10.1051/matecconf/201821801008.
Повний текст джерелаАнотація:
On January, 2017 there had been fault trip at PMT 150/20 kV transformer in Jatirangon substation. For fault detection, that rele differential phase T and REF 20 kV have worked to detect this fault. The resulted impact of this fault is Power outage in feeder a 1350 A, 35 MW and 5 Mvar. The cause of this fault is the occurrence of breakdown on ground cables 20kV T-phase-core 1. This results in a short circuit to the ground so that the differential protection relay and REF 20kV work because the relay detects a fault in the ptotection zone. The result of this research is the design of an early detection monitoring tool. This tool is used to determine the amount of leakage current on the ground cable in order to minimize the occurrence of interference that causes the occurrence of electrical power outage. The result of the leakage current monitor on the ground phase cable T obtained a current of 0.6A with temperature 35 °C. With thermal failure calculation method for leakage current obtained result of 0,56180A with temperature 35 °C. Comparison of the calculation with the measurement of leakage current on the ground cable T phase is obtained at 6.36%.
Дисертації з теми "Phase comparison relay"
1
Ніценко, Володимир Вікторович. "Підвищення показників ефективності функціонування релейного захисту збірних шин розподільчих установок". Thesis, Запорізький національний технічний університет, 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/34557.
Повний текст джерелаАнотація:
Дисертація на здобуття наукового ступеня кандидата технічних наук (доктора філософії) зі спеціальності 05.14.02 – Електричні станції, мережі і системи. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2018.
Дисертація присвячена розв'язанню актуальної науково-прикладної задачі у галузі релейного захисту елементів електроенергетичних систем, що полягає у підвищенні ефективності дії релейного захисту збірних шин розподільчих установок. У роботі вдосконалено метод диференційно-фазного захисту шин, згідно з яким алгоритм порівняння фаз струмів застосовано у якості єдиного засобу забезпечення абсолютно селективної дії захисту в аварійних режимах, та запроваджено групу неконфігурованих параметричних уставок захисту, що сприяє зниженню ймовірності його неселективної дії через допущені персоналом помилки, а також, за рахунок оптимізації умов пуску та спрацювання захисту, підвищується їх успішність за внутрішніх коротких замикань, що дозволяє відмовитись від застосування окремого високочутливого органу захисту. Для поліпшення експлуатаційних характеристик та усунення режимних обмежень застосування пристроїв релейного захисту шин вдосконалено метод компенсації кутових похибок насичених трансформаторів струму у диференційно-фазному захисті шин в частині забезпечення подовження логічних імпульсів напруги, сформованих із напівхвиль спотворених струмів. Обрано робочі уставки параметрів налаштування диференційно-фазного захисту шин, а саме кута блокування ±φбл=900 та рівня формування імпульсів ±ір=(40-50)%·Іамп, за яких забезпечуватиметься його надійна та селективна дія в аварійних режимах. Проведено математичне і імітаційне моделювання поведінки диференційно-фазного захисту шин та лабораторні досліди його макетного зразку, що дозволило підтвердити адекватність розробленої моделі захисту, ефективність її алгоритмів та правильність обраних робочих уставок. Виконано аналіз техніко-економічних показників застосування диференційно-фазного захисту шин, на підставі якого визначені його переваги у порівнянні з пристроями диференційного струмового захисту шин та оцінені показники економічної ефективності його впровадження та експлуатації.Dissertation for a candidate degree (PhD) in Engineering Sciences of the speciality 05.14.02 – Electric power stations, networks and systems. – National technical university "Kharkiv polytechnic institute", Kharkiv, 2018. The dissertation is devoted to the solution of the actual scientific and practical problem in the field of relay protection of electric power systems elements, which is to increase the efficiency of relay busbar protection of switchgears. In this work, the method of phasedifferential busbar protection has been improved, according to which the currents phases comparison algorithm is applied as the sole means of providing absolutely selective protection in emergency conditions, and a group of non-configured parametric settings is introduced that reduces the probability of its non-selective operation through mistakes made by the personnel, as well as due to optimization start and trip conditions of protection operation, its performance increases at internal faults, which allows to refuse the application a high-sensitive protection relay. In order to improve the performance and eliminate the regime limitation of the use of relay protection devices, the method of compensating angular errors of saturated current transformers in the phase-differential busbar protection in the part of ensuring the extension of logic voltage impulses formed from half-waves of distorted currents is improved. The working parameters of the phase-differential busbar protection have been selected, namely the blocking angle is 900 and the impulse formation level is (40-50)%·Іamp, which will ensure its reliable and selective operation in emergency conditions. The mathematical and simulation modeling of the phasedifferential protection behavior and laboratory experiments of its model was carried out, which allowed to confirm the adequacy of the developed model of protection, the efficiency of its algorithms and the correctness of the selected working settings. There were completed analysis of technical and economic indicators of the phase-differential busbar protection using, on the basis of which were determined its advantages compared with the devices of differential busbar protection and approximate estimates of the economic efficiency of its implementation and operation.
