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SSRN 2022年

作者： Zhao, P.H. Li, K. Zhang, H. Li, Dong Chen, B. Zheng, Y.P. Li, W.P. Wang, G.X. Fan, L.H. Yao, L. State Key Laboratory of Multiphase Flow in Power Engineering Xi 'an Jiaotong University Shaanxi Xi'An710049 China Department of Ophthalmology The Second Affiliated Hospital of Xi 'an Jiaotong University Shaanxi Xi'An710004 China The First Affiliated Hospital of Xi'an Joao Tong University Shaanxi Xi'An710061 China Department of Mechanical Engineering The University of Akron Akron United States

The photo-thermal effects of laser on tissue is widely used in ophthalmology to treat retinal diseases. By adjusting the pulse duration from nano to tens of seconds, the multi-scale retinal lesion from micro to millimeter size can be thermally targeted. Large scale difference among the target lesions brought extra challenge for retinal laser surgery modeling. In this study, we developed a coupled whole eye model for retinal laser surgery. In the model, Penens bioheat transfer equation was adapted for the whole eye temperature modeling. Simultaneously, we treat the fundus as a multi-layered porous medium made of a tissue matrix buried with highly-absorbing chromophores (melanin or blood). Two-temperature equations, one for the chromophore and the other for the surrounding tissue, will be developed based on the local thermal non-equilibrium theory of porous media. The Pennes model and the two-temperature model was coupled together to calculated the thermal responses of eye during several laser retinal surgery process with pulse duration from nano to tens of seconds. The simulation results proved our model is capable of modeling laser retinal surgery process in different time scale. Furthermore, the present coupled model was applied in a real fundus anatomy from a patient with diabetic retinopathy to illustrate its feasibility in customized laser protocol planning. © 2022, The Authors. All rights reserved.

关键词： Ophthalmology

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Experimental investigation on characteristic parameters of air-water slug flow in a vertical tube

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CHEMICAL engineering SCIENCE 2021年 246卷 116895-116895页

作者： Wang, Teng Gui, Miao Zhang, Tao Bi, Qincheng Zhao, Jinle Liu, Zhaohui Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Sch Nucl Sci & Technol 28 West Xian Ning Rd Xian 710049 Shaanxi Peoples R China

Y Experimental investigation on vertical upward co-current air-water slug flow was carried out at atmospheric pressure, employing optical probes and high-speed photography. Experiments were performed with water superficial velocity ranging from 0.089 to 1.52 m/s and gas superficial velocity ranging from 0.049 to 1.06 m/s in a polymethyl methacrylate tube of 15 mm inner diameter. Taking advantage of the time-domain characteristics of optical probes, slug flow has been disposed as a combination of Taylor bubbles and liquid slugs. Slug flow identification, characteristic parameters measurement and analysis were conducted in the present study. Firstly, combined with subjective observation, a developed methodology of flow pattern identification based on machine learning was proposed, with emphasis on slug flow. Results showed that the proposed method exhibited an outstanding advantage in the identification in the flow pattern transition region. More importantly, extensive data on local void fraction in liquid slugs (alpha(l, LS)) and in continuous slug units (alpha(l)), gas-phase velocity of Taylor bubble (U-TB) and liquid slug (U-LS), length of Taylor bubble (L-TB) and liquid slug (L-LS), were obtained. Through comprehensive analysis, it was found that turbulence intensity and flow pattern transitions were the dominant factors in affecting the characteristics of slug flow parameters. (C) 2021 Elsevier Ltd. All rights reserved.

关键词： Slug flow Optical probe Void fraction Bubble velocity Taylor bubble Liquid slug

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Construction of a Transient Multi-Physics Model of Solid Oxide Fuel Cell Fed by Biomass Syngas Considering the Carbon Deposition and Temperature Effect

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SSRN 2022年

作者： Zhu, Pengfei Yao, Jing Wu, Zhen Huang, Si-Min Abu Mansor, Mohd Radzi Yang, Fusheng Zhang, Zaoxiao School of Chemical Engineering and Technology Xi’an Jiaotong University Xi’an710049 China Guangdong Provincial Key Laboratory of Distributed Energy Systems Guangdong Provincial Engineering Research Center of Distributed Energy Systems Dongguan University of Technology Dongguan523808 China Department of Mechanical and Manufacturing Engineering University Kebangsaan Malaysia Selangor43600 Malaysia State Key Laboratory of Multiphase Flow for Power Engineering Xi’an Jiaotong University Xi’an710049 China

