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    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (7): 0-0.  
    Abstract3156)      PDF(pc) (20270KB)(116159)      
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    Research Progress on Mesh Deformation Method in Computational Aeroelasticity
    ZHANG Weiwei, GAO Chuanqiang, YE Zhengyin
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2014, 35 (2): 303-319.   DOI: 10.7527/S1000-6893.2013.0423
    Abstract3363)      PDF(pc) (12893KB)(87473)      

    Mesh deformation is a main method to implement the computational mesh deformation with a moving boundary in computational aeroelasticity. First, an investigation of the status of the current advances in the researches on mesh deformation is presented in this paper, and some common mesh deformation approaches in recent years are reviewed in detail, which are spring analogy method, elastic solid method, transfinite interpolation method, Delaunay graph method, radial basis function method and temperature analogy method. Besides, based on the established models, the existing methods can be classified into physical model method, mathematical interpolation method and hybrid approach. A brief introduction of each method is made on theoretical method and research advance. The main emphasis is on the difference among the three methods of advantages and disadvantages as well as properties including deformation capability, deformation quality and efficiency. As an important aspect in computational aeroelasticity, the calculation data transformation between flow field boundary and structure boundary is summarized as well. At last, the present problems of mesh deformation which are frequently encountered in computational aeroelasticity are discussed, and in order to meet the needs of projects, possible prospects in future mesh deformation investigations are also proposed.

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    Concept definition of new-generation multi-purpose manned spacecraft
    YANG Lei, ZHANG Bainan, GUO Bin, ZUO Guang, SHI Yong, HUANG Zhen
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (3): 703-713.   DOI: 10.7527/S1000-6893.2014.0355
    Abstract3503)      PDF(pc) (1609KB)(74358)      

    With the Shenzhou spacecraft entering into the stage of maturity, it is of necessity to launch the research and development of a new-generation multi-purpose manned spacecraft. In this paper, we firstly generalize the technological characteristics, the design concept and the status quo of the foreign new-generation manned spacecraft. Based on this, we summarize their technological trend, i.e., multi-task adaption, cost reduction, bluntbody aerodynamic configuration, high safety reliability and new lightweight materials. Then, we primarily analyze the task requirements of China's new-generation manned spacecraft, including low earth orbit flight mission, as well as manned flights to the Moon, the asteroid and the Mars. We basically set the parameters of the overall performance. Finally, we sort out the technological approaches of it and propose two design schemes, which could provide some reference for the research of China's new-generation manned spacecraft.

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    Moving targets TDOA/FDOA passive localization algorithm based on localization error refinement
    LIU Yang, YANG Le, GUO Fucheng, JIANG Wenli
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (5): 1617-1626.   DOI: 10.7527/S1000-6893.2015.0010
    Abstract3529)      PDF(pc) (2558KB)(73301)      

    For the two-stage weighted least squares (TSWLS) technique of passive source localization using time difference of arrival (TDOA) and frequency difference of arrival (FDOA) measurements, which has the problem that the root mean square error (RMSE) and localization bias is large as the measurement noise increases. Based on analyzing the factor influencing the performances of the TSWLS firstly and then improves the TSWLS via Taylor-series (TS) expansion technique. The first stage of the new algorithm is the same as the one of TSWLS. At the second stage of the new algorithm, the localization error of the first stage is identified through utilizing the first-order Taylor-series expansion. Through updating the first-stage localization error, the final localization output is obtained. Theoretical performance analysis shows that the proposed estimator can attain the Cramer-Rao lower bound (CRLB) accuracy. Computer simulations are used to contrast the new technique with the TSWLS algorithm, the iterative maximum likelihood method based on TS and the constrained total least squares (CTLS) algorithm in terms of their localization RMSE and the localization bias. The new algorithm whose complexity is almost the same as TSWLS, the RMSE and localization bias are lower than TSWLS, TS and CTLS algorithm.

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    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (6): 0-0.  
    Abstract1091)      PDF(pc) (37750KB)(69490)      
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    LADRC-based trajectory tracking for unmanned helicopter
    WU Chao, WANG Haowen, ZHANG Yuwen, TAN Jianfeng, NI Xianping
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (2): 473-483.   DOI: 10.7527/S1000-6893.2014.0270
    Abstract3340)      PDF(pc) (5579KB)(55255)      

    Trajectory tracking control system is used for decoupling the control unmanned helicopter, which is a nonlinear system with multi-input/multi-output and strong coupling effects. In order to avoid the dependence on accuracy of unmanned helicopter physical parameters measurement and identification and to reduce external disturbance impact, a multi-loop controller based on linear active disturbance rejection control (LADRC) is proposed. At first, the flight dynamics model is built for unmanned helicopter X-Cell. The atmospheric disturbance model, which contains wind shear, turbulence and gust model, is also set up for accurate simulation of real flight environment. Secondly, X-Cell is trimmed for verifying the accuracy of dynamic model and trim algorithm. A set of calculation values is selected as the initial state and input of the subsequent simulation. Then attitude, velocity and position control loop are built based on the first-order and second-order LADRC controllers which are selected according to system order. Combined with the time-scale separation principle, the whole trajectory control system is constructed from inner loop to outer loop. After that, the stability of the system is analyzed. The characteristic roots show that the whole system becomes stable with the trajectory controller. Finally, flight simulation experiments under various disturbance conditions are performed. The results show that the established control system can achieve a good climbing figure-eight trajectory tracking. Compared with controller based on proportion integration differentiation(PID), the controller based on LADRC has better robustness and capability of anti-disturbance.

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    Reliability-based Multidisciplinary Design Optimization Integrating BLISCO and iPMA
    LIU Chengwu, JIN Xiaoxiong, LIU Yunping, LIU Jihong
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2014, 35 (11): 3054-3063.   DOI: 10.7527/S1000-6893.2014.0047
    Abstract2923)      PDF(pc) (2453KB)(51723)      

    To solve the inefficient problem of reliability-based multidisciplinary design optimization (RBMDO), which is caused by the nested optimization process and repeated iterations of multidisciplinary analysis and reliability analysis, a new method integrating Bi-level integrated system collaborative optimization (BLISCO) and improved performance measure approach (iPMA) is proposed. Firstly, with the sequential idea, the whole process is decoupled and the repeatedly reliability analysis of overall reliability model is avoided. Then, an efficient and suitable BLISCO strategy for dealing with the multidisciplinary design optimization (MDO) of complex engineering system is adopted, which abandons the consistency constraints of collaborative optimization as well as the complex analysis and approximate modeling problems of Bi-level integration system synthesis. Thirdly, the performance measure approach (PMA) is improved by updating angle strategy to evaluate the reliability, which can reduce a great number of multidisciplinary reliability analysis. Finally, a shock absorber design example of landing gear has been implemented to verify the efficiency of the proposed method. The results show that the efficiency of the proposed method has been improved by 30.93% and 19.97% respectively compared to the other two methods. Therefore, it is valuable in engineering design and optimization.

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    Effect of modal selection on static aeroelastic analysis
    DU Ziliang, WAN Zhiqiang, YANG Chao
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (4): 1128-1134.   DOI: 10.7527/S1000-6893.2014.0247
    Abstract2558)      PDF(pc) (4636KB)(50150)      

    The flexibility method and modal approach are usually used in structural analysis in the static aeroelastic research. Compared to the flexibility method which is mature but brings higher computational cost for the solution,the modal approach has the advantage of significant reduction in the dimension of the problem,high efficiency and convenient for verification. However, there are no principles for the selection of modes and one must have enough engineering experience to fully utilize the modal approach in practice. To provide modal approach with its own quantitative criteria in practice, this paper first proposes the idea of modal influence coefficient to evaluate the effect of modal selection on modal approach of aeroelastic analysis. In order to validate the rationality and validity of the modal influence coefficient, the paper carrys out control efficiency and aeroelastic correction analysis for a typical aircraft. The results show that the modal influence coefficient can accurately evaluate the effect of modal selection on static aeroelastic analysis, thus providing some helpful reference in practice.

