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Numerical study of convective heat transfer of a supersonic combustor with varied inlet flow conditions

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Acta Mechanica sinica 2019年第5期35卷 943-953页

作者： W.h.Fan F.q.Zhong s.G.Ma X.Y.Zhang state Key Laboratory of high Temperature Gas Dynamics Institute of MechanicsChinese Academy of SciencesBeijing 100190 China school of Engineering science University of Chinese Academy of SciencesBeijing 100049China

Characteristics of convective heat transfer of a supersonic model combustor with variable inlet flow conditions were studied by numerical simulation in this *** three-dimensional flow and wall heat flux at different air inlet Mach numbers of 2.2,2.8 and 3.2 were studied numerically with Reynolds-averaged Navier-stokes equations with a shear-stress transport(ssT)k-ωturbulence model and a three-step reaction ***,ethylene was chosen as the fuel,and the fixed fuel-to-air equivalence ratio is 0.8 in all cases in this *** results of the simulations indicate that wall heat flux distribution of the combustor is very non-uniform with several peaks of wall heat flux at varied *** the low inlet Mach number of 2.2,a shock train structure is formed in the isolator,and three peaks of wall heat flux are located respectively on the backward face of the cavity,on the side wall near the fuel injection and on the bottom wall near the injection holes,and a maximum wall heat flux reaches 5.4 MW/*** the medium inlet Mach number of 2.8,there exists a much shorter shock structure with three peaks of wall heat flux similar to that of Mach number ***,as the inlet Mach number increased to 3.2,there is no shock structure upstream of fuel injections,and the combustor flow is in a supersonic mode with different locations and values of wall heat flux *** statistical results of wall heat loading show that the change of total wall heat is not monotonic with the increase of inlet Mach number,and the maximum appears in the case of Mach number being ***,for all the cases,the bottom wall takes up more than 50%of the total heat loading.

关键词： Wall heat flux Numerical simulation Ethylene supersonic combustor

DEFORMATION BEhAVIOR OF AA6063 ALUMINIUM ALLOY AFTER REMOVING FRICTION EFFECT UNDER hOT WORKING CONDITIONs

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Acta Metallurgica sinica(English Letters) 2008年第6期21卷 451-458页

作者： Z. Y. Chen s. q. Xu X.h. Dong National Die ＆ Mold CAD Engineering Research Center Shanghai Jiaotong University Shanghai 200030 China College of Materials science and Engineering Taiyuan University of Technology Taiyuan 030024 China

The hot deformation behavior of AA6063 aluminium alloy has been investigated by means of compression tests at temperatures between 400 and 520℃, and strain rates ranging from 2.5 to 10 s^-1. Owing to the barreling, the theoretical model on the basis of hills general method is used to calculate the flow stress of a cylindrical specimen under uniaxial simple compression so as to consider the friction effect at the die-specimen interface. A method of evaluating the friction coefficient by combining compression tests with the finite element method is presented. The real flow behavior of AA6063 aluminium alloy can be described with sinh-Arrhenius equation. The hot deformation activation energy q derived from the corrected stress and strain data is 232. 350 kJ/mol.

关键词： Barreling Compression test Friction Flow stress Aluminium alloy Activation energy

Convexification of hybrid AC-DC Optimal Power Flow with Line-Commutated Converters

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CsEE Journal of Power and Energy systems 2024年第2期10卷 617-628页

作者： hongyuan Liang Zhigang Li J.h.Zheng q.h.Wu school of Electric Power Engineering South China University of TechnologyGuangzhou 510641China

Line-commutated converter (LCC)-based high-voltage DC (hVDC) systems have been integrated with bulk AC power grids for interregional transmission of renewable power. The nonlinear LCC model brings additional nonconvexity to optimal power flow (OPF) of hybrid AC-DC power grids. A convexification method for the LCC station model could address such nonconvexity but has rarely been discussed. We devise an equivalent reformulation for classical LCC station models that facilitates second-order cone convex relaxation for the OPF of LCC-based AC-DC power grids. We also propose sufficient conditions for exactness of convex relaxation with its proof. Equivalence of the proposed LCC station models and properties, exactness, and effectiveness of convex relaxation are verified using four numerical simulations. simulation results demonstrate a globally optimal solution of the original OPF can be efficiently obtained from relaxed model.

