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2016 Vol. 42, No. 1

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Volume 42 Issue12016
2016 Year 42 Volume 1 Issue E-journal
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A new composite multi-field-of-view optical sensor and its navigation method
JIANG Jie, ZHENG Jiayi, LING Sirui
2016, 42(1): 1-7. doi: 10.13700/j.bh.1001-5965.2015.0068
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According to the filtering method and navigation precision, the layout of multi-field-of-view of a composite optical sensor with four mirrors was presented. A kind of high-precision method of autonomous navigation based on the sensor was given. The method was to simultaneously measure the earth, navigational star and refraction star via the four mirrors of the sensor, and autonomous navigation for satellite was realized through geometrical position relation among satellite, the earth, and star direction. Also the measurement acquisitions in autonomous celestial navigation simulation were studied. Five practicable working modes of composite multi-field-of-view optical sensor are proposed. A simulation model was set up using of Kalman filtering algorithm, and the system simulation was made using simulative data at the basic of an earth-pointing satellite with a certain orbit altitude. Based on the simulation results of all five working modes, the observing mode of double directly sensing horizon combined with single stellar horizon atmospheric refraction provides the highest navigation accuracy. The position accuracy can reach order of 10 m.
Generalized linear regression model based on functional data analysis
WANG Huiwen, HUANG Lele, WANG Siyang
2016, 42(1): 8-12. doi: 10.13700/j.bh.1001-5965.2015.0078
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Functional linear regression model has captured much attention in functional data analysis. By tools in semiparametric and nonparametric statistics, it is proposed to estimate the coefficients in generalized linear regression models with both multivariate scalar covariates and functional covariates. In this framework, the theory of generalized linear model is introduced, and the response variable is not required to be continuous random variable and may be discrete or attribute data, which widely broadens the application of functional linear model by solving the regression problem of predictors with mixed types of multivariate data and functional data. Besides, Logistic regression and Possion regression corresponding to categorical or discrete responses were emphasized, and a reweight algorithm for maximizing the log likelihood function was provided. In the procedure of estimation, functional principal component analysis and B spline were utilized, and the criterion to select the number of basis functions was suggested. The simulation results show that the proposed estimation and test methods are effective.
UH model considering expansion of soils and its finite element implementation
LUO Ting, ZHANG Panpan, YAO Yangping, LIU Yuemiao, CHEN Liang, CAO Shengfei
2016, 42(1): 13-20. doi: 10.13700/j.bh.1001-5965.2015.0069
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The unified hardening model (UH model) for overconsolidated unsaturated soils is applicable to problems involving unsaturated soils. The wetting behaviors of unsaturated soils in overconsolidated condition can be described more reasonably using this model. It can also describe strain-hardening and softening behaviors of the unsaturated soils better. Based on the UH model for unsaturated soils, a new UH model for bentonite was proposed by considering the expansion of the soil aggregates. With just one more parameter, the proposed model can not only describe the stress-strain behaviors of the bentonite under general loading paths,but also describe the expansion of the bentonite under wetting paths. Based on the secondary development platform of finite element software, the UH model considering the expansion of the bentonite has been implemented. The subroutine was proved to be reasonable through the simulation of the triaxial test and the swelling pressure test using the proposed model.
Electric vehicle energy economy based on braking intention identification
JI Fenzhu, DU Farong, ZHU Wenbo
2016, 42(1): 21-27. doi: 10.13700/j.bh.1001-5965.2015.0031
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Braking energy recovery is a main technology measure for improving the energy economy of the electric vehicle. It is a key point to accurately identify the driving intent for braking energy recovery. The models of braking intention identification for lifting up the accelerating pedal and depressing the braking pedal were respectively established. Braking intention was identified using fuzzy control method. The identification results of driver braking intention were expressed as small-strength brake, middle-strength brake and emergency brake.Two types of energy recovery modes were made up based on the braking intention identification results. The braking force allocation strategy and calculation model were set up based on the economic commission of Europe (ECE) regulations line and I curve. A braking system simulation model was founded in the plate of Cruise and MATLAB/Simulink, and braking energy recovery rate and driving range of the electric vehicle were calculated for different energy recovery modes.The results show that: if energy recovery mode is different, the braking energy recovery rate is different; in a new European driving cycle (NEDC), the energy recovery rate could be improved in the case of recovering the braking energy in the stage of lifting up the accelerating pedal, and this braking energy is set to simulate engine braking in orthodox vehicle; the driving range increased 5.69% in NEDC.
