Abstract:In the application of Bayesian Networks (BN) for large scale engineering systems, computer memory for the network’s parameters increases exponentially with the nodes of the system. Aiming at this problem, one method, in which the traditional Conditional Probability Table (CPT) is replaced by the Probability Tree (PT) based on the Context Specific Independence (CSI), can effectively reduce the storage complexity. In view of that Aircraft failure is often expressed in a multi-input single-output logic gates manner, as well as that fault tree is a special kind of BN, the reductive method based on CSI was proposed for the application of the BNs modeled from the commonly used typical logic gates, and it proves that the storage need using PT is linear with the nodes, rather than exponential. Simultaneously, the formula for calculating the number of parameters needed in a PT is given. Finally, this new method (PT) is used to the fault diagnostic model of an aircraft nose wheel steering system, in comparison with the original CPT method, which shows that PT approach can effectively reduce computer memory needs.

Abstract:Stiffened wing panel is easy to lose efficiency due to buckling under the loading of compression, shear, torsion and bend. The concept of stability efficiency factor introduced to carrying efficiency of stiffened composite structures in order to realize optimal design of stiffened composite wing structures. The best design principle that taking the equal of the of the critical buckling load and the static load is adopting. We obtain efficiency factor according to the principle of optimal design and the buckling analysis of stiffened panel, and get the efficiency factor graph through the PCL parametric modeling and analyzing. The research results demonstrate that: the method that building the carrying efficiency of stiffened panel model can rapidly realize the wing structural design and obtain obvious effect of high carrying efficiency.

Abstract:The structural forms of cylindrical stiffened composite panels are widely used in the aerospace field. The weight and pressure bearing capacity are determined by the structure layout. Aiming at layout optimization of cylindrical stiffened composite panel, discretization method is applied to the optimization. Stringers’ distance and panel’s length are dispersed into several values and typical sections are chosen for the stringer. To optimize ply thickness of 0°、±45°、90° and section sizing of stringer ,structural weight is chosen as objective function and critical buckling load is constraint. The 700 results indicate that t-section stringer is most favorable in structural lightweight design. the design curves are also obtained.

Abstract:This paper study three algorithms converting aerodynamic load to FEM node load which are applied in different wing structures with different kind of load, and comparatively analyzes these three algorithms. This paper through a numerical example analysis pros and cons of the algorithm uniform load ,spanwise elliptical distribution, the typical straight wing,and the three-dimensional wing, This article which discuss converting aerodynamic load to FEM node load has certain referential significance for engineering applications.

Abstract:Based on the continuum damage mechanics, this paper established a 3D laminates model with a large opening under shear loading ,calculated the ultimate strength and simulated the damage process. The numerical results were compared with the relevant experimental study and demonstrated the feasibility of this method. Then ,the paper established a finite element model of an aircraft porthole structure to study the mechanical behavior under pure shear load of composite material containing reinforcing frame structure with a large opening and analyzed the damage law.

Abstract:According to the demand of the condition monitoring system of scramjet inlets, 2-D flow field of the scramjet inlets was numerically simulated; the numerical simulation results of the scramjet inlets at different Mach number and different pressure were presented. The surface static pressure distributions of the inlets from start to un-start was analyzed and the start judgment criterion was given. After inlet monitoring parameters are determined, extension theory was applied to the sensor selection, thus establishing a comprehensive evaluation method of scramjet sensor selection. Then An example of pressure sensor using this optimal selection method verified the effectiveness of this method. The research provides reference for the establishment of the scramjet parameters measurement scheme and the design of condition monitoring system.

Abstract:The high cost and time wasting of Experiment and CFD on obtaining flow field make it hardly to meet the requirement for aircraft design. Utilizing the proper orthogonal decomposition combined with interpolation, we can quickly get the flow fields for aircraft design with only a small amount of sample flow fields obtained from experiment or CFD. Through the studying of the flow fields of RAE2822 and combining the proper orthogonal decomposition with two different interpolation method., We carry out the quick method for predicting flow fields. After compared the predicted flow fields with the flow fields obtained direct from CFD, we concluded that the the proper orthogonal decomposition combined with interpolation is a reliable method on flow field predicting.

Abstract:The dynamic feature makes flapping-wing much different from fixed-wing. In order to study the unsteady aerodynamics of flapping-wing, a flapping-wing wind tunnel experimental system based on virtual instrument was set up, which can perform real-time measurement of aerodynamic force, flapping angle, power consumption and so on. The Strouhal number (St) was regarded as a key issue of unsteady aerodynamics. A series of wind tunnel experiments, based on the definition of St, were carried out to explore the influence of the St, which was varied by different flapping amplitude, flapping frequency and wind velocity. The lift, thrust and propulsion efficiency of the flapping-wing in different conditions were analyzed, and the influence rule of St on aerodynamic characteristics for flapping-wing was get. The experiments showed that, as St increased, the aerodynamic of flapping-wing increased significantly; and the propulsion efficiency kept in a high level when St was in a certain range.

