Quasi‐steady‐state large‐signal modelling of DC–DC switching converter: justification and application for varying operating conditions

Ion dump is an important functional component of the Neutral Beam Injection (NBI) system of Experimental Advanced Superconducting Tokamak (EAST) for absorbing un-neutralized particles deflected by deflection magnets during neutralization, and by means of the corresponding measurement and analyzing method on it, the total energy deposition value and instantaneous energy deposition distribution of the deflected ion beam can be obtained. According to the operation mechanism of the NBI system, ion dump is directly subjected to high-energy particle bombardment for long time, the corresponding heat-loaded on its plates is high, so the temperature rise control is demanding. In order to realize the running power of 2–4MW and running pulse length of more than 100s or even 1000s in the future NBI system, the structure of the ion dump must be designed in accordance with the quasi-steady state operation requirements to provide the guarantee for the steady state operation of EAST system. The Hypervapotron structure based on the subcooled boiling principle is used as an alternative structure to enhance the heat transfer of this high-heat-flux component. According to the operating requirements, space requirements, measurement requirements and beam power distribution characteristics, the engineering design and implementation of ion dump based on the enhanced heat transfer structure is realized for the future long pulse quasi-steady NBI system. The computational results of the heat-fluid-solid coupling simulation based on the two-phase heat transfer are also confirmed the feasibility of the proposed ion dump structure under quasi-steady-state operating conditions. This study is of great significance to explore the optimal heat transfer structure for quasi-steady ion dump to realize the high current, quasi-steady state and high power operation of EAST-NBI system.

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Capturing the spectral response of solar cells with a quasi-steady-state, large-signal technique

Progress in Photovoltaics Research and Applications ◽

10.1002/pip.661 ◽

2006 ◽

Vol 14 (3) ◽

pp. 203-212 ◽

Cited By ~ 6

Author(s):

Helmut Mäckel ◽

Andrés Cuevas

Keyword(s):

Solar Cells ◽

Steady State ◽

Spectral Response ◽

Quasi Steady State ◽

Large Signal

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Experimental Study of the Effect of Hydrogen Inflow on Passive Core Cooling System With Natural Circulation Flow

Volume 3: Student Paper Competition; Thermal-Hydraulics; Verification and Validation ◽

10.1115/icone2020-16949 ◽

2020 ◽

Author(s):

Yasunori Yamamoto ◽

Masayoshi Mori ◽

Kosuke Ono ◽

Tetsuya Takada

Keyword(s):

Steady State ◽

Cooling System ◽

Natural Circulation ◽

Operating Conditions ◽

Quasi Steady State ◽

Circulation Flow ◽

Term Operation ◽

Accident Conditions ◽

Core Cooling

Abstract Isolation Condenser (IC) is one of the passive core cooling systems with natural circulation flow, which is effective for safety measures against station black out. Once core uncover occurs, hydrogen generated in the core affects operating condition of ICs. To use ICs as an important safety measure not only for transient conditions but also for accident conditions, robustness of ICs against hydrogen inflow must be understood well. In this study, experiments with high pressure steam were conducted using experimental setup simulating IC, where helium was injected to simulate hydrogen effects. When the pressure in an accumulator increased high enough, natural circulation flow generated in the experimental loop. After the long-term operation, the pressure and the natural circulation flow rate achieved nearly constant. The pressure at quasi-steady state increased with increasing the helium injection amount. The pressure difference in a section including outlet side of a vertical pipe was slightly increased when helium was injected which may have indicated that the helium accumulated in the section and caused increment of the pressure loss. The startup pressure of the IC simulator also increased when helium was injected, where the driving force by the water head difference also decreased. Though long-term operations were performed after helium injection, the effect of injected helium on operating conditions of the IC remained for quasi-steady state conditions.

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TRANSIENT OPERATION OF SENSIBLE FIXED-BED REGENERATORS

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4053486 ◽

2022 ◽

pp. 1-16

Author(s):

Hadi Ramin ◽

Easwaran N Krishnan ◽

Gurubalan Annadurai ◽

Carey J. Simonson

Keyword(s):

Steady State ◽

Fixed Bed ◽

Operating Conditions ◽

Design Parameters ◽

Transient Temperature ◽

Quasi Steady State ◽

Transient Operation ◽

Steady State Condition ◽

Test Standards ◽

Wide Range

Abstract Fixed-bed regenerator is a type of air-to-air energy exchanger and recently introduced for energy recovery application in HVAC systems because of their high heat transfer effectiveness. Testing of FBRs is essential for performance evaluation and product development. ASHRAE and CSA recently included guidelines for testing of FBRs in their respective test standards. The experiments on FBRs are challenging as they never attain a steady state condition, rather undergoes a quasi-steady state operation. Before reaching the quasi-steady state, FBRs undergo several transient cycles. Hence, the test standards recommend getting measurements after one hour of operation, assuming FBR attains the quasi-steady state regardless of test conditions. However, the exact duration of the initial transient cycles is unknown and not yet studied so far. Hence, in this paper, the duration of FBR's transient operation is investigated for a wide range of design and operating conditions. The test standards' recommendation for the transient duration is also verified. The major contributions of this paper are (i) quantifying the effect of design parameters (NTUo and Cr*) on the duration of transient operation and (ii) investigation of the effect of sensor time constant on the transient temperature measurements. The results will be useful to predict and understand the transient behavior of FBRs accurately.

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A criterion based on computational singular perturbation for the construction of reduced mechanism for dimethyl ether oxidation

Journal of the Serbian Chemical Society ◽

10.2298/jsc121122023w ◽

2013 ◽

Vol 78 (8) ◽

pp. 1177-1188

Author(s):

Zuozhu Wu ◽

Xinqi Qiao ◽

Zhen Huang

Keyword(s):

Steady State ◽

Singular Perturbation ◽

Dimethyl Ether ◽

Reduction Process ◽

Operating Conditions ◽

Quasi Steady State ◽

Reduced Mechanism ◽

Wide Range ◽

Computational Singular Perturbation ◽

Premixed Laminar

A criterion based on the computational singular perturbation (CSP) method is proposed in order to determine the number of quasi-steady state (QSS) species. This criterion is employed for the reduction of a detailed chemical kinetics mechanism for the oxidation of dimethyl ether (DME), involving 55 species and 290 reactions, leading to a 20 steps reduced mechanism which involves 26 species. A software package, named I-CSP, was developed to make the reduction process algorithmic. Input to the I-CSP includes (i) the detailed mechanism, (ii) the numerical solution of the problem for a specific set of operating conditions, (iii) the number of quasi steady state (QSS) species. The resulting reduced mechanism was validated both in homogenous reactor, including auto-ignition and PSR, over a wide range of pressures and equivalence ratios, and in a one-dimensional, unstretched, premixed, laminar steady DME/Air flame. Comparison of the results calculated with the detailed and the reduced mechanisms shows excellent agreement in the case of homogenous reactor, but discrepancies can be observed in the case of the premixed laminar flame.

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