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Numerical simulation of the bubble dynamics in a bifurcated micro-channel using the lattice Boltzmann method

JOURNAL OF APPLIED PHYSICS 2019年第3期126卷

作者： Lou, Qin Li, Tao Yang, Mo Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China

The dynamics behavior of a bubble passing through a bifurcated microchannel is studied numerically by using the lattice Boltzmann model. The effects of channel wettability, the viscosity ratio, the capillary number (Ca), the initial bubble size, and the flow flux ratio on the interface dynamic behavior, breakup mechanism, and residual mass of the bubble through the bifurcated microchannel are studied systematically. The simulation result indicates that these factors have significant influence on the bubble motion behavior. The bubble splits into two sub-bubbles and flow out of the channel completely when the channel surface is hydrophilic. However, some mass residuals of the bubble are observed when the channel surface is hydrophobic and the residual mass increases with the contact angle. On the other hand, as the viscous ratio of gas-liquid increases, the bubble is more likely to break up and to flow out of the channel. In addition, for the case of low capillary number and small bubble size, the bubble cannot break up, so it finally strands in the main channel. Besides, as capillary number increases, the flow flux ratio required for the bubble to flow out of subchannels increases. Eventually, we establish the relation for the critical flow flux ratio Qc as Qc =0.604 e 13.44 C a and Qc = 1.985 e 5.53 C a to describe whether the bubble breaks up or not for different bubble radii.

关键词： Microchannels

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Facile synthesis of Au nanoparticles with different shapes in a soluble starch-hydroquinone system and their SERS activity

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MATERIALS LETTERS 2019年 255卷

作者： Sun, Li Zhu, Jiacheng Zhang, Hua Dou, Binlin Su, Wenxian Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Jun Gong Rd 516 Shanghai 200093 Peoples R China

A simple soluble starch-hydroquinone system was explored, in which flower-like and star-like gold nanoparticles (Au NPs) could be individually synthesized only by adjusting the injection rate of the precursor solution. Meanwhile, their size could be easily tuned just by changing the molar ratio of Au3+ ions and Au seeds in the precursor solution. As-prepared samples were proved to be polycrystalline, pure and stable Au NPs by means of various characterization techniques. Clearly, the novel and facile method to control the shape (morphology and size) can provide a unique perspective for the shape control of other metal NPs. In addition, obtained Au NPs showed distinct shape-determined surface-enhanced Raman scattering (SERS) activity towards Rhodamine 6G molecules, implying their potential for applications in SERS-based detections and analysis. (C) 2019 Elsevier B.V. All rights reserved.

关键词： Gold Nanoparticles Shape Controllable synthesis Raman

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Numerical simulation on the forced oscillation of rigid riser with helical strakes in different section shapes

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OCEAN engineering 2019年 190卷

作者： Liu, Qingsong Hao, Winxing Li, Chun Miao, Weipao Ding Qinwei Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China

In order to study the helical strakes' suppression effects on the vibration riser, triangle and circular sections helical strakes are proposed. With the technology of dynamic mesh, forced oscillation in steady flow of the riser with helical strakes in different cross-section shapes at low Reynolds number are numerically simulated. The analysis is focused on the lock-in range, as well as the force status and trailing vortex structure under different values of amplitude (A) and oscillation frequency (f(e)), and draw comparisons to the bare riser's results. Research shows the lock-in range will increase with the increase of amplitude ratio (A/D), the riser with all three different shaped helical strakes have larger lock-in range than bare riser. Before entering into the lock-in region, riser with different shaped helical strakes all have good effects on suppressing the vibrations of riser. Within and after lock-in region, riser with triangle and circular sections helical strakes have smaller lift force than that with rectangular section, which reduced lift coefficient by 65.83% and 83.53%. The trailing vortex structures of the riser with helical strakes are in strength three-dimensional character. Inside the lock-in region, riser with triangle and circular sections have better suppression effect than that with rectangular section. Outside the lock-in region, riser with triangle section helical strakes has the best vortex suppression effect, of which the influence on the flow field is greatest and the vortex-induced force is least.

