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Influence of the Acoustic Liner in Large Eddy Simulation of Longitudinal Thermoacoustic Instability in a Model Annular Combustor

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Journal of Thermal Science 2024年第2期33卷 710-724页

作者： MENG sheng ZHANG Man gao Yi AECC Commercial Aircraft Engine Co. Ltd.Shanghai200241China School of Aeronautics and Astronautics Shanghai Jiao Tong UniversityShanghai200240China

Although extensive efforts have been made to dampen the thermoacoustic instability,successfully controlling the pressure oscillations in modern gas turbines or aeroengines remains *** influence of the acoustic liner on the longitudinal thermoacoustic mode in a model annular combustor is investigated by Large Eddy Simulation(LES) in this *** result of the self-excited longitudinal thermoacoustic instability without the liner agrees well with the frequency and acoustic analysis of the pressure mode based on experimental *** different bias flow velocities of the liner located downstream of the combustor are then *** results reveal that the existence of the liner influences not only the acoustic field but also the flow *** the bias velocity is large,it leads to intense turbulence-induced fluctuations,and the pressure oscillation is modulated *** shows that the weak coupling between flow and pressure oscillations plays a significant role in the onset of the intermittency of a thermoacoustic *** on the dynamic analysis of the thermoacoustic system with the acoustic liner,this intermittency is caused by the influence of the flow field on the flame-acoustic ***,a low-order modeling method based on Van der Pol(VdP) oscillator with additive stochastic forcing is conducted to reproduce the evolving dynamics of the thermoacoustic *** the numerical cases demonstrated in this work are relatively simpler than those in a practical combustion system,the results are helpful for us to understand the effect of the acoustic liner and show the attractive potential to apply this device to suppress thermoacoustic instability.

关键词： thermoacoustic instability acoustic liner Large Eddy Simulation low-order modeling

On the Number of Irreducible Characters in a 3-block with a Minimal Nonabelian Defect Group

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Acta Mathematica Sinica,English Series 2017年第9期33卷 1267-1274页

作者： sheng YANG sheng gao Chong Bin XU Department of Mathematics Wenzhou University Department of Mathematics Hefei University of Technology

Let B be a 3-block of a finite group G with a defect group D. In this paper, we are mainly concerned with the number of characters in a particular block, so we shall use Isaacs＇ approach to block structure. We consider the block B of a group G as a union of two sets, namely a set of irreducible ordinary characters of G having cardinality k（B） and a set of irreducible Brauer characters of G having cardinality l（B）. We calculate k（B） and l（B） provided that D is normal in G and D = （x, y, z｜x3n=y3m = z3 = [x, z] = [y, z] = 1, [x, y] = z）（n 〉 m 〉 2）.

关键词： Characters blocks defect groups inertial groups

Microstructure of ferrospheres in fly ashes: SEM, EDX and ESEM analysis

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第11期9卷 1595-1600页

作者： Qing-feng XUE sheng-gao LU Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition College of Environmental and Resource Sciences Zhejiang University Hangzhou 310027 China

Ferrospheres in fly ashes from a coal-fired power plant were extracted by a magnetic separation technique and their microstructure was studied by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and environmental scanning electron microscopy (ESEM). Ferrospheres in fly ashes show significant iron enrichment compared to their respective fly ashes. Iron oxides in ferrospheres mainly occur as minerals magnetite (Fe3O4) and hematite (α-Fe2O3), which are derived mainly from the decomposition and oxidation of iron-bearing minerals in coal during combustion. EDX data indicate that ferrospheres also contain Si, S, Al and Ca resulting from quartz, mullite, anhydrite and amorphous materials. A large percentage of ferrospheres are commonly 5～50 μm in size. The microstructure of ferrospheres includes smooth, polygonal, dendritic, granular and molten drop characteristics. SEM coupled with EDX provided fast and accurate results of the microstructure and chemical composition of ferrospheres, and helped us to assess environmental issues related to the disposal and utilization of fly ashes.

