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Building Simulation 2021年第3期14卷 523-533页

作者： Long Gao Gegentana Junchao Bai Baizhong Sun Deyong Che Shaohua Li School of energy and power Engineering Northeast Electric Power UniversityJilin 132012China

The goal of this study is to investigate the effect of key design parameters on the thermal performance of the packed bed heat storage device by numerical calculation.A one-dimensional,non-equilibrium packed bed latent heat storage mathematical model was established and the applicability of the model was *** results demonstrate that the inlet temperature of the heat transfer fluid(HTF)had the greatest influence on each *** the inlet temperature increased from 333 K to 363 K,exergy destruction increased threefold,effective heat storage time decreased by 67%,effective heat storage increased by 38%,and exergy efficiency decreased by 11%.The decrease of the capsule diameter had a positive effect on each evaluation *** to the sensitivity analysis,the order of importance of each parameter within their variation range was HTF inlet temperature,HTF flow rate,PCM capsule size and PCM initial temperature.

关键词： packed bed thermal energy storage solar heating system performance evaluation parametric analysis

Numerical Investigation on Characteristics of Supercritical CO_(2)Heat Transfer in Vertical Circular Tubes with Circumferentially Half-Side Heating

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Journal of Thermal Science 2024年第5期33卷 1744-1756页

作者： ZHANG Yan ZHANG Xinyi YAN Chenshuai WU Wenhua GAO Erman School of energy and power Engineering Northeast Electric Power UniversityJilin 132012China

The design of heat exchangers in the advanced supercritical power conversion system cannot be separated from the study of heat transfer ***-side heating mode is often encountered for solar receiver and supercritical ***,the characteristics of supercritical CO_(2)(sCO_(2))convection heat transfer in vertical tubes with circumferentially half-side heating was numerically investigated through the SST k-ωturbulent model which matches well with the experimental ***,heat transfer between sCO_(2)upflow and downflow was *** to film boiling heat transfer at subcritical pressure,numerical results were processed according to the supercritical pseudo-phase transition hypothesis,with liquid-like phase in the tube core region and vapor-like film in the region near the heated tube *** structure of two layers was demarcated by pseudo-critical temperature T_(pc).Therefore,sCO_(2)heat transfer was assessed according to double thermal resistances caused by vapor-like film near the wall and core liquid-like *** findings suggest that wall temperature for upflow is higher than that for downflow,which is attributed to larger thermal resistance in the fluid domain for upflow than that for *** difference guarantees the excellent heat transfer performance for downflow than *** is also further concluded that the formation of vapor-like film near the wall due to pseudo-phase transition plays a key role in dominating wall temperature and inducing heat transfer deterioration in half-side heating *** present contribution is significant to the design of supercritical heat exchanger under half-side heating mode.

关键词： supercritical CO_(2) pseudo-phase transition half-side heating thermal resistance flow direction

Performance Analysis of Thermal energy System with Linear System Method

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Journal of Thermal Science 2007年第3期16卷 231-236页

作者： Liping LI Chunfa ZHANG School of energy and power North China Electric Power University Baoding 071003 China

The paper addresses the system performance of coal-fired power unit with changed auxiliary system or other local heat disturbance. The idea of state space model is imported and the universal formula for the calculation of system performance output is deduced on the system state equation. Two important vector of system are worked out under linear system assumption and transform. The transfer matrix is the characteristics of system itself and is constant for a similar condition, which greatly facilitates the analysis. The concept of thermal disturbance vector is proposed to construct the thermal disturbance input easily. The method can be helpful for analyzing any thermal disturbance input satisfying the assumption and also for supplementing the correction means of performance test. An example of 600MW power unit is presented to demonstrate its availability.

关键词： matrix vector power unit performance linear system method thermodynamic analysis.

Effect of Rotor-stator Axial Gap on the Tip Seal Leakage Flow of a Steam Turbine

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Journal of Thermal Science 2021年第3期30卷 973-982页

作者： LI Pan CAO Lihua School of energy and power Engineering Northeast Electric Power UniversityJilin 132012China

The tip leakage flow in different axial gaps is numerically investigated based on the Reynolds-Averaged Navier-Stokes equations and k-ω SST turbulent model using commercial CFD software ANSYS *** characteristics of vortexes in the flow field of tip seal and the distribution law of rotor tip leakage loss are analyzed under the change of axial *** results show that the flow field in the blade tip seal undergoes complex changes with the increase of axial *** are two opposite vortices in the seal cavity with small axial gap,namely,the large vortex in the cavity and the small vortex near the wall of the *** small vortex gradually disappears with the increase of the axial *** the axial gap is increased to a certain value,the reverse large vortex is formed in the cavity behind the low teeth of seal,and the leakage rate increases significantly;the steam flow angle and the mixing loss also show different *** on the traditional calculation formula of tip leakage rate,a more accurate calculation formula of tip leakage rate is constructed by introducing equivalent labyrinth seal teeth to consider the variation of axial gap.

