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Effects of Number of Bleed Holes on Shock-Wave/Boundary-Layer Interactions in a Transonic Compressor Stator

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Journal of Thermal Science 2024年第2期33卷 611-624页

作者： LI Bai ZHOU Xun luo lei DU Wei School of Energy Science and Engineering Harbin Institute of TechnologyHarbin150001China

An extensive numerical investigation is conducted to characterize the flow separation control in a transonic compressor cascade with a porous *** bleed holes are arranged on the suction surface in a single row,two staggered rows and three staggered *** each bleed scheme,five bleed pressure ratios are examined at an inlet Mach number of *** results indicate that the aerodynamic performance of the cascade is significantly improved by the porous *** the single-row scheme,the maximum reduction in total pressure losses is 57%.For the two-staggered-row and three-staggered-row schemes,there is an optimal bleed pressure ratio of 1.0,and the maximum reductions in total pressure loss are 68% and 75%,*** low loss in the cascade is due to the well-controlled boundary *** new local supersonic region created by the bleed hole is the key reason for the improved boundary *** vortex induced by side bleeding provides another mechanism for delaying flow *** the bleed holes could create multiple local supersonic regions,which reduce the range of the adverse pressure gradient that the boundary layer needs to *** is the reason why cascades with more bleed holes perform better.

关键词： transonic compressor stator shock wave/boundary layer interaction porous bleed number of bleed holes

Effect of Strain Ratio on Fatigue Model of Ultra-fine Grained Pure Titanium

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Journal of Wuhan University of Technology(Materials Science) 2023年第5期38卷 1169-1178页

作者： QIANG Meng YANG Xirong LIU Xiaoyan luo lei Wuhan Institute of Marine Electric Propulsion Wuhan 430064China

The ultra-fine grained(UFG)pure titanium was prepared by equal channel angular pressing(ECAP)and rotary swaging(RS).The strain controlled low cycle fatigue(LCF)test was carried out at room *** fatigue life prediction model and mean stress relaxation model under asymmetrical stress load were *** results show that the strain ratio has a significant effect on the low cycle fatigue performance of the UFG pure titanium,and the traditional Manson-coffin model can not accurately predict the fatigue life under asymmetric stress ***,the SWT mean stress correction model and three-parameter power curve model are proposed,and the test results are *** final research shows that the threeparameter power surface model has better *** studying the mean stress relaxation phenomenon under the condition of R≠-1,it is revealed that the stress ratio and the strain amplitude are the factors that significantly afiect the mean stress relaxation rate,and the mean stress relaxation model with the two variables is calculated to describe the mean stress relaxation phenomenon of the UFG pure titanium under different strain *** fracture morphology of the samples was observed by SEM,and it was concluded that the final fracture zone of the fatigue fracture of the UFG pure titanium was a mixture of ductile fracture and quasi cleavage *** toughness of the material increases with the increase of strain ratio at the same strain amplitude.

关键词： ultra-fine grained pure titanium low cycle fatigue life model mean stress relaxation mode strain ratio fracture morphology

Soft transmission of 3D video for low power and low complexity scenario

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Digital Communications and Networks 2023年第3期9卷 769-778页

作者： Ao Li Taihai Yang Wenxin Wu lei luo School of Communications and Information Engineering Chongqing University of Posts and TelecommunicationsChongqing400065China School of Computer Science and Technology East China Normal UniversityShanghai200062China School of Information and Communication Engineering University of Electronic Science and Technology of ChinaChengdu611731China

Thanks to the rapid development of naked-eye 3D and wireless communication technology,3D video related applications on mobile devices have attracted a lot of ***,the time-varying characteristics of the wireless channel is very challenging for conventional source-channel coding based transmission ***,the high complexity of source-channel coding based transmission scheme is undesired for low power mobile *** advanced transmission scheme named Softcast was proposed to achieve efficient transmission performance for 2D image/***,it cannot be directly applied to wireless 3D video transmission with high *** paper proposes a more efficient soft transmission scheme for 3D video with a graceful quality adaptation within a wide range of channel Signal-to-Noise Ratio(SNR).The proposed method first extends the linear transform to 4 dimensions with additional view dimension to eliminate the view redundancy,and then metadata optimization and chunk interleaving are designed to further improve the transmission ***,a synthesis distortion based chunk discard strategy is developed to improve the overall 3D video quality under the condition of limited *** experimental results demonstrate that the proposed method significantly improves the 3D video transmission performance over the wireless channel for low power and low complexity scenarios.