2
Ніценко, Володимир Вікторович. "Підвищення показників ефективності функціонування релейного захисту збірних шин розподільчих установок". Thesis, НТУ "ХПІ", 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/34554.
Повний текст джерелаАнотація:
Дисертація на здобуття наукового ступеня кандидата технічних наук (доктора філософії) зі спеціальності 05.14.02 – Електричні станції, мережі і системи. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2018.
Дисертація присвячена розв'язанню актуальної науково-прикладної задачі у галузі релейного захисту елементів електроенергетичних систем, що полягає у підвищенні ефективності дії релейного захисту збірних шин розподільчих установок. У роботі вдосконалено метод диференційно-фазного захисту шин, згідно з яким алгоритм порівняння фаз струмів застосовано у якості єдиного засобу забезпечення абсолютно селективної дії захисту в аварійних режимах, та запроваджено групу неконфігурованих параметричних уставок захисту, що сприяє зниженню ймовірності його неселективної дії через допущені персоналом помилки, а також, за рахунок оптимізації умов пуску та спрацювання захисту, підвищується їх успішність за внутрішніх коротких замикань, що дозволяє відмовитись від застосування окремого високочутливого органу захисту. Для поліпшення експлуатаційних характеристик та усунення режимних обмежень застосування пристроїв релейного захисту шин вдосконалено метод компенсації кутових похибок насичених трансформаторів струму у диференційно-фазному захисті шин в частині забезпечення подовження логічних імпульсів напруги, сформованих із напівхвиль спотворених струмів. Обрано робочі уставки параметрів налаштування диференційно-фазного захисту шин, а саме кута блокування ±φбл=900 та рівня формування імпульсів ±ір=(40-50)%·Іамп, за яких забезпечуватиметься його надійна та селективна дія в аварійних режимах. Проведено математичне і імітаційне моделювання поведінки диференційно-фазного захисту шин та лабораторні досліди його макетного зразку, що дозволило підтвердити адекватність розробленої моделі захисту, ефективність її алгоритмів та правильність обраних робочих уставок. Виконано аналіз техніко-економічних показників застосування диференційно-фазного захисту шин, на підставі якого визначені його переваги у порівнянні з пристроями диференційного струмового захисту шин та оцінені показники економічної ефективності його впровадження та експлуатації.Dissertation for a candidate degree (PhD) in Engineering Sciences of the speciality 05.14.02 – Electric power stations, networks and systems. – National technical university "Kharkiv polytechnic institute", Kharkiv, 2018. The dissertation is devoted to the solution of the actual scientific and practical problem in the field of relay protection of electric power systems elements, which is to increase the efficiency of relay busbar protection of switchgears. In this work, the method of phasedifferential busbar protection has been improved, according to which the currents phases comparison algorithm is applied as the sole means of providing absolutely selective protection in emergency conditions, and a group of non-configured parametric settings is introduced that reduces the probability of its non-selective operation through mistakes made by the personnel, as well as due to optimization start and trip conditions of protection operation, its performance increases at internal faults, which allows to refuse the application a high-sensitive protection relay. In order to improve the performance and eliminate the regime limitation of the use of relay protection devices, the method of compensating angular errors of saturated current transformers in the phase-differential busbar protection in the part of ensuring the extension of logic voltage impulses formed from half-waves of distorted currents is improved. The working parameters of the phase-differential busbar protection have been selected, namely the blocking angle is 900 and the impulse formation level is (40-50)%·Іamp, which will ensure its reliable and selective operation in emergency conditions. The mathematical and simulation modeling of the phasedifferential protection behavior and laboratory experiments of its model was carried out, which allowed to confirm the adequacy of the developed model of protection, the efficiency of its algorithms and the correctness of the selected working settings. There were completed analysis of technical and economic indicators of the phase-differential busbar protection using, on the basis of which were determined its advantages compared with the devices of differential busbar protection and approximate estimates of the economic efficiency of its implementation and operation.