关键词： Fly ash Ferrosphere Microstructure Scanning electron microscopy (SEM)

Metal phosphides and borides as the catalytic host of sulfur cathode for lithium–sulfur batteries

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International Journal of Minerals,Metallurgy and Materials 2022年第5期29卷 990-1002页

作者： Rui gao Zhenyu Wang sheng Liu Guangjie Shao Xueping gao College of Environmental and Chemical Engineering Yanshan UniversityQinhuangdao 066004China School of Materials Science and Engineering Nankai UniversityTianjin 300350China

Lithium−sulfur batteries are one of the most competitive high-energy batteries due to their high theoretical energy density of _(2)600 W·h·kg^(−1).However,their commercialization is limited by poor cycle stability mainly due to the low intrinsic electrical conductivity of sulfur and its discharged products(Li_(2)S_(2)/Li_(2)S),the sluggish reaction kinetics of sulfur cathode,and the“shuttle effect”of soluble intermediate lithi-um polysulfides in ether-based *** address these challenges,catalytic hosts have recently been introduced in sulfur cathodes to en-hance the conversion of soluble polysulfides to the final solid products and thus prevent the dissolution and loss of active-sulfur *** this review,we summarize the recent progress on the use of metal phosphides and borides of different dimensions as the catalytic host of sulfur cathodes and demonstrate the catalytic conversion mechanism of sulfur cathodes with the help of metal phosphides and borides for high-en-ergy and long-life lithium-sulfur ***,future outlooks are proposed on developing advanced catalytic host materials to improve battery performance.

关键词： lithium–sulfur batteries sulfur cathode catalytic host metal phosphides metal borides

Liutex based new fluid kinematics

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Journal of Hydrodynamics 2022年第3期34卷 355-371页

作者： Chaoqun Liu Yifei Yu Yi-sheng gao Department of Mathematics University of Texas at ArlingtonArlingtonTexas76019USA College of Aerospace Engineering Nanjing University of Aeronautics and AstronauticsNanjing210016China

The traditional Cauchy-Stokes(C-S)decomposition states that the velocity gradient tensor can be decomposed into a symmetric tensor and an anti-symmetric tensor,namely the strain-rate tensor and the vorticity ***,there are two problems with the C-S *** is that the anti-symmetric(vorticity)tensor cannot represent the fluid rotation or *** is that the symmetric(strain-rate)tensor cannot distinguish the stretching/compression and *** vorticity cannot distinguish between the non-rotational shear and the rigid rotation,vorticity has been decomposed into a rigid rotation part called“Liutex”and an anti-symmetric shear in our previous work.A Liutex-based principal coordinate system has been proposed,and the corresponding velocity gradient tensor decomposition,called the principal decomposition,is presented in this principal coordinate system,which results in:(1)a Liutex tensor that represents rigid rotation,(2)a tensor that represents pure shear and(3)a tensor that represents stretching/***,each point has its own principal coordinate system,which implies that the principal decomposition is performed in different principal coordinate systems,not the original(global)coordinate *** address this issue,the principal decomposition in the original coordinate system is derived in this paper,and,therefore,provides a new kinematic approach to study the local rigid rotation,pure shear,and stretching/*** principal decomposition is unique,Galilean invariant and has clear physical *** new velocity gradient tensor decomposition could become a foundation for new fluid kinematics.

关键词： Liutex principal coordinates principal decomposition Helmholtz Cauchy-Stokes(C-S)

Pore Size Distribution of Clayey Soils and Its Correlation with Soil Organic Matter

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Pedosphere 2015年第2期25卷 240-249页

作者： Malik ZAFFAR LU sheng-gao Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition College of Environmental and Resource SciencesZhejiang University Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health College of Environmental and Resource SciencesZhejiang University

Soil pore size distribution(PSD) directly influences soil physical,chemical,and biological properties,and further knowledge of soil PSD is very helpful for understanding soil functions and *** this study,PSD of three clayey soils collected from the topsoil(0-20 cm) of Vertisols in Northern China was analyzed using the N_2 adsorption(NA) and mercury intrusion porosimetry(MIP) *** effect of soil organic matter(SOM) on the PSD of clayey soils was also *** differential curves of pore volume of clayey soils by the NA method exhibited that the pores with diameter 75 μm,31.4%),cryptopores(0.1-0.007μm,16.0%),micropores(30-5 μm,9.7%) and mesopores(75-30 μm,7.3%).The SOM greatly affected the pore structure and PSD of aggregates in clayey *** particular,SOM removal reduced the volume and porosity of 5-100 μm pores while increased those of <5 μm pores in the 5-2 and 2-0.25 mm aggregates of clayey *** increase in the volume and porosity of < 5 μm pores may be attributed to the disaggregation and partial emptying of small pores caused by the destruction of SOM.

