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SSRN 2022年

作者： Deng, Lei Dong, Lingxiao Bai, Yang Wu, Yuhao Liu, Hu Belošević, Srdjan Tomanović, Ivan Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China Guoshen Institute of Technology CHN ENERGY Xi'An710065 China Department of Thermal Engineering and Energy "VINČA" Institute of Nuclear Sciences National Institute of thе Republic of Serbia University of Belgrade Mike Petrovića Alasa 12-14 11351 Vinča PO Box 522 Belgrade11001 Serbia

The ultra-supercritical double-reheat boiler has attracted more attention because of high parameters, low pollution and large capacity. However, there are some difficulties in the development of this technology, such as adjusting the reheat steam temperature. In this study, computational fluid dynamics simulation is used to analyze a 660 MW double-reheat tower-type pulverized coal-fired boiler. The influence of flue gas recirculation (FGR) on heat transfer characteristics and combustion process in the furnace (including heating surfaces in the upper parts of the furnace) are evaluated. The user-defined function approach predicates CO reduction effect on NO x . The results show that the flow at the horizontal section through the centerline of recirculating flus gas nozzles is rotating. The velocity distribution changes into an elliptical rotating flow when FGR ratio is 20%. At higher FGR ratios, the high-temperature area (1565-1700 K) shrinks and both the NO x concentration at the low-temperature superheater outlet and oxygen concentration in the furnace descend. Oxygen concentration at low-temperature superheater outlet first increases and then decreases. In the main combustion zone, the heat flux peak of water-cooled wall is about 330 kW m -2 . As FGR ratio increases from 0% to 20%, the rate of water-cooled wall heat absorption to total boiler decreases by 3.50%. This rate for reheater and superheater increases by 2.53% and 2.13%, respectively. © 2022, The Authors. All rights reserved.

关键词： Temperature

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Effect of particle size on the thermal performance of NaNO3/SiC)2/C composite phase-change materials

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Particuology 2019年第3期17卷 169-175页

作者： Liang Liu Liqiong Wang Weichun Ge Yanfeng Ge Yun Huang State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology Beijing 100081 China State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences Beijing 100190 China State Grid Liaoning Electric Power Supply Co. Ltd. Shenyang 110004 China

Storage of thermal energy is a key technology for energy conservation and application of renewable energy sources. In this paper, the thermal performance of inorganic composite phase-change materials (PCMs;NaNO3/SiO2/C) is studied under extreme thermal conditions and the effect of raw particle size is examined. We designed a thermal shock test platform with a diffusive combustion system and in-situ infrared thermal imaging. The influences of the heat flux magnitude and exposure time on the performance of the PCMs were examined under vertical thermal shock conditions. Leakage of molten salt in the composite PCMs was observed as the heat flux reached a threshold point. The morphology and thermal properties were characterized by ex-situ SEM, XRD, DSC, and BET. Raw particles with sizes in the range of 105-500 μm were used to synthesize the composite material and examine its role in thermal shock behavior. Our experiments showed that deterioration of the thermal storage density was slowed as the particle size was increased. This work provides useful guidance for improving the anti-thermal shock ability of future material designs.

关键词： Thermal storage Phase change material Particle size Thermal shock Decomposition temperature

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Beam dynamics induced by the quantum metric of exceptional rings

arXiv

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arXiv 2024年

作者： Zhang, Zhaoyang Septembre, Ismaël Liu, Zhenzhi Kokhanchik, Pavel Liang, Shun Liu, Fu Li, Changbiao Wang, Hongxing 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 Naturwissenschaftlich-Technische Fakultät Universität Siegen Walter-Flex-Straße 3 Siegen57068 Germany 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 Paris75231 France

Topological physics has broadened its scope from the study of topological insulating phases to include nodal phases containing band structure singularities. The geometry of the corresponding quantum states is described by the quantum metric which provides a theoretical framework for explaining phenomena that conventional approaches fail to address. The field has become even broader by encompassing non-Hermitian singularities: in addition to Dirac, Weyl nodes, or nodal lines, it is now common to encounter exceptional points, exceptional or Weyl rings, and even Weyl spheres. They give access to fascinating effects that cannot be reached within the Hermitian picture. However, the quantum geometry of non-Hermitian singularities is not a straightforward extension of the Hermitian one, remaining far less understood. Here, we study experimentally and theoretically the dynamics of wave packets at exceptional rings stemming from Dirac points in a photonic honeycomb lattice. First, we demonstrate a transition between conical diffraction and non-Hermitian broadening in real space. Next, we predict and demonstrate a new non-Hermitian effect in the reciprocal space, induced by the non-orthogonality of the eigenstates. We call it transverse non-Hermitian drift, and its description requires biorthogonal quantum metric. The non-Hermitian drift can be used for applications in beam steering. Copyright © 2024, The Authors. All rights reserved.

