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Low-temperature chemistry in plasma-driven ammonia oxidative pyrolysis

Green Energy & Environment 2024年第9期9卷 1477-1488页

作者： Mingming Zhang Qi Chen Guangzhao Zhou Jintao Sun He Lin school of mechanical Electronic and Control Engineering Beijing Jiaotong University school of mechanical Engineering Shanghai Jiao Tong University

Ammonia is gaining increasing attention as a green alternative fuel for achieving large-scale carbon emission reduction. Despite its potential technical prospects, the harsh ignition conditions and slow flame propagation speed of ammonia pose significant challenges to its application in engines. Non-equilibrium plasma has been identified as a promising method, but current research on plasma-enhanced ammonia combustion is limited and primarily focuses on ignition characteristics revealed by kinetic models. In this study, low-temperature and low-pressure chemistry in plasma-assisted ammonia oxidative pyrolysis is investigated by integrated studies of steady-state GC measurements and mathematical simulation. The detailed kinetic mechanism of NH3decomposition in plasma-driven Ar/NH3and Ar/NH3/O2mixtures has been developed. The numerical model has good agreements with the experimental measurements in NH3/O2consumption and N2/H2generation, which demonstrates the rationality of modelling. Based on the modelling results, species density profiles, path flux and sensitivity analysis for the key plasmaproduced species such as NH2, NH, H2, OH, H, O, O（1D）, O2（a1△g）, O2（b1∑g+）, Ar*, H-, Ar+, NH3+, O2-in the discharge and afterglow are analyzed in detail to illustrate the effectiveness of the active species on NH3excitation and decomposition at low temperature and relatively higher E/N values. The results revealed that NH2, NH, H as well as H2are primarily generated through the electron collision reactions e + NH3→ e + NH2+ H, e + NH3→ e + NH + H2and the excited-argon collision reaction Ar*+ NH3+ H → Ar + NH2+ 2H, which will then react with highly reactive oxidative species such as O2*, O*, O, OH, and O2to produce stable products of NOx and H2O. NH3→ NH is found a specific pathway for NH3consumption with plasma assistance, which further highlights the enhanced kinetic effects.

关键词： Non-equilibrium plasma Ammonia fuel Oxidative pyrolysis Pathway flux analysis Sensitivity analysis

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Automatic Miscalibration Detection and Correction of LiDAR and Camera Using Motion Cues

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Chinese Journal of mechanical Engineering 2024年第2期37卷 318-329页

作者： Pai Peng Dawei Pi Guodong Yin Yan Wang Liwei Xu Jiwei Feng school of mechanical Engineering Southeast UniversityNanjing 211102China school of mechanical Engineering Nanjing University of Science and TechnologyNanjing 210014China school of mechanical and Aerospace Engineering Nanyang Technological UniversitySingaporeSingapore

This paper aims to develop an automatic miscalibration detection and correction framework to maintain accurate calibration of LiDAR and camera for autonomous vehicle after the sensor ***,a monitoring algorithm that can continuously detect the miscalibration in each frame is designed,leveraging the rotational motion each individual sensor ***,as sensor drift occurs,the projection constraints between visual feature points and LiDAR 3-D points are used to compute the scaled camera motion,which is further utilized to align the drifted LiDAR scan with the camera ***,the proposed method is sufficiently compared with two representative approaches in the online experiments with varying levels of random drift,then the method is further extended to the offline calibration experiment and is demonstrated by a comparison with two existing benchmark methods.

