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12th Asia-Pacific Conference on Combustion, ASPACC 2019

作者： Liu, Yang Tang, Chenglong Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

The purpose of this work is to investigate the effect of ethanol blending into methylcyclohexane during the ignition at low temperatures. The ignition delay times of the binary fuels with ethanol blending ratio varied from 0% to 100% at = 1.0, Pc = 20 bar, Tc = 680 - 890 K were measured with the rapid compression machine, and the mechanism of Bissoonauth et al. (Proc Combust Inst 2018) well predicts the experimental results. Based on the high quality of the model, the effects of ethanol blending on the pressure and heat release are studied. Both of the maximum pressure and the heat release during the ignition decrease with the ethanol blending ratio increases. The interaction of MCH and ethanol happens in the competition of active radicals like OH, and MCH dominates the ignition process as it occupies about two thirds of the OH to form the fuel radical. © Asia-Pacific Conference on Combustion, ASPACC *** right reserved.

关键词： Ethanol

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Thermal management matters in photovoltaic–electrocatalysis for solar hydrogen production

EcoEnergy

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EcoEnergy 2024年

作者： Jie Chen Xin Chen Jie Sun Jingkuo Qu Xiangjiu Guan Shaohua Shen School of Chemical Engineering and Technology Xi'an Jiaotong University Xi'an China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

Photovoltaic–electrolysis (PV-EC) system currently exhibits the highest solar to hydrogen conversion efficiency (STH) among various technical routes. This perspective shifts the focus from the materials exploration in photovoltaics and electrolysis to the critical aspect of thermal management in a PV-EC system. Initially, the theoretical basis that elucidates the relationships between temperature and the performance of both photovoltaics and electrolyzers are presented. Following that, the impact of thermal management on the performance of PV-EC for solar hydrogen production is experimentally demonstrated by designing variables-controlling experiments. It is observed that while utilizing identical PV and EC cells under varying thermal conditions, the highest STH can reach 22.20%, whilst the lowest is only 15.61%. This variation underscores the significance of thermal management in optimizing PV-EC systems. Finally, increased efforts to enhancing heat transfer and optimizing heat distribution are proposed, thus facilitating the design of more efficient PV-EC systems with minimized thermal energy losses.

关键词： device design photovoltaic-electrolysis solar to hydrogen thermal management water electrolyzer

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Non-Hermitian delocalization in a 2D photonic quasicrystal

arXiv

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arXiv 2023年

作者： Zhang, Zhaoyang Liang, Shun Septembre, Ismaël Yu, Jiawei Huang, Yongping Liu, Maochang Zhang, Yanpeng Xiao, Min Malpuech, Guillaume Solnyshkov, Dmitry Key Laboratory for Physical Electronics and Devices The Ministry of Education Shaanxi Key Lab of Information Photonic Technique School of Electronic Science and Engineering Faculty of Electronics and Information Xi’an Jiaotong University Xi’an710049 China Institut Pascal PHOTON-N2 Université Clermont Auvergne CNRS Clermont INP Clermont-FerrandF-63000 France International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Department of Physics University of Arkansas FayettevilleAR72701 United States National Laboratory of Solid State Microstructures School of Physics Nanjing University Nanjing210093 China Paris75231 France

Quasicrystals show long-range order, but lack translational symmetry. So far, theoretical and experimental studies suggest that both Hermitian and non-Hermitian quasicrystals show localized eigenstates. This localization is due to the fractal structure of the spectrum in the Hermitian case and to the transition to diffusive bands via exceptional points in the non-Hermitian case. Here, we present an experimental study of a dodecagonal (12-fold) photonic quasicrystal based on electromagnetically-induced transparency in a Rb vapor cell. The transition to a quasicrystal is obtained by superposing two honeycomb lattices at 30◦ with a continuous tuning of their amplitudes. Non-Hermiticity is controlled independently. We study the spatial expansion of a probe wavepacket. In the Hermitian case, the wavepacket expansion is suppressed when the amplitude of the second lattice is increased (quasicrystal localization). We find a new regime, where increasing the non-Hermitian potential in the quasicrystal enhances spatial expansion, with the C12 symmetry becoming visible in the wavepacket structure. This real-space expansion is due to a k-space localization on specific quasicrystal modes. Our results show that the non-Hermitian quasicrystal behavior is richer than previously thought. The localization properties of the quasicrystals can be used for beam tailoring in photonics, but are also important in other fields. Copyright © 2023, The Authors. All rights reserved.

