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Study on basic coal consumption characteristics in dynamic process of 660MW ultra-supercritical coal-fired unit

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Study on basic coal consumption characteristics in dynamic p...

2019 Canadian Society for Civil Engineering Annual Conference, CSCE 2019

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

ISBN: (纸本)9780791883747

With the spreading of intermittent renewable power, coalfired power units should cycle frequently to balance the load between power supply side and demand side. Coal consumption of coal-fired units operating in dynamic processes is influenced by many factors, including thermal system, control system, heat storage variation, etc. Therefore, it is very difficult to evaluate the energy efficiency of coal-fired units operating in dynamic processes. It is important to ascertain the basic coal consumption rate in dynamic processes, which is the basis to evaluate the operation performance of coal-fired units. In this study, an off-design calculation model of 660MW ultra-supercritical coal-fired unit is developed and validated with design parameters. The developed model can be used to predict the coal consumption rates under steady-state off-design conditions. The basic coal consumption means the coal consumption of coal-fired units with operating parameters the same as target values. To calculate the basic coal consumption rate, a load cycling process is differentiated into lots of short time periods and every period is regarded as a steady-state condition with constant load, therefore the coal consumption rates in every period are equal to that of the corresponding steady-state condition. The calculation formula of basic coal consumption rates in is derived for load cycling processes. On the basis of the off-design calculation model and assumption of idealized condition, average coal consumption rates during different processes with constant load cycling rates can be calculated and analyzed. Results show that if the initial and final loads are both settled, the basic coal consumption rate remains unchanged and is independent of load cycling rate. If the load cycling amplitude remains unchanged, the basic coal consumption rate increases as the initial load decrease. The study aims to provide benchmark values for the energy consumption analysis in actual dynamic processes,

关键词： Energy efficiency

Experimental Investigation on flow and Heat Transfer Characteristics of Helium in Rectangular Narrow Slit Channel

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SSRN 2024年

作者： Li, Changzhong Wang, Chenglong Sun, Yanyu Chen, Ronghua Tian, Wenxi Su, Guanghui Qiu, Suizheng State Key Laboratory of Multiphase Flow in Power Engineering China Department of Nuclear Science and Technology Shaanxi Key Lab. of Advanced Nuclear Energy and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China China Nuclear Power Engineering Co. Ltd. Beijing100840 China

Helium is utilized as coolant in high temperature gas cooled reactors. Rectangular narrow slit channels are commonly present in the core. The flow and heat transfer properties of helium significantly affect the core temperature and flow distribution. This paper experimentally investigates the flow and heat transfer properties of high temperature helium in rectangular narrow slit channel. The Reynolds numbers ranged from 468 to 5327, the temperature ratio of wall to bulk from 0.91 to 1.22, the helium outlet temperature up to 944 K, and the maximum heat flux density up to 0.101 MW/m². In the experiment, the total and local convective heat transfer coefficients, along with the friction factors, are measured. Correlation equations for the Nusselt number and friction factor with respect to Reynolds number are derived. The primary findings are as below: the friction factors of helium in rectangular narrow slit channels are significantly larger than those calculated by current empirical correlations. In the turbulent zone, the measured local Nusselt numbers are in excellent accordance with the Gnielinski correlation;however, a significant discrepancy exists in the laminar zone. New flow heat transfer correlation equations are proposed on the bases of experimental data. Upon comparison, the total Nusselt numbers fall in the error of 10%, and almost all local Nusselt numbers and the friction factors fall in the error of 20%. © 2024, The Authors. All rights reserved.

关键词： Helium

Rotor Dynamic Analysis of Supercritical Carbon Dioxide Bryton Cycle Coaxial Integrated Unit

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Rotor Dynamic Analysis of Supercritical Carbon Dioxide Bryto...

Prognostics and System Health Management Conference (PHM-Qingdao)

作者： Xiaokang Xu Yi Yang Jiangfeng Wang Juwei Lou Liangqi Chen State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an China Laboratory of Science and Technology on Integrated Logistics Support College of Intelligence Science and Technology National University of Defense Technology Changsha China

The rotor system plays a very important role in supercritical carbon dioxide Brayton cycle system, and its dynamic problem will directly affect the motion stability and safety of the whole unit. In this paper, the rotor dynamic model of supercritical CO 2 coaxial unit is established by finite element method, and the critical speed, modal shape and unbalance response of the rotor are studied. The first seven critical speed of the rotor and the first seven natural frequency of the rotor at the working speed are calculated. The bending modal of the rotor and the position where the rotor amplitude is the largest are analyzed, which can provide reference for the optimization design of the rotor stability. The influences of mass unbalances at the operational speed of rotor are analyzed. The research can provide some suggestions for the optimal design and actual operation of the supercritical CO 2 coaxial integrated unit.