关键词： Helical strakes Forced oscillation Lock-in Vortex-induced vibrations Suppression

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Numerical simulation on the thermal performance enhancement of energy storage tank with phase change materials

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JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY 2019年第2期14卷

作者： Tian, Yang Zhao, Ming Univ Shanghai Sci & Technol Coll Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China

The model of the energy storage tank based on multiple tubes with phase change material was established. The influence of the tube circle diameter and the inner annulus temperature on the heat storage performance of the tube bundle in the concentric circle was studied by numerical simulation. The results show that the increase of the tube circle diameter (Phi) can significantly improve the heat storage efficiency, and the increase in inner wall temperature (T-w) can make the heat storage time significantly shorter, but with the tube circle diameter (F) increases, the effect of T-w on shortening the heat storage time is gradually weakened. In addition, the dimensionless criterion equation of the liquid fraction function (f) at different tube circle diameters is presented too. Furthermore, based on the variation of the mean Nu with Fo, the heat transfer mechanism of the melting process of the PCM can be divided into four stages: (1) heat conduction dominates stage;(2) natural convection dominates stage;(3) natural convection begins to transform into heat conduction stage;and (4) heat conduction dominates again.

关键词： Numerical simulation Latent thermal energy storage Tube circle Wall temperature Fitting

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Performance analysis of a novel household water purification system based on humidification-dehumidification principle

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DESALINATION 2019年 469卷

作者： Li, Kun Wu, Weidong Hu, Kun Wang, Li Hua, Ruoqiu Univ Shanghai Sci & Technol Sch Energy & Power Engnr Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China

In order to avoid frequent cleaning and replacement of filters in the household membrane filtration water purifiers, a novel household water purification system based on the Humidification-Dehumidification (HDH) principle was proposed in this work. A heat pump (HP) unit was utilized in the system for both heating and cooling the closed circulating air. Experimental investigation was conducted by simulating annual working conditions of different water inlet temperatures (5 to 25 degrees C). The performance parameters including system operating conditions, power consumption, water production rate and pure water production per unit energy consumption were analyzed. The results showed that the system performance parameters had a close relationship with the water inlet temperature. The higher water inlet temperature would lead to larger power consumption but greater pure water production rate with a maximum of 692 g/h. The pure water production per unit energy consumption firstly rose and then declined with decreasing the water inlet temperature and reached a maximum of 1996.5 g/(kWh) at 15 degrees C. The pure water production rate of this system was not less than 580 g/h, which could meet the needs of general household drinking water, and the removal rate of the total dissolved solids (TDS) was up to 97%.

关键词： Humidification-Dehumidification (HDH) heat pump (HP) Pure water preparation Household Performance analysis

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Thermodynamic and safety analysis for hydrogen production in a supercritical water gasification system of coal by multi-oxidizers distribution

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Energy 2025年 331卷

作者： Kui Luo Runqiu Dong Xujun Li Zhiyong Peng Libo Lu Jialing Xu Hui Jin Liejin Guo State Key Laboratory of Multiphase Flow in Power Engineering (SKLMF) Xi'an Jiaotong University NO.28 Xianning West Road Xi'an 710049 Shaanxi Province China Dongfang Steam Turbine Co. Ltd. Deyang 618000 China Jiangxi Provincial Key Laboratory of Particle Technology Jiangxi University of Science and Technology Ganzhou 341000 China School of Smart Energy Shanghai Jiao Tong University Shanghai 201100 China

