Abstract:To deal with the problem of aerodynamic and stealth integrated optimization of flywing UAV,A multi-objective optimization study on aerodynamic and stealth of the flywing UAV is carried out which based on the deformation of surface. The FFD parametric method is used to parameterize the wing surface; CFD calculation based on RANS equations is used to analyze the aerodynamic performance of the flywing UAV, large element physical optical method and uniform theory of diffraction are used to calculate RCS of the flywing UAV; And ASMOPSO algorithm with the Kriging surrogate model which based on the expect hyper-volume improvement infill criterion is adopted for integrated optimization design. The results of flywing UAV aerodynamic and stealth integrated optimization exhibit considerable improvement.

Abstract:The high resolution numerical simulation of rotor/wingbody interaction flowfield in hover is crucial for the accurate prediction of aerodynamic performance of the tiltrotor aircraft. The study of interaction flowfield high resolution numerical simulation is the important issues of helicopter aerodynamics. Based on the moving-embedded grid technique, a CFD simulation method for predicting unsteady flowfield is established. Reynolds-averaged Navier-Stokes(RANS) equations are used as governing equations and Spalart-Allmaras turbulence model is employed, implicit LU-SGS scheme is adopted. On this basis, the unsteady interaction flowfield of the rotor/wingbody are investigated in deep research, and the special phenomenon 'fountain effect' is simulated, the results indicate that the total thrust loss is about 16.6% as compared to the isolated rotor. Furthermore, it studies the different preset flaps/ailerons affect on decreasing rotor/wingbody aerodynamic interference. The results show that the lowest aerodynamic interference presents the preset flaps/ailerons angle 45 degree. In the preset angle of 45 degree, the total thrust loss reduces to 13.8% from 16.6%.

Abstract:Aiming at the problem of big drag during takeoff for seaplane, a hydrofoil seaplane with deflectable wings is proposed. The hydrodynamic lift generated by deflectable wing cutting the water surface during takeoff is big enough to lift the aircraft off the water surface. The deflectable wing can deflect the angle according to flight conditions during the flight phase. Aerodynamic and hydrodynamic coupling solutions and dynamic equilibrium equations are used to calculate the hydrodynamic performance for hydrofoil seaplane, and the aerodynamic characteristics of air cruise are analyzed. At the same time, the calculation of the same size double-float seaplane is carried out, and the hydrodynamic and aerodynamic characteristics for two configurations were compared. The numerical results show that the peak value of total drag for double-float seaplane is about 1.97 times of that of the deflection wing for hydrofoil seaplane during takeoff. Aerodynamic performance of deflecting wing with 0° deflection angle is optimal and the drag is lower than that of double-float seaplane during flight, which proves that the deflection wing layout of hydrofoil seaplane can effectively improve the hydrodynamic and aerodynamic performance for seaplane.

Abstract:Stealth technology is an important technical means to improve the penetration capability of cruise missiles. In order to analyze the influence of shaping stealth on the electromagnetic scattering characteristics of cruise missiles, the electromagnetic models of stealth and conventional cruise missiles were established, and the distribution of RCS curves for shaping stealth, frequency and pitch angle response characteristics were studied based on Physical Optics method and RCS reduction value. The results show that shaping stealth could greatly reduce scattering characteristics in nose and rear direction, it also could change the peak position of RCS scattering and make the curve converge inward in nose and rear direction. And with the frequency increasing, the mean values and reduction values oscillate respectively around -32 dBsm and 25 dB, the RCS mean values decrease and reduction values increase in the other angular domains. While the scattering characteristics is not affected with small variation of pitch angle, and the RCS mean values and reduction values in every angular domains oscillate, the reduction mean in nose direction is about 35 dB, and the maximum value exists in the pitch angle of 0 degrees.

Abstract:In this paper, the numerical simulation models of composite structural damage under low velocity impact are classified and evaluated. The low-velocity impact model is composed of two kinds of sub-models: the impact process model and the material damage evolution model. The key elements of each type of model and their processing methods are listed. The commonly used combinations are collected and reviewed, and six simulation models with high frequency in the literatures are listed. The numerical evaluation of two examples with the listed six models was completed, and the results show that for orthogonal laminated plates, the damage shapes and areas given by the six models can be predicted accurately, but for the angle-ply laminated plate, the delamination damage morphology achieved by the model of Puck criterion, considering shear nonlinearity and based energy release rate is closer to the experimental results.

Abstract:In the field of civil aircraft maintenance, the formulation of special event tasks has always been the focus of civil aircraft maintenance manual development. Based on design experience and damage and special event analysis method on S3000L and through detailed analysis and technical tailoring and supplement, the concept of Effect Rating was first given. The technical parameters and analysis methods were established. The special events analysis theories and methods were set up for domestic civil aircraft. The given analysis showed that the theory and analysis method were reasonable and reliable. Some references were given for compiling the Chapter 05 of AMM of domestic civil main aircraft manufacturer.

