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three-dimensional Numerical Simulation of Ice Crystal Melting in Jet Engine

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Journal of Thermal Science 2019年第5期28卷 984-992页

作者： ZHU Pengfei ZHANG Jiachen HAN Bingbing ZHANG Lifen LIU Zhenxia School of Power and Energy Northwestern Polytechnical University Xi'an 710129 China Shanghai Aircraft Airworthiness Certification Center of CAAC Shanghai 200335 China

A method was presented for calculating the melting rate of ice crystals in different axial positions in a compressor. The volume of fluid model and enthalpy-porosity model were used to simulate the melting process of single ice crystal. The result was validated by experimental data from literature. The change of the liquid fraction of the ice crystals with the axial position was obtained when the temperature distribution inside the compressor was introduced into the melting process. The liquid fraction of the spherical ice crystals was fitted with the ice crystal diameter as a variable, and the general distribution function for computing liquid fraction in any axial position in the compressor was obtained. The function of axial position as a variable for non-spherical ice crystal was also got.

关键词： ice crystals three-dimensional simulation melting process liquid fraction

three-dimensional time-varying sliding mode guidance law against maneuvering targets with terminal angle constraint

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Chinese Journal of Aeronautics 2022年第4期35卷 303-319页

作者： Xinxin WANG Hongqian LU Xianlin HUANG Yefeng YANG Zongyu ZUO Center for Control Theory and Guidance Technology Harbin Institute of TechnologyHarbin 150001China The Seventh Research Division Beihang UniversityBeijing 100191China

This paper deals with the problem of intercepting maneuvering targets with terminal angle constraints for missiles subjected to three-dimensional non-decoupling engagement *** achieve the finite-time interception and satisfactory overload characteristics, a time varying sliding mode control methodology is developed based on a time base generator function. The main feature of the proposed guidance law guarantees the Line-of-Sight(LOS) angles to converge to small neighborhoods of the desired values at the interception time. First, a fractional power extended state observer is used to estimate the unknown target acceleration, which can significantly reduce the adaptive switching gain. The fractional power extended state observer enjoys the advantage of better noise tolerance. Then, a newly designed sliding mode surface is constructed by introducing a time base generator function and the time-varying sliding mode guidance law is developed based on this time-varying sliding surface. The proposed guidance law significantly reduces the overload magnitudes. Numerical simulations are carried out to verify the performance of the proposed guidance law.

关键词： Guidance law Maneuvering target Terminal angle constraint three-dimensional Time-varying sliding mode

three-dimensional Numerical Study on Thermal Performance of a Super Large Natural Draft Cooling Tower of 220m Height

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Journal of Thermal Science 2013年第3期22卷 234-241页

作者： JIN Tai ZHANG Li LUO Kun FAN Jianren State Key Laboratory of Clean Energy Utilization (Zhejiang University) Hunan Electric Power Design Institute

Based on the heat and mass transfer theory and the characteristics of general-purpose software FLUENT, a three-dimensional numerical simulation platform, composed of lots of user defined functions(UDF), has been developed to simulate the thermal performance of natural draft wet cooling towers(NDWCTs). After validation, this platform is used to analyse thermal performances of a 220m high super large cooling tower designed for inland nuclear plant under different operational conditions. Variations of outlet temperature of the cooling tower caused by changes of water flow rates, inlet water temperatures are investigated. Effects of optimization through non-uniform water distributions on outlet water temperature are discussed, and the influences on the flow field inside the cooling tower are analyzed in detail. It is found that the outlet water temperature will increase as the water flow rate increases, but the air flow rate will decrease. The outlet water temperature will decrease 0.095K and 0.205K, respectively, if two non-uniform water distribution approaches are applied.

关键词： Super Large Natural Draft Wet Cooling Tower three-dimensional Numerical Simulation Thermal Performance Non-uniform Water Distribution

three-dimensional simulation method of multipactor in microwave components for high-power space application

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Chinese Physics B 2014年第4期23卷 686-693页

作者：李韵崔万照张娜王新波王洪广李永东张剑锋 National Key Laboratory of Science and Technology on Space Science China Academy of Space Technology (Xi’an) Key Laboratory of Physical Electronics and Devices of the Ministry of Education Xi’an Jiaotong University State Key Laboratory of Millimeter Waves Southeast University