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    Influence of fiber surface state on microstructure and phase composition of C/C-SiC composites
    DAI Jixiang, SHA Jianjun, WANG Shouhao, WANG Yongchang
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (5): 1704-1712.   DOI: 10.7527/S1000-6893.2014.0154
    Abstract2890)      PDF(pc) (4727KB)(44954)      

    In order to investigate the influence of fiber surface state on the microstructure and phase composition of C/C-SiC composites, the surface composition of carbon fibers is modified by heat treatment, and then the fibers with different surface compositions are used to fabricate the C/C-SiC composites via liquid silicon infiltration technique. The surface composition of carbon fibers is measured by XPS (X-ray photoelectron spectroscopy). Results reveal that the oxygen content on the surface of carbon fibers decreases with increasing the treatment temperature. The low oxygen content led to small numbers of oxygen-containing functional groups, resulting in small pore size and a high porosity in C/C perform. After infiltrating the liquid silicon into C/C preform, the morphologies of C/C-SiC composites are observed by scanning electron microscopy(SEM). It is found that the microstructure and phase composition of C/C-SiC composites are quite dependent on the surface composition of carbon fibers. With decreasing the oxygen content on the carbon fiber surface, the SiC content in matrix increased, but the residual Si is reduced. Particularly, in the case of fibers with low oxygen content on the surface, there is almost no residual Si in matrix, and the composites presented a more homogeneous distribution of SiC matrix. Based on the results mentioned above, it can be seen that the microstructure and phase composition of C/C-SiC composites are controlled by the size and distribution of pores, which is closely associated with the surface state of carbon fibers. For the C/C preform with large pore size, during the liquid silicon infiltration, the formation of SiC is dominated by the solution-precipitation reaction and the interface-limited diffusion reaction mechanisms. In the case of C/C preform with small pore size, the formation of SiC is mainly controlled by solution-precipitation reaction mechanism.

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    Investigation of sound generation by non-synchronously vibrating rotor blades
    ZHOU Di, WANG Xiaoyu, CHEN Jun, HONG Zhiliang, SUN Xiaofeng
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (3): 737-748.   DOI: 10.7527/S1000-6893.2015.0029
    Abstract1417)      PDF(pc) (1578KB)(39282)      

    The blade fatigue failure is a common aeroelastic problem of axial compressor. The phenomenon accompanied with blade vibration is abnormal acoustic field generation in compressor duct. The frequency of sound field generated by non-synchronously vibrating rotor blades is unequal not only to the compressor rotational frequency, but also to the blade passing frequency that is identical with sound generated by stator and rotor interaction. Meanwhile the frequency cannot be explained by typical Doppler shift phenomenon. In this paper, a theoretical model based on the three-dimensional lifting surface theory has been built to demonstrate the frequency and circumferential modal characteristics of the sound generated by rotor blades vibration. The developed model illuminates the fact that the sound frequency and circumferential mode depend a lot on the inter-blade phase angle. The experiment results verify the relationship between sound generation and blades vibration given by the model.

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    Effects of Titanium Surface Anodization on Adhesive Bonding Properties of TA2/polyetheretherketone(PEEK)
    XU Fei, PAN Lei, BAI Yunrui, CAO Jiameng, TAO Jie, TAO Haijun, CAI Lei
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2014, 35 (6): 1724-1732.   DOI: 10.7527/S1000-6893.2013.0447
    Abstract2326)      PDF(pc) (3362KB)(37367)      

    Surface treatment on titanium sheets by NaTESi anodization at constant voltage is conducted to improve the bonding properties of TA2/polyetheretherketone (PEEK) in TA2/Cf/PEEK laminates. The effects of technical parameters (such as voltage, time and temperature) on the single lap joint shear strength and the surface roughness of TiO2 film are investigated by an orthogonal test. It demonstrates that the most important factor affecting the bonding properties is time. Longer anodization times resuted in lower surface roughness, which contributed to inferior bonding properties. Properties of the TA2 laminate are investigated by XRD and SEM, and the results show that the optimized process which is favorable for the increase of the bonding strength is as follows: anodizing voltage 10 V, anodizing temperature 35℃ and anodizing time 10 min. The surface roughness treated by this method is 1.34 μm and the nano-particles morphology appeares, which the size of the particles is about 100-200 nm. The single lap joint shear strength with these parameters could reach 19 MPa. The resistance to delamination between the titanium sheet and PEEK in this optimized process is measured in a double cantilever beam test. The average energy release rate of the TA2/PEEK interface which was prepared by the method of NaTESi anodization is 188.1 J/m2, which showes an increase of 103.1% compared with the untreated ones. The results indicate that the anodizing process markedly enhance the delamination resistance of TA2/PEEK bonding interface.

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    Airfoil optimization based on improved CST parametric method and transition model
    WANG Xun, CAI Jinsheng, QU Kun, LIU Chuanzhen
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (2): 449-461.   DOI: 10.7527/S1000-6893.2014.0059
    Abstract2591)      PDF(pc) (4418KB)(30220)      

    In this paper, B-spline basis function is implemented in class and shape transformation (CST) parameterization method in place of the traditional Bezier polynomials to enhance the local ability of control and accuracy to represent an airfoil shape. To guarantee the requirements on geometric smoothing performance and proper orthogonal decomposition (POD) reconstruction accuracy in airfoil design optimization process, the local fairing method for multi-resolution airfoil is proposed based on the wavelet decomposition technique, expanding the design space. A surrogate model based on POD method and γ-Reθt transition predicting model is adopted to achieve fast and accurate prediction of aerodynamic forces and transition. The computed results of flow around airfoils show that the combined surrogate model is an effective method in design optimization of natural laminar airfoil. A complete aerodynamic design optimization system for natural laminar airfoil is constructed by integrating genetic algorithm, the improved CST parameterization method with wavelet decomposition fairing, POD surrogate model and γ-Reθt transition model. The system is used for the design optimization of low-speed and transonic airfoils, achieving an increase in lift-drag ratio of 47.42% and 45.85%, respectively, which validates the efficiency of the design optimization system proposed in this paper.

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    A Feature Point Extraction Method for Large Size Aerial Images
    SHI Xiangbin, ZHANG Jinsong, CHEN Runfeng, LIU Jinli
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2014, 35 (1): 240-248.   DOI: 10.7527/S1000-6893.2013.0326
    Abstract3318)      PDF(pc) (3748KB)(24824)      

    The existing feature point extraction methods usually cost a lot of CPU time when they are applied to large size aerial images. For the purpose of fast extraction of feature points in these large size aerial images, a novel method is developed. Usually these aerial images have not only large sizes but also wide ranges of shooting. They usually have different feature point performances on different scales and the distributions of spectra are uniform in the frequency domain. In this paper, the scales of the feature points are kept by employing the Laplacian pyramid, and a specified non-uniform N-dimensional directional filter bank is applied to decompose the pyramid images. The scales and the directions of the images are extracted. Then the local extreme points are extracted as a candidate feature points set. Finally, the candidate feature points in different directions are merged by a specified merge-strategy. Thus, we obtain the final feature points set and the directions of the feature point described by the direction filter bank. Experimental results are presented that demonstrate the proposed method is efficient for large size aerial images while meeting the match rate and precision rate requirements.

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    Investigation of Airflow Allocation Inside High Pressure Turbine Rotor Blade
    ZHU Xingdan, TAN Xiaoming, GUO Wen, ZHANG Jingzhou, WANG Yongming
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2014, 35 (12): 3273-3782.   DOI: 10.7527/S1000-6893.2014.0193
    Abstract832)      PDF(pc) (13136KB)(23773)      

    Conjugate heat transfer simulation is used to conduct investigations aiming at obtaining the cooling performance of the internal cooling structures of a certain turbine rotor blade in this paper. Effects of three different airflow allocation methods on the cooling effect of the blade are analyzed under the condition of the same total airflow. Subsequently, the cooling structure with the best cooling performance is chosen to discuss the influence of rotational speed on total inlet pressure and overall cooling effectiveness. The results show that Model B produces more reasonable airflow allocation, obtaining more uniform temperature distribution and higher overall cooling effectiveness. The cooling airflow deflects due to the existence of Coriolis force and centrifugal buoyancy force. The stagnation line located at the blade leading edge is forced to shift from pressure side to suction side with the increase of rotational speed and the film discharges are also changed with the rotational speed. The increasing rotational speed leads to an improvement on pressure surface cooling effectiveness and inversely a decrement on suction surface cooling effectiveness.

