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Impact of Wake on Downstream Adjacent Rotor in Low-speed Axial Compressor

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Journal of Thermal Science 2004年第2期13卷 114-120页

作者： Xinqian Zheng Sheng Zhou Beijing univ aeronaut & astronaut Sch Jet Prop Beijing 100083 Peoples R China

This paper investigates the effect of upstream wake on unsteady separated flow field of downstream adjacent vanes by solving 2D unsteady Reynolds-averaged Navier-Stokes equations discretized by a high-order scheme. The results indicated that the maximum relative reduction of loss coefficient was 27.2% when the relative passing frequency (the ratio of wake passing frequency to the characteristic frequency of trailing-vortex shedding of downstream adjacent rotor) is less than 2.5. The amplitude of wake defect exists a threshold value and the aerodynamic performance is enhanced monotonically with the amplitude of wake defect basically. The effective range of incidence must be greater than 8°, which is near the stall boundary.

关键词： unsteady flow separated flow rotor/stator interaction axial flow compressor.

Influence of Controlled Rolling and Cooling Process on the Mechanical Properties of Low Carbon Cold Forging Steel

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Journal of Iron and Steel Research International 2011年第S1期18卷 595-599页

作者： LI Zhuang 1,WU Di 2,ZHENG Hui 1,DONG Xue-xin 2 (1.School of Materials Science and Engineering,shenyang university of aeronautics and astronautics,shenyang 110136,Liaoning,China 2.State Key Laboratory of Rolling and Automation,Northeastern university,shenyang 110004,Liaoning,China) shenyang univ aeronaut & astronaut Sch Mat Sci & Engn Shenyang 110136 Liaoning Peoples R China Northeastern univ State Key Lab Rolling & Automat Shenyang 110004 Liaoning Peoples R China

In the present paper,controlled rolling and cooling processing was conducted by using a laboratory hot rolling *** influence of different processing parameters on the mechanical properties of low carbon cold forging steel was *** results show that the faster cooling after the deformation (especially in low temperature rolling conditions) leads to the refinement of the ferrite *** specimen exhibits very good mechanical properties owing to the finer ferrite *** pearlite morphologies can also affect the mechanical properties of low carbon cold forging *** mechanical properties increase with decreasing final cooling temperature within the range from 650℃ to 570 ℃ due to the finer interlamellar spacing of pearlite *** mechanical properties of the specimens with fast cooling after the conventional rolling are not only better than those of the specimens with slow cooling after low temperature rolling,but also almost similar to those of the specimens with fast cooling after low temperature *** is suggested that fast cooling after high temperature rolling (the conventional rolling) process would be of important industrial value.

关键词： controlled rolling and cooling process low carbon cold forging steel fast cooling the finer ferrite grains mechanical properties

Crack Damage Accumulation in Equal-Channel Angular Pressing of 6061 Al

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稀有金属材料与工程 2011年第S3期40卷 294-297页

作者： Zhou Qing, Gao Lin, Chen Minghe, Chen Wenjie, Duan Yupeng Nanjing university of aeronautics and astronautics, Nanjing 210016, China Nanjing univ aeronaut & astronaut Nanjing 210016 Peoples R China

Crack damage factor expressed by Normalized Cockcroft & Latham (N C&L) criterion was used for estimating the crack damage accumulation during multiple passes equal-channel angular pressing (ECAP) of 6061Al rod. First the simulation of crack damage factor was carried out by a software DEFORM-3D, and then the ECAP experiments of 6061 rod were performed. The damage places were found locating at the upper and bottom surface of the rod after ECAP. It has also been demonstrated that the ECAP routes including route A, Bc and C have strong effects on the strain distribution and the strain accumulation from both the experiment and the simulation.

关键词： ECAP 6061 aluminum alloy crack damage ductile fracture

Aging Effect on Elapsed Time of Serrations in Al-Li Single Crystals

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Journal of Materials Science & Technology 1998年第4期14卷 353-356页

作者： Tian, BH Yan, MG Chen, CQ Beijing Inst aeronaut Mat Beijing 100095 Peoples R China Beijing univ aeronaut & astronaut Beijing 100083 Peoples R China

Elapsed time of serrations in AI-Li single crystals was investigated with two definitions: one is the time elapsed in one cycle of serrations, the other is the average elapsed time within a strain limit. Elapsed time of individual serration appears independent on stress drops during serrated flow. It primarily distributes within the limits of short elapsed time in peak aged condition compared with underaged and overaged conditions, corresponding to low level of the average elapsed time that appears indifferent to increasing strain. It seems that shearing behaviour of delta' particles could be responsible for the variations in elapsed time of serrations.