Carbon deposition is a thorny issue for the SOFC fueled by low carbon hydrocarbons such as biomass syngas. Moreover, long-term large temperature gradients would reduce SOFC durability. Regarding these two issues, a two dimensional transient multi-physical model considering carbon deposition and temperature effect is developed for SOFC in this work. Typically due to the carbon deposition, the SOFC anode porosity decreases from 0.5 to 0.26, and the reaction activity decreases from 1.0 to about 0.45 after running 140 day. Accordingly, the current density decreases by 1.6 % at t =42 d and 6% at t =140 d, which indicates the damage of SOFC durability compared to the durability target (1%/1000h) of commercial SOFC. The maximum temperature difference of the cell is predicted to be about 106 o C. It was found that the carbon deposition and large temperature gradient are closely related to the operating parameters. With the increase of operating voltage from 0.4 V to 0.8 V, the porosity and reaction activity respectively increase by 50% and 55%, and the maximum temperature difference is reduced from 150 o C to 16 o C after running 140 day. The increase of the inlet temperature could improve the overall temperature and decrease the porosity. Besides, the reduction in the ratio of CH 4 to H 2 O helps to suppress carbon deposition, thus to improving the performance. © 2022, The Authors. All rights reserved.

关键词： Solid oxide fuel cells (SOFC)

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UNSTEADY SIMULATION ON flow CHARACTERISTICS OF STEAM JET CONDENSED INTO SUBCOOLED WATER

UNSTEADY SIMULATION ON FLOW CHARACTERISTICS OF STEAM JET CON...

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ASME power Conference 2019

作者： Song, Shilin Chong, Daotong Zhao, Quanbin Chen, Weixiong Yan, Junjie Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Shaanxi Peoples R China

ISBN: (纸本)9780791859100

Steam jet condensation through sonic nozzle in quiescent subcooled water pool is important for the safety of nuclear reactor system. In this study, the dynamic process of stable condensation jet steam plume is obtained by numerical simulation method. The simulation results are in good agreement with the experimental results. The flow field results indicate that two typical fluctuation regimes exist in the dynamic process of steam plume. Simultaneous analysis of pressure and flow field indicates that two fluctuation regimes produce different pressure pulses. When the detachment phenomenon occurs during the fluctuation of the steam plume, a pressure pulse which value is clearly greater than 220 kPa is generated. When the plume sharply contracts without obvious detachment phenomenon during the fluctuation process, a pressure pulse which value is almost lower than 120 kPa is generated.

关键词： Numerical method Direct contact condensation Steam jet Dynamic characteristic

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Measurements on flame structure of bluff body and swirl stabilized premixed flames close to blow-off

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 2019年 104卷 15-25页

作者： Zhang, Weijie Wang, Jinhua Lin, Wenjun Guo, Shilong Zhang, Meng Li, Guohua Ye, Jingfeng Huang, Zuohua Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Northwest Inst Nucl Technol State Key Lab Laser Interact Matter Xian 710024 Shaanxi Peoples R China

The structure of unconfined lean premixed CH4/air flames stabilized with an axisymmetric bluff-body and a swirler was studied for conditions far from and close to blow-off. Blow-off was approached by gradually reducing the equivalence ratio while keeping bulk velocity constant at about 20m/s. The objective is to examine the critical regions of flame structure that initiate and develop to blow-off for relatively short flames. OH-PLIF and CH*. chemiluminescence were adopted to capture the instantaneous flame front and time-averaged flame structure. Statistics of the flame root-lift-off, flame front curvature and flame surface density (FSD) were obtained. Local burning velocity was estimated based on the FSD field. The burning intensity was also demonstrated with CH* chemiluminescence. As blow-off was approaching, the flame structure was seen to be more compacted. Lift-off at the flame roots was observed to be more frequent and the lift-off height was increased at leaner conditions. The local burning intensity was significantly decreased at upstream stages including the flame root close to blow-off. The wrinkling ratio was growing obviously at downstream, with finer flame structure observed through the short and intensive probability density function (PDF) of curvatures. The enhanced wrinkling by the recirculating flow at downstream is assumed to be favorable for the flame stabilization prior to the final blow-off. This indicates minor effects of downstream on blow-off. Comparatively, upstream of the flame including the main shear layer and the flame root is more unstable and unfavorable for ignition and flame stabilization, which dominantly promotes the blow-off. The measurements in present study are useful for model validation in terms of flame structures, and also significant for exploring the blow-off behavior of shorter flames as proposed in previous studies.