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    Progress in airframe-propulsion integration technology of air-breathing hypersonic vehicle
    WU Yingchuan, HE Yuanyuan, HE Wei, LE Jialing
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (1): 245-260.   DOI: 10.7527/S1000-6893.2014.0238
    Abstract2820)      PDF(pc) (29626KB)(23727)      

    Air-breathing hypersonic vehicle is highly integrated making its design challenging. All vehicle parts and functions interact including aerodynamics, propulsion, control, structure, tank and thermal protection, especially for airframe and scramjet engine coupling. The lower wall of the aircraft forebody and afterbody is either compression part of the engine inlet or expansion part of the engine nozzle and it produces lift and pitching moment as well as thrust. The strong coupling of the airframe and engine has direct influence to the thrust, lift, drag, pitching moment, aerodynamic heating, airframe cooling, stability and control characteristics of the vehicle. The research developments of airframe-propulsion integration technology are introduced and the related works of China Aerodynamics Research & Development Center (CARDC) are emphasized. These works included osculating curved cone waverider inlet design, double shockwave axissymetric flow field-based inward turning inlet design, airframe-propulsion integrated vehicle tests in pulsed combustion heated hypersonic high-temperature wind tunnels and hypersonic large-scale parallel numerical simulation platform (AHL3D). The related fundamental researches of hypersonic shock-boundary layer interaction, compressible turbulent transition of flow separation mechanism and its control, scramjet combustion study on flow mechanism and other related basic issues are introduced. The urgent need of efficient high-precision calculation method is emphasized.

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    Axial Transonic Compressor Flow Instability Prediction Based on Eigenvalue Theory
    LIU Xiaohua, ZHOU Yanpei, SUN Dakun, MA Yunfei, SUN Xiaofeng
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2014, 35 (11): 2979-2991.   DOI: 10.7527/S1000-6893.2013.0499
    Abstract1881)      PDF(pc) (2559KB)(23162)      

    Flow instability is a great challenge in turbomachinery, and rotating stall is one major type of flow instability in compression system of aero-engine. In the present paper a rotating stall inception model based on a general eigenvalue theory of flow stability is developed with an emphasis on flow instability onset in axial transonic compressors. After solving the established eigenvalue equation using the spectral method and the singular value decomposition (SVD) method, the onset point of flow instability is determined by the imaginary part of the resultant eigenvalue. The significant effect of flow compressibility on the stall onset point calculation for a transonic rotor is studied by comparing the prediction results for a high speed single rotor at both high and low rotational speeds. The capacity of the present model to predict the stall inception point is assessed against the experimental data of a transonic single stage compressor. It is verified that this model is capable of predicting the mass flow at the stall onset point of a multi-stage transonic compressor flow with reasonable accuracy without numerous empirical data, and it is sustainable in terms of computation cost for industrial application.

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    AN EXPLICIT EXPRESSION OF THE TURBULENT FRICTIONAL DRAG COEFFICIENT FOR A FLAT PLATE
    Shi Changchun
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    1988, 9 (6): 299-302.  
    Abstract3834)      PDF(pc) (232KB)(23032)      
    This paper presents some analytic expressions associated with those well-known skin-friction formulas for turbulent shear flows. Two methods were developed for this aim. The first one is an approximated analytic solution for the same super-algebraic equation; And the second one is a method of iteration and its convergence has been proven. The skin-friction formula of D.B.Spalding has also been improved in the present work.
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    Research of Visual Interaction for Virtual Reality Flight Training
    ZHOU Lai, ZHENG Danli, GU Hongbin, WANG Debao
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2013, 34 (10): 2391-2401.   DOI: 10.7527/S1000-6893.2013.0290
    Abstract1954)      PDF(pc) (8203KB)(22807)      

    Appearance-based hand pose estimation which relies on computer vision techniques is adopted to realize natural interaction in a semi-virtual reality cockpit. To cope with the low efficiency and high memory consumption in large capacity and high-dimension feature indexing, an improved locality sensitive Hashing (LSH) method is proposed in this paper which combines the multi-probe principle with the nearest-neighbor table. Moreover, a forecast model which predicts indexing performance and a parameter optimization method are used to achieve better indexing performance. Experimental results show that the forecast model is appropriate for practical indexing performances and the time consumption is reduced by 41.9% at the cost of a slight recall rate drop. In summary, the application of the improved LSH to hand pose estimations able to upgrade virtual hand visualization and hand posture reconstruction in a semi-virtual reality cockpit.

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    Study of Heat Transfer of Cryogenic Methane Under Supercritical Pressure with Consideration of Thermal Conduction in Engine Cooling Channel Walls
    CHEN Zunjing, WANG Leilei, MENG Hua
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2013, 34 (1): 8-18.   DOI: 10.7527/S1000-6893.2013.0002
    Abstract3258)      PDF(pc) (7541KB)(22252)      

    Numerical simulation study is conducted of the heat transfer of cryogenic methane flowing inside a rectangular engine cooling channel under supercritical pressure with consideration of the coupled thermal conduction in the solid channel region. The effects of wall heat fluxes and cooling channel geometries on the fluid flow and heat transfer processes under supercritical pressure are carefully examined. Variations of the fluid velocity, channel wall temperature, wall heat flux, and Nusselt number are obtained and discussed. Results indicate that with consideration of the conjugate heat transfer in both the solid and fluid regions, a fraction of the heat flux imposed on the top channel surface is transferred into the cryogenic methane through the side walls. As the imposed wall heat flux increases, more heat can be thermally conducted into the side channel walls. Decreasing the cooling channel height/width aspect ratio leads to enhanced heat transfer, but the pressure loss also increases significantly. Therefore, the combined effects of the channel aspect ratio on both heat transfer and pressure loss has to be taken into consideration to obtain an optimum cooling channel design. The thermal performance parameter can be used as a reference in this regard. The modified Jackson & Hall coefficient is applicable to heat transfer prediction under supercritical pressure with acceptable accuracy under all tested conditions in this paper.

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    GENERATION OF 3 D MUTLI BLOCKED STRUCTURE BODY FITTED GRIDS OF A COMPLEX CONFIGURATION FLYING BODY
    Zhu Junzheng;Fan Xijun
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    1997, 18 (1): 62-66.  
    Abstract2147)      PDF(pc) (260KB)(21466)      

    A general generation method is presented for the 3 D multiply blocked structure grid of a complex configuration flying body.The structure grids can be generated by decomposing the domain into any number of contiguous blocks,and each physics region can be considered to have been transformed to a rectangular computational region on which the curvilinear coordinates are the independent variables.Thus the generated grid is not too skew or unregular.Effect of control functions on grid generation is discussed.The given examples showed that the method may deal with arbitrary complex 3 D domains with the multi blocked structure technique.

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    Numerical Study on Thermal Cracking of RP-3 Aviation Kerosene Under Supercritical Pressure
    ZHAO Guozhu, SONG Wenyan, ZHANG Ruoling
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2014, 35 (6): 1513-1521.   DOI: 10.7527/S1000-6893.2013.0547
    Abstract2119)      PDF(pc) (4449KB)(21244)      

    In order to understand the thermal cracking characteristic of hydrocarbon fuel under supercritical pressure in the regenerative cooling progress, a numerical study on the thermal cracking of RP-3 aviation kerosene under 5 MPa is conducted based on a four-species surrogate model of RP-3. A modified Kumar-Kunzru model consisting of 18 species and 24 reactions is used to simulate the cracking process. The effect of thermal cracking on the thermophysical properties and heat transfer of the fluid is investigated. The effect of secondary reactions on the thermal cracking of RP-3 aviation kerosene is also studied at high conversion of RP-3. Numerical results show that the conversion of RP-3 is higher than 20% with a relative proportion of aromatics of 12.1% once the fluid temperature reaches 890 K. The thermophysical properties of the fluid change obviously when the thermal cracking of RP-3 occurs. The wall temperature and fluid temperature decrease by 130 K and 129 K respectively at the tube outlet. Meanwhile, the Nusselt number increases by 16.5%, indicating that the heat transfer is enhanced. The secondary reactions affect the thermal cracking of RP-3 obviously at high conversion. It is found that the conversion of RP-3 with secondary reactions is 29.1% lower than that without secondary reactions. Meanwhile, the wall temperature and fluid temperature decrease by 34 K and 22 K respectively at the tube outlet.

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    Detached-eddy simulation based on unstructured and hybrid grid
    ZHANG Yang, ZHANG Laiping, HE Xin, DENG Xiaogang
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (9): 2900-2910.   DOI: 10.7527/S1000-6893.2014.0342
    Abstract792)      PDF(pc) (9485KB)(20867)      

    To improve the turbulence simulation ability of the second order finite-volume algorithm based on unstructured and hybrid grid, a hybrid second order scheme is established by modifying the dissipation term of the standard Roe flux-difference splitting scheme and the numerical dissipation of the scheme can be self-adapted according to the detached-eddy simulation (DES) flow field information. The credibility of the approach is supported by two typical numerical examples of its application: Re=3 900 circular cylinder and NACA 0021 airfoil at high angle of attack (60°), and the DES predictions are compared with experimental data and with other numerical solutions. The DES methods based on both the one equation Spalart-Allmaras turbulence model and the two equation k-ω shear stress transport (SST) model are used in the computation. The effects of numerical schemes and turbulence models are also discussed in the study, which shows that the scale of turbulence structure resolved by the hybrid scheme is smaller than that resolved by the standard Roe scheme and the corresponding flow field is better; meanwhile the DES methods used in this paper are little affected by their RANS-based models.