关键词： Autonomous vehicle LiDAR and camera Miscalibration detection and correction Sensor drift

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Examination of two-phase behaviors in porous media during pool boiling

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Science China(Technological Sciences) 2024年第6期67卷 1695-1713页

作者： ZHANG ZhiHao GUAN ShuYa WU Rui ZHAO ChangYing school of mechanical Engineering Shanghai Jiao Tong University

The enhancement of pool boiling heat transfer using porous media has been extensively *** the two-phase distribution and evolution in porous media are crucial to the heat transfer performance,including the critical heat flux(CHF)and heat transfer coefficient(HTC),direct observation of the two-phase flow inside the media is limited owing to the blockage of the direct view from the porous *** this study,pool boiling visualization experiments were conducted on porous samples with different throat widths in deionized *** results showed that the HTC increased with the throat ***,the growth-contraction cycle of the vapor region and the formation and drying of the wall liquid film inside the porous media were *** vapor region,including the maximum and minimum areas in the boiling cycle,was quantitatively ***,the relationship between the minimum gas-phase area and HTC peak was identified.A one-dimensional transient model was developed considering solid skeleton heat conduction,liquid film evaporation,and vapor region growth to quantitatively study the influence of heat flux on the internal two-phase *** model successfully captured the maximum gas-phase area,duration of boiling cycles,and HTC trends at specific heat *** results of this quantitative study provide insights into the internal two-phase distribution and evolution induced by pool boiling.

关键词： porous media two-phase behaviors pool boiling

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Reshaping force for deformed casing repairing with hydraulic rolling reshaper and its influencing factors

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Petroleum Science 2024年第4期21卷 2745-2757页

作者： Hong-Fei Li Min Luo Ting-Ting Xu Qiao-Zhen Li Cong-Jian Huang school of mechanical Science and Engineering Northeast Petroleum University

Hydraulic rolling reshaper is an advanced reshaping tool to solve the problem of casing deformation,which has been widely used in recent years. When it is used for well repair operation, the reshaping force provided by ground devices is generally determined by experience. However, too large reshaping force may destroy the deformed casing, and too small reshaping force may also prolong the construction period and affect the repairing effect. In this paper, based on Hertz contact theory and elastic-plastic theory, combined with the process parameters of shaping, and considering the structural characteristics of the deformed casing and reshaper, we propose a mathematical model for calculating the reshaping force required for repairing deformed casing by hydraulic rolling reshaper. Meanwhile, the finite element model and numerical method of hydraulic rolling reshaper repairing deformed casing are established by using the finite element method, and the reliability of the mathematical model is verified by several examples. On this basis, the control variable method is used to investigate the influence of each parameter on the reshaping force, and the influence degree of each parameter is explored by orthogonal simulation test and Pearson correlation analysis. The research results not only provide an important theoretical basis for the prediction of reshaping force in on-site construction, but also provide a reference for the subsequent improvement of the shaping process.

关键词： Hydraulic rolling reshaper Reshaping force Deformed casing Casing reshaping Hertz contact theory

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Operation Strategy and Matching of Supply and Demand of CCHP System with Various Building Types

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Journal of Thermal Science 2024年第6期33卷 2203-2220页

作者： LI Yaohong WANG Pengxiang PENG Bin BIAN Xiaoyang school of mechanical and Electrical Engineering Lanzhou University of Technology

The important indications for assessing CCHP(combined cooling,heating and power) systems are their supply-demand matching characteristics between the user demand side and the energy supply *** characteristics are primarily influenced by different building types and operating *** view of the energy redundancy of the following electric load(FEL) and following thermal load(FTL) operation strategies and the energy deficiency of the following hybrid electric-heating load(FHL) operation strategy,this paper proposes an improved following balanced heat-electrical load(IFBL) operation strategy based on the following balanced heat-electrical load(FBL) operation *** on the energy utilization rate as the objective function,this paper optimizes the installed capacity of CCHP systems in different buildings and proposes an energy factor for evaluating the supply-demand matching characteristics of the *** results show that the energy utilization rate and energy factor of the system under IFBL are optimal relative to the other operation ***,the hotel building has the highest energy utilization rate and the lowest energy factor;on the contrary,the office building has the lowest energy utilization rate and the highest energy ***,the analysis of supply-demand matching for different building types under multiple operating strategies shows that the hospital and hotel systems exhibit optimal supply-demand matching performance under the IFBL strategy,with values of0.945 and 0.938,respectively;on the contrary,the office system has an optimal supply-demand matching of 0.935under the FEL *** the FTL strategy,the systems of all three buildings exhibit poor matching performance.