3
Huang, Ching-Lin, and 黃慶林. "Global Positioning System Application in Current Phase Comparison of Differential Protection Relay of Transmission and Distribution Line." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/3wz4vf.
Повний текст джерелаАнотація:
博士國立臺北科技大學
電機工程系博士班
100
This dissertation applied synchronous time of global positioning system (GPS) to generate reference voltage for current phase comparison of differential protection relay of power transmission line. The proposed method does not require conventional temporary reference voltage configuration, and can make current phase comparison test faster and safer. This dissertation simulated short circuit current before power transmission system is integrated into system, so that the differential protection relays at both ends have current value, and current transducer transforms three-phase current to voltage value. Furthermore, multifunction protection relay tester was used to increase AIM (Analog Input Measurement) and Trans Win for obtaining voltage waveform. The reference voltage using GPS synchronous time was compared with three-phase current waveform at both ends so as to obtain time difference. The current angle of various phases at both ends was calculated to compare whether the current angle difference between various phases at both ends was about 180º. The current phase comparison could be used to determine whether wiring is correct. The primary protection relay can synchronously operate when the line is integrated into the system. The power transmission line can be safer and more stable after integration with the system.
Тези доповідей конференцій з теми "Phase comparison relay"
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Dob, Brian, and Craig Palmer. "Communications assisted islanding detection: Contrasting direct transfer trip and phase comparison methods." In 2018 71st Annual Conference for Protective Relay Engineers (CPRE). IEEE, 2018. http://dx.doi.org/10.1109/cpre.2018.8349783.
Повний текст джерела
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Utsumi, Takuya, Tomomichi Nakatsuka, Hideyuki Takani, Hidenari Amoh, Fumio Kawano, and Phil Beaumont. "Faulted phase selection function based upon impedance comparison in a distance protection relay." In 2011 IEEE International Conference on Advanced Power System Automation and Protection (APAP). IEEE, 2011. http://dx.doi.org/10.1109/apap.2011.6180365.
Повний текст джерела
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Giˆrda, Gelu F., and Abdemusa Moosajee. "Optimization of Diesel Engine: Synchronous Alternator Group." In ASME/IEEE 2004 Joint Rail Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/rtd2004-66026.
Повний текст джерелаАнотація:
The paper describes the findings of an experiment that is a result of close collaboration among four companies. The paper discusses the experiment on one locomotive by using a microprocessor-based relay, Multiple Function Relay (MFR) SEL-701, for on-line measurement, control and optimization of a HEP (Head End Power) group. The HEP has a Diesel engine, 810 HP/908 HP, 1800 rpm, and a double wound three-phase self excited synchronous alternator, 625 kVA, 575 V. The HEP group is installed on the locomotive and supplies the electrical hotel power to the train’s coaches. The relay SEL-701 (Schweitzer Engineering Laboratories) measures the Diesel engine temperatures on 7 different points and the winding temperatures at 3 internal points, one per each phase. The SEL-701 monitors alternator output currents and voltages and controls one (or both) train lines when the Diesel engine’s hottest temperature equals the maximum admissible temperature. Amongst others the paper highlights the benefits derived by use of on-line measurements of the Diesel engine before and after relocation of a pre-existent engine shutdown temperature probe. In addition, the paper discusses the decrease in the numbers of Diesel engine shut downs due to the modified mode of protection and the increase in available electrical power supplied to the train lines together with the comparison of the HEP group efficiency before and after modification.