关键词： Quasicrystals

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Surface sulfurization activating hematite nanorods for efficient photoelectrochemical water splitting

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Science Bulletin 2019年第17期64卷 1262-1271页

作者： Lianlian Mao Yu-Cheng Huang Yanming Fu Chung-Li Dong Shaohua Shen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Department of Physics Tamkang University Tamsui 25137 Taiwan China

Surface treatment is an effective method to improve the photoelectrochemical(PEC) performance of photoelectrodes. Herein, we introduced a novel strategy of surface sulfurization to modify hematite(a-Fe2 O3)nanorods grown in an aqueous solution, which triggered encouraging improvement in PEC *** comparison to the solution-grown pristine a-Fe2 O3 nanorod photoanode that is PEC inefficient and always needs high temperature(>600 °C) activation, the surface sulfurized a-Fe2 O3 nanorods show photocurrent density increased by orders of magnitude, reaching 0.46 mA cmà2 at 1.23 V vs. RHE(reversible hydrogen electrode) under simulated solar illumination. This improvement in PEC performances should be attributed to the synergy of the increased carrier density, the reduced surface charge carrier recombination and the accelerated water oxidation kinetics at the a-Fe2 O3/electrolyte interface, as induced by the incorporation of S ions and the formation of multi-state S species(Fe-Sx-Oy) at the surface of a-Fe2 O3 nanorods. This study paves a new and facile approach to activate a-Fe2 O3 and even other metal oxides as photoelectrodes for improved PEC water splitting performances, by engineering the surface structure to relieve the bottlenecks of charge transfer dynamics and redox reaction kinetics at the electrode/electrolyte interface.

关键词： Photoelectrochemical Water splitting Hematite nanorods Photoanodes Surface sulfurization

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PREFACE: SPECIAL ISSUE FOR THE 2ND INTERnational SYMPOSIUM ON THERMAL-FLUID DYNAMICS (ISTFD2021)

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Heat Transfer Research 2022年第8期53卷 V-VI页

作者： Cheng, Lixin Bai, Bofeng Guo, Zhixiong School of Energy and Power Engineering Beijing University of Technology Beijing100124 China Department of Engineering and Mathematics Sheffield Hallam University SheffieldS1 1WB United Kingdom State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Department of Mechanical and Aerospace Engineering Rutgers The State University of New Jersey PiscatawayNJ08854 United States

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Boosted Photocatalytic Co2 Reduction by Induced Electromotive Force in Rotating Magnetic Field

SSRN

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SSRN 2023年

作者： Lu, Danchen Ren, Yuqi Yang, Ya Cheng, Miao Wang, Ke Wang, Nan Liu, Maochang Zhou, Jiancheng Chen, Wenshuai Li, Naixu School of Chemistry and Chemical Engineering Southeast University No.2 Dongnandaxue Road Jiangsu Nanjing211189 China CAS Center for Excellence in Nanoscience Beijing Key Laboratory of Micro-nano Energy and Sensor Beijing Institute of Nanoenergy and Nanosystems Chinese Academy of Sciences Beijing101400 China Key Laboratory of Bio-Based Material Science and Technology Ministry of Education Northeast Forestry University No. 26 Hexing Road Harbin150040 China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University No.28 Xianning West Road Shaanxi Xi'An710049 China