关键词： combined cooling energy factor energy utilization rate heating and power system (CCHP) matching supply and demand operation strategy

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Theoretical Modeling and Surface Roughness Prediction of Microtextured Surfaces in Ultrasonic Vibration-Assisted Milling

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Chinese Journal of mechanical Engineering 2024年第2期37卷 163-183页

作者： Chenbing Ni Junjie Zhu Youqiang Wang Dejian Liu Xuezhao Wang Lida Zhu school of mechanical and Automotive Engineering Qingdao University of TechnologyQingdao 266525China school of mechanical Engineering and Automation Northeastern UniversityShenyang 110819China

Textured surfaces with certain micro/nano structures have been proven to possess some advanced functions,such as reducing friction,improving wear and increasing *** prediction of micro/nano surface textures is of great significance for the design,fabrication and application of functional textured *** this paper,based on the kinematic analysis of cutter teeth,the discretization of ultrasonic machining process,transformation method of coordinate systems and the cubic spline data interpolation,an integrated theoretical model was established to characterize the distribution and geometric features of micro textures on the surfaces machined by different types of ultrasonic vibration-assisted milling(UVAM).Based on the theoretical model,the effect of key process parameters(vibration directions,vibration dimensions,cutting parameters and vibration parameters)on tool trajectories and microtextured surface morphology in UVAM is ***,the effect of phase difference on the elliptical shape in 2D/3D ultrasonic elliptical vibration-assisted milling(UEVAM)was *** to conventional numerical models,the method of the cubic spline data interpolation is applied to the simulation of microtextured surface morphology in UVAM,which is more suitable for characterizing the morphological features of microtextured surfaces than traditional methods due to the presence of numerous micro *** prediction of surface roughness indicates that the magnitude of ultrasonic amplitude in z-direction should be strictly limited in 1D rotary UVAM,2D and 3D UEVAM due to the unfavorable effect of axial ultrasonic vibration on the surface *** study can provide theoretical guidance for the design and fabrication of microtextured surfaces in UVAM.

关键词： Theoretical modeling Microtextured surface Ultrasonic vibration-assisted milling Cubic spline interpolation Surface roughness

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Macro electrochemical milling and its hybrid variants

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Chinese Journal of Aeronautics 2024年第8期37卷 1-35页

作者： Ningsong QU Xiaolong FANG Junzhong ZHANG Huanghai KONG Yang LIU Minglu WANG Xiaokang YUE Yuehong MA Zhihao SHEN Jiajie CHEN College of mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China school of mechanical Engineering Jiangsu UniversityZhenjiang 212003China school of mechanical Engineering Jiangsu University of Science and TechnologyZhenjiang 212003China school of mechanical Engineering Hefei University of TechnologyHefei 230009China

Macro electromechanical milling has recently attracted increasing attention because numerous large thin-walled structures composed of difficult-to-cut materials are employed in the aerospace *** paper reviews recent developments in state-of-the-art macro electromechanical *** fundamental aspects of material removal mechanisms,such as the generation and breakdown behaviors of passive oxide films of typical difficult-to-cut materials,were *** methods for breaking down passive films are summarized,and simulation methods for the machining process coupling multiple physical fields are *** electrochemical milling methods,including fly mode electrochemical milling and sink electrochemical milling,are *** made to improve process performance,such as the material removal rate,surface quality,and machining accuracy,are *** addition,the main hybrid electrochemical milling methods,including electrochemical discharge milling,mechano-electrochemical milling,and electrochemical mill grinding,are also presented.

