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Dynamic modelling and thermo-mechanical performance evaluation of thermal power plants during the background of enhanced operational flexibility

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ENERGY 2025年 318卷

作者： Fan, Mengyang Zhao, Yongliang Liu, Zefeng Wang, Zhu Liu, Ming Yan, Junjie Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

To integrate the high penetration of renewable energy into the power grid, thermal power plants must expand their load variation range and rate. However, increased these operational flexibility leads to rapid fluctuations in thermal parameters, which induces stress variations that affect the safety of critical components within power plants, particularly steam turbine rotors. Consequently, monitoring rotor stress during dynamic processes is essential for the safe and reliable operation of power plants, which has been underemphasized in previous studies. In this study, a dynamic model of the power plant and an online stress calculation model were developed to assess the thermo-mechanical performance of the steam turbine rotor. The governing stage has been identified as the most critical area during peak shaving processes. The study reveals that as the load variation rate increases from 1.0 % to 4.0 % Pe min- 1 during peak shaving processes from 50 % to 75 % THA, the stress amplitude at the governing stage escalates from 1.8 to 22.8 MPa. Furthermore, at a load variation rate of 2.0 % Pe min- 1, increasing the peak shaving depth results in a rise in stress amplitude and fatigue damage from 3.7 MPa and 6.6 x 10- 11 to 7.8 MPa and 3.0 x 10-9.

关键词： Operational flexibility Dynamic modelling Thermal power plant Finite element analysis Steam turbine rotor

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Experimental and theoretical studies on the mixing pressure and prediction model of the steam-water two-phase injector

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2025年 239卷

作者： Wang, Zichen Zhao, Quanbin Liu, Wenbing Chong, Daotong Yan, Junjie Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The steam-water two-phase injector is widely used in various industrial applications. However, the use of improper local parameters frequently results in inaccurate predictions of the injector performance. Among them, the mixing pressure plays a crucial role in predicting the injector performance. In this paper, experimental and theoretical studies were carried out on the mixing process and overall performance of the steam-water two-phase injector. The mixing pressure is found to locate at the end of mixing chamber, where the pressure difference between wall and center is equal to 0. The experimental results indicate that the mixing pressure increases with the steam outlet pressure (related to the steam inlet pressure) and the temperature difference between inlet steam and inlet water, but changes very slightly with the inlet water pressure. Then a semi-theoretical model for calculating the mixing pressure was obtained, and the predict accuracy of mixing pressure was within +25%. A one-dimensional injector model was developed based on newly developed mixing pressure model, which could predict the axis pressure distribution and the pressure-raising performance, with prediction accuracy better than +15%.

关键词： Injector Mixing pressure One-dimensional model Pressure-raising performance

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Effect of the shear flow field on the bubble behaviors during photoelectrochemical water splitting

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ELECTROCHIMICA ACTA 2025年 512卷

作者： Liu, Miaomiao Wang, Yechun Zhen, Canghao Zhang, Bo Feng, Yuyang Du, Ruiwen Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The regulation of bubble dynamics on the photoelectrode surface through the application of external physical fields significantly influences the efficiency of photoelectrocatalytic reactions. This study investigates the evolution and detachment characteristics of bubbles on the photoelectrode surface under varying flow velocities and laser powers, focusing on the impact of shear flow on mass transfer and gas evolution efficiency. The results indicate that increasing flow velocities effectively enhance the reaction current within the system. Notably, for single bubbles, the effect of flow velocity on the reaction current is significantly more pronounced at high laser power than at low laser power. Shear flow promotes the detachment of bubbles from the photoelectrode surface, with the detachment diameter decreasing as the flow velocity increases. Additionally, applying a shear flow field enhances convective flow on the photoelectrode surface. Consequently, the combined mass transfer coefficient on the surface of the photoelectrode increases with increasing flow velocity, wherein the forced convection mass transfer plays a predominant role. However, higher mass transfer rates correspond to a decline in gas evolution efficiency for single-bubble electrodes. In addition to single bubbles, the results for multiple bubbles reveal that the number of bubbles on the photoelectrode surface initially increases and then decreases with increasing flow velocity. This study provides valuable guidance for the rational utilization of shear flow fields and the regulation of the bubble evolution process, thereby contributing to the enhancement of the photoelectrocatalytic system reaction efficiency.

