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4th International Conference on Industry, Information System and Material Engineering, IISME 2014

作者： Wessam, Mahfouz Elnaggar Chen, Zhi-Hua Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing 210094 Jiangsu China

ISBN: (纸本)9783038352143

The paper presents results of investigation of a flow over unguided artillery projectile in order to understand variation of flow parameters past a 155 mm artillery projectile M107 and the performance of the computational code. Furthermore;static aerodynamic coefficients were calculated. The flow around projectile was solved as 3-D unsteady compressible flow. © (2014) Trans Tech Publications, Switzerland.

关键词： Computational fluid dynamics

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The Hydrodynamic Characteristics of a Circular Cylinder in an Electrically Low-Conducting Fluid

The Hydrodynamic Characteristics of a Circular Cylinder in a...

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the 5th International Conference on Mechanical Engineering and Mechanics

作者： Ying HE Zhihua CHEN Xinmin YANG Wenjun YI Key Laboratory of Transient Physics Nanjing University of Science and Technology

A closed-loop control algorithm has been developed for suppressing the vortex shedding of flow past a circular cylinder in an electrically low-conducting fluid(e.g. seawater). The intent is to avoid both vortex shedding and flow separation from the body, which is achieved through the introduction of localized electromagnetic forces(Lorentz forces) generated by an array of permanent magnets and electrodes on the surface of the circular cylinder. More specifically, the closed-loop control has been derived from the equations capable of determining at all times the intensity of the Lorentz force in order to control the flow. This is accomplished first, independently of the flow(open loop algorithm) and second, based on some partial flow information measured on the surface of the solid body.

关键词： Vortex Shedding Flow Control Flow Separation Lorentz Force

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Experiment Study on Detonation Noise of Pulse Detonation Engine with Gapped Nozzle

Experiment Study on Detonation Noise of Pulse Detonation Eng...

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the 5th International Conference on Mechanical Engineering and Mechanics

作者： Guiyang XU Chunsheng WENG Ning LI National Key Laboratory of Transient Physics Nanjing University of Science and Technology

In order to explore the control of formation and propagation of pulse detonation engine noise, the experiment system of pulse detonation engine with gapped nozzle is set up. The investigation of detonation noise characteristic is carried out in the range from 800 mm to 3000 mm at four different angles. The results show that maximum detonation pressure does not change significantly with the gapped nozzle, but the pressure oscillation amplitude is depressed significantly. The reduction of detonation positive duration by 60.91% and shorten time interval between impact noise and jet noise are observed because of shortening the exhaust process time. The gapped nozzle shows significant influence on impact noise and jet noise suppression with amplitude decrease by 40.90% and 47.55%. The detonation noise directivity is ambiguous as the reduced ratio of impact noise at the angles of 0° and 30°. The gapped nozzle would be utilized to increase ratio of jet noise and impact noise amplitude. The results are of great significance for studying the mechanism of detonation noise and expediting the process of the engineering application.

关键词： Pulse Detonation Engine Noise Radiation Directivity Experimental Research Nozzle

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Two Dimensional Numerical Simulation of the Influence of Flow Index on Two-phase Detonation of Gel Fuel/Air

Two Dimensional Numerical Simulation of the Influence of Flo...

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the 5th International Conference on Mechanical Engineering and Mechanics

作者： Jianlu YANG Chunsheng WENG National Key Laboratory of Transient Physics Nanjing University of Science & Technology

The process of two-phase detonation was studied on gel fuel and air mixture, and the impact of flow index(n) was obtained on detonation. Two-phase detonation governing equations were established according to the nature of gel fuels and the characteristics of two-phase detonation flow field. The governing equations were solved by the method of conservation element and solution element(the CE/SE method). In this paper, the detonation of gasoline-based gel fuel in 2.0 meters detonation tube was simulated. The results indicate that the deflagration to detonation transition(DDT) distance is impacted by flow index(n) significantly. The DDT distance is 339 mm, 485 mm and 647 mm for the flow index n=0.1, 0.25 and 0.4, respectively. As the flow index(n) increases, the distance of deflagration to detonation transition becomes longer. Along with detonation wave sweeping through the droplets of gel fuel, the droplets experience three stages: the shock-induced stage, the reaction accelerating stage and the complete reaction stage. Each stage is affected by flow index(n), especially for the reaction accelerating stage. With the flow index(n) increasing, the time required for complete evaporation and peeling of fuel droplets increases. The calculation results for further investigating the effect of the flow index(n) on the detonation, exploring the way to shorten the DDT distance and increasing the pulse detonation engine thrust are of important significance.