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Mild Combustion of a Premixed Nh3/Air Jet Flame in Hot Coflow Versus its Ch4/Air Counterpart

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SSRN 2023年

作者： Li, Pengfei Wang, Guochang Liu, Xiangtao Shi, Guodong Cai, Xiao Liu, Zhaohui Mi, Jianchun State Key Laboratory of Coal Combustion School of Energy and Power Engineering Huazhong University of Science and Technology Wuhan430074 China College of Engineering Peking University Beijing100871 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Dalian Maritime University China

MILD combustion is very suitable for solving the problems of unstable flame and high NOx emission (ENOx ) for ammonia fuel, but the related studies are rare. This work numerically investigates the MILD combustion characteristics of a premixed NH3/air jet flame in hot coflow (JHC) under different jet equivalence ratio (ΦJ), coflow temperature (TC) and oxygen level (XO2,C). For comparison, the similar CH4/air MILD-JHC flames are also calculated. Results show that the NH3 flame generally has lower temperature rise and heat release as well as larger reaction zone than CH4. This may suggest that the former flame can develop to the MILD regime more easily. ENOx is two orders higher from the NH3 than CH4 flame at all TC and XO2,C for ΦJ 1, ENOx of the NH3 flame quickly drops to near zero, but ENH3 and EH2 are very high (~1000 ppm) and the combustion efficiency is low. Moreover, ENOx increases quickly (slowly) with XO2,C (TC) while ENH3 and EH2 are quite low at TC ≥ 1300 K and XO2,C ≥ 1% for the NH3 flame. ENOx mainly comes from NO but N2O is also important at low ΦJ and TC. Therefore, considering all ENOx , ENH3, EH2 and the burning efficiency, the optimal conditions for NH3 MILD combustion are ΦJ =1, TC ≥ 1500 K and XO2,C =1%-3%. In addition, compared to the conventional flame, the NH3 MILD combustion can reduce ENOx by 1-2 orders. © 2023, The Authors. All rights reserved.

关键词： Ammonia

Novel Fast Predesign Methodology of Centrifugal Compressor Used for Pemfcs Based on 1d Loss Mechanism and Interpretable Machine Learning Models

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SSRN 2024年

作者： Chen, Zhikai Sun, Jieshuai Chen, Ziying Spence, Stephen Peng, Xueyuan Feng, Jianmei School of Energy and Power Engineering Xi'an Jiaotong University Xi'An710049 China School of Mechanical Manufacturing and Biomedical Engineering Trinity College Dublin Dublin 2 Ireland State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'An710049 China

The significant challenge of balancing accuracy, time, and cost has consistently compelled designers to develop more efficient and economical predesign methods. To tackle this issue, a novel predesign method amalgamating one-dimensional (1D) loss model with gradient boosting decision tree (GBDT) model has been proposed. A high-precision 1D loss model was developed and experimentally tested for rapid performance assessment. Furthermore, two machine learning models, named Extreme Gradient Boosting (XGBoost) and Light Gradient Boosting Machine (LightGBM), were trained, and compared to construct surrogate models. Hyperparameter optimization was executed utilizing a Bayesian algorithm to identify the optimal hyperparameter set. Additionally, the Sobol sensitivity analysis and Shapley Additive Explanations (SHAP) based interpretability were used to explore the paramount factors affecting the model's outputs and the interactions among the sensitive parameters. The findings underscore that the blade outlet angle, impeller outlet diameter, impeller outlet width, inlet shroud diameter, and blade inlet angle(shroud) are the most five important parameters influencing the model's indexes. Some beneficial design guidelines are distilled from their feature importance and interactions. and The implement of new design yields powerful evidence for the developed prior knowledge with an increase of 2.5830% in isentropic efficiency and a reduction of 1.5202% in power consumption. © 2024, The Authors. All rights reserved.

关键词： Sensitivity analysis

Laser-Synthesized Ligand-Free Cu Nanocatalysts in Electrochemical CO2 Reduction to Methane

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arXiv

arXiv 2025年

作者： Ye, Taiping Lactionov, Artyom Sozaev, Islam Popov, Anton Klimentov, Sergei Kabashin, Andrei V. Liu, Ya International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi 710049 China National Research Nuclear University MEPhI Moscow115409 Russia CNRS LP3 Aix-Marseille Université Marseille13288 France

Electrochemical CO2 reduction (eCO2R) represents a pivotal strategy for mitigating global carbon emissions while simultaneously converting renewable energy into storable chemical fuels. Copper-based catalysts have been extensively explored in this field due to their unique capability to catalyze multi-carbon products. However, the intrinsic complexity of eCO2R pathways on Cu surfaces often leads to mixed product distributions, posing a significant challenge for achieving high selectivity toward a single desired hydrocarbon. Herein, we report a breakthrough in methane selectivity using laser-synthesized, ligand-free Cu nanomaterials. Unlike conventional Cu catalysts that produce diverse products, these ligand-free nanoparticles exhibit unprecedented selectivity for methane (CH4) with a Faradaic efficiency (FE) exceeding 70% at superior overpotentials. The absence of surface ligands, a direct consequence of the ultrafast laser ablation synthesis, ensures abundant exposed active sites with tailored electronic and geometric configurations. We attribute the exceptional methane selectivity to the synergistic effects of active sites-rich surfaces and optimized *CO intermediate binding energetics, which favor the protonation pathway toward CH4 rather than C–C coupling. This work not only resolves the longstanding selectivity dilemma in Cu-catalyzed eCO2R but also establishes laser-synthesized ligand-free nanomaterials as a versatile platform for designing high-performance electrocatalysts. Copyright © 2025, The Authors. All rights reserved.

