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Study of helium diffusion in yttria: A multiscale approach based on the density functional theory and kinetic Monte Carlo, with transmission electron microscopy and thermo-desorption spectroscopy

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JOURNAL OF NUCLEAR MATERIALS 2024年 597卷

作者： Cavalcanti, Vinicius Oliveira Roques, Jerome Horlait, Denis Gilabert, Eric Riant, Guillaume Colombeau-Bedos, Thomas Clavier, Nicolas Gentils, Aurelie Univ Paris Saclay IJCLab IN2P3 CNRS F-91405 Orsay France Univ Bordeaux CNRS LP2I UMR 5797 F-33170 Gradignan France Univ Montpellier ICSM CEA CNRSENSCM F-30207 Bagnols Sur Ceze France

A known issue for future nuclear reactors is helium accumulation inside the steel structure materials, responsible for structural issues such as embrittlement and cracking. One possible solution is using new types of reinforced steel, such as oxide dispersion strengthened (ODS) steel. It consists of adding oxide nanoparticles to the Fe-based material, especially yttrium oxide (yttria, Y2O3), improving its properties. Therefore, one first step is understanding the helium diffusion inside this system. Very little is known about helium inside yttria, with most studies being theoretical ones. Based on this context, this work proposes a combined theoretical and experimental multiscale approach to investigate helium diffusion inside yttria. The theoretical approach starts with the density functional theory, used to model the atomic yttria cell and determine helium insertion sites. The transitions between the sites were described using the Nudged Elastic Bond (NEB) method. Kinetic Monte Carlo was then employed to obtain the interstitial diffusion coefficient expression for the first time for this material. It showed a limited diffusion at temperatures below 600 K, which may indicate a tendency for He to be blocked in the oxide. Then, the charged vacancies were explored. It showed that the vacancy further reduces helium diffusion. Finally, it was demonstrated that helium spreads across different vacancies and interstitial sites. The experimental part involved implanting helium ions at 50 keV in samples with nanometric or micrometric grains. Then, the specimens were characterised with transmission electron microscopy (TEM) and thermodesorption spectroscopy (TDS) techniques. TEM did not evidence detectable bubbles even at the highest studied fluence (1 x 1016 cm-2). The TDS highlighted different mechanisms for helium diffusion and the grain size's role, providing a novel model for diffusion coefficient calculation based on interstitial diffusion.

关键词： ODS steel Helium diffusion numerical and experimental methods TEM TDS DFT

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numerical model of cake baking based on enthalpy-porosity method

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JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY 2024年第4期38卷 2081-2089页

作者： Lee, Dong Jae Kim, Gyeong Min Park, Su Il Jeong, Jeong Hoon Kim, Doo Hyun Kim, Young Soo Park, Yong Gap Ha, Man Yeong LG Elect Home Appliance & Air Solut Co Chang Won South Korea Pusan Natl Univ Sch Mech Engn Busan South Korea LG Elect H&A R&D Ctr 170Sanpaechong ro Changwon Si Gyeongsangnam D South Korea Changwon Natl Univ Dept Mech Engn Chang Won 641773 South Korea

This study proposes a numerical model of the cake-baking process, including its heat and mass transfer processes and the phase change process of water, using the enthalpy-porosity method. The specific heat and thermal conductivity of the cake dough were measured as functions of temperature using a differential scanning calorimeter and the hot plate method with a probe, respectively, for a numerical evaluation of the variations in the thermo-physical properties of the cake dough. The internal and upper-surface temperatures of the cake were measured using thermocouples and an infrared camera, respectively. The mass loss of the cake was measured to determine its water content fraction. The commercial computational fluid dynamics software Fluent 19.2 was used to develop the numerical model of cake baking. The experimental and numerical model results were compared quantitatively and showed excellent agreement. In general, the temperature in the central region of the cake was lower than the internal temperature close to the cake pan. The upper-surface temperatures of the cake exceeded 100 degrees C and tended to increase toward the cake edge. The water content initially decreased linearly with time. Finally, the correlation between the upper-surface temperature and brightness of the cake dough was examined to determine the cake-baking performance.