关键词： Photoelectrochemical water splitting Bubble evolution Shear flow field Mass transfer

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Effect of interface control on pressurization deterioration and gas-phase distribution characteristics of a multistage mixed flow nuclear main pump

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PROGRESS IN NUCLEAR ENERGY 2025年 185卷

作者： Dai, Xiaoyu Xu, Qiang Yang, Chenyu Su, Xiaobin Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

In case of emergencies such as loss-of-coolant accident (LOCA), high gas volume fractions (GVF) leads to severe pressurization deterioration and failure in mixed flow nuclear main pump (MFNMP), threatening nuclear engineering stability and safety. Two test methods and numerical simulation based on PBM model are used to study the effects of parameters including the interface condition, inlet GVF, rotational speed, and inlet pressure on the overall and inter-stage performance of the multistage MFNMP. The results show that the critical GVF of the pump at its rated rotational speed increases by 74.3 % compared to when pumping tap water by reducing the surface tension at the flow rate of 1.0 QBEP. With the increase of booster stage, the gas-phase distribution along the axis presents the characteristics of 'single peak' and 'double peak', indicating the great difference in the gas accumulation position inside different impellers. When the mass flow rate of the gas phase is small, although the pressurization of the MFNMP decreases with the increase of the liquid flow rate due to the intensification of flow separation, the amplitude of the decrease is smaller than the increase in pressurization amplitude resulting from the elimination of gas accumulation within the impeller. Therefore, the trend of distinct sudden rise in the pressurization curve is observed in the mapping test. Reducing surface tension significantly broadens the range of liquid flows that enable the pump to operate effectively at high pressures. A correlation equation considering fluid physical properties for predicting critical GVF for MFNMP pump is presented.

关键词： Mixed flow nuclear main pump Interface control Gas-liquid two-phase flow Severe pressurization deterioration Gas-phase distribution

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Evaluation of load following control strategy for heat pipe-cooled microreactor coupled with closed Brayton cycle system

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PROGRESS IN NUCLEAR ENERGY 2025年 185卷

作者： Qian, Yiran Liu, Tao Zhang, Yan Leng, Yuyang Shi, Tianrun Song, Meihui Chen, Weixiong Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Heat pipe-cooled reactors (HPCRs), with their straightforward and compact design and inherent safety features, are considered a promising option for mobile nuclear power sources. However, the coupling between the HPCR and the energy conversion system complicates load tracking control. In this study, a comprehensive dynamic model of an HPCR coupled with a closed-air Brayton cycle (CABC) is developed. This model integrates a neutron kinetics point reactor model, a thermal resistance network model for the heat pipe, and a CABC model representing the power conversion system. To achieve effective load tracking, a control scheme for the Brayton cycle power is proposed, combining turbine bypass control with inventory control. The system's response to load variations, from 100 % full power (FP) to 50 % FP at a rate of 5 % FP/min, is analyzed, considering reactor power self-regulation. The results indicate that the reactor power exhibits an overshoot of -4.36 % and stabilizes after 2100s, while the fuel average temperature fluctuates within +4.6 degrees C and stabilizes at 2240s. Building on the dynamic performance of the HPCR-CABC system, a reactor power control scheme is developed by adjusting control drums to introduce external reactivity. This scheme successfully controls reactor power at a steady state within 720s, without fluctuation. However, the fuel average temperature fluctuates by more than 10 degrees C, stabilizing after 9450s. To improve control effectiveness, a temperature correction channel is incorporated into the reactor power control system. As a result, the fuel average temperature fluctuates within +0.3 degrees C and stabilizes at the design value of 699.4 degrees C within 860s. Compared to previous control schemes, the improved cascade reactor power control scheme results in a shorter stabilization time for the fuel average temperature. To assess the adaptability of the proposed HPCR-CABC coordination control strategy, simulations are conducted for load

关键词： Heat pipe-cooled reactor Brayton cycle Load following Control strategy

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Validation and improvement of dimethyl ether kinetic models: Insights from O^•H laser-absorption measurements across a wide pressure range

