Table of Content

30 October 2010, Volume 31 Issue 10

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Paper

Drag Reduction and Wake Flow Control by Lorentz Force in Shear Flow

ZHANG Hui, FAN Bao-chun, HE Wang, LI Hong-zhi

2010, 31(10):  1285-1290.  doi:10.3969/j.issn.1000-1093.2010.10.001

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The boundary layer flow of cylinder can be modified effectively by Lorentz force near the surface of the cylinder in the weakly conductive fluid which holds the advantages for cylinder wake control. The experiment and calculation of cylinder wake and its electromagnetic control were investigated in the shear flow. Experiments were conducted in a rotating annular tank filled with a low-conducting electrolyte. A cylinder with electromagnetic actuators mounted on the surface was placed into the electrolyte. Force measurements were carried out by strain gages attached to a fixed beam to which the cylinder was suspended and flow fields were visualized by dye markers. Based on the Navier-Stokes equations considering the electromagnetic body force, i.e. Lorentz force, in the exponential-polar coordinates, the numerical investigations were carried out by means of an alternative-direction implicit alogorithm and a fast Fourier transform algorithm. The experimental and calculated results show that the cylinder wake leans towards the side of slow velocity of flow. The drag and lift vary periodically. The average value of lift is not 0 any longer, and its direction points to the side of slow velocity of flow. The wake becomes a line leaning to the side of slow velocity of flow under the action of Lorentz force. The drag decreases and doesn't oscillate any longer. The lift increases and turns to steady which points to the side of slow velocity of flow.

Drag Reduction and Optimal Control of Cylinder Wake Via Lorentz Force

ZHANG Hui, FAN Bao-chun, HE Wang, LI Hong-zhi

2010, 31(10):  1291-1297.  doi:10.3969/j.issn.1000-1093.2010.10.002

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The flow of the weak electrolyte solution can be controlled by Lorentz forces generated by the suitably chosen magnetic and electric fields, which can be used for the drag reduction, the suppression of vortex shedding and the vortex street in the flow over a bluff body. In order to get a large control effect with small power input, the interaction parameter N, the ratio of the electromagnetic force to the inertia force serving as control input in the control process, should be optimized according to the instantaneous flow field. An adjoint-based ensemble optimization method of control algorithms was developed via Lorentz forces. The performance index and adjoint equations in the expolential-polar coordinates were derived. Numerical simulations based on the Navier-Stokes equations and its adjoint equations for optimal control of cylinder wake were carried out for Reynolds number Re=200. Based on the Navier-Stokes equations considering the electromagnetic body force, i.e. Lorentz force, in the exponential-polar coordinates, the numerical investigations were carried out by means of an alternative-direction implicit algorithm and a fast Fourier transform algorithm. The variation of the optimal interaction parameters with time were described based on calculated results, and the evolution of the flow field and the variation of the drag and lift forces on the cylinder surface in the control process were discussed. The results show that the suppression of vortex shedding, reduction in drag force, absorption of vibration and suppression of noise can be implemented by the optimal control.

Design and Properties of Sandwich Structure for Ballistic-resistant Radome

CHEN Xin, ZHU Xi, ZHANG Li-jun, WANG Xiao-qiang

2010, 31(10):  1298-1302.  doi:10.3969/j.issn.1000-1093.2010.10.003

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A sandwich structure with high transmissivity for ballistic-resistant radome was designed to prevent a radar from impact produced by short distance explosion of anti-radiation weapon. Ultra-high molecular weight polyethylene (UHMWPE) laminate was determined as anti-penetration layer of sandwich structure by testing the ballistic penetration property of UHMWPE laminates with different thicknesses. The structure parameters were obtained by electromagnetic optimization, and the electromagnetic performance of designed sandwich was theoretically analyzed. Ballistic and electromagnetic test results show that the designed sandwich structure resists fragment impact produced by the explosion of a certain anti-radiation missile at 15m, with minimum transmissivity (power transmission coefficient) of 97.8% and average value of 98.6% at S band. The design method for sandwich structure of ballistic-resistant radome has been proven to be reliable by theoretical and experimental results.