Theory analysis of system instantaneous availability under uniform distribution
YANG Yi, REN Sichao, YU Yongli
2016, 42(1): 28-34. doi: 10.13700/j.bh.1001-5965.2015.0058
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The early volatility of instantaneous availability which belonged to one-unit repairable system was analyzed in theory. Recent research progress on two kinds of availabilities was reported and the importance of research on the instantaneous availability was highlighted. It was respectively discussed that the failure time and repair time of system components obeyed the same as well as different uniform distribution, and then the renewal equation was transformed into piecewise ordinary differential equations or delay differential equations. The analytical expressions of instantaneous availability were obtained from the differential equations by the use of the continuity and initial value. A method was put forward to judge the volatility of instantaneous availability, that is, to judge whether there existed the value of instantaneous availability less than that of the steady-state availability. The method has been proved to be effective, and the conclusion demonstrates that the volatility exists regardless of any parameter combination under uniform distribution. The final simulation results are in good agreement with the theoretical results.
Performance evaluation of fault diagnosis system based on Bayesian network
YU Jinsong, SHEN Lin, TANG Diyin, LIU Hao
2016, 42(1): 35-40. doi: 10.13700/j.bh.1001-5965.2015.0070
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Assessing whether a newly developed fault diagnosis system is effective is an important issue to ensure diagnosis system performance.Due to the requirement of evaluating the performance of the fault diagnosis system based on Bayesian network (BN), an evaluation method using a modified binomial distribution was developed, considering the real distribution of diagnosis results. The parameters of the modified binomial distribution were estimated using training data during the training process of fault diagnosis system, and both diagnosis accuracy and confidence interval of a diagnostic system could be calculated simultaneously by this evaluation method. The quantitive evaluation indices provided by the proposed evaluation method greatly contributed to the evaluation of acceptability and reliability of a Bayesian network-based diagnosis system, and were of great significance in supporting diagnosis system training. In conclusion, the effectiveness of the proposed evaluation method was validated by an example concerning a fault diagnosis system for the aircraft fuel system.
Parameter estimation method based on beta-likelihood function
WANG Xiaohong, LI Yuxiang, YU Chuang, WANG Lizhi
2016, 42(1): 41-46. doi: 10.13700/j.bh.1001-5965.2015.0071
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Distribution parameter estimation is a common method which is used in reliability data analysis to study the change rules of product reliability and evaluate the reliability level of the product. Learning from the beta distribution which is used to describe the product reliability in life test and evaluate the reasonable degree of estimator of reliability, we thought that reliability estimator is more reasonable if its probability density function is bigger in the beta distribution, raised a beta likelihood function to evaluate the reasonable level of the estimate in reliability analysis, discussed the distribution parameter estimation method when using this beta likelihood function, verified the method by simulation under the exponential distribution case and Weibull distribution case, and gave the corresponding application examples. The estimation method is based on abundant theoretic evidence, and is suitable for all kinds of distribution types. From the application examples, we know that estimation results are reasonable and believable. Maximum likelihood estimation method takes the samples' probability density function in the distribution to be estimated as the evaluation criteria, while, on the contrast, our method takes the cumulative incidence estimator as the evaluation criteria. So it is more applicable in the research on reliability and survival problems when concerning the cumulative occurrences.