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    Experimental study on Rayleigh-Ludwieg instability of aircraft wake vortex
    BAO Feng, LIU Jinsheng, ZHU Rui, LIU Yue
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (7): 2166-2176.   DOI: 10.7527/S1000-6893.2015.0091
    Abstract920)      PDF(pc) (10413KB)(18628)      

    Based on the fact that the main wing and tail would produce counter-rotating vortices in the process of taking-off and landing, a set of double vortex generators are designed. Under two different experimental conditions, in terms of changing the position and initial intensity ratio of the double vortex, the wake vortex development of the test mode is acquired, including flow visualizations and particle image velocimetry (PIV) technology. Research reveals that the introduction of a weaker vortex, with a proper position and initial intensity ratio, would change the main vortex original trajectory and promotes its dissipation. However, it does not present an obvious linear relationship between them. The analysis results of vortex trajectory could be used in improving the efficiency of taking-off and landing in airports, the experiments also provide a reference for the overall design of aircrafts: when the requirement for flight mechanics design is satisfied, optimizing the overall aerodynamic layout will have a significant effect on alleviating the intensity of aircraft wake.

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    Hypersonic aeroheating prediction technique and its trend of development
    PENG Zhiyu, SHI Yilei, GONG Hongming, LI Zhonghua, LUO Yicheng
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (1): 325-345.   DOI: 10.7527/S1000-6893.2014.0242
    Abstract2851)      PDF(pc) (20003KB)(18424)      

    The hypersonic aeroheating prediction is a key technique for hypersonic vehicle. Development of hypersonic aeroheating prediction technique is analyzed and discussed. Firstly, a brief development history of hypersonic aeroheating prediction technique and experiment technology is reviewed. Based on that, according to the comparison with the calculation and wind tunnel experiment results for typical configuration, the aeroheating engineering computation calculation method and numerical simulation prediction technique are introduced with emphasis; meanwhile the performance of ground experiment equipment and the status quo of measurement technique are also generalized. Finally, the development trend of hypersonic aeroheating prediction technique is discussed; and the issue need to be studied and solved on aeroheating prediction technique are also raised.

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    Analysis of flow characteristics for hypersonic vehicle
    WU Ziniu, BAI Chenyuan, LI Juan, CHEN Zijun, JI Shixiang, WANG Dan, WANG Wenbin, XU Yizhe, YAO Yao
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (1): 58-85.   DOI: 10.7527/S1000-6893.2014.0228
    Abstract5480)      PDF(pc) (11227KB)(18345)      

    Modern hypersonic vehicles have local non-streamlined obstacles, operate at lower turbulent environment with high Mach number and lower Reynolds number and cruise in air subjected to shock and friction heating. Due to these factors, hypersonic flows are full of strong local flow structures such as strong shock waves and thick boundary layers, with severe interactions between them. Aerodynamic heating is strengthened locally by such interactions. A number of critical phenomena such as transition and pressure perturbations are quite sensitive and the competitive influences of wave and frictional drags make the lift to drag ratio have a barrier. All these are not simply dependent on the Mach number and Reynolds number, but also dependent on many dimensional parameters, so that modelling by ground facilities is difficult and a combined study of theory, numerical study and experimental measurement are necessary to solve an engineering problem. In this paper, we give an overview of the state-of-art knowledge of the most important and critical physics of hypersonic flow and discuss the methods to solve hypersonic flow problems in the most possible effective way.This review and discussion are hopefully useful for further fundamental studies and for providing a bridge between fundamental study and engineering applications.

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    Effect of Dryden atmospheric turbulence on minimum-energy trajectory of stratospheric airships
    ZHANG Liming, XING Jianjun, CHEN Ziang, WANG Yi, YU Yang
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2017, 38 (1): 120180-120180.   DOI: 10.7527/S1000-6893.2016.0157
    Abstract697)      PDF(pc) (5201KB)(18311)      

    This paper investigates the ascent optimal trajectory of stratospheric airship with constant wind and the effect of atmospheric turbulence on optimal trajectory. First, three-degree-of-freedom dynamics model of stratospheric airship was completed by forces analysis, considering the constant wind, earth rotation, mass rate and other factors, and then the variables were scaled to obtain a normalized system equation. Second, this problem of optimal trajectory was transformed into a problem of nonlinear programming by using the direct collocation method. Considering the minimum energy scenario, an appropriate solution for nonlinear programming problem was determined, and the feasible solution was obtained. Then the control history of solution was taken into the system equation to examine the feasibility and the acceleration components were analyzed. Finally, the Dryden atmospheric turbulence was introduced to the minimum energy scene, and then the data of computation and comparison analysis were obtained. By discussing the error between calculation and simulation, the relation of the error of final position and the mean of complex wind was found, and a strategy for resisting the interference of Dryden atmospheric turbulence for stratospheric airships was raised.

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    Analysis of Flight Delay Propagation Using Bayesian Networks
    Li Junsheng;Ding Jianli
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2008, 30 (6): 1598-1604.  
    Abstract3140)      PDF(pc) (844KB)(18198)      
    As there exists a link between the scheduled flights, each scheduled flight delay can affect the downstream airport and its scheduled flight.Therefore methods are needed to investigate and visualize the propagation of delays for flightconnection at hub airports. The Bayesian network (BN) is an effective propagation analysis method. In this article, a flight delay propagation model is developed based on the BNs by analysis of a certain hub airport flight delays which will affect associated airports and connecting flights. By utilizing some actual airline data, the article reports training of the model through the expectation maximization (EM) algorithm, and gives the test results, which clearly demonstrate the value of BN for analyzing the system-level effects arising from micro-level causes.
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    Gas kinetic scheme in hypersonic flow simulation
    XU Kun, CHEN Songze
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (1): 135-146.   DOI: 10.7527/S1000-6893.2014.0232
    Abstract2810)      PDF(pc) (3047KB)(17475)      

    For hypersonic flow simulation, a review of computation fluid dynamics (CFD) and a summary of gas kinetic scheme are presented in this paper. The mechanism underlying the construction of gas kinetic scheme is clarified by comparing it with the traditional CFD method. The importance of direct modeling and the implementation of the physical laws in a discretized space are emphasized. Through some classical hypersonic applications in recent years, such as the shock/shock interaction, shock wave/boundary layer interaction, and hypersonic boundary layer separation problems, the advantages of the methodology are also demonstrated. As a trend of CFD, the gas kinetic scheme includes more fundamental physical laws in its algorithm construction, and the multiple scale nature makes the kinetic scheme feasible for the hypersonic applications. The principle of direct modeling and the methodology of constructing numerical schemes from mesoscopic or microscopic flow dynamics would benefit the development of reliable flow solvers, especially for the high speed flow.

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    Asynchronous track-to-track association algorithm based on similarity degree of interval-real sequence
    YI Xiao, HAN Jianyue, ZHANG Huaiwei, GUAN Xin
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (4): 1212-1220.   DOI: 10.7527/S1000-6893.2014.0275
    Abstract1897)      PDF(pc) (5901KB)(17127)      

    Because local sensors in the distributed multi-target tracking system usually start working at different time and provide tracks at different rates with different communication delays, the local tracks from different sensors are usually asynchronous. The current solution is to synchronize the tracks before track association. But the estimation error spreads when synchronizing, which affects the performance of correlation. To solve the problem, an asynchronous track-to-track association method based on similarity degree of interval-real sequence is presented. Firstly, the track sequences are transformed to same-length sequences which contain interval data and real data by interval-real sequence transform (IRST). Then a new difference measurement for the sequences is defined, by which the correlation degree can be calculated and the track association conclusion be made. Simulation results show that the presented method can effectively solve the asynchronous track-to-track association problem, and its performance is seldom affected in the case of different communication delays and disorderly data.

