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Experimental study on dynamic mechanism of vortex evolution in a turbulent boundary layer of low Reynolds number

Journal of Hydrodynamics 2020年第5期32卷 807-819页

作者： Yan-ang Guo Xiang-rui Dong Xiao-shu Cai Wu Zhou School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Key Laboratory of Multiphase Flow and Heat Transfer in Shanghai Power Engineering Shanghai 200093China

The dynamic mechanism of the vortex generation and evolution process in a fully developed turbulent boundary layer with Reθ=97-194 is experimentally *** this study,a moving single-frame and long-exposure(MSFLE)imaging method and a moving particle image velocimetry/particle tracing velocimetry(M-PIV/PTV)are designed and implemented for measuring the temporal and spatial evolution of vortex cores in both qualitative and quantitative ways,*** the other hand,the Liutex vector,which is a new mathematical definition and identification of the vortex core proposed by Liu’s group,is first applied in the experiment for the structural visualization and quantitative analysis of the local fluid *** results show that an intuitional process of vortex evolution can be clearly observed by tracking the vortex using MSFLE and verify that the roll-up of the shear layer induced by shear instability is the origin of vortex formation in ***,a quantitative investigation in terms of the critical vortex core boundary(size)and its accurate rotation strength is carried out based on the Liutex vector field analysis by M-PIV/*** to statistics of the relation between vortex core size and the rotation strength during the whole process,the physical mechanism of vortex generation and evolution in a turbulent boundary layer of low Reynolds number can be summarized as a four-dominant-state course consisting of the“synchronous linear segment(SL)-absolute enhancement segment(AE)-absolute diffusion segment(AD)-skewing dissipation segment(SD)”.

关键词： Turbulent boundary layer high-and low-speed fluid vortex generation moving single-frame and long-exposure moving particle image velocimetry/particle tracing velocimetry Liutex vector

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Investigation on the Mechanism of Co2 Hydrate Formation by Synergistic Action of Kinetic Promoters

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SSRN 2023年

作者： Liu, Ni Leng, Jing Cui, Mengxue Yang, Liang School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China

CO2 hydrate technology has a promising application in carbon neutralization through carbon capture. In this paper, the effect of different mass concentrations of fullerene C60 and sodium lignosulfonate (SL) on the gas storage performance of CO2 hydrate was investigated. C60 can promote the best results at the concentration of 0.01 wt%. The induction time was 168 minutes, and the gas storage capacity was 56.60 V/V, which is 112.22% higher than that of pure water. This is due to the large specific surface area of C60 nanoparticles, which reduces the surface tension of the solution and increases the gas-liquid mass transfer rate. SL can promote the best results at the concentration of 0.1 wt%. The induction time was 1,908 minutes, and the gas storage capacity was 89.98 V/V, which is 2.37 times higher than that in the pure water system. This is because SL molecules possess abundant functional groups, high chemical reactivity, high elasticity and surface activity. The best compounding pair was in the experimental group of 0.01 wt% C60 with 0.1 wt% SL. The induction time was 60 minutes, and the gas storage capacity was 108.87 V/V. Therefore, both C60 and SL have a positive effect on CO2 hydrate formation. © 2023, The Authors. All rights reserved.

关键词： Carbon dioxide

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Study on the Aerodynamic Characteristics of Vertical Axis Wind Turbines Based on Omnidirectional Guide Grids

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SSRN 2023年

作者： Zhou, Ye Xiandong, Li Hao, Yu Renhao, Ruan School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai200093 China

