Table of Content

31 January 2014, Volume 35 Issue 1

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Paper

Effect of Ignition Advance Angles on Combustion Process in Natural Gas-fueled Rotary Engine

FAN Bao-wei, PAN Jian-feng , CHEN Rui, LIU Yang-xian, TANG Ai-kun, WANG Qian

2014, 35(1):  1-8.  doi:10.3969/j.issn.1000-1093.2014.01.001

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The calculation models of combustion and turbulent flow are established for a spark-ignition rotary engine in order to realize dynamic simulation of operating process of natural gas-fueled rotary engine. The evolution processes of flow and temperature fields and the propagation process of flame in cylinder are obtained by numerical simulation, and the effects of different ignition advance angles on the flame propagation are analyzed under the same ignition. The results show that the eddy in cylinder can largely accelerate the flame propagation speed. When the spark plug begins to ignite, it is best to be located at the transition region between eddy zone and unidirectional flow. With the motion of rotor, the eddy is extruded and disappears because the volume of combustion chamber decreases. The ignition advance angle should be appropriately increased for making full use of the eddy action time under the constant eddy disappearance moment condition. Under the computational conditions, when the ignition advance angle is 47°, the combustion efficiency and the peak pressure in the cylinder are the highest, and the lower NO_x exhaust is also taken into consideration. This study provides some theoretical guidance for the determination of best ignition advance angles under different working conditions.

Numerical Simulation on Three-dimensional Dynamic Process of Sabot Discarding of APFSDS

HUANG Zhen-gui, CHEN Zhi-hua, GUO Yu-jie

2014, 35(1):  9-17.  doi:10.3969/j.issn.1000-1093.2014.01.002

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The discarding process of armour piercing fin-stabilized discarding sabot (APFSDS) is crucial for its flight stability and lethality. In order to describe the aerodynamic interferences between the projectile and the sabots and the six degree-of-freedom (6DOF) flight trajectories of three sabots with respect to the projectile, the three-dimensional flow field of APFSDS under the action of aerodynamic force and gravity is simulated with the use of the dynamic mesh technique. Based on the governing equations of fluid dynamics and rigid body motion equations of 6 DOF and the variation of flow characteristics during discarding processes and the time history of aerodynamic coefficients of all sabots and projectile are obtained.

Numerical Research on Drag Reduction of Base Bleed in Supersonic Flow

ZHUO Chang-fei, WU Xiao-song, FENG Feng

2014, 35(1):  18-26.  doi:10.3969/j.issn.1000-1093.2014.01.003

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In order to research the drag reduction characteristics of base bleed in supersonic flow, three-dimensional Navier-Stokes equations with chemical reactions are solved by the high-accuracy upwind scheme (AUSMPW+), k-ω SST turbulence model, 8 species/12 reaction kinetics model, and second-order turbulent combustion model. The flow field based on the actual base bleed gas in supersonic flow is numerically simulated by verifying the effectiveness and reliability of the numerical methods. The calculated results show that, with the increase in base bleed parameter, the base pressure ratio increases and then decrease, and finally it tends to increase. When the base bleed parameter is small, base pressure ratio does not change with base bleed area. While base bleed parameter is large, the base pressure ratio increases with base bleed area. Increasing the temperature of base bleed gas is favorable to increase the base pressure ratio. The intensity of the secondary combustion improves with the increase in the content of fuel-rich gas in base bleed gas, which can improve the base pressure ratio. The results can provide reference for the engineering application of base bleed projectile.

Design and Experiment of a Linear Ultrasonic Motor for Fuze Safety System

TANG Yu-juan, WANG Xin-jie, WANG Jiong

2014, 35(1):  27-34.  doi:10.3969/j.issn.1000-1093.2014.01.004

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For the intelligent and smart requirements of fuze safety system, a linear ultrasonic motor is proposed based on the eximious characteristics of the ultrasonic motor, such as non-electromagnetic interference, fast response, self-locking, simple structure, and flexible design, etc. The initial structure size of motor is determined according to the structure of fuze safety system. The sensitivity of structural parameters to the two-phase modal frequency consistency is analyzed by finite element software ANSYS, and the motor structure size is optimized. Frequency sweep test and vibration modal test are carried out, indicating that the motor can generate required two-phase oscillation modes, and two-phase frequency are quite close each other. The mechanical performance of motor is tested. The test results show that the speed and maximum output force of motor are 88.2 mm/s and 2.3 N

