Abstract:Aircraft gust response refers to the transient change of aircraft flight parameters ,the structure load conditions in the event of gusts. The additional aerodynamic gust loads will lead to changes in aircraft flight status , gusts over substantial value will affect the performance and safety of flight. In view of this situation , this paper based on CFD technology to solve unsteady N-S equations , introduces " grid speed" in the computing grid to simulate gusts , and research aircraft gust response in time domain. First calculate aerodynamic characteristics of three-dimensional aircraft model SWIM (Simple Wake Follower Model) in the trailing vortex , CFD calculation results with the results of wind tunnel experiments , literature CFD results are in good agreement ; Then simulate the flight path of SWIM diving across trailing vortex field , achieving the CFD-6DOF trajectory simulation of SWIM in the trailing vortex. Trajectory simulation results show that the jitter , sinking , changing flight conditions , intense flip phenomena occur while SWIM flying in trailing vortex are similar with the trajectory characteristics of aircraft flying into the wake vortex.

Abstract:When aircraft is damaged with its wing lost partially, its mass and wing span may change obviously, which may result in the changes in aerodynamics, mass properties, and the center of gravity that can compromise the stability of the damaged aircraft. A fight aircraft is mentioned in this paper and the changes of this damage is discussed. With these changes, we summarize revised flight dynamics equations for the damaged aircraft, which will provide an important theoretical basis for anti-discrimination class.

Abstract:Fracture toughness under plane stress is used to describe the ability of thin metallic sheet to withstand unstable crack propagation. However, it shows strong sensitivity to the specimen geometry during tests. In this study, the experiment to obtain K-R resistance curves of a typical type of aviation materials, 2524-T3 aluminum alloy sheet, was conducted using middle crack tension specimen with different width and initial crack length and hence determine the plane stress fracture toughness K_c and apparent fracture toughness K_app. The results showed that the K-R resistance curves highly relevant to specimens’ width but less to the initial crack size. The fracture toughnesses and apparent fracture toughnesses are affected apparently by both the specimen width and the initial crack length. An apparent fracture toughness criterion including the width effect is proposed to predict residual strength. Meanwhile, with close observation of the role of “flow stress” (the mean of yield stress and ultimate stress) in the final fracture of cracked cross-section, a model for residual strength evaluation was put forward based on the net section yielding criterion. This model exhibits both net-section yielding and stable ductile tearing during the fracture of ductile metals.

Abstract:In the design and manufacture of aircraft composite skin structure, composite Ω stringer or T stringer reinforced skin panel is typical airplane integrated structure. The study on the two different structures of composite reinforced panels in the world nowadays is mainly about whether the reinforcement geometrical shape, strength and weight could meet the structure performance requirement. Rare researchers study on the process comparison and analysis of the two different kinds of stringer structures. However, the study on process comparison and analysis of the two different kinds of stringer structures on the early design stage could help with the balance between reinforced panel structure performance and cost, therefore to achieve optimum design with low manufacture cost, as being not only the basis of material choosing, but being helpful for optimal process. The thesis studies on aircraft composite typical Ω stringer and T stringer co-curing process structure through simulation of different manufacture process tests, strength comparison tests etc., then we gain mass of data of manufacture advantages and disadvantages, strength comparison, individual process characteristics etc. We propose methods of different structure process analysis in aircraft design and manufacture concurrent engineering. Through the comparison analysis of the data, we illustrate the process advantages and disadvantages of the two structures. Then we summarize the analysis and research result and make a conclusion.

Abstract:The most type of propeller used in medium/small UVA with piston motor are two blades and fixed angles. The root and tip of this propeller is wider, and the mid part is narrow. But the rotate speed is higher and flight speed is lower in cruising condition, and the thrust is smaller in the step of taking off after using this propeller in fact. It is nor better for UAV developing in future. Therefore, Several types of propellers are designed for the same UAV platform with the same piston motor in this paper. The capabilities of these propellers in zero velocity and in cruising velocity are tested in NF-3 wind tunnel. According to the analyse of test data, the type of propeller with rectangular blade is better than others in efficiency, thrust coefficient and power coefficient, and especially its rotate speed is smallest in the same power imported, So, this type of rectangular propeller is very fit for the medium/small UVA with piston motor.

Abstract:Research of thrust asymmetry compensation control based on turbofan engine performance deterioration mitigating control (EPDMC) was conducted. An outer thrust loop based on nominal control system was investigated, which manipulates thrust indirectly and minimizes thrust asymmetry through setting expected thrust followed by twin engine. Then key technology including thrust setting, parameter estimation and speed command modification was introduced. Simulation performed under MATLAB/Simulink conditions indicates the feasibility of the thrust asymmetry compensation control system in automatic thrust synchronization.

