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Development of a fan-stirred constant volume combustion chamber and turbulence measurement with PIV

Frontiers in Energy 2022年第6期16卷 973-987页

作者： Haoran ZHAO Jinhua WANG Xiao CAI Zhijian BIAN Hongchao DAI Zuohua HUANG State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

A fan-stirred combustion chamber is developed for spherically expanding flames,with P and T up to 10 bar and 473 K,*** characteristics are estimated using particle image velocimetry(PIV)at different initial pressures(P=0.5-5 bar),fan frequencies(ω=0-2000 r/min),and impeller diameters(D=100 and 114 mm).The flame propagation of methanol/air is investigated at different turbulence intensities(u′=0-1.77 m/s)and equivalence ratios(f=0.7-1.5).The results show that u′is independent of P and proportional toω,which can be up to 3.5 m/s at 2000 r/min.L_(T)is independent of P and performs a power regression withω*** turbulent field is homogeneous and isotropic in the central region of the chamber while the inertial subrange of spatial energy spectrum is more collapsed to-5/3 law at a high Re_(T).Compared to laminar expanding flames,the morphology of turbulent expanding flames is wrinkled and the wrinkles will be finer with the growth of turbulence intensity,consistent with the decline of the Taylor scale and the Kolmogorov *** determined S_(L)in the present study is in good agreement with that of previous *** S_(L)and S_(T)of methanol/air have a non-monotonic trend with f while peak S_(T)is shifted to the richer side compared to S_(L).This indicates that the newly built turbulent combustion chamber is reliable for further experimental study.

关键词： fan-stirred combustion chamber turbulence characteristics particle image velocimetry(PIV) methanol turbulent expanding flames

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Optimization of cold-end system of thermal power plants based on entropy generation minimization

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Frontiers in Energy 2022年第6期16卷 956-972页

作者： Yue FU Yongliang ZHAO Ming LIU Jinshi WANG Junjie YAN State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

Cold-end systems are heat sinks of thermal power cycles,which have an essential effect on the overall performance of thermal power *** enhance the efficiency of thermal power plants,multi-pressure condensers have been applied in some large-capacity thermal power ***,little attention has been paid to the optimization of the cold-end system with multi-pressure condensers which have multiple parameters to be ***,the design optimization methods of coldend systems with single-and multi-pressure condensers are developed based on the entropy generation rate,and the genetic algorithm(GA)is used to optimize multiple *** parameters,including heat transfer area of multi-pressure condensers,steam distribution in condensers,and cooling water mass flow rate,are optimized while considering detailed entropy generation rate of the cold-end *** results show that the entropy generation rate of the multi-pressure cold-end system is less than that of the single-pressure cold-end system when the total condenser area is ***,the economic performance can be improved with the adoption of the multi-pressure cold-end *** compared with the single-pressure cold-end system,the excess revenues gained by using dual-and quadruplepressure cold-end systems are 575 and 580 k$/a,respectively.

关键词： cold-end system entropy generation minimization optimization economic analysis genetic algorithm(GA)

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Fluidization of particles in SCW fluidized bed:Voidage distribution of emulsion phase

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Particuology 2022年第4期20卷 60-75页

作者： Hao Wang Youjun Lu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049ShaanxiChina

Supercritical water(SCW)fluidized bed reactors convert biomass to fuels without pollutants *** this work,experimental studies were carried out to investigate voidage distribution in an SCW fu-idized bed by capacitance *** sands with different particle sizes were fluidized by SCW under system pressure of 20-27 MPa and temperature of 410-570℃.The effect of operation conditions on voidage distributions of the emulsion phase(*** voidage and probability density)is discussed.A predicting correlation between voidage and superficial velocity in emulsion phase is *** relative error of the correlation is within+25%.These research results provide useful guidance for the optimization of supercritical water gasification technology.