关键词： Electrochemical machining Electrochemical milling Material removal rate Surface quality Electrochemical discharge milling Electrochemical millgrinding

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Multimode Design and Analysis of an Integrated Leg-Arm Quadruped Robot with Deployable Characteristics

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Chinese Journal of mechanical Engineering 2024年第3期37卷 41-61页

作者： Fuqun Zhao Yifan Wu Xinhua Yang Xilun Ding Kun Xu Sheng Guo Xiaodong Jin school of mechanical Engineering and Automation Beihang UniversityBeijing 100191China school of mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China

To improve locomotion and operation integration, this paper presents an integrated leg-arm quadruped robot(ILQR) that has a reconfigurable joint. First, the reconfigurable joint is designed and assembled at the end of the legarm chain. When the robot performs a task, reconfigurable configuration and mode switching can be achieved using this joint. In contrast from traditional quadruped robots, this robot can stack in a designated area to optimize the occupied volume in a nonworking state. Kinematics modeling and dynamics modeling are established to evaluate the mechanical properties for multiple modes. All working modes of the robot are classified, which can be defined as deployable mode, locomotion mode and operation mode. Based on the stability margin and mechanical modeling, switching analysis and evaluation between each mode is carried out. Finally, the prototype experimental results verify the function realization and switching stability of multimode and provide a design method to integrate and perform multimode for quadruped robots with deployable characteristics.

关键词： Quadruped robot Multimode design Mode switching Locomotion Operation

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Morphology of impact fragmentation distribution of single spherical and ellipsoidal particles in drop weight experiments

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Particuology 2024年第3期86卷 137-148页

作者： Qiuhua Miao Peng Huang Wenchang Zhu school of mechanical Engineering Southeast UniversityNanjing211189China

Particle shape is an important factor affecting the fragmentation distribution of the ore *** investigate the influence of particle shape on the morphological fragmentation distribution characteristics,the crushable ore particles are defined as prolate,oblate ellipsoid and spherical particles,which have different aspect ratios(AR)and sphericity(S).Based on the drop weight experiment,the influence of the net drop height on the macroscopic mechanical behavior and crushing distribution characteristics of the single spherical and ellipsoidal particles is *** results show that different peak-shifting characteristics exist during particle *** fragmentation distribution peak shifts left when the increased impact energy is eventually only enough to break medium-sized ***,it shifts right when impact energy is increased enough to break largest-sized ***,regardless of whether the net drop height changes,the maximum continuous fragmentation degree presents"M"-shaped characteristic with the increased *** with the ellipsoid particles,the single spherical particle is more difficult to be broken by impact,with wider equivalent particle fragmentation *** the increase of particle sphericity,the maximum continuous fragmentation degree of a single ellipsoid particle has an overall trend of initial increase and subsequent *** when particle sphericity is 0.9

关键词： Ellipsoid particles Fragmentation distribution Drop weight experiment Numerical simulation

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A lubrication model for bubbly oil lubrication with interfacial effect and thermal effect using the theory of multiphase mixtures

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Friction 2024年第2期12卷 271-290页

作者： Shaohua LI Xiaohui LIN Shuyun JIANG school of mechanical Engineering Southeast UniversityNanjing 211189China

Bubbly oil lubrication is a type of lubrication ***,the lubrication model of the bubbly oil has not been thoroughly *** paper aims to investigate the modelling for bubbly oil lubrication considering the interfacial effect and thermal effect,and a theoretical model is established based on the theory of multiphase *** interfacial and thermal effects on the static characteristics of a thrust bearing are analyzed.A test rig for the thrust bearing is developed to measure the static characteristics of the bearing under bubbly oil *** results show that the bearing static characteristics,*** temperature rise,film thickness,friction torque,and volume flow,increase with consideration of three interfacial effects;the bearing temperature rise increases but the film thickness,friction torque,and volume flow rate decrease with consideration of the three thermal effects;the thermal effect on the bearing static characteristics is greater than the interfacial effect.

关键词： bubbly oil lubrication theory of multiphase mixtures interfacial effect thermal effect fluid bearing

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