Abstract:The solar powered aircraft ribs are light, thin structure of large number. Proper rib structural layouts are important to the aircraft lightening and the wing stiffness etc. Based on the rib structures of some typical solar powered aircraft, a topology optimization design method of the ribs were introduced: Firstly, a typical solar powered aircraft rib structure was optimized, based on the Bi-directional Evolutionary Structural Optimization(BESO); Secondly, the specific designs of the rib structure were given; Lastly, the structural strength, stiffness and stability of the rib were verified through Finite Element Method. Though the method in this paper, a more suitable structural layouts of the solar powered aircraft ribs was obtained.

Abstract:At 0:00 on November 22, 2007. China began to implement Reduced Vertical Separation Minimum (RVSM), research is extremely important to RVSM airworthiness. However, China RVSM airspace with respect to the North Atlantic airspace in March 27, 1997 has began to reduce the vertical interval has 10 years of blank period. According to the relevant aviation manuals, reference implementation experience of other countries and regions of RVSM operations, combined with our the actual situation of China’s civil aviation and management systems, to study the RVSM airworthiness of the aviation technology. Article on rice Inch height of RVSM operations show the differences encountered problems and high layer configuration problems were analyzed, and gives a way of using the corresponding lookup the conversion method to solve the problem of meters English level, so that our RVSM operations with international standards.

Abstract:Lightening the structure weight is one of the most important targets of the aircraft design. It could be realized by applying the composite material instead of the metal and optimizing the structure. An optimization design is done for a high aspect ratio composite wing in this paper. The design variables are the position of the spars and the composite layup. The target is to minimum the weight. And the constraint conditions are the structural strength and stiffness. The optimization is done through genetic algorithm with Matlab calling Patran. The composite layup library is built to solve the problem that the number of the composite layup variables is too huge. The result shows that this optimization method is effective and it is useful in engineering design. At the same time, the composite layup library also can be widely used in other works related with composite layup optimization.

Abstract:In order to improve the performance of modern rockets, large area-ratio nozzle s are adopted. Over-expansion occurs in large area-ratio nozzles due to high back pressure at low altitudes, leading to unsteady and asymmetrical flow separation inside the nozzle, as well as severe side-loads phenomena. As a result, the large side-loads may lead to remarkable problem of fluid/structure interaction. In this paper, the situation and progress on nozzle flow separation is reviewed. Research object and product of different period were described. Several factors that induce side loads are enumerated, including transition of shock pattern, declining separation line, pressure pulsation, buffeting, fluid/structure coupling, etc. On this basis, progress and research methods on fluid/structure interaction are further analyzed, including experimental and numerical methods. Besides, new research objects that are probably related to side loads are pointed out. Finally,several corresponding critical mechanical problems which need to be considered and settled during large area-ratio nozzle design are discussed, and the suggestion about critical aspects of side-loads needing to be further studied is put forward.

Abstract:This paper analyzes and researches the RAT generator natural icing flight test of a type of domestic aircraft in its development process. Firstly, this paper introduces the reason and purpose of the RAT generator natural icing flight test, and the civil aviation standards for natural icing environment. Secondly, the paper introduces the flight test method for RAT generator natural icing flight test. Finally, the test results are analyzed. The results show that RAT generator flight test of natural icing environmental condition meet airworthiness regulatory requirements, RAT generator manual release function can be realized in the foreseeable natural icing environmental condition, and the power supply function is normal.

Abstract:In order to get the benefits of non-conventional configuration in regional aircraft design to improve its performance, and avoid its weaknesses, the blended configuration with non-conventional and conventional layout is proposed. This configuration improves the aerodynamic characteristics of re-gional aircraft utilizing the advantages of the flying wing, meanwhile avoid the negative aspects. By improve and optimize a large number of design programs through gradual iteration, the blended configuration with non-conventional and conventional layout is obtained. The aerodynamic performance of this layout is better than the new generation of regional aircraft. Such as, the cruise lift to drag ratio is increased about 7.5%, drag divergence Mach number is increased about 7.5%, and cruise factor is increased about 7.5%. At the same time it has good airport adaptability. And the program has the potential to further optimize the performance improvements, and laid a foundation for the research unconventional layout of the transport aircraft in the future.

Abstract:Fore-loaded airfoil has less pitching moment and better stealth ability, it can have both good aerodynamic and stealth per-formances at the same time. It is ideal airfoil for flying wing aircraft. Multi-points integrated optimization design research of Fore-loaded airfoil is present in this paper based on a flying wing aircraft. Airfoil parametric method, aerodynamic performance evaluation method and optimization algorithm are applied during the research. Firstly, geometry control abil-ities of classical airfoil parametric methods are evaluated, and the evaluation results shows that Hicks-Henne and CST methods have more powerful control abilities. Then, the design states and optimization model are established according to the flying wing aircraft design requirements. The integrated optimization design of Fore-loaded airfoil is implemented afterwards with CST parametric method, NS equation numerical solution method and genetic algorithm, and satisfying design result is obtained. Compared with the reference airfoil, the optimized airfoil has larger relative thickness and better aerodynamic performance.

