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Numerical Simulation Investigating the Influence of Varied Stack Parameters on the Energy Conversion in Thermoacoutic Engines

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SSRN 2024年

作者： Yao, Chen Zhou, Yao Liu, Jiping Yan, Junjie MOE Key Laboratory of Thermal Fluid Science Engineering Xi’an Jiaotong Univeristy Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong Univeristy Xi’an710049 China

The stack is a crucial component of the thermoacoustic heat engine, influencing its capacity to generate stable pressure amplitude and enhance efficiency. Utilizing the discontinuous Galerkin (DG) method, fully compressible Navier-Stokes equations were solved to simulate the energy exchange between the stack and surrounding air under various conditions.(1) Simulations were conducted under different stack wall boundary conditions, including linear temperature distribution wall, isothermal wall, and adiabatic wall. The work performed by 1 kg of gas at a specific position during one cycle was defined as local energy density to analyse the effect of different stack spacing, stack length and stack thickness. (2) Too small a stack spacing causes the inability to generate pressure amplitude. Increasing the stack spacing continuously enhances the generated pressure amplitude, with the energy density distribution near the hot heat exchanger becoming more significant. As the stack spacing continues to increase, the energy density decreases at positions farther from the wall, leading to a reduction in pressure amplitude. The generated acoustic streaming intensity diminishes faster with the continuous increase in stack spacing. (3) A smaller stack length results in reduced viscous dissipation at the wall, leading to a larger generated pressure amplitude. However, shorter stack lengths cause increased gas oscillation displacement, resulting in lower energy density concentrate around the stack. This raises the load on the two heat exchangers, consequently reducing the overall efficiency. (4) The pressure amplitude decreases with the increase in stack thickness. The vortex intensity at the gap between the hot heat exchanger and the stack increases with the stack thickness, leading to higher viscous losses for the fluid passing through this region. Consequently, the performance of the thermoacoustic engine declines. These findings provide valuable guidance for the design of thermoa

关键词： Numerical methods

Sequential Growth of Cs_(3)Bi_(2)I_(9)/BiVO_(4)Direct Z-Scheme Heterojunction for Visible-Light-Driven Photocatalytic CO_(2)Reduction

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Transactions of Tianjin University 2023年第6期29卷 462-472页

作者： Long Jiang Hanrui Du Le Li Xiangjiu Guan Yihao Zhang Liwei Li Xiaoxu Liu Lei Li Yingcheng Tian Li Zhang Shuai Wang Jie Chen Shaohua Shen State Key Laboratory for Performance and Structure Safety of Petroleum Tubular Goods and Equipment Materials CNPC Tubular Goods Research InstituteXi’an 710077China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an 710049China School of Chemical Engineering and Technology Xi’an Jiaotong UniversityXi’an 710049China CNPC National Engineering Research Center for Oil and Gas Drilling Equipment Co. Ltd.Baoji 721002China China Coal Energy Research Institute Co. Ltd.Xi’an 710049China

The high exciton binding energy and lack of a positive oxidation band potential restrict the photocatalytic CO_(2)reduction efficiency of lead-free Bi-based halide perovskites Cs_(3)Bi_(2)X_(9)(X=Br,I).In this study,a sequential growth method is presented to prepare a visible-light-driven(λ>420 nm)Z-scheme heterojunction photocatalyst composed of BiVO_(4)nanocrystals decorated on a Cs_(3)Bi_(2)I_(9)nanosheet for photocatalytic CO_(2)reduction coupled with water *** Cs_(3)Bi_(2)I_(9)/BiVO_(4)Z-scheme heterojunction photocatalyst is stable in the gas-solid photocatalytic CO_(2)reduction system,demonstrating a high visible-light-driven photocatalytic CO_(2)-to-CO production rate of 17.5μmol/(g·h),which is approximately three times that of pristine Cs_(3)Bi_(2)I_(9).The high efficiency of the Cs_(3)Bi_(2)I_(9)/BiVO_(4)heterojunction was attributed to the improved charge separation in Cs_(3)Bi_(2)I_(9).Moreover,the Z-scheme charge-transfer pathway preserves the negative reduction potential of Cs_(3)Bi_(2)I_(9)and the positive oxidation potential of BiVO_()*** study off ers solid evidence of constructing Z-scheme heterojunctions to improve the photocatalytic performance of lead-free halide perovskites and would inspire more ideas for developing leadfree halide perovskite photocatalysts.

关键词： Lead-free halide perovskite Z-scheme heterojunction CO_(2)reduction Visible-light photocatalysis Charge transfer

Dynamic performance analysis of different schemes of solar tower power plant

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Dynamic performance analysis of different schemes of solar t...

