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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

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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

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Revised Control Strategy for Coal-Fired power Plants During Transient Processes Considering Heat Transfer Deterioration of Cooling Wall: Flexibility Enhancement and Security Operation

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SSRN 2024年

作者： Wang, Dengliang Zhao, Yongliang Gao, Wei Chen, Weixiong Wang, Chaoyang Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Increasing share of power generation from intermittent renewable energy has resulted in an expanding demand for deep peaking and operational flexibility of thermal power plants. Under this circumstance, it causes an enormous threat to the safe operation of the boiler, especially cooling wall. So it is crucial to focus on the thermo-hydraulic performance of the cooling wall during transient processes. In this paper, a 1100 MW ultra-supercritical thermal power plant is used as the research object. A one-dimensional dynamic model of the cooling wall is constructed based on the conservation of mass, conservation of momentum, conservation of energy, state, metal heat storage and heat transfer equations. The temperature distributions of working fluid, inner and outer wall along the height direction of the cooling wall are obtained. Dry-out phenomenon of the cooling wall during the load cycling process is observed. It is found that heat transfer deterioration is a key reason for metal wall temperature intermittent fluctuation. When the load cycling rates are 2.5% Pe/min and 3.0% Pe/min, the maximum temperatures of metal tube wall during the loading up process reach 527.9°C and 557.3°C, respectively. Furthermore, a revised control strategy is proposed based on the heat transfer deterioration characteristics of the cooling wall. During the loading up process, the highest wall temperature is significantly reduced from 557.3°C to 502.2°C at 3.0% Pe/min. The maximum power ramp rate is increased from 2.5% Pe/min to 3.0% Pe/min when the revised control strategy is adopted. © 2024, The Authors. All rights reserved.

关键词： Fossil fuel power plants

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Data-Driven Dimensional Analysis of Critical Heat Flux in Subcooled Vertical flow: A Two-Stage Machine Learning Approach

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SSRN 2024年

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

This study pioneers a machine learning-based method designed for automating dimensional analysis to refine critical heat flux (CHF) prediction. Addressing the limitations of traditional dimensional analysis, this approach not only enhances the precision in identifying and quantifying dimensionless numbers but also provides valuable insights for CHF modeling. By integrating the Buckingham Pi theorem with modern computational methods, including the active subspace method and automatic differentiation (AD), the research represents a hopeful methodological advancement in thermal hydraulics. Application of this algorithm to a dataset from subcooled departure from nucleate boiling (DNB) conditions in vertical tube experiments has led to the identification of the most significant dimensionless number, showing a strong negative correlation with the boiling number Bochf. This key discovery underpins the development of a simplified dimensionless correlation, exhibiting improved predictive accuracy over existing models. The contribution of this research lies in its potential to deepen the understanding of physical phenomena, such as CHF, and to mitigate the reliance on empiricism in complex physical modeling. The methodological innovation introduced in this study provides a more systematic and insightful approach to thermal phenomena analysis, potentially enhancing the precision and applicability of predictive models in a wide range of thermal management and design optimization applications. While the initial results are promising, the full impact and breadth of this methodology necessitate further exploration through extensive application and rigorous validation in various CHF scenarios. © 2024, The Authors. All rights reserved.

关键词： Heat flux

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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

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Experimental and Numerical Study on Co-combustion Behaviors and NO_(x) Emission Characteristics of Semi-coke and Coal in a Tangentially Fired Utility Boiler

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Journal of Thermal Science 2021年第4期30卷 1116-1131页

作者： WANG Chang’an FENG Qinqin JIN Liyan WANG Zhichao YAO Wei WANGPengqian DU Yongbo ZHANG Xilai YANG Zhongcan CHE Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power EngineeringXi’an Jiaotong UniversityXi’an 710049China Xi’an Thermal Power Research Institute Co. LTD.Xi’an 710054China

