Yi K.,École Centrale Lyon |
Collet M.,École Centrale Lyon |
Ichchou M.,École Centrale Lyon |
Li L.,Beihang University |
Li L.,Co Innovation Center for Advanced Aerospace Engine
Smart Materials and Structures | Year: 2016
In this paper, we designed and analyzed a piezo-lens to focus flexural waves in thin plates. The piezo-lens is comprised of a host plate and piezoelectric arrays bonded on the surfaces of the plate. The piezoelectric patches are shunted with negative capacitance circuits. The effective refractive indexes inside the piezo-lens are designed to fit a hyperbolic secant distribution by tuning the negative capacitance values. A homogenized model of a piezo-mechanical system is adopted in the designing process of the piezo-lens. The wave focusing effect is studied by the finite element method. Numerical results show that the piezo-lens can focus flexural waves by bending their trajectories, and is effective in a large frequency band. The piezo-lens has the ability to focus flexural waves at different locations by tuning the shunting negative capacitance values. The piezo-lens is shown to be effective for flexural waves generated by different types of sources. © 2016 IOP Publishing Ltd.
Sun D.,Beihang University |
Sun D.,Co Innovation Center for Advanced Aerospace Engine |
Liu X.,Engine Certification Center |
Sun X.,Beihang University |
Sun X.,Co Innovation Center for Advanced Aerospace Engine
Journal of Fluids Engineering, Transactions of the ASME | Year: 2015
It is known that a kind of stall precursor-suppressed (SPS) casing treatment can be used to enhance compressor stall margin (SM) without recognizable efficiency loss. The further requirement in this regard is to develop an effective way to determine the variation range of the SM improvement during the design of such SPS casing treatment. In this investigation, based on the extrapolation hypothesis and the existing work, an extended stall inception model for quantitative evaluation of the SM enhancement is presented for both subsonic and transonic compressors with the SPS casing treatment. The capability of the extended model to quantitatively evaluate the SM enhancement with the SPS casing treatment is validated against the experimental data. The quantitative evaluation results show that the SPS casing treatments with different geometric parameters can improve the SM by a diverse percentage. In particular, for the facilities used in the present investigation, the experiments show that the SPS casing treatments can cause relevant increases of the SM. The change trend of the SM enhancement with various design parameters of the SPS casing treatment is in line with the corresponding theoretical results. Copyright © 2015 by ASME.
Yu J.-H.,Beihang University |
Chen Z.-T.,Beihang University |
Chen Z.-T.,Co Innovation Center for Advanced Aerospace Engine |
Jiang Z.-P.,Beihang University
International Journal of Advanced Manufacturing Technology | Year: 2016
Blades are affected by clamping, cutting forces, and residual stress, thus resulting in warping and distortion because of the thin wall and free surfaces. In this paper, a new process for the control of machining distortion is proposed to eliminate surface errors by using an adaptive dual-arm fixture. First, some causes of distortion by different machining methods are discussed. Second, an adaptive mechanism with eight degrees of freedom is designed to allow the blade to be clamped under an unstressed state and to enable the release of stress at any time. Thereafter, a dual-sphere fixture is designed on the basis of the adaptive mechanism. Finally, by adopting this process based on the adaptive dual-arm fixture, machining distortion is reduced after releasing stress several times. Experimental results show that the process can eliminate 50 % of surface errors in machining. Therefore, a test blade machined by the proposed process will exhibit improved precision. © 2016 Springer-Verlag London
Yu J.,Beihang University |
Yu J.,Co Innovation Center for Advanced Aerospace Engine |
Chen Z.,Beihang University
Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica | Year: 2016
Blade is easily affected by clamping, cutting force and residual stress which result in warp and torsion due to thin-walled and free surface of blade. In this paper, a new method for the control of machining distortion that eliminates surface errors by using an adaptive dual-arm fixture is presented. Firstly, the sources of distortion in different machining methods are discussed. Secondly, after the detailed analysis of unstressed fixing and stress releasing, the engineering design and mechanism analysis of the adaptive mechanism are shown. Finally, a control process of machining distortion is obtained based on the adaptive dual-arm fixture. Machining distortion can be eliminated without multiple repairing datum and changing machine. The experimental results show that the adaptive dual-arm fixture can effectively eliminate surface errors by 50% in machining, and the precision of test blade machined in this way is improved obviously. © 2016, Press of Chinese Journal of Aeronautics. All right reserved.
