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SSRN 2024年

作者： Yang, Yunjie Bai, Minli Zhou, Zhifu Wu, Wei-Tao Lv, Jizu Hu, Chengzhi 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 School of Mechanical Engineering Guangdong Ocean University Zhanjiang524088 China

While reducing the size and Pt loading can achieve a lower proton exchange membrane fuel cell (PEMFC) stack cost, it is also very important to focus on the performance changes of the PEMFC stack during the long-term operation. A 3D PtCo catalysts long-term performance model is established in this study, and PEMFC stacks with one cooling unit per cell (1-cell stack) and three cells (3-cell stack) are employed as the computational domains, respectively. The effective area of each cell is 50 cm2, and the changes in current density as well as effective catalytic area of PEMFC stacks with two cooling strategies before and after long-term operation under different humidity conditions are investigated at low Pt loadings. The results show that there are large differences in the output voltage and current density distributions between the three cells due to the poor membrane hydration affected by the non-uniform temperature distribution, although the 3-cell stack can significantly reduce the size. Localized catalyst degradation in both 3-cell and 1-cell stacks is closely related to the geometry of the cathodic flow field, and non-uniform catalyst degradation is found to increase the activation and mass transfer losses and change the distribution of current density within the membrane. In addition, the 3-cell stack is found to perform even better in terms of durability, especially under high humidity conditions, which provides a potential solution to improve the durability of PEMFC stacks operating in harsh conditions. © 2024, The Authors. All rights reserved.

关键词： Durability

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Selectivity catalytic reduction of NO by CO over Fe-Cu oxides supported on rice hull Ash(Rha) 7

Selectivity catalytic reduction of NO by CO over Fe-Cu oxide...

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7th International Conference on power engineering, ICOPE 2019

作者： Teng, Zhaohui Fu, Liang Li, Na Zhou, Qulan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xian710049 China

The present work contains the studies of catalytic reduction of NO with CO over 20 wt.% bimetallic Fe-Cu transition metal oxides supported on rice hull ash (RHA) and γ-Al2O3, which were prepared by various procedures. All catalysts contained CuO and Fe2O3 alongside with CuFe2O4. The catalytic activity kinetics for NO and CO reduction reaction mechanism was obviously improved over the synthesized RHA when compared to alumina support. And bimetallic metal catalyst Fe2Cu1/RHA demonstrated a high conversion of NO at all the temperatures examined. This was due to the strong interaction of Cu-Fe with the amorphous silica and activated carbon in RHA and high dispersion on the supporter. NO was almost reacted to N2 over Fe2Cu1/RHA from room temperature to 500℃ and O2 has little influence on it in our experiment conditions. About 100% CO was oxidized after 150℃ over Fe2Cu1/RHA. All the materials showed an unchanged stability over the period of 20h. Metallic copper and iron were the active species. The present results suggest that bimetallic Fe-Cu transition metal oxides supported on rice hull ash (RHA) can be used as an applicable catalyst to selectively reduce NO and CO. © ICOPE 2019 - 7th International Conference on power engineering, Proceedings. All rights reserved.

关键词： Reduction

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Studies on high temperature corrosion behavior of water wall materials under cyclic temperature 7

Studies on high temperature corrosion behavior of water wall...

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7th International Conference on power engineering, ICOPE 2019

作者： Liu, Zhuhan Wu, Zhengyu Li, Na Zhou, Qulan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

In this study, the corrosion behavior of water wall materials under cyclic temperature was studied. Corrosion products (XRD and EDS), corrosion morphology (SEM detection) and corrosion effects on residual matrix metal (SEM detection) were compared after different corrosion times to obtain the corrosion behavior under cyclic temperature conditions. There is no significant difference between the corrosion products of the sample at the circulating temperature and the corrosion products at the constant temperature. The corrosion surface layer is iron oxide, but according to the cross-sectional morphology it can be clearly observed that under the cyclic temperature condition, there is a certain increase in the corrosion layer thickness and the corrosion scales is broken with less protection. As the composition of T23, Cr didn't participate in the corrosion reactions to form a protective Cr2O3 protective layer, which is different in other materials. © ICOPE 2019 - 7th International Conference on power engineering, Proceedings. All rights reserved.

关键词： High temperature corrosion

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Experimental study on preparation of amorphous SiO2 by fluidized bed combustion of rice husk 7

Experimental study on preparation of amorphous SiO2 by fluid...

