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Investigation on turbulent characterization of arrayed micro-tube premixed hydrogen flames using an enhanced flamelet library

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Applied Thermal engineering 2025年 275卷

作者： Han, Xiao Yin, Yanxu Wang, Bosen Chang, Yunxin Cai, Xiao Research Institute of Aero-Engine Beihang University Beijing100191 China National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics Beihang University Beijing100191 China Collaborative Innovation Center for Advanced Aero-Engine Beihang University Beijing100191 China Xi'an Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xi'an710049 China

Lean turbulent premixed hydrogen/air flames exhibit increased flame wrinkling and significantly enhanced flame speeds, posing challenges for stable combustion. In the novel arrayed multi-flame burner, flame instabilities are intensified by flame-flame interactions. This study develops a distributed and efficient numerical framework for the Large Eddy Simulation-Flamelet Generated Manifold (LES-FGM) method, incorporating an improved 1D flamelet library. The framework is applied to investigate flame dynamics in both bluff-body and conical flame systems under varying equivalence ratios (= 0.4–0.7) and Karlovitz numbers (Ka = 1–100). By accounting for preferential diffusion, thermal-diffusive instability, and heat loss in stretched flames, the framework improves the accuracy of the flamelet library and captures key physical effects. 1D simulations are performed to validate and analyze the influence of differential diffusion on flame characteristics. The impact of transient flame stretching is analyzed in detail, revealing its critical role in stability transitions across varying turbulence intensities. Additionally, this study examines turbulence effects and micromix multi-flame interactions. The flame stretch factor varies from 1.1 to 2.4 in these three cases. At lower equivalence ratios, higher Ka suppresses tip-opening but intensifies small-scale flame wrinkling. Flame pocket detachment becomes more frequent. Vortex interactions play a key role in flame instability. The strain rate of conical flames is 40 % lower than that of bluff-body flames. These findings provide novel insights into flame dynamics in multi-flame burner arrays, which are critical for optimizing combustion performance in gas turbine combustors. © 2025 Elsevier Ltd

关键词： Large eddy simulation

Curvature Adaptive Voxel-Based Monte Carlo Method with Application for Customized Retinal Laser Surgery

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SSRN 2024年

作者： Zhang, Hao Li, Dong Chen, Bin Zhang, Hanfeng Liang, Yao Zheng, Yuping Wang, Guoxiang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Department of Ophthalmology 2nd affiliated hospital Medical School Xi’an Jiaotong University Xi’an710049 China Department of Mechanical Engineering The University of Akron AkronOH44325 United States

Accurate prediction of light propagation and energy deposition in biological tissues is crucial for the success of laser-based medical treatments. We propose a novel Curvature Adaptive Voxel-based Monte Carlo method (CAVMC) to correct for light reflection and refraction at curved interfaces by introducing coordinate transformation with an artificial surface parallel to the curved interface. This approach achieves an optimal balance between simulation accuracy and efficiency. Our study demonstrates that for small optical mismatches, the relative error can be reduced significantly, with the energy deposition error dropping from 34.7% to 6.6%. For large optical mismatches, CAVMC substantially improves accuracy, reducing computational errors by more than 50%. We validated CAVMC in a customized retinal laser therapy scenario for diabetic retinopathy, demonstrating its ability to accurately predict laser energy deposition and thermal effects, which is crucial for avoiding tissue damage during treatments. The efficiency and accuracy of the CAVMC method make it valuable for personalized retinal laser surgery and potentially other medical applications. Overall, CAVMC offers a robust tool for simulating light propagation in heterogeneous biological tissues, enhancing the precision and safety of medical treatments. © 2024, The Authors. All rights reserved.