Charge separation plays a crucial role in semiconductor-based photocatalytic CO2 conversion. Herein, we report a unique induced electric field, which can actively manipulate carrier behavior at the minuscule, leading to significantly boosted photocatalytic CO2 reduction in H2O vapor. The success relies on the development a monolithic photocatalyst made of a copper foam substrate and nanosized ZnO/NiO/Au heterostructures that can effectively couple a special rotating magnetic field (RMF). Specifically, the copper foam cuts the magnetic induction line, leading to the periodic generation of induced electric field. This induced electric field could significantly increase the carriers' density by preventing their recombination. Moreover, NiO and Au as the active sites for oxidation and reduction, respective, synergistically magnify this effect. As a result, compared with the photocatalytic reaction without adding RMF, the utilization rate of photogenerated electrons increases by 5.24 times after coupling RMF, with the yield of CO and CH4 improved by 5.50 times and 5.18 times. This strategy by integrating unique RMF into the reaction system provides new insights for improving photocatalytic CO2 conversion. © 2023, The Authors. All rights reserved.

关键词： Carbon dioxide

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Study on TMD Control on Stability Improvement of Barge-Supported Floating Offshore Wind Turbine Based on the Multi-Island Genetic Algorithm

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China Ocean engineering 2019年第3期33卷 309-321页

作者： DING Qin-wei LI Chun CHENG Shan-shan HAO Wen-xing HUANG Zhi-qian YU Wan School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai 200093 China Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering Shanghai 200093 China School of Engineering University of Plymouth Devon PL4 8AA UK

A floating offshore wind turbine (FOWT) has a great potential in producing renewable energy as offshore wind resource is rich in deep sea area (water deeper than 60 m) where fixed foundations are cost-effective or deployable. However, compared with a fixed-bottom installation, FOWT has to suffer more extreme loads due to its extra degrees of freedom. Therefore, the stability of an FOWT is a key challenge in exploiting offshore deep-water wind. Focusing on the stability of barge-type FOWT, this paper is to investigate the effect of passive structural control by equipping a tuned mass damper (TMD) on the nacelle. The turbulent wind with sharp fluctuations is established both in velocity and inflow direction based on standard Kaimal turbulence spectrum as suggested in the standard IEC61400-2. The irregular wave is generated according to the Pierson-Moskowitz spectrum. The dynamic structural characteristics of FOWT are calculated based on the fully coupled aero-hydro-servo-elastic solver FAST. Evidence has shown that the proposed method of the nacelle-based TMD is effective in controlling stability of an FOWT, as the sway and roll motions of barge and the side-side displacement of tower top decreased significantly. With the increase of mass, the side-side displacement of tower-top and the amplitude of roll motion of barge reveal a trend of increasing first and then decreasing. The stiffness and damping have little effect. Furthermore, the multi-island genetic optimization algorithm (MIGA) is employed to find globally optimum structural parameters (mass, stiffness and damping) of the TMD. The optimum structure parameters of TMD are achieved when the mass is 21393 kg, damping is 13635 N/(m/s) and stiffness is 6828 N/m. By adopting the optimized TMD, stability of roll motion of barge and side-side displacement of tower-top increase up to 53% and 50% respectively when compared with the normal TMD. The simulation results verify the validity and reliability of the proposed TM

关键词： FOWT barge TMD MIGA wind wave stability

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Film levitation and central jet of droplet impact on nanotube surface at superheated conditions

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Physical Review E 2020年第4期102卷 043108-043108页

作者： Dongdong Zhou Yuhui Zhang Yu Hou Xin Zhong Jian Jin Lidong Sun State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi 710049 China State Key Laboratory of Mechanical Transmission School of Materials Science and Engineering Chongqing University Chongqing 400044 China

