• Title/Summary/Keyword: Transient Conditions

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Study on the Recoil Operation of the Servomotor with PM Poles (PM형 제어용 Servo전동기의 Recoil동작에 관한 연구)

  • Se Hoon Chang
    • 전기의세계
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    • v.21 no.4
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    • pp.15-21
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    • 1972
  • For the conventional DC machine, the armature MMF is negligible compared with field MMF except when the machine is under heavy load or transient conditions. During the motor starting or reversal, the transient armature current and corresponding MMF effect the flux density of each pole in the machine magnetic circuit. However, the circuit flux density is restored to normal values by the field winding MMF after the transient armature current dies in an electromagnetic DC motor. Permanent magnet servomotor have no field windings about the circuit poles to restore circuit flux density through the demagnetized part of each pole after the transient armature MMF dies, and portions of the magnetic circuit stay permanently demagnetized. Thus the problem of stabilizing a magnet pole piece under the influence of the transient armature current need attentions. This work present the recoil operation of the servomotor with PM poles in conjunctions with the influence of the armature reaction effect. The development of an analytical and quantatative study is presented for predicting the regime of the recoil operation under this condition.

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TRANSIENT CHF PHENOMENA DUE TO EXPONENTIALLY INCREASING HEAT INPUTS

  • Park, Jong-Doc;Fukuda, Katsuya;Liu, Qiusheng
    • Nuclear Engineering and Technology
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    • v.41 no.9
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    • pp.1205-1214
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    • 2009
  • The critical heat flux (CHF) levels that occurred due to exponential heat inputs for varying periods to a 1.0-mm diameter horizontal cylinder immersed in various liquids were measured to develop an extended database on the effect of high subcoolings for quasi-steady-state and transient maximum heat fluxes. Two main mechanisms of CHF were found. One mechanism is due to the time lag of the hydrodynamic instability (HI) which starts at steady-state CHF upon fully developed nucleate boiling, and the other mechanism is due to the explosive process of heterogeneous spontaneous nucleation (HSN) which occurs at a certain HSN superheat in originally flooded cavities on the cylinder surface. Steady-state CHFs were divided into three regions for lower, intermediate and higher subcooling at pressures resulting from HI, transition and HSN, respectively. HSN consistently occurred in the transient boiling CHF conditions that correspond to a short period. It was also found that the transient boiling CHFs gradually increased, then rapidly decreased and finally increased again as the period became shorter.

Thermal Stress Analysis for Life Prediction of Power Plant Turbine Rotor (발전용 터빈 로우터의 수명예측을 위한 열응력 해석)

  • 임종순;허승진;이규봉;유영면
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.2
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    • pp.276-287
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    • 1990
  • In this paper research result of transient thermal stress analysis of power plant turbine rotors for life prediction under severs operating conditions is presented. Galerkin's recurrence scheme is used for numerical solution of discretized FEM equation of transient heat conduction equation. Boundary conditions for the equation and operating conditions are intensively investigated for accurate life prediction of turbine rotors in operation. A computer program for on-site application is developed and tested. Distribution of thermal stress in turbine rotors during various operating condition is analyzed with the program and it is found that the peak thermal stress appears during cold stage conditions at the first stage of high pressure rotors.

Simulation of reactivity-initiated accident transients on UO2-M5® fuel rods with ALCYONE V1.4 fuel performance code