关键词： Laser surgery

Multi-Objective Optimization Design of a Solar-powered Integrated Multi-Generation System Based On Combined Sco 2 Brayton Cycle and Orc Using Machine Learning Approach

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SSRN 2024年

作者： Zhang, Junyi Wang, Jiangfeng Liu, Wenxing Hu, Bin Lou, Juwei Zhao, Pan Institute of Turbomachinery State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China Nuclear Power Institute of China No. 328 Section 1 Changshun Avenue Sichuan Chengdu610213 China DongFang Electric Engineering& Consulting Co. Ltd 18 Xixin Avenue High-tech West Zone Sichuan Chengdu611731 China

With the rapid development of technology and the accelerated degradation of the global environment, there is an urgent need to find a clean and efficient energy solution to replace traditional fossil fuels for energy production. Additionally, this solution should also meet the growing demand for various energy products for energy user. In particular for remote areas such as islands, coastal regions and deserts which are far from the power grid, regular resources such as power, freshwater, and cooling are all scarce. Therefore, integrating freshwater and cooling subsystems into the power generation system to create a multi-generation system can facilitate achieving energy self-sufficiency in remote regions. This paper proposes an integrated multi-generation system powered by a solar power tower (SPT) according to the principle of cascading energy utilization, which includes a supercritical CO2 (SCO2) Brayton cycle, an Organic Rankine cycle (ORC), an ejector refrigeration cycle (ERC), and a reverse osmosis (RO) unit. A mathematical model is established to analyze the system performance from the perspectives of energy, exergy and economics. Different machine learning algorithms including back propagation neural network (BPNN), support vector regression (SVR), random forest (RF) are used to develop prediction models of the system performance. By comparing and analyzing the predictive performance of different machine learning models, the optimal machine learning model is obtained as a surrogate model for the thermodynamic model of the proposed system to accelerate the optimization process. The results show that the BPNN model demonstrates the highest predictive accuracy and the lowest relative error fluctuation, maintaining a relative error of less than 1% for over 97.5% of the data in the testing set. When comparing the multi-objective optimization results of the BPNN model with those of the thermodynamic model from multiple perspectives, it can be observed that the res

关键词： Neural network models

Recent advances in all-in-one flexible supercapacitors

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Science China Materials 2021年第1期64卷 27-45页

作者： Tiezhu Guo Di Zhou Wenfeng Liu Jinzhan Su Electronic Materials Research Laboratory Key Laboratory of the Ministry of Education&International Center for Dielectric ResearchSchool of Electronic Science and EngineeringXi’an Jiaotong UniversityXi’an710049China State Key Laboratory of Electrical Insulation and Power Equipment Xi’an Jiaotong UniversityXi’an710049China International Research Centre for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an710049China

The rise of personalized flexible electronics has promoted the rapid development of flexible supercapacitors due to their long service life,fast charging-discharging rates and safe *** from the traditional flexible supercapacitors,the all-in-one integrated flexible supercapacitors are more resistant to deformation and lower interface resistance,which have a broader application prospect in the field of flexible *** review briefly summarizes the preparation methods and electrochemical properties of some typical all-in-one supercapacitors,represented by planar and fibrous structures in recent ***,the basic understanding of traditional flexible supercapacitors and all-in-one integrated flexible supercapacitors,and the key parameters of the performance of flexible supercapacitors are ***,the hydrogel matrix all-in-one supercapacitors with different functional characteristics(stretchable,self-healing and compressible)and the nonhydrogel matrix(separator,flexible membrane)all-in-one supercapacitors are ***,the challenges and future development of flexible supercapacitors are considered.

关键词： flexible supercapacitors all-in-one hydrogel

High-Entropy (Cocrfemnni)3o4 Catalysts for Propane Catalytic Destruction: Effect of the Precipitation Agent

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SSRN 2023年

作者： Ma, Yue Zhang, Yun Jian, Yanfei Jiang, Zeyu Chai, Shouning Li, Lu Xia, Lianghui He, Chi State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China Department of Physics and Information Technology Baoji University of Arts and Sciences Shaanxi Baoji721016 China National Engineering Laboratory for VOCs Pollution Control Material & Technology University of Chinese Academy of Sciences Beijing101408 China