Influences of surface nanotubes at high temperatures are investigated on droplet impact dynamics and Leidenfrost effect. Five distinct regimes of impact droplets are found on the nanotube surface, including contact boiling, film levitation, central jet levitation, central jet, and Leidenfrost phenomenon. The regimes of film levitation, central jet levitation, and central jet are characterized by either film levitation and/or liquid central jet. The regime of Leidenfrost phenomenon is characterized by droplet bounce-off behavior free of any liquid jets. Film levitation is driven by the vaporization of two parts of the droplet, with one as the droplet bottom layer over the contact area above the nanotube structure, and the other as the hemiwicking liquid in nanotubes. Both the vaporization is impaired by increasing the surface temperature, which is attributed to the reduced contact time and less extent of spread of the droplet at a higher surface temperature. The central jet phenomenon is driven by the vapor stream produced by hemiwicking liquid in the central area upon impact. It is enhanced and then suppressed by elevating the surface temperature, resulting from the collective effects of the vapor pressure in nanotubes which increases with the surface temperature, and the cross-sectional area of the vapor stream, which increases and then decreases with the surface temperature. At a high Weber number, the Leidenfrost temperature can be increased by 125∘C on the nanotube surface, implying a great potential in heat transfer enhancement for droplet-based applications.

关键词： Drop & bubble phenomena Drop breakup multiphase flows

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Experimental investigation of gasoline spray vaporization behaviors under various ambient conditions 12

Experimental investigation of gasoline spray vaporization be...

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12th Asia-Pacific Conference on Combustion, ASPACC 2019

作者： Zhan, Cheng Yang, Rui Tong, Shangqing Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

In terms of spray vaporization visualization, effects of ambient temperature (394-516 K) and ambient pressure (0.1-3.8 MPa) on multi-hole gasoline spray macroscopic characteristics has been investigated separately via optical diagnostics. Schlieren method was adopted to visualize vapor phase fuel at high ambient temperature. Laser sheet optical patternation provided us with cross-section perspective to verify results in schlieren images and acquire additional information like plume distribution. The results show that vaporization process will be promoted by high ambient temperature due to enhanced heat transfer between spray body and surrounding gas. The effects of ambient pressure on spray evolution possess different inner mechanisms with ambient temperature variation. In low ambient temperature, axial evolution indicated by vapor tip penetration will be restricted by high ambient pressure, whereas radial expansion indicated by spray angle will be facilitated. For atmospheric ambient pressure in high ambient temperature, spray collapse will appear due to enhanced vaporization of single plume and intensified jet-to-jet interaction. Moreover, because of inhibited vaporization of light component in high ambient pressure, vaporization model will transfer from distilled-like vaporization to co-vaporization, indicated by homogeneous vapor phase distribution. © Asia-Pacific Conference on Combustion, ASPACC *** right reserved.

关键词： Vaporization

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Large eddy simulation on the respective roles of integral length scale and turbulence intensity on turbulent premixed combustion 12

Large eddy simulation on the respective roles of integral le...

引用

12th Asia-Pacific Conference on Combustion, ASPACC 2019

作者： Shilong, Guo Meng, Zhang Jinhua, Wang Xutao, Wei Zuohua, Huang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

The effects of integral length scale () and turbulence intensity (? ) on premixed combustion are studied using large eddy simulation. Three groups of lean CH4/air flames are carried out using the thickened flame model combined with a two-step reduced chemical mechanism. Two groups vary at constant ? and the other group increases ? from low to high while keeping unchanged. One of the cases is validated to available experimental data, showing good agreement for the flame-brush structure. The numerical results show that the increase in or ? leads to a decrease in flame-brush height and an increase in flame-brush thickness and volume. The turbulent flame speed () will be enhanced by these two factors within the scope of our study. All the flame-brush structure data, including height, thickness, volume and area, and also collapse onto a single line when the turbulent Reynolds number is used as abscissa. The probability density function distributions of filtered thickened flame front curvature show that will be increased by and ? through increasing the amount of large-scale and small-scale wrinkling structures respectively. © Asia-Pacific Conference on Combustion, ASPACC *** right reserved.

关键词： Large eddy simulation

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