关键词： Nanoparticles

The Thermal Effect of Flame-Wall Interaction on the Nox Emission Characteristics of Ammonia Swirling Flames in a Model Combustor

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SSRN 2022年

作者： Zhang, Meng Xu, Wanying Wang, Ruixiang Wei, Xutao Wang, Jinhua Huang, Zuohua Tan, Houzhang State Key Laboratory of Multiphase Flow in Power Engineering Xian Jiaotong University Xian710049 China MOE Key Laboratory of Thermo-Fluid Science and Engineering Xian Jiaotong University Xian710049 China

Ammonia (NH 3 ) combustion is regarded as one of the most promising solutions to realize zero CO 2 emission. However, the low reactivity, low heat release result in a strong flame-wall interaction (FWI) which significantly affects the flame stabilization and the NOx emission characteristics. In this study, an air film cooling on the swirling combustion chamber was designed to investigate the thermal effect of the FWI on NOx emission. The flame structure and NO production are measured with the OH-/NO-PLIF techniques. The NOx emission is analyzed by the Gasmet DX4000 Fourier Transform Infrared (FTIR) gas analyzer. Large eddy simulation is also conducted to extend the understandings of experimental findings. For the current combustion chamber, the temperature difference is increasing as downstream location, resulting a larger convection heat loss. The heat loss shows no apparent effect on the flame structure and NO production at the symmetrical plane. The flame tends to be more fragmentized and the NO production is largely decreased at near wall region and the outer recirculation zone with increasing heat loss. This can be understood that NO production rate from the oxidation of NH i by O, H and OH radicals through HNO is largely decreasing in these regions. Therefore, a decreasing NO trend is found at the chamber outlet. NO emission shows a decreasing trend with heat loss at lean condition, which is mainly caused by the decreased NO production at near wall region resulting from the lower combustion efficiency. However, N 2 O, a more serious greenhouse gas, significantly increases as the heat loss increases. This is mainly because that the production of N 2 O from NO is promoted and N 2 O decomposition is suppressed within the thermal boundary. Thus, N 2 O might become a more serious emission component in NH 3 fuelled gas turbines. Moreover, a tradeoff behaviour between NO and N 2 O is observed as increasing heat loss. This study suggests the thermal effect of FWI on t

关键词： Heat losses

Steam Entrainment and Heat Transfer Characteristic of Steam Submerged Jet Condensation within Steam-Water Mixture Layer

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SSRN 2022年

作者： Zhao, Quanbin Fu, Pengfei Chong, Daotong Chen, Weixiong Liu, Jiping Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China MOE Key Laboratory of Thermal Fluid Science and Engineering Xi'an Jiaotong University Xi'An710049 China

Steam-water interface and mixture layer are the key window for understanding the heat and mass transfer mechanism of steam submerged jet condensation. In this paper, the steam-water two-phase mixture layer is captured and the interfacial vortex is observed with a quasi-two-dimensional submerged steam jet visualization experimental platform. Then, the volume heat transfer capacity of steam-water mixture layer and heat transfer coefficient with steam-water inner interface are obtained. Furthermore, a new turbulent eddy entrainment model is developed to calculate the local entrainment mass rate and local condensation heat transfer coefficient. Both the local entrainment mass rate and local condensation heat transfer coefficient increases along steam jet direction, and reaches the maximum value at the tail of the mixture layer. The calculated condensation heat transfer coefficient ranges from 0.88 to 2.94 MW·m -2 ·K -1 , which is about the half of the value of hypothetical heat transfer coefficient with inner interfacial area. © 2022, The Authors. All rights reserved.

关键词： Condensation

Corrosion Behavior of Low Carbon 9cr-Ods Steel in High Temperature Oxygen-Saturated Lead-Bismuth Eutectic

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SSRN 2024年

作者： Yang, Chongdou Xu, Yuwen Yun, Di Zhao, Bingyao Liu, Wenguan Gao, Rui Xie, Shijing Qiu, Jie School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China State Key Laboratory of Multiphase Flow Xi’an Jiaotong University Xi’an710049 China Sino-French Institute of Nuclear Engineering and Technology Sun Yat-Sen University Zhuhai519082 China

The corrosion behavior of low-carbon 9Cr-ODS steel were carried out in oxygen saturated LBE. It was found that the thickness of the oxide film increased with increasing corrosion time, but the growth rate gradually slows down with increasing time. TEM and XRD results show that the main structure of the oxide layer formed on 9Cr-ODS steel is multilayered structure, consist of an (Fe,Cr)3O4 spinel inner layer, mixed with some nano precipites FeCr2O4, Cr3O4, Mn3O4 and morphous at the grain boundaries, nanocrystal transition layer and a Fe3O4 outer layer. The corrosion mechanism of 9Cr-ODS steel in liquid LBE is discussed. © 2024, The Authors. All rights reserved.

关键词： Manganese oxide