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Yang, Lijing, Milad Rakhsha, and Dan Negrut. "Comparison of Surface Tension Models in Smoothed Particles Hydrodynamics Method." In ASME 2019 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/detc2019-98124.
Повний текст джерелаАнотація:
Abstract We compare two surface tension models to solve two-phase fluid interaction problems in the context of the mesh-free Smoothed Particles Hydrodynamics (SPH) method. The Continuum Surface Force (CSF) model (later extended to Continuum Surface Stress, CSS), originally derived from grid-based numerical methods, requires an accurate estimation of the interface curvature to express the surface tension. Unlike CSF, the Inter-Particle Force (IPF) model is more robust in this regard as it draws on a molecular dynamics foundation by considering how the pairwise interaction forces between particles within a cutoff distance act in relation to producing the surface tension. Herein, we rely on second-order consistent gradient and Laplacian operators to improve the accuracy of SPH formulations as well as on a particle shifting technique to “disorder” particles from non-differentiable interface geometries. A 3D liquid droplet deformation test is used to compare CSF and IPF in terms of their pressure field and kinetic energy dissipation accuracy.
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Kreitzer, Paul J., Michael Hanchak, and Larry Byrd. "Horizontal Two Phase Flow Regime Identification: Comparison of Pressure Signature, Electrical Capacitance Tomography (ECT) and High Speed Visualization." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-89075.
Повний текст джерелаАнотація:
Understanding the behavior of transient two phase refrigerant flow is an important aspect of implementing vapor compression systems in future aerospace applications. Pressure drop and heat transfer coefficient are important parameters that guide the design process, and are influenced by flow regime. Published two phase flow models rely heavily on a priori knowledge of the current two phase flow conditions including flow regime. Additional complications arise when applying published correlations to a range of systems because each correlation is based on a specific set of experimental conditions, including working fluid, flow orientation, channel size, and channel shape. Non-intrusive measurement techniques provide important advantages while measuring the behavior of two phase flow systems. A two phase flow experimental test rig has been developed at the Air Force Research Laboratory, providing a closed loop refrigeration system capable of producing flow regimes from bubbly through annular flow. Two phase flow is produced by pumping subcooled R134a through a heat exchanger with 40 minichannels into an adiabatic transparent fused quartz observation channel with a hydraulic diameter of 7 mm. Refrigerant mass flux is varied from 100–400 kg/m2s with a heat flux from 0–15.5 W/cm2. Temperatures ranged from 18–25 °C and pressures between 550–750 kPa. The data from high speed pressure transducers were analyzed using standard signal processing techniques to identify the different flow regimes. Initial results indicate that different flow regimes can be identified from their pressure signature. In addition, real-time void fraction measurements were taken using Electrical Capacitance Tomography (ECT). This paper describes the process behind ECT systems used to measure two phase flow conditions. Comparisons with high speed video assess the accuracy of ECT measurements in identifying various two phase flow conditions. Results indicate variations between ECT and high speed images, however, enough information is provided to create flow pattern maps and regime identification for different superficial vapor and liquid velocities.
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Gauntt, Randall O., Kyle Ross, and Kenneth Wagner. "MELCOR 1.8.5 Simulation of TMI-2 Phase 2 With an Enhanced 2-Dimensional In-Vessel Natural Circulation Model." In 10th International Conference on Nuclear Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/icone10-22321.