Numerical Simulation on Hydrodynamic Characteristics of Submarine Missile in the Vertical Launch Process

MIN Jing-xin， WEI Ying-jie， WANG Cong， CAO Wei， ZOU Zhen-zhu

2010, 31(10):  1303-1309.  doi:10.3969/j.issn.1000-1093.2010.10.004

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The cavitation flow characteristics and hydrodynamic evolution during the rise of submarine launched missile were researched by using a numerical simulation method. The fluid-solid coupling problem of moving boundary of missile body and cavitation flow field was solved by using a continuity equation, transport equations of liquid mass fraction, RANS (Reynolds-Averaged Navier-Stokes) equation in conjunction with a dynamic mesh technique and a standard k-ε turbulence model. Furthermore, the underwater moving process of submarine launched missile was numerically simulated, the effect of warhead lines of submarine launched missile on the partial cavitation and hydrodynamic performance was analyzed in detail, and three groups of underwater trajectory of submarine launched missile in the case of thrust-weight ratio were given . The simulational and analysis results show that the partial cavitating can increase the hydrodynamic performance of missile, and a modest warhead lines of missile can restrain the partial cavitation and improve its hydrodynamic performance.

The Magnetic Field Penetration Characteristics in Bore of Small Caliber Fuze Using Inductive Energy

WU Zhi-liang， ZHANG He

2010, 31(10):  1310-1315.  doi:10.3969/j.issn.1000-1093.2010.10.005

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A method of which the stored inductive energy is provided for fuze in the process of information setting before a projectile lauch was proposed in order to solve the problem of small room for designing a small-calibre electronic fuze. This method, which can save the space of extra fuze power, provides a new way to design fuze power. Therefore, a mathematical model of electromagnetic induction in the bore was set up. The characteristics of magnetic field penetrating through the metal gun barrel made of nonferromagnetic material were analyzed. The analyses results show that the magnetic field intensity can be 80% of the source after penetration only if the frequency of external electromagnetic excitation should be less than 5 kHz. With the increase in the frequency of source magnetic field, the magnetic field intensity is exponentially attenuated after penetrateion. The experimental results show that the inductive energy storage fuze prototype designed according to the above-mentioned theory meets the technical requirements of small calibre fuze. And the analyses conclusion of magnetic field penetration characteristics is helpful to design the inductive energy storage fuze in bore.

Roll Angle Measurement of Spinning Projectile Based on Non-orthogonal Magnetic Sensors

LI Ding, BU Xiong-zhu

2010, 31(10):  1316-1321.  doi:10.3969/j.issn.1000-1093.2010.10.006

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In allusion to some deficiencies of micro inertial sensors, of which the measuring error spreads with time and the measuring range can not meet the requirement of roll angle measurement of spinning projectile, the roll angle measurement of spinning projectile by using the magnetic sensors and its engineering implementation feasibility were researched. A mathematical expression was given for the magnetic sensors installed at the different angles and positions, and the attitude angles were calculated according to the ratio of extreme value of the two non-orthogonally installed magnetic sensors which has corresponding relationship with pitch angle. The condition of singularity and the feasibility of roll angle measurement using the magnetic sensors were analyzed, and the half size hardware-in-the-loop experiment was accomplished based on the sensor configuration and calculation method. The experimental results show that the resolved errors of pitch angle and roll angle can be controlled within the range of 1°, this measurement scheme can apply to the spinning projectile which has a small variety of yaw angle.

MD Simulation of the Crystal Morphology of β-HMX Affected by NTOFOX-7 and RDX

HUANG Can-can, LI Li-jie, CHEN Shu-sen, JIN Shao-hua, YUAN Liu, CHEN Teng-xiao

2010, 31(10):  1322-1326.  doi:10.3969/j.issn.1000-1093.2010.10.007

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The crystal growth morphology of β-HMX was simulated using a molecular dynamics (MD) method and Material Studio software. A double-layer structure model was used to simulate the effect of insensitive energetic compounds NTO, FOX-7 and RDX on β-HMX crystal morphology, as well as their coating role on β-HMX crystal. The results show that three types of molecules can be attached to the grown crystal face of β-HMX, of which FOX-7 can be evenly attached to the β-HMX crystal face, expecting to achieve high energy-insensitive coating, but having a little influence on β-HMX crystal morphology. NTO and RDX molecules have different bonding energy on each β-HMX crystal face, so they can control the HMX crystal morphology to some extent, of which, RDX can make β-HMX tend to spherical crystal morphology.