关键词： Softcast Low power 3D video Wireless

Ablation of C/SiC-HfC composite prepared by precursor infiltration and pyrolysis in plasma wind tunnel

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Journal of Advanced Ceramics 2020年第3期9卷 393-402页

作者： Liuyang DUAN lei luo Liping LIU Yiguang WANG Science and Technology on Thermostructural Composite Materials Laboratory Northwestern Polytechnical UniversityXi'an 710072China Beijing Institute of Long March Aerospace Vehicles Beijing 100076China Ultrahigh Speed Aerodynamics Research Institute China Aerodynamics Research and Development CenterMianyang 621000China Institute of Advanced Structure Technology Bejing Institute of TechnologyHaidian DistrictBeijing 100081China

Carbon fiber reinforced silicon carbide-hafnium carbide(C/SiC-HfC)composite was prepared by precursor infiltration and pyrolysis ***,ablation behavior of C/SiC-HfC was evaluated in plasma wind *** was found that oxide layer formed during ablation significantly influenced the surface *** of dense HfO2 SiO2 layer under low heat flux led to stable surface ***(SiO2)on the surface was gradually consumed when heat flux increased,resulting in conversion of HfO2-SiO2 on the surface to *** HfO2 with high catalytic cofficient absorbed more energy,causing gradual increase in the surface *** oxide layer was destroyed at high heat flux and high stagnation point *** carbon fiber lost the protection of HfO2-SiO2 layer,it burned immediately,leading to surface temperature jump.

关键词： C/SiC-HfC composite precursor infilration and pyrolysis ablation plasma wind tunnel

Design Methods and Strategies for Forward and Inverse Problems of Turbine Blades Based on Machine Learning

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Journal of Thermal Science 2022年第1期31卷 82-95页

作者： ZHOU Haimeng YU Kaituo luo Qiao luo lei DU Wei WANG Songtao School of Energy Science and Engineering Harbin Institute ofTechnologyHarbin 150001China

To study the feasibility of using machine learning technology to solve the forward problem(prediction of aerodynamic parameters)and the inverse problem(prediction of geometric parameters)of turbine blades,this paper built a forward problem model based on backpropagation artificial neural networks(BP-ANNs)and an inverse problem model based on radial basis function artificial neural networks(RBF-ANNs).The S2(a stream surface obtained by extending a radial curve in turbo blades)calculation program was used to generate the dataset for single-stage turbo blades,and the back propagation algorithm was used to train the *** parameters of five blade sections in a single-stage turbine were selected as inputs of the forward problem model,including stagger angle,inlet geometric angle,outlet geometric angle,wedge angle of leading edge pressure side,wedge angle of leading edge suction side,wedge angle of trailing edge,rear bending angle,and leading edge *** outputs are efficiency,power,mass flow,relative exit Mach number,absolute exit Mach number,relative exit flow angle,absolute exit flow angle and reaction degree,which are eight aerodynamic *** inputs and outputs of the inverse problem model are the opposite of that of the forward problem *** models can accurately predict the aerodynamic parameters and geometric parameters,and the mean square errors(MSEs)of the forward problem test set and the inverse problem test set are 0.001 and 0.00035,*** study shows that machine learning technology based on neural networks can be flexibly applied to the design of forward and inverse problems of turbine blades,and the models built by this method have practical application value in regression prediction problems.

关键词： turbine blade forward and inverse problem machine learning neural networks parameter prediction

Flow Analysis of Tandem Blades as the Outlet Vane of a Highly Loaded Compressor

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Journal of Thermal Science 2024年第6期33卷 2005-2018页

作者： luo Qiao luo lei DU Wei YAN Han WANG Songtao ZHOU Xun School of Energy Science and Engineering Harbin Institute of TechnologyHeilongjiang 150001China

A tandem blade configuration is a significant flow control method that delays the onset of flow *** study numerically investigates the effects of diffusion factor and percentage pitch on the flow structure of tandem *** factors vary from 0.328 to *** pitches change from 0.80 to *** show that the loss coefficient increases with diffusion factor and decreases with percentage *** is a hub-corner stall of the forward blade in all *** flow determines the rear blade corner *** the percentage pitch and diffusion factor changes the momentum distribution of the gap *** separation of the rear blade is inhibited as low-momentum gap fluids are involved in the passage vortex along with the hub-corner stall of the forward *** diffusion factor causes a change in incidence at the leading edge of the rear blade,resulting in a variation at the corner separation of the rear blade.A tandem blade is compared with the reference outlet *** performance of the tandem blade is superior to that of the reference outlet vane in all incidences,with a 26.35%reduction in the loss coefficient and a 7.89%enhancement in the pressurization at the designed *** blades stall at positive incidence because of the hub-corner stall of the forward *** intensity of the gap flow increases with incidence,preventing corner separation of the rear blade at positive incidences.