Efficient catalytic destruction of light alkane with ultra-stable and highly symmetric structure is still an intractable issue. High entropy oxides (HEOs) with high chemical disorder and lattice distortion and superior stability have shown great potential in heterogeneous thermocatalysis. Herein, spinel-type HEOs are synthesized via a scalable co-precipitation method with different precipitants (NaOH, Na2CO3, and NaHCO3) and firstly adopted in catalytic destruction of propane. Results demonstrate that the HEO-NaOH possesses the best activity, achieving 90% of propane conversion at 325 °C with an apparent activation energy of 56 kJ·mol-1. Compared with other two HEOs, HEO-NaOH system has larger quantities of surface oxygen vacancies and easily forming several reactive oxygen species (OOH-, O2-, and OH-, etc.), which significantly contribute to the catalytic performance. Moreover, the excellent water resistance of HEOs is verified due to their high conformational entropy and structural stability. Reaction mechanism reveals that OOH- and O2- are the key species in the oxidation of C3H8, which break C-H and C-C bonds in sequence, and are then converted to oxygenated compounds via oxygen oxidation before the final mineralization. The present work provides new insights into the fabrication of efficient catalysts for light alkane destruction as well as other thermocatalytic applications. © 2023, The Authors. All rights reserved.

关键词： Sodium hydroxide

Parametric Investigation of Multi-Pulsed Cryogen Spray Cooling for Skin Protection During Hyperthermal Laser Lipolysis Through in Vitro Experiment and Numerical Simulation

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SSRN 2022年

作者： Xin, Hui Yu, Fangbo Deng, Chenggang Chen, Ming Li, Dong Chen, Bin State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi'An710049 China School of Mechanical Engineering Ningxia University Ningxia Yinchuan750021 China

Laser lipolysis is now a commonly accepted modality to remove fat. Transcutaneous hyperthermal laser lipolysis has attracted researchers’ interest because of its advantages of non-invasive nature and high efficiency. Owing to the competitional absorption of laser energy between skin and adipose tissue, it is necessary to develop efficient skin cooling technology to protect epidermis and dermis from thermal damage. In vitro laser experiment was carried out using streaky pork which has similar optical and thermal properties with human adipose tissue. Temperature changes of pigskin epidermis under 1210nm laser irradiation with different power (6W~12W) and irradiation duration (3s~13s) were obtained by infrared thermal imager. The experimental results showed that the epidermis temperature will exceed the safety threshold of 47°C when laser power is equal to 6W and irradiation duration longer than 5s, or laser power is equal or larger than 9W and irradiation duration equal or longer than 3s. To protect skin from thermal injury, multi-pulsed cryogen spraying cooling (MP-CSC) by using R134a was introduced. Numerical simulation was conducted to match cooling and laser parameters by simplifying skin tissue to a multi-layered model. It is suggested that hyperthermal laser lipolysis with power of 6W/9W and irradiation duration of 7s can be realized, accompanied by MP-CSC with pulse duration of 10ms, pulse delay of 2000ms and pulse number of 5. © 2022, The Authors. All rights reserved.

关键词： Cooling

Adaptive Growing Randomized Neural Networks for Solving Partial Differential Equations

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arXiv

arXiv 2024年

作者： Dang, Haoning Wang, Fei Jiang, Song School of Mathematics and Statistics Xi’an Jiaotong University Shaanxi Xi’an710049 China School of Mathematics and Statistics State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China Institute of Applied Physics and Computational Mathematics Beijing100088 China