关键词： AC-DC power system convex relaxation linecommutated converter optimal power flow second-order cone programming

MICROsTRUCTURAL ChARACTERIsTICs AssOCIATED WITh hIGh- sTRAIN-RATE PLAsTIC DEFORMATION IN ThE ELECTROFORMED COPPER LINER OF shAPED ChARGEs

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Acta Metallurgica sinica(English Letters) 2005年第5期18卷 620-626页

作者： A.L. Fan W.h. Tian q. suns B.s. Wang Department of Materials Physics and Chemistry University of Science and Technology Beijing Beijing 100083 China Taiyuan University of science and Technology Taiyuan 030024 China 210 Institute The Chinese Ordnance Industry Institute Beijing 100081 China

The microstructures of electroformed copper liners of shaped charges that had undergone high-strain-rate deformation were observed by optical microscopy （OM） and scanning electron microscopy （sEM）. Meanwhile, the orientation distribution of the grains in the recovered jet was examined by electron backscattering Kikuchi pattern （EBsP） technique. EBsP analysis reveals that the fibrous texture observed in the as-electroformed copper liners disappeared after explosive detonation deformation. OM observation shows that the microstructure evolves system- atically from the jet center to its perimeter during cooling from high temperatures after explosive detonation deformation. This microstructural characteristic is similar to that of solidification, i.e. there exist equiaxed grains in the center of the jet and significant columnar grains around the equiaxed grains. The result reveals that there is melting-related phenomenon in the jet center. Corresponding microhardness variations from the jet center to its perimeter is also determined. All the phenomena can be explained by a strong gradient of temperature across the section of the jet during plastic deformation at high-strain-rate.

关键词： jetting electroformation microstructure hardness,ultra-high strain rate deformation

Dispatchable Region for Active Distribution Networks Using Approximate second-order Cone Relaxation

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CsEE Journal of Power and Energy systems 2023年第6期9卷 1999-2007页

作者： Zhigang Li Wenjing huang J.h.Zheng q.h.Wu school of Electric Power Engineering South China University of TechnologyGuangzhou 510640China

Uncertainty in distributed renewable generation threatens the security of power distribution *** concept of dispatchable region is developed to assess the ability of power systems to accommodate renewable generation at a given operating *** DC and linearized AC power flow equations are typically used to model dispatchable regions for transmission systems,these equations are rarely suitable for distribution *** achieve a suitable trade-off between accuracy and efficiency,this paper proposes a dispatchable region formulation for distribution networks using tight convex *** cone relaxation is adopted to reformulate AC power flow equations,which are then approximated by a polyhedron to improve ***,an efficient adaptive constraint generation algorithm is employed to construct the proposed dispatchable *** studies on distribution systems of various scales validate the computational efficiency and accuracy of the proposed method.

关键词： Dispatchable region distribution system renewable power generation second-order cone relaxation uncertainty

solid-state Interfacial Reaction between Eutectic Au-Ge solder and Cu/Ni(P)/Au Metalized Ceramic substrate and Its suppression

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Journal of Materials science & Technology 2015年第5期31卷 445-452页

作者： F.q.Lang h.Yamaguchi h.Nakagawa h.sato Advanced Power Electronics Research Center(ADPERC) National Institute of Advanced Industrial Science and Technology(AIST).Central 21-1-1UmezonoTsukubaIbaraki 305-8568.Japan

Eutectic Au-12 Ge solder was employed to bond the siC power devices to a si3N4/Cu/Ni（P）/Au multilayered *** high-temperature reliability of the bond was investigated in detail at 200,250,300 and 330 ℃,*** and Ni5Ge3intermetallic compounds（IMCs） were identified at the Au-12Ge/Ni（P） interface by micro X-ray diffraction（μXRD） and scanning electron microscopy（sEM）equipped with energy dispersive X-ray analysis（EDX）.The growth of the Ni-Ge IMCs was dominated by Ni5Ge3layer,which formed at the Ni5Ge3/NiGe interface by outward diffusion of Ni from the Ni（P） *** activation energy of the total Ni-Ge IMCs growth was 66 kJ/*** shear strength of the bond was tested at both 25 ℃ and the aging temperatures,*** shear strength decreased slightly after aging at 200 and 250 ℃.The shear strength tested at 250 ℃ was 46 MPa after aging at 250 ℃ for 3000 *** shear strength aged at 300 and 330 ℃ rapidly decreased with aging time due to the rapid growth of the *** slow down the interfacial reaction between the high temperature solder and the Ni（P）layer,an approximately 200 nm-thick Ta/TaN/Ta new diffusion barrier（DB） was deposited on the *** by transmission electron microscopy（TEM） equipped with EDX,reveals that the Ta/TaN/Ta DB was bonded well to the Ni（P） layer and the *** temperature storage test at 330 ℃ for1500 h reveals that the bond of the siC devices maintained its high shear strength of approximately56 MPa without *** new DB effectively suppressed the interfacial reaction between the Au-12 Ge solder and the Ni（P） layer of the substrate.