Abstract:Aiming at the problem that maintenance support capability in aviation equipment maintenance support is difficult to meet the requirement of maintenance support, a new optimization model of aviation equipment maintenance support process is proposed based on Markov decision process and graphical evaluation review technology. Firstly, taking the total maintenance time as the objective function with decision nodes embedded in the GERT network, the MDP-GERT network model of aviation equipment maintenance support process is constructed. Then, by using the strategy iteration and Monte Carlo simulation technology, solving method of the model is given. Finally, the optimization procedure and estimated time of the nitrogen filling process of several aircrafts are obtained through a case study, which verified the feasibility and effectiveness of the model and algorithm. The results show that this model can effectively provide decision support for shortening maintenance support time and improving maintenance support efficiency by optimizing maintenance process.

Abstract:The detection and alarm of air threat situation is the key to the early warning for UAV flight collision avoidance. For this reason, a detection and alarm method of air threat situation based on track prediction is proposed for UAV collision avoidance. In the method, firstly, the sliding window polynomial fitting method is used to dynamically predict the track of the intruder. Then, on the basis of the track prediction, using the flight information of UAV and intruder, the dynamic collision avoidance zone of UAV is established to the intruder. Finally, combined with static protection zone principle, the detection and alarm for flight conflict trend, nearSmidairScollision trend and flight collision trend between UAV and intruder is carried out in a specific flight scenario. Simulation results validate the effectiveness of the proposed method and the feasibility of application in the early warning for UAV flight collision avoidance.

Abstract:In order to effectively control the theater airspace for ensuring the safe, efficient and orderly operation of aviation military transportation activities, the SUMApHMP mathematical model is constructed for the planning of Transit Corridor (TC) basic network without considering the restricted airspace, and a hybrid taboo search algorithm combined with Floyd shortest path algorithm is proposed for solving the model, and then TC basic network without considering the restricted airspace is designed according to the solution result of SUMApHMP. The hybrid taboo search algorithm is tested by flight flow matrix and distance matrix between 10 airports in the air battlefield, and the result obtained by the proposed algorithm is compared with the results optimized using Lingo 9.0 software, validating the feasibility and effectiveness of the algorithm.

Abstract:The composite vertical take-off and landing fixed-wing UAV is a compound UAV with the performance of multi-rotor UAV and fixed-wing UAV. Its innovation lies in clarifying the influence of rotor installation location on the overall performance of UAV.Aiming at the complex aerodynamic interaction between rotor and wing of this kind of UAV.In this paper,the aerodynamic characteristics were analyzed by experiments and Computational Fluid Dynamics(CFD). The installation method of the rotor was determined, and the installation distance of the rotor was further determined based on the level flight status of the UAV. Experiment and numerical simulation results show that the rotor mounted under the wing is more efficient than the rotor mounted above the wing, and the installation distance between the rotor and the wing have a certain influence on the lift of the rotor and the flight performance of the UAV.

Abstract:In order to study the impact damage of helicopter rotor blade under maneuvering condition, in the numerical simulation, the effects of the pulling force, swing moment and shimmy moment of the blade on the impact damage were considered previous. For the rotor blade of a certain type of aircraft, the full - size finite element model was used to simulate the impact.First the profile characteristics of the rotor blade were calculated by using the Fortran program and VABS software. After that, the load analysis model of elastic blade structure was established and the software CAMRIDII was used to calculate the blade load in the state of mobility. On this basis, NASTRAN software was used to conduct transient analysis on the the blade, and the prestress state of the blade under load was simulated. Then DYTRAN software was used to simulate the damage caused by the blade bounce based on the adaptive contact method. The research shows that the damage condition of the blade is non-linear with the impact velocity. In addition to the bullet point, the surrounding structure will also be damaged when the projectile hits. The stiffness matching between the structural parts should be considered in the design of the impeller to achieve the best impact energy absorption effect and the minimum damage area.

Abstract:In order to study the overall scheme design of the medium-small core engine-derived engine, based on the co-working constraints of the core engine’s components and the matching mechanism of high and low pressure system, the influence of the core engine design points on the characteristic parameters of core engine with non-variable geometric area and variable geometric area is studied, the overall performance and size-weight calculation model of the core engine derived engine is established, and the model is used to design the overall scheme design of a big bypass ratio turbofan engine derived from an advanced medium-small core engine. The results show that the mechanical load and thermal load of the core engine can not be simultaneously exerted when the geometrical area of the core engine is not variable. Only when the geometrical area of the core engine is variable, the mechanical load and thermal load of the core engine can be simultaneously exerted. When the pressure ratio of the low-pressure system is 1.8, compared to the core engine with non-variable geometric area, the core engine with variable geometric area increases 16.4% in mass flow, 14.1% in thrust and decreases 1.4% in specific fuel consumption.

Abstract:Because the airborne hydraulic system products will experience the test of low temperature environment in the whole flight envelope,In order to fully verify the reliability of aircraft hydraulic system products under low temperature environment,This paper contrasts various design schemes of low temperature test for aircraft hydraulic system, analyzes three low temperature test schemes. And identifies the types of tests to which they are adapted, Finally, this paper compares the advantages and disadvantages of various schemes. And we propose a new scheme for low temperature test of aircraft hydraulic system with long time, low power consumption and large flow rate. The scheme meets the requirements of the test and achieves the expected effect of high efficiency and energy saving.

