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Numerical Investigation into the Transient Behavior of the Spike-Type Rotating Stall for a Transonic Compressor Rotor

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Fluid Dynamics & Materials Processing 2022年第3期18卷 761-773页

作者： Pengfei Ju Fangfei Ning Zhiting Tong Jingying Wang Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical EngineeringTianjin University of TechnologyTianjin300384China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education(Tianjin University of Technology) Tianjin300384China Research Institute of Aero-Engine Beihang UniversityBeijing100191China National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics School of Energy and Power EngineeringBeihang UniversityBeijing100191China School of Energy and Power Engineering Shandong UniversityJinan250061China Shandong Engineering Laboratory for High-Efficiency Energy Conservation and Energy Storage Technology&Equipment Shandong UniversityJinan250061China

In this paper,a numerical investigation into a spike-type rotating stall process is carried out considering a transonic compressor rotor(the NASA Rotor 37).Through solution of the Unsteady Reynolds-Averaged Navier-Stokes(URANS)equations,the evolution process from an initially circumferentially-symmetric near-stall flow field to a stable stall condition is simulated without adding any artificial *** the near-stall operating point,periodic fluctuations are present in the overall flow of the ***,the blockage region in the channel periodically shifts from middle span to the *** fluctuating condition does not directly lead to stall,while the full-annulus calculation eventually evolves to ***,a kind of“early disturbance”feature appears in the dynamic signals,which propagates forward ahead of the rotor.

关键词： Transonic compressor spike stall numerical simulation early disturbance dynamic signal

Numerical Investigation on Thermal Characteristics and Energy Efficiency of Lithium-Ion Battery Under Different Charging Stresses

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SSRN 2024年

作者： Xie, Wenlong Gao, Xinlei Zhang, Zhengjie Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering Tianjin University of Technology Tianjin300384 China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education Tianjin University of Technology China Department of Mechanical Engineering Imperial College London LondonSW7 2AZ United Kingdom School of Transportation Science and engineering Beihang University Beijing100191 China

The thermal characteristics of lithium-ion batteries during the charging process significantly impact their electrochemical performance and safety, particularly under high-rate or extreme temperature conditions. In this study, an electrochemical-thermal coupling model for a 2.5 Ah LiNi0.8Co0.1Mn0.1O2 18650 lithium-ion battery is proposed and experimentally validated. The heat generation and variation patterns of the electrodes at different charging rates and temperatures are evaluated, and the influence mechanisms of various electrode design parameters on charging energy efficiency are elucidated. The results reveal that high-rate charging increases the proportion of irreversible heat in the total heat generation, primarily due to the increase in ohmic heating at the positive electrode. Ambient temperature is less sensitive to heat generation than the C-rate, but low temperatures can also increase irreversible heat and are associated with an increase in positive polarization heat. Analyzing thermal characteristics at the electrode level can contribute to the optimization of battery design and the improvement of thermal safety. Electrode architectures, including electrode thickness, active material porosity, particle radius and negative/positive electrode capacity (N/P) ratio, are determined to analyze their effects on the heat generation of various components within the battery. Thick electrodes or active materials with high porosity induce significant ohmic heating and increase irreversible heat, with a slight effect on reversible heat, which is detrimental to energy efficiency. Large particle radii primarily increase reaction heat and polarization heat, and a high N/P ratio reduces the battery heat generation and is related to the reduction of negative reaction heat. Notably, variations in both two parameters have limited impact on to energy efficiency. Therefore, implementing appropriate thermal management across various charging scenarios is crucial for achievin

关键词： Lithium-ion batteries

Understanding the Limitations of Thick Electrodes on the Rate Capability of High-Energy Density Lithium-Ion Batteries

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SSRN 2024年

作者： Xie, Wenlong Zhang, Zhengjie Gao, Xinlei Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering Tianjin University of Technology Tianjin300384 China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education Tianjin University of Technology China School of Transportation Science and engineering Beihang University Beijing100191 China Department of Mechanical Engineering Imperial College London LondonSW7 2AZ United Kingdom

As a core component of transportation electrification, lithium-ion batteries need to address two critical challenges: achieving high energy density and enabling fast charging. However, changes in electrode thickness could result in a trade-off between these two characteristics. Herein, the impact of electrode thickness on the electrochemical performance, thermal behavior, as well as energy and power density of LiNi0.8Co0.1Mn0.1O2(NCM)/graphite batteries are investigated through mathematical modeling. Underutilization of active materials of the thick electrode is identified as the primary limitation on rate capability, which can be attributed to the slow solid-state diffusion and poor electrolyte transport within the electrode, especially the enlarged concentration gradients in the solid phase and the lithium depletion in the electrolyte phase during high-rate charging. Evolutions of local current density and heat generation rate along the electrode thickness are compared, identifying the underlying mechanism of inducing uneven reaction kinetics inside the battery. The trade-off between the energy and power density as a function of electrode thickness is investigated based on the limitations of charge transfer and mass transport. Furthermore, the rate-limiting factors under various application requirements are elucidated. This study will provide guidance for the electrode design of high-energy-density batteries with fast-charging capabilities. © 2024, The Authors. All rights reserved.