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    Computational research on aerodynamic characteristics of helicopter main-rotor/tail-rotor/vertical-tail interaction
    YE Zhou, XU Guohua, SHI Yongjie
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (9): 2874-2883.   DOI: 10.7527/S1000-6893.2014.0314
    Abstract510)      PDF(pc) (5941KB)(16334)      

    A computational method based on computational fluid dynamics (CFD) technology is developed for helicopter main-rotor/tail-rotor/vertical-tail interaction analysis. In the present method, Navier-Stokes equations are utilized as the control equations. For the spatial and time discretization, the second-order upwind Roe scheme and implicit LU-SGS (Lower-Upper Symmetric Gauss-Seidel) scheme are used respectively, and the B-L (Baldwin-Lomax) model is used as the turbulence model. Moving embedded grid method is applied to exchanging the flowfield information among the grids of main-rotor, tail-rotor and vertical-tail. By the method developed, example calculations on the flowfield of well-known Helishape 7A rotors and Lynx tail rotors are performed, and the validity of the present method is demonstrated by comparing the calculated results with available experimental data. Then, numerical simulations for main-rotor/tail-rotor aerodynamic interference are made. Furthermore, taking vertical tail interaction into consideration, tail-rotor/vertical-tail and main-rotor/tail-rotor/vertical-tail interaction calculations are conducted to investigate the interaction mechanism between main rotor, tail rotor and vertical tail. It is shown that, for different vertical-tail/tail-rotor configurations, a larger blockage area always leads to a greater tail-rotor trust, but a smaller clean trust of vertical tail and tail rotor. In addition, the clean tail-rotor trusts of "push configuration" are always higher than those of the "pull configuration" for different blockage areas. It is also shown that, vertical tail has little influences on main-rotor/tail-rotor interaction in forward flight.

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    Effect of Mistuned Parameters on Mode Localization of T-tail Structure
    Yang Zhichun;Yang Fei
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2009, 30 (12): 2328-2334.  
    Abstract30175)      PDF(pc) (904KB)(565)      
    Mode localization is often an unexpected dynamic phenomenon in weakly-coupled symmetric structures, and it arises from small imperfections (less than 5%) which perturb the symmetry of a structure. Such imperfections typically result from random manufacturing or assembly imprecision. Mode localization prediction is an important issue in T-tail structure design because drastic localized vibration phenomena may occur during the ground vibration test of a T-tail aircraft. Mode localization is dependent not only on parameter mistuning, but also on coupling degree. In this article the definition of mode localization is improved according to the peak amplitude ratio. The coupling degree is defined according to the effect of the stiffness of the horizontal stabilizer and fin on the modal frequencies of the T-tail structure. The mode localization and frequency loci veering phenomena for a T-tail structure is then studied and the effects of mistuned mass, mistuned stiffness and the location of mistuning on the mode localization of the horizontal stabilizer are investigated. Numerical simulation results for a T-tail structure model indicate that mode localization is most likely to occur in a T-tail structure consisting of weakly coupled substructures—a horizontal stabilizer and a fin. Moreover, when mode localization occurs, the first two bending vibration modes in the T-tail structure are prone to localization, and only one of the two modal frequencies is changed by parameter mistuning to induce frequency loci veering. The simulation also demonstrates that if mass or stiffness mistuning occurs to a horizontal stabilizer, the amplitude of the bigger mass side or smaller stiffness side is greater than that of the peer side. The study suggests that mode localization design is easy to achieve in T-tail structures by introducing mass mistuning on the tip of the horizontal stabilizer or stiffness mistuning on the root of the horizontal stabilizer.
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    Real-time Parameters Estimation of Inertial Platform’s HealthCondition Based on Belief Rule Base
    Hu Changhua;Si Xiaosheng
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2010, 31 (7): 1454-1465.  
    Abstract13176)      PDF(pc) (2000KB)(890)      
    A real-time and accurate health condition prediction for an inertial platform is essential for cost-effective and timely maintenance planning and scheduling. Due to the fact that the true health condition of the inertial platform cannot be observed directly, it is assumed that the observations of characteristic parameters are available from monitoring, and the characteristic parameters correlate with health condition of the inertial platform. In this article, a health condition prediction system for the inertial platform is established based on belief rule base (BRB), where the characteristic parameters of the inertial platform are used as the inputs of BRB system and the health condition of platform as the output consequence. To overcome the drawbacks of current parameter optimization algorithms for BRB and satisfy real-time prediction, a parameter estimation algorithm is investigated for online updating BRB prediction system based on the expectation maximization (EM) algorithm. When the new input-output information of system operation is available, the model parameter can be updated online. Real-time health condition prediction for the inertial platform system is validated using the established model and the algorithm under investigation. The experimental results show that the proposed method can implement online parameter estimation of health condition prediction for the inertial platform effectively. In addition, compared with offline parameter optimization method, the proposed method can generate better results in terms of prediction accuracy and operating time, and thus has great potential in engineering practice.
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    Genetic collision avoidance planning algorithm for irregular shaped object with kinematics constraint
    ZHANG Zhi, LIN Shenglin, ZHU Qidan, WANG Kaiyu
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (4): 1348-1358.   DOI: 10.7527/S1000-6893.2014.0130
    Abstract12006)      PDF(pc) (7869KB)(402)      

    To deal with the path planning problems of irregularly shaped objects in complex environment, a genetic collision avoidance algorithm with kinematics constraint is developed. This algorithm is then applied to the path planning operations on carrier-based aircraft scheduling on carrier flight deck. Moreover, it can be extended to solve other path planning cases under such constraints. For the problems resulting from these objects, which are characterized by complex shape and the bending radius constraint while moving in complicated obstacle situations, the technique proposed is proved to be effective. Based on the traditional genetic path planning algorithm, a three-dimensional position and orientation coding method, a three-stage path decoding method and an approach specific to the collision detection and distance calculation of a track bounding box are presented. Also, a penalty term and a gene repairing strategy are brought into the genetic process to seek the optimum. Finally, simulated verifications are conducted using VC++ platform to obtain the optimal paths. The results show that the optimal collision avoidance paths in complex obstacle environment are achieved utilizing the proposed algorithm, with the pre-set bending radius constraints satisfied. It is indicated that the design yields effective solutions to the collision avoidance path planning problems correlated with this kind of objects.

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    Symmetry FrFT Used to Suppress the Fixed Background Clutter to Detect Moving Target in a SAR Image
    CHEN Guang-dong;ZHU Zhao-da;ZHU Dai-yin
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2005, 26 (6): 748-753.  
    Abstract9841)      PDF(pc) (784KB)(1048)      
    In single channel SAR, the echo from a slow moving target is confused with ground clutter in time、space and frequency domains. If the information about fixed clutter in SAR image can be used to suppress the background clutter, the detection of moving target will be easy. The fractional Fourier transform is a linear operator, and will not be influenced by cross terms. The FrFT is a way to concentrate the energy of the echo from a ground moving target. In two symmetry fractional Fourier domains with two inverse rotation angles of every SAR image tangential line, the static clutter’s spectrums are same, while the moving target’s are different. The absolute value subtracting of the two signals can be expected to have superior moving target detection performance. The experiment result proveds the validity of this method.
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    Application of Gauss-Hermite Filter in SINS Alignment
    XIE Yangguang, YI Guoxing, WANG Changhong, QU Yaobin
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2012, (3): 554-560.   DOI: CNKI:11-1929/V.20110726.1650.006
    Abstract9184)      PDF(pc) (1152KB)(556)      
    In this paper investigate the alignment problem of a stationary based strapdown inertial navigation system . In order to improve the aligning accuracy and shorten the aligning time, a Gauss-Hermite filter (GHF) is adopted in the alignment model based on large azimuth misalignment angles. The nonlinear Gauss integration of multi-variables to the mean and covariance computation in the GHF is addressed. Since large azimuth misalignment angles will introduce the nonlinearity in the alignment error equations, this paper employs linear state transformation approach to obtain the analytic solution of the linear state vector in the underlying equations. The integration of multi-variables is thus converted to the integration of a single-variable. Hence the so called "dimension problem" in the application of GHF to alignment is solved without loss of accuracy. The proposed method is applied to a SINS, and it shows that the aligning accuracy of path angle is improved by 16% and the aligning time is reduced by 75% compared with extended Kalman filter (EKF) and unscented Kalman filter (UKF).
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    Numerical Study on Turbulent Convective Heat Transfer with n-heptane Under Supercritical Pressures
    Hua Yixin;Wang Yazhou;Meng Hua
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2010, 31 (7): 1324-1330.  
    Abstract9094)      PDF(pc) (1517KB)(898)      
    This article establishes a general numerical scheme which incorporates the accurate transport and thermodynamic property calculations of a fluid under supercritical pressures based on a modified corresponding-state method and the fundamental thermodynamic relationships with the Soave-Redlich-Kwong (SRK) equation of state. A comprehensive numerical investigation of the turbulent convective heat transfer with n-heptane, a typical hydrocarbon fuel, under supercritical pressures is systematically conducted. This heat transfer phenomenon is closely related to engine cooling technique in rocket and hypersonic propulsion systems. The effect of the supercritical pressure on fluid flows and heat transfer phenomena is examined in detail. Variations of the Nusselt number are elucidated and compared with those obtained from the available empirical formulae. Numerical results indicate that under supercritical pressures, the Nusselt number decreases with decreasing pressure, and that turbulent heat transfer becomes weakened and slightly oscillated near the critical region.
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    Real-time residual life prediction based on semi-stochastic filter and expectation maximization algorithm
    FENG Lei, WANG Hongli, SI Xiaosheng, YANG Xiaojun, WANG Biaobiao
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (2): 555-563.   DOI: 10.7527/S1000-6893.2014.0257
    Abstract9076)      PDF(pc) (2024KB)(389)      