Abstract:In order to grasp the level and trend of various technical parameters of turbofan engine correctly. The models and corresponding programs for performance calculations and evaluations of size and weight of turbofan engine were set up. The technical parameters were collected of fifteen foreign typical turbofan engines from 2 to 4 generations, which were evaluated with the programs mentioned above so that the level and developing trends of these parameters were obtained. Then, the technical parameters were predicted of the advanced turbofan engine of next generation. Based on the developing trends of the technical parameters, the possible engine integration design directions of next generation advanced turbofan engine are explored, which helped to indicate its developing trends and method of integrated design.

Abstract:To solve the attitude control problem of small quadrotor according to its complex coupling, non-linear and serious internal/external disturbance feature, a control scheme based on active disturbance rejection control technique is proposed. The dynamic model is established with Newton-Euler formalism, and the uncertainty, coupling and parameter perturbation are considered as total disturbance. Extended State Observer is used to estimate and compensate the total disturbance, the Non-linear State Error Feedback is used to restrain the compensate error, a model for simulation is established. The result of the simulation shows that the Extended State Observer of the Active Disturbance Rejection Control technique can estimate/compensate disturbance well under circumstance of parameter perturbation and disturbance. Attitude controller based on Active Disturbance Rejection Control theory shows good dynamic quality, steady-state accuracy and strong robustness.

Abstract:In the development era of wing-in-ground effect vehicle, there remains two major technical issues: first, in the process of taking off, the lift-drag ratio is too small to lift the aircraft body out from the water rapidly; second, when landing, aircraft`s body may crash heavily into the water, which wears it out. To solve above issues, according to the hull theory, wing design theory and the Theodore Von Karman water impact theory, this paper designs a new hydro-ski applied in wing-in-ground effect craft. and uses CATIA to draw 3D model of the hydro-ski, and the FLUENT to figure out the craft`s hydrodynamic characteristics. This research concludes that lift coefficient and drag coefficient of the hydro-ski increases as the angle of attack increases. In addition, the lift-drag ratio curve is shown as a parabola, peaking at 5°. In the meantime, when the incoming flow velocity is 2m/s, the lift coefficient, drag coefficient and CL/CD is larger than that of the others. To conclude, the hydro-ski helps lift the craft body out from water rapidly when taking off and reduce impact force to the hull when landing.

Abstract:Refinement design requirements of modern aircraft configuration require airfoil parametric methods have precise geometry control ability. Geometry control ability evaluation of classical airfoil parametric methods can provide reference for designers to choose suitable airfoil parametric method for engineering problems. Five representative classical airfoils are used as test airfoils in this paper and four classical airfoil parametric methods’ geometry control ability is evaluated based on the standard wind tunnel model tolerance requirement. The four airfoil parametric meth-ods are Hicks-Henne, B-spline, PARSEC and CST respectively. The evaluation results indicate that airfoil geometry control abilities are different between the parametric methods and each method has its own applicable scope. Every parametric method’s applicability is analyzed based on the evaluation results and its inherent characters.

Abstract:Aims at the interference of the balance component output values caused by assembly stress when installation it, on the premise of the unchanged length of the balance, this paper uses finite element simulation and analysis it based on different length of the fixed end of the balance component. It turns out the assembly stress indeed affect the output result, but not changed obviously with the change of the length of the clamped end. Some measures should be done to eliminate the assembly stress during the balance process and texts.

Abstract:Alternative current (AC) and nanosecond pulse (NS) plasma dielectric barrier discharge (DBD) is applied to the active control of the asymmetrical vortices over the cone of the cone-cylinder. The characteristics of the AC-DBD and NS-DBD is discussed. The experiment is performed in a low speed wind tunnel. The angle of attack is 45? and the wind speed ranges from 5 m/s to 22 m/s. Flow control modes of the actuator are plasma off, port on and starboard on. The result shows that the asymmetrical field can be mirror symmetry control by port on and starboard on of AC-DBD at 5 m/s, but the NS-DBD is not effective. As the wind speed increased, the function of the AC-DBD on asymmetric vortices is gradually disappears, meanwhile the function of NS-DBD is increasing. When the wind speed reaches 22 m/s, NS-DBD can get the asymmetrical field mirror symmetry, but the AC-DBD is not effective. This implies that the NS-DBD is more effective to control the separated vortices field at the higher wind speed relative to the AC-DBD.

Abstract:The UAV features negative stagger and wing tip gap of 5% wing span, and strong interference exist between components of the wing systems. Reynolds Averaged Navior-Stokes scheme is adopted to analyze its drag polar, stall and pitching moment characteristics. The research revealed that the induced drag is reduced by 9% compared with equal mono-wing, which is close to the theoretical result; The trimmed maximum lift coefficient drops significantly due to the requirements of static stability and trim, which are realized by -4 degree negative incidence angle of aft wing; Nose up pitching moment is observed at large angle of attack after stall, which attributes to the forward wing tip stall due to its sweptback, as well as the decreased efficiency of the aft wing in the wake of the forward wing.