关键词： Flow Index Deflagration to Detonation Evaporation Peeling Conservation Element and Solution Element Method

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Application of the CE/SE Method to Magnetohydrodynamic Augmentation of Pulse Detonation Engines

Application of the CE/SE Method to Magnetohydrodynamic Augme...

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the 5th International Conference on Mechanical Engineering and Mechanics

作者： Ling LIN Chunsheng WENG National Key Laboratory of Transient Physics Nanjing University of Science & Technology

The technology of magnetohydrodynamic(MHD) acceleration is focus of increasing attention due to its widely application prospect in aeronautics and astronautics. Thrust of pulse detonation engines can be increased by MHD augmentation. In the pulse detonation induced MHD ejector(PDIME) concept, overpressure at the exit of converging-diverging nozzle blocks flow in the bypass tube. With an upstream propagating, the seeded air stream in bypass tube is first shocked and raised to high-temperature to ionize thermally. The magnetic field energy then is added to accelerate the ionization gas from bypass tube, which thus augments the propulsive performance of PDE. In this paper, the model of gas-liquid two-phase detonation engine with bypass MHD ejector concepts was established, in which the engine was ignited by plasma jet. An appropriate approach of Conservation Element and Solution Element(CE/SE) was deduced for solving 2D plasma jet ignition and detonation process with MHD accelerator. The computational results show that the deduced CE/SE method can capture discontinuity effectually such as shock in the PDIME. It has been observed that thrust augmentation can be accomplished by the bypass accelerator under the given flight condition,and even then the bypass accelerator will activate only under a given velocity. Further analysis and optimization are required owing to some challenges associated with achieving performance gains. The results have certain significant reference for the experimental study in the future.

关键词： The CE/SE Method Pulse Detonation Engines MHD Augmentation Plasma Jet Ignition

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Numerical Simulation Study on Effect of Aspect Ratio for Penetration Process of Long-rods

Numerical Simulation Study on Effect of Aspect Ratio for Pen...

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the 5th International Conference on Mechanical Engineering and Mechanics

作者： Lei MAO Qing FANG National Key Laboratory of Transient Physics Nanjing University of Science and Technology

Using LS-DYNA finite element program and referencing the existing experimental data to set up numerical simulation for tungsten alloy long-rods penetrating into semi-infinite target. The numerical model was checked. In order to investigate the effect of aspect ratio on the long-rods penetration process, setting up numerical simulation for different aspect ratio long-rods penetrating into semi-infinite target without changing material and mass of the penetrator. Simulation results show that: the results are good agreement with the experimental data, indicating that the numerical model established and the material parameter calibrated are reasonable and effective in this paper. At the same impact velocity, the larger the aspect ratio, the smaller the diameter of the crater, the deeper the penetration depth, the penetration efficiency reduces. But with the increasing of aspect ratio, these effects become weakened gradually.

关键词： Long-rod Aspect Ratio Penetration Numerical Simulation

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Electro–magnetic control of shear flow over a cylinder for drag reduction and lift enhancement

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Chinese physics B 2013年第10期22卷 362-369页

作者：张辉范宝春陈志华陈帅李鸿志 Science and Technology on Transient Physics Laboratory Nanjing University of Science and Technology

In this paper, the electro-magnetic control of a cylinder wake in shear flow is investigated numerically. The effects of the shear rate and Lorentz force on the cylinder wake, the distribution of hydrodynamic force, and the drag/lift phase diagram are discussed in detail. It is revealed that Lorentz force can be classified into the field Lorentz force and the wall Lorentz force and they affect the drag and lift forces independently. The drag/lift phase diagram with a shape of ＂8＂ consists of two closed curves, which correspond to the halves of the shedding cycle dominated by the upper and lower vortices respectively. The free stream shear （K 〉 0） induces the diagram to move downward and leftward, so that the average lift force directs toward the downside. With the upper Lorentz force, the diagram moves downwards and to the right by the field Lorentz force, thus resulting in the drag increase and the lift reduction, whereas it moves upward and to the left by the wall Lorentz force, leading to the drag reduction and the lift increase. Finally the diagram is dominated by the wall Lorentz force, thus moving upward and leftward. Therefore the upper Lorentz force, which enhances the lift force, can be used to overcome the lift loss due to the free stream shear, which is also obtained in the experiment.