关键词： steam turbine axial gap tip leakage labyrinth seal prediction formulation

Structures and Magnetic Properties of Europium-Transition Metal-Gallium Ternary Intermetallic Compounds with 1:3 Type

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Chinese Physics Letters 2015年第1期32卷 158-161页

作者：何强郭永权 School of energy power and Mechanical Engineering North China Electric Power University

The crystal structures and magnetic properties of novel Eu TrGa3-r （T=Pd, It, Rh） in termetallic compounds are investigated by using powder x-ray diffraction and magnetic measurements. EuTrGa3-r crystallizes in orthorhombic structure with space group of Cmcm and Z = 4. There are four kinds of nonequivalent 4c crystal positions in EuTrGaa-r unit cell, which are occupied by 4Eu, 4GaⅠ, 4（GaⅡ, T） and 4GaⅢ, respectively. EuTrGa3-r ex- hibits the complex magnetic states in low-temperature regime, with the three-, two- and one-antiferromagnetic transitions occurring for T=Ir, T=Rh and T=Pd, respectively. It might be due to the Kondo effect： a localized antiferromagnetic interaction of the isolated impurity spins with the surrounding conduction electrons at low-temperature regime.

关键词： Pd Ga Structures and Magnetic Properties of Europium-Transition Metal-Gallium Ternary Intermetallic Compounds with 1 Type Eu

Crystal structure and magnetic properties of disordered alloy ErGa3-xMnx

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Chinese Physics B 2019年第8期28卷 241-245页

作者： Cong Wang Yong-Quan Guo Shuo-Wang Yang School of energy power and Mechanical Engineering North China Electric Power University

ErGa3-xMnx disordered alloy is successfully prepared by the vacuum arc melting technology,and the crystal structure and magnetic properties are investigated by using the x-ray diffraction and magnetic *** Rietveld structural analysis indicates that the ErGa3-xMnx crystallizes into a cubic structure with space group of Pm3m in Mn doping range of x=***,the disordered alloy with structural formula of Er0.8Ga2^Ⅰ(Ga^Ⅱ,Mn)0.4 as the second phase is separated from cubic phase for the samples with x=0.2 and 0.3,which is induced by substituting the(Ga^Ⅱ,Mn)-(Ga^Ⅱ,Mn)pair at 2e crystal position for the rare earth Er at 1 a *** lattice parameters tend to increase with Mn content increasing due to the size effect at Ga(1.30A)site by substituting Mn(1.40A)for *** paramagnetic characteristic is observed by doping Mn into ErGa3 at room *** Mn content increasing from x=0 to 0.1,the magnetic susceptibilityχtends to *** phenomenon can be due to the increase of effective potential induced by doping Mn into ***,the magnetic susceptibilityχcontinues to decrease with the increase of Mn content in a range of x>0.2,which is due to the phase separation from the cubic Er(Ga,Mn)3 to the hexagonal Er0.8Ga2(Ga,Mn)0.4.

关键词： ErGa3-xMnx Rietveld structure refinement magnetic transport

Cylindrical bubble dynamics in triple-frequency acoustic field

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Journal of Hydrodynamics 2024年第5期36卷 947-953页

作者： Jia-xin Yu Zhi-hao Liu Jin-sen Hu Xiao-yu Wang Xiang-qing Zhang Jun-wei Shen Yu-ning Zhang Key Laboratory of power Station energy Transfer Conversion and System(Ministry of Education) School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing102206China

In this paper,the dynamic characteristics of the cylindrical bubbles under triple-frequency acoustic excitation are investigated *** analytical solution of the primary-superharmonic-subharmonic(PRI-SUPER-SUB)simultaneous resonance is obtained through the multi-scale *** on the analysis of the frequency response,the influencing mechanisms of the primary parameters(e.g.,the total amplitude,amplitude ratio,liquid viscosity,polytropic exponent,and bubble equilibrium radius)on the resonance are investigated *** main conclusions include:(1)The solution for the simultaneous resonance of the cylindrical bubble exhibits jumping and hysteresis phenomena in the vicinity of the resonance frequency.(2)As the total amplitude,amplitude ratio,and equilibrium radius increase,the response amplitude of the PRI-SUPER-SUB simultaneous resonance increases,while the influence of the viscosity is the opposite.(3)The regions dominated by the instability of the simultaneous resonance is significantly affected by the system parameters.