Abstract:Study on the cooling structure of vectored nozzle is very important for developing the vector propulsion technology in aero-engine. To study the cooling technology of axial-symmetric vector nozzle, the slot film, multi-hole film and composite film have been applied in the heat shield, and the nozzle wall temperature in after burning condition have been computed. In this work, the heat balance equation based on heat transfer of nozzle has been developed and solved with Newton Rafael method to give wall temperature. Heat transfer of film cooling was computed with empirical formula of cooling effectiveness. And radiative heating from the gas was computed with net radiation analysis method in an enclosure. One axial-symmetric vectored nozzle with 20° deflection angle has been taken for investigation, temperature of the nozzle and heat shield without film cooling is firstly computed, then temperature with 9 film structures were computed. For verification of the computation method, wall temperature of one axial-symmetric nozzle in after burning condition has been computed and compared with results of reference. Study of this work shows that the heat shield plays a good cooling effect for convergent part of nozzle, and film cooling on the heat shield can reduce its temperature remarkably. Comparing with convergent part of nozzle which is protected by the heat shield, temperature of the divergent section of nozzle is very high which needs further cooling.

Abstract:The boarding door is an important moving part of aircraft and often made of metal, so it has great potential for weight loss. The purpose of this article is to analyze the feasibility of using composite material in the structure design of boarding door. According to the CCAR and design criteria for composite structure, a research on structure design and analysis of composite boarding door was carried out in this paper. The best one of three beam design options was chosen based on stress and strain analysis using FEM. Then the structural strength was analyzed by using the method of overall-local single-bolt mode. Through the research, Using the composite materials in structure design of boarding door is feasible, then the key points in the design of composite material boarding door were also summarized, and the foundation of using composite materials in engineering design was established.

Abstract:The application of titanium alloy for the commercial aircraft fuselage can make the structure weight saving, and improve fatigue life and the corrosion-resistant capability. The quantity of titanium alloy increased in the most advanced commercial aircrafts. The properties and advantages of the titanium alloys have been described detailedly. The recent applications of titanium alloys and fasteners on commercial aircrafts have been introduced and the reason has been analysed. The opportunity and the challenge of titanium alloy applications have also been presented.

Abstract:Civilian airplane is the first airplane type to fully use CCAR25 for validating the airworthiness, the flight test of control surfaces jammed situation is highly focused by CAAC. To ensure civilian airplane flight control surfaces jamming flight test successfully, surfaces jammed scheme and fight test method are studied in the paper. Three schemes of surfaces jamming are introduced and analyzed, emphasizing the principle and flight safety control scenario of the front-injected method, finally typical surfaces jammed simulation flight test method is formed . The scheme and method are validated on the civilian airplane iron bed, the results indicate that the front-injected method meets the requirements of surfaces jamming and is highly feasible.

Abstract:To better understand the effects of rotation on the internal channel heat transfer characteristics, the flow and heat transfer condition in an internal channel with 90° ribs are investigated using three-dimensional numerical simulation method. The inlet Reynolds number is 17,000 and three outlets mass flow discharge ratio is 1:2:1. The Rotating number and the hydraulic diameter divided by radius of gyration range from 0 to 0.09 and 0 to 69.6, respectively. The influence of Rotation number and Radius of gyration on heat transfer coefficient were achieved. Results show that the pressure coefficient increases along radial outflow and decreases along radial inflow due to rotational force; in the trailing surface, Nusselt number (Nu) in radial outflow passages increases and the Nu in radial inflow passage decreases with the augment of the rotation number, the variation of Nu in the leading surface contrary to that of the trailing surface; the Nu along the flow direction in trailing and leading surface are slightly enhanced when gyration radius to hydraulic diameter ratio increase, the surface heat transfer coefficient is affected on the variable radius of gyration.

Abstract:This issue analyse the necessity of nondestructive testing technology of laser ultrasonic in compositesj, introduce the sitution of this technology’s development, studying its critical technical point, including how to excite and receive ultrasound using laser beam, and the interferometer, at last, point the problem of the existing ultrasonic system, and what to do in the future.

Abstract:In order to study the differences of dynamic friction characteristics between domestic rope pulley and imported rope pulley in certain aircraft operating system, and provide data support and engineering reference for the improvement of rope pulley design in the operating system, based on relevant domestic and abroad paper materials and engineering practice, this paper analyzes the dynamic friction characteristics of imported rope pulley, which upcoming adopted in this operating system. Applying basic principles of classical mechanics theory, comparative analysis of dynamic friction characteristics from the domestic rope pulley being used, and using Labview software for processing and spectral analysis software, it verifies that the dynamic friction of imported rope pulley is small, and the stiffness is large, which meets the requirements of engineering design, and provides a project basis for improvement of the operating system.