Dynamic analysis of air system with fast transients in shaft failure event
LIU Chuankai, LI Yuanyuan, LI Yanru, JIANG Hongchao, DING Shuiting
2016, 42(1): 47-53. doi: 10.13700/j.bh.1001-5965.2015.0064
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This study established the governing equations and the corresponding modularized simulation model for air system in rapid transients. The modularized model consists of four kinds of basic components that constitute the transient air system network: pressure vessels, nodes, ducts, and throttles. The validation of the modular components and their assemblies against published data has been demonstrated to be successful. The model is proved to be able to handle volume packing effects and flow inertia effects that account for the main contributions to fast transient scenarios. On this basis, the model is utilized to analyze the flow evolution of air system in aero engine high pressure turbine (HPT) shaft failure event. The results show that the shaft failure can lead to complex dynamic response in the air system and the subsequent reversal of the turbine disk endload. The model established in this study successfully predicts the air system transient response within millisecond time scales, which provides an effective approach to gain insight into the complex transient mechanism of aero engine air system.
Effects of W-doping on formation energy of oxygen vacancy in TiO2
ZHU Linggang, ZHOU Jian, SUN Zhimei
2016, 42(1): 54-58. doi: 10.13700/j.bh.1001-5965.2015.0015
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First-principles calculations were used to study the influence of W-doping on the formation energy of oxygen vacancy in rutile TiO2 oxide, in order to explore the possible effects on the corrosion resistance of Ti alloys by the addition of W which is normally used to strengthen the matrix. It was found that W can increase the formation energy of neighboring oxygen vacancy by nearly 0.7 eV, meaning that it can inhibit the generation of oxygen vacancy and the penetration of oxygen into the matrix effectively, which is beneficial for the oxidation resistance of Ti alloys. For the oxygen-vacancy pairs with different configurations, W can also increase their formation energy, by only 0.2 eV per vacancy; therefore, the positive effects of W will be weakened with the accumulation of oxygen vacancies and the acceleration of the oxidation process. Analysis on the electronic density of states shows that for oxygen-vacancy pairs with various configurations, the energy levels of the states of the unbounded electrons are different, which eventually lead to various formation energies.
Structure design and motion mode analysis of a six wheel-legged robot
XU Kun, ZHENG Yi, DING Xilun
2016, 42(1): 59-71. doi: 10.13700/j.bh.1001-5965.2015.0021
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The research of hybrid locomotion robot has become one of the hottest spots of mobile robots. Wheel-legged robot which combines the advantages of wheeled robot and legged robot can be better adapted to complex environment. A new combination between wheels and legs is proposed and a new circumferential symmetry wheel-legged robot is designed. It can transit its locomotion mode by changing its configuration. Meanwhile, it reduces mechanism complication and avoids the fray of wheels while they are used as feet in legged motion mode. Because of its special structure, four typical "3+3" tripod gaits and the equivalent mechanisms in different walking gaits processes are presented and transition between them is analyzed. The forward and inverse kinematics models of single leg are built. Based on its structure, planning of motion mode transition from wheeled motion mode to legged motion mode and from legged motion mode to wheeled motion mode is given and simulated in software. Its wheeled motion mode and steering problem are analyzed and illustrated,and four steering models are built. Some tests with wheel-legged robot prototype are made to verify its ability of locomotion both in legged mode and wheeled mode and its capability of transition between different motion modes.
Chordwise attenuation of heat transfer performance on inner surface of hot-air anti-icing system
BU Xueqin, PENG Long, LIN Guiping, ZHOU Ying
2016, 42(1): 72-78. doi: 10.13700/j.bh.1001-5965.2015.0065
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The local heat transfer performance on the inner surface of the airfoil leading in jet impingement hot-air anti-icing system is experimentally studied through inverse flux technique using a piccolo which has 3 rows of orifices chordwisely, among which the middle orifice is exactly facing the stagnation point. The jet Reynolds number, Rej, the relative piccolo tube to surface distance, Zn/d, and the relative chordwise arc length in the jet impingement zone, r/d, are studied as the factors of local jet impingement heat transfer performance. The range of Rej, Zn/d and r/d are 2.5×104-1×105, 1.736-27.5, 13.21-61.5, respectively. The local heat transfer performance curve looks like a bell, meaning it is high around the stagnation point and decreases as the position goes aside. This curve consists of 3 parts: the stable zone, the decline zone and the ending zone.Stable zone is only dependent on r/d. All of Rej, Zn/d and r/d significantly affect the declining rate of decline zone. However, the amount of decrease is nearly independent of r/d. The experimental correlation equation of the heat transfer performance attenuation under the circumstances of applying this kind of piccolo structure is developed, which would be helpful for future design of anti-icing system and evaluation of its thermal performance.