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7th International Conference on power engineering, ICOPE 2019

作者： Yao, Yashu Xu, Heng Tan, Jingkao Hu, Zhengtao Zhou, Qulan Li, Na State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

The rice husk ash (RHA) contains a large amount of amorphous silica having a large specific surface area and high activity, but after combustion of the rice husk the SiO2 is easily crystallized, which deteriorate the performance. Therefore, it is necessary to study the crystallization process of silica in combustion for the preparation of excellent rice husk ash. On the self-built fluidized bed experimental system, the combustion characteristics of rice husk and the pore characteristics of RHA under different excess air coefficients were studied. It was found that when the excess air ratio was between 0.8 and 0.9, the silica remained unchanged, and the specific surface area of rice husk ash is larger. Meanwhile, the furnace temperature is higher, which is conducive to the utilization of heat;when the excess air ratio is greater than 1, the crystallization of rice husk ash is more serious. In conclusion, it should be burned when the excess air ratio is less than 1 in order to prepare RHA with large specific surface area by direct combustion method. © ICOPE 2019 - 7th International Conference on power engineering, Proceedings. All rights reserved.

关键词： Silica

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Ventilation and cooling of wind generator: A numerical study and experimental verification 7

Ventilation and cooling of wind generator: A numerical study...

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7th International Conference on power engineering, ICOPE 2019

作者： Ao, Yunjin Li, Na Zhou, Qulan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

In the wind generator, a large amount of heat is generated during the operation, which usually causes severe temperature rise and decrease of efficiency. By coupling fluid dynamics and heat transfer, a numerical method has been developed to calculate the velocity filed and temperature distribution of a common air-cooled doubly-fed wind generator. The numerical results have been verified by the experiments. The results show that the flow resistance is higher in the center in the axial direction, thus the temperature is much higher than the ends. In the height direction, there locate the most dangerous points and the temperature rise is about 110K. In the circumference direction, there are regularity of fluctuation and can assist in finding the dangerous points. The variations of heat source and cooler power as well as rotation speed all affect the temperature rise of the generator. The regularity and method of this study can be applied to similar generators or generators of other forms, thus advice can be given for the design, manufacture, operation and maintenance of wind generators. © ICOPE 2019 - 7th International Conference on power engineering, Proceedings. All rights reserved.

关键词： Temperature distribution

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Thermo-economic optimization of the dual-pressure condenser for 700 °C ultra-supercritical coal-fired power plants

Thermo-economic optimization of the dual-pressure condenser ...

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2019 Canadian Society for Civil engineering Annual Conference, CSCE 2019

作者： Fu, Yue Liu, Ming Wang, Liyuan Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

ISBN: (纸本)9780791883747

Pulverized coal power is one of major contributor in power production, whose efficiency can be enhanced by increasing the main steam parameters and adjusting the cold end system parameters. The thermo-economic optimization of the cold end system for 700 °C ultra-supercritical coal-fired power plants were carried out in this study. The condenser pressure was thermoeconomically optimized for the single-pressure condenser systems. Then, with the same heat transfer area of the optimized single-pressure condenser, the dual-pressure condenser system was thermo-economically optimized. The distributions of heat transfer area and exhaust steam mass flow between the highpressure and low-pressure chambers in the dual-pressure condenser system were optimized. The results show that the optimal vacuum pressure of the single-pressure condenser is 3 kPa and the optimal heat transfer area is 27 km2. For the dualpressure condenser system, the cost of dual-pressure condenser is reduced to the minimum value 1.3 million CNY/year. The power plant efficiency is increased by the maximum value 0.1% when the heat transfer area and exhaust steam mass flow rate are distributed equally between two chambers, compared with that of the single-pressure condenser system. The optimal values of the low-pressure and high-pressure chamber are 2.4 kPa and 3.2 kPa, respectively. This paper provides the reference for the design optimization of cold end system for high parameter power units. Copyright © 2020 ASME.

关键词： Coal fired power plant

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Onset of slugging fluidization in supercritical water fluidized bed

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Particuology 2020年第5期18卷 47-56页

作者： Hao Wang Jikai Huang Youjun Lu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049ShaanxiChina Energy Research Insatute Qilu University of Technology(Shandong Academy of Sciences)Jinan 250014ShandongChina

The supercritical-water fluidized bed(SCWFB)is a reactor for coal and biomass gasification without pollutant *** carried out a series of experiments in a SCWFB,and a dual-capacitance probe measurement system was applied to measure the hydrodynamics of slugs,such as the slug frequency,chord length,and rising *** groups of Geldart-B particles with different mean diameters were fluidized by supercritical water with a system pressure of 20-27MPa and at 410-570℃.The minimum slugging Reynolds number increases logarithmically with Archimedes number and a predicting correlation of the minimum slugging fluidization velocity in the SCWFB is presented:Rems=32908.84 ln(Ar^0.55+260376.65)-*** relative error of the above correlation was within ±15% and the averaged relative error was 7.5%.The effect of operating conditions on the minimum slugging fluidization velocity is *** research provides useful guidance for scaling-up design and for determining the optimum range of operating conditions in the SCWFB.