关键词： high-temperature solder Interfacial reaction Activ

MATRIX INVEsTIGATION ON IsAIChEV ORIENTATION RELATIONshIP

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Acta Metallurgica sinica(English Letters) 1999年第2期12卷 185-190页

作者： sheng, Z.q. Xiao, h. Nuclear Power Inst of China Chengdu China

By means of TEM technique the orientation relationships of cementite, precipitated from islands of granular bainite during tempering, with ferrite have been observed. By calculating the eigenvalues and eigenvectors of transformation matrix, Isaichev relationship has been analyzed. The results indicate that Isaichev relationship is indeed the sum of Kurdjumov-sachs relationship and Pitsch relationship, so the viewpoint that the cementite with Isaichev relationship precipitates from austenite, instead of ferrite, was confirmed. Moreover, the matrix calculation shows that three reported orientation relationships among austenite, ferrite and cementite in pearlitic transformation cannot be simultaneously valid. (Edited author abstract) 4 Refs.

关键词： Carbides Crystal orientation Eigenvalues and eigenfunctions Nuclear reactors Pearlitic transformations Phase transitions

Deformation behavior of laser bending of circular sheet metal

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Chinese Optics Letters 2011年第5期9卷 47-51页

作者： q.Nadeem s.J.Na Department of Mechanical Engineering KAIST

The application of a thermal source in non-contact forming of sheet metal has long been used. however, the replacement of this thermal source with a laser beam promises much greater controllability of the process. This yields a process with strong potential for application in aerospace, shipbuilding, automobile, and manufacturing industries, as well as the rapid manufacturing of prototypes and adjustment of misaligned components. Forming is made possible through laser-induced non-uniform thermal stresses. In this letter, we use the geometrical transition from rectangular to circle-shaped specimen and ring-shaped specimen to observe the effect of geometry on deformation in laser forming. We conduct a series of experiments on a wide range of specimen geometries. The reasons for this behavior are also analyzed. Experimental results are compared with simulated values using the software ABAqUs. The utilization of line energy is found to be higher in the case of laser forming along linear irradiation than along curved ones. We also analyze the effect of strain hindrance. The findings of the study may be useful for the inverse problem, which involves acquiring the process parameters for a known target shape of a wide range of complex shape geometries.

关键词： Deformation behavior of laser bending of circular sheet metal

Experimental study of corner separation and unsteady characteristics in linear compressor cascades with and without sweeping jet actuator

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Propulsion and Power Research 2024年第3期13卷 360-374页

作者： s.W.Chen W.h.Li C.Xu q.h.Meng school of Energy science and Engineering Harbin Institute of TechnologyHarbinHeilongjiang 150001China AVIC shenyang Aircraft Design and Research Institute Shenyang 110035China

sweeping jet actuator(sJA)has been widely applied for activeflow control in *** this paper,the sJA character in compressor cascade and its performance for separation control in innerflows are ***-averaged and transientflowfield measurement,together with visualization methods are *** is found that endwall effects are important for both sJA behaviors and sJA performance for separation control in compressor *** is a maximum of 12.7%total pressure loss reduction with sJA placed near the separation position,close to the endwall and under *** characteristic frequencies in theflowfield contribute to the capture of influence regions of vortices and excitation *** concentrated shedding vortices and sJA jets impact region helped to judge that sJA energizes low momentumfluids in a large region and matches the high loss core *** be concrete,theflow separation control mechanism of sJA lies on the interruption of the blade suction surface boundary layer development and the restriction of the lifting of the boundary layer from end-wall towards blade suction surface.

关键词： Compressor cascade Activeflow control sweeping jet actuator Corner separation Oilflow visualization