关键词： mercury intrusion porosimetry N2 adsorption pore volume porosity soil aggregate Vertisol

Systoles of hyperbolic surfaces with big cyclic symmetry

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Science China Mathematics 2021年第2期64卷 421-442页

作者： sheng Bai Yue gao Shicheng Wang School of Mathematical Sciences Peking UniversityBeijing 100871China

We obtain the exact values of the systoles of these hyperbolic surfaces of genus g with cyclic symmetry of the maximum order and the next maximum ***,for the genus g hyperbolic surface with order 4 g+2 cyclic symmetry,the systole is 2 arccosh(1+cosπ/(2 g+1)+cos 2π/(2 g+1))when g≥7,and for the genus g hyperbolic surface with order 4 g cyclic symmetry,the systole is 2 arccosh(1+2 cos 2π/2 g)when g≥4.

关键词： systole hyperbolic surface big cyclic symmetry

Grain boundary segregation and relaxation in nano-grained polycrystalline alloys

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Science China(Physics,Mechanics & Astronomy) 2021年第2期64卷 72-90页

作者： Tong-Yi Zhang Ying-Xin gao sheng Sun Materials Genome Institute Shanghai UniversityShanghai200444China

The present study carries out systematic thermodynamics analysis of Grain Boundary(GB)segregation and relaxation in NanoGrained(NG)polycrystalline *** segregation and relaxation is an internal process towards thermodynamic equilibrium,which occurs naturally in NG alloys without any applied loads,causes deformation and generates internal *** analysis comprehensively investigates the multiple coupling effects among chemical concentrations and mechanical stresses in GBs and grains.A hybrid approach of eigenstress and eigenstrain is developed herein to solve the multiple coupling *** analysis results indicate that the GB stress and grain stress induced by GB segregation and relaxation can be extremely high in NG alloys,reaching the GPa level,which play an important role in the thermal stability of NG alloys,especially via the coupling terms between stress and *** present theoretic analysis proposes a novel criterion of thermal stability for NG alloys,which is determined by the difference in molar free energy between a NG alloy and its reference single crystal with the same nominal chemical *** the difference at a temperature is negative or zero,the NG alloy is thermal stable at that temperature,otherwise unstable.

关键词： nano-grained alloys thermal stability grain boundary segregation eigenstress eigenstrain

Influence of Shear Effects on the Characteristics of Axisymmetric Wave Propagation in a Buried Fluid‑Filled Pipe

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Chinese Journal of Mechanical Engineering 2022年第3期35卷 275-284页

作者： Ping Lu Xiaozhen sheng Yan gao Ruichen Wang State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031China School of Urban Railway Transportation Shanghai University of Engineering ScienceShanghai 201620China Key Laboratory of Noise and Vibration Research Institute of AcousticsChinese Academy of SciencesBeijing 100190China Institute of Railway Research University of HuddersfieldHuddersfield HD13DHUK

The acoustic propagation characteristics of axisymmetric waves have been widely used in leak detection of fluid-filled *** related acoustic methods and equipment are gradually coming to the market,but their theoretical research obviously lags behind the field practice,which seriously restricts the breakthrough and innovation of this *** on the fully three-dimensional effect of the surrounding medium,a coupled motion equation of axisymmetric wave of buried liquid-filled pipes is derived in detail,a contact coefficient is used to express the coupling strength between surrounding medium and pipe,then,a general equation of motion was derived which contain the pipe soil lubrication contact,pipe soil compact contact and pipe in water and ***,the corresponding numerical calculation model is established and solved used numerical *** shear effects of the surrounding medium and the shear effects at the interface between surrounding medium and pipe are discussed in *** output indicates that the surrounding medium is to add mass to the pipe wall,but the shear effect is to add *** the consideration of the contact strength between the pipe and the medium,the additional mass and the pipe wall will resonate at a specific frequency,resulting in a significant increase in the radiation wave to the surrounding *** research contents have great guiding effect on the theory of acoustic wave propagation and the engineering application of leak detection technology in the buried pipe.

关键词： Buried fluid-filled pipe Axisymmetric waves Shear effect Dispersion