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Experimental investigations on flow instabilities in a forced circulation loop at near-critical and supercritical pressures

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AIP Conference Proceedings 2013年第1期1547卷

作者： Lei Zhang Haijun Wang Hongfang Gu Shouxu Qiao Xiaobao Shi Yushan Luo State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiao tong University Xi'an 710049 China

Properties of supercritical water will undergo drastic changes near the "pseudo critical" point which gives rise to a serious concern about flow instabilities under supercritical conditions. To investigate the fluid flow behaviors, experiments with different system pressures (near-critical and supercritical pressure) were conducted on the Xi'an Jiao tong University's (XJTU) supercritical water test facility. Large amplitudes of mass flow flux as well as inlet pressure were found in various operation conditions. Mechanism of this unusual flow instability behavior is discussed. The oscillation behavior occurring in the present work has also been compared with that under the subcritical pressures and parameters effects are also studied.

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Research on condensation of n-octane/n-nonane in throttling flow

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2011年第SUPPL. 1期32卷 150-153页

作者： Lü, Xiao-Fei Liu, Hai Li, Ming-Sheng Chang, Chun Bai, Bo-Feng State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China First Gas Production Factory Xinjiang Oil field Company Karamay 834000 China

A numerical model was developed to simulate the condensation flow of the n-octane/n-nonane in three dimension throttle. With this model the condensation properties of n-octane/n-nonane in throttle were investigated, it was found that the maximum supersaturation ratio of n-octane/n-nonane vapor in the homogeneous condensation process was very high, in comparison n-nonane was harder to condense. The influence of inlet supersaturation ratio, total pressure and total temperature on the condensation of n-nonanein in throttling flow process was analyzed. From the results, the direct influences of inlet parameters were found on the wilson point location, average droplet radius and liquid phase mass fraction.

关键词： Condensation

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Study of thermophysical properties of binary mixtures of N-phenyl ethanolammonium based protic ionic liquids with water and ethanol solvents

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Journal of Ionic Liquids 2022年第1期2卷

作者： Chennuri, Bharath Kumar Losetty, Venkatramana Sreenivasulu, K. Gardas, Ramesh L. Sivakumar, K. A.P. Tirupati517502 India Department of Chemistry VelTech Rangarajan Dr. Sagunthala R&D Institute of Science and Technology Avadi Chennai600062 India Department of Chemistry State Key Laboratory of Multiphase Flow in Power Engineering Xian Jiaotong University Xian710049 China Department of Chemistry Indian Institute of Technology Madras Chennai600036 India

This work reveals that the physicochemical properties such as density, ρ and speed of sound, u for the binary mixtures of N-phenylethanolammonium formate ([NPEA][For]) and N-phenylethanolammonium acetate ([NPEA][Ace] with water and ethanol solvents were experimentally measured for the temperature ranges from 293.15 K to 318.15 K at atmosphere pressure. The apparent molar volume, VΦ and apparent molar isentropic compressibility, κs,Φ were estimated from the experimental data. Redlich-Mayer type empirical equation was applied to calculate the limiting apparent molar properties at infinite dilution (Vω∞ and k∞) and corresponding empirical parameters (Sv, Bv, Sk and Bk). The type of interaction either IL-solvent or IL-IL or solvent-solvent occurring in solution were determined from the data of empirical parameters. Furthermore, the temperature dependent apparent molar volume at infinite dilution, V∞ was used to calculate the apparent molar expansibility at infinite dilution, E∞. Moreover, these E∞ values of the studied binary solutions were found to be positive. The making and breaking structure ability of both PILs were analyzed at all experimental conditions. © 2021 The Authors

关键词： Dilution

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Investigation on the flow distribution characteristics of a water-wall intermediate header at a supercritical pressure

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Reneng Dongli Gongcheng/Journal of engineering for Thermal Energy and power 2006年第3期21卷 299-302页

作者： Zhu, Yu-Qin Bi, Qin-Cheng Chen, Ting-Kuan State Key Laboratory of Power Engineering Multi-Phase Flow Xi'an Jiaotong University Xi'an 710049 China

An investigation was conducted of the flow distribution characteristics of distribution header water-wall tubes under a supercritical pressure for a home-made 600 MW once-through boiler. The test parameters can be listed as follows: pressure p=23-25 MPa, mass flow rate G=400-1200 kg/(m2·s), working medium temperature t=10-400°C. An experimental study has been conducted of the impact of working medium pressure, mass flow rate and working medium temperature on the vertical water-wall tube flow distribution characteristics of the distribution header. The test results show that with an increase in mass flow rate, the uniformity of flow distribution among the vertical water-wall tubes could be enhanced. The non-uniformity of flow distribution will undergo a step increase near the quasi-critical points. Moreover, with an increasing pressure, the above-mentioned step increase will become weaker. By employing a discrete model of the parallel-connected branch tubes of the distribution header, the flow distribution among the distribution header vertical water-wall tubes was calculated and the calculation results are in good agreement with the test ones.

