• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.6
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• pp.39-48
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• 2017

In this study, combustion modeling of ZPP and