Trajectory optimization method of aircraft endurance flight based upon control surface trimming
LIU Fan, WANG Lixin, CAI Weimin
2016, 42(1): 79-86. doi: 10.13700/j.bh.1001-5965.2015.0067
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Besides providing balancing moment for stable flight, control surface deflection will change the lift-drag ratio of the airplane, which affects the endurance performance of the airplane. Based on the traditional flight trajectory optimization which assumes that the airplane is a particle, the effects of lift-drag characteristic on aircraft endurance performance are analyzed. Increasing lift-drag ratio at climb segment, cruise segment and earlier descent segment, and decreasing lift-drag ratio at later descent segment will improve the endurance performance of the airplane. In order to obtain the optimum flight trajectory and range closer to the actual potential of airplane, a trajectory optimization method of aircraft endurance flight based upon control surface trimming is proposed. Through this method, the optimum combined trimming mode of control surfaces can be obtained for multi-control surface airplane. The optimization result of a type of aircraft indicates that, compared to single trimming modes of control surface, the optimum combined trimming mode increases the total range by 7.5% at most for the example airplane.
Stability analysis and optimization for pneumatic cabin pressure regulating system
ZHENG Xinhua, XIE Lili, REN Junxue
2016, 42(1): 87-93. doi: 10.13700/j.bh.1001-5965.2015.0020
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Pressure oscillation arises in cabin of aircraft equipped with the considered pressure regulating system. To solve the problem, the scheme of cabin pressure regulating system was introduced and analyzed. The system in differential pressure flight phase is simplified according to actual components participating in the pressure modulating. The simplified system was taken as an example for stability analysis. The nonlinearity of the system was analyzed in details. The describing function was obtained and the negative inverse describing function curve was plotted. The charging and discharging dynamic of hole-container structure was studied, and it was found that the charging and discharging transient was almost same in the condition. Then the transfer function of hole-container structure was built as first-order element, and the similarities and differences between them were pointed out. Describing function method was employed to analyze stability of the system, and a way of achieving stability was proposed. Full-physical simulation result shows that the required stability is achieved by this way.
Global-best guided fuzzy cuckoo search algorithm and its application
QIN Qiang, FENG Yunwen, XUE Xiaofeng
2016, 42(1): 94-100. doi: 10.13700/j.bh.1001-5965.2015.0025
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A global-best guided fuzzy cuckoo search algorithm is proposed to deal with the deficiencies of cuckoo search algorithm, such as poor at exploitation and accuracy, slow convergence, etc. A global-best guided strategy was introduced into the nests update formula to take advantage of the current optimal nest location information when producing new nest location in order to maintain the diversity of the nests and increase the algorithm's exploitation. In addition, the proposed method utilize fuzzy set theory to adjust the two main coefficients, one is search step, the other is the fraction of worst nests, and is thereby able to improve the accuracy and the global convergence. The performance of the proposed algorithm was tested by two classical structural reliability limited state functions and then it was applied to reliability analysis of an aircraft door locking mechanism. Experimental results show that compared with the particle swarm optimization,standard cuckoo search algorithm and improved cuckoo search algorithm, the proposed algorithm enhances the accuracy and the convergence effectively, and it has better optimization results when applied to reliability analysis problems.
