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Chen X.,Center for Monitoring Research | Ren H.,Center for Monitoring Research | Wang J.,University of Illinois at Urbana - Champaign | Chen Y.,Shanghai Aircraft Design Institute | And 2 more authors.
30th Congress of the International Council of the Aeronautical Sciences, ICAS 2016 | Year: 2016

Taking advantage of advanced sensors and data processing techniques, certain states of complex systems in aircraft can be monitored in realtime. However, it still takes efforts in practical trouble shooting in order to locate the exact faulty component after some malfunction alerts. This often consumes great time and energy, sometimes may even cause flight delay. A new diagnostic approach is developed based on a hierarchical Bayesian network that can combine both Fault Mode and Effect Analysis (FMEA) and real-time monitoring information. An aircraft brake system, as one of the typical electromechanical systems, is selected and two different statistical models are proposed in case study. The intelligent fault diagnostic approach has the potential to improve the efficiency and accuracy of aircraft system diagnosis.

Bai J.,Northwestern College | Liu N.,Northwestern College | Qiu Y.,Northwestern College | Chen Y.,Shanghai Aircraft Design Institute | And 2 more authors.
Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University | Year: 2013

Carefully considering the landing configuration of a large civil transport aircraft, we apply the CFD computational method and mesh generation strategy, whose validity is confirmed by wind tunnel experiments conducted by us, to study the influence of nacelle chine on high-lift efficiency. The results show that the flow mechanism of nacelle chine is similar to that of large sweep delta wing. The intensity and the location of vortex flow, which are induced by nacelle chine, are the key elements of high-lift efficiency. Moving the vortex outer or downward or enhancing its intensity can increase high-lift efficiency. Through putting nacelle chine downward, the vortex will be moved downward and outboard of wing, but the influence of intensity will not show a monotonic way. The vortex will move upward and inboard of wing and its intensity will be enhanced by putting nacelle chine backward. Increasing the angle incidence or obliquity of nacelle chine can move the vortex upward and outboard of wing, and both of them can increase the intensity of vortex. Increasing the sweep angle (reducing the area near leading edge) of nacelle chine will move the vortex downward and outboard of wing, but its intensity will be reduced. Therefore, the influence of these parameters (location, angle of incidence and so on) upon high-lift efficiency are not monotonic. Getting the optimum parameter combination needs a lot of analysis of flow fields. Besides, the design of nacelle chine will be restricted by cruise configuration, the reverse thrust device and the structure of engines; they must be taken into consideration in design process.

Qiu Y.-S.,Northwestern Polytechnical University | Bai J.-Q.,Northwestern Polytechnical University | Huang L.,Northwestern Polytechnical University | Zhu J.,Northwestern Polytechnical University | And 3 more authors.
Kongqi Donglixue Xuebao/Acta Aerodynamica Sinica | Year: 2012

By numerical simulation and wind tunnel experiment data, the influence of wing-mounted engine nacelle on high-lift system and the effects of nacelle stake setting at different positions have been investigated. The results indicated that: the separation flow from engine nacelle at high angles of attack and the slat cut-off have serious influence on aerodynamic characteristic of high-lift system. They caused a very large space of low-speed area above main wing and flap. An engine nacelle strake could improve this situation by setting at proper position. The mechanism is: a strong vortex would caused by nacelle strake at high angle of attack, then the vortex transport energy from freedom flow to the low-speed flow space. And the vortex would induce the low-speed to flow faster. Finally, the low-speed flow space reduced. But the position of nacelle strake need to optimize, setting it at unsuitable position will cause more lost of maximum lift.

Han Z.-R.,Nanjing University of Aeronautics and Astronautics | Lu Z.-L.,Nanjing University of Aeronautics and Astronautics | Guo T.-Q.,Nanjing University of Aeronautics and Astronautics | Chen Y.-C.,Nanjing University of Aeronautics and Astronautics | Chen Y.-C.,Shanghai Aircraft Design Institute
Kongqi Donglixue Xuebao/Acta Aerodynamica Sinica | Year: 2012

Based on the compressible viscous flow, disorder degree of the flow velocity is proposed to be the indicator variable for a grid adaption. Jameson cell-centred scheme of Finite Volume Method and five-stage Runge-Kutta approach/dual time-stepping approach are used to solve steady/unsteady N-S equations. Spalart-Allmaras One-Equation is employed to the simulations of turbulent flows. In order to improve the capability of catching flow separation characteristics, the grid adaption method is used during the numerical simulation of the two-dimensional static stall and dynamic stall. The example results indicate that the grid adaption method can obviously improve the calculation accuracy in the case of increasing a small amount of grid cells.