Coal supercritical water gasification (SCWG) for hydrogen production technology is highly prospective due to the clean and efficient treatment process. A single oxidation reactor heating method is usually used in existing work limiting the efficient and stable operation of the system due to high component temperatures. This paper proposed the heat supply strategy of multi-oxidation reactor and heat exchanger layout to improve the system performance for the realization of reasonable matching of material flow and energy flow in each stage of the system. The improved system reduced the maximum temperature of the oxidation reactor from 1550 °C to 850 °C, and the system exergy efficiency and H 2 yield reached 49.30 % and 101 kg/h (at the mass ratio of coal to water of 1:10), respectively. The exergy flow results showed that the improved system exergy loss was concentrated in the oxidation reactor (34.00 %) heat exchanger (28.86 %), cooler (19.07 %), and gasification reactor (9.70 %). Exergy efficiency increased as the mass ratio of coal to water increased to the maximum exergy efficiency of 53.50 %. As the temperature increased from 600 °C to 675 °C, the exergy efficiency decreased from 53.10 % to 48.70 %. System adjustability analysis showed that the system can be stabilized over a 40 %–100 % range of feed fluctuations. This work may provide an optimization strategy for efficient operation and dynamic safety regulation of H 2 production by SCWG technology.

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Macro assessment of microalgae-based CO2 sequestration: Environmental and energy effects

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ALGAL RESEARCH-BIOMASS BIOFUELS AND BIOPRODUCTS 2020年 51卷

作者： Zhao, Bingtao Su, Yaxin Univ Shanghai Sci & Technol Sch Energy & Power Engn 516 Jungong Rd Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer 516 Jungong Rd Shanghai 200093 Peoples R China Donghua Univ Sch Environm Sci & Engn 2999 North Renmin Rd Shanghai 201620 Peoples R China

Microalgae are the most important types of bioenergy-producing and environmentally friendly media used in carbon sequestration, but the macro performance in carbon emission reduction has not yet been understood accurately. To assess the performance and the enviro-energy effect of microalgae-based CO2 sequestration, a comprehensive quadric surface-based logistic model was proposed to characterize the specific production rate of microalgae cultivated under varying key physicochemical factors, including input CO(2 )concentration, N-source concentration, P-source concentration, light intensity, and culture temperature. The effects of these factors were addressed based on the proposed model. The results indicate that the quadric surface-based logistic model predicts the specific production rate more accurately and effectively (R-2 = 0.9509) than the conventional multifactors Monod-Droop model. It enhances the generalization performance by including more influencing factors, considering the independent and interactive effects, and avoiding the possibility of negative values that occur in regular response surface methodology. Furthermore, the performances of microalgal-biomass yields and CO2 sequestration were determined. It is suggested that, theoretically, a maximum of 2.35 GtCO(2) can be sequestrated in 100,000 km(2) culture area, accounting for 8.01-5.31% of global CO2 emission reductions in 2020. On average, annual 0.5393 GtCO(2) sequestration and 324.33 million tons of microalgal-biomass yields would be benefited when using 53,000 km(2) culture area, even though the high economic performance for the microalgal-diesel conversion is challenging to achieve. Microalgae show a great potential in environmentally friendly CO2 mitigation by converting both atmospheric and industrial CO2 into biomass and bioenergy.

关键词： Microalgae Carbon dioxide sequestration Specific production rate Quadric surface-based logistic modeling Environmental and energy effects

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Numerical and experimental investigation into the dynamic response of a floating wind turbine spar array platform

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JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY 2018年第3期32卷 1105-1116页

作者： Ding, Qinwei Li, Chun Yu, Nanting Hao, Wenxing Ji, Jie Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai Peoples R China Univ Plymouth Sch Engn Plymouth Devon England

The station keeping ability of a platform is the most fundamental guarantee to securing the dynamic stability of a Floating offshore wind turbine (FOWT) when being subjected to complex marine environment. These are usually evaluated in terms of rigid body dynamic response of a floating platform which supports whole FOWT. To investigate the dynamic response of array of FOWT, we put forward the concept of a large FOWT farm which consists of nine spar-type wind turbine array and meanwhile shares mooring line system by connecting those FOWT to one another. The whole FOWT is established based on OC3-Hywind spar buoy platform with NREL 5MW wind turbine. Considering effects of wind, wave and current loads, the dynamic response of the proposed FOWT was conducted based on FEM software ANSYS AQWA under both operational condition and survival condition. Besides, comparisons of dynamic response between the original single FOWT and the proposed FOWT farm were also made. Several interesting conclusions were gained through the investigation. For the original single FOWT, RAO in surge, heave and pitch are concentrated in low frequency, while the peak value of frequency is about 0.2 rad/s. In addition, FOWT (P1, P3, P7 and P9) located on the four vertices of 3x3 have higher sway motion which range from about -0.15 m similar to 0.15 m, while sway motion of the rest can be neglected. With the worsening of environmental condition, surge motion of the original single FOWT increases significantly, while it's not significant for the proposed FOWT farm. At the same time, statistic values of pitch motion of the proposed FOWT farm are quite close to those of the original single FOWT. While, under the survival condition, range of pitch motion of the proposed FOWT farm is significantly smaller than that of the original single FOWT. In all, the results verify the effectiveness of the proposed FOWT farm.