关键词： Supercritical water fluidized bed Capacitance probe measurement system Voidage distribution

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Evaluation of frictional pressure drop correlations for air-water and air-oil two-phase flow in pipeline-riser system

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Petroleum Science 2024年第2期21卷 1305-1319页

作者： Nai-Liang Li Bin Chen School of Low-carbon Energy and Power Engineering China University of Mining and TechnologyXuzhou221116JiangsuChina State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an710049ShaanxiChina

Accurate prediction of the frictional pressure drop is important for the design and operation of subsea oil and gas transporting system considering the length of the pipeline. The applicability of the correlations to pipeline-riser flow needs evaluation since the flow condition in pipeline-riser is quite different from the original data where they were derived from. In the present study, a comprehensive evaluation of 24prevailing correlation in predicting frictional pressure drop is carried out based on experimentally measured data of air-water and air-oil two-phase flows in pipeline-riser. Experiments are performed in a system having different configuration of pipeline-riser with the inclination of the downcomer varied from-2°to-5°to investigated the effect of the elbow on the frictional pressure drop in the riser. The inlet gas velocity ranges from 0.03 to 6.2 m/s, and liquid velocity varies from 0.02 to 1.3 m/s. A total of885 experimental data points including 782 on air-water flows and 103 on air-oil flows are obtained and used to access the prediction ability of the correlations. Comparison of the predicted results with the measured data indicate that a majority of the investigated correlations under-predict the pressure drop on severe slugging. The result of this study highlights the requirement of new method considering the effect of pipe layout on the frictional pressure drop.

关键词： Frictional pressure drop Pipeline-riser Gas-liquid two-phase flow Severe slugging Correlation

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THERMAL-HYDRAULIC ANALYSIS OF THE COOLING WALL IN ULTRA SUPERCRITICAL COAL-FIRED GENERATION PLANTS DURING DEEP PEAKING

THERMAL-HYDRAULIC ANALYSIS OF THE COOLING WALL IN ULTRA SUPE...

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ASME 2024 Power Conference, POWER 2024

作者： Wang, Dengliang Zhao, Yongliang Chen, Weixiong Wang, Chaoyang Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China

ISBN: (纸本)9780791888186

Due to increasingly severe environmental and climate concerns currently, renewable energy is highly penetrated around the world. However, given the intermittency and instability of renewable energy, coal-fired generation plants urgently need to undertake deep peak shaving tasks, resulting in the frequent load cycling transient processes of units. It will have a significant effect on the safe operation of the boiler components, especially for the hydrodynamic instability of cooling wall within the boiler. This paper takes a 1100 MW ultra-supercritical primary reheat coal-fired generation plants as the research object. In accordance with the heating load distribution characteristics of cooling wall, a hydrodynamic characteristic calculation model of cooling wall within the boiler is constructed based on the mass conservation, momentum conservation and energy conservation equations, which introduces numerous empirical correlations available for heat transfer and hydraulic resistance calculation at the same time. The working fluid temperature in the direction of cooling wall height at 100% THA, 75% THA, 50% THA, 40% THA and 30% THA, as well as the metal temperature of the inner, outer and fin tube walls are analyzed. The changes in metal wall temperature of cooling wall under different load cycling rates are obtained during the low load operating range of 50% THA to 30% THA. Ultimate load cycling rates of the coal-fired generation plants without causing the overtemperature issue of cooling wall is obtained. Finally, when the revised fuel supply control strategy is adopted, it is able to significantly reduce the maximum metal wall temperature during the rapid load cycling process. The maximum load cycling rate is increased from 2.5% Pe/min to 3.0% Pe/min for the loading up process. Copyright © 2024 by ASME.

关键词： Coal

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Formic acid dehydrogenation reaction on high-performance Pd_(x)Au_(1−x) alloy nanoparticles prepared by the eco-friendly slow synthesis methodology

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Frontiers in Energy 2023年第6期17卷 751-762页

作者： Yibo GAO Erjiang HU Bo HUANG Zuohua HUANG State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China Institute of Chemical Engineering and Technology Xi’an Jiaotong UniversityXi’an 712000China

