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Review of spatial scale dispersion models (ATDMs) to simulate environmental dispersion and deposition of radionuclides and the overview of GIS coupling with dispersion models

International Journal of Advanced Nuclear Reactor Design and...

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International Journal of Advanced Nuclear Reactor Design and Technology 2024年第4期6卷 256-280页

作者： Muhammad, Hussaini Xuan, Wang Wang, Mingjun Su, Guanghui School of Nuclear Science and Technology Shanxi Key Laboratory of Advanced Nuclear Energy and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Abuja Nigeria

Estimation of the radiological consequences including the calculation of radiation doses to the exposed population requires numerical evaluation of atmospheric radioactive releases from nuclear facilities under accidental scenarios for implementation of adequate protective and other response actions to prevent or minimize severe deterministic effects and reduce the probability of occurrence of stochastic effects. This paper reviews various state-of-the-art spatial scale atmospheric dispersion models, known as the ATDMs, designed to evaluate atmospheric transport, dispersion, and depositions of radionuclide emissions from release sources. The ATDMs (atmospheric transport, dispersion, and deposition models) reviewed in this paper are FLEXPART, CALPUFF, LADAS, RASCAL, RIMPUFF, and HotSpot. These ATDMs are increasingly applied to perform probabilistic radiological risk assessment, which is one of the IAEA safety requirements for site evaluation of new NPP, and the calculated doses can be used to establish EPZs, an underlying basis of emergency preparedness. The numerical approaches, modeling methodology, advantages, limitations, scope of applications, and research investigations performed using these models in radiological and other environmental impact assessments within their scope of applications are presented. GIS has been widely recognized as a technique applied to aid the modeling of pollutant dispersion and visualization of model outputs in a spatial context, among other benefits. In nuclear accident consequence evaluation, spatial data provides key information such as accident location, range of radiological contamination, population density, etc, which are very important. This demonstrates the high significance of GIS-ATDMs coupling. Therefore, an overview of the coupling of dispersion models with GIS is also highlighted. © 2025 Xi'an Jiaotong University

关键词： Risk assessment

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Optimization on ignition timing and EGR ratio of a spark-ignition engine fuelled with natural gas-hydrogen blends

Optimization on ignition timing and EGR ratio of a spark-ign...

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SAE 2011 World Congress and Exhibition

作者： Hu, Erjiang Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

In this paper, 20%H2 (20% hydrogen in natural gas-hydrogen blends, by volume) is selected as the test fuel, and the ignition timing and EGR ratio are adjusted to optimize the performance, combustion, and emissions of a natural gas-hydrogen engine. An experimental investigation on the effect of ignition timings, EGR ratios on combustion behaviors and emissions of a spark-ignition engine fuelled with natural-gas and hydrogen blends was conducted. When increasing the ignition timing at specified EGR ratio, engine power output will give its peak value at MBT timing. Large EGR introduction decreases engine power output and increases combustion duration. Effective thermal efficiency shows an increasing trend at the small EGR ratio and a decreasing trend with further increasing EGR ratio. With advancing the ignition timing, the flame development duration is increased, and the rapid combustion duration and total combustion duration are decreased. All of these three kinds of combustion duration are increased with the increase of EGR ratio. HC concentration is decreased and NOx concentration is increased with advancing the ignition timing while CO emission varies little with the ignition timing. NOx concentration is decreased with the increase of EGR ratio. HC emission is increased with the increase of EGR ratio. CO and CO2 emissions show little variations with the EGR ratio and ignition timing. Based on the above analysis, a MAP containing ignition timings and EGR ratios for 20%H2 fuel blend is presented, and this will provide the reference and guidance to engine designers and engineers. In addition, through optimizing ignition timing and EGR ratio, high efficiency and low emission spark-ignition engine can be realized fueled with natural gas-hydrogen blends. Copyright © 2011 SAE International.

关键词： Natural gas

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Experimental and modeling study on ignition delay times of dimethyl ether/ n -butane blends at a pressure of 2.0 MPa

Experimental and modeling study on ignition delay times of d...

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作者： Jiang, Xue Zhang, Yingjia Man, Xingjia Pan, Lun Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

In this study, the ignition delay times of dimethyl ether (DME)/n-C 4H10 fuel blends, neat DME, and neat n-C4H 10 diluted with argon were measured behind reflected shock waves. The experiments were performed in the temperature range of 1100-1600 K, at a pressure of 2.0 MPa, and equivalence ratios from 0.5 to 2.0. A latest kinetic mechanism NUIG Aramco Mech 1.3 was validated against the measured ignition data and used to conduct the chemical kinetic analysis. Results showed that different equivalence ratio-dependent behaviors were exhibited at different temperature regimes for DME, n-C4H10, and their blend. The ignition delay time of neat n-C4H10 was increased with an increase in the equivalence ratio. A strong inhibiting trend was exhibited at high temperatures. For the neat DME, however, an opposite influencing tendency from the equivalence ratio was presented in comparison to that on n-C 4H10. Ignition promotion becomes significant at relatively low temperatures. A 50% DME/50% n-C4H10 blend show a combined behavior of both n-butane and DME. Fuel reaction flux analysis, sensitive analysis, and mole fraction analysis were conducted for the understanding of the interaction between the ignition chemistries of DME and n-C4H10 at a pressure of 2.0 MPa. © 2014 American Chemical Society.