Preparation of HMX/Cu Composite Particles by Electroless Plating Method and their Thermal Decomposition Characteristics

XIONG Lang-lu，GUO Xiao-de， LI Feng-sheng

2014, 35(1):  35-41.  doi:10.3969/j.issn.1000-1093.2014.01.005

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HMX/Cu composite particles are prepared by the electroless plating method. The size, morphology and phase of particles are analyzed by SEM and XRD. And the DSC is applied to study their thermal decomposition characteristic. The results show that the composite particles coated with Cu of 80 nm in diameter have obvious catalysis effect on solid phase decomposition of HMX. The percentage of the prophase decomposition heat increases from 2.37% to 97.29%. On the other hand, the thermal decomposition peak moves to the low temperature of 35.53 ℃ and the rate slows down. Especially, the thermal decomposition of HMX/Cu become to be very intense at the heating rate of 15 ℃/min. Compared with HMX, the apparent activation energy of HMX/Cu is decreased by 33.16 kJ/mol. It is advantageous to the thermal decomposition of nano HMX/Cu through adding a moderate amount of O₂. Moreover, “Effect of spatial distribution” of catalyst is presented based on the analysis of nanometer Cu catalyst mechanism.

Electrostatic Maneuvering Target Tracking Based on Fuzzy Interacting Multiple Model Particle Filter

FU Wei， ZHENG Bin

2014, 35(1):  42-48.  doi:10.3969/j.issn.1000-1093.2014.01.006

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Interacting multiple model particle filter (IMMPF) has the defects of low precision and long updated time, which is not able to meet the requirement of the electrostatic maneuvering target tracking. To solve the problem, a new fuzzy interacting multiple model particle filter (FIMMPF) is proposed. This algorithm can adjust the transition probability matrix of IMM by fuzzy control in real-time and make the motion model that is closet to the current actual motion model occupy larger proportion in the initial state vector. In order to improve the precision of PF algorithm and reduce the updated time of algorithm, central difference expand Kalman filter algorithm is used to generate a proposed distribution and update the target state. The theory analysis and simulation results show that FIMMPF can track the electrostatic maneuvering target with higher positioning precision and smaller updated time.

Study of Millimeter-wave Active Jamming Based on Waveform Deception for Terminal-sensitive Projectiles

CHEN Xi, CHEN Zi-li, XU Jian-zhong, MENG Chun-xiang

2014, 35(1):  49-54.  doi:10.3969/j.issn.1000-1093.2014.01.007

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According to the characteristics of the encounter between terminal-sensitive projectile and metal target and the signal processing circuit of millimeter-wave (MMW) alternating current radiometer, a novel method of MMW active jamming based on waveform deception is proposed. An antenna temperature model for the interference source detection is analyzed and established. The antenna temperature signal has wider pulse width and constant amplitude compared with the output signal in ground metal target detection. Then the signal frequency is distorted by the inherent low-frequency cut-off feature of the video amplifier in the radiometer, generating the split signals of positive and negative pulse waveforms, in which the negative waveform pulse can be used to simulate the output signal in ground metal target detection. The experimental results demonstrate the validity and feasibility of the proposed method, which provides an approach for MMW terminal-sensitive active jamming.

Design and Experiment of Heat Insulation Blanket for Airport Support Equipment

XIE Wei-hong, JIA Feng-hui, LI Shun-cai₃

2014, 35(1):  55-61.  doi:10.3969/j.issn.1000-1093.2014.01.008

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The infrared contrast between airport support equipment and its working background is studied, and an infrared camouflage scheme for the front part of a car is made. After a series of experiment on structure and materials, a new kind of heat insulation blanket is developed, which comprises two 3 mm thick ceramic fiber layers and a 3 mm thick phase-change paraffin wax capsule layer sandwiched in them. To verify its camouflage effect, field experiment is conducted with a thermal imager, and numerical simulation is made by using ANSYS. It turns out that this heat insulation blanket can be used effectively to control the temperature of equipment and background, which meets the infrared radiation camouflage specifications.