    The prediction of residual life (RL) is the key of the predictive maintenance for engineering equipment. Accurate and real-time prediction can provide more effective decision support to the subsequent maintenance schedule and avoid the failure effectively. In engineering practice, the performance index reflecting the degradation process of the equipment is generally not observed directly. To tackle the residual life problem under hidden degradation, a prediction method based on semi-stochastic and expectation maximization (EM) algorithm is proposed in this paper. First, the residual life is taken as the hidden state and the prediction model is constructed by building the stochastic relationship between the residual life and monitoring data. Secondly, based on the monitoring data up to the current time, a collaborative method by the extended Kalman filter (EKF) and expectation maximization algorithm is presented to achieve a real-time estimation and updating of the residual life distribution and unknown model parameters. Finally, the proposed method is validated by the application to the inertial measurement unit (IMU) and the results indicate that the method can improve the accuracy and reduce the uncertainty of the estimated residual life.

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    High-Precision Estimation of 2D Angle for Signals with UCAs
    TAO Jian-wu;SHI Yao-wu;CHANG Wen-xiu
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2006, 27 (4): 687-691.  
    Abstract8354)      PDF(pc) (383KB)(1042)      
    Based on uniform circular arrays (UCAs), a high-precision estimation of 2D direction angle for multiple sources is proposed. First, exploiting information of source in 2D space-time domain forms the space-time rotational matrix, so that the multiple sources are separated. Second, based on a direct array manifold in UCA, the azimuth and elevation are estimated by Least Squares (LS). Finally, the removal method of cyclic ambiguity is presented. Numerical results show that the advantages of estimator are high precision and robustness to amplitude and phase error of sensor gain.
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    Influencing factors of combustion characteristics of boron particle in forced convective flow
    FANG Chuanbo, XIA Zhixun, HU Jianxin, WANG Dequan
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (2): 492-500.   DOI: 10.7527/S1000-6893.2014.0115
    Abstract7762)      PDF(pc) (4169KB)(280)      

    The combustion characteristics of single boron particle in forced convective flow in ramjet engines are investigated systemically. A physical and mathematical model is proposed taking into consideration the gas flow around the particle, the gas diffusion and the surface finite reaction dynamics. The two-dimensional axi-symmetric Navier-Stokes equations with species reactions are solved using the finite volume technique. And the numerical simulation method is validated. Then influencing factors such as the free stream velocity, particle radius, the ambient oxygen mass fraction and the ambient pressure on the combustion characteristics of single boron particle are studied by numerical simulations. And the effect mechanism for each factor is analyzed in detail. The numerical prediction results show that in forced convective flow, both the mass rate and the mass flux of the buring boron particle increase with the increase in the free stream velocity, the particle radius, the ambient oxygen mass fraction and the ambient pressure. A comprehensive analysis of the results is conducted and it is found that the mass flux of the buring boron increases with the stream Reynolds number. Then the mass flux of the buring boron particle in the static atmosphere is modified based on abundant numerical results to describe the combustion characteristics of the boron particle in forced convective flow.

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    EROSION WEAR BEHAVIOUR AND MODEL OF ABRADABLE SEAL COATING
    Yi Maozhong;Huang Baiyun;He Jiawen;Zhou Huijiu
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    1998, 19 (5): 546-552.  
    Abstract7477)      PDF(pc) (847KB)(703)      

    The erosion wear resistance is one of the most important properties of abradable seal coating. The erosion wear behaviour and mechanism of several kinds of middle temperature abradable seal coatings were investigated by a CMS 100 self made vacuum sand erosion machine. The results show that the relationship between the erosion weight loss and the erosion time is linear, the coatings hold a maximum erosion rate at 60° impact angle, and the relation between the erosion rate and the impact speed is an exponential function. The speed exponent increases with the increase of the impact angle. At 90° impact, the abrasive particles impinging on the coating surface produce indents and extrude lips, then the lips are work hardened and fall off; and flattened metal phase grains are impinged repeatedly, loosen and exfoliate. At 30° impact, the micro cutting, plowing and tunneling via pores and non metal phase are involved. The model of the erosion mechanism is advanced on the basis of the above mentioned erosion behaviour.

