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19th International Bhurban Conference on Applied Sciences and Technology, IBCAST 2022

作者： Shen, Yi Xu, Xiao Zhang, Jun Zhang, Zhaoming Key Laboratory of Unsteady Aerodynamics and Flow Control Ministry of Industry and Information Technology Nanjing University of Aeronautics and Astronautics Jiangsu Nanjing China School of Mechatronics and Power Engineering Jiangsu Zhenjiang China

ISBN: (数字)9781665460514

ISBN: (纸本)9781665460514

There are serious aerodynamic heating and high resistance phenomena for near space supersonic aircraft. Application of opposing jet flow is an effective technology for drag and heat reduction. This paper uses DSMC method to simulate the external opposite flow of aircraft moving in the supersonic flow in rarefied environment of near space. It analyzes the advantages and disadvantages of drag and heat reduction of opposing jet in the different conditoins by adjusting speeds of the jet in order to obtain an optimized scheme. The numerical results show that the peak values of aircraft surface pressure, surface heat flux and friction are reduced by 76.6%, 93.5% and 50.0% respectively. Application of opposing jet in rarefied environment can effectively reduce the drag and aerodynamic heating for supersonic aircraft. The present study provides an effective reference for the aircraft design on the drag and heat reduction. © 2022 IEEE.

关键词： Supersonic aircraft

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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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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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Experimental exploration of the effect of oxy-fuel combustion on ash deposition behavior of Zhundong high-alkali coal 7

Experimental exploration of the effect of oxy-fuel combustio...

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7th International Conference on power engineering, ICOPE 2019

作者： Sun, Ruijin Wang, Chang'an Zhao, Lei Wang, Chaowei Han, Tao Zhu, Chenzhao Liu, Yinhe Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an710049 China

Zhundong coalfield has a super-large reserve of coal resources. However, its high-alkali feature deteriorates the phenomenon of ash deposition and slagging in coal-fired boilers. Oxy-fuel combustion is a clean and efficient combustion technology, which promotes the efficient and clean utilization of high-alkali coals. While the ash deposition behaviors of high-alkali coals in oxy-fuel case are still unclear. This study compared the differences in morphology and element distribution of ash deposits between air and oxy-fuel conditions to reveal the ash deposition characteristics and mineral migration during oxy-fuel combustion of high-alkali coals. Experimental results showed that the ash deposits were less compact with less floc ash adhering to the ash particles during oxy-fuel combustion compared to air case. Besides, few sulphur, sodium, chlorine and calcium existed in the ash deposits in oxy-fuel combustion, which was constant with the fewer and weaker diffraction peaks of sodium chloride, sodium sulphate, anorthite and mullite under oxy-fuel condition. With the oxygen concentration increased, the intensity of sodium chloride diffraction peak is stronger. © ICOPE 2019 - 7th International Conference on power engineering, Proceedings. All rights reserved.

关键词： Coal

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Catalytic Gasification of Large Particle Size Biomass with Loaded Aaems Under Oxygen-Steam Atmosphere

SSRN

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SSRN 2023年

作者： Ren, Jiyun Yang, Kaixuan Li, Yuhang Bai, Yang Jiang, Jiahao Huang, Xiaole Deng, Lei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China Shanghai Power Equipment Research Institute Co. Ltd. Shanghai200240 China Xi’an Thermal Power Research Institue Co. Ltd. Xi’an710032 China

To evaluate the effect of alkali and alkaline earth metals species (AAEMs) on the catalytic gasification of large particle size biomass, a vertical fixed-bed reactor is conducted for candlenut wood gasification under the oxygen-stream atmosphere. The gasification chars derived from gasification are characterized by SEM, X-ray CT, BET, and FTIR. Tar and syngas are analyzed via GC-MS and GC respectively. Advanced X-ray CT technology provides beneficial visualization to assist in the interpretation of the catalytic gasification of large particle size biomass loaded with AAEMs. The results indicate a progressive augmentation of AAEMs content along the radial direction and end surface for all loaded samples and gasification chars, which could also be visualized from the 3D reconstruction of X-ray CT. Many large pores (40-60 μm) aligned along the grain direction collapse after gasified and generate numerous micropores in gasification chars. 10-20 μm pores are more prominent in chars loaded with KCl and CaCl2. The char loaded with CaCl2 has more well-developed pores, a larger specific surface area, and -OH compounds, aldehydes, ketones and carboxylic acids. The addition of AAEMs facilitates the high generation of M1 compounds (contains 1 benzene ring) in the tar and suppresses the enhancement of other compounds, M4 compounds, and long-chain alkanes. H2 and CO concentrations augments and declines by loading AAEMs. The highest H2 concentration of 62.1% is detected by the addition of CaCl2. When loaded with KCl, the syngas calorific value reduces by 1.37%, while loaded with NaCl, CaCl2, and MgCl2 show an augmentation of 11.48%, 10.56%, and 2.55%, respectively. A decrement of CnHx concentration in syngas derived from samples loaded with KCl and MgCl2 and an increment one loaded with NaCl and CaCl2 are acquired. © 2023, The Authors. All rights reserved.

关键词： Oxygen

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Effects of Combustor Wall Temperature on the Outer Recirculation Zone Combustion Modes Transition in Lean Premixed Dme/Air Swirl Flames

SSRN

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SSRN 2024年

作者： Lin, Wenjun Zhang, Weijie An, Zhenhua Wang, Jinhua Huang, Zuohua Zhang, Huangwei State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Department of Mechanical Engineering National University of Singapore 9 Engineering Drive 1 Singapore117576 Singapore Department of Mechanical Engineering and Science Kyoto University Kyoto daigakuKatsura Nishikyo-ku Kyoto615-8540 Japan

In this study, the effects of wall thermal conditions on the ORZ combustion modes transition in the DME/air swirl flames are investigated using the Large Eddy Simulation (LES) and Flamelet Generated Manifold (FGM) method. The results show that the ORZ chemistry and temperature are highly sensitive to the wall thermal condition. Based on the correlation between the temperature and species observed in the time-averaged numerical results, the relation between the combustion mode and temperature in the ORZ is discovered. Through temporal analysis of species and heat release rate in the ORZ, the stable Mode II and Mode IV as well as the unstable Mode III are identified. The chemical reaction pathway analysis for typical probe in the ORZ reveals that different combustion modes undergo distinct (lowtemperature or high-temperature) chemical reaction pathways. Afterwards, the definition of combustion modes used in experiments is refined by utilizing the chemical reaction data from the simulations. And it is applied to identify the combustion mode across the entire computational domain. The results confirm the consistency between the combustion modes determined in experiments based on OH and CH2O and those determined in simulations using chemical reaction rates. Finally, this explains the mechanism of the flickering flame in Mode III is the competition between the low-temperature and high-temperature reaction in the ORZ. Whereas the unstable Mode III can be stabilized by changing the wall temperature to reach the Mode II or Mode IV. © 2024, The Authors. All rights reserved.

关键词： Temperature

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