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COMBUSTION AND FLAME 2025年 275卷

作者： Zhang, Xin Feng, Zilong Hong, Congjie Zhang, Yuyang Huang, Zuohua Zhang, Yingjia Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Aiming to provide stronger constraints on the detailed kinetic models of dimethyl ether (DME) over a wide range of temperatures, pressures, and equivalence ratios, reflected shock waves combined with UV laser absorption were used to quantitatively measure microsecond-resolved (OH)-H-center dot time-histories in the oxidation of highly Ardiluted DME mixtures with varying equivalence ratios of 0.5, 1.0, and 2.0 over the temperature range of 1188-1823 K. Diagnostic wavelengths near 306.687 nm (1.5 atm) and 306.689 nm (15.5 atm) were selected at the peak of the R1(5) transition of the (OH)-H-center dot A-X (0,0) rovibronic band. Details on the temperature- and pressure- dependence of the (OH)-H-center dot profiles were revealed by a series of meticulously designed measurements. The first (OH)-H-center dot time-history measurements under high pressures and more fuel-lean conditions provided additional validation targets for the modern reaction models. Comparative evaluation of five recent reaction kinetic models of DME against the new data revealed that none of them perfectly align with all the (OH)-H-center dot time-histories measured in this study. Nevertheless, NUIG Mech1.1 and the Hashemi model demonstrated superior overall predictive performance. Taking into account the predictive performance on the global parameter of ignition delays, NUIG Mech1.1 was chosen to identify key reactions governing the (OH)-H-center dot evolution behavior. A modified NUIG Mech1.1 was proposed by incorporating the recent experimental and literature theoretical work. These new quantitative measurements of (OH)-H-center dot time-histories of DME particularly at 15.5 atm provide a critical contribution to the database needed for further model development at micro-level and combustion organization.

关键词： DME Shock tube Absorption spectroscopy OH time-histories Reaction models

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Cyclic flow cut-off characteristics of gas-liquid two-phase flow in pipeline-riser system and prediction of its occurring condition

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INTERNATIONAL JOURNAL OF multiphase flow 2025年 182卷

作者： Liu, Tianyu Zou, Suifeng Wang, Hanxuan Xu, Luhan Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

In offshore oil and gas fields, the prediction of gas-liquid two-phase flow pattern is of great importance for the design and operation of pipeline-riser systems. However, no special attention was put on the mechanism of periodic flow cut-off at the riser outlet, which is an inherent characteristic of certain flow patterns directly related to operation safety, in the study of flow pattern transition. In this study, differential pressure signals are used to explore the internal correlation between the flow cut-off of gas and/or liquid phase at the riser bottom and the riser outlet. The flow patterns are classified based on continuous flow or flow cut-off at the riser outlet. Then, the flow pattern transition mechanisms are studied from the view of the condition under which flow cut-off will appear. At high gas and low liquid velocities, the mechanism can be explained by a conventional theory;while at high gas and high liquid velocities, dissipation of hydrodynamic slugs becomes the major reason for flow pattern transition;and a unified model is introduced to predict the dissipation. At low gas and high liquid velocities, the condition for gas-liquid eruption can still describe the flow pattern transition, but it is modified by the slug dissipation model. At higher pressure, the lasting time of gas cut-off at the riser elbow becomes shorter, and a threshold can be set to decide whether it can be ignored. The predicted results are in good agreement with the flow pattern maps under different pipeline structures and fluid properties, and the reason why flow cut-off disappears in the experimental loop at high pressure of 10 MPa is successfully explained.

