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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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SSRN 2024年

作者： Qian, Yiran Liu, Tao Zhang, Yan Leng, Yuyang Shi, Tianrun Song, Meihui Chen, Weixiong State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 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 analysed, 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°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°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°C and stabilizes at the design value of 699.4°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 reductions from 100% FP to 80%, 60%,

关键词： Brayton cycle

Experimental Investigation of Pressure Pulsation and Noise Due to Thermodynamic Effects on Cavitation in High-Temperature Water

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SSRN 2024年

作者： Xu, Bo Hu, Hongfei Yang, Kuang Wang, Haijun State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

In power systems or equipment, water is often in a state of high temperature and high pressure. The thermodynamic effects are non-negligible during cavitation. The orifice plate, as one of the most fundamental structures in cavitation flow, is used as a research object in cavitation experiment to analyze the thermodynamic effects of high-temperature water. In this study, the variational mode decomposition is improved by using the center frequency and correlation coefficient of the intrinsic mode functions, thus developing an adaptive variational mode decomposition method (AVMD). This method effectively decomposes the pressure pulsations and radiated noise during cavitation and can reasonably classify different cavitation stages. The results indicate that periodic turbulence pulsation frequencies of 5-15 Hz are observed in non-cavitating regions. With the onset of cavitation, the flow field exhibits high-frequency pseudo-periodic frequencies, and the turbulence pulsation frequency gradually decreases, with Strouhal number (St) reducing from 0.2 to 0.1. In regions of severe cavitation, the St of turbulence pulsation frequency exceeds 0.4. Under the same cavitation number, during the development stage of cavitation, as the degree of subcooling decreases, the temperature drop in the cavitation region gradually increases, and the maximum is 2.5 K. The amplitude of pressure pulsations also declines, with the maximum reduction reaching 49.7%. In the severe cavitation stage, the temperature drop in the cavitation region reaches a maximum of 2.87K and is no longer affected by the degree of subcooling. The radiated noise sound pressure level exhibited similar trends as the pressure pulsations inside the pipe when the cavitation number changed. The noise was dominated by low frequencies, with a sound pressure level around 82dBA. The mid-frequency component had a sound pressure level around 79dBA, while the high-frequency component corresponded to a level around 77dBA. At the s

关键词： Variational mode decomposition

Calcium Looping Sorption-Enhanced Electrified Steam Methane Reforming for Efficient Hydrogen Production with Short- and Long-Duration Cooperative Energy Storage

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SSRN 2024年

作者： Song, Huchao Zhang, Xinyue Lin, Xiaolong Bian, Hao Liu, Yinhe State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Currently, the dominant hydrogen production technology is steam methane reforming, but both the reforming reaction and the combustion for driving the reaction produce significant CO2 emissions. Sorption-enhanced methane reforming enables the in-situ removal of CO2 produced by the reforming reaction and promotes higher hydrogen yields, however, CO2 emissions from combustion cannot be avoided. Renewable electricity instead of combustion for reaction heating can eliminate combustion carbon emissions and flue gas heat loss, but its dependence on renewable electricity supply prevents continuous and stable operation. This study proposes a sorption-enhanced electrified steam methane reforming technology based on short- and long-duration cooperative energy storage and calcium looping carbon capture. This technology utilizes the CO2 adsorption and energy storage property of the absorbent to absorb CO2 in situ in the reformer and transform renewable electricity to chemical and thermal energy in the regenerator as short- duration energy storage. The energy stored in the absorbent can be used to drive the methane reforming reaction and transformed into chemical energy in hydrogen continuously as long- duration energy storage. Through First law and Second law analysis, this study has found that the novel process improves thermal efficiency by 8.5 percentage points and reduces the exergy loss of the overall process by 53.2% compared with the sorption-enhanced steam methane reforming process. Based on current fuel prices in China, the novel process is more economical than the other steam methane reforming processes simulated in this study. Sensitivity analysis has found that low electricity and high methane prices benefit the economic performance of the novel process. This study may provide a stable, efficient, and economical way of clean hydrogen energy production. © 2024, The Authors. All rights reserved.