关键词： Lean premixed combustion Blow-off Flame structure Bluff-body and swirl burner OH-PLIF

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Rationally Engineered Reox-Cuso4/Tio2 Catalyst with Superior Nh3-Sco Efficiency and Remarkably Boosted So2 Tolerance: Synergy of Acid Sites and Surface Adsorbed Oxygen

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SSRN 2022年

作者： Yu, Yanke Wei, Desheng Tong, Zhaojian Wang, Jinxiu Chen, Jinsheng He, Chi Department of Environmental Science and Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China Center for Excellence in Regional Atmospheric Environment Institute of Urban Environment Chinese Academy of Sciences Xiamen361021 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi Xi'An710049 China National Engineering Laboratory for VOCs Pollution Control Material & Technology University of Chinese Academy of Sciences Beijing101408 China

Ammonia (NH3) is a critical component causing environmental problems like haze and water pollution. Selective catalytic oxidation of ammonia (NH3-SCO) to N2 and H2O is a promising method to abate NH3 emission. However, inferior SO2 tolerance is still a tremendous challenge to be conquered for present NH3-SCO catalysts regarding practical applications. Application of materials which was difficult to be sulfated by SO2 should be an effective pathway to solve this problem. Here, a ReOx-CuSO4/TiO2 catalyst which coupled the advantages of ReOx (Rhenium oxides, supplying highly active adsorbed surface oxygen for enhancing NH3-SCO reaction) and CuSO4 (providing Brønsted acid sites for inhibiting the formation of N2O) was rationally fabricated. Results indicated that ReOx-CuSO4/TiO2 catalyst performed excellent catalytic performance in NH3-SCO with almost 100% of NH3 oxidized at 300 °C (N2 selectivity as high as 96%). Crucially, the composite catalyst exhibited incredible activity and stability under harsh reaction conditions toward SO2 (600 ppm) and H2O (4.0 vol.%) owing to the superior inhibition capability for SO2 adsorption. In situ DRIFTS, in situ Raman and in situ XPS demonstrated that the NH3-SCO reaction over ReOx-CuSO4/TiO2 catalyst mainly obeyed a N2H4 reaction mechanism and oxidation-reduction circle between Re7+ and Re6+ played a vital role. In addition, SO2 would not affect this reaction mechanism on ReOx-CuSO4/TiO2 catalyst. The knowledge and understanding reported could provide critical insights for the design and optimization of efficient materials for industrial NH3 oxidative elimination. © 2022, The Authors. All rights reserved.

关键词： Ammonia

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Design and performance analysis of compressor and turbine in supercritical CO2 power cycle based on system-component coupled optimization

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ENERGY CONVERSION AND MANAGEMENT 2020年 221卷 113179-113179页

作者： Wang, Jiangfeng Guo, Yumin Zhou, Kehan Xia, Jiaxi Li, Yan Zhao, Pan Dai, Yiping Xi An Jiao Tong Univ Shaanxi Engn Lab Turbomachinery & Power Equipment State Key Lab Multiphase Flow Power Engn Inst TurbomachinerySch Energy & Power Engn Xian 710049 Peoples R China

Supercritical CO2 (S-CO2) power cycle has been widely applied in the field of nuclear energy, solar energy and waste heat recovery because of its high efficiency, compact structure and suitability for various heat sources. Compressor and turbine are the key components of the S-CO2 power cycle which significantly affect the cycle performance. Therefore, it is of great necessity to carry out the cycle optimization design and key components performance analysis. In this paper, a novel system-component coupled optimization method of S-CO2 power cycle, which fully considers the performance of compressor, turbine and the S-CO2 power cycle performance, is proposed for improving the accuracy of optimization design results and guarantee a good match between the optimal thermodynamic parameters of S-CO2 power cycle and the performance of key components. The system-component coupled optimization method is implemented by genetic algorithm based on the one-dimensional model of the SCO2 centrifugal compressor and S-CO2 radial inflow turbine to obtain the accurate optimal cycle thermodynamic parameters and the key components design parameters. Using the obtained design parameters of S-CO2 centrifugal compressor and S-CO2 radial inflow turbine, three-dimensional modeling and CFD simulation of S-CO2 centrifugal compressor and S-CO2 radial inflow turbine are implemented. The results show that using system component coupled optimization method can evaluate the cycle performance more reasonably and accurately. The optimized cycle thermal efficiency and the cycle net power output are 19.47% and 987.3 kW, respectively. The optimized turbine efficiency and compressor efficiency are 82.57% and 81.25%, respectively. Unsteady CFD simulation results show that the turbine total-to-total efficiency obtained by steady computation is 0.83% higher than the unsteady time-averaged value obtained by unsteady computation. The relative errors of one-dimensional design results and three-dimensional simu