Jin Y.,Nanjing University of Aeronautics and Astronautics |
Jin Y.,Co Innovation Center for Advanced Aerospace Engine |
He X.,Nanjing University of Aeronautics and Astronautics |
He X.,Co Innovation Center for Advanced Aerospace Engine |
And 4 more authors.
Applied Thermal Engineering | Year: 2014
Flow fields of combustors have been commonly used to help understand combustion characteristics. In this paper, numerical simulations with validated methodology are employed to provide insight of the flow structures of a laboratory-scale trapped vortex combustor (TVC). Turbulence model determination and numerical method validation are accomplished with the help of experimental data from particle image velocimetry (PIV) measurements. A comparison of numerical and experimental results suggests that the standard k-ε turbulence model is able to provide a satisfactory prediction of the flow structures. Both of the two typical cavity flow patterns mentioned are observed: in a plane between two radial struts, the cavity flow features the dual-vortex pattern, however, in a plane along a radial strut, the cavity flow is dominated by the single-vortex pattern. This difference in flow patterns of different planes indicates the difference in cavity stream-mainstream mixing mechanism, which further, is believed to lead to enhanced mixing in spanwise direction. © 2014 Elsevier Ltd. All rights reserved.
Jin Y.,Nanjing University of Aeronautics and Astronautics |
Jin Y.,Co Innovation Center for Advanced Aerospace engine |
He X.,Nanjing University of Aeronautics and Astronautics |
He X.,Co Innovation Center for Advanced Aerospace engine |
And 5 more authors.
Aerospace Science and Technology | Year: 2014
Previous works have put forward the key role of radial strut in a trapped vortex combustor (TVC), however, few researches focusing on radial strut can be found in the existing literature so far. The present study is carried out to investigate the effect of the cavity-injector/radial-strut relative position on the performance of a trapped vortex combustor. This effect is directly explored by TVC combustion experiments that are run at atmospheric pressure using RP-3 liquid aircraft fuel. The specific positions include: the inline arrangement, the intermediate arrangement and the staggered arrangement. The staggered arrangement shows remarkable advantages in terms of ignition, lean blow out (LBO) and combustor temperature rise, whereas the inline arrangement performs rather poorly. Numerical simulations with validated methodology of non-reacting flows are then conducted for the purpose to explain the experimental results. The good performance of the staggered arrangement is mainly attributed to the counter-rotating streamwise vortex pair, the high turbulent kinetic energy and turbulent dissipation rate. © 2014 Elsevier Masson SAS.
Lu Z.L.,Xi'an Jiaotong University |
Lu Z.L.,Co Innovation Center for Advanced Aerospace Engine |
Fan Y.X.,Xi'an Jiaotong University |
Miao K.,Xi'an Jiaotong University |
And 4 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2014
To satisfy the requirements of mechanical performances of integral Al 2O3-matrix ceramic mould for fabricating hollow turbine blades, Al2O3 or ZrO2 fibres were added to the slurry in gelcasting. The microstructures of Al2O3-matrix ceramic mould were tested by scanning electron microscope and micron X-ray imaging system besides their bending strengths at different temperatures. The result showed that when Al2O3 fibre or ZrO2 fibre were added, the room-temperature bending strength of the ceramic mould was remarkably improved after pre-sintering at 1,250 °C. The medium-temperature bending strength was about between 0.5 and 2 MPa from 400 to 600 °C and reached the minimum at 500 °C. At 1,300 °C, the high-temperature bending strengths decreased gradually with an increase of Al2O3 fibre content and increased with an increase of ZrO2 fibre content. The specimens expanded first in pre-sintering and then shrunk in final sintering, respectively. According to the test results, we used ZrO2 as the additive with 10 wt% content, and the overall performances of Al 2O3-matrix ceramic mould were the best. Finally, hollow turbine blades were successfully fabricated. © 2014 Springer-Verlag London.