关键词： Floating offshore wind turbine (FOWT) Spar Motion Stability AQWA

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Research on a high-accuracy dynamic test method of the rotor temperature field of an explosion-proof motor

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HIGH TEMPERATURES-HIGH PRESSURES 2020年第5-6期49卷 397-409页

作者： Zhao, Qiang Yuan, Yichao Guo, Junjie Tang, Chuansheng Wu, Xuandong Univ Shanghai Sci & Technol Sch Energy & Power Engn Jungong Rd 516 Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Jungong Rd 516 Shanghai 200093 Peoples R China Wolong Elect Nanyang Explos Protect Grp Co LTD Zhongjing Rd 22 Nanyang 473000 Peoples R China Nanyang Inst Technol Sch Mech & Automot Engn Changjiang Rd 80 Nanyang 473004 Peoples R China

To achieve high-accuracy dynamic rotor temperature measurement of an explosion-proof motor during operation, a novel measurement method with a new-type FBG (Fiber Bragg Grating) sensor, is proposed in this paper. First, a new kind of FBG temperature sensors which could be employed in the narrow and small spaces of a motor's air-gap with microsize sealing was developed. Experiments have shown that the designed sensor has a linearity of 0.999, and a repeatability of greater than 274.5 K within the range of 323 K-443 K. Second, a rotor temperature test system with designed sensor was built;the test results showed that the error between the test results and simulation results was less than 8%, which verified the feasibility and validity of the presented method. Furthermore, introducing an all-optical signal into the motor's measurement field, this method was characterized by good fitness, immunity to electromagnetic interference, good explosion-proof performance, high accuracy, dynamic measurement, etc. Therefore, this method could be widely applied to the motor measurement field.

关键词： Explosion-proof motor Temperature field Dynamic test Rotor temperature

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Investigation on aerodynamic performance of horizontal axis wind turbine by setting micro-cylinder in front of the blade leading edge

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ENERGY 2018年 143卷 1107-1124页

作者： Wang, Ying Li, Gaohui Shen, Sheng Huang, Diangui Zheng, Zhongquan Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Univ Kansas Aerosp Engn Dept Lawrence KS 66045 USA

For NREL Phase VI horizontal axis wind turbine, a flow control method to suppress the flow separation by setting micro-cylinder in front of the blade leading edge is proposed, and the corresponding numerical simulation analysis for the aerodynamic performance of wind turbine is conducted. Firstly, the results predicted by simulation are confirmed experimentally. Under the same operating condition, the simulation and experimental results of low-speed shaft torque are compared, along with results from other studies. It can be found that the simulation results can accurately reflect the basic physical characteristics of flow field for NREL Phase VI wind turbine. Secondly, the influence of different diameters and positions of micro-cylinders on aerodynamic performance of wind turbine is discussed. Numerical results suggest that under different stall conditions, setting appropriate micro-cylinders in front of the blade leading edge can effectively suppress flow separation on wind turbine blades without increasing the load of wind turbine. Moreover, under different wind speeds, micro-cylinders with different diameters and positions have various impacts on aerodynamic performance of wind turbine. Through numerical calculation, the blade torque can maximally have an increase of 273% by setting a micro-cylinder with proper diameter and position in front of the blade leading edge. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Horizontal axis wind turbine flow separation Aerodynamic performance Micro-cylinder

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