关键词： Cylindrical bubble dynamics simultaneous resonance multi-scale method frequency response

De-noising of radiation pressure signal generated by bubble oscillation based on ensemble empirical mode decomposition

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Journal of Hydrodynamics 2022年第5期34卷 849-863页

作者： Xiang-hao Zheng Yu-ning Zhang Key Laboratory of power Station energy Transfer Conversion and System(Ministry of Education) School of EnergyPower and Mechanical EngineeringNorth China Electric Power UniversityBeijing102206China

The radiation pressure signals generated by the bubble oscillation are often utilized to recognize the characteristics of the target objects in many ***,these signals are easily contaminated by complex background *** order to accurately extract the effective components of the radiation pressure signal generated by the bubble oscillation,this paper proposes a de-noising procedure for the radiation pressure signal,based on the ensemble empirical mode decomposition(EEMD),the autocorrelation function and the modified wavelet soft-threshold de-noising *** order to verify the effectiveness of the procedure,the typical radiation pressure signal generated based on the Keller-Miksis model under the acoustic excitation is employed for the subsequent de-noising *** results of the qualitative analysis show that the amplitude and the period of the bubble oscillation can be clearly observed in the time-domain diagram of the de-noised signal based on the *** the quantitative analysis,the de-noised signal based on the EEMD has better performance with higher signal-to-noise ratio(SNR),smaller root-mean-square error,and larger correlation coefficient than that based on the wavelet transform(WT)and the empirical mode decomposition(EMD).Furthermore,with the increase of the complexity of the radiation pressure signal(e.g.,the increase of the dimensionless pressure amplitude of the acoustic wave and the decrease of the SNR of the input signal),the above three evaluation indexes of the de-noised signal based on the EEMD are all better than those based on the other two *** the signal is more complex,the de-noising capabilities of the WT,the EMD are greatly reduced,but the EEMD can still maintain the good de-noising capability,which shows the superiority of the signal de-noising procedure proposed in the present paper.

关键词： Radiation pressure cavitation bubble oscillation signal de-noising ensemble empirical mode decomposition(EEMD) autocorrelation function wavelet soft-threshold de-noising

Physics of cavitation near particles

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Journal of Hydrodynamics 2024年第1期36卷 102-118页

作者： Jia-xin Yu Xiao-yu Wang Jun-wei Shen Jin-sen Hu Xiang-qing Zhang Da-qing He Yu-ning Zhang Key Laboratory of power Station energy Transfer Conversion and System(Ministry of Education) School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing102206China

The combined effect of cavitation and silt abrasion presents a great challenge and threat to secure the operation and the efficiency of hydraulic machineries working in sediment-laden *** present paper critically reviews the current research progress on the interaction mechanisms of the bubbles and the ***,the analytical models including boundary treatment methods for predicting the jet dynamics of the bubble collapse near particles are ***,the bubble collapsing dynamics,jet dynamics and shock wave characteristics near particles are revealed both experimentally and ***,the bubble-particle-wall system is investigated with a focus on microjets.

关键词： Cavitation bubble particle jet shock wave

Thermo-Flow Performances for the Main-Auxiliary Integrated Natural Draft Dry Cooling System

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Journal of Thermal Science 2024年第3期33卷 1010-1025页

作者： ZHANG Zongyang HOU Yichen ZHOU Hanyu JIA He CHEN Lei KONG Yanqiang WANG Weijia YANG Lijun DU Xiaoze Key Laboratory of power Station energy Transfer Conversion and System of Ministry of Education School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing102206China

Recently,natural draft dry cooling system with the main-auxiliary integrated air-cooled heat exchangers in the up and lower layers,has drawn attention to the electric power *** research firstly develops two physical models for the integrated cooling system,namely Case A and Case *** Case A,the main air-cooled heat exchanger is arranged in the upper layer and the auxiliary air-cooled heat exchanger arranged in the lower layer,while in Case B,the two heat exchanger systems are arranged in the opposite *** then,directing at the engineering TMCR and TRL 1 working conditions,the unit-local-overall thermo-flow characteristics of Case A and Case B are obtained and compared by numerical *** findings show that,for the auxiliary air-cooled exchanger,Case A has obviously higher cooling performances than Case B,with the difference varying from 5.46%to 7.55%.Whereas,for the main air-cooled exchanger,Case B shows the recovered cooling performances,with the difference changing from 1.15%to 2.99%.Case A is preferably recommended to the engineering application in consideration of more strict cooling demand of the auxiliary cooling ***,this research will provide some theoretical guidelines for the design and construction of the main-auxiliary integrated natural draft dry cooling system.

关键词： integrated dry cooling system main air-cooled heat exchanger auxiliary air-cooled heat exchanger upper layer and lower layer thermo-flow performances