Dehydrogenation of formic acid (FA) is considered to be an effective solution for efficient storage and transport of hydrogen. For decades, highly effective catalysts for this purpose have been widely investigated, but numerous challenges remain. Herein, the Pd_(x)Au_(1−x) (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) alloys over the whole composition range were successfully prepared and used to catalyze FA hydrogen production efficiently near room temperature. Small PdAu nanoparticles (5–10 nm) were well-dispersed and supported on the activated carbon to form PdAu solid solution alloys via the eco-friendly slow synthesis methodology. The physicochemical properties of the PdAu alloys were comprehensively studied by utilizing various measurement methods, such as X-ray diffraction (XRD), N2 adsorption–desorption, high angle annular dark field-scanning transmission electron microscope (HAADF-STEM), X-ray photoelectrons spectroscopy (XPS). Notably, owing to the strong metal-support interaction (SMSI) and electron transfer between active metal Au and Pd, the Pd0.5Au0.5 obtained exhibits a turnover frequency (TOF) value of up to 1648 h−1 (313 K, nPd+Au/nFA = 0.01, nHCOOH/nHCOONa = 1:3) with a high activity, selectivity, and reusability in the FA dehydrogenation.

关键词： FA dehydrogenation face-centred cubic structures PdAu solid solution alloy nanoparticles slow synthesis methodology SMSI effect

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STRESS ANALYSIS AND LIFE ASSESSMENT OF THE STEAM TURBINE ROTOR DURING PEAK SHAVING TRANSIENT PROCESSES

STRESS ANALYSIS AND LIFE ASSESSMENT OF THE STEAM TURBINE ROT...

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ASME 2024 Power Conference, POWER 2024

作者： Fan, Mengyang Zhao, Yongliang Liu, Ming Wang, Chaoyang Wang, Zhu Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China

ISBN: (纸本)9780791888186

To achieve the net-zero emissions targets, the global share of renewable energy is rapidly increasing. The high penetration of intermittent and variable renewable power necessitates that coal-fired power plants enhance their operational flexibility for peak shaving and frequency regulation. Frequent and rapid start-ups, shutdowns, and peak shaving processes pose significant safety challenges to the steam turbine rotors. This paper investigates the impact of flexible operation on rotor stress. Firstly, an online monitoring model was developed and verified using a finite element model of a steam turbine high-medium pressure rotor. Secondly, the online calculation model was integrated with a dynamic coal-fired unit model developed using the JTopmeret software on the GSE platform, a well-established dynamic simulation tool for nuclear and fossil fuel power plants. Finally, a rotor low-cycle fatigue life assessment model was developed, and the von Mises stress and fatigue life loss under various load variation rates and ranges were determined. As the load variation rate increases, the life loss increases significantly, with maximum von Mises stress amplitudes of 5.2, 6.5 and 7.8 MPa at 1%, 2% and 3% Pe min−1 load variation rates, respectively. Conversely, as the load variation range increases, the life loss decreases substantially, with maximum von Mises stress amplitudes of 9.2 and 5.0 MPa during load variation processes of 50%-75% and 75%-100% THA, respectively. This study provides detailed guidance for optimizing the safe operation and control strategies of coal-fired power plants. Copyright © 2024 by ASME.

关键词： Steam turbines

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THE FLEXIBILITY ENHANCEMENT OF SUBCRITICAL COAL-FIRED POWER PLANTS: CONTROL STRATEGY OPTIMIZATION FOR LIVE AND REHEAT STEAM TEMPERATURE

THE FLEXIBILITY ENHANCEMENT OF SUBCRITICAL COAL-FIRED POWER ...

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ASME 2024 Power Conference, POWER 2024