关键词： Baking Thermo-physical property variation Heat and mass transfer Phase change Enthalpy-porosity method numerical and experimental methods

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experimental and numerical research on flow characteristics of inlet particle separator for aero-engine under the influence of water film

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART G-JOURNAL OF AEROSPACE ENGINEERING 2023年第12期237卷 2772-2787页

作者： Luo, Mingcong Hu, Qionglei Liu, Aocheng Ooi, Kim Tiow Zheng, Qun Yan, Shilin Harbin Engn Univ Coll Power & Energy Engn Harbin Peoples R China Shanghai Marine Equipment Res Inst Shanghai Peoples R China Nanyang Technol Univ Sch Mech & Aerosp Engn Singapore Singapore

An aero-engine must be able to operate in all-weather conditions, which requires the aircraft to be safe throughout the flight even in bad weather. Excessive intake of rainwater can induce stall and surge of compressor and flameout of combustion chamber, which will lead to the loss of power of the engine. In rainy weather, water come into the engine inlet protection device, which directly determines the compressor inlet conditions and will further affect the compressor working condition and the matching features. In this paper, special attention was paid to the experimental characteristics of aero turbo-shaft engine inlet particle separator (IPS) and the numerical study employing ANSYS-CFX under water spraying condition. Based on the phenomenon of water film forming on the wall surface of the IPS and the experimental data under different water spraying conditions, combined with the predictions from CFD study, an empirical model of water film flow on the wall surface has been developed. The results indicate that in the case of high water ingestion, droplets will inevitably form water film on the wall after entering the IPS. Due to the viscous resistance of wall water film and its influence on the airflow boundary layer, the flow state inside the IPS will change. By establishing a wet wall water film model, the flow characteristics near the wall are closer to the experimental state. The total pressure loss prediction error was reduced from 24.8% to 5.2% and 26.4% to 5.7% under the uniform water spraying rate of 2.93% and 4.84%, respectively.

关键词： Water ingestion aero turbo-shaft engine inlet particle separator wet wall water film model numerical and experimental methods

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A study on the hydraulic and thermal characteristics in fractal tree-like microchannels by numerical and experimental methods

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2012年第25-26期55卷 7499-7507页

作者： Yu, Xiang-fei Zhang, Chun-ping Teng, Jyh-tong Huang, Su-yi Jin, Shi-ping Lian, Yi-fu Cheng, Ching-hung Xu, Ting-ting Chu, Jiann-cherng Chang, Yaw-Jen Thanhtrung Dang Greif, Ralph Chung Yuan Christian Univ Dept Mech Engn Chungli 32023 Taiwan Huazhong Univ Sci & Technol Sch Energy & Power Engn Wuhan 430074 Peoples R China Ho Chi Minh City Univ Tech Educ Dept Heat & Refrigerat Technol Ho Chi Minh City Vietnam Univ Calif Berkeley Dept Mech Engn Berkeley CA 94720 USA

This paper focused on the hydraulic and thermal characteristics of fractal tree-like microchannels with different ARs (aspect ratios) for the Reynolds numbers ranging from 150 to 1200. And the fractal microchannels with two branches and straight microchannels with the same heat transfer area were also compared in terms of the pressure loss, mean heat transfer coefficient, and COP (coefficient of performance). The experimental results showed that the fractal tree-like microchannels had a much higher heat transfer coefficient than that of straight microchannels at the cost of a much higher pump power. And for fractal and straight microchannels, the AR of microchannels was also found to have a relatively large impact on both the pressure loss and heat transfer. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： Fractal tree-like microchannels Hydraulic and thermal behaviors numerical and experimental methods

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Performance Optimization of the High-Pressure Compressor in Series Two-Stage Turbocharging System Based on Low-Speed Performance Requirements of Diesel Engine

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JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME 2022年第8期144卷 081008-081008页

作者： Liang, Dingkun Yang, Hanqian Li, Qingbin Xu, Cheng Xie, Qiuyuan Cent South Univ Forestry & Technol Changsha 410000 Hunan Peoples R China Hunan Tyen Machinery Co Ltd Hengyang 421200 Hunan Peoples R China Hunan Fazel Power Remfg Co Ltd Changsha 410000 Hunan Peoples R China