关键词： Ethers

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Multiple load short-term forecasting model of integrated energy system based on multiple LSTM networks

Multiple load short-term forecasting model of integrated ene...

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International Conference on power engineering 2021, ICOPE 2021

作者： Cai, Yanchun Xu, Kaiwen Chong, Daotong Wang, Jinshi Yan, Junjie Liu, Ming State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Accurate short-term load forecasting of integrated energy system can optimize system operation and play an important role in improving system energy efficiency. In this paper, a multiple load short-term forecasting model of integrated energy system based on multiple LSTM networks is proposed. Firstly, the load influencing factors are divided into meteorological characteristic, delay characteristic and periodic characteristic, and the correlation is calculated based on Pearson coefficient. Secondly, a load forecasting model with multiple LSTM network coupling is established to explore the relationship between load and three characteristics, and excavate the complex coupling relationship among cooling, heating and power. The results show that the model has better prediction performance compared with other commonly used models. © 2021 The Japan Society of Mechanical Engineers.

关键词： Long short-term memory

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Ventilation and cooling of wind generator: A numerical study and experimental verification 7

Ventilation and cooling of wind generator: A numerical study...

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7th International Conference on power engineering, ICOPE 2019

作者： Ao, Yunjin Li, Na Zhou, Qulan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

In the wind generator, a large amount of heat is generated during the operation, which usually causes severe temperature rise and decrease of efficiency. By coupling fluid dynamics and heat transfer, a numerical method has been developed to calculate the velocity filed and temperature distribution of a common air-cooled doubly-fed wind generator. The numerical results have been verified by the experiments. The results show that the flow resistance is higher in the center in the axial direction, thus the temperature is much higher than the ends. In the height direction, there locate the most dangerous points and the temperature rise is about 110K. In the circumference direction, there are regularity of fluctuation and can assist in finding the dangerous points. The variations of heat source and cooler power as well as rotation speed all affect the temperature rise of the generator. The regularity and method of this study can be applied to similar generators or generators of other forms, thus advice can be given for the design, manufacture, operation and maintenance of wind generators. © ICOPE 2019 - 7th International Conference on power engineering, Proceedings. All rights reserved.

关键词： Temperature distribution

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MPS analysis of molten corium jet and structure interaction during nuclear severe accident 17

MPS analysis of molten corium jet and structure interaction ...

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17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017

作者： Li, Gen Zhang, Jun Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

The melt jet and structure interaction is an important phenomenon in the progression of nuclear severe accident. It could happen when molten corium relocates onto core plate and Reactor Pressure Vessel (RPV) lower head, and in the ex-vessel accident, the molten corium may directly impinge onto and Erode concrete. In the present study, a numerical code was developed based on Moving Particle Semi-implicit (MPS) method, to analyze the erosion scenario of RPV wall and dry concrete by melt jet. The numerical modeling was validated by comparing structure erosion configuration and time-dependent erosion depth with the experimental data. In the analysis of RPV wall erosion, it indicates that no crust layer presented at the interaction of stainless steel (SS) melt jet and RPV wall, while for Zr, ZrO2 and UO2 melt jets the crust layer presented. At a superheat temperature equal to 300 K, the erosion rate by SS melt was the fastest, even though the absolute temperature was the lowest compared with other cases. In the analysis of melt jet and concrete interaction, the core melt was divided as metallic material (SS-Zr) and oxide material (ZrO2-UO2). The results indicate that the crust and ablated concrete layer presented at the interface of UO2-ZrO2 melt and concrete, whereas no crust could be found in the interaction of SS-Zr melt with concrete. The erosion progression was faster in the erosion by metallic melt jet than by oxidic melt jet. The present analysis demonstrates that the erosion rate was affected not only by temperature, but also by crust layer, and the major threat to structure was metallic melt, especially at high temperature. © 2016 Association for Computing Machinery Inc. All Rights Reserved.

关键词： Erosion

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Experimental study on preparation of amorphous SiO2 by fluidized bed combustion of rice husk 7

Experimental study on preparation of amorphous SiO2 by fluid...