Based on the particle-in-cell technology and the secondary electron emission theory, a three-dimensional simulation method for multipactor is presented in this paper. By combining the finite difference time domain method and the panicle tracing method, such an algorithm is self-consistent and accurate since the interaction between electromagnetic fields and particles is properly modeled. In the time domain aspect, the generation of multipactor can be easily visualized, which makes it possible to gain a deeper insight into the physical mechanism of this effect. In addition to the classic secondary electron emission model, the measured practical secondary electron yield is used, which increases the accuracy of the algorithm. In order to validate the method, the impedance transformer and ridge waveguide filter are studied. By analyzing the evolution of the secondaries obtained by our method, multipactor thresholds of these components are estimated, which show good agreement with the experimental results. Furthermore, the most sensitive positions where multipactor occurs are determined from the phase focusing phenomenon, which is very meaningful for multipactor analysis and design.

关键词： multipactor numerical method three-dimensional high-power threshold

three-dimensional NUMERICAL SIMULATION OF WAVE SLAMMING ON AN OPEN STRUCTURE

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Journal of Hydrodynamics 2012年第4期24卷 526-534页

作者： DING Zhao-qiang WANG Guo-yu REN Bing State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China

The three-dimensional numerical simulation of wave slamming on an open structure in the splash zone is carried out based upon the Volume Of Fluid （VOF） method. A wave basin is established by solving the continuity equation and the Navier-Stoke equations. The linear wave-maker is placed on the left side of the basin, and the numerical sponge layer and the SRC are placed on the right side of the basin to damp the incident waves. The three-dimensional wave slamming boundary condition is adopted to model waves in contact with and separated from the underside of the structure. The numerical results of wave slamming on a foursquare structure for various parametric cases are verified by the experimental results. Meanwhile, the characteristics of the wave impact forces on the undersides of the rectangular structures with various length-breadth ratios are discussed.

关键词： wave slamming three-dimensional Volume Of Fluid (VOF)

three-dimensional reconstruction of a point immersed in water and application to a single rising bubble

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Particuology 2019年第5期17卷 83-92页

作者： Saiwei Li Luyang Chen Zhiqiang Sun School of Energy Science and Engineering Central South University Changsha 410083 China

The ability to reconstruct an object submerged in water is instrumental in scenarios such as the study of a rising bubble trajectory, and subsequently, its motion and force balance. In this paper, we propose a method that can reconstruct the three-dimensional position of a scene point immersed in water, while taking into account the refraction-induced distortion at the air-water interface between the point and camera. The scene point is captured by two orthogonally placed high-speed cameras, providing a pair of images through which the point's image coordinates are obtained. With pre-calibrated camera matrices, the world coordinates of the point’s position can be correctly calculated using a triangulation method, provided the scene point is in air. However, because of refraction, triangulating the image pairs of the point submerged in water results in erroneous world coordinates. Thus, we propose a method to correct the point's image coordinates to account for refraction induced distortion during reconstruction. The method was first verified by reconstructing the coordinates of square corners on a checkerboard, which produced results that deviated from the real value by 0.18%, as opposed to the 5.15% false enlargement prior to correction. Then, we applied the method to the reconstruction of the three-dimensional trajectories of single rising spherical bubbles, whose results were in favorable agreement with previous studies.

关键词： Underwater visualization three-dimensional reconstruction Refraction Distortion correction

three-dimensional flow field simulation of steady flow in the serrated diffusers and nozzles of valveless micro-pumps

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Journal of Hydrodynamics 2019年第2期31卷 413-420页

作者： Ying-hua Xu Wei-ping Yan Kai-rong Qin Tun Cao School of Energy and Power Engineering Dalian University of TechnologyDalian 116024China School of Optoelectronic Engineering and Instrumentation Science Dalian University of TechnologyDalian 116024China

This paper presents a three-dimensional flow field simulation of the steady flows through diffusers and nozzles with straight or serrated-sided walls to analyze the effect of the channel structure on the flow *** pressure and velocity profiles in the diffusers and the nozzles as well as the net volumetric flow rate are *** simulation demonstrates that the pressure and velocity profiles in the serrated diffuser/nozzles are more complicated than those with the straight-sided wall,while the net steady flow rate with the straight-sided wall increases monotonically with the increase of the pressure difference,the steady flow rate with serrated sided walls increases gradually to reach a maximum and then decreases with the increase of the pressure *** results suggest that the number of the sawteeth plays a significant role in optimizing the design of serrated diffusers and nozzles for improving the transport efficiency of valveless micro-pumps.