The performance of the high-pressure (HP) compressor is very important for the two-stage turbocharging system. However, the performance of HP compressor on the engine most of the time is poor at low speed and low mass flow conditions. These will lead to poor engine performance at low engine speed. The purpose of this paper is to improve the performance of the HP compressor at low speed and low mass flow conditions. The Latin hypercube design of the experiment method is used to establish the Kriging model and global optimization by multi-objective genetic algorithm NSGA-II to optimal HP compressor. The simulation results indicated that the flow field within the compressor was improved and the high entropy generation area was reduced. The new design delayed the mixing between the tip clearance leakage vortex flow and main flow. The low-speed performance of the HP compressor was improved. The turbocharger gas stand tests and engine bench tests were carried out. The results showed that the efficiency and pressure ratio of the optimized design is increased by 2.1% and 3%, respectively. The engine achieved better performance in low-speed conditions. The pumping means effective pressure (PMEP) and intake airflow increased by 7% and 4.98%, respectively, while brake specific fuel consumption (BSFC) and soot emissions decreased by 0.56% and 32.8%, respectively.

关键词： two-stage turbocharger low-speed performance engine performance fuel economy and emissions numerical and experimental methods multi-objective optimization method

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An alternative approach to thermal analysis using inverse problems in aluminum alloy welding

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INTERNATIONAL JOURNAL OF numerical methods FOR HEAT & FLUID FLOW 2017年第3期27卷 561-574页

作者： Magalhaes, Elisan dos Santos da Silva, Cristiano Pedro Fernandes Lima e Silva, Ana Lucia Marcondes Lima e Silva, Sandro Metrevelle Univ Fed Itajuba Inst Engn Mech Itajuba Brazil

Purpose - The purpose of this article is the determination of the temperature fields in a weld region has always been an obstacle to the improvement of welding processes. As an alternative, the use of inverse problems to determine the heat flux during the welding process allows an analysis of these processes. Design/methodology/approach - This paper studies an alternative for the thermal analysis of the tungsten inert gas welding process on a 6,060 T5 aluminum alloy. For this purpose, a C++ code was developed, based on a transient three-dimensional heat transfer model. To estimate the amount of heat delivered to the plate, the specification function technique was used. Lab experiments were carried out to validate the methodology. A different experimental methodology is proposed to estimate the emissivity (radiation coefficient). Findings - The maximum difference between experimental and numerical temperatures is lower than 5 per cent. The determined emissivity value for the aluminum 6,060 T5 presented a good agreement with literature values. The thermal fields were analyzed as function of the positive polarity. The specification function method proved to be an adequate tool for heat input estimation in welding analysis. Originality/value - The proposed methodology proves to be a cheaper way to estimate the heat flux on the sample. The estimated power curves for the welding process are presented. The methodology to calculate the emissivity (radiation coefficient) was validated.

关键词： Heat transfer Welding process Heat flux estimation Inverse problems numerical and experimental methods

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numerical Analysis on the Pressure Distribution of Long Oblate Chimney

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International Conference on Manufacturing Engineering and Automation (ICMEA 2012)

作者： Yuan, Zi Hou Zhan, Zhi Lan Wuhan Text Univ Dept Mech Wuhan 430073 Hubei Peoples R China

ISBN: (纸本)9783037855300

In order to investigate wind load for long oblate chimney, a commercial computational software "Fluent" was employed to solve the time-averaged k-epsilon turbulent flow model for Realizable form. The flow structure and surface pressure distribution on the long oblate chimney upon facing wind was obtained for the wide-face and the narrow-face, respectively. The windward side of long oblate chimneys bears positive pressure, while the largest negative pressure area is on both sides of chimney. The characteristics of the wind pressure distribution were explained by analyzing the flow around the chimney. These discoveries can be used as a reference, for the new version of the wind load criteria.