Research on Catalytic Combustion Model of AP/Al/HTPB Propellant

FENG Feng₁， CHEN Jun₁， SONG Hong-chang₂， ZHENG Ya₁

2010, 31(10):  1327-1332.  doi:10.3969/j.issn.1000-1093.2010.10.008

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The effects of the catalysts on the thermal decomposition of AP/Al/HTPB (hydroxy

Research on Sulfur-free Black Powder with Low Smoke Signature

CUI Qing-zhong， JIAO Qing-jie， CHEN Yan， LIU Shuai

2010, 31(10):  1333-1336.  doi:10.3969/j.issn.1000-1093.2010.10.009

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K_0.333(NH₄)_0.667NO₃ was prepared using a

Micro-appearance and Formation Mechanisms of PBX Cutting Surface

ZHANG Qiu, HUANG Jiao-hu, YIN Rui, TANG Wei

2010, 31(10):  1337-1340.  doi:10.3969/j.issn.1000-1093.2010.10.010

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Micro-appearance of explosive component affects its surface performance greatly

Synthesis and Properties of 3-Amino-246-Trinitrophenol and 35-Diamino-246-Trinitrophenol

ZHANG Xue-mei, DONG Hai-shan, ZHOU Zhi-ming, LI Hai-hua

2010, 31(10):  1341-1345.  doi:10.3969/j.issn.1000-1093.2010.10.011

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3-amino-2,4-trinitrophenol and 3,5-diamino-2,4,6-trinitrophenol were obtained by vicarious nucleophilic substitution (VNS) amination of picric acid under the different conditions in the yield of 81% and 78% respectively, which used 4-amino-1,2,4-triazole as the aminating reagent. The structures of the products were identified by IR, ₁HNMR, and elemental analysis. The thermal decomposition processes were studied by DTA-TG, and their shock sensitivities were tested. The results show that the peak temperatures of thermal decomposition of 3-amino-picric acid and 3,5-diamino-picric acid are 243.7 ℃ and 286.9 ℃, respectively, and their characteristic fall heights are 42.8 cm and 56.1 cm, respectively. The peak temperature of thermal decomposition increases and the shock sensitivity is lowered when amino group is introduced into the molecular of picric acid.

Numerical Simulation on Effect Factors of Stability of Powder Combustion in Microtube

LIU Jian， SHEN Rui-qi， YE Ying-hua， HU Yan

2010, 31(10):  1346-1350.  doi:10.3969/j.issn.1000-1093.2010.10.012

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To understand the effect factors of solid energetic material combustion in microcombustion, the effect of the dimensions and thickness of combustor and the thermal conductivity of its wall on the temperature distribution of wall and the heat loss of a microtube combustor during the burning of solid grain in the microtube combustor was studied by transient-state thermal analysis under ANSYS. Results show that the heat transfer of combustor's wall is the key factor for combustion stability in microtube combustor. With the reduction in the dimensions of combustor, the interaction of gas and wall is strengthened, and the heat loss is also increased, resulting in the instability or extinction of combustion. The simulation also indicates that the thermal conductivity of wall has the competing effect on the heat transfer of combustor's wall. The heat loss of wall and the heat transferred through the wall axially to the preheated zone decrease with the reduction in the heat conductivity of wall, however, the former makes greater contribution, which improves combustion stability. In addition, a thicker wall is beneficial to combustion stability in a certain extent.