Integrated method of knowledge and data for quantitative reliability modeling
HAO Zhipeng, ZENG Shengkui, GUO Jianbin, MA Jiming, LI Qilin
2016, 42(1): 101-111. doi: 10.13700/j.bh.1001-5965.2015.0029
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Keys of quantitative reliability design lie in the establishment of the quantitative reliability model. Current modeling methods mainly rely on design staff's knowledge on product failure rules, including failure modes, environmental disturbances, failure mechanisms, etc. However, the inherent finiteness and imperfection of knowledge are bound to bring both model error and input uncertainties to the quantitative reliability model. To address this problem, we proposed a knowledge-and-data integrated Bayesian modeling method to develop the quantitative reliability model, quantifying the model error and input uncertainties. First of all, the tasks of the knowledge-and-data integrated modeling of the quantitative reliability model were explained, and the corresponding framework was established. Then the principle of Bayesian integration of knowledge and data was clarified. After that, the general method of Bayesian integration of knowledge and data was proposed, and two specific Bayesian integration methods for both performance fluctuation and degradation data were addressed respectively. Finally, the effectiveness and feasibility of the proposed method were illustrated by a case of an airborne axial piston pump.
Design and simulation of controllable aircraft main landing gear operating actuator
HUANG Chen, JIA Yuhong
2016, 42(1): 112-119. doi: 10.13700/j.bh.1001-5965.2015.0034
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Conventional aircraft landing gear hydraulic system has little controllability during operation. Landing gear hydraulic operating actuator designed to operate under maximum aircraft load factor during landing gear retraction may lead to more serious impact under common load factors. Conceptual design of a controllable operating actuator applied to aircraft main landing gear was raised, which employs 2-way proportional throttle valves to adjust hydraulic damping according to load factor. Multibody model of landing gear retracting device and hydraulic model of operating actuator were combined in main landing gear retraction simulation under different load factors. Controllable design generates lower strut ending speed, actuator back pressure and structural impact compared with conventional design under certain design constrains. Effects of actuator input pressure and damping relation between the input and output throttle valves on simulation results were studied. Improved design of controllable operating actuator was raised, which further lessened maximum actuator load and impact of landing gear retraction by using the effect of inertia force.
Gliding reentry vehicle lateral/directional coupling attitude control strategy
SHI Linan, LI Huifeng, ZHANG Ran
2016, 42(1): 120-129. doi: 10.13700/j.bh.1001-5965.2015.0037
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A lateral/directional coupling control strategy based on the analysis of coupling characteristics was proposed for a class of under-actuated reusable launch vehicle (RLV) with only two body flaps and strongly coupling phenomena. Several common coupling mechanisms and evasion modes were described, including the inertial coupling, the motion coupling, the Dutch coupling and the control coupling. A rapid roll stability boundary was calculated along a nominal trajectory to limit the angular rate of bank angle command, and aiming at the problem that the existing Dutch-roll forecast formula is not suitable for this aircraft, a criterion of the Dutch-roll motion stabilization was proposed in order to adjust the controller gain in different situations. Based on the analysis of the coupling characteristics, a RLV longitudinal and lateral/directional motion control strategy was designed: elevators were used to trim and control on the longitudinal channel; body flaps and reaction control system (RCS) were used to hybrid control on the lateral/direction channel at low dynamic pressure and at high dynamic pressure body flaps can work alone. The 6 degree of freedom (6-DOF) numerical simulation results have demonstrated the control strategy proposed can track the guidance command well and maximize the using of aerodynamic actuators to reduce the consumption of RCS fuel.