  • Guenot-Delahaie, Isabelle;Sercombe, Jerome;Helfer, Thomas;Goldbronn, Patrick;Federici, Eric;Jolu, Thomas Le;Parrot, Aurore;Delafoy, Christine;Bernaudat, Christian
    • Nuclear Engineering and Technology
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    • v.50 no.2
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    • pp.268-279
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    • 2018
  • The ALCYONE multidimensional fuel performance code codeveloped by the CEA, EDF, and AREVA NP within the PLEIADES software environment models the behavior of fuel rods during irradiation in commercial pressurized water reactors (PWRs), power ramps in experimental reactors, or accidental conditions such as loss of coolant accidents or reactivity-initiated accidents (RIAs). As regards the latter case of transient in particular, ALCYONE is intended to predictively simulate the response of a fuel rod by taking account of mechanisms in a way that models the physics as closely as possible, encompassing all possible stages of the transient as well as various fuel/cladding material types and irradiation conditions of interest. On the way to complying with these objectives, ALCYONE development and validation shall include tests on $PWR-UO_2$ fuel rods with advanced claddings such as M5(R) under "low pressure-low temperature" or "high pressure-high temperature" water coolant conditions. This article first presents ALCYONE V1.4 RIA-related features and modeling. It especially focuses on recent developments dedicated on the one hand to nonsteady water heat and mass transport and on the other hand to the modeling of grain boundary cracking-induced fission gas release and swelling. This article then compares some simulations of RIA transients performed on $UO_2$-M5(R) fuel rods in flowing sodium or stagnant water coolant conditions to the relevant experimental results gained from tests performed in either the French CABRI or the Japanese NSRR nuclear transient reactor facilities. It shows in particular to what extent ALCYONE-starting from base irradiation conditions it itself computes-is currently able to handle both the first stage of the transient, namely the pellet-cladding mechanical interaction phase, and the second stage of the transient, should a boiling crisis occur. Areas of improvement are finally discussed with a view to simulating and analyzing further tests to be performed under prototypical PWR conditions within the CABRI International Program. M5(R) is a trademark or a registered trademark of AREVA NP in the USA or other countries.

Introduction to Systems Analysis Technique for a Liquid Rocket Engine (액체로켓엔진 시스템 해석 기술 소개)

  • Cho, Won Kook;Park, Soon Young;Kim, Chul Woong
    • Aerospace Engineering and Technology
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    • v.13 no.1
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    • pp.70-75
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    • 2014
  • Programs of energy balance, mode analysis and transient analysis for a liquid rocket engine have been introduced. The analysis methods have been verified through comparison between the present results, and the results of the other program and experimental data. An energy balance analysis is used for engine system design at the early development phase. A mode analysis is used for decision of engine operation conditions and test conditions, and studying deviation of an engine performance. A transient analysis can predict a propellant flow rate, thrust, impulse at transient phase. It is essential to establish a startup/shut down sequence. The analysis programs will be used to develop the engines of KSLV-II.

Transient loss analysis of non-insulation high temperature superconducting coil using the field-based data profiling method

  • Hoon Jung;Yoon Seok Chae;June Hee Han;Ji Hyung Kim;Seung Hoon Lee;Ho Chan Kim;Young Soo Yoon;Ho Min Kim
    • Progress in Superconductivity and Cryogenics
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    • v.25 no.3
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    • pp.38-42
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    • 2023
  • The evaluation of no-insulation (NI) high-temperature superconducting (HTS) typically uses the lumped equivalent circuit (LEC) model. Constant parameters in the NI HTS LEC model accurately predict voltage and central magnetic field at currents below the critical current. However, it is difficult to find constant circuit parameters that simultaneously satisfy the measured voltage and magnetic field under overcurrent conditions. Recent research highlights changes in contact resistance during transient conditions, which may impact power loss estimation in NI HTS coils. Therefore, we confirm the influence of contact resistance changes on loss calculation in the transient state for NI HTS coil. To achieve this, we introduce a measurement data analysis method based on the LEC model and compare it with the LEC model using constant circuit parameters.

Unsteady Single-Phase Natural Circulation Flow Mixing Prediction Using CATHARE Three-Dimensional Capabilities

  • Salah, Anis Bousbia;Vlassenbroeck, Jacques
    • Nuclear Engineering and Technology
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    • v.49 no.3
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    • pp.466-475
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    • 2017
  • Coolant mixing under natural circulation flow regime constitutes a key parameter that may play a role in the course of an accidental transient in a nuclear pressurized water reactor. This issue has motivated some experimental investigations carried out within the OECD/NEA PKL projects. The aim was to assess the coolant mixing phenomenon in the reactor pressure vessel downcomer and the core lower plenum under several asymmetric steady and unsteady flow conditions, and to provide experimental data for code validations. Former studies addressed the mixing phenomenon using, on the one hand, one-dimensional computational approaches with cross flows that are not fully validated under transient conditions and, on the other hand, expensive computational fluid dynamic tools that are not always justified for large-scale macroscopic phenomena. In the current framework, an unsteady coolant mixing experiment carried out in the Rossendorf coolant mixing test facility is simulated using the three-dimensional porous media capabilities of the thermal-hydraulic system CATHARE code. The current study allows highlighting the current capabilities of these codes and their suitability for reproducing the main phenomena occurring during asymmetric transient natural circulation mixing conditions.