关键词： compressor tandem blade loss corner separation gap flow

Tension-Compression Asymmetry in Ultrafine-grained Commercially Pure Ti Processed by ECAP

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Journal of Wuhan University of Technology(Materials Science) 2023年第3期38卷 689-694页

作者：刘晓燕 LI Shuaikang YANG Xirong luo lei School of Metallurgical Engineering Xi'an University of Architecture and TechnologyXi'an 710055China

A homogenous microstructure of ultrafine-grained (UFG) commercially pure (CP) Ti characterized by equiaxed grains/subgrains with an average grain size of about 150 nm and strong prismatic fiber texture were obtained after 4 passes of equal channel angular pressing (ECAP).Tension–compression asymmetry in yield and work hardening behavior of UFG CP Ti were investigated by uniaxial tension and compression *** experimental results reveal that UFG CP Ti exhibits a relatively obvious tensioncompression asymmetry in yielding and work hardening *** basal and prismaticslip are suppressed either for tension or compression,which is the easiest to *** tension twin system{1012} easily activated in compression deformation due to the prismatic fiber texture based on the Schmidt factor,consequently resulting in a lower yield strength under compression than *** can improve the tension-compression asymmetry of CP Ti due to grain *** interaction among the dislocations,grain boundaries and deformation twins are the main work hardening mechanisms for compression deformation,while the interaction between the dislocations and grain boundaries for tension *** twins lead to the higher work hardening under compression than tension.

关键词： ultrafine-grained commercially pure Ti equal channel angular pressing tensioncompression asymmetry texture twinning

Investigation of the Vortex Dynamic Mechanism of the Flow Losses on a Transonic Compressor Stator

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Journal of Thermal Science 2019年第1期28卷 51-60页

作者： KAN Xiaoxu WANG Songtao luo lei SU Jiexian School of Energy Science and Engineering Harbin Institute of Technology

For a transonic axial-flow compressor, the numerical simulations, verified against experimental data, were used to study the inherent correlation between the evolutionary process of the vortex structures and the flow loss in a compressor stator passage during the throttling process. The flow loss was divided accurately and quantitatively, based on the evolutionary process of the vortex structures. According to the position of the singular points of the vortex structures, the influence of the evolution of the vortex structures on the generation and development of the flow loss was analyzed on a microscale scale. Thereafter, this paper provided the vortex dynamic mechanism of the flow loss, which was important to enrich the theoretical system of the flow field in the compressor. The results show that: the flow loss at the top of the stator tip is caused by the low-energy fluid clusters, which are transported and accumulated by the vortices from the endwall; the transport effect of the pressure separation vortex at the upper half-height only migrates the position of the flow losses, but there is new flow loss generated by its shear action to the endwall. The dominant flow loss during the throttling process concentrates upon the closed separation bubble around the middle of the suction side of the stator.

关键词： transonic compressor stator throttling process vortex structure flow losses topological analysis

Optimizing microstructure,shrinkage defects and mechanical performance of ZL205A alloys via coupling travelling magnetic fields with unidirectional solidification

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Journal of Materials Science & Technology 2021年第15期74卷 246-258页

作者： lei luo Liangshun luo Yanqing Su Lin Su Liang Wang Jingjie Guo Hengzhi Fu National Key Laboratory for Precision Hot Processing of Metals School of Materials Science&EngineeringHarbin Institute of TechnologyHarbin 150001China Office of International Cooperation University of Science and Technology of ChinaHefei 230026China

ZL205A alloys tend to form disordered and defective microstructure due to the large solidification intervals and ***,finding ways to effectively optimize the microstructure and mechanical performance is of great *** this regard,the coupling of travelling magnetic fields(TMF)with unidirectional solidification was used to continuously regulate the mushy zones of ZL205A ***,experiments are combined with simulations to systematically reveal the mechanisms on the optimizations at each stage of solidification *** findings demonstrate that different directional strong melt flows generated by TMF are responsible for these ***,the effects of TMF on microstructure are different at each stage of solidification ***,downward TMF coupled with unidirectional solidification can refine and uniform the microstructure,decrease the formation of precipitation,promote the growth consistency of matrix phaseα-Al growing along thecrystal orientation,reduce the secondary dendrites and overlaps between dendrites,eliminate the shrinkage defects,and increase the ultimate tensile strength,yield strength,elongation and hardness from 198.3 MPa,102.2 MPa,7.5%and 82.3 kg mm^(-2)without TMF to 225.5 MPa,116.1 MPa,13.6%and 105.2 kg mm^(-2).Contrastively,although upward TMF can reduce Al3Ti and refineα-Al,it increases the formation of Al6Mn,Al2Cu,secondary dendrites,overlaps between dendrites,and shrinkage defects;then it deflects and disorders the growth ofα-Al,further to decrease the overall performance of alloys.

关键词： ZL205A solidification microstructure