Numerical Simulation of Secondary Combustion Gas Field in Concentric Canister Launcher and Improvement Measures of Guider

HU Xiao-lei, LE Gui-gao, MA Da-wei, ZHU Zhong-ling

2014, 35(1):  62-69.  doi:10.3969/j.issn.1000-1093.2014.01.009

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To study the thermo-impact of jet flow secondary combustion, a three-order accurate MUSCL scheme is employed to solve 12-step reaction and 11 species chemical reactions of H₂/CO mixed combustion gas field in concentric canister launcher(CCL), and the zone moving and dynamically layering methods are adopted to simulate missile motion. Compared with free-jet flow experimental results, it is shown that the method is feasible. The jet field characteristic with chemical reactions and the temperature changes of missile body are analyzed. The results show that chemical reaction occures in mixing layer of gas and air out of cylinder and there is no reaction in CCL tube. Reflective shock is due to the mutual interference of gas out of cylinder, exhaust plume and missile tail. The axial temperature of reaction flow field is higher than those of frozen flow and single component flow. Guider can reduce missile body temperature and its height optimal value is near 1.5 times the clearances inside and outside cylinder. The research can provide theoretical significance for the optimization design of CCL structures.

Multi-criteria Decision-making for Guidance System Design Parameters

ZHANG Yi-hang, HOU Ming-shan

2014, 35(1):  70-75.  doi:10.3969/j.issn.1000-1093.2014.01.010

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A multi-criteria decision making (MCDM) method is proposed for the design parameter optimization of missile guidance and control system with the considerations of system performance, cost and other factors. The optimal parameters of the guidance system can be easily obtained

Research on Learning Flight for Unmanned Aircraft in Background Magnetic Field

ZHOU Jian-jun， LIN Chun-sheng， ZHAO Jian-yang

2014, 35(1):  76-82.  doi:10.3969/j.issn.1000-1093.2014.01.011

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The compensation of aircraft's magnetic field interference is a key technology in aeromagnetic survey. For the flight learning problem of unmanned aircrafts, Tolles-Lawson model is improved with the consideration of geomagnetic gradient, a fold line flight method is proposed, and the different flight paths are discussed. The parameters calculated using the proposed fold line flight method have a good result in aeromagnetic compensation according to simulated and real flight data. And increase in numbers of courses is helpful for obtaining more precise parameters with the method. If learning courses are more orthogonal to each other in the condition of same numbers of courses, the calculated parameters is more precise as well.

Dynamics Numerical Analysis of Vehicle-mounted Antiaircraft Missile Launching on the Move

ZHONG Zhou₁， JIANG Yi₁， LIU Qun₂

2014, 35(1):  83-87.  doi:10.3969/j.issn.1000-1093.2014.01.012

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The numerical simulations of different grade random roads are carried out using autoregressive (AR) model, and the travelling and launching integration models of vehicle-mounted antiaircraft missile based on flexible multi-body dynamics are established. According to the simulation results of vehicle dynamics, the worst missile launching time is established. The launching dynamics simulation is conducted and the missile attitude parameters are obtained based on the analyzed results. The effect of velocity and road condition on launching accuracy is analyzed. The research results show that all the three vehicle speeds on B-grade road can ensure launching safety, but vehicle speed on C-grade road is restricuted to 25 km/h.

Study of Characteristics of Unsteady Cavitating Flow around an Axisymmetric Blunt Body

HU Chang-li, WANG Guo-yu, CHEN Guang-hao, WANG Fu-feng, ZHAO Jing

2014, 35(1):  88-95.  doi:10.3969/j.issn.1000-1093.2014.01.013

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Cavitating flow around an axisymmetric blunt body is studied based on the experiments and numerical simulations. A high-speed video camera is used to observe the processes of cavity development and shedding. A partially-averaged Navier-Stokes (PANS) method which is a hybrid RANS/LES turbulent model is applied in numerical simulation. The results show that the characteristics of cavity developing and shedding vary as cavitation number is changied. With the decrease in the cavitation number, the period of cavity developing increases and the shedding of small scale vortices occurs. Moreover, it is found that the shedding generally contains two processes: cavity break-off and cavity shedding. The cavity break-off probably occurs at the location which is about 0.3D away from the shoulder. The cavity sheds with U-vortex type which is induced by the re-entrant flow. In addition, the cavity tends to be steady when the break-off cavity is in conjunction with the attached cavity.