关键词： Supercritical CO2 power cycle System-component coupled optimization Compressor design Turbine design Unsteady simulation

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Void fraction measurement of stratified gas-liquid flow based on multi-wire capacitance probe

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EXPERIMENTAL THERMAL AND FLUID SCIENCE 2019年 102卷 61-73页

作者： He, Denghui Chen, Senlin Bai, Bofeng Xian Univ Technol State Key Lab Ecohydraul Northwest Arid Reg Xian 710048 Shaanxi Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

The void fraction of stratified gas-liquid flow is crucial to determine mixture density, calculate pressure gradient, obtain phase flow rate, analyze flow structure and monitor flow processes. The measurement and prediction of void fraction is of particular interest in many industrial processes. The objective of this paper is to develop a new method to accurately measure the void fraction in the stratified gas-liquid flow. A measurement device named multi-wire capacitance probe which is based on the single-wire capacitance probe is developed. The device can obtain the average void fraction as well as the local void fraction by measuring the water layer height at different circumferential positions of the pipe. We analyze the water layer height and its variations with time at different circumferential positions under different superficial gas and liquid velocity. We also discuss the local void fraction at different circumferential position and the average void fraction of the circular cross section by measuring the water layer height. Comparisons of ten existing prediction correlations using the measured void fraction are made. The correlation of Annand-Massina is recommended to predict the void fraction of stratified gas-liquid flow. The relative error of the void fraction predicted by this correlation is within +/- 3.0% under the 95.65% confidence level.

关键词： Stratified gas-liquid flow Water layer height Void fraction Capacitance probe

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Study on a high-speed oil-free pump with fluid hydrodynamic lubrication

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ADVANCES IN MECHANICAL engineering 2020年第7期12卷

作者： Fang, Xufeng Hou, Yu Cai, Yijie Chen, Liang Lai, Tianwei Chen, Shuangtao Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

A novel centrifugal pump with axial directional inlet and outlet flow was presented. The system fluid was employed as the lubricant for the hydrodynamic bearings by which the pump can operate at the maximum speed of 8100 r/min without oil lubrication or rigid support. The performance curves related to the efficiency, head, and volume flow rate were obtained via a water cycle test rig. The efficiency at best efficiency point reached 36.14% with a volume flow rate of 4.13 m(3)/h and a head of 27.34 m at 7800 r/min. The maximum head reached 37.28 m, with a volume flow rate of 0.568 m(3)/h at 7800 r/min. The maximum volume flow rate of 6.05 m(3)/h was obtained with a head of 19.45 m at 8100 r/min. Then, the three-dimension computational fluid dynamics model with Reynolds-averaged Navier-Stokes equations and shear stress transportk-omega turbulence model for the pump and bearings was set up individually. The numerical results agreed well with the experimental data.

关键词： High-speed pump small centrifugal pump fluid hydrodynamic lubrication pump head

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Effects of physical structure of high heating-rate chars on combustion characteristics

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FUEL 2020年第0期266卷 117059-000页

作者： Liu, Siqi Niu, Yanqing Wen, Liping Kang, Yaqian Wang, Denghui Hui, Shi'en Xi An Jiao Tong Univ Sch Energy & Power Engn Dept Thermal Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

The combustion performance of high heating-rate chars is observably affected by the evolution of its physical structure during devolatilization. An effort has been devoted to building understandable relationships between the heating rates of different rank coals, char structure and subsequently detailed combustion characteristics. In this work, the physical structure parameters (internal surface area, porosity, and swelling ratio) of bituminous coals and lignites are qualitatively summarized as a function of heating rates ( > 10(4) K/s). Meanwhile, the physical structure effects on char combustion characteristics are investigated separately by using the self-developed kinetics model, where the transient char properties, ash distribution (ash film, ash dilution, and ash vaporization) and char combustion performances are taken into account. The relative importance of the three structure parameters on char burnout is also performed. The internal surface area of high heating-rate chars exerts positive effects on combustion with higher burning temperature and shorter burnout time, whereas the swelling ratio and porosity exert complex effects. The combustion rate initially increases then goes down with char conversion, owing to the integrated effects of formation and destruction of internal surface area. The importance of physical structure parameters on char combustion follows the order: internal surface area > swelling ratio > porosity. These results provide in-depth insight into the effects of physical structure during char combustion and suggest higher heating rates are favorable in industrial boiler applications.

关键词： Char combustion Internal surface area Swelling ratio Porosity Heating rates

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