关键词： Distribution header Once-through boiler Supercritical pressure Vertical water-wall tubes

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Pressure-velocity coupling algorithm on non-orthogonal non-staggered grid

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Jisuan Lixue Xuebao/Chinese Journal of Computational Mechanics 2006年第1期23卷 93-96页

作者： Xie, Gong-Nan Wang, Qiu-Wang Zhang, Dong-Sheng Tao, Wen-Quan State Key Laboratory of Multi-phase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

In this paper, a new numerical procedure is proposed for the steady flow of a viscous, incompressible fluid based on SIMPLER algorithm on a non-orthogonal non-staggered grid, together with Cartesian velocity components as dependent variables in the momentum equations. The main feature of the algorithm is that the pressure and pressure correction equations are obtained by explicitly treating pressure cross-derivatives terms in interface contravariant velocities. A collocated arrangement of variables is introduced on numerical grids, and the cell face velocities are calculated by the momentum interpolation. It is proved that this algorithm can be effectively used to simulate fluid flow and heat transfer in complex geometry, by the validation calculation of flow inside branching channel.

关键词： Incompressible flow

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Effects of Flue Gas Recirculation on Combustion and Heat Flux Distribution in 660 Mw Double-Reheat Tower-Type Boiler

SSRN

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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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Numerical Simulation of Acoustic Propagation in Gas Ultrasonic flowmeter

SSRN

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SSRN 2022年

作者： Xiao, Yongqing Zhang, Meng Li, Dong Yang, Yueming Ma, Bingkun Qi, Jianhui School of Energy and Power Engineering Shandong University Jinan250061 China Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power University Beijing102206 China Suzhou Research Institute Shandong University Suzhou215123 China Shandon Academy of Sciences China

Ultrasonic flowmeter has been widely used in chemical smelting, industrial production and other fields. Through the COMSOL Multiphysics software, the non-linear trajectory of the rays in the non-invasive and intrusive UFW is first simulated by the ray tracing method. Then, the transient ultrasonic propagation process is simulated to analyze the reasons for the error of ultrasonic propagation. Finally, the cause of the error of the transducer is analyzed by the sound pressure signal at the receiving end. It was found that it is precisely because of the high-speed flow that the ultrasonic propagation is distorted, which is manifested as the non-linear trajectory and downstream drift of the sound beam. The signal at the receiving end also fails to hit the correct position due to beam drift, resulting in sound pressure falling below the detected value. © 2022, The Authors. All rights reserved.

关键词： flow measurement

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Comparison of chemical composition and acidity of size-resolved inorganic aerosols at the top and foot of Mt. Hua, Northwest China: The role of the gas-particle distribution of ammonia

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Science of the Total Environment 2023年 905卷 166985页

