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Visualization investigation of secondary flow on heat transfer deterioration in horizontal heat tube 22

2014 22nd International Conference on Nuclear engineering, ICONE 2014

作者： Wu, Chao Li, Hui-Xiong Qian, Zhang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi China

ISBN: (纸本)9780791845905

Mixed convection heat transfer in heated tubes has been studied extensively in the past decades, which is widely used in various industrial fields such as cooling of a nuclear reactor core. The secondary flow, which is induced by buoyancy force, has been found in previous research to have profound influence on the heat transfer difference on circumferential position and occurrence of heat transfer deterioration in horizontal heated channel. Therefore, understanding the secondary flow velocity field has important implications to prevent heat transfer deterioration and ensure the safe operation of nuclear power plants. Numerical methods have been adopted in literature to analyze the complex interaction between secondary flow and heat transfer deterioration. However, to the knowledge of the author, experimental measurement of secondary flow in the radial cross-section of a horizontal tube does not exist.. Copyright © 2014 by ASME.

关键词： Numerical methods

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Dynamic performance analysis of different schemes of solar tower power plant

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

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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

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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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Flame-front instabilities of outwardly expanding isooctane/ n -butanol blend-air flames at elevated pressures

Flame-front instabilities of outwardly expanding isooctane/ ...

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作者： Zhang, Xinyi Tang, Chenglong Yu, Huibin Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

Experiments were conducted in a constant volume bomb filled with isooctane/n-butanol blend-air mixtures over a wide range of n-butanol blending ratios, equivalence ratios, and initial pressures. High-speed schlieren photography was used to measure the critical radius for the onset of flame-front instability. Results show that, for a given n-butanol blending ratio, cellular instabilities appear earlier and the critical Peclet number, which represents the onset of instability, is decreased with the increase of the initial pressure and equivalence ratio. Under fuel-rich conditions, the critical Peclet number increases with the increase of the n-butanol blending ratio. Theoretical calculation of the critical Peclet number was also conducted to interpret the effects of n-butanol on the flame-front instabilities of the blends. Results show that, for rich mixture conditions, with the increase of the n-butanol blending ratio, the overall activation energy of the mixtures is decreased and, thus, the thermal-diffusional instabilities are suppressed. While under fuel-lean conditions, the thermal-diffusional instabilities are favored. As a consequence, with an increasing n-butanol blending ratio, the critical Peclet number is expected to be decreased under fuel-lean conditions and increased under fuel-rich conditions. © 2014 American Chemical Society.

关键词： Mixtures

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Study on Venturi nozzle for gas-liquid two-phase flow metering

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Journal of Harbin Institute of Technology(New Series) 2012年第1期19卷 107-110页

作者：梁法春张修刚王栋林宗虎 College of Pipeline and Civil Engineering China University of Petroleum State Key Lab of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Experiments were carried out to study gas-liquid two-phase flow through a horizontally mounted Venturi nozzle. The inner diameter of pipe is 25 mm and the throat diameter of Venturi nozzle is 5. 1 mm. The pressure difference and pressure loss across the nozzle were measured. It was found that the degree of pressure fluctuation strongly depends on the gas quality. However,the relationship between the standard deviation of pressure difference and the gas quality is not monotonous. Multiple solutions may occur when the relationship was used to determine gas quality. On the other hand,the standard deviation of pressure loss was found to be monotonously correlated to X. This phenomenon was applied to measured gas quality. Also a modified Lin's equation is proposed to calculate the two-phase flow rate. The experimental measurements agree well with the predicted values.

关键词： two-phase flow Venturi nozzle flow measurement

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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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Modeling and dynamic simulation on a three-stage feedwater heater with water level controlled

Modeling and dynamic simulation on a three-stage feedwater h...

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International Conference on power engineering, ICOPE 2015

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

Consisting of steam cooler, condensation zone and drain cooler, the three-stage feedwater heater is widely used in the thermal power plants. To study the variable condition characteristics of three-stage feedwater heater with water level controlled, a GSE simulation model of that in 300MW thermal system of power plant was established. Validated by the steady states of the heater, different dynamic characteristics were investigated when the load varied. The results revealed that the steam pressure, feedwater flow and feedwater inlet temperature drops would have a significant influence on the extracting steam flow, feedwater temperature increment and terminal temperature difference. The dynamic trends were intensified with the variation of the input condition enhanced. The response time of extracting steam pressure drops is 430s and that of feedwater flow drops would be prolonged to 600s. The dynamic processes with water level controlled were carried out and showed that adjusting flow valve could keep the water level stable and secure the operation of heater smooth and steady. However, frequently controlling the position of flow valve could impair the steady procedures of other parameters and prolonged the response time. © 2015 The Japan Society of Mechanical Engineers.