International Conference on power engineering 2021, ICOPE 2021

作者： Wang, Yaqian Chen, Weixiong Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

In this paper, solar power tower stations with different configurations of steam generators are proposed, and a detailed dynamic model of one-dimensional distributed parameters is established and verified. The response characteristics of the two systems under the disturbance of the main controllable variables are calculated, and the results are analyzed and compared. It is concluded that, compared with steam turbines, steam generation systems have significant thermal inertia, and different steam generation system schemes will have a significant impact on the dynamic performance of the system. For a natural circulation-driven system, the energy balance and power output are more sensitive to the hot salt mass flow rate, and mass balance would be adjusted by the feedwater mass flow. For a once-through-driven system, the energy balance is controlled by hot salt mass flow, but the mass balance and power output should be adjusted by the feedwater mass flow. © 2021 The Japan Society of Mechanical Engineers.

关键词： Solar energy

Changing Conditions and Thermodynamic Transient Characterization of Therminol VP-1 Oil-Water Heat Exchanger

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Changing Conditions and Thermodynamic Transient Characteriza...

power System and New Energy Technology Innovation Forum (NPSIF), Boao New power System International Forum -

作者： Shuai Dong An Zheng Peng Wang Chaoyang Wang HUANENG YIMIN COAL-POWER CO. LTD. Hulunbuir China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

ISBN: (数字)9798331504557

ISBN: (纸本)9798331504564

In this paper, the exergy efficiency of high-pressure heater feedwater in a coal-fired power generation thermal system heated with Therminol VP-1 as the thermal fluid is investigated, and the transient characteristics of the heat exchanger are analyzed after changes in heat transfer oil parameters. The results show that the exergy efficiency of Therminol VP-1 for heating feedwater tends to decrease as the unit load decreases. The exergy efficiency for heating high pressure heater feedwater was 80% to 90%, with a maximum of 90.3%. The time required to reach the new steady state after perturbation of the boundary parameters of the oil-water heat exchanger increased with the load rate, with a minimum of 200 s and a maximum of 500 s in the study range. the new steady state was reached more quickly with increasing load than with decreasing load.

关键词： Thermodynamics Technological innovation Oils Water heating power system stability Thermal analysis Steady-state Transient analysis Heat transfer Turbines

Experimental Study on the Propagation Mechanism of Acetylene-Air Detonation Waves in a Unilaterally Intermittently Constrained Channel

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SSRN 2024年

作者： Gai, Jingchun Qiu, Hua Xiong, Cha Zhao, Minghao He, Xinlu Yang, Zhan Feng, Zhiyuan Cehn, Xitao Huang, Zuohua School of Power and Energy Northwestern Polytechnical University Xi’an710072 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

This study experimentally explores the propagation mechanisms of acetylene/air detonation waves within a channel intermittently constrained on one side, utilizing soot foil and high-speed schlieren photography to capture the cellular structure and shock-flame evolution. The experiments revealed that the detonation waves traverse the semi-enclosed channel with various discrete wall configurations on the side in four distinct propagation modes: (I) periodic detonation failure and re-initiation;(II) single extinction and re-initiation;(III) localized extinction and (IV) non-extinction. Mode I occurs exclusively when the open area ratio exceeds 0.85, while detonation tends to favour Mode II when the gaps between discrete walls exceed three times the cell size;otherwise, it tends towards Modes III and IV. The re-initiation mechanism of detonation involves curvature shocks inducing local explosions of reactive mixtures through multiple Mach reflections off the discrete walls. The self-sustained propagation mechanism of the detonation wave is maintained by the interaction of strong transverse shocks reflected from discrete walls with the inherent transverse waves within the detonation structure, sustaining the instability of the cellular detonation. © 2024, The Authors. All rights reserved.

关键词： Detonation

Intra-Ring Bridging:A Strategy for Molecular Design of Highly Energetic Nitramines

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Chinese Journal of Chemistry 2021年第10期39卷 2857-2864页

作者： Linyuan Wen Tao Yu Weipeng Lai Jinwen Shi Maochang Liu Yingzhe Liu Bozhou Wang State Key Laboratory of Fluorine&Nitrogen Chemicals Xi'an Modern Chemistry Research InstituteXi'anShaanxi710065 China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong UniversityXi'anShaanxi 710049China

Main observation and conclusion Important progress has been made in the development of energetic molecules with high performance by computer-aided molecular design in recent years,but structural novelty of organic scaffolds is *** this work,we propose an intra-ring bridging strategy inspired by the known energetic nitramines to design novel polycyclic and cage energetic *** than 100 energetic structures were designed by introducing the C—C bridges and increasing the ring *** synthesis difficulty is considered besides the two most concerned properties of EMs,energy and *** a comprehensive estimation,a symmetric cage molecule labeled as 8U-30 was finally selected because of its relatively high detonation performance,and comparable impact sensitivity as well as synthetic accessibility with ***,the proposed strategy could be utilized in further molecular design to gain various scaffolds,especially cage structures,for different demands.