In order to analyze the influence of the structural parameters of the omnidirectional deflector on the aerodynamic performance of the vertical axis wind turbine, a combination of the inclination angle, relative distance, and thickness of the blade grid was designed to compare the influence of the structural parameters of the omnidirectional deflector on the aerodynamic performance of the vertical axis wind turbine under various tip speed ratio conditions. The results show that the wind power utilization rate and moment coefficient of the wind turbine under the effect of the omnidirectional deflector grille tend to increase and then decrease as the inclination angle increases, and the best effect on the wind turbine aerodynamic performance is achieved when the inclination angle is 0°, the wind turbine moment is greatly increased, and the range of effective operating conditions is expanded. When the inclination angle is 0° at all relative distances, the omnidirectional deflector grid can improve the pressure distribution of wind turbine blades, and the corresponding pneumatic performance improvement increases with the relative distance. When the relative distance is 2.6, the best effect on the wind turbine's aerodynamic performance is achieved. By changing the number of deflector blades and chord length to adjust the grid consistency, the vertical axis wind turbine aerodynamic performance curve under the action of the omnidirectional deflector shifts toward the direction of the large tip speed ratio as the grid consistency increases, and the corresponding wind energy utilization rate and torque coefficient peak are increasing and then decreasing when the chord length is 374mm (grid consistency is 0.267). When the chord length is 374mm (the blade thickness is 0.267), the best effect on the aerodynamic performance of the vertical axis wind turbine is achieved. © 2023, The Authors. All rights reserved.

关键词： Vertical axis wind turbine

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Estimation of particle depth from two defocused images using the Fourier transform

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Particuology 2020年第2期18卷 48-54页

作者： Wu Zhou Xu Luo Benting Chen Yukun Zhang Xiaoshu Cai School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai 200093China

Depth from defocus is one technology for depth *** estimate particle depth information from two defocused images captured simultaneously by two coaxial cameras with different imaging *** images are processed with the Fourier transform to obtain the characteristic parameter(i.e.,the standard deviation of the relative blur kernel of these two defocused images).First,we theoretically analyze the functional relationship between the object depth and the standard deviation or variation of the relative blur ***,we verify the relationship *** analyze the influence of particle size,window size and image noise on the calibration curves using both numerical simulations and *** obtain the depth range and accuracy of this measurement system *** the verification experiments,we use a sample of glass microbeads and the irregularly-shaped dust particles on a microscope *** of these experiments present a suitable depth measurement ***,we apply the measuring system to the depth estimation of drops from a small anti-fogging *** results show that our system and image processing algorithm are robust for different types of particles,facilitating the in-line three-dimensional positioning of particles.

关键词： Depth from two defocused images Fourier transform Standard deviation of relative blur kernel Drops depth measurement Sensitivity and accuracy analysis

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Experimental study on improvement of freeze-drying process for porcine aorta

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DRYING TECHNOLOGY 2022年第2期40卷 401-415页

作者： Gui, Chao Tao, Leren Zhang, Yaqi Univ Shanghai Sci & Technol Sch Energy & Power Engn 516 Jungong Rd Shanghai 200093 Peoples R China Xinxiang Univ Sch Civil Engn & Architecture Xinxiang Henan Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai Peoples R China

Freeze-drying is an effective method for preservation of aortas. In order to maintain the original properties of aortas, the sublimation drying process requires accurate monitoring. In this study, we used a contactless mass measurement device to monitor drying process, porcine aortic segments were divided into four series for freeze-drying, then relevant experiments and calculations were carried out to evaluate the quality of lyophilized samples. The study found that the sublimation process could not be accurately monitored by measured temperature, however, the real-time weighing could do it well, and was suitable to judge the endpoint of primary drying. Meanwhile, the change law of sublimation temperature was obtained by quasi-steady heat transfer equations. The removal ratio of free water during the primary drying greatly affected the properties of lyophilized samples, thorough sublimation had contributed to better performance of products, especially in mechanical properties. In addition, compared with annular aortic segments, the flaky samples had better heat transfer and performed better in histological scanning.