Correlation Between Burning Rate and Thermal Decomposition of AP/Al-CMDB Propellants

LI Ji-zhen, FU Xiao-long, LIU Xiao-gang, FAN Xue-zhong, LIU Zi-ru, ZHANG La-ying

2010, 31(10):  1351-1356.  doi:10.3969/j.issn.1000-1093.2010.10.013

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The correlation between burning rate and thermal decomposition of AP/Al-CMDB propellants in the pressure range of 1.0~13.0 MPa were studied by a high pressure differential scanning calorimetry (PDSC). The results show that the factors of pressure p and exothermic rate ΔH_d/Δθ must be analyzed respectively in the model of the correlation between burning rate and thermal decomposition of AP/Al-CMDB propellants in the pressure range of 1.0~13.0 MPa, where the formula of the correlation model is u=k_uP^a［ΔHd/Δθ］^b. The calculated results show that there is an error of lower than 2.50% between the theoretical burning rates and the experimental values.

Synthesis of 2-methoxy-35-dinitryl-6-azidepyrazine

LIU Yao-peng, CHEN Hua-xiong, CHEN Shu-sen, JIN Shao-hua

2010, 31(10):  1357-1362.  doi:10.3969/j.issn.1000-1093.2010.10.014

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MDNAP is a precursor for novel energetic compounds. 2-methoxy-6-chlorin pyrazine (MCP) was first synthesized from raw material 2,6-dichlorin pyrazine by substituting chlorine with methoxyl with a yield of 81%. 2-methoxy-3,5-dinitryl-6-chlorin pyrazine (MDNCP) was obtained by the nitration of MCP with mixed nitric and sulfuric acids under facile conditions with a yield of 75%. 2-methoxy -3,5-dinitryl-6-azide pyrazine (MDNAP) was synthesized from MDNCP by the zaide substitution of MDNCP with a yield of 60%. Therein, all the intermediates were characterized by IR, H₁ NMR, ESI-MS and EI-MS.

Effect of Cotton Linter and Nitrification Conditions on Nitrogen Content and its Distribution Uniformity of Nitrocellulose

WANG Wen-jun, ZUO Yang, LI Yong-hong, SHAO Zi-qiang, ZHANG You-de

2010, 31(10):  1363-1371.  doi:10.3969/j.issn.1000-1093.2010.10.015

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The effects of DP of the cotton linter, the nitrification time, and the HNO₃ concentration in nitric-sulfuric mixes on the nitrogen content and its distribution uniformity of nitrocellulose were investigated by a test instrument developed by Beijing Institute of Technology .It is the first time that the swelling degree of fibre is used as a analysis indicator. The results show that the DP of cotton linter has no significant effect on the nitrogen content, but the lower the DP is, the more uniform the nitrogen distribution of the resulting nitrocellulose is; As the nitration time extends, the nitrogen content gradually increases and reaches its maximum at the time of 30 mins, then it shows a slight downward trend; while the distribution index D_ξ of NC shows a contrary trend, it initially decreases with time and obtains its minimum at the time of 30mins, then become larger with further extension of nitration time. The nitrogen content of nitrocellulose increases with the HNO₃ concentration within the interested range, while the most uniform nitrogen distribution can only be obtained in a appropriate HNO₃ concentration value, too low or too high concentration of HNO₃ in nitric-sulfuric mixes result in wider nitrogen distribution. It is found from the investigation that the swelling degree of fiber is a direct indicator affecting the nitrogen distribution of nitrocellulose. The higher the swelling degree is, the better the distribution uniformity of nitrogen content is.

Numerical Simulation and Experimental Investigation on Mixed-compression Inlet of Solid Fuel Ramjet Extended-range Projectile

XIA Qiang, WU Xiao-song, SUN Bo, XIONG Zhi-ping

2010, 31(10):  1372-1378.  doi:10.3969/j.issn.1000-1093.2010.10.016

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The complex flow field of a mixed-compression inlet of solid fuel ramjet extended-ranged projectile with struts was numerically simulated by using the 3D Reynolds-averaged Navier-Stokes equations in terms of different attack angles and inflow Mach numbers, and also the wind tunnel test was made. The schlieren photographs of inlet, the distribution of static pressure along the inlet and the influence of different operations on total pressure at the exit of inlet were obtained. The results indicate that the numerical flow structure and wind tunnel test schlieren photographs of inlet are identical. With the increase in angle of attack, the air flow enters into the inlet, the total pressure recovery coefficient decreases, and the Mach number of exit almost holds the line. At the subcritical state, the influence of attack angle on total pressure recovery coefficient increase significantly, and its value is lower than that in the critical state. Furthermore, under the same inflow Mach number, the total pressure recovery coefficient increases as the backpressure at the exit of inlet raises.