关键词： Topology

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Effect of water addition on auto-ignition of kerosene under afterburner relevant conditions 12

Effect of water addition on auto-ignition of kerosene under ...

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12th Asia-Pacific Conference on Combustion, ASPACC 2019

作者： Sun, Wuchuan Huang, Wenlin Qin, Xiaokang Zhang, Yingjia Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Ignition delay times were measured for stoichiometric kerosene/air mixtures with and without H2O addition behind reflected shock conditions: pressures of 0.45 - 7.5 atm and temperatures of 900 - 1450 K. The effect of H2O addition on the reactivity of RP-3 was explored at various pressure and temperatures. The Arrhenius-type expressions were fitted by using the current ignition data. A four-component surrogate model of RP-3 was proposed based on similarity criterion of function group. The proposed model generally reproduces the tendency of pressure-dependence of ignition delay times but it over-predicts the experimental data at lower pressures. The addition of H2O presents different effects at elevated pressures. The kinetic analysis was performed to clarify the kinetic and thermodynamic effects. © Asia-Pacific Conference on Combustion, ASPACC *** right reserved.

关键词： Kerosene

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Phenomenon of fog formation and flow characteristics of droplet-vapor-gas mixture in a cooler-condenser

Phenomenon of fog formation and flow characteristics of drop...

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ASME 2019 International Mechanical engineering Congress and Exposition, IMECE 2019

作者： Gu, Hongfang Guo, Qiwei Li, Changsong Zhou, Qing State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an Shaanxi China

ISBN: (纸本)9780791859452

Fog formation occurs in the process of condensation in the presence of non-condensable gas if the bulk temperature is lower than its saturation temperature (supersaturated). The phenomena of fogging is the formation of small condensate particles mixing with the vapor/gas stream, which creates potential problems of the vapor/gas/condensate separation and environmental pollution. Therefore, understanding of fogging mechanism and prevention of fog droplet entrainment are one of technical concerns for design and operation of cooler-condensers in the process industry. This paper presents the experimental study and numerical simulation of shell-side condensation with fog formation using a mixture of steam/non-condensable gas. The experimental data were collected on the two tube bundles (modified plastic tubes and stainless steel tubes). Using a high-speed photograph technique, the phenomenon of fog formation and flow characteristics of vapor/droplet transport were recorded over a wide range of test conditions. The numerical analysis of film and dropwise condensation, fog formation and droplet particle transport were simulated using different tube geometry and material, and flow velocity of air/droplet mixture. Based on simulation results, a new droplet trapping parameter is proposed to assess the optimal parameters of heat exchanger structural and operation conditions. Comparisons show that the numerical analysis results have a good agreement with experimental data and observations. These findings provide fundamental approach to account for the effect of fog formation, film and dropwise condensation, and droplet transport crossflow in cooler-condensers. Copyright © 2019 ASME.

关键词： Drops

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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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Experimental study of auto-ignition of dimethyl ether at low-temperatures and low-pressures 12

Experimental study of auto-ignition of dimethyl ether at low...

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12th Asia-Pacific Conference on Combustion, ASPACC 2019

作者： Huang, Wenlin Sun, Wuchuan Wu, Honghuan Qin, Xiaokang Jiang, Xue Zhang, Yingjia Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Dimethyl ether (DME) is a property of alternative fuels to attract due to the special molecular structure in terms of either scientific study or engine application. However, the lack of fundamental data at low pressures and low temperatures impedes to understand thoroughly the chemistry of DME. Ignition delay times of DME/"air" mixtures with various equivalence ratios of 0.5 - 5.0 were measured in a shock tube at pressure of 3.0 atm over temperatures of 625 - 1200 K. Aramco Mech 2.0 was selected to reproduce the experimental observation. In general, the kinetic model remains an uncertainty in predicting the reactivity of DME at equivalence ratios below 2.0 but it tends much better at equivalence ratios over 3.0. Unlike the model predictions, the experimental data did not show obvious NTC behavior for the mixtures with equivalence ratios of 0.5 and 1.0. The selected model almost fails to capture the four-stage ignition feature for the mixtures with equivalence of 2.0 even considering the hot spot caused by pre-ignition energy release. © Asia-Pacific Conference on Combustion, ASPACC *** right reserved.

关键词： Ethers

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Melt droplet fragmentation behavior during fuel-coolant interaction 18

Melt droplet fragmentation behavior during fuel-coolant inte...