Bai J.-Q.,Northwestern Polytechnical University | Qiu Y.-S.,Northwestern Polytechnical University | Chen Y.-C.,Shanghai Aircraft Design Institute | Li Y.-L.,Shanghai Aircraft Design Institute | Zhou T.,Shanghai Aircraft Design Institute
Kongqi Donglixue Xuebao/Acta Aerodynamica Sinica | Year: 2012

By numerical simulation, the influence of slat tracks and flap track fairings on aerodynamic performance of high-lift system and its flow mechanism have been investigated. The results indicate that these brackets just bring a little descent to the linear part of lift curve, but cause a remarkable loss to the angle of stall and maximum lift coefficient. The mechanism lies in that low-momentum strong wake flow generated by slat tracks mixed with the boundary layer of main wing, which causes the remarkable loss of the lift. At high angle of attack, slat tracks will generate large area flow separation. The flap slot section area diminishes for blockage effect of flap track fairings. This made the high speed flow of flap slot faster, and made for blowing the separation flow on flap surface away.

Li Y.,Northwestern Polytechnical University | Bai J.,Northwestern Polytechnical University | Guo B.,Shanghai Aircraft Design Institute | Yang T.,Northwestern Polytechnical University | He X.,Northwestern Polytechnical University
Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University | Year: 2015

First we explore the influence on the aerodynamic characteristics of the tilt angle, height and angle of the installation of the blended winglet. Then, we build the optimization system with FFD technology, Latin hypercube sampling method, Kriging surrogate model and the improved particle swarm optimization algorithm. We apply this system to the blended winglet; through the appropriate arrangement of the FFD control body frame we achieve a framework for FFD parameterized design of multiple control winglets. Optimization results show that the drag of the designed blended winglets decrease obviously as compared with that of the original configuration. Compared with the parameter analysis of those three wingtip devices ("wingtip extension", "eddy diffusion" and "double fork scimitar"), we draw some valuable conclusions for the design of wingtip devices.

Bai J.,Northwestern Polytechnical University | Liu N.,Northwestern Polytechnical University | Qiu Y.,Northwestern Polytechnical University | Zhang X.,Northwestern Polytechnical University | And 3 more authors.
Kongqi Donglixue Xuebao/Acta Aerodynamica Sinica | Year: 2014

This paper applies the methods of CFD simulation of fluid flow, which are validated by wind tunnel results, to analyze the influences of installation location of nacelle chine on the lift performance of landing configuration from the change of spatial vortices. The numerical simulation results show that because of the influences of nacelle and pylon, the end of slats and cuts of main wing left by the deflection of slats, will induce a series of vortices in high angle of attack (α), which could bring separation in the upper surface of main wing easily. The vortex induced by nacelle chine can depress these vortices and low speed region of flow field above the main wing behind nacelle so that the stalling α and maximum lift coefficient will be improved. Regarding the landing configuration in this paper, its stalling α and maximum lift coefficient are increased by 2° and 0.15 respectively by the installation of nacelle chine. The vortex induced by nacelle chine will move downwards once the chine is put back or down, which leads to stronger restraint effects to other vortices and lower speed region. In order to increase the stalling α and maximum lift coefficient of landing configuration, both of the location and strength of vortex induced by nacelle chine must be taken into consideration in the design process. Because of some geometry restraints and adopting above investigation results, the location of nacelle chine is redesigned through the tradeoff study for the location and strength of space vortex. The CFD result shows that for the redesigned location of chine, geometry restraint is satisfied and the loss of maximum lift coefficient of landing configuration is less than 0.015, which still meets the design requests.

Wang Y.-Y.,Northwestern Polytechnical University | Zhang B.-Q.,Northwestern Polytechnical University | Chen Y.-C.,Northwestern Polytechnical University | Chen Y.-C.,Shanghai Aircraft Design Institute
Applied Mathematics and Mechanics (English Edition) | Year: 2011

A robust airfoil optimization platform is constructed based on the modified particle swarm optimization method (i.e., the second-order oscillating particle swarm method), which consists of an efficient optimization algorithm, a precise aerodynamic analysis program, a high accuracy surrogate model, and a classical airfoil parametric method. There are two improvements for the modified particle swarm method compared with the standard particle swarm method. First, the particle velocity is represented by the combination of the particle position and the variation of position, which makes the particle swarm algorithm a second-order precision method with respect to the particle position. Second, for the sake of adding diversity to the swarm and enlarging the parameter searching domain to improve the global convergence performance of the algorithm, an oscillating term is introduced to the update formula of the particle velocity. At last, taking two airfoils as examples, the aerodynamic shapes are optimized on this optimization platform. It is shown from the optimization results that the aerodynamic characteristic of the airfoils is greatly improved in a broad design range. © 2011 Shanghai University and Springer-Verlag Berlin Heidelberg.

Xiao K.,Shanghai Aircraft Design Institute
Cailiao Gongcheng/Journal of Materials Engineering | Year: 2012

High temperature compression tests at a temperature range of 200-500°C with various strain rates 0.001-1 s -1 on a conventional as-cast AZ31 were carried out using a Gleeble-1500 dynamic material testing machine. The effects of deformation temperature and strain rate on microstructure evolution of the as-cast AZ31 magnesium alloy were analyzed by introducing temperature-compensated strain rate (Zener-Hollomon parameter, Z value). The results of the microstructure observations indicate that as the volume fraction of DRX grains increased, the size of DRX grain size is decreased. The mean size of the DRX grains decreases and the volume fraction of DRX grains increase with an increase of Z value. The three dimensional graph has been established to provide a clear guideline for forming craft selection.

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