Abstract:Numerical simulation was carried out to investigate the film cooling mechanism of the crescent-shaped block & plasma actuator structure. With CFD method, flow field characteristics, temperature characteristics and cooling effectiveness were analyzed for different film cooling structures: the common circle-hole, crescent-shaped block and plasma actuator film cooling structure. The results show that in circle-hole film cooling structure, counter-rotating vortex pair(CRVP), which lifted the cooling flow and entrain the hot flow, was formed, therefore the cooling effectiveness was the lowest. In the plasma actuator structures and crescent-shaped block structures, anti-CRVP, which restrained the scale and strength of CRVP, was formed. Compared to that with common circle-hole cooling structure, the film cooling effectiveness is improved a lot both in lateral and streamwise. In the crescent-shaped block & plasma actuator structure, the anti-CRVP reached its maximum, therefore significantly improving cooling effectiveness in the area between the holes and generating the best cooling performance.

Abstract:The method solved three-dimensional compressible RANS equations on a point-to-point multi-block structured grid was employed in this paper. Firstly, the DLR-F11 standard model used in the 2nd AIAA high lift prediction workshop (HiLiftPW-Ⅱ) was simulated to validate the reliability of the research method, the results showed that the computational predictions agreed well with experimental, so that the research method could be employed to predict flow field of a complex civil transport aircraft configuration with high lift device. Secondly, we investigated the effects of engine failure on longitudinal aerodynamic characteristics of a civil transport aircraft. The results shown that engine failure not only made drag coefficient increase obviously, but also affected lift coefficient, pitching moment and stall characteristics adversely.

Abstract:The longitudinal moment has an big influence on the stability and safety of the plane. During the research of Wing-hung and Low-HTP(horizontal tail plane) airplane the longitudinal moment stability declines along the lift increases. the HTP is an principal part which provides the longitudinal moment and the longitudinal characteristics of the whole plane is changing due to the HTP. The seven-hole probe is carried out to measure the dynamic press loss and down-wash angle of the HTP to find the reason. Results show that the loss of the dynamic press of the HTP at the angle which is before the maximum lift is bigger than original pressure. The test results are agreed with the calculated ones, and it could be used to optimize aerodynamic characteristics.

Abstract:The aerodynamic characteristics of a low speed unmanned aerial vehicle (UAV) with delta wing configuration are studied by solving Reynolds averaged Navior-Stokes (RANS) equations. The UAV adopts 58° sweptback angle and NACA 6-sery symmetric airfoil section, with aspect ratio of 1.7. The maximum lift coefficient of the aircraft suffers large loss due to the tailless configuration, dropping from 0.62 to 0.48. The relative high aspect ratio based on wetted area ensures reasonable lift-to-drag ratio at smaller lift coefficient, and for typical lift coefficient 0.2 the value is 7.7. With increasing lift coefficient vortex flow structure emerges above the wing as well as the increased trim drag, which decrease the lift-to-drag ratio rapidly. Good longitudinal stability is maintained up to angle of attack (AOA) of 40°, as well as the elevator efficiency. The flow field study reveals that when the AOA is less than 15° the flow is attached to the surface due to the blunt leading edge, which results in higher leading-edge suction, less cross flow on the wing and the improved lift-to-drag ratio. When the AOA is increased above 15°the vortex flow pattern is dominant, which prevents large scale flow separation within the AOA range up to 40°, and maintains the elevator efficiency at the same time. The delta wing with blunt leading edge boasts both high aerodynamic efficiency at lower AOAs and good stability and control at higher AOAs, and has the potential of application for aircrafts of low speed, compact arrangement.

Abstract:A new structural optimization method, which is based on subset simulation optimization (SSO) and the Lagrangian multiplier method, is proposed to solve structural optimization problems under constraints in this paper. The Lagrangian multiplier method is used to handle multiple constraints. Then, SSO is used to solve the transformed unconstrained problem and search for the global optimum. In order to guarantee the robustness of convergence, the updating method of penalty factor is modified for this purpose. The accuracy, robustness and efficiency of the proposed method are demonstrated by two examples. The optimization results of proposed method are compared with those obtained by other optimization methods available in the literature. It indicates that the proposed method has excellent performance on searching for the global optimum.