关键词： Lithium-ion batteries

Reform and Practice in Experimental Teaching from the View of "emerging Engineering": Case Study on the Field of Energy and Power Engineering 2

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Reform and Practice in Experimental Teaching from the View o...

2nd Information Communication Technologies Conference, ICTC 2021

作者： Tian, He Liu, Lijian Tian, Miao Zhou, Shimin Tianjin University of Technology Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control National Demonstration Center for Experimental Mechanical and Electrical Engineering Education Tianjin University of Technology School of Mechanical Engineering Tianjin China Tianjin Academy of Educational Science Tianjin China Tianjin Newborn New Energy Technology Co. Ltd Tianjin China

ISBN: (纸本)9780738142876

According to the idea of "Emerging Engineering Education"talent training model of Ministry of Education, students should be trained to have "metaphysical"concept, connection, imagination, macro thinking. Project-driven experiment teaching focuses on a project, and the goal is the completion of the project;the student is the center of teaching activities, which is supported by the inquiry process. This study analyzes the significance of the project-driven method in experimental teaching. This paper describes the implementation process of experimental teaching in the field of energy and power engineering in terms of project design, teaching system construction and so on under the project-driven method. By analyzing the results of a questionnaire survey distributed to students of energy and power in the College of Mechanical Engineering at the Tianjin University of Technology, it is found that the students are satisfied with the effects of project-driven experimental teaching, and the use of experimental teaching has greatly aroused the students' enthusiasm for learning. The ability of the students to engage in autonomous learning, engineering practice and innovation has been greatly improved, and a good teaching effect has been achieved. © 2021 IEEE.

关键词： Students

Mechanochromic Properties of Acridine Heterocyclic Derivatives with a Donor-Acceptor Configuration

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SSRN 2023年

作者： Shi, Wei Rong, Bin Li, Shuzhe Lin, Yang Liao, Yingjie Cao, Chenhui Pan, Saihu Wei, Bin Key Laboratory of Advanced Display and System Applications Ministry of Education Shanghai University Shanghai200072 China School of Mechatronic Engineering and Automation Shanghai University Shanghai200444 China School of Microelectronics and Control Engineering Changzhou University Changzhou213164 China Anhui Sholon New Material Technology Co. Ltd. Anhui Chuzhou239500 China Shanxi Datong University China

The mechanochromic properties of two acridine heterocyclic derivatives with a donor-acceptor configuration, 10-phenyl-10-(4-(7,7,13,13-tetramethyl-7,13-dihydro-5H-indeno[1,2-b]acridin-5-yl)phenyl)anthracene-9(10H)-one (DpAn-InAc) and 10-(4-(5,5-dimethylbenzofuro[3,2-c]acridin-13(5H)-yl)phenyl)-10-phenylanthracen-9(10H)-one (DpAn-BzAc), were investigated. The average red shift of the emission peak was 18 nm for DpAn-InAc, with the long grinding time bringing the greatest shift, while both the highest and the lowest pretreat temperature brought a greater impact on the luminescent peak. The grinded DpAn-BzAc preheated at 100 °C showed the maximum wavelength shift, which was ascribed to the lower glass transition temperature of DpAn-BzAc. Meanwhile, the discolored sample could be recovered by ethanol fumigation, proving that the discoloration was reversible. XRD analyses revealed that under the anisotropic force, the microcrystalline structure of DpAn-InAc and DpAn-BzAc were destroyed, resulting in the shift of the fluorescence peak. The fluorescence shift of DpAn-BzAc was more obvious than that of DpAn-InAc, while its recovery was inferior compared to DpAn-InAc, which was due to its looser molecular structure. Finally, DpAn-InAc and DpAn-BzAc were applied in delivering rewritable encrypted information and both of the two molecules have shown capabilities in transmitting coded information. This work sheds light on using the molecule with donor-acceptor molecular structure in the stimuli-responsive field, and shows their potential application in transmitting encrypted information. © 2023, The Authors. All rights reserved.

关键词： Fluorescence

A Novel Microwave Humidity Sensor Based on a Complementary Interdigital Capacitor Resonator

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SSRN 2024年

作者： Wang, Litian Chen, Jie Li, Dan Qian, Lirong Xiong, Yang Miao, Lin Zhang, Rong Li, Cuiping Tianjin Key Laboratory of Film Electronic and Communication Devices School of Integrated Circuit Science and Engineering Tianjin University of Technology Tianjin300384 China School of Integrated Circuit Science and Engineering Tianjin University of Technology Tianjin300384 China Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering Tianjin University of Technology Tianjin300384 China National Demonstration Resonant for Experimental Mechanical and Electrical Engineering Education Tianjin University of Technology China

This study presents a novel microwave humidity sensor that utilizes a complementary interdigital capacitor resonator (CIDCR), an advanced design derived from the traditional complementary split ring resonator (CSRR) structure. The CIDCR design enhances the sensor's performance by concentrating the electric field in a more compact region, leading to improved sensitivity and miniaturization. The sensor is coated with a composite film of chitosan (CS) and polyacrylamide-glycerol (PAMG), combining the high moisture sensitivity of PAMG with the stability of CS. The CIDCR-based sensor demonstrates superior performance, including high sensitivity, a broad detection range, rapid response/recovery times, and excellent long-term stability. Density functional theory (DFT) calculations further elucidate the moisture-sensitive mechanisms at the molecular level, highlighting the role of hydrogen bonding in the composite film. Application tests confirm the sensor's potential for use in respiratory monitoring, non-contact sensing, and health monitoring, showcasing the advantages of the CIDCR structure in achieving enhanced humidity sensing capabilities. © 2024, The Authors. All rights reserved.