Abstract:In order to study the new methods to improve the aerodynamic and acoustic characteristic of multi-element airfoil, this paper presents the lift characteristic of two-element airfoil by wind tunnel test and numerical simulation with the upper surface of flap in smooth and rough situation, respectively. The test was accomplished in NF-3 low-speed wind tunnel of NWPU. The experiment model was two-dimensional model with 87 flush orifices. The smooth and rough situations were achieved by filling sound-absorbing porous material in upper surface of flap and using plastic membrane to overlap it or not. The numerical simulation was carried on the two-dimensional simulation of ANSYS Fluent with the unstructured mesh and k-ω SST turbulence model. The result shows that when sound-absorbing material is exposed, the low and medium frequency noise is eliminated. But the rough surface causes the decrease of average velocity in slot, the increase of fluctuation velocity and the reducing of the lift coefficient of airfoil. Thus, it is essential to keep the smoothness of upper surface of flap. Moreover, in multi-element airfoil wind tunnel test, in order to guarantee the quality of data, the surface cleaning must be done in time to maintain the surface smooth.

Abstract:Spalart-Allmaras(SA) one-equation turbulence model has been prevailing used in the numerical simulation of engineering turbulence flows. In this paper, the flow situations of small incidence, middle incidence, large incidence of a typical fighter are concerned. And the influences of eight model parameters in SA turbulence model on the calculated turbulent flow fields are analyzed by using the uniform design of experiments. The results show that under different flow situations do the model parameters exhibit different influences on calculated results of lift and drag coefficients. For attached flow of small incidence, the influences of the parameters cv1 and cb1 are much greater than other parameters, and for middle incidence and large incidence, the parameter of largest influence is cb1. Then the turbulence model parameter estimation method is developed and utilized for the estimation of cb1 value for large incidence case. It is found that when the parameter value of cb1 decrease moderately, the calculated lift and drag coefficients agree with the experimental results much better. This could be attributed to that the conventional value of the model parameters are calibrated from free shear flow but there exists some difference in the development of eddy-vicosity and shear stress between the large incidence separated flow and the free shear flow.

Abstract:In the prospective of the cost-effective ratio, the relation between spare parts’ delay time and their costs is researched, and the purchase strategy and simulation methodology of spare parts are provided. Finally, take B1-B Bomber as an example, the results under different purchase strategies are computed by the simulation method. And the metrics and the feasible of the strategy are analyzed with figures and table.

Abstract:Inflatable wings are gradually welcomed by vehicle designers because of its superiority that inflatable wing has lower weight, can be tucked and conveniently carried. Inflatable wing is a typical of flexible inflated structure, which involve the advancing front of the distorted UAV that can be applied to tucked vehicles, airplane of earth science research and Mars exploration aircraft etc. This paper adopts the internal tangential circle to approximate standard airfoil profile and use static mechanics to give demonstration. Based on NACA0018, a series of approximate inflatable wings are designed by controlling the numbers of the tangential circles. All designed wings’ aerodynamic characteristics are analyzed and compared using CFD, then basic characters of the conformality method can be obtained. The results show that lift coefficients of inflatable wing lower than standard airfoil, which can reach 80% of standard airfoil, meanwhile ,it variable range is small along with internal tangential circle numbers. But drag coefficients vary obviously, which increases 1~1.5 times correspondingly. Lastly, an inflatable wing prototype is produced , its flying qualities are explored by several test flights.

Abstract:Abstract: Emergency Evacuation Door(EED) is the only exits in a flight test airplane for flight crew evacuation, whether the EED internal mechanism is functional or not directly affects the flight crew evacuation. This paper analyses the motion principle of the EED in a certain type of flight test airplane from two aspects(lock and unlock) based on the characteristics of its mechanism. In addition, virtual prototypes of the mechanism are established with Lms.Virtual.Lab Motion software to simulate and analyze the motion of EED, with and without pressure load respectively. The result shows the mechanism performs well in terms of operation protection during unlocking and locking, The operating force to unlock the protection mechanism in pressurized condition is larger than that in non-pressurized condition. However, once the protection mechanism is unlocked, the pressure load can assist in opening the door, greater pressure load will result in faster response.

Abstract:This paper analyzed the advantage of fiber reinforced composites when applied in mould, compared to traditional metal and invar; fiber reinforced composites used for mould and the mould fabrication process were introduced; the domestic and foreign application and development trend of fiber reinforced composites mould were introduced ; then the necessity and urgency of developing composites mould were emphasized.

Abstract:Experimental study and finite element analysis has been performed on designed specimen to research the widespread fatigue damage characteristics of fuselage skin repair for civil aircraft. Test and analysis results showed that the initial location of crack at connecting region was basically equal probability of randomly generated. Residual strength of structure decreased originating from the combined effect of multiple-site crack. It caused the acceleration and competition effects of crack initiation. Connecting region failure finally occurred since the propagation and coalescence of main crack which acquired the competition advantage. The main crack propagation curves of damage tolerance analysis and experiments had the same trend, but the calculation of the crack propagation life was less than the test results.