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

ISBN: (纸本)9780791888186

With the increasing penetration of renewable power, flexible power sources are urgently required by the power grid to balance the supply and demand sides. Therefore, the operational flexibility of subcritical coal-fired power plants should be further enhanced. In this study, dynamic models of a reference 330MW subcritical coal-fired power plant were developed and validated. The load ramp performances of the reference plant were simulated. The maximum ramp rates during loading down processes were 2%Pe/min and 1.5%Pe/min in 75% -50% and 50% -40% load cycling ranges, respectively, and the maximum ramp rate during loading up processes is 1.5%Pe/min. That the live steam and reheat steam temperatures exceeding their thresholds limits for the load ramp rates. The subcritical power unit has a steam drum, serving as a substance and energy storage device, and allows partial decoupling of feedwater flow and coal flow. Consequently, an enhanced steam temperature control strategy, facilitated by adjusting the feedwater flow rate during the load ramp processes, was proposed. The feedwater flow rate is appropriately regulated during load cycling dynamic processes to assist the control of live steam and reheat steam temperatures. The models to obtain the live steam and reheat steam temperature variations influenced by the feedwater flow rates are developed, and implemented in the control strategy. Then, simulations on the reference power plant with the enhanced control strategy were conducted, and the temperature overshoots have been effectively suppressed. As a result, the load ramp rate is increased. For example, in the load cycling range of 75%-40%, the overall unit ramp rate is increased by 1%Pe/min, achieving an enhancement in the operational flexibility of subcritical units. Copyright © 2024 by ASME.

关键词： Coal

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Effect of Particle Orientation on Heat Transfer in Arrays of Prolate Particles

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Computer Modeling in engineering & Sciences 2023年第8期136卷 1509-1526页

作者： Romana Basit Xinyang Li Zheqing Huang Qiang Zhou School of Chemical Engineering and Technology Xi’an Jiaotong UniversityXi’anChina State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’anChina

Direct Numerical Simulations have been carried out to study the forced convection heat transfer of flow through fixed prolate particles for a variety of aspect ratios ar={5/4,5/3,5/1}with Reynolds number(Re)up to *** variations of the solid volume fraction c={0.1,0.2,0.3}with four Hermans orientation factors S={−0.5,0,0.5,1}are *** has been found that changes in S cause prominent variations in the Nusselt *** general,Nusselt number increases with the decrease of *** all three aspect ratios,the Nusselt number remains a linear function of S at different c and ***,it is concluded that,for heat transfer from prolate muti-particle system,the effects of orientations cannot be ignored.A new correlation for Nusselt number has been developed for arrays of prolate particles using the simulation data as a function of Re,c,S and ar.

关键词： Direct Numerical Simulation heat transfer lattice Boltzmann method particle orientations prolate particles

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Particle convective heat transfer near the wall in a supercritical water fluidized bed by single particle model coupled with CFD-DEM

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Particuology 2023年第2期73卷 47-58页

作者： Tianning Zhang Zhen Wan Youjun Lu State Key Laboratory of Multiphase Flow in Power Engineering(SKLMFPE) Xi'an Jiaotong UniversityXi'an710049ShaanxiChina Xi'an Electronic Engineering Research Institute Xi'an710100ShaanxiChina

Supercritical water fluidized bed(SCWFB)is a promising reactor to gasify biomass or *** optimization design is closely related to wall-to-bed heat transfer,where particle convective heat transfer plays an important *** paper evaluates the particle convective heat transfer coefficient(h_(pc))at the wall in SCWFB using the single particle *** critical parameters in the single particle model which is difficult to get experimentally are obtained by the computational fluid dynamics-discrete element method(CFD-DEM).The contact statistics related to particle-to-wall heat transfer,such as contact number and contact distance,are also *** results show that particle residence time(τ),as the key parameter to evaluate h_(pc),is found to decrease with rising velocity,while increase with larger thermal boundary layer thickness.τfollows a gamma function initially adopted in the gas-solid fluidized bed,making it possible to evaluate h_(pc) in SCWFB by a simplified single particle *** theoretical predicted h_(pc) tends to increase with rising thermal gradient thickness at a lower velocity(1.5 U_(mf)),while first decreases and then increases at higher velocity(1.75 and 2 U_(mf)).h_(pc) occupies 30%-57%of the overall wall-to-bed heat transfer coefficient for a particle diameter of 0.25 *** results are helpful to predict the overall wall-to-bed heat transfer coefficient in SCWFB combined with a reasonable fluid convective heat transfer model from a theoretical perspective.

关键词： Supercritical water Fluidized bed Particle residence time Discrete element method Single particle model

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