关键词： Supercritical water fluidized bed Slugging fluidization Dual-capacitance probe method

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Numerical Simulation of Unsteady flow Control Mechanism of Attached Stationary Or Vibrating Small Cylinder On a Main Cylinder

SSRN

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SSRN 2022年

作者： Huang, Shengxian Hu, Yu Wang, Ying Shanghai key laboratory of multiphase flow and heat transfer of power engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai China National Key Laboratory of Science and Technology on Aerodynamic Design and Research Xi’an710072 China

The phenomena of flow separation and vortex shedding after bluff body are the key to the safety of offshore engineering. To deepen the understanding of the relevant physical mechanism of wake vortex control of the non-equal diameter double cylinder model, simulation was conducted when Re=200 using the SST k-ω turbulence model. The effects of different diameter ratios, position angle, and gap ratio between the double cylinder model on the flow pattern, surface pressure, and wake characteristics of the main cylinder are investigated. Four different forced vibration forms are applied to the small cylinder with the optimum arrangement area, and their influence on the hydrodynamic characteristics of the main cylinder is analyzed. The results show that the main cylinder's vortex shedding and aerodynamic characteristics can be effectively improved by the small auxiliary cylinder arranged in the near wake region of the main cylinder, and there is an optimal position for the small cylinder. In addition, the vibration of the small auxiliary cylinder in the wake area will cause the locking area of the main cylinder and the side vortex shedding on the main cylinder can be better suppressed by using the auxiliary vibration small cylinder with a suitable frequency ratio. © 2022, The Authors. All rights reserved.

关键词： Vortex shedding

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Experimental investigation of heat transfer characteristics of supercritical water in the entrance region of vertical upward tube 7

Experimental investigation of heat transfer characteristics ...

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7th International Conference on power engineering, ICOPE 2019

作者： Kong, Xiangfei Zhang, Qian Guo, Kaikai Feng, Yuan Lei, Xianliang Li, Huixiong State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

In order to investigate the special heat transfer characteristics of supercritical water in the entrance region, series of experiments have been conducted in 3-m and 6-m long vertical upward tubes with 20.0-mm internal diameter. The experimental parameters cover the pressures from 22.5 to 27 MPa, the mass fluxes from 150 to 600 kg/(m2·s), and the heat fluxes from 50 to 500 kW/m2. Enhanced heat transfer (EHT) was observed at the inlet of the test sections which was different from the EHT occurred near the pseudo-critical point. Deteriorated heat transfer (DHT) was also observed at the inlet of the test sections under high q/G conditions. It was found that the inlet bulk fluid enthalpy could affect the occurrence and the degree of DHT at the inlet of the test section. DHT disappeared when the inlet bulk fluid enthalpy exceeded the pseudo-critical enthalpy. Finally, the mechanisms of the EHT and DHT occurred at the inlet of test section were analyzed. © ICOPE 2019 - 7th International Conference on power engineering, Proceedings. All rights reserved.

关键词： Heat transfer

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Study on basic coal consumption characteristics in dynamic process of 660MW ultra-supercritical coal-fired unit

Study on basic coal consumption characteristics in dynamic p...

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2019 Canadian Society for Civil engineering Annual Conference, CSCE 2019

作者： Yin, Junjie Liu, Ming Yan, Junjie Zhao, Yongliang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi China

ISBN: (纸本)9780791883747

With the spreading of intermittent renewable power, coalfired power units should cycle frequently to balance the load between power supply side and demand side. Coal consumption of coal-fired units operating in dynamic processes is influenced by many factors, including thermal system, control system, heat storage variation, etc. Therefore, it is very difficult to evaluate the energy efficiency of coal-fired units operating in dynamic processes. It is important to ascertain the basic coal consumption rate in dynamic processes, which is the basis to evaluate the operation performance of coal-fired units. In this study, an off-design calculation model of 660MW ultra-supercritical coal-fired unit is developed and validated with design parameters. The developed model can be used to predict the coal consumption rates under steady-state off-design conditions. The basic coal consumption means the coal consumption of coal-fired units with operating parameters the same as target values. To calculate the basic coal consumption rate, a load cycling process is differentiated into lots of short time periods and every period is regarded as a steady-state condition with constant load, therefore the coal consumption rates in every period are equal to that of the corresponding steady-state condition. The calculation formula of basic coal consumption rates in is derived for load cycling processes. On the basis of the off-design calculation model and assumption of idealized condition, average coal consumption rates during different processes with constant load cycling rates can be calculated and analyzed. Results show that if the initial and final loads are both settled, the basic coal consumption rate remains unchanged and is independent of load cycling rate. If the load cycling amplitude remains unchanged, the basic coal consumption rate increases as the initial load decrease. The study aims to provide benchmark values for the energy consumption analysis in actual dynamic processes,

关键词： Energy efficiency

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