作者： Feng, Qiao Liu, Haijiao Dai, Wenting Cao, Yue Shen, Minxia Liu, Yali Qi, Weining Chen, Yukun Guo, Xiao Zhang, Yifan Li, Lu Zhou, Bianhong Li, Jianjun State Key Laboratory of Loess and Quaternary Geology Key Lab of Aerosol Chemistry and Physics Institute of Earth Environment Chinese Academy of Sciences Xi'an710061 China College of Geography and Environment Baoji University of Arts and Sciences Shaanxi Key Laboratory of Disaster Monitoring and Mechanism Simulation Baoji721013 China Xi'an Institute for Innovative Earth Environment Research Xi'an710061 China National Observation and Research Station of Regional Ecological Environment Change and Comprehensive Management in the Guanzhong Plain Shaanxi China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Aerosol pH is not only a diagnostic indicator of secondary aerosol formation, but also a key factor in the specific chemical reaction routes that produce sulfate and nitrate. To understand the characteristics of aerosol acidity in the Mt. Hua, the chemical fractions of water-soluble inorganic ions in the atmospheric PM2.5 and size-resolved particle at the top and foot of Mt. Hua in summer 2020 were studied. The results showed the mass concentrations of PM2.5 and water-soluble ions at the foot were 2.0–2.6 times higher than those at the top. The secondary inorganic ions, i.e., SO42−, NO3−, and NH4+ (SNA) were 56 %–61 % higher by day than by night. SO42− was mainly distributed in the fine particles (Dp 3− showed a unimodal size distribution (peaking at 0.7–1.1 μm) at the foot and a bimodal (0.7–1.1 μm and 4.7–5.8 μm) size distribution at the top. At the top site, the distribution of NO3− in coarse particles (> 2.1 μm) was mainly attributed to the gaseous HNO3 volatilized from fine particles reacting with cations in coarse particles to form non-volatile salts (such as Ca(NO3)2). The pH values of PM2.5 were 2.7 ± 1.3 and 3.3 ± 0.42 at the top and foot, respectively. NH4+/NH3(g) plays a decisive role in stabilizing aerosol acidity. In addition, the increase of the liquid water content (LWC) at the foot facilitates the gas-particle conversion of NH3, while the H+ concentration was diluted, resulting in a decrease in acidity at the foot. NH4+/NH3 had good linear correlations with SO42−, NO3−, and LWC during the daytime at both sites, indicating that SO42−, NO3−, and LWC together affect the gas-particle distribution of ammonia by day: however, the effect of LWC at night was not evident. © 2023

关键词： Ammonia

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Gas‐Liquid Two‐Phase flows Inverse Analysis in An Aeration Tank

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AIP Conference Proceedings 2007年第1期914卷 877-882页

作者： Wen Cheng Zhang‐bin Wang Yuichi Murai Fujio Yamamoto 1State Key Laboratory of Multiphase Flow in Power Engineerig Xi’ann Jiaotong University Xi’an 710049 China 2Environment Research Institute Xian University of Technology Xian 710048 China 3Div. of Mec. Science Graduate School of Engineering Hokkaido University Japan 4Graduate School of Engineering University of Fukui Bunkyo 3‐9‐1 Fukui 910‐8507 Japan

In bubbly two‐phase flow, the gas phase and liquid phase have different flow fields. The mathematical expression for the motion of a small bubble at low Re number has been already established, the liquid velocity along the trajectory of the bubble is calculated inversely by using the motion equation. Whole field liquid flow structure has also estimated using a spatial and/or temporal interpolation method. This paper proposes an algorithm for estimating the liquid phase flow field based on measurement data on bubble data on bubble motion. The applicability of the algorithm is examined with Taylor‐Green vortex flow as an analytical test case. Meanwhile, The result, based on the theory, has been applied to reconstruct liquid phase velocity field by using the data of bubble velocity in an aeration tank.

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A 3d Ptco Degradation Model for Long-Term Performance Prediction of a Scaled-Up Pemfc Under Constant Voltage Operation

SSRN

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SSRN 2023年

作者： Yang, Yunjie Bai, Minli Zhou, Zhifu Wu, Wei-Tao Zhao, Jian Wei, Lei Li, Yang Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Dalian116024 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'An710049 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China Center for Advanced Vehicular Systems Mississippi State University Starkville39762 United States Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen518055 China

The non-uniform distribution of reactants, pressure, temperature, and reaction rate, in a scaled-up proton exchange membrane fuel cell (PEMFC) can lead to different catalyst degradation rate, impacting the long-term performance of PEMFCs. However, the local catalyst degradation behaviors in a PEMFC stack have not yet been fully understood due to the lack of experimental approaches and catalyst degradation model. In the present study, a numerical model is established for a 200 cm2 commercial-sized PEMFC stack with realistic anode and cathode flow fields. PtCo is employed as the cathode catalyst, and a 3D PtCo catalyst degradation model is developed to analyze the non-uniform evolution of the electrochemical active surface area (ECSA), current density, and Co2+ in the catalyst layers under the constant voltage conditions. The modeling results demonstrated that catalyst degradation is more severe downstream as well as under land of the cathode flow field, and the cathode catalyst layer (CCL) is the area most contaminated by the Co2+. The non-uniform catalyst degradation as well as Co2+ contamination increased the activation losses and local oxygen transport resistance. The catalyst degradation leads to a total power loss of 43.3% after 80,000 hours operation. The aging model provides a better understanding for large scale PEMFC stacks regarding its nonuniform PtCo degradation and can assist the future design of commercial PEMFCs with better lifetime. © 2023, The Authors. All rights reserved.

关键词： Proton exchange membrane fuel cells (PEMFC)

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