Jiao S.,Airforce Engineering University |
Cheng L.,Co Innovation Center for Advanced Aerospace Engine |
Li Q.,Xidian University |
Li X.,Airforce Engineering University
Key Engineering Materials | Year: 2016
The cyclic load number of aero-engine blade during its service life is very likely beyond 107, which is regarded as the conventional fatigue limit. Moreover, surface strengthening is very often used in the manufacturing process of blade. The conventional testing method in the VHCF regime cannot exactly reflect the stress state of the blade, including the mechanism of crack initiation. To study the fatigue behavior and effects of laser shock peening, a kind of bending fatigue subcomponent specimen was designed and the laser shock peening model was established. Experiment about TC17 was accomplished by the Ulra-High Cycle bending fatigue system. It is found that the fatigue damage occurs beneath the surface and the S-N curve is continuously rather than multi-step declining in the VHCF regime. Process of surface strengthening has a significant effect on fatigue performance of TC17 titanium alloy. © (2016) Trans Tech Publications, Switzerland.
Gao X.,Northwestern Polytechnical University |
Chu W.-L.,Northwestern Polytechnical University |
Chu W.-L.,Co Innovation Center for Advanced Aerospace Engine
Hangkong Dongli Xuebao/Journal of Aerospace Power | Year: 2014
For the study object of a subsonic axial-flow compressor rotor of Northwestern Polytechnical University, a reliable numerical simulation method was presented, and then axisymmetric contouring optimization for the casing under the condition of peak efficiency was conducted with the module DESIGN/3D in software package NUMECA, and the optimal rotor was obtained finally. The optimal rotor pushed the tip clearance leakage vortex away from the suction side at the leading edge of the blade. Although this led to an increase of the magnitude of leakage vortex and flow loss at the first 30% axial chord, the magnitude of leakage vortex and flow loss were greatly reduced at the last 70% axial chord of the blade, thus reducing the total loss, and increasing the peak efficiency and absolute total pressure at the outlet. The efficiency of the optimal rotor increases about 0.36% under the peak efficiency condition, which increases more under large mass flow rate condition, but under the near stall condition, the optimal rotor forms low velocity zone earlier at the blade tip area, leading to an earlier stall and making the stability margin of the optimal rotor smaller.
Zhang C.,Nanjing University of Aeronautics and Astronautics |
Hu J.,Nanjing University of Aeronautics and Astronautics |
Hu J.,Co Innovation Center for Advanced Aerospace Engine |
Wang Z.,Nanjing University of Aeronautics and Astronautics
Journal of Engineering for Gas Turbines and Power | Year: 2014
To clearly clarify the effects of different upstream boundary layer thickness and tip clearance size to the detailed tip flow field and flow mechanism, numerical simulations are performed on a subsonic compressor rotor, which is used for low-speed model testing of a rear stage embedded in a modern high-pressure compressor. First, available experimental data are adopted to validate the numerical method. Second, comparisons are made for tip leakage vortex (TLV) structure, the interface of leakage flow/mainflow, endwall loss, isentropic efficiency and pressure-rise among different operating conditions. Then, effects of different clearance sizes and inflow boundary layer thicknesses are investigated. Finally, the self-induced unsteadiness at one near-stall (NS) operating condition is studied for different cases. Results show that the increment of tip clearance size has a deleterious effect on rotor efficiency and pressure-rise performance over the whole operating range, while thickening the inflow boundary layer is almost the same except that its pressure-rise performance will be increased at mass flow rate larger than design operating condition. Self-induced unsteadiness occurs at NS operating conditions, and its appearance largely depends on tip clearance size, while the effect of upstream boundary layer thickness is little. Copyright © 2014 by ASME.