Modeling and Example Analysis of Wear Random Process

LIU Qin, LI Juan, LIU Ying

2010, 31(10):  1379-1382.  doi:10.3969/j.issn.1000-1093.2010.10.017

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Considering the time dependence and randomness of wear process, a modeling metho

Research Notes

Research on the Application of Explosive Network in the Shaped Charge Warhead

XU Li-xin， LIU Hong-li， SHEN Xiao-jun， ZHANG Guo-wei

2010, 31(10):  1383-1388.  doi:10.3969/j.issn.1000-1093.2010.10.018

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With respect to the problems of that the shaped charge warhead currently uses th

Research on the VNS Reaction of 1-Amino-123-Triazole

CHEN Fu-xue, FU Zhan-da, LIU Bao-jie, WU Yu-kai, ZHOU Zhi-ming

2010, 31(10):  1389-1393.  doi:10.3969/j.issn.1000-1093.2010.10.019

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1-amino-1,2,3-triazole was used as a new amino source to prepare TATB through

Research on Artificial Neural Network-based Prediction Model for the Critical Thickness of RDX

LIU Yu-cun₁, YU Guo-qiang, DONG Guo-qing₃

2010, 31(10):  1394-1397.  doi:10.3969/j.issn.1000-1093.2010.10.020

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The critical thickness of RDX at different densities, grain sizes and binding content was tested using a wedge-shaped charge. The Elman prediction model was established using density, grain size and binding content as input variables, and the critical thickness of RDX as output variable to predict the critical thickness under other conditions. The results show that the relationship between the three factors and the critical thickness is the same as that in Ref.［9-11］, and the neural network can be used to predict the critical thickness of RDX.

An Effective Optimization Method for Designing IIR Digital Filters Based on AFHPSO

GAN Ming-gang, PAN Feng, CAI Tao

2010, 31(10):  1398-1402.  doi:10.3969/j.issn.1000-1093.2010.10.021

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The optimization design of IIR digital filters is a multi-parameter problem. A

Numerical Analysis on Non-planar Vibration of the Highline System for Alongside Replenishment

HE Xue-jun, ZHANG Liang-xin, REN Ai-di

2010, 31(10):  1403-1408.  doi:10.3969/j.issn.1000-1093.2010.10.022

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A theoretical model of non-planar vibration of highline system for alongside replenishment was established, in which the influences of the lumped mass and inclination angle of highline are considered. The third order mode of a kinetic equation was discretized to obtain an ordinary differential equation of kinetic control by Galerkin method. The dynamic response of the highline system was analyzed by Mathematica. The factors influencing the dynamic behavior of highline system were considered, including inclination angle and tension fluctuation of highline system. The result shows that the tension fluctuation of highline system is one of the important factors influencing the dynamics behavior of highline，which could change the periodical motion behavior of highline and excite a large range variation of amplitude of the highline system.

Fitting Research on the Relaxation Function of Shear Modulus for Viscoelastic Materials

WEI Yan-bin, SHI Yi-kai, LIU Peng

2010, 31(10):  1409-1412.  doi:10.3969/j.issn.1000-1093.2010.10.023

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The characteristic parameters of viscoelastic physical model must be provided for the finite element analysis of viscoelastic materials. A numerical fitting method was used to derive the relationship of the generalized Maxwell model and the normalized experimental curve in terms of a model simplified for the viscoelastic material-costal cartilage, realize the fitting of experimental curve with the generalized Maxwell model, and receive the Maxwell model parameters of costal cartilage for viscoelastic finite element analysis. The simulation shows that the curve fitting degree is high.