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Introduction of fretting-contact-induced crack closure: Numerical simulation of crack initiation and growth path in disk/blade attachment

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Chinese Journal of Aeronautics 2019年第8期32卷 1923-1932页

作者： Chen HU Dasheng WEI Yanrong WANG Xianghua JIANG school of energy and power engineering Beihang University

Fretting fatigue crack initiation and growth in titanium alloy dovetail assembly was investigated by the Finite Element Method(FEM). Firstly, contact stress was calculated precisely with an elastic–plastic material model. Secondly, the location and angle of crack initiation were determined by the parameter of the maximum shear stress range on the critical plane, and the angle of crack growth was predicted by the Maximum Tangential Stress(MTS) criterion, which showed agreement with experimental observation. Finally, the fretting-contact-induced crack closure behavior was simulated by the node release technique in software ABAQUS with both elastic and elastic–plastic material models. The simulation shows that the variation of the contact status between fretting surfaces will result in crack closure even for the elastic material model. The fretting crack closure ratio decreases as the crack grows out of the contact area and it has great impact on the effective range of Stress Intensity Factor(SIF) as well as the crack growth rate.

关键词： Crack closure Crack growth Crack initiation Finite element method Fretting fatigue

Effect of Geometrical Parameters on Submerged Cavitation Jet Discharged from Profiled Central-body Nozzle

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Chinese Journal of Mechanical engineering 2013年第3期26卷 476-482页

作者： YANG Minguan XIAO Shengnan KANG Can WANG Yuli school of energy and power engineering Jiangsu University

The flow characteristics of cavitation jets are essential issues among relevant studies. The physical properties of the jet are largely determined by the geometrical parameters of the nozzle. The structure and cavitation jets characteristics of the angular-nozzle and the self-resonating cavitation nozzle have been extensively studied, but little research is conducted in the central-body cavitation nozzle mainly because of its hard processing and the cavitation jet effect not satisfactory. In this paper, a novel central-body nozzle (a non-plunger central-body nozzle with square outlet) is studied to solve above problems. Submerged jets discharged from the novel central-body nozzle are simulated, employing the full cavitation model. The impact of nozzle configuration on jet properties is analyzed. The analysis results indicate that when central-body relative diameter keeps constant, there is an optimal contraction degree of nozzle’s outlet, which can induce intense cavitation in the jet. The central-body relative diameter also affects jet profiles. In the case of large central-body relative diameter, most of the bubbles settle in the jet core. On the contrary, a smaller relative diameter makes bubbles concentrate in the interface between the jet and its surrounding fluid. Moreover, the shorter outlet part allows the cavitation zone further extend in both the axial and racial directions. The research results further consummate the study on the central-body nozzles and the correlation between cavitation jet and the structure, and elementarily reveal the mechanism of cavitation jet produced in a non-plunger novel central-body nozzle and the effect of the structure parameters on the cavitation jet, moreover, provide the theoretical basis for the optimal design of the nozzle.

关键词： central-body nozzle cavitation jet square-outlet numerical simulation

In-phase thermal–mechanical fatigue investigation on hollow single crystal turbine blades

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Chinese Journal of Aeronautics 2013年第6期26卷 1409-1414页

作者： Wang Rongqiao Jing Fulei Hu Dianyin school of energy and power engineering Beihang University

Thermal-mechanical fatigue（TMF）is the primary cause of failure of nickel-based single crystal turbine *** experiments have been performed on the critical section which is subjected to the most serious damage and determined by numerical calculation combined with service failure *** experimental system including the loading,heating,air cooling,water cooling,and control subsystems,is constructed to satisfy the TMF experimental *** experimental system can simulate the stress feld,temperature feld,air cooling process,and TMF spectrum on the critical section under service conditions in a laboratory environment.A metal loading device and a new induction coil are developed to achieve the required stress and temperature distributions on the critical section,*** experimental results have indicated that cracks initiated at the trailing edge of the suction surface on the critical *** on these experiments,life prediction and failure analysis of hollow single crystal turbine blades can be investigated.