Research on Protective Performance of Foam Aluminum Composite Structure against Stress Wave

YANG Dong-li， WANG Lin， YANG Jie， ZHAO Deng-hui

2014, 35(1):  96-101.  doi:10.3969/j.issn.1000-1093.2014.01.014

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The protective performance of foam aluminum-Al composite structures with different densities and thicknesses are investigated with conventional and improved split Hopkinson pressure bars (SHPB). The experimental results demonstrate that, when foam Aluminum is used as interlayer, the primary stress wave is divided into several stress waves. The time of stress wave arriving at a back plate is postponed, and the wave intensity decreases. The impact of stress wave decreases more clearly with the increase in thickness of interlayer. When foam aluminum-Al composite structure is used as faceplate, the pulse width broadens, the rising edge is improved, and the wave intensity reduces. At the same time, the foam aluminum-Al composite structures can absorb a large part of impact energy, which can be served as stress wave protective material. With the increase in thickness and relative density of the foam aluminum, the wave shaping effect is more significant. The wave intensity reduces, the rising slop becomes flat, however the stress wave pulse changes little. The influence of Al plate thickness on composite structure can be ignored.

Dynamic Modeling and Response of a Morphing UAV with Variable Sweep and Variable Span

YANG Guan-tong, TANG Sheng-jing, ZHAO Lin-dong, GUO Jie

2014, 35(1):  102-107.  doi:10.3969/j.issn.1000-1093.2014.01.015

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For morphing flight vehicles, the changes of sweep angle and span have great influence on key parameters such as aerodynamic forces, inertial moments, pressure center and gravity center. A dynamic model of morphing vehicle with variable sweep and span is established based on Newton-Euler method. The additional force and moment generalized by morphing are deduced. The dynamic response aroused by morphing is studied using decoupled longitudinal equations and quasi-steady aerodynamic model. The results indicate that the changes of sweep and span influence the dynamic characteristics severely; however, the effect of different morphing speed is not remarkable. Appropriate strategy of morphing could weaken the fluctuation of dynamic parameters and relieve the burden of control system.

Method for Improving Mass Property Measurement Accuracy of Large-size Projectiles

WANG Chao， ZHANG Xiao-lin， TANG Wen-yan， WANG Jun， MA Qiang

2014, 35(1):  108-113.  doi:10.3969/j.issn.1000-1093.2014.01.016

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In order to increase the mass property measurement accuracy of the large-size projectile, the calibration methods of measured pose are investigated. A kinematics model for measurement system is established, and the influence of measured pose errors on measuring results are analyzed. A method and process of calibration based on the kinematics are introduced, and the calibration parameters are analyzed and classified. A calibration method using neural networks is provided. Experimental results indicate that the Kinematics method is used to reduce the errors of CG, MOI and POI to 10%, 90% and 23%, respectively, before calibration. The combination method of neural networks and kinematics is used to reduce the errors of CG, MOI and POI to 7%, 45% and 25%, respectively, before calibration.

Research on Dynamic Reliability Sensitivity of Hard Alloy Cutting Tool

WANG Xin-gang， LI He, LYU Chun-mei, WANG Xue-ling₂, PANG Xu₂

2014, 35(1):  114-119.  doi:10.3969/j.issn.1000-1093.2014.01.017

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The selection of design parameters of cutting tool has the direct effect on the reliability of tools and the precision of processed workpiece. Based on stress-strength interference model, a mathematical model on dynamic reliability of hard alloy cutting tool is built, and the change rule of its reliability is obtained. Combining with sensitivity analysis method, the computational formulas of dynamic reliability sensitivity of physical and material parameters of hard alloy cutting tool are deduced, and the curves of reliability sensitivity of design parameters are also given. The results show that the design parameters of cutting tool are more sensitive with the increase in machining time and impact loading action, thus the selection of sensitive parameters should be controlled directly or indirectly so as to reduce its influence on reliability of cutting tool, which can improve the reliability of cutting tool and the precision of processed workpiece. Meanwhile, the proposed method provides a theoretical basis for enhancing the reliability of tool system and the whole machine tool.