关键词： Molecular modeling Energetic materials Cage compounds Computational chemistry Nitramines

A Preliminary Study on the Blistering Behavior of Dispersion Plate-Type Fuel Assembly

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SSRN 2024年

作者： Yu, Songjiao Zhang, Kui Yang, Yiming Liu, Yumin Tian, Wenxi Qiu, Suizheng School of Nuclear Science and Technology Shanxi Key Laboratory of Advanced Nuclear Energy and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

The dispersion plate fuel assembly, owing to its favorable characteristics of low temperature gradient, high stability, and excellent thermal conductivity, has become a focal point in the research of novel high-performance fuel elements. However, the current literature lacks a comprehensive understanding of the fuel plate's performance, particularly with regard to the bubbling phenomenon in the fuel plate cladding. In this study, we have implemented a fission gas release model, building upon previous analyses of fuel plate performance under steady-state operation. By comparing our calculation results with the Forsberg-Massih model, we find a close correspondence in trends, thereby validating the accuracy of our computational approach. Furthermore, we utilize the upgraded FROBA-PLATEs code to predict the blistering behavior of fuel plates under specific quasi-steady-state conditions. Our results demonstrate that the occurrence position and threshold temperature of blistering in the fuel assembly can be precisely predicted using this approach. © 2024, The Authors. All rights reserved.

关键词： Fission products

3D In2S3/C/Fe3C nanofibers for Z-scheme photocatalytic CO2 conversion to acetate

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Materials Today Catalysis

Materials Today Catalysis 2023年 3卷

作者： Liao, Chen Jing, Wenhao Wang, Feng Liu, Ya International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi 710049 China

Constructing a Z-scheme heterostructure is of great significance to achieve efficient photocatalytic CO2 conversion without sacrificial reagents. However, the fabrication of a well-suited Z-scheme remains a challenge. In this work, we constructed a Z-scheme system with a suitable band structure by in-situ hydrothermal growth of In2S3 nanosheets on electrospun Fe3C/Carbon fibers with 3D structure. The Z-scheme electron transport path is verified by the calculation of the energy band structure calculation and the method of photodeposition, indicating that In2S3 and Fe3C are reduction reaction sites and oxidation reaction sites respectively. Carbon fibers serve as both the skeleton of the 3D structure and the electron mediator from Fe3C to In2S3. Moreover, the DFT calculation demonstrates that the introduction of Fe3C can reduce the energy barrier of *CO and *COH coupling on In2S3, and weaken the bonding of In-S, thereby enhancing the product selectivity towards acetate. Owing to the efficient charge transfer of the Z-scheme system, the photocorrosion in In2S3 is also greatly reduced, showing a relatively stable chemical composition after several hours of reaction. Compared with In2S3 and Fe3C/C, In2S3-C/Fe3C composites showed a significantly increased acetate evolution rate of 11.33 μmol/h/g without any sacrificial reagents. This work provides important insights into the design and research of the photocatalyst system that combines a monolithic 3D structure and a Z-scheme charge flow for efficient CO2 conversion. © 2023 The Authors

关键词： Carbon fibers

Experimental and Numerical Simulation Study on Critical Heat Flux in Narrow Rectangular Channels

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SSRN 2024年

作者： Lv, Xindi Zhang, Dalin Song, Gongle Su, Guanghui Tian, Wenxi Qiu, Suizheng State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China

Experimental investigation was performed on the critical heat flux (CHF) in narrow rectangular channels. The rectangular channel adopts single-side heating, the channel gaps were 1.3 and 1.9mm, the system pressure was 1~4Mpa, the inlet subcooling was 20~100K, and the mass flux was 200~1500 kg/(m2⋅s). The variation of CHF in vertical upward flow with different thermal parameters and geometric dimensions was studied. A three-fluid transient model was established to calculate the CHF of vertical upward annular flow in narrow rectangular channel. The calculation model was validated with CHF experimental data and the results were in good agreement. Combining experimental and theoretical research results, it could be concluded that the mass flow rate played an important role in the critical heat flux phenomenon of narrow rectangular channel, and its magnitude directly affected the effect of changes in thermal parameters such as pressure, mass flow rate and inlet subcooling on CHF. © 2024, The Authors. All rights reserved.

关键词： Heat flux