关键词： Pipeline-riser Two-phase flow flow cut-off flow pattern transition Slug dissipation Liquid blockage

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Effect of rolling motion and hole structure on flow and heat transfer characteristics of steam jet condensation through numerical simulation

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INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER 2025年 164卷

作者： Luo, Zhenghang Ma, Yunfei Yuan, Zhiwen Wei, Pengbo Chen, Weixiong Zhao, Quanbin Chong, Daotong Yan, Junjie Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

In the pressure relief system of nuclear power plants, through multi-hole spargers, steam is blown off into subcooled water in the form of multi-hole steam jets. The flow pattern and heat transfer (HT) characteristics of multi-hole steam jets might differ greatly from single-hole steam jets, significantly affecting the system's performance. Thus, the transient flow pattern and HT characteristics of multi-hole steam jets were investigated, and how rolling motion affects the heat transfer characteristics was also investigated. Besides, forces acting on the steam volume were investigated for steam jets under different conditions, and the HT characteristics were explored from the perspective of force analysis. Compared with single-hole steam jets, the heat transfer coefficient (HTC) of multi-hole steam jets was significantly lowered, and the steam plume penetration length and phase interface area were much larger. Besides, the increase in hole number might advance the transition of the flow regime. Under rolling conditions, the HTC was larger but did not vary much with the rolling parameters. The dominant forces were different for different situations, and the weaker effect of rolling motion on steam jets in the condensation oscillation regime may result from smaller inertial force compared with steam jets in the chugging regime.

关键词： Direct contact condensation Multi-hole steam jet Numerical simulation Rolling condition Mutual shielding effect

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Experimental study on boiling heat transfer and pressure drop characteristics of hybrid jet microchannel heat sink

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APPLIED THERMAL engineering 2025年 261卷

作者： Tang, Xiaoyu Xu, Qiang Yu, Haoyuan Pei, Chenyu Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Hybrid jet microchannel cooling can improve the non-uniform temperature distribution, significant pressure drop in microchannel, and the uneven heat transfer coefficient in jet impact. The heat transfer and pressure drop characteristics of a hybrid jet microchannel heat sink were investigated experimentally using deionized water as the working fluid. The experiments were carried out under the operating conditions of mass fluxes from 200 600 kg/m2s, subcooling degrees from 20 40 K, jet-to-target spacings from 1 2.5 mm, and outlet pressure of 1 atm. The results show that increasing jet-to-target spacing and mass flux and decreasing subcooling can improve the heat transfer coefficient, and the maximum heat transfer coefficients increase by 58 %, 73 %, and 50 %, respectively. A heat transfer correlation for the hybrid jet microchannel is proposed with a mean absolute error of 6.5% based on the experimental data. Since large jet-to-target spacing has more expansion space and is closer to the length of the potential core, increasing jet-to-target spacing results in higher critical heat flux at low mass flux. Compared to the heat sink with higher jet-to-target spacing, the pressure drop of the heat sink with the lower one is significantly affected by the mass flux due to the superposition of size effect of the channel and gas-liquid friction. In addition, the slope that pressure drop curves increase with the decrease of jet-to-target spacing rises with the mass flux, while it is not apparent with the subcooling. As the subcooling and jet-totarget spacing rise and the mass flux decreases, the coefficient of performance will increase.

关键词： Hybrid jet microchannel Jet-to-target spacing Pressure drop Heat transfer Coefficient of performance

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Experimental research on the dynamic characteristics of a vertical upward tube for supercritical CFB boilers

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INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER 2025年 164卷

作者： Du, Xiaocheng Han, Lei Wei, Ziyu An, Ning Yang, Dong Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The dynamic characteristics of water wall have great impacts on the safe operation of thermal power plants. This paper investigates the dynamic characteristics through experiments. The dynamic characteristics of the test tube in the transcritical pressure process (23 MPa -> 21.3 MPa) are studied, and the influences of various operating parameters on the response processes are explored. The response laws of some experimental parameters have been obtained. The results show that the closer the local enthalpy is to the saturated water enthalpy, the higher the heat flux, and the lower the mass flux, the easier it is for the wall temperature to soar during the transcritical process, and the longer the duration of the heat transfer deterioration. The dynamic heat transfer coefficient correlations and the judgment formula of the heat transfer deterioration boundary were fitted for the transcritical process. In addition, the response processes of inlet enthalpy, heat flux and pressure variation under supercritical pressure are studied. The response laws of experimental parameters under supercritical pressure were obtained. During the response processes under supercritical pressure, there is no heat transfer deterioration phenomenon, but the dynamic characteristics are influenced by the heat transfer characteristics.

关键词： Experiment Transcritical pressure Dynamic process Heat transfer characteristics Rapid load change Supercritical CFB boiler

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