Abstract:As the petri net modeling has good visibility and excellent dynamic expressiveness, the paper introduces a methodology of utilizing Petri Net to perform reliability modeling on complex system. Through simulating the formed Petri Net model of the complex system by means of the Monte Carlo Simulation，which has formed a whole theory on reliability analyze, and the computation results can be required finally. Eventually, the case of wire flight control system is applied, the simulated result of which proves the validity and accuracy of the above methodology. Thus, the reliability analyze methodology based on Petri Nets can be applied to the complex aircraft system efficiently.

Abstract:In a high altitude airship propeller system, at present, adopting the technology of variable pitch increases the weight and consumes more energy, this paper designed a kind of centrifugal hammer pitch-controlled system based on the centrifugal force , analyzed the working principle of the mechanism, and Kinematics and dynamics simulation analysis are carried out using the ADAMS software. The simulation result shows that when the propeller speed was changed, this system can accomplish the functions of variable pitch propeller, and verify the feasibility of the mechanism. According to the simulation results, apply parametric modeling of centrifugal hammer, establish a constraint equation and make the pitch Angle of optimization as the objective function, optimize the space position of the centrifugal hammer, the optimization results show that 48 degrees of centrifugal hammer installation Angle has the best effect of variable pitch for this platforms.

Abstract:Based on the deep understanding and analysis of the windshield bird-strike airworthiness requirements described in CCAR-25, as well as the engineering experience in a specific civil aircraft type, a detailed description of satisfying bird-strike airworthiness requirements in windshield design process is given. In the last, a set of feasible windshield resistance of bird-strike verification methods which satisfies the corresponding requirements is summarized, and a suggestion about the substantiation of MA700, a new airplane, was given.

Abstract:A simulation analysis method of milling process has been proposed to achieve the prediction of machining deformation of curved thin-walled structures. The regression equation of cutting force are ??obtained by milling experiments under a series of different combinations of cutting parameters to provide the basis for the cutting force loading of simulation test. By using python language for secondary development of Abaqus simulation software, combined with the “model change” technology and three kinds of tool path，milling simulation analysis have been carried on for the machining deformation of curved thin-walled structure. The results indicate that: the deformation of stepped Symmetrically tool path has the minimum amount, and the amount of deformation of unilateral tool path pattern is much larger than two kinds of Symmetrically tool path , With the reduced height of the side walls, the difference decreases, and at the bottom, substantially the same amount of deformation obtained. Finally, The reliability of the simulation analysis milling experiments is verified by milling experiment.

Abstract:Engineering Change classification is an important part of configuration control, in order to meet the increasingly prominent fine engineering change management needs, reduce engineering change classification dependent on human judgment, the introduction of the new classification and management of a commercial aircraft engineering technology research classification model and change management strategy, through the analysis of commercial aircraft development process engineering changes characteristic analysis of engineering changes influence the composition of factors, from the "importance", "urgency" and "complexity" three dimensions influence on engineering changes were portrayed, to build commercial aircraft change impact assessment index system, an integrated fuzzy evaluation Party and coordinate mapping method for constructing commercial aircraft to change the classification model. And eight classification given closely related aircraft based change management policies and procedures to achieve the fine engineering change management. Finally, a typical commercial aircraft company engineering changes, for example, discussed and validated classification model and change management strategies.

Abstract:In order to improve the accuracy of turbulence flow simulations, the k-kL two-equation turbulence model constructed by Abdol-Hamid is applied to close RANS equations and assessed. In this paper, a modification to the upper limit in von Karman length scale is proposed. Some factors effecting simulation accuracy are also discussed. A number of test cases including flat plate case, airfoil case and backward facing step case are run to demonstrate the accuracy of this model, its capability to resolve important flow features and grid convergence. Test results show that this turbulence model is superior or at least comparable to other two-equation turbulence models in simulating either attached or separated turbulent flows.

Abstract:A local grid deformation method based on TFI(Transfinite Interpolation) was developed in this paper. This method could be employed to solve complex flow with other dynamic grid methods because it is different from other global grid deformation methods while it can limit the deformation in special zone without any influence on grids of other zone. For an airfoil NACA0012 with a flap, numerical simulations of pitching oscillations were conducted, and computational results agrees well with experimental results. Then it is concluded that the method developed in this paper is variable for flow solutions of complex geometries.