Data Fusion Algorithm for Target Trajectory Determination Based on Spline Function Representation

GONG Zhi-hua， ZHOU Hai-yin， GUO Wen-sheng， XU Xu

2014, 35(1):  120-127.  doi:10.3969/j.issn.1000-1093.2014.01.018

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A data fusion algorithm for target trajectory determination based on spline function representation is presented. Under least squares criterion, a nonlinear optimization strategy is applied to search the optimal spline nodes according to different trajectory characteristics. The truncation error can be eliminated and the estimated parameters in the fusion model can be reduced greatly. Therefore, the computational efficiency and estimation accuracy for the trajectory parameters will be enhanced. Finally, the calculation show the validity of the proposed algorithm, and the system errors for each measuring data can be compensated accurately.

Research Notes

Study of Constitutive Model of Ballistic Gelatin at High Strain Rate

WEN Yao-ke, XU Cheng , CHEN Ai-jun

2014, 35(1):  128-133.  doi:10.3969/j.issn.1000-1093.2014.01.019

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In order to numerically simulate the terminal effect of bullet and fragment, the research status of ballistic gelatin physical properties is summarized firstly. The features of rate-dependent hyperelastic model and elastic-plastic hydrodynamic model are studied, respectively. The coefficients of equation of state of ballistic gelatin are concluded based on related experiments. The penetration of a steel sphere into a block of ballistic gelatin is studied experimentally, and is modeled using the finite element method. The comparison of the computed and experimental results shows that the elastic-plastic hydrodynamic model can simulate the experiment more accurately at high velocity impact. Ballistic gelatin is known as a rate-dependent sensitively material, but the thermal softening is dominant at high strain rate, the physical behavior can be modeled with a dynamical constitutive.

Design of Variable Structure Guidance Law for Head-on Interception Based on Variable Coefficient Strategy

XIONG Jun-hui, TANG Sheng-jing, GUO Jie， ZHU Da-lin

2014, 35(1):  134-139.  doi:10.3969/j.issn.1000-1093.2014.01.020

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Head-on interception is a common guidance method for interception problem. The adaptive variable structure guidance law guiding the line-of-sight angular rate to converge to zero is available to improve the guidance precision. However, the variable structure guidance law leads to large required acceleration of interceptor before the line-of-sight angular rate converges to zero, especially in a situation where the target has strong maneuverability as well as high velocity. A strategy making the coefficients of the guidance law vary according to a typical rule via fuzzy control is proposed. Smaller guidance coefficients are selected at the beginning of terminal guidance. Therefore, the guidance command is reduced and a smaller acceleration of interceptor is incurred. As the coefficients grow to the fixed and desired values, the line-of-sight angular rate converges to zero rapidly so that the stability of the guidance system is guaranteed. It is concluded that the fuzzy variable coefficients strategy is highly effective for head-on interception as shown in the simulation.

A Method for Measuring Detection Range of Passive Sonar in Uncertain Environments

CHENG Guang-li， ZHANG Ming-min

2014, 35(1):  140-144.  doi:10.3969/j.issn.1000-1093.2014.01.021

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A method is proposed for measuring the detection range of passive sonar in uncertain ocean environments. The relationship between the detection range of passive sonar and the uncertain parameters of ocean environment are inferred when there are single and multiple uncertain parameters in the ocean environment, the probability distribution functions of detection range of passive sonar are obtained, and then the detection ranges of passive sonar in ocean environment are determined based on the maximum likelihood criterion. For the cases of the single and multiple uncertain parameters of ocean environment, the detection ranges of passive sonar are calculated. The proposed method makes full use of information of PDF of the uncertain environmental parameters, and needs not to specify the type of PDF of ocean environmental parameters and set any threshold for determining the detection range as well.