关键词： Computational fluid dynamics Long Oblate Chimney numerical and experimental methods Wind Angle k-epsilon model in Realizable form Steady incompressible flow

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numerical analysis of the pressure field on curved and open self-weighted metallic roofs due to the wind effect by the finite volume method

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APPLIED MATHEMATICS AND COMPUTATION 2009年第1期209卷 31-41页

作者： Diaz, J. J. del Coz Nieto, P. J. Garcia Perez, J. A. Gonzalez Navarro, A. Martin Univ Oviedo Dept Construct Engn High Polytech Sch Gijon 33204 Spain Univ Oviedo Dept Math Fac Sci Oviedo 33007 Spain Univ Seville Dept Design Engn Escuela Super Ingenieros Seville 41092 Spain

In this paper, an evaluation of distribution of the air pressure is determined throughout the curved and open self-weighted metallic roof due to the wind effect by the finite volume method. Data from experimental tests carried out in a wind tunnel involving a reduced scale model of a roof as well as our previous results using the finite element method (FEM) [J.J. del Coz, P.J. Garc a Nieto, F.J. Suarez Dominguez, numerical analysis of pressure field on curved self-weighted metallic roofs due to wind effect by the finite element method, J. Comput. Appl. Math. 192 (1) (2006) 40-50.] were used for comparison. The non-linearity is due to Navier-Stokes equations that govern the turbulent flow. The calculation has been carried out keeping in mind the possibility of turbulent flow in the vicinities of the walls, and speeds of wind have been analyzed understood between 30 and 40 m/s. Finally the forces and moments are determined on the cover, as well as the distribution of pressures on the same one, comparing the results obtained with the Spanish and European Standards rules, given place to the conclusions that are exposed in the study. (C) 2008 Elsevier Inc. All rights reserved.

关键词： Computational fluid dynamics Finite volume modeling numerical and experimental methods Steady incompressible flow Curved self-weighted metallic roofs

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Influence of Road Texture on Tyre/Road Contact in Static Conditions numerical and experimental Comparison

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ROAD MATERIALS AND PAVEMENT DESIGN 2008年第4期9卷 689-710页

作者： Cesbron, Julien Anfosso-Ledee, Fabienne Yin, Hai Ping Duhamel, Denis Le Houedec, Donatien LCPC F-44341 Bouguenais France Univ Paris Est UR Navier Ecole Natl Ponts & Chaussees F-77455 Marne La Vallee 2 France Ecole Cent Nantes GeM F-44321 Nantes 3 France

This paper deals with the influence of road texture on normal pressure distribution for tyre/road contact in statics, within the framework of rolling noise prediction. A contact model is developed in statics where the tyre tread is modelled by air elastic half-space and the road surface by several perfectly rigid asperities. The problem is solved using a Two-scale Iterative Method (TIM) which is fast and efficient. The numerical results give high resolution contact patterns for real road surfaces. Predicted results are compared to contact pressures measured between a slick tyre and several road surfaces. The agreement is fairly acceptable by keeping in mind both the precision of the measurement device and the simplicity of the model. The best correlations are obtained for model surfaces composed of spherical punches and real road surfaces of moderated or high macro-texture. The results are less conclusive for road surfaces of fine macro-texture. The efficiency of the TIM at a tyre/road contact scale is an encouraging first step before introducing dynamical effects.

关键词： Tyre/Road Contact Road Texture Tyre Print Pressure Measurements numerical and experimental methods

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Influence of Road Texture on Tyre/Road Contact in Static Conditions

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Road Materials and Pavement Design 2008年第4期9卷 689-710页

ABSTRACTABSTRACTThis paper deals with the influence of road texture on normal pressure distribution for tyre/road contact in statics, within the framework of rolling noise prediction. A contact model is developed in statics where the tyre tread is modelled by an elastic half-space and the road surface by several perfectly rigid asperities. The problem is solved using a Two-scale Iterative Method (TIM) which is fast and efficient. The numerical results give high resolution contact patterns for real road surfaces. Predicted results are compared to contact pressures measured between a slick tyre and several road surfaces. The agreement is fairly acceptable by keeping in mind both the precision of the measurement device and the simplicity of the model. The best correlations are obtained for model surfaces composed of spherical punches and real road surfaces of moderated or high macro-texture. The results are less conclusive for road surfaces of fine macro-texture. The efficiency of the TIM at a tyre/road contact scale is an encouraging first step before introducing dynamical effects.

关键词： Tyre/Road Contact Road Texture Tyre Print Pressure Measurements numerical and experimental methods

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