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18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2019

作者： Li, Gen Feng, Haobo Wen, Panpan Zhang, Jun Wang, Jinshi Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

During a severe accident of nuclear reactor, the fuel-coolant interaction occurs at the relocation stage of corium melt. Such a mode of contact can result in vigorous thermal interactions, intense steam generation and, potentially, steam explosions. The thermal processes, in their turn, largely depend on hydrodynamic behavior. When melt is pouring into coolant pool, the melt jet fragments into large droplets or blobs, named the primary breakup. The droplets or blobs will experience secondary breakup as a result of shock wave at steam explosion. Either the primary or secondary breakup is governed by interface hydrodynamic instabilities. The droplet size distribution, which affects fuel-coolant areas, is important for evaluating heat transfer and debris coolability. In this study, we modelled melt drops deformation and fragmentation using a meshless Lagrangian MPS method. Fragments amount and size distribution were compared under different Weber numbers, and fragments drag coefficient were also analyzed. The results indicate that the melt drops breakup process could be divided into two phases: initial deformation and fragmentation phase governed by flow inertial force and the subsequent fragments coalescence phase under the impact of fluid surface tension. Fragments amount increased in fragmentation phase but decreased in coalescence phase. A large amount of fragments has a normalized diameter of 0.01 - 0.03, but a small amount of large size fragments (d/d0 > 0.04) also appeared as the crescent-shaped melt broke up and small fragments coalesced. The drag coefficient decreased with time during drop deformation period, and then reached a stable value. It has no significant difference among cases with different Weber numbers. © 2019 American Nuclear Society. All rights reserved.

关键词： Hydrodynamics

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Theoretical Chemical Kinetic Study of the H-atom Abstraction from Ethanol by Hydroperoxyl Radical 12

Theoretical Chemical Kinetic Study of the H-atom Abstraction...

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12th Asia-Pacific Conference on Combustion, ASPACC 2019

作者： Zhao, Qian Sun, Wuchuan Deng, Fuquan Yang, Feiyu Zhang, Yingjia Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Reactions of ethanol + hydroperoxyl radical (H?2) are well known a crucial reaction class in oxidation mechanism of ethanol. However, the kinetic parameters of the reactions are basically extrapolated by analogy with n-butanol + H?2 system calculated by Zhou et al. [1]. The reliability of such the analogy remains to be seen, as no directly theoretical or experimental evidence is available in literature to date. In this study, thermal rate coefficients of H-atom abstraction reactions for ethanol + H?2 system were calculated at both CCSD(T)/cc-pVTZ//M06-2x/def-TZVP and CCSD(T)/CBS//M06-2x/def-TZVP levels of theory, with an uncertainty of a factor of 3, by means of using both conventional transition-state theory and canonical variational transition-state theory. Similar to n-butanol + H?2 system, the title reactions are dominated by alpha site H-abstraction, whereas the rate coefficients of all channels of ethanol are slightly slower than that of n-butanol + H?2 system. Generally, the new calculations show only limited effect on ethanol reactivity at low pressures and high temperatures (over 1300 K) but it prevents the kinetic mechanisms to over-predict ignition delay times under engine relevant conditions. © Asia-Pacific Conference on Combustion, ASPACC *** right reserved.

关键词： Ethanol

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Solid-solution-tuned d-band center boosts alkaline hydrogen evolution

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Journal of Materiomics 2025年

作者： Saiya Liu Wenjia Gu Chunyang Zhang Kejian Lu Fei Xue Maochang Liu International Research Center for Renewable Energy & State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China Suzhou Academy of Xi’an Jiaotong University Suzhou 215123 Jiangsu China

d-band center engineering in metal phosphide offers promising avenues to improve hydrogen evolution reaction (HER) activity through electronic modulation. However, precise d-band regulation via theoretically feasible double heteroatom modification remains challenging. This work demonstrates a ternary metal phosphide (Fe 0.5 V 0.5 NiP) engineered through Fe/V integration to optimize the d-band center of nickel phosphide (Ni 2 P). Combined experimental and theoretical analyses reveal that Fe and V synergistically shift the d-band center closer to the Fermi level, thereby balancing absorption/desorption of HER intermediates. Notably, V significantly reduces water dissociation energy barriers, while Fe–V cooperation optimizes hydrogen-adsorption Gibbs free energy. The Fe 0.5 V 0.5 NiP achieves exceptional alkaline HER performance, delivering overpotentials of 67.9 mV (10 mA/cm 2 ) and 203.1 mV (100 mA/cm 2 ) in 1 mol/L KOH, surpassing the benchmark Pt/C. Remarkably, it maintains stability for 100 consecutive hours without degradation. This work provides atomic-level insights on dual-heteroatom modified d-band tuning and establishes a rational design paradigm for high-performance metal phosphide electrocatalyst.

关键词： d-band center Metal phosphide Solid solution Alkaline HER electrocatalyst

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