关键词： Hydrogen production

Research on Full-Day Operation Strategies of Virtual power Plants Integrating Interruptible Loads Energy Storage to Adapt to Various Weather Changes

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SSRN 2024年

作者： Chong, Daotong Tian, Zeyu Wang, Zhu Du, Guanghan Yan, Hui State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China

Interruptible load energy storage (ILES) represents a novel energy storage technology with the dual functionality of load and storage. The storage aspect of an ILES facilitates flexible and controllable scheduling. In contrast, the load attribute offers widespread energy storage potential. ILES surpasses traditional storage methods, particularly at large scales, by efficiently utilizing existing resources, reducing investment needs, and avoiding energy decay. However, the dual nature of ILES presents challenges in its direct application to power grids, necessitating its integration into virtual power plants (VPPs) as an indirect but crucial scheduling tool. This study develops a dynamic simulation model for a large-scale VPP incorporating an industrial-scale ILES. A control strategy is proposed, focusing on the efficient and flexible use of ILES and ensuring the VPP's safe, stable operation. This strategy includes a method for determining the dispatching time and range of the ILES and introduces three schemes—power universality, power enhancement, and power attenuation—to compute the dispatching power of the ILES and develop a dispatch plan tailored to varying needs. Additionally, the strategy enhances existing control systems by generating optimized signals to increase the dispatch rate and ensure operational safety. Simulation analysis of three typical scenarios assesses the dispatching parameters of the ILES, VPP operation safety, and system capacity for grid ancillary service participation. The findings show that while maintaining safety and stability, the ILES dispatch rate improved from 10 MW/min to 40 MW/min, diminishing energy losses and enhancing efficiency. Adjustments in dispatching times increased the ILES dispatching power from 53.7 MW to 101.8 MW and the VPP output power from 16.9 "MW∙h" to 96.7 "MW∙h", significantly boosting system flexibility and ancillary service capabilities. The variability in dispatching power, under scheme modifications, ranged

关键词： Energy storage

Thermodynamic Modeling and Analysis of the Hydrogen and Combustible Gas Production in Supercritical Water Partial Oxidation System of Coal

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SSRN 2024年

作者： Li, Yifeng Xing, Guowei Liu, Shi Guo, Shenghui Ge, Zhiwei Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Supercritical water partial oxidation (SCWPO) is an eco-friendly coal treatment technology that lowers the temperature needed for complete gasification of coal, promotes hydrogen output, enables targeted regulation of gaseous product composition, and eliminates gaseous pollutants. Current researches mainly focus on experiments and numerical simulations, with limited exploration in thermodynamics. he present study establishes an auto-thermal SCWPO cogeneration system for Hongliulin coal, employs sensitivity analysis to refine system parameters, and utilizes Life Cycle Assessment to evaluate environmental impact of hydrogen production system. As the outlet temperature of the reactor increases and the preheating water flow and equivalence ratio (ER) increase, the fraction of hydrogen in the gas product rises;conversely, the fraction of the combustible gas (CH4+CO+H2) rises. The SCWPO system can be precisely tailored to yield high-purity hydrogen or combustible gas by modulating the amount of oxygen input. The system of combustible gas production is capable of generating 241.67 GJ·h-1 of energy and attaining a cold gas efficiency of 81.62% when the ER is 0.25. The hydrogen production system can produce 1004.38 kg·h-1 of hydrogen and 206 t·h-1 of heated water at 0.5 MPa and 150℃ for an ER of 0.6. The optimum hydrogen production system achieved an energy efficiency of 90.97%, showing an improvement of 11.12% to 46.76% compared to previous hydrogen production systems. The standard Global Warming Potential of the system through carbon capture technology is 0.0087. The system developed in this paper benefits the industrial application of SCWPO and the optimization of subsequent processes. © 2024, The Authors. All rights reserved.

关键词： Thermolysis

Thermodynamic Analysis of a Supercritical Water Partial Oxidation Autothermal Cogeneration System of Coal

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SSRN 2024年

作者： Xing, Guowei Li, Yifeng Ren, Changyifan Ge, Zhiwei Guo, Liejin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Supercritical water partial oxidation (SCWPO) is a very efficient technology for the environmentally sound treatment of resources. Currently, there are few thermodynamic studies of SCWPO cogeneration system. In this study, a new supercritical water partial oxidation autothermal cogeneration system of coal is proposed. The system was evaluated for energy and exergy under typical operating conditions. The efficiencies achieved were 86% for energy and 47.6% for exergy. Due to the mixed working fluid is a mixture of H2O and CO2, the CO2 is very easy to capture. The exergy analysis revealed that the most significant exergy loss within the system occurred in the SCWPO reactor, which accounted for 78.2%% of the total exergy loss. Further sensitivity analysis of the system indicates that optimum values identified for both back pressure and carbon capture and storage unit (CCS) first stage pressure (PV-pump1), which are 8.5 kPa and 0.03 MPa. Additionally, increasing both the flow rate and temperature of preheated water can significantly enhance system efficiency. An increase in the flow rate of preheated water can lead to a reduction of the maximum system temperature;however, an elevation in the temperature of preheated water may cause a significant rise of the maximum system temperature, which is not conducive to the stable operation of the system. Finally, this paper compares the proposed system with the systems that have been reported in the literature. The results show that the system represents an innovative cogeneration solution with considerable advantages. © 2024, The Authors. All rights reserved.