关键词： cylinder wake control Lorentz force shear flow hydrodynamic force

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Effects of the Boattail of a Spinning Projectile on Its Aerodynamics Characteristics

Effects of the Boattail of a Spinning Projectile on Its Aero...

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the 5th International Conference on Mechanical Engineering and Mechanics

作者： Jie MA Zhihua CHEN State Key Laboratory of Transient Physics Nanjing University of Science & Technology

The Magnus effect acts on a spinning projectile including the side force and yawing moment, however, its final consequence on the projectile depends on multiple parameters, such as the spin rate, angle of attack, body shape, fins and bottail etc. The prediction of Magnus and dynamic stability derivatives of spin-stabilized projectiles were recently reported, and it was found that each configuration showed differences in the characteristics of Magnus moment. In order to understand such phenomenon, the Magnus effect on a generic 6.37 diameter long tangential-ogive-cylinder type projectile is studied by means of 3D DES simulations. The reliability of our numerical method has been verified with previous experimental data. Several configurations with different boattails were investigated numerically using the same method, the effects of different boattails and base geometry on the aerodynamic coefficients are shown and discussed, which can provide guidance for designing and improving the flight quality of spinning projectiles.

关键词： Magnus Effect Boattail Configuration Aerodynamic Characteristics

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Measurement of electromagnetic radiation dissipation in pulse power supply discharging

Measurement of electromagnetic radiation dissipation in puls...

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Electromagnetic Launch technology

作者： Yong Jin Yazhou Zhang Hui Tian Chunxia Yang Qinghua Lin Baoming Li National Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing China

A 2MJ pulse power supply (PPS) has been designed to support the development and evaluation of candidate propellants for an Electrothermal-Chemical (ETC) gun. The overall power system consists of twenty capacitive 100kJ pulse power modules. Each capacitor bank of the 100kJ module consists of two 12kV 50kJ capacitors. A triggered vacuum switch (TVS) was adopted as the main pulse power-closing switch. Electromagnetic radiation dissipation is always observed in pulse power supply discharging experiments. This kind of pulse radiate dissipation always has an influence in discharging peak current and load energy deposition. A copper wire sensor is designed and employed to measure the radiation intensity distributions near the facility. And the whole system's radiate dissipation is also obtained in calculations. Results show that radiation dissipation is always detected at the TVS triggering moment in synchronized discharging model. The received signal has a main frequency nearly 125kHz, and rapidly oscillating damped in 1ms. The radiation dissipation energy is nearly 3% in the whole discharging energy and the discharge efficiency keeps more than 75%.

关键词： Capacitors Plasmas Propellants Switches Current measurement Coils Power measurement

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Nuclear norm minimization in subspace based continuous-time Hammerstein system identification

Nuclear norm minimization in subspace based continuous-time ...

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11th IEEE International Conference on Control and Automation, IEEE ICCA 2014

作者： Dai, Mingxiang Zhang, Jingxin Chai, Li Science and Technology on Transient Physics Laboratory Nanjing University of Science and Technology Nanjing 210094 China School of Software and Electrical Engineering Swinburne University of Technology VIC3211 Australia School of Information Science and Engineering Wuhan University of Science and Technology Wuhan 430081 China Dept of Electrical and Computer Systems Engineering Monash University VIC 3800 Australia

ISBN: (纸本)9781479928378

A novel method combining the nuclear norm minimization (NNM) and continuous-time (CT) subspace identification method (CSIM) is proposed to identify the CT Hammerstein model with little priori information. The nuclear norm minimization, which is the heuristic convex relaxation of the minimum rank constraint, is applied to the CT subspace identification method, for the purpose of improving the robustness and accuracy of identification. The proposed method can perform the identification well without the priori information about the Hammerstein model, which not only reduces the complexity of the identification problem but also broaden its applications. The nonlinear block of Hammerstein model is approximated with the pseudospectral method, which replaces the nonlinear function with Lagrange basis functions. A typical numerical example is presented to verify the NNMCSI method and the identification results are compared with the refined instrumental variable method. © 2014 IEEE.

关键词： Functions

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