关键词： Water levels

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Laminar flame speeds and flame structure of syngas using OH-PLIF

Laminar flame speeds and flame structure of syngas using OH-...

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9th Asia-Pacific Conference on Combustion, ASPACC 2013

作者： Fu, Jin Jing, Wu Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

The effects of flame stretch and hydrogen dynamic stretch on laminar Bunsen flames, especially for the mixture with high H2 fraction, were studied in this paper. OH-PLIF was used to examine the flame reaction zone by visualizing the OH radical concentrated zone. Experiments were conducted at equivalence ratios ranging from 0.5 to 1.6 in the laminar flow range with Reynold's number from 800-2200. H2 fractions in the H2/CO mixture vary from 0.25 to 4.0. Results show that with the increase of H 2 fraction in fuel mixture, the effects of both hydrodynamic stretch and flame stretch are increased. Interpretation on the effect of stretch on flame is provided.

关键词： Mixtures

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Experimental and kinetic study on ignition delay times of 2, 5-DMF/n-heptane blends 9

Experimental and kinetic study on ignition delay times of 2,...

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9th International Conference on Modeling and Diagnostics for Advanved Engine Systems, COMODIA 2017

作者： Hu, Erjiang Gao, Zhenhua Ku, Jinfeng Meng, Xin Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Ignition delay times of 2, 5-dimethylfuran(2, 5-DMF)/n-heptane/oxygen/argon mixtures were measured in this study. Experiments were performed at the stoichiometric mixtures in the temperature range of 1200-1800K. A blend model for 2, 5-DMF/n-heptane blends was developed by combining two selected models for each individual fuel component. According to the combined model, the ignition delay time increases with an increase in the 2, 5-DMF addition level, non-linearly. Kinetic analysis was conducted to investigate interaction effects between two fuels. At relatively low blending ratios of 2, 5-DMF, the two fuels have negligible impacts on the reaction path of each other. As the 2, 5-DMF addition increases to relatively higher levels, decomposition path of n-heptane is significantly changed due to the competition for small radical. Copyright © 2017 by the Japan Society of Mechanical Engineers.

关键词： Heptane

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EXPERIMENTAL INVESTIGATION ON THE TRANSCRITICAL DYNAMIC CHARACTERISTICS OF WATER WALL FOR A SUPERCRITICAL CFB BOILER

EXPERIMENTAL INVESTIGATION ON THE TRANSCRITICAL DYNAMIC CHAR...

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ASME 2024 International Mechanical engineering Congress and Exposition, IMECE 2024

作者： Yang, Dong An, Ning Du, Xiaocheng Han, Lei Guo, Zerui Wei, Ziyu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi Xi'an China

ISBN: (纸本)9780791888667

When the boiler load varies, the operational parameters in the water wall will change, this process is called as dynamic process. Dynamic process presents unique flow and heat transfer phenomena within the water wall. To investigate the process, the research was conducted in a vertical upward smooth tube for a supercritical circulating fluidized bed (CFB) boiler. Experiments were conducted to explore the dynamic characteristics during transcritical pressure process. The results indicate that as system pressure decreases from 23 MPa to 21 MPa, the mass flux within the tube increases sharply, and the outlet fluid temperature decreases. Concurrently, a rapid rise in wall temperature was observed. As the inlet mass flux increases, the wall temperature eventually returns to the normal value. The dynamic heat transfer coefficients were calculated throughout the transcritical pressure process, revealing stages of heat transfer deterioration, subcooled boiling, and single-phase water heat transfer. In addition, experiments and numerical simulations were carried out to explore the dynamic characteristics at supercritical pressure. The dynamic response curves during the step process of heat flux and inlet enthalpy under supercritical pressure conditions were obtained. As the inlet enthalpy decreases, the system mass flux increases, and as the heat flux increases, the system mass flux decreases. And there is no rise in wall temperature during the dynamic response at supercritical pressure. Copyright © 2024 by ASME.

关键词： Water tube boilers

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