Повний текст джерелаАнотація:
Phase 2 of the TMI-2 accident (core uncovery and melting) is revisited with the latest release of MELCOR (i.e., Version 1.8.5). An enhanced multi-ring multi-level hydro nodalization of the reactor core and upper plenum was developed to permit calculation of natural convection heat transfer between the core and upper internals. Uncertainties in boundary and initial conditions are investigated with particular attention given to the distribution of liquid in the RCS at the beginning of Phase 2 and to the histories of pressure and level in the steam generators. Special attention given to modeling the boiler sides of the once-through steam generators is presented. The modeling is designed to capture the rapid condensation of RCS vapor that would result from spraying cold auxiliary feedwater directly onto the upper portion of a voided steam generator tube bundle. Presentation of key Phase-2 accident signatures including fuel temperatures and hydrogen generation are presented. Comparisons are made between MELCOR calculations, TMI-2 data, and SCDAP/RELAP simulations. A largely improved MELCOR simulation of TMI-2 Phase 2 is obtained.
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Janczewski, Jacek, Ulf Nilsson, Torsten Strand, and Christian Troger. "Heat Load on the Walls of an Annular DLE Combustor Calculation and Comparison With Experiments." In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-454.
Повний текст джерелаАнотація:
The knowledge of the hot gas side heat load is a necessary prerequisite for the design of the advanced cooling scheme of a dry low-NOx combustor and the mechanical integrity (MIT) calculations of the combustor walls. The magnitude and the spatial distribution of the heat fluxes has to be known in the very early phase of the design, where there is no hardware available. The evaluation of a combustor wall design has to be based on known process data, thermodynamic and combustion parameters and has to rely on computational methods and experience. A stepwise computational approach is presented to reach this target utilising • 1D flow and Nusselt-Number correlations • 2-D boundary layer code • computational fluid dynamics (CFD) For the validation of the method atmospheric and pressurised single burner combustor tests were performed. The relative merits and pitfalls of the different methods are discussed in detail. Recommendations for their utilisation within the design process and for their further development are given.
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Sonawane, Mahesh, Rohit Vaidya, and Hunter Haeberle. "Structural Analysis of Rigid High-Pressure Risers for Seismic Loads." In Offshore Technology Conference. OTC, 2021. http://dx.doi.org/10.4043/31299-ms.
Повний текст джерелаАнотація:
Abstract Typically, the design of all offshore risers focuses on environmental loads i.e. wave loading, wind loads and currents. While these loads are ubiquitous in an offshore environment, accidental loading in the form earthquake induced seismic loads is an important criterion in the design of offshore structures. API RP 2A recommends site-specific studies as a basis for developing the ground motion specification of the design criteria, particularly for sites in areas of high seismicity (Zones 3–5). Seismic loads are low probability events in most cases and there isn't enough data in the initial pre-FEED / FEED phase of project to conduct seismic studies on the riser systems. Designers have to rely on past experience, code guidance, and assumptions for design data. In this paper through the means of two (2) case studies for a region prone with high seismic activities, we will demonstrate the challenges of designing rigid High-Pressure Riser Systems for seismic loads. A comparison will be provided for assumed loads based on code guidance and loads derived from preliminary seismic studies. In addition, comparisons will be provided for the final design loads achieved after the detailed platform design. The results will show the risks of relying solely on one source of data in the design process that can imperil the fabrication / procurement process with redesign due to unforeseen loads. Design optimization through proper centralization and other mitigation strategies will be presented for the benefits of future concrete based fixed platform projects.
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Thomas, Martin, Antoine Dauptain, Florent Duchaine, Laurent Gicquel, Charlie Koupper, and Franck Nicoud. "Comparison of Heterogeneous and Homogeneous Coolant Injection Models for Large Eddy Simulation of Multiperforated Liners Present in a Combustion Simulator." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64622.