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7th International Conference on power engineering, ICOPE 2019

作者： Yao, Yashu Xu, Heng Tan, Jingkao Hu, Zhengtao Zhou, Qulan Li, Na State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

The rice husk ash (RHA) contains a large amount of amorphous silica having a large specific surface area and high activity, but after combustion of the rice husk the SiO2 is easily crystallized, which deteriorate the performance. Therefore, it is necessary to study the crystallization process of silica in combustion for the preparation of excellent rice husk ash. On the self-built fluidized bed experimental system, the combustion characteristics of rice husk and the pore characteristics of RHA under different excess air coefficients were studied. It was found that when the excess air ratio was between 0.8 and 0.9, the silica remained unchanged, and the specific surface area of rice husk ash is larger. Meanwhile, the furnace temperature is higher, which is conducive to the utilization of heat;when the excess air ratio is greater than 1, the crystallization of rice husk ash is more serious. In conclusion, it should be burned when the excess air ratio is less than 1 in order to prepare RHA with large specific surface area by direct combustion method. © ICOPE 2019 - 7th International Conference on power engineering, Proceedings. All rights reserved.

关键词： Silica

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Interfacial stability in vertical swirling annular two-phase flow 16

Interfacial stability in vertical swirling annular two-phase...

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16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2015

作者： Liu, Li Bai, Bofeng State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

ISBN: (纸本)9781510811843

The linear stability of liquid film flowing upward the inner surface of vertical cylinder under the action of the swirling gas core flow is investigated taking exactly the centrifugal force and curvature of the cylinder into account. Swirl has been considered by superposing a circular movement on the annular flow. The theoretical model of the stability of interface to small perturbation is established by analyzing the normal force balance condition at the wavy interface. The characteristic equation is solved and the stability criterion is obtained. The stability characteristics of neutral, growing and damped modes are presented showing the influences of swirl intensity, relative motion of gas-liquid flow, and the surface tension force. The modeling results indicate that the swirling of the gas phase stabilizes the film flow while the curvature of the cylinder destabilizes it. For strong swirling annular flow, it is found that there is a small influence of surface tension on the stability of interface because the stabilizing centrifugal force is dominant on this condition. The neutral wavelength is found to be very sensitive to the values of swirl intensity and cylinder radius when gas-liquid relative movement is small. However, when gas flow rate is large enough, there is no significant difference in its value.

关键词： Stability criteria

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Numerical modeling of heat transfer in a two-phase closed thermosyphon 24

Numerical modeling of heat transfer in a two-phase closed th...

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24th IIR International Congress of Refrigeration, ICR 2015

作者： Cao, Jing Li, Mei Li, Bowen Hou, Yu Zhang, Xingqun State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

ISBN: (纸本)9782362150128

Heat pipe technology is widely applied in the heat transfer systems of many equipment. Two-phase closed thermosyphon (TPCT) is one of the heat pipes which could work with the help of natural gravity. TPCT is adopted in many occasions, such as the waste heat recovery system, the ground source heat pumps, the preservation of permafrost and the de-icing of roadways. In this paper, a comprehensive numerical model is established to describe the condensation and evaporation of thermosyphon. The volume of fluid (VOF) model is employed to describe the interface between vapor and liquid phases. The predicted temperature distribution on the thermosyphon wall agreed well with the published experimental data in the trend.

关键词： Thermosyphons

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Thermo-economic optimization of the dual-pressure condenser for 700 °C ultra-supercritical coal-fired power plants

Thermo-economic optimization of the dual-pressure condenser ...

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2019 Canadian Society for Civil engineering Annual Conference, CSCE 2019

作者： Fu, Yue Liu, Ming Wang, Liyuan Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

ISBN: (纸本)9780791883747

Pulverized coal power is one of major contributor in power production, whose efficiency can be enhanced by increasing the main steam parameters and adjusting the cold end system parameters. The thermo-economic optimization of the cold end system for 700 °C ultra-supercritical coal-fired power plants were carried out in this study. The condenser pressure was thermoeconomically optimized for the single-pressure condenser systems. Then, with the same heat transfer area of the optimized single-pressure condenser, the dual-pressure condenser system was thermo-economically optimized. The distributions of heat transfer area and exhaust steam mass flow between the highpressure and low-pressure chambers in the dual-pressure condenser system were optimized. The results show that the optimal vacuum pressure of the single-pressure condenser is 3 kPa and the optimal heat transfer area is 27 km2. For the dualpressure condenser system, the cost of dual-pressure condenser is reduced to the minimum value 1.3 million CNY/year. The power plant efficiency is increased by the maximum value 0.1% when the heat transfer area and exhaust steam mass flow rate are distributed equally between two chambers, compared with that of the single-pressure condenser system. The optimal values of the low-pressure and high-pressure chamber are 2.4 kPa and 3.2 kPa, respectively. This paper provides the reference for the design optimization of cold end system for high parameter power units. Copyright © 2020 ASME.

关键词： Coal fired power plant

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