关键词： Exergy

High Concentration of CO and CO2 Inhibits Coal Gasification in Supercritical Water

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SSRN 2024年

作者： Zhang, Rui Zhao, Shuaiqi Huang, Han Zhao, Kunpeng Bai, Bofeng State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Supercritical water gasification technology achieves efficient resource utilization of lignite and produces H2, CO and CO2. In this study, we experimentally investigated the impact of gas product generated from high concentration (>30 wt%) formic acid decomposition on the gasification of Tiebei lignite in the supercritical water. H2 promotes the pyrolysis of carbon structures, the increase in CO promotes CO2 generation through the water-gas shift reactions, and the enrichment of CO2 hinders gas diffusion. We found that high concentration of formic acid(H2, CO and CO2) inhibits the gasification of Tiebei lignite in the supercritical water. Compared with coal gasification in the supercritical water without formic acid, 30wt% formic acid reduces the carbon efficiency of lignite by 7.66%, and the mass conversion of coal by 3.97%. When the concentration of formic acid is 30wt% to 70wt%, the higher concentration of formic acid(H2, CO and CO2), the worse gasification performance of Tiebei lignite. © 2024, The Authors. All rights reserved.

关键词： Water gas shift

Experimental study on combustion, ash fusibility and slagging propensity during co-combustion of organic solid waste and lignite

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Journal of the Energy Institute 2023年 106卷

作者： Liu, Hu Wang, Yancheng Xue, Jingwen Zhang, Yankang Yu, Pengfei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Rapidly growth of organic solid waste (OSW) has caused serious social and environmental problems. Incineration as one of the most good public acceptance and environmentally friendly method attains increasing attention. In this study, the co-combustion characteristics of OSW and lignite, including the ignition and burnout temperature, ash melting and slagging propensity were studied. The experimental results show that the ignition temperature almost remains stable while the burnout temperature of the blends decreases as the increase of the OSW blending ratio, since the heat release during volatile combustion is beneficial for the burnout of coal char, but the polymer may melt and block the pores of the coal char at high temperature when the OSW blending ratio is higher than 30%. Besides, the slagging propensity of blending fuel is severe when the OSW blending ratio is 30%, and special attention should be paid to avoid slagging during the combustion process. © 2022 Energy Institute

关键词： Lignite

Flocculation of suspended cohesive particles in Rayleigh-Bénard turbulence

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Physical Review Fluids 2025年第2期10卷 024305-024305页

作者： Han Huang Shuaiqi Zhao Rui Zhang Binbin Pei Kunpeng Zhao Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Key Laboratory of Mechanics on Disaster and Environment in Western China The Ministry of Education of China Lanzhou University Lanzhou 730000 China

We employ a four-way coupled numerical approach to investigate the dynamics of suspended cohesive particles in Rayleigh-Bénard turbulence. The Stokes drag, cohesive, and direct contact forces between primary particles are captured in detail, yielding the phenomena of flocs' aggregation, breakage, and deformation. The momentum and thermal exchange between primary particles and the fluid are considered based on the Source-in-Cell method. We found that the initial increase of the average floc size indicates a temporary flocculation phase, which is followed by an equilibrium phase where the average floc size becomes stable, reflecting the balance between aggregation and breakage. Different from the traditional perspective, which attributed the local accumulation of particles to their gravity, we found that the suspended particles still tend to accumulate in the bottom hot boundary layer region. This accumulation is primarily driven by the temperature-induced variation in aggregation strength and the nonuniform spatial distribution of floc inertia. Additionally, the stronger cohesion yields a reduction in momentum intensity of the thermal plumes, primarily due to the more pronounced weakening of fluid momentum by the larger flocs.

关键词： Momentum