关键词： Aluminum alloys

Modified Moving Particle Semi-Implicit Meshless Method for Incompressible Fluids

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Journal of Thermal Science 2004年第3期13卷 226-234页

作者： Jun Guo Zhi Tao Beijing univ aeronaut & astronaut Div 402 Dept Jet Prop Beijing 100083 Peoples R China

A modified moving particle semi-implicit method (MPS) is presented for incompressible fluids. Modification is on the removal of imaginary nodes to enforce the boundary conditions. Comparison with the original imaginary-node scheme has proved the validity of the proposed method. Performance of MPS method in general is also investigated by comparing the results of Lid-driven and natural convection problems with finite volume method (FVM). It is found that MPS method shows relatively strong numerical diffusion, and for convection problems, MPS method appears to be less robust than FVM. Though better results could be obtained with different kernel functions, such improvement is quite limited.

关键词： meshless method incompressible fluids numerical diffusion kernel function.

Grid Generation and Numerical Analysis of Multi-Stream Flow in the Complex Channel with a Forced Mixer Lobe

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Journal of Thermal Science 2004年第2期13卷 167-173页

作者： Suofang Wang Liguo Li Jingzhou Zhang Nanjing univ aeronaut & astronaut Coll Energy & Power Engn Nanjing 210016 Jiangsu Peoples R China

The co-located grid, SIMPLEC and Chen-Kim modified k - E turbulence model are applied to investigate numerically the multi-stream flow and temperature fields in the complex channel with a forced mixer lobe at room temperature and at elevated temperature. The body-fitted coordinate grids are generated respectively in sub-domains according to the shapes of the channel by solving Poisson’s equations to compose the whole grid of the domain. The large viscosity, linear and simultaneous under-relaxation factors are used to solve the coupling of fluid and solid. The solid grid is complemented at the upper inlet of the secondary flow to keep the same node number at the inlet and at double-wall sub-domains. The numerical results and experimental data show good agreement at room temperature. It is illustrated that the cooling air ejected into the slot between the double plates decreases the temperature of the wall.

关键词： body-fitted coordinate multi-stream flow lobe ejector double-wall.

Frequency Analyses for Mechanism Research of Unsteady Flow Inside Three Dimensional Compressor Cascade

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Journal of Thermal Science 2004年第3期13卷 207-212页

作者： Sheng Zhou Hongbin Wu Xinqian Zheng Beijing univ aeronaut & astronaut Natl Key Lab Aircraft Engine Beijing 100083 Peoples R China

Numerical simulations are carried out for unsteady flow field of certain kind of 3D compressor cascade. Emphasis is laid on vortex shedding and frequency analysis in a compressor cascade. Numerical simulations using unsteady Reynolds-averaged viscous turbulent equations are carried out. The results show that the flows in separated areas and wake areas are characterized as periodic or quasi-periodic vortex shedding and the frequencies of vortex shedding vary with incidences and Mach number. At the same Mach number, the frequency of vortex shedding will decrease as the incidence increases. Yet, the frequency will increase as the Mach number increases at the same incidence. In the same computation case, the frequency of vortex shedding will vary along the span of blade. The frequency is smaller at the middle of the span than that at the hub.

关键词： axial flow compressor cascade unsteady flow separated flow frequency of vortex shedding.

Ballistic Penetration of Dyneema Fiber Laminate

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Journal of Materials Science & Technology 1998年第3期14卷 265-268页

作者： Zhang, Zuoguang Shen, Shiguang Song, Huancheng Zhang, Daxing Beijing univ aeronaut & astronaut Dept Mat Sci & Engn Beijing 100083 Peoples R China

UHMWPE fiber (Dyneema) reinforced composites are an important class of materials for armors. These materials provide superior ballistic performance to the armor, such as the military armor systems requiring a reduction in back-armor effects or a substrate for hardened facings of steel or ceramic. The reported work characterized the ballistic impact and mechanical performance of Dyneema fiber in composite laminates. The capability of the laminate to absorb ballistic impact energy was influenced by the impact velocity and the laminate areal density. Two kinds of penetration were compared and a two-step model for the penetration was proposed. (Edited author abstract) 3 Refs.

关键词： Fiber reinforced materials

Annealing Effect on Mechanical Properties of Ti_(51)Ni_(13)Pd_(36)High Temperature Memory Alloy

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Journal of Materials Science & Technology 2000年第5期16卷 531-533页

作者： Xu, HB Hu, SQ Jiang, CB Gong, SK Beijing univ aeronaut & astronaut Dept Mat Sci & Engn Beijing 100083 Peoples R China

The high temperature shape memory alloy Ti51Ni13Pd36 was subjected to a cold working and annealing treatment to improve its mechanical properties and the shape memory effect. It was found that recovery of the cold worked alloys started at near 673 K and the recrystallization temperature was at about 748 K. The grain size decreased with the increase of annealing temperature below 923 K and then increased when above 923 K. The smallest average grain size of about 3.5μm, which is approximately 10 times smaller than the hot rolled one, permitted the best combination of the mechanical properties in the alloy annealed at 923 K for 1h. The cold rolling raised the peak temperature of reverse transformation. This temperature dropped very sharply when the specimen was annealed at temperatures higher than 673 K.

关键词： Alloys