Active disturbance rejection control method on load relief system for launch vehicles
YANG Weiqi, XU Zhi, TANG Shuo, ZHANG Yingying
2016, 42(1): 130-138. doi: 10.13700/j.bh.1001-5965.2015.0051
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Load relief control technology is studied for launch vehicles flying across the strong wind area. First, load relief controllers based on angle of attack feedback and accelerometer feedback were calculated, and limits of these methods were analyzed, thus an improved active disturbance rejection controller (ADRC) based on informed research was introduced into the flight control system. On the one hand, the error which was observed by status observation was introduced into the ADRC loop. On the other hand, by calculating the wind load impact on the control system, it improves the control law in ADRC and proves that aerodynamic load can be restrained by ADRC, and the method to select the gains in governing equation in the improved control law was given. At last, taking a liquid launch vehicle as an example and considering the elastic vibration and sloshing, load relief effect was analyzed with different methods. The simulation results show that after the improved ADRC method is introduced, the flight control system enhances the ability to reject disturbance, and expands the boundary when choosing a gains in the control law. With the disturbance compensation and proposed control law, the effect of the load relief system on the launch vehicle was greatly improved. This method has a great value in engineering application.
Effect of rotor-stator interaction on film-cooling of turbine blade
LI Hongyang, ZHENG Yun
2016, 42(1): 139-146. doi: 10.13700/j.bh.1001-5965.2015.0054
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For the purpose of studying the effect of rotor-stator interaction on film-cooling of turbine blade, the AGTB turbine cascade was chosen to do the research, with which a vane row was assembled. Unsteady numerical simulation was made for the full stage. The cross-section flow field at different instants of time and variation of temperature distribution of the blade over time were analyzed in detail. Furthermore, influence of wake and potential interference on film-cooling of downstream blade was discussed. Conclusions are as follows: the strong potential interference of the vane could change the flow angle of downstream blade in the range of 12°, which has a great influence on cooling jet; both the wake and potential interference could induce cooling jet "uptrend" and increase the mass flow of the cooling air by more than 20%, enhancing instant cooling performance; function time of potential interference was about 1/2 stator period, while that of the wake was about 1/6 stator period, and the potential interference usually performs longer time and has stronger effects than the wake. Affected by the transport effects, variations of cooling performance of the whole blade and flow condition of cooling jet were not synchronous, of which the latency time could be about 1/3 stator period or even longer.
Life up and down method for determining WFD average behavior of aircraft structures
ZHANG Jianping, SHI Xinhong, ZHANG Jianyu, ZHENG Xiaoling
2016, 42(1): 147-151. doi: 10.13700/j.bh.1001-5965.2015.0056
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The widespread fatigue damage (WFD) problem is a serious threat to the integrity and safety of aircraft structures.Evaluation of the WFD average behavior is the base for establishing a limit of validity of the engineering data that supports the structural maintenance program. A life up and down method for evaluating the WFD average behavior of aircraft structures was proposed based on the theory of strength up and down method in fatigue applied statistics. The residual strength test was conducted following the fatigue test with a specified fatigue life level (FLL) to determine whether the residual strength meet the requirement. Taking the mean value of the adjacent two FLL with contrasted results as the FLL could lead to a residual strength equal to the required one. By repeating the tests and statistical analysis of the results, the WFD average behavior could be found out. Test on multiple site damage structure with 5-details was conducted with the proposed method, and a WFD average behavior, with a requested residual strength and a specified loading condition, was provided. The proposed method based on the fatigue reliability can be used both in multiple site damage structures and multiple element damage structures, independent of the specific forms of the structures and the load conditions.
Investigation of mixed convection of supercritical pressure RP-3 in vertical round tube
JIA Zhouxia, XU Guoqiang, WEN Jie, LONG Xiaodong, WANG Yue
2016, 42(1): 152-157. doi: 10.13700/j.bh.1001-5965.2015.0066
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The mixed convection research of supercritical pressure hydrocarbon aviation fuel RP-3 in vertical tube was conducted and the effects of buoyancy and thermophysical properties on convection was investigated. The wall heat fluxes (200-500 kW/m2), inlet pressure (3-5 MPa) and inlet Reynolds number (5 000-10 500) were maintained in the experiments. The study shows that heat transfer impairment occurrs in inlet region for all upward flow conditions due to buoyancy effects, which is not observed in the downward flow. The heat transfer coefficient increases as the fluid bulk temperature increased as a result of comprehensive effects of thermophysical properties. At lower inlet Reynolds number (5 700), the radial velocity profile changes in downward flow conditions leading to heat transfer enhancement due to buoyancy effects. The buoyancy effects are also significant for higher inlet Reynolds number (10 500). The criterion equation (Bo* < 5.6×10-7) failed to evaluate buoyancy effects on hydrocarbon fuel heat transfer.