关键词： Experiment Induction heating Single crystal superalloy Thermal-mechanical fatigue(TMF) Turbine blade

A surface parametric control and global optimization method for axial flow compressor blades

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Chinese Journal of Aeronautics 2019年第7期32卷 1618-1634页

作者： Jinxin CHENG Jiang CHEN Hang XIANG school of energy and power engineering Beihang University

An aerodynamic optimization method for axial flow compressor blades available for engineering is developed in this paper. Bezier surface is adopted as parameterization method to control the suction surface of the blades, which brings the following advantages:(A) significantly reducing design variables;(B) easy to ensure the mechanical strength of rotating blades;(C) better physical understanding;(D) easy to achieve smooth surface. The Improved Artificial Bee Colony(IABC) algorithm, which significantly increases the convergence speed and global optimization ability, is adopted to find the optimal result. A new engineering optimization tool is constructed by combining the surface parametric control method, the IABC algorithm, with a verified Computational Fluid Dynamics(CFD) simulation method, and it has been successfully applied in the aerodynamic optimization for a single-row transonic rotor(Rotor 37) and a single-stage transonic axialflow compressor(Stage 35). With the constraint that the relative change in the flow rate is less than0.5% and the total pressure ratio does not decrease, within the acceptable time in engineering, the adiabatic efficiency of Rotor 37 at design point increases by 1.02%, while its surge margin 0.84%,and the adiabatic efficiency of Stage 35 0.54%, while its surge margin 1.11% after optimization, to verify the effectiveness and potential in engineering of this new tool for optimization of axial compressor blade.

关键词： Aerodynamic optimization Bezier surface Compressor Global optimization Surface parametric control

A physically based methodology for predicting anisotropic creep properties of Ni-based superalloys

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Rare Metals 2016年第8期35卷 606-614页

作者： Jia Huang Duo-Qi Shi Xiao-Guang Yang school of energy and power engineering Beihang University

This paper is focused on developing suitable methodology for predicting creep characteristics （i.e., the minimum creep strain rate, stress rupture life and time to a specified creep strain） of typical Ni-based directionally solidified （DS） and single-crystal （SC） superalloys. A modem method with high accuracy on simulating wide ranging creep properties was fully validated by a sufficient amount of experimental data, which was then developed to model anisotropic creep characteristics by introducing a simple orientation factor defined by the ultimate tensile strength （UTS）. Physical confidence on this methodology is provided by the well-predicted transitions of creep defor- mation mechanisms. Meanwhile, this method was further adopted to innovatively evaluate the creep properties of different materials from a relative perspective.

关键词： Wilshire equations Anisotropic creepproperties Ni-based superalloy Prediction methodologyCreep mechanism

Experimental study by PIV of swirling flow induced by trapezoid-winglets

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Journal of Hydrodynamics 2013年第6期25卷 919-928页

作者：车翠翠田茂诚张冠敏冷学礼 school of energy and power engineering Shandong University

The characteristics of the longitudinal vortex induced by trapezoid-winglets in a circular tube are investigated by the Particle Image Velocimetry （PIV） Technique with flow Reynolds number in the range of 500-13 000. In the experimental test section, four trapezoid-winglets are fixed symmetrically on the tube wall in two different ways： up-flow and down-flow. The results show that a counter-rotating vortex pair is formed behind each winglet and they distribute as a symmetrical vortex array in the transverse section. Between the two vortexes in a vortex pair the fluid flows towards the wall in the up-flow winglet case and away from the wall in the down-flow winglet case, corresponding also to the regions of peak values of the velocity components normal to the mainstream. Both of the flow patterns enhance the velocity in the near wall region, leading to the intensification of the transverse mixing and the mass transfer in the tube. With Reynolds number increasing, the flow maintains the vortex pattern in the case of the up-flow winglets, indicating better persistence of the longitudinal vortex, while the vortexes in the case of the down-flow winglets are more scattered and tend to breaking into small eddies. The trapezoid winglet shows the preferable turbulent disturbance characteristics in the tube and the experimental results provide benchmark data for further CFD studies.