The utilization of powdery semi-coke as a power fuel in pulverized coal-fired power plants has become a new and potential technique to consume the excess powdery *** characteristic of low volatile results in poor combustion performance and high NO_(x) emission,and to co-fire with bituminous coal is a practical strategy to address this ***,the co-combustion characteristics and the inherent interaction between semi-coke and coal remain insufficiently *** addition,the influences of secondary air arrangement,the boiler operation load,and the fuel type on co-combustion process are still unclear,which is urgent to be further *** the present study,experiments and numerical simulations were jointly utilized to inquire into the co-combustion behaviors and NO_(x) emission features of semi-coke and *** results demonstrated that the"out-furnace method"was a suitable choice for small-capacity boiler when the proportion of semi-coke was 33%,due to the limited combinations of the semi-coke injection *** was recommended that semi-coke was preferred to be injected from the middle layers of the furnace under the"in-furnace method"to improve the overall co-combustion *** critical value of the separated over fire air ratio in this study was 27.5%,over which a slight drop of carbon content in fly ash could come ***,the elevation in the proportion of separated over fire air gave rise to the significant decline of NO_(x) *** constricted secondary air arrangement was preferred to be employed due to the high boiler *** separated over fire air and the surrounding air needed to maintain a wide-open degree to prevent the increase of NO_(x) emissions and the coking of *** the load reduction regulation method adopted in this study,the NO_(x) concentration first rose and then dropped,while the burnout ratio decreased obviously as the operation load was *** combinations of coa

关键词： semi-coke numerical simulation co-combustion NOx emission blending method

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Heat Transfer Enhancement of Air flow Through New Types of Perforated Dimple/Protrusion Fins

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SSRN 2024年

作者： Sen, Palash Chen, Mengjie Bai, Bofeng State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Heat transfer enhancement technologies of air flow are of critical to energy conservation and emission reduction in industrial applications. This paper explores the numerical simulation analysis of 18 kinds of perforated dimple/protrusion fins. The wind speed varies within the range of 2~6m/s, and the investigation delves into the impact of different structural parameters on strengthening factor Nu/Nu0, resistance factor f/f0 and other comprehensive evaluation factor performance evaluation criteria (PEC) of perforated dimple/protrusion fins. The study specifically explores the influence of structural parameters, including intercepting perforated dimple/protrusion height (S0), aperture (D), hole structure offset (a), and the arrangement of perforated dimple/protrusion structure, on heat transfer performance. The overall heat transfer performance of the perforated dimple/protrusion fins rises with height under the same operating conditions. It first increases and then declines with the increasing aperture, and first drops and then increases with the increasing offset. The hole structure offset is better on the inflowing leeward side than on the inflowing side. The fins with both perforated dimple and perforated protrusion structures have advantages over the one with either of two structures, and the alignment arrangements are identified as the optimal configuration. © 2024, The Authors. All rights reserved.

关键词： Air

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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

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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

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DYNAMIC CHARACTERISTICS AND CONTROL STRATEGY OPTIMIZATION OF A 1000 MW LIGNITE-FIRED power UNIT INTEGRATED WITH PRIMARY AIR HEATER

DYNAMIC CHARACTERISTICS AND CONTROL STRATEGY OPTIMIZATION OF...

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ASME 2024 power Conference, power 2024

作者： Li, Mengjie Li, Maoliang Yin, Chaoqiang Liu, Ming Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China Clean Combustion and Flue Gas Purification Key Laboratory of Sichuan Chengdu China Dongfang Electric group Dongfang Boiler Co. LTD Sichuan Zigong China

ISBN: (纸本)9780791888186

Lignite is a kind of low rank coals with abundant reserves, and it is cost-effective for power plants. However, the moisture content is about 30% to 60% for the lignite, and the water carried by the raw lignite is dried in the pulverization system, which will consume much energy. Therefore, high temperature should be maintained for the primary air of the lignite-fired power plants, especially when the power plant operates under low power ratio or with low temperature feed air. In this study, a 1000 MW lignite-fired power system integrated with a primary air heater is proposed and analyzed. In the primary air heater, the low temperature reheated steam is extracted from the boiler to heat the primary air after the air preheater. The integration of primary air heater makes the lignite-fired power system be more complex, which will influence the operational flexibility of the power plant. Therefore, dynamic models of steam turbines and the boiler with waste heat recovery system were developed in this study. The transient characteristics of the unit under load cycling conditions and primary frequency modulation processes were analyzed. Then, control strategy of the primary air heater of turbine and boiler were enhanced based on the simulation results. The results show that the temperature of primary air can be increased by 51-69 °C by the additional air preheater, and the primary frequency modulation capacity can be improved by 8 MW at 50% power load ratio during primary frequency modulation process. Copyright © 2024 by ASME.

关键词： Steam turbines

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