关键词： Valveless micro-pump steady flow diffuser and nozzle serrated-sided wall three-dimensional flow field simulation

three-dimensional Urban Thermal Effect across a Large City Cluster during an Extreme Heat Wave:Observational Analysis

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Journal of Meteorological Research 2022年第3期36卷 387-400页

作者： Yue MA Ping LIANG Sue GRIMMOND Xuchao YANG Jun LYU Yihui DING Key Laboratory of Cities’Mitigation and Adaptation to Climate Change in Shanghai Shanghai Regional Climate CenterChina Meteorological AdministrationShanghai 200030China Shanghai Jiading District Meteorological Bureau Shanghai 201800China Department of Meteorology University of ReadingReading RG66ETUnited Kingdom Ocean College Zhejiang UniversityZhoushan 316021China Jiangsu Meteorological Information Center Jiangsu Meteorological BureauNanjing 210008China National Climate Center China Meteorological AdministrationBeijing 100081China

Given extensive and rapid urbanization globally,assessing regional urban thermal effects(UTE)in both canopy and boundary layers under extreme weather/climate conditions is of significant *** population and economic growth in the Yangtze River Delta(YRD)have made it one of the largest city clusters in ***,we explore the three-dimensional(3D)UTE in the YRD using multi-source observations from high-resolution automatic weather stations,radiosondes,and eddy covariance sensors during the record-setting heat wave(HW)of July-August *** is found that the regional canopy layer UTE is up to 0.6-1.2℃,and the nocturnal UTE(0.7-1.6℃)is larger than daytime UTE(0.2-0.5℃)during the *** regional canopy layer UTE is enhanced and expanded northwards,with some rural sites contaminated by the urban influences,especially at *** the boundary layer,the strengthened regional UTE extends vertically to at least 925 hPa(~750 m)during this *** strengthened 3D UTE in the YRD is associated with an enlarged Bowen ratio difference between urban and non-urban *** findings about the 3D UTE are beneficial for better understanding of the thermal environment of large city clusters under HW and for more appropriate adaption and mitigation strategies.

关键词： urban thermal effect three-dimensional Yangtze River Delta heat wave

three-dimensional Flower-like Rutile TiO2 Microsphere Composed of Nanorods： a Potential Material as Light Scattering Layer for DSSCs

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Chemical Research in Chinese Universities 2017年第2期33卷 298-304页

作者： Yan Shi Yulin Yang Guohua Dong Yanxia Jiang Liguo Wei Ting Su Ruiqing Fan MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage School of Chemistry and Chemical Engineering Harbin Institute of Technology Harbin P. R. China College of Chemistry and Chemical Engineering Qiqihar University Qiqihar P. R. China College of Environmental and Chemical Engineering Heilongjiang University of Science and Technology Harbin P. R. China

The low spectrum utilization and the recombination of photo-generated electrons are the main challengesfor improving the performance of dye sensitized solar cells（DSSCs）. In this article, a three-dimensional flower-likeruffle titanittm dioxide（TDF-TiO2） was successfully synthesized via a simple sol-thermal process. X-Ray diffractionpatterns（XRD） and scan electron microscopy（SEM） images exhibit that the TDF-TiO2 are the futile TiO2 microspherecomposed of lots of regular cuboid nanorods. Applying this TDF-TiO2 as light scattering layer on the photoanode ofDSSCs, the devices present an excellent photovoltage performance, yielding a power conversion efficiency（PCE） of7.69%, which can be mainly attributed to the enhanced light utilization and the reduced recombination of pho-to-generated electrons upon a combined analysis of electrochemical impedance spectroscopy（EIS）, open-circuit vol-tage decay（OCVD）, and intensity-modulated photocurrent spectroscopy and intensity-modulated photo voltage spec-troscopy（IMPS/1MVS）, etc. As a conclusion, TDF-TiO2 is a potential material as light scattering layer and opticaltransition medium to improve the performance of DSSCs, and this work further demonstrated that regulating themorphology and particle size of TiO2 is an efficient approach for enhancing the performance of DSSCs by optimizingthe utilization of light and the transporting behaviors of photo-generated electrons.

关键词： Dye sensitized solar cell Photoanode three-dimensional flower-like rutile TiO2 Light scattering layer