Повний текст джерелаАнотація:
With the goal of increasing the thermodynamic efficiency of aircraft engines, the temperature in the combustion chamber has risen to the point where the gas temperature is above the melting point of materials used in the chamber and cooling systems are mandatory. Today, most of the existing lean burn combustors rely on multiperforated liners to keep hot gases away from the walls. However, resolving all holes of the combustor in the CFD design phase remains beyond currently available computational resources, so the effusion cooling system is often modeled by homogeneously injecting air on the whole surface of the liner, especially in the context of Large Eddy Simulation (LES) based CFD. This paper investigates a novel approach to simulate the effect of jets emitted from discrete holes on the flow inside a combustion chamber. In this new modeling approach, jet diameters are treated to be resolvable by the grid while conserving the correct mass and momentum flow rate. LES are performed on the combustion simulator of the engine representative FACTOR test rig at two different operating points and compared to measurement data as well as previous simulations obtained using a homogeneous air injection modeling on liners. The new approach shows globally similar results as the well validated homogeneous injection model and is applicable on realistic industrial geometries at a negligible level of additional cost (+0.3%).
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Hossain, Kamal, Michael Buck, Wolfgang Bernnat, and G. Lohnert. "TH3D: A Three-Dimensional Thermal Hydraulic Tool for Design and Safety Analysis of HTRs." In Fourth International Topical Meeting on High Temperature Reactor Technology. ASMEDC, 2008. http://dx.doi.org/10.1115/htr2008-58178.
Повний текст джерелаАнотація:
The institute of nuclear engineering and energy systems (IKE), University of Stuttgart, Germany has developed a new thermal hydraulic tool which can be used for three-dimensional thermal hydraulic analysis of pebble bed as well as block type HTRs. During nominal operation, the flow inside the gas-cooled High Temperature Reactor is essentially single-phase, compressible, and non-isothermal. So, at least one gas phase has to be considered beside the solid phase for thermal hydraulic analysis of HTRs. Each phase (e.g. solid, gas) is considered as a continuum which occupies only its respective fraction of the control volume. Thermal non-equilibrium is considered between phases and time dependent energy conservation equations for solid and gas phases are solved. Simplified momentum conservation equation for gas obtained from porous media approximation is solved along with the time dependent mass conservation equation. Provisions for simulating more than one gas component are available in this newly developed code TH3D which could be required for simulating some accident situations (e.g air / water ingress by pipes break). The interaction between phases is made by a set of constitutive equations which rely on semi-empirical correlations obtained from different experiments. Finite volume method with a staggered grid approach is used for spatial discretization and a fully implicit, time adaptive, multi step method is used for time-dependent discretization. A benchmark calculation which is oriented to the pebble type fuel reactor PBMR-400 and a 3D calculation were presented in HTR-2006 conference and will also be published in Nuclear Engineering and Design (NED) journal. In order to demonstrate the capabilities of TH3D for simulating all block type HTRs, a benchmark calculation which is proposed by IAEA CRP-3 and oriented to the Gas Turbine Modular Helium Reactor (GT-MHR) is performed. Calculations are performed for the steady state case (nominal operation) as well as for Loss of Forced Cooling (LOFC) with and without depressurization. The results obtained from TH3D are compared with the results obtained from several countries participated in this benchmark calculation program by using different code system. In this paper, results of this benchmark calculation and comparisons will be presented. A fuel model for pebble type fuel is implemented in TH3D where heterogeneity of heat production inside the fuel pebble is taken into account. The assumption of homogeneous heat production could be justified for steady state calculation or for slow transient but for fast transient calculation, the assumptions of homogeneous and heterogeneous heat production produce a huge difference for coupled thermal hydraulics and neutronics calculation. In order to show the capabilities of this newly developed code TH3D to couple with a neutronics system, it was coupled with a point kinetics model for a fast reactivity insertion case. In this case all control rods were withdrawn very quickly (with a velocity of 1 m/sec) to the end position. It was assumed that the scram signals were not activated when power or temperature was increased beyond a limiting value during this withdrawal process but the control rods system continued to be withdrawn up to the top position instead of getting down and the coolant flow was reduced by controlling the blowers. The neutronics feedback during this fast reactivity insertion case with homogeneous and heterogeneous fuel model will also be presented.