关键词： Freeze-drying dehydration rate sublimation rehydration capacity mechanical properties histological scanning

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Sensitively Detection of Ascorbic Acid in Orange Samples with Ionic Liquid Functionalized Carbon Dots and Lanthanide Complexes

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SSRN 2024年

作者： Li, Ying Xia, Ji-Ji Lu, Jia-Zhen Wang, Zi-Long Wang, Mi-Tang School of Materials and Chemistry University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China

In the food industry, ascorbic acid (AA) is widely used as an antioxidant. However, the concentration of AA is influenced by various factors, including temperature, time, and pH value during food preparation and storage, leading to its instability in content. This makes the accurate detection of AA content particularly important. Precise determination of AA content in food and pharmaceuticals is crucial for ensuring the adequate intake of essential vitamins and maintaining good health. Herein, we have developed a successful preparation method of an imidazole-based ionic liquid functionalized CDs hybrids APM-CDs. A novel photo functional hybrid probe Eu3+@APM-CDs was obtained via an ion-exchange reaction between APM-CDs and lanthanide complex Eu(DPA)3. The obtained hybrid probe was extensively characterized in detail. What’s more, the results show that the FL intensity of Eu3+@APM-CDs has a good linear response to AA concentrations in the range of 0-500 μM (R2 = 0.99), with a detection limit of 80 nM. The fluorescence probe demonstrates good selectivity and sensitivity toward AA and has the potential for significant application in AA detection by simplifying procedures and reducing interference from impurities. © 2024, The Authors. All rights reserved.

关键词： Probes

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Study on Liutex-driven reward for intelligent flow control by dynamic feature-based deep reinforcement learning

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AIP ADVANCES 2025年第5期15卷

作者： Wang, Qi Dong, Xiangrui You, Sunyu Cai, Xiaoshu Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

The issue of flow separation over an airfoil under weak turbulent conditions is addressed and resolved through the deep reinforcement learning (DRL) strategy. To suppress the generation of separation flow and the instability of the vortex shedding alley over an airfoil, a novel reward function named R Liutex, considering the suppression of the rigid rotation intensity and core size of the vortex, is first proposed in this paper. The great potential of this Liutex-driven reward for effective large eddy elimination and aerodynamic optimization is verified in this work. Furthermore, a dynamic feature-based DRL (DF-DRL) framework is redeveloped to markedly enhance the learning efficiency and convergence speed. The combination of the Liutex-driven reward function with the DF-DRL framework results in an exceptional aerodynamic performance, with minimal fluctuations in both drag and lift coefficients, highlighting the potential of this approach for advanced flow control strategies. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International (CC BY-NC-ND) license (https://***/licenses/by-nc-nd/4.0/).

关键词： Deep reinforcement learning

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Mercury transformation and removal in chemical looping combustion of coal: A review

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FUEL 2023年第1期347卷

作者： Liu, Dunyu Wang, Chaoran Fan, Yunpei Liu, Qiuqi Wang, Xudong Xu, Kailong Jin, Jing Ma, Jingjing Ma, Jinchen Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Ningxia Univ Coll Chem & Chem Engn State Key Lab High Efficiency Utilizat Coal & Gree Yinchuan 750021 Ningxia Peoples R China Huazhong Univ Sci & Technol State Key Lab Coal Combust Wuhan 430074 Peoples R China

Chemical looping combustion (CLC) of coal for carbon capture utilization and storage is an effective technology to reduce carbon emission due to smaller energy penalty and inherent low emission of pollutants. However, a large uncertainty exists in mercury emission from both air and fuel reactor for coal-fired chemical looping combustion. This paper attempts to reveal the underlining mechanisms for the transformation of mercury-related species both in combustion and post-combustion process. Mercury in coal, temperature, and water vapor pro-mote the release of mercury in fuel reactor. Oxygen carriers (OCs) promote the conversion of Hg0 to Hg2+ and HgP. Both oxygen release and adsorption ability of reduced OCs contributes to the mercury removal efficiency. HCl is the dominant species for Hg0 oxidation. NO, SO2, CO, and H2 have negative impacts on Hg0 oxidation;while O2 promotes Hg0 oxidation;the influence of H2O on Hg0 oxidation depends on concentration. H2S may promotes Hg0 removal by formation metal sulfides. In the post combustion mercury removal by adsorption and catalytic oxidation process, O2, HCl, NO, and CO2 promote the oxidation of Hg0, whereas SO2, CO, and H2 inhibit the oxidation of Hg0. The impacts of H2S and H2O on Hg0 oxidation depends on their concentrations. Simul-taneous removal of SO2, NO, and Hg0 by green oxidation-based absorption using free radicals or in the compression process have a good prospect due to potential low cost. This work will encourage wider discussion on flue gas treatment possibilities to reduce the cost of future CLC power plant.