Analysis of strain in electromagnetic V-shaped bending of 2024-T3 aviation aluminum alloy plate
XIONG Weiren, WANG Wenping, WAN Min, LI Xinjun
2016, 42(1): 158-164. doi: 10.13700/j.bh.1001-5965.2015.0075
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The mechanical properties and service life of parts are influenced by the strain characteristics after metal forming process which causes plastic deformation. Meanwhile, the electromagnetic forming (EMF) gets more attention for the advantage that it can help to overcome the drawback of low formability of aluminum alloys at room temperature by improving the formability. Therefore, the aviation aluminum alloy plate of 2024-T3 was used as the study object. And, the experiments and numerical simulations of V-bending process by both EMF and conventional mechanical method were carried out. The influence of two forming methods on the strain characteristics at the V-shaped corner which is along the longitudinal direction of the specimen was studied. The results show that the tensile strain at the outside of the V-shaped corner of the numerical virtual part formed by EMF is smaller than that formed by mechanical method, and the peak value of tensile strain of actual part formed by EMF is lower by 13.9% as well. In addition, compared with mechanical method, a larger proportion of metal sheet formed by EMF gets involved in the bending deformation.
Analysis of wings effects on locust-like robot air posture
CHEN Kewei, CHEN Diansheng, ZHANG Ziqiang, ZHANG Benguang
2016, 42(1): 165-171. doi: 10.13700/j.bh.1001-5965.2015.0098
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To verify the mechanism that locusts adjust their posture in air by flapping wings asynchronously, the air posture adjustment locust-like robot system has been designed which realized the flapping of wings with the crank-rocker structure. The structure characteristics have been analyzed and the wings flapping model has been established. Then, the forces and torques acting on the wings under different flapping frequencies and different amplitudes have been calculated. The influences on the body with synchronous and asynchronous flapping of wings have also been analyzed. Finally, an experimental platform has been built and a series of experiments have been implemented. Results indicate that synchronous flapping of left and right wings does not induce body posture change greatly while different phases of each side of wings will cause the body swing. Furthermore, different flapping amplitudes will induce the body roll and the higher flapping frequency is,the more obvious the body rolling phenomenon is. The experiments have verified the correctness of the mechanism of locust air posture adjustment by the ways of asynchronous wings motion and have provided the basis for the design of the air posture adjustment locust-like robot.
Experimental analysis on flow past circular cylinder attached to frontal splitter plate
ZHOU Xiao, HU Ye, WANG Jinjun
2016, 42(1): 172-179. doi: 10.13700/j.bh.1001-5965.2015.0053
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Considering the classic circular cylinder flow model, a frontal splitter plate was introduced to explore the influence on the flow past a circular cylinder in a water channel. Particle imaging velocimetry (PIV) was utilized to investigate the flow characteristics of the circular cylinder attached to a splitter plate with two different stiffness (flexible and rigid) respectively at the Reynolds number of Re=1 800. Owing to the bending deformation of the flexible plate's leading point, an additional perturbation results in the generation of vortex on the tip of the plate and even varies the dominant frequency in the wake region.In the downstream of the cylinder, the sizes of reverse flow region in the flexible plate condition and the no-plate condition are similar, while the size of reverse flow region in the rigid plate condition is larger. The experiment results show that the drag force of the circular cylinder could be reduced in a degree by the frontal splitter plate.