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    Laminar Flow Control Technology and Application
    ZHU Ziqiang, WU Zongcheng, DING Juchun
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2011, 32 (5): 765-784.  
    Abstract7124)      PDF(pc) (3625KB)(4782)      
    Friction drag is the major part of the total drag of a transport, so reducing it is essential for improving the performance and reducing the cost of a transport. Since laminar friction drag is much less than the turbulent one, one of the important measures for reducing it is to increase the laminar flow extent, and if possible, to realize a fully laminar flow. For that, three types of laminar flow control technology, i.e., natural laminar flow, fully laminar flow and hybrid laminar flow controls, are formed. In the present paper, drag reducing analysis, the concepts, methods, potential benefits and design methods of laminar flow control technology, and operational maintenance of a laminar flow aircraft (including protection of insect contamination and ice accumulation) are systematically described; Summary of researches of laminar flow control technology during 1930-2000 is briefly introduced and the progress in this field is shown by using examples of X-21A slotted suction flight tests, simulated airlines flight tests of Jetstar HLFC leading edge systems and Boeing 757 HLFC flight tests, and future research is also pointed out.
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    Influence of Opposing Jet on Flow Field and Aerodynamic Heating at Nose of a Reentry Vehicle
    Rong Yisheng;Liu Weiqiang
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2010, 31 (8): 1552-1557.  
    Abstract6777)      PDF(pc) (26444KB)(740)      
    A CFD study on the reduction of aerodynamic heating on the nose of a reentry vehicle by an opposing jet thermal protection system is conducted, by means of which the flow field parameters, reattachment point position, surface pressure distribution and heat flux distribution are obtained. The physical mechanism of the reduction of heat flux is analyzed. The opposing jet interacts with the freestream to form a Mach disk which enables the freestream to flow to the edges rather than interact with the surface to produce aerodynamic heating. In addition, the jet flows back to form a cool recirculation region, which reduces the difference in temperature between the surface and the nearby gas, and thus reduces the heat flux. The larger the total pressure ratio, the lower is the aerodynamic heating. To study the effect of the intensity of the opposing jet more appropriately, a new parameter RPA is defined by combining the flux and the total pressure ratio. The study shows that the same shock wave position, reattachment point position, peak heat flux position and total heat load can be obtained with the same RPA with different fluxes and total pressure ratios, which means the new ratio parameter may account for the intensity of the opposing jet and be used to analyze its influence on the flow field and total heat load at the nose of a reentry vehicle.
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    TYPES OF FLOW OVER LEESIDE OF A CLIPPED DELTA WING AT SUPERSONIC SPEEDS
    Hong Jinsen
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    1996, 17 (5): 90-95.  
    Abstract6767)      PDF(pc) (288KB)(552)      
    This paper describes a flow visualization experiment over the leeside of a slender tapered wing with a leading edge sweepback angle of 65° and a biconvex section. By using laser vapor screen, schlieren and oil flow techniques, the test was carried out at Mach numbers of 1.10, 1.53, 2.53, 3.01 and 4.01 for angles of attack from 5° through 25°. And photos of flow off body and on lee surface have been taken. The vapor screen photos show seven distinct types of flow developed over the delta region of the wing. These types of flow are displayed in a plane of Mach number and angle of attack normal to the leading edge. In the region of the side edge there are side vortices formed and in the region of the trailing edge trailing vortices shed. The variations of both the bow shock positions at different Mach numbers and the positions of separating lines induced by shock waves with Mach numbers and angles of attack are obtained based upon the schlieren plus the vapor screen photos in the sections. The oil flow visualization shows clearly primary reattachment, secondary separation, secondary reattachment lines and side edge vortices on the lee surface. The results of this test are in good agreement with experiments and numerical simulations of others.
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    Development of future fighters
    YANG Wei
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2020, 41 (6): 524377-524377.   DOI: 10.7527/S1000-6893.2020.24377
    Abstract6530)      PDF(pc) (4047KB)(9181)      
    Recent years have witnessed extensive discussions on the change of warfare forms and the development of post-4th generation fighters against the background of great power competition and batches of 4th generation fighters entering service. This paper reviews the origin of fighter generation classification and the driving elements behind each generational leap, outlining the evolution of Observe, Orient, Decision, Act (OODA) loops for air combat and proposing the essence of OODA 3.0. After a summary of the supportive and progressive relations among mechanization, informatization and intelligentization, it explores the dialectical relationship among autonomy and manned/unmanned, as well as that among platform, system of systems, and distributed operation, followed finally by a discussion of an agile and efficient development approach of future fighters.
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    MULTIPLE INPUT-OUTPUT FREQUENCY RESPONSE FUNCTIONS ESTIMATION
    Li Yuefeng;Lu Minfu
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    1986, 7 (6): 596-603.  
    Abstract6377)      PDF(pc) (517KB)(1651)      
    The theory of multiple input-output frequency response functions estimation is studied based on the finite Fourier transform. Several possible input signal types are discussed. Of them, the deterministic signal excitation is a new technique which is adrantageous over the currently prevailing random exci tation in test time, the amount of data required to be sampled and reduced and the estimation accuracy. Moreover, the hardware requirement is simpler and it is possible to run with a dual-channel FFT analyser only.In light of the theory, a software package for 6 input-multiple output FRF estimation has been developed, running in the PDP11/23 mini computer system with 64K bytes memory. The operator is prompted to select one from 4 excitation types, ( 1 ). deterministic, ( 2 ). periodic random, ( 3 ). burst random, and( 4 ). continuous random excitation. The package was used for real structures such as a free-free beam and a helecopter tail rotor. The results show that the deterministic excitation technique was the best.
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    Application of Hierarchical Partial Least Squares Regression to Development Cost Prediction of Aircraft
    Wang Liyuan;Guo Jilian;Zhang Hengxi
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2009, 30 (8): 1380-1384.  
    Abstract6369)      PDF(pc) (623KB)(708)      
    In the analysis of the development cost of an aircraft there are usually only small samples with a large number of cost drive factors. In view of this fact and considering the advantages of hierarchical partial least squares regression (Hi-PLS) in building a regressive model in the condition of a large number of variables, an application of Hi-PLS to aircraft development cost prediction is proposed using the development cost prediction of a fighter plane fuselage as an example. After the cost drive factors of the fighter plane fuselage development cost are grouped, Hi-PLS is applied to the regress of the grouped cost drive factors, and a fuselage development cost prediction model is established. The calculated results in the example show that Hi-PLS model can reflect satisfactorily the correlation between fuselage development cost and performance parameters of a military aircraft.
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    Evaluation of Equipment System Availability for Multi-echelon Maintenance Supply with Cannibalization
    RUAN Minzhi, LI Qingmin, PENG Yingwu, HUANG Aolin, WANG Shen
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2012, (4): 658-665.   DOI: CNKI:11-1929/V.20111223.1225.001
    Abstract6243)      PDF(pc) (1472KB)(513)      
    Cannibalization policy is an effective approach to improve support effectiveness. Under the current support condition, it can make equipment availability reach the upper limit. This paper establishs respectively availability models of a non-cannibalization system, a cannibalization system and a partial cannibalization system under the mode of multi-echelon maintenance supply in accordance with the characteristics of cannibalization combined with multi-echelon technique for recoverable item control(METRIC) theory. The analysis flow and method of support effectiveness are studied. In a given example, The initial spare parts inventory project is obtained under which the equipment availability is analyzed with different cannibalization policies. VMETRIC simulation is used to test the results, and the verification shows that there is high consistency between the two results, which proves the validity of the model.
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    COMPARATIVE TEST STUDY FOR THE MAXIMUM LIKELIHOOD PRINCIPLE AND THE TREATMENT OF ITS FATIGUE TEST DATA
    Xiong Junjiang;Huang Xinyu;Gao Zhentong Xia Qianyou;Gan Weimin;Zeng Benyin;Sun Rulin
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    1996, 17 (5): 28-31.  
    Abstract6159)      PDF(pc) (228KB)(467)      
    On the basis of N(S-S 0) m=C , according to the maximum likelihood principle, the formulas of P S N curves are presented which were determined by the single spot method, the single spot group method and the group method.The comparative test was made, and the test data are analyzed and treated. It was found that the P S N curves determined by these three methods were approximate.By means of the single spot method,many specimens may be saved, so the single spot method may be used to determine the P S N curves of the structure components.
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    NUMERICAL STUDY OF THERMOCHEMICAL NONEQUILIBRIUM RADIATION FLOWFIELD ENGINEERING CALCULATION
    HUANG Hua;QU Zhang-hua
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2000, 21 (5): 434-436.  
    Abstract5770)      PDF(pc) (253KB)(585)      
    The symmetric thermochemical nonequilibrium radiation flow is simulated numerically. The full Navier Stokes equations are taken as the governing equations. The two temperature and eleven species gas model is considered. The improved Nicolet "one temperature" radiation model is used. NND scheme for shock capture and time preconditional matrix technique are used for numerical solution. The result of radiation heat is got for contrasting with experiment result.
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    UAV Autonomous Control Levels and System Structure
    CHEN Zongji, WEI Jinzhong, WANG Yingxun, ZHOU Rui
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2011, 32 (6): 1075-1083.   DOI: CNKI:11-1929/V.20110328.1428.005
    Abstract5750)      PDF(pc) (1531KB)(993)      
    It is of great significance to establish a correct autonomous control level standard of unmanned aerial vehicles (UAVs) for understanding the present autonomous control level of UAV in China, and providing the guidance for research and development of Chinese UAV autonomous control technology. It is emphasized that the autonomous control levels of a UAV should be equivalent to the corresponding intelligent behavior level of a piloted airplane. Therefore, based on the analyses of human intelligent behavior mechanism, an autonomous control level of human being is given. Based on the detailed analyses of UAV autonomous control levels in USA, more suitable UAV autonomous control levels for China are suggested by canceling the original distributed autonomous level since it cannot belong to a specified intelligent action, and naming the autonomous levels according to the characteristics of military function. The technical supports of each autonomous level are analyzed; the structure of UAV autonomous control system and the function modules are established to support each UAV autonomous control level.
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    Numerical Simulation of Ejection Seat and Analysis of Performance Under Adverse Attitudes
    Yu Jia;Lin Guiping;Mao Xiaodong
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2010, 31 (10): 1927-1932.  
    Abstract5518)      PDF(pc) (1458KB)(802)      
    The escape performance evaluation of an ejection seat in China depends mainly on sled tests which may take a long time. Due to the limits of available experimental facilities, research of ejection seat perfor-mance under adverse attitudes is rarely done. In this article, a numerical simulation method is developed to evaluate and analyze the escape performance of ejection seats under adverse attitudes. The ejection progress fell into four phases. The mathematic models of each phase are built. The quaternion method rather than the Euler angular velocity equation is adopted in the free flight phase to resolve the singularity problem of a traditional 6 degree of freedom equation. The mathematic models are solved using four-order Runge-Kutta methods. The computational results agreed well with the sled test experiment data. The ejection seat attitude and trajectory are calculated and analyzed to study the performance of a escape system in adverse attitude conditions. The major causes of poor performance of an escape system under adverse attitude conditions are the instability of the seat at high speed and the influence of aircraft embroiling movement. Some basic methods to improve the escape performance of ejection seats under adverse attitudes are proposed according to the analysis.
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    Analysis of flow characteristics for hypersonic vehicle
    WU Ziniu, BAI Chenyuan, LI Juan, CHEN Zijun, JI Shixiang, WANG Dan, WANG Wenbin, XU Yizhe, YAO Yao
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (1): 58-85.   DOI: 10.7527/S1000-6893.2014.0228
    Abstract5480)      PDF(pc) (11227KB)(18345)      

    Modern hypersonic vehicles have local non-streamlined obstacles, operate at lower turbulent environment with high Mach number and lower Reynolds number and cruise in air subjected to shock and friction heating. Due to these factors, hypersonic flows are full of strong local flow structures such as strong shock waves and thick boundary layers, with severe interactions between them. Aerodynamic heating is strengthened locally by such interactions. A number of critical phenomena such as transition and pressure perturbations are quite sensitive and the competitive influences of wave and frictional drags make the lift to drag ratio have a barrier. All these are not simply dependent on the Mach number and Reynolds number, but also dependent on many dimensional parameters, so that modelling by ground facilities is difficult and a combined study of theory, numerical study and experimental measurement are necessary to solve an engineering problem. In this paper, we give an overview of the state-of-art knowledge of the most important and critical physics of hypersonic flow and discuss the methods to solve hypersonic flow problems in the most possible effective way.This review and discussion are hopefully useful for further fundamental studies and for providing a bridge between fundamental study and engineering applications.