Randomized neural network (RNN) methods have been proposed for solving various partial differential equations (PDEs), demonstrating high accuracy and efficiency. However, initializing the fixed parameters remains a challenging issue. Additionally, RNNs often struggle to solve PDEs with sharp or discontinuous solutions. In this paper, we propose a novel approach called Adaptive Growing Randomized Neural Network (AG-RNN) to address these challenges. First, we establish a parameter initialization strategy based on frequency information to construct the initial RNN. After obtaining a numerical solution from this initial network, we use the residual as an error indicator. Based on the error indicator, we introduce growth strategies that expand the neural network, making it wider and deeper to improve the accuracy of the numerical solution. A key feature of AG-RNN is its adaptive strategy for determining the weights and biases of newly added neurons, enabling the network to expand in both width and depth without requiring additional training. Instead, all weights and biases are generated constructively, significantly enhancing the network’s approximation capabilities compared to conventional randomized neural network methods. In addition, a domain splitting strategy is introduced to handle the case of discontinuous solutions. Extensive numerical experiments are conducted to demonstrate the efficiency and accuracy of this innovative approach. Copyright © 2024, The Authors. All rights reserved.

关键词： Partial differential equations

Effect of 2,5-dimethylfuran addition on ignition delay times of n-heptane at high temperatures

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Frontiers in Energy 2019年第3期13卷 464-473页

作者： Zhenhua GAO Erjiang HU Zhaohua XU Geyuan YIN Zuohua HUANG State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

The shock tube autoignition of 2,5-dimethylfuran (DMF)/n-heptane blends (DMF)/n-100%, by mole fraction) with equivalence ratios of 0.5, 1.0, and 2.0 over the temperature range of 1200-1800 K and pressures of 2.0 atm and 10.0 atm were investigated. A detailed blend chemical kinetic model resulting from the merging of validated kinetic models for the components of the fuel blends was developed. The experimental observations indicate that the ignition delay times nonlinearly increase with an increase in the DMF addition level. Chemical kinetic analysis including radical pool analysis and flux analysis were conducted to explain the DMF addition effects. The kinetic analysis shows that at lower DMF blending levels, the two fuels have negligible impacts on the consumption pathways of each *** the DMF addition increases to relatively higher levels, the consumption path of n-heptane is significantly changed due to the competition of small radicals, which primarily leads to the nonlinear increase in the ignition delay times of DMF/n-heptane blends.

关键词： ignition delay time shock tube kinetic model 2,5-dimethylfuran (DMF) n-heptane

Experimental study on potassium catalyzed gasification of large particle size biomass with CO2

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Journal of the Energy Institute 2023年 111卷

作者： Huang, Xiaole Li, Yuhang Ren, Jiyun Yang, KaiXuan Li, Ruiyu Bai, Yang Deng, Lei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an710049 China Xi'an Thermal Power Research Institue Co. Ltd. Xi'an710032 China Shanghai Power Equipment Research Institute Co. Ltd. Shanghai 200240 China Shunde Institue of Inspection Guangdong Institue of Special Equipment Inspection and Research Foshan528300 China

Candlenut wood with large particle size is selected to investigate the biomass gasification catalyzed by potassium. The sample pore structure, the spatial distribution of potassium, and the effects of potassium salt species on the biomass gasification with CO2 are examined. The results show that the large particle candlenut wood exhibits obvious spatial anisotropy and that the pore structure is mainly distributed along the axial direction. Large particle candlenut wood has a more uniform distribution of potassium salts along the axial direction. Part of the potassium salt releases outward during the gasification, which reduces the potassium salt content in the sample center. The average potassium contents of sample loaded with KCl and biochar of sample loaded with KCl are 9.273% and 7.745%, respectively. The synthesis of polycyclic aromatic hydrocarbons in tar could be inhibited by potassium, which could also catalyze the gasification and methane removal reactions of biochar and facilitate the formation of CO and H2. Compared to raw sample (28.99%), the syngas yields from the gasification of sample loaded with KCl, sample loaded with K2CO3, and sample loaded with K2SO4 are 40.22%, 52.16%, and 41.72%, separately. The catalysis of potassium is closely related to its occupation of the active sites on biochar. The chemical bonds formed by potassium and biochar are repeatedly broken and formed during the gasification, which promotes the decomposition of organic matter. Compared with KCl and K2SO4, K2CO3 has a better catalytic effect. © 2023 Energy Institute

关键词： Biomass