关键词： longitudinal vortex Particle Image Velocimetry (PIV) trapezoid-winglets circular tube

Enhanced Photocatalytic Degradation of Rhodamine B by Cu_2O Coated Silicon Nanowire Arrays in Presence of H_2O_2

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Journal of Materials Science & Technology 2014年第11期30卷 1124-1129页

作者： Chengtao Yang Jinliang Wang Lirun Mei Xiaoyu Wang school of Physics and nuclear energy engineering Beihang University

Highly ordered Cu2O coated silicon nanowire arrays （SiNWAs） were fabricated as photocatalyst via depositing Cu nanoparticles on silver-assisted electroless-etched SiNWAs and subsequently annealing. The as-prepared samples have been characterized by scanning electron microscopy, X-ray diffraction and UV-VIS-NIR spectrophotometry. The photocatalytic properties of the Cu2O coated SiNWAs were investigated by degradation of Rhodamine B （RhB） under simulated solar light with a cut-off filter （λ 〉 420 nm）. The results indicated that H2O2 could greatly improve the photocatalytic properties of Cu2O coated SiNWAs, and exhibited strong synergy effect between them. The hybrid nanowire arrays will be promising photocatalytic materials in the field of energy and environment.

关键词： Silicon nanowire arrays Cu2O p-n junction H2O2 Photocatalytic degradation

A study on the catalytic performance of carbide slag in transesterification and the calculation of kinetic parameters

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Science China(Technological Sciences) 2015年第2期58卷 258-265页

作者： LIU Meng Qi NIU Sheng Li LU Chun Mei LI Hui HUO Meng Jia school of energy and power engineering Shandong University

The catalytic performance of carbide slag in transesterification is investigated and the reaction kinetic parameters are calculated. After being activated at 650℃, calcium compounds of carbonate and hydroxide in the carbide slag are mainly transformed into calcium oxide. The activated carbide slag utilized as the transesterification catalyst is characterized by X-ray diffraction （XRD）, attenuated total reflectance-Fourier transform infrared spectroscopy （ATR-FTIR）, nitrogen adsorption-desorption and the Hammett indicator method. Compared with the carbide slag activated at 700 and 800℃, the largest surface area of 22.63 m2g^-1, the smallest particle size of 265.12 nm and the highest catalytic efficiency of the carbide slag activated at 650℃ guarantee its capacity in catalyzing transesterification. Then, the influences of activated temperature （Ta）, molar ratio of methanol to oil （γ）, catalyst added amount （ζ）, reaction temperature （Tr） and reaction time （τ） on the catalytic performance are investi- gated. Under the optimal transesterification condition of Ta=650℃, γ=15, ζ=3%, Tr=60℃ and τ=-110 rain, the catalytic efficiency of 92.98% can be achieved. Finally, the kinetic parameters of transesterification catalyzed by the activated carbide slag are calculated, where activation energy （E） is 68.45 kJ mol^-1 and pre-exponential factor （k0） is 1.75×10^9 min^-1. The activated carbide slag shows better reused property than calcium hydroxide.

关键词： transesterification catalyst carbide slag kinetic parameters

The direct numerical simulation of pipe flow

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Journal of Hydrodynamics 2013年第1期25卷 125-130页

作者： LIU Zheng-gang DU Guang-sheng SHAO Zhu-feng school of energy and power engineering Shandong University

The conservative difference scheme and the third-order Runge-Kutta scheme in combination with the the Crank-Nicholson scheme are used to directly simulate the flow field in a pipe with the Reynolds number of 2 600. The flow field, including the velocity distribution and the turbulence intensity, is obtained by the direct numerical simulation. From the calculated results, the ratio of the linear average velocity along the ultrasonic propagation path to the profile average velocity on the pipe cross-section is also obtained in an ultrasonic flow meter. It is concluded that the direct numerical simulation method can be used to study the ratio of the profile-linear average velocity at low Reynolds number conditions in the transition region and to improve the measurement accuracy of the ultrasonic flow meter.

关键词： Direct Numerical Simulation (DNS) pipe turbulence intensity Reynolds stress