Computational Heat Transfer Analysis of Dish Type Solar Receiver Using the Transient model (CFD를 이용한 접시형 태양열 집열기의 과도 열전달 모델 해석)

  • Oh, Sang-June;Lee, Ju-Han;Seo, Joo-Hyun;Lee, Jin-Gyu;Cho, Hyun-Seok;Seo, Tae-Beom
    • New & Renewable Energy
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    • v.4 no.4
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    • pp.72-79
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    • 2008
  • A numerical and experimental studies are carried out to investigate the transient heat transfer characteristics of 5kWth dish type solar air receiver. Measured solar radiation and temperatures at several different locations are used as boundary conditions for numerical a. Many parameters' effects (reflectivity of the reflector, the thermal conductivity of the receiver body, transmissivity of the quartz window, etc.) on the thermal performance are investigated. Discrete Transfer Method is used to calculate the radiation heat exchange in the receiver. A transient heat transfer model is developed and the rate of radiation, convection and conduction heat transfer are calculated. Comparing of the experimental and the numerical results, results of both are in good agreement. Using the numerical model, the transient heat transfer characteristics of volumetric air receiver for dish type solar thermal systems are known and the transient thermal performance of the receiver can be estimated.

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LDO Regulator with Improved Transient Response Characteristics and Load Transient Detection Structure (Load Transient Detection 구조 및 개선된 과도응답 특성을 갖는 LDO regulator)

  • Park, Tae-Ryong
    • Journal of IKEEE
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    • v.26 no.1
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    • pp.124-128
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    • 2022
  • Conventional LDO regulator external capacitors can reduce transient response characteristics such as overshoot and undershoot. However, the capacitorless LDO regulator proposed in this study applied body technology to the pass transistor to improve the transient response and provide excellent current drive capability. The operating conditions of the proposed LDO regulator are set to an input voltage that varies from 3.3V to 4.5V, a maximum load current of 200mA, and an output voltage of 3V. As a result of the measurement, it was found that when the load current was 100 mA, the voltage was 95 mV in the undershoot state and 105 mV in the overshoot state.

On the measurement of the transient dynamics of the nanocomposites reinforced concrete systems as the main part of bridge construction

  • Shuzhen Chen;Hou Chang-ze;Gongxing Yan;M. Atif
    • Structural Engineering and Mechanics
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    • v.90 no.4
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    • pp.417-428
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    • 2024
  • Nanocomposite-reinforced concrete systems have gained increasing attention in bridge construction due to their enhanced mechanical properties and durability. Understanding the transient dynamics of these advanced materials is crucial for ensuring the structural integrity and performance of bridge infrastructure under dynamic loading conditions. This paper presents a comprehensive study of the measurement techniques employed for assessing the transient dynamics of nanocompositereinforced concrete systems in bridge construction applications. A numerical method, including modal analysis are discussed in detail, highlighting their advantages, limitations, and applications. Additionally, recent advancements in sensor technologies, data acquisition systems, and signal processing techniques for capturing and analyzing transient responses are explored. The paper also addresses challenges and opportunities in the measurement of transient dynamics, such as the characterization of nanocomposite-reinforced concrete materials, the development of accurate numerical models, and the integration of advanced sensing technologies into bridge monitoring systems. Through a critical review of existing literature and case studies, this paper aims to provide insights into best practices and future directions for the measurement of transient dynamics in nanocompositereinforced concrete systems, ultimately contributing to the design, construction, and maintenance of resilient and sustainable bridge infrastructure.