关键词： Humidity sensors

Step-length optimization based on genetic algorithm for a parallel mobile robot 7

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Step-length optimization based on genetic algorithm for a pa...

7th International Conference on Information Science and control Engineering, ICISCE 2020

作者： Liu, Shuang Chen, Wei Wu, Hang Zhang, Wenchang Tianjin University of Technology Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Tianjin China Institute of Medical Support Technology Academy of Military Sciences of Chinese PLA Tianjin China

ISBN: (纸本)9781728164069

With the development of technology, parallel mobile robots have been paid more attention in various industries due to the strong load capacity, high running stability and rapid response speed. However, step-length optimization is an important but challenging task for this kind of mobile robot. Step length has dramatic effect on the stability of robot and the performance of electric cylinder. Balancing the speed characteristics and stability margin, we propose a genetic algorithm to solve this problem and design a novel fitness function that can measure the motion characteristics of parallel mobile robot. Effectiveness of our method is verified by experiments. © 2020 IEEE.

关键词： Mobile robots

Non-Stoichiometric Protic Ionic Liquids for Efficient Carbon Dioxide Capture and Subsequent Conversion Under Mild Conditions

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SSRN 2024年

作者： Wang, Litian Chen, Jie Wang, Shuai Zhou, Tongyao Li, Dan Li, Cuiping Qian, Lirong Xiong, Yang Miao, Lin Xie, Zhiyong Tianjin Key Laboratory of Film Electronic and Communication Devices School of Integrated Circuit Science and Engineering Tianjin University of Technology Tianjin300384 China School of Integrated Circuit Science and Engineering Tianjin University of Technology Tianjin300384 China Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering Tianjin University of Technology Tianjin300384 China China Tianjin Bohua Yongli Chemical Industry CO. Ltd Tianjin30045 China

Protic ionic liquids (PILs) have emerged as innovative solvents with significant potential for CO2 capture and transformation, presenting a sustainable alternative to conventional methods which often involve energy-intensive processes or environmentally detrimental chemicals. Herein, a novel strategy for CO2 capture and conversion at mild conditions using non-stoichiometric protic ionic liquids (NPILs) was demonstrated for the first time. These NPILs, employed as sorbents, solvents, and catalysts, were composed of imidazole (Im) and 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) in various ratios. Correlations between the mole ratio of DBU/Im and physicochemical properties such as viscosity, conductivity, thermal stability, and the distribution of neutral and ionic species were systematically investigated. Effects of the absorption temperature and CO2 partial pressure on the absorption capacity were also studied. Different absorption mechanisms, including carbonate and carbamate pathways, were analyzed using FT-IR and NMR spectroscopy. Moreover, the fixed CO2 could be catalytically converted to quinazoline-2,4(1H,3H)-diones under exceptionally mild reaction conditions (1atm, 50 °C, metal-free process). A plausible reaction mechanism involving simultaneous CO2 activation and substrate activation for the transformation of CO2 into quinazoline-2,4(1H,3H)-diones was verified through NMR spectra. It is believed that the new insights into the CO2 mechanism will facilitate the rationaldesign of functional ionic liquids for CO2 capture, utilization, and storage in the future. © 2024, The Authors. All rights reserved.

关键词： Carbon dioxide

Effects of Wall Emissivity on Aerodynamic Heating in Scramjets

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Fluid Dynamics & Materials Processing 2020年第6期16卷 206-216页

作者： Yue Zhou Pengfei Ju School of Aeronautical Science and Technology Beihang UniversityBeijing100191China Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical EngineeringTianjin University of TechnologyTianjin300384China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education(Tianjin University of Technology) Tianjin300384China

The effects of the wall emissivity on aerodynamic heating in a scramjet are *** supersonic turbulent combustion flow including radiation is solved in the framework of a decoupled strategy where the flow field is determined first and the radiation field *** particular,a finite difference method is used for solving the flow while a DOM(iscrete ordinates method)approach combined with a WSGGM(weighted sum of gray gases)model is implemented for radiative *** nonreactive turbulent channel flows are examined for a DLR hydrogen fueled scramjet changing parametrically the wall *** results indicate that the wall radiative heating rises greatly with increasing the wall *** the wall emissivity rises,the radiative source and total absorption increase,while the incident radiation decreases ***,although the radiative heating can reach a significant level,its contribution to the total aerodynamic heating is relatively limited.

关键词： Scramjet aerodynamic heating wall emissivity radiation