Abstract:Establish design assurance system is the most direct embodiment of implmenting airworthiness requirements.Chinese aviation industries are mainly dedicated on military aircraft，lack of experience in civil aviation research and development，lack of understanding of how to establish design assurance system and implement design assurance system.This paper describs airworthiness management mode at home and abroad ,design assurance system requirments and the necessity of establishing design assurance system. This paper expounds the contents of learning comprehension,comparative analysis,document implementation and continuous improvement，and puts forward the methods and ideas of establishing design assurance system。

Abstract:Electric braking technology is an important development trend of aircraft braking system which is a key function subsystem to ensure safety of aircraft during taking-off and landing, it is also an important component of More Electric aircraft. Comparing with traditional hydraulic braking system, Electric braking system has obvious advantages of simpler system structure, higher reliability, lower cost, etc. This paper has firstly collected and investigated the development of aircraft electric braking system, presented the characteristics and differences among the various international electric braking technologies； And then, according to the test results and analysis of Electric braking specimens, the key technique has been specially analyzed at the same time, which provides the relevant references to the research of our domestic electric braking method. Finally, according to our own specialty and practice, the current situation of the domestic electric braking development was also considered and summarized.

Abstract:In the case of a certain aircraft’s engine lubricating oil’s temperature drop is insufficient after turning on the lubricating oil heat diffusion ejector (hereinafter referred to as the ejector) under the condition of engine idling on ground in the hot weather, a reasonable flow analysis and relevant calculation method of ejector performance is given to solve this problem. Based on N-S equations and k-epsilon turbulence model, lubricating oil’s temperature drop before/after ejector under severe conditions is calculated in this paper. The results of the on-board ground test show that the calculation method is reasonable and numerical simulation results are consistent with the test results, which meets the requirements of general engineering calculations and provides a theoretical basis for the performance of an ejector. This paper also gives the method of performance improvement of an ejector based on the calculation.

Abstract:In order to effectively capture the flame propagation rule in the annular combustor and clarify its ignition mechanism of joint flame, the whole ignition process of the combustor was recorded on the TurboCombo made by Zhejiang University with the help of a high-speed camera to carry out visual experimental research. This paper mainly introduced the research on ignition mechanism of three configurations(direct-injection annular combustor, swirling-injection annular combustor, and direct-injection annular combustor with turbine guide blades), and analyzed the characteristics of the process of flame propagation, the process of flame combination under the influence of circumferential velocity’s component because of the swirling injectors, the effect on circumferential ignition process ignition time due to the turbine guide blades. The results show that the high-speed visual measurement can track the whole ignition process in the annular combustion, which is helpful to clarify the ignition mechanism of flame joint in the annular combustion chamber. This study is helpful to the analysis of the high altitude ignition performance of APU and other aero-engines.

Abstract:Navigation database can be used for navigation calculation and automatic tuning management of navigation platform, etc. It is necessary to flight management system data sources. In order to effectively improve the efficiency of the use, update and maintenance of the onboard navigation database, greatly reduce the workload of the relevant staff, the fast parsing and generating method of airborne navigation database based on relation model is proposed. Modeling a large number of data objects contained in the ARINC424 protocol to define logical relationships and constrains between objects in the protocol, and optimizing the data structure, establishing a cross-reference relationship between the data through the intermediate relationship table, thereby fast parsing and generating of the database is realizing. The test results show that the method can effectively improve the efficiency of data query, reduce the time consumption of data parsing and generating, and make the database performance better.

Abstract:This paper is aimed at studying changing trend of each performance parameter of a certain type of fan in the airliner ventilation system under the condition of variable flow rate. The parameters of fan efficiency, pressure rise, power, static pressure distribution on blade surface and the vortex structure in flow field were obtained by CFX numerical simulation. The calculation and analysis show that the total pressure efficiency increases with the increase of flow rate in a certain range, and the efficiency decreases sharply when the flow rate reaches a certain value. In addition, the change of flow rate leads to the change of static pressure on the blade surface and aerodynamic force on the fan. At low flow rate, the aerodynamic force on the impeller has a lowest point. The vortex structure in the flow field also varies with the flow rate in the give range, which is mainly due to the change of the attack angle caused by the flow rate.

Abstract:In this paper, the finite element analysis and calculation methods for compensating displacement fatigue and durable vibration fatigue of Pipeline Compensator are research. By comparing and analyzing the calculation results of finite element simulation and traditional engineering calculation method for a certain type of pipeline compensator, the finite element calculation method for compensating displacement fatigue of pipeline compensator is studied, and the finite element calculation process of durable vibration life is explored. The results are compared with test data to verify the calculation accuracy of its design method. The results show that, the accuracy of the finite element method is better than the engineering design method in calculating the displacement fatigue life. And the finite element method can give the definite distribution of the vibration stress and predict the vibration life, which is better than the engineering design method, which can only provide the natural vibration frequency of compensator, vibration stress and life cannot be defined.