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보조동력장치 연료 공급을 위한 솔레노이드 밸브의 다중물리 해석
장세명(S. M. Chang),정헌술(H. S. Jeong),허재성(J. S. Huh) 유공압건설기계학회 2009 유공압건설기계학회 학술대회논문집 Vol.2009 No.11
The APU(auxiliary power unit) for a rotary-wing aircraft supplies excess power like electric generators beyond the main thrust. The fuel supply system of APU consists of a set of complex pipelines from the fuel tank to the ignition unit of gas turbine engine. Some of primary valves control the flow rate of fuel, and they are worked with torque motors by changing electrical current. A two-stage method is used in the numerical simulation of this study: a three-dimensional model for the simulation of the real-existing servo valve in an aerospace system has been developed, based on multiple physics such as electro-magneto-statics, structural dynamics, and fluid mechanics with FEM(finite element method) and FVM(finite volume mthod). The technical method for the design of an electrical servo valve should be established in detail with this numerical simulation.
비정상 압축성 유동 해석을 위한 고차 정확도 적응 격자 기법의 연구
장세명(S.M. Chang),Philip J. Morris 한국전산유체공학회 2008 한국전산유체공학회지 Vol.13 No.3
The high-order numerical method based on the adaptive mesh refinement(AMR) on the quadrilateral unstructured grids has been developed in this paper. This adaptive-grid method, originally developed with MUSCL-TVD scheme, is now extended to the WENO (weighted essentially no-oscillatory) scheme with the Runge-Kutta time integration of fifth order in spatial and temporal accuracy. The multidimensional interpolation was studied in the preliminary research, which allows us to maintain the same order of accuracy for the computation oj numerical flux between two adjacent cells of different levels. Some standard benchmark tests are done to validate this method for checking the overall capacity and efficiency of the present adaptive-grid technique.
장세명(S.M. Chang),필립 존 모리스(P.J. Morris) 한국전산유체공학회 2006 한국전산유체공학회지 Vol.11 No.4
In this paper, the authors developed a multidimensional interpolation method inside a finite volume cell in the computation of high-order accurate numerical flux such as the fifth order WEND (weighted essentially non-oscillatory) scheme. This numerical method starts from a simple Taylor series expansion in a proper spatial order of accuracy, and the WEND filter is used for the reconstruction of sharp nonlinear waves like shocks in the compressible flow. Two kinds of interpolations are developed: one is for the cell-averaged values of conservative variables divided in one mother cell (Type 1), and the other is for the vertex values in the individual cells (Type 2). The result of the present study can be directly used to the cell refinement as well as the convective flux between finer and coarser cells in the Cartesian adaptive grid system (Type 1) and to the post-processing as well as the viscous flux in the Navier-Stokes equations on any types of structured and unstructured grids (Type 2).
장세명(S.M. Chang),정연규(Y.G. Jung),김사지(S.J. Kim),송찬이(C.Y. Song),장근식(K.S. Chang) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Extracorporeal Shock Wave Therapy (ESWT) is known a very effective clinical treatment against persistent musculo-skeletal pains that do not respond with the conservative medical therapy. In the hydroelctric type ESWT, shock waves are generated by the electric sparks between two electrodes a few milimeters apart charged in tens of thousand volts, immersed in water and located at the first focal point of an ellipsoidal reflector. Then the shock is focused at the second focal point of the reflector for clinical use. The shock wave is bombarded thousand of times on the target area positioned at the second focal point. In this medical equipment, there is lots of obscurity in the physical and biological effect. We first make CFD analysis to expound the shock focusing process of this pressure device.
보조동력장치 연료 공급용 서보밸브 토크모터의 기초 수치모사 연구
장세명(S. M. Chang),정헌술(H. S. Jeong),장강원(G. W. Jang),양인영(I. Y. Yang),이원중(W. Lee) 유공압건설기계학회 2009 드라이브·컨트롤 Vol.6 No.2
The APU(Auxiliary Power Unit) needs a set of complex pipeline for the fuel supply system where some of the main valves controlling the flow rate consist of the servo valve worked with a torque motor. The input electric current produces an induced magnetic field almost perpendicular to the background magnetic filed generated by fixed permanent magnets. The induced torque deforms the tubular bushing, and directly rotates an armature, which can open and close the valve. In this study, we start from a basic analytic model using a simple electro-magneto-statics, and expand our model to the three-dimensional one computationally applying a commercial code named COMSOL. The result is compared with each other, and reasonable numerical data are obtained for the dynamic behavior and multi-physics system.
차세대 인공위성 전기저항제트 가스추력기의 다물리 수치모사
장세명(S.M. Chang),최진철(J.C. Choi),한조영(C.Y. Han),신구환(G.H. Shin) 한국전산유체공학회 2016 한국전산유체공학회지 Vol.21 No.2
NEXTSat-1 is the next-generation small-size artificial satellite system planed by the Satellite Technology Research Center(SatTReC) in Korea Advanced Institute of Science and Technology(KAIST). For the control of attitude and transition of the orbit, the system has adopted a RHM(Resisto-jet Head Module), which has a very simple geometry with a reasonable efficiency. An axisymmetric model is devised with two coil-resistance heaters using xenon(Xe) gas, and the minimum required specific impulse is 60 seconds under the thrust more than 30 milli-Newton. To design the module, seven basic parameters should be decided: the nozzle shape, the power distribution of heater, the pressure drop of filter, the diameter of nozzle throat, the slant length and the angle of nozzle, and the size of reservoir, etc. After quasi one-dimensional analysis, a theoretical value of specific impulse is calculated, and the optima of parameters are found out from the baseline with a series of multi-physical numerical simulations based on the compressible Navier-Stokes equations for gas and the heat conduction energy equation for solid. A commercial code, COMSOL Multiphysics is used for the computation with a FEM (finite element method) based numerical scheme. The final values of design parameters indicate 5.8% better performance than those of baseline design after the verification with all the tuned parameters. The present method should be effective to reduce the time cost of trial and error in the development of RHM, the thruster of NEXTSat-1.
원심압축기 임펠러의 효율최적화를 위한 반익 유동에 대한 수치연구
김성수(S. S. Kim),왕학민(H. M. Wang),노태현(T. H. Noh),김성수(S. S Kim),장세명(S. M. Chang) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.11
A splitter-blade is optimized for the efficiency to determine the location of a system of impeller for the centrifugal compressor using CFD technique. The splitter-blade formed the steady flow at the exit of impeller as well as the dividing flow of the full-blade system. The cross-sectional area of the flow depending on the starting position and angle should be set between full-blade and splitter-blade. Changing the cross-sectional area divided by the splitter-blade, we can stabilize the dominant part of exit flow. Therefore, in this study, the parameters of the starting position and angle effect on determining the optimized efficiency of splitter-blade of impeller system. CFD is shown to be very helpful for this procedure of design.