Abstract:Fuel burn is one of the most important parameters in judging the economical efficiency of airplanes. Based on the range equation，main ways to reduce the fuel consumption of airplane have been discussed in this paper. Under the background of conceptual design of an airplane, influence studies of cruise speed, cruise altitude and aspect ratio of wing on the block fuel and the maximum take-off weight (MTOW) have been carried out on the premise of little change in the general layout. According to the findings, general layout optimization and certain developments have been applied to the initial design, and the changes of block fuel, operational empty weight (OEW) and MTOW have been analyzed during the developments. The results indicate that the optimization design brings a 3.92% decrease in the block fuel and a 100 kg reduction in MTOW during the same design range.

Abstract:Engineers devote themselves to reduce the weight of structures and to improve their performance. The Thrust-Weight Ratio and Weight-Factor of the aircrafts are highly improved because of widely use of composite material. Based on the requirements of development of aerospace and aviation industry, the thesis is concentrated on the investigation of composite door structure progressive design and analysis. And the optimum design of composite plate and shell structure is studied. Based on composite material door structure of a aircraft, the FEM is built and carried out by using of Nastran & Patran. The progressive optimization is finished by Hypersizer. The author obtains the optimum results according to the design requirements. The parameters of cross section, angle of each plies and stacking sequence are calculated. Methods of establishment of FEM and procedure of progressive optimization are summarized. According to the results of analysis, after the optimization, the mass of structure decreases and the structure meets the required design target.

Abstract:In order to study the dynamic performance of tiltrotor aircraft nacelle tilting mechanism during nacelle turning from wing aircraft model to helicopter model, based on the force and kinematic analysis of nacelle tilting mechanism, the nacelle tilting mechanism multi-body dynamic simulation model was established on the LMS Motion software platform, defined every components property of nacelle tilting mechanism, created joints between the components, defined motion drives, created external forces and torques to simulate real working condition, to obtain and analyze the major kinematic parameters curves of nacelle and the interaction forces between nacelle and screw shaft. The results can indicate: With the increase of nacelle rotation angle, the interaction force between nacelle and screw shaft decreases then increases, the interaction force between nacelle and wing increases.

Abstract:Engine installation design is an important aircraft design work, engine installation design of fighters is especially important and the design tasks are highly complicated. The authors of the article collected large number of references, studied and anylased engine installation design exsamples of modern fighters, performed inducting and summarizing sysmetically. The purposes of the authors are to provide references to field colleagues. The article overviewed engine installation design of fighter, summarized installation system design of modern afterburning turbofan engines. Engine installation design examples of 8 types of modern fighters were dissected, the similarities and differences between these engine installation designs were compared, installation forms and structure details of engine mounting etc. are included. The above-mentioned dissecting and comparing are helpful for domestic colleagues to understand engine installation design, and to gain excellent design solutions.

Abstract:In this paper, the research status of risk assessment method has been analyzed for civil aircraft operating. The method ofprobabilistic risk assessment inaircraft has been established based on the FMEA and FTA. Three type methods have been presented to calculate the fleet risk: The probability forecast of fleet has been developed by maintenance plan and historical data. The fleet risk model has been established at random failures period.Uncorrected fleet risk assessment method andthe case have been establishedat wear-out period. The fleet risk trends, influencing factors as well as risk value may occur have been given.Compared withfour methods, the suitable operation risk methods for civil aircraft and fleet have been established in variable states over the remaining life of the fleet. Through these methods, the risk of civil aircraft would be reduced effectively during operation.

Abstract:No matter how high is the initial design and reliability level of the aircraft, once entry into service, proper use and maintenance is the base to maintain the level of its inherent design level and reliability. It is the responsibility of the manufacturer to develop a detailed and correct maintenance program. The development of domestic civil aircraft started late, and there are not many types and quantities of domestic aircrafts in service. The manufacturers have less experience in developing maintenance program. This paper studies the widely used international MSG-3 maintenance task analysis method, and the development and background of MSG-3 has been described as well as the application in several types of domestic civil aircraft. This paper has studied the content of MSG-3 in details，including the methods of aircraft systems/powerplant maintenance task analysis，structural and zonal inspection task analysis，and the procedure of developing and optimizing the maintenance program. Finally the author generalizes the problem and solution in developing the maintenance program of domestic civil aircraft manufacturers. This research has a practical reference value in developing the maintenance program for civil aircraft manufacturers and evaluating the maintenance program for civil aviation authorities.