关键词： Chemical looping combustion Mercury transformation Oxygen carrier

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Experimental and numerical analysis of the multilayer distributed Joule-Thomson cooler with pillars

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INTERNATIONAL JOURNAL OF ENERGY RESEARCH 2021年第4期45卷 6086-6103页

作者： Geng, Hui Cui, Xiaoyu She, Hailong Chang, Zhihao Univ Shanghai Sci & Technol Sch Energy & Power Engn 516 Jungong Rd Shanghai 200093 Peoples R China Key Lab Multiphase Flow & Heat Transfer Shanghai Shanghai Peoples R China

The conventional Joule-Thomson cooler is not compact in heat exchanger and insufficient in cooling capacity, which is limited in applying integrated electronics. However, microchannels with pillars are effective in increasing the area to volume ratio and enhancing heat transfer through the presence of vortex. Besides, multilayer microchannels are essential to enlarge the mass-flow rate in the cooler. In this study, a multilayer distributed J-T cooler with pillars is investigated. A new mathematical model of the cooler is developed and validated against the experimental data;the relative errors of the temperature and mass-flow rate are both within 5%. Furthermore, the distribution of temperature and pressure in the microchannel is analyzed by the model calculation. Numerical results show that the temperature of the high-pressure fluid decreased slightly under the influence of the heat exchange and distributed J-T effect. When the inlet pressures are 3.00, 4.00 and 5.40 MPa, the cold-end temperatures are 233.0, 185.8 and 161.2 K, respectively, with the cooling capacity reaching 2.25, 3.40 and 3.87 W, respectively. In addition, the influences of the axial heat conduction and heat leakage on the cooling performance are analyzed by using the models. The temperature rise of the cold end increases by 6.8 and 6.2 K at 5.40 MPa, respectively, considering the above two factors. The simulation model provides a useful tool for the J-T cooler.

关键词： cooling capacity heat transfer J‐ T cooler microchannel pressure drop

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Entropy Generation of R513A Condensation flow Inside the Horizontal Microfin Tubes

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JOURNAL OF THERMAL SCIENCE AND engineering APPLICATIONS 2024年第7期16卷 071002-071002页

作者： Zhang, Suhan Tao, Leren Huang, Lihao Jin, Cheng Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

It is widely acknowledged that the pressure drop increases with enhanced heat transfer in heat exchanger tubes, and entropy generation analysis serves as an effective method to comprehensively evaluate heat transfer and pressure drops. This paper conducts experimental research on in-tube condensation heat transfer using refrigerants R513A and R134a in six test tubes, comprising both smooth and microfin tubes with outer diameters of 9.52 mm and 12.7 mm, respectively. The microfin tubes are available in two types, with 60 and 65 fins, respectively, and a helix angle of 18 deg. The experimental conditions included mass fluxes of 50-250 kg/m(2) s and condensation temperatures of 35 degrees C, 38 degrees C, and 40 degrees C. The findings indicate that replacing R134a with R513A is feasible. The 9.52 mm tube exhibits superior overall heat transfer performance compared to the 12.7 mm tube, and the 60-fin microfin tube outperforms the 65-fin tube in terms of heat transfer efficiency. This suggests that microfin tubes with smaller diameters and an optimal number of fins are more effective in enhancing condensation heat transfer performance. Graphical Abstract Figure

关键词： R513A and R134a microfin tube condensation heat transfer entropy generation minimization analysis thermophysical properties

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