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    A New Approach to Identify Buffet Loads for Aircraft Vertical Tail
    JIA You, YANG Zhichun
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2013, 34 (10): 2333-2340.   DOI: 10.7527/S1000-6893.2013.0214
    Abstract5420)      PDF(pc) (3479KB)(510)      

    It is difficult to perform direct measurement of the buffet loads acting on the vertical tail of an aircraft. This paper presents a novel frequency domain approach to identify buffet loads point by point from the measured acceleration responses. Based on the statistical property of the buffet loads in the time domain and spatial domain, the buffet loads are expressed as a linear combination of orthogonal functions in the spatial domain and random functions in the time domain. The spatial function is composed of a set of orthogonal functions, and the identification of buffet loads in the frequency domain is transformed into the estimation of the time function. First, the relationship between the acceleration spectral density and the generalized exciting force spectral density is obtained from the aeroelastic motion equation of the vertical tail; then, the relationship of the exciting force spectral density and buffet loads spectral density is obtained in terms of spectral decomposition. The time function can be identified utilizing the orthogonality of the spatial functions point by point. In order to address ill-posedness, a new regularization process is introduced to guarantee the stability of identification, and the optimal regularization factor is selected by Newton’s iteration. A vertical tail model is adopted to verify the feasibility and precision of the proposed method. A set of buffet loads are simulated by a computational fluid dynamics (CFD) code, and these buffet loads are exerted on the vertical tail to calculate the corresponding buffeting acceleration responses which are used to identify the buffet loads using the proposed method. Good agreements between the calculated buffet loads and estimated buffet loads validate the present method.

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    Decentralized Time-delay Adaptive Sliding Mode Control for Attitude Coordination of Satellite Formation Under Actuator Misalignment
    LU Yueyong, HU Qinglei, MA Guangfu, ZHOU Jiakang
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2011, 32 (9): 1686-1695.   DOI: CNKI:11-1929/V.20110316.1336.006
    Abstract5415)      PDF(pc) (1795KB)(708)      
    This paper develops an adaptive sliding mode attitude control system combined with time-delay control for the attitude coordination of satellite formation, especially when there exists the misalignment and magnitude error of active actuators. An adaptive update algorithm is presented to estimate the misalignment of actuators online, while the external disturbances together with random magnitude errors of an actuator are attenuated by the sliding mode controller. In addition, due to the introduction of the time-delay element, which just delays the last instantaneous control torque for a unit time, the complexity of controller design is greatly reduced. The stability of the closed-loop system is also proved based on the Lyapunov theory. Finally, the effectiveness of the corresponding controller is studied through numerical simulation. The results demonstrate that the external disturbance and random magnitude error can be attenuated by choosing appropriate control parameters, and the adaptive update algorithm can converge in a short time as well.
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    Neural-Net Based Adaptive Reconfigurable Control for a Super-Maneuverable Aircraft
    ZHU Jia-qiang;GUO Suo-feng
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2003, 24 (3): 246-250.  
    Abstract5375)      PDF(pc) (202KB)(722)      
    This paper describes a neural network based direct adaptive control approach to the problem of reconfigurable flight control of a super-maneuvering aircraft . The base control law is designed in nonlinear dynamic inversion, and neural networks are used to cancel the inversion error induced by many reasons, especially by actuator failures. Simulation of two types of actuator failures show that through adaptively canceling the inversion error, neuralnetworks can reconfigure the control instantly when there should be actuator failures. The system will keep steadyand maintain certain handling qualities.
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    Space Tethered Robot Optimal Trajectory Planning for Medium Approaching Range Based on Velocity Impulse
    XU Xiudong, HUANG Panfeng, MENG Zhongjie, WANG Dongke
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2012, 33 (8): 1531-1539.  
    Abstract5335)      PDF(pc) (2432KB)(370)      
    This paper proposes a multi-objective trajectory optimization approach based on velocity impulse for the medium range trajectory planning of a space tethered robot, The optimization includes total velocity impulse and flight time. First, a relative dynamic model and a trajectory optimization model are provided for an approaching target of the space tethered robot. Next, the non-dominated sorting genetic algorithm is employed to obtain the optimal trajectory Pareto solution set for a relative distance of 1.5 km. Simulation results show that this method can reveal the relationships among flight time, fuel consumption, planar view angle and velocity impulse number. By identifying multiple solutions, the approach can produce the corresponding optimal trajectory to meet different task requirements for a medium approaching range.
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    Experimental Study on Steady-state Operating Characteristics of Gravity-assisted Loop Heat Pipes
    Bai Lizhan;Lin Guiping;Zhang Hongxing
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2008, 29 (5): 1112-1117.  
    Abstract5237)      PDF(pc) (1870KB)(753)      
    With the extension of application field, the loop heat pipes (LHPs) may operate under various attitudes, including gravity-assisted attitude. The steady-state operating characteristics of LHPs under gravity-assisted attitude are experimentally studied and compared with those under horizontal and adverse elevation attitudes. The experimental results show that there exist two driving modes when LHPs operate under gravity-assisted attitude: gravitydriven mode and capillary force and gravity co-driven mode. When the heat load is small, the LHPs operate in gravity-driven mode, the fluid in the vapor transport line is in the two-phase state, and the operating temperature is obviously lower than that under horizontal and adverse elevation attitudes, due to the strengthen of cooling effect of the return liquid on the compensation chamber. When the heat load is bigger than the critical value, the LHPs operate in capillary force and gravity co-driven mode, the fluid in the vapor transport line is in the single-phase vapor state, and the operating temperature is approximately the same as that under horizontal and adverse elevation attitudes. In the end, the experimental phenomena are analyzed and explained based on the pressure balance in the system and the energy balance of the compensation chamber.
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    Prediction of Remaining Useful Life for Equipment with Partially Observed Information
    SHANG Yongshuang, LI Wenhai, LIU Changjie, SHENG Pei
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2012, (5): 848-854.   DOI: CNKI:11-1929/V.20120201.0944.010
    Abstract5177)      PDF(pc) (1898KB)(681)      
    In order to predict the remaining useful life (RUL) for a degraded system with partially observed information, the historical lifetime data and performance degradation data are fused together. Firstly, the hidden Markov model (HHM) is used for state evaluation to get the transition probability matrix and observation probability matrix of the system. Secondly, the Bayesian method is used to renew continually the conditional probability distribution of the equipment’s state. Then, a proportional hazards model (PHM) is used for reliability analysis to get the failure rate and reliability functions of the system. The remaining useful life distribution for the equipment is thus obtained. Case study indicates that the method can improve prediction precision effectively, which can help provide logistics personnel with a scientific basis for maintenance decision making.
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    Finite Element Analysis of Narrow Strip Laser Peening Forming
    Zhang Xingquan;Zhang Yongkang;Zhou Jianzhong;Gu Yongyu
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2009, 30 (4): 744-750.  
    Abstract5174)      PDF(pc) (989KB)(444)      
    Laser peening forming is a novel technology which employs stress waves induced by laser to form a plate. This technology is characterized by high speed, short duration, high strain rate, and non-linearity ofdeformationof materials. This article explicit dynamic analysis is implemented for shock wavesolid interaction, and implicit analysis for relaxation of pressured materials. A model is developed for numerical solution, and some key issues in finite element simulation, such as material model, pressure loading profile, and grid map, are discussed in detail. The stress and deformation field after laser peening are predicted. A series of experimentsof strip laser peening are conducted to validate the model, and the residual stresses are measured by X-ray diffraction (XRD) while deformation is measured by an arc height tester. Experimental data and numerical values are in good agreement.
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    EFFECTS OF FINE WIRE ON FLOW OVER A BACKWARD FACING STEP
    Wang Jinjun;Yu Yongsheng;Lan Shilong
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    1997, 18 (3): 345-347.  
    Abstract5151)      PDF(pc) (130KB)(733)      

    The hydrogen bubble technique was used to visualize the development and variation of a backward facing step laminar separation flow, which covered basic flow and its unsteady control. The unsteady disturbance was introduced by a wake vortex generated by a fine wire located upstream the step. The visualization results indicate that the fine wire delays the shear layer reattachment in most cases, and that only when the fine wire is at the positions x w /h=0 and y w /h=0.5, the shear layer reattachment distance could be decreased.

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