Research on fault diagnosis based on multi-signal flow graph and branch-and-bound algorithm
LIANG Shuang, YU Jinsong, TANG Diyin, JIANG Yang
2016, 42(1): 180-186. doi: 10.13700/j.bh.1001-5965.2015.0017
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A complete fault diagnosis method based on multi-signal flow graph and branch-and-bound algorithm was proposed to deal with real-time online fault diagnosis problems. A multi-signal flow graph model was built for the object system and a dependency matrix was generated as diagnostic knowledge. Conflict sets was generated by the dependency matrix and the system observation vector, which was essential in transforming the problem of finding the minimal diagnosis set to a problem of integer programming. A new version of branch-and-bound algorithm was utilized to calculate the optimal solution of the diagnosis by branching, computing lower and upper bounds and pruning the conflict sets. In this way,explosion problem caused by enumeration could be avoided. By applying the proposed approach to a fuel system of aircraft, the efficiency of this method was verified. Diagnostic results by comparing with the existing TEAMS-RT algorithm demonstrate that the proposed method has a higher accuracy in locating the faults. Besides, both single-fault and multi-fault diagnostic problems can be covered and the method is capable of large-scale complex system fault diagnosis.
Influence of side boundary condition on compression performance of aluminum alloys stiffened panels
XU Rongzhang, GUAN Zhidong, JIANG Siyuan
2016, 42(1): 187-192. doi: 10.13700/j.bh.1001-5965.2015.0022
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Engineering aircraft stiffened structure reinforced by a beam or wall panels restriction are simply supported, and high strength aluminum alloys stiffened panels constrained by side boundary will exhibit different compression performance from panels with unsupported side boundary in axial compression. Test and numerical calculation research were conducted to study this phenomenon. Moiré interferometry and strain gauges were used to monitor the buckling and post-buckling process. Based on the software of ABAQUS, a finite element model was developed. Johnson-Cook constitutive model with ductile damage and shear damage was used to study compression performance of panels with different side boundary conditions. The calculated results are coordinated with the tested results very well. The results indicate that all skins of side simply supported panels buckle simultaneously, while only side skins of unsupported panels buckle. Despite the buckling load for unsupported panels is well lower than that for side simply supported panels,the former's ultimate load only almost decreases by 9%.
Combat capability requirement generation of shipborne area air defense based on analytic rules
XU Junfei, XING Changfeng, WU Ling
2016, 42(1): 193-200. doi: 10.13700/j.bh.1001-5965.2015.0038
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Abstract:
First, in order to generate the capability indexes of shipborne in the capability requirement generation process, the threatening task of shipborne is decomposed, a capability index system is built, the analytic rules between the meta tasks and the capability indexes are analyzed. Second, in the background of area air defense of single shipborne ship-to-air missile, the corresponding mathematical models are established according to the steps of operational process, and with relation graph, the capability indexes, including killing zone boundaries, launching zone boundaries, anterior distance and height of airborne early warning aircraft, warning distance, etc., are verified in simulation on the basis of operational requirements and other factors between ourselves and the enemy. Finally, the interval numerical values are produced by analyzing the impact of the required detection distance and speed upon combat capability indexes, which provides a quantitative basis for combat capability requirement generation of shipborne area air defense.
Algorithm for recognizing and constructing rib feature based on constrained Delaunay triangulation
ZHOU Min, ZHENG Guolei, LUO Zhibo, CHEN Shulin
2016, 42(1): 201-210. doi: 10.13700/j.bh.1001-5965.2015.0049
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Abstract:
In order to recognize the rib feature in aircraft structural parts, a recognition and construction algorithm based on the constrained Delaunay triangulation is presented. First, according to the different machining methods between the real bottom plane and the flat rib as well as the similar geometric characters of these two features, the concept of generalized bottom plane is introduced to represent the real bottom plane and the flat rib. Moreover, a representation model of the rib feature is established for further recognition and construction. Second, the constrained Delaunay triangulation method is adopted to decompose the generalized bottom plane, recognize and distinguish it as the flat rib or bottom plane, and then extract the medial axis of the flat rib. Finally, the flat rib is divided as per the medial axis while the declining rib is recognized and constructed as a sub-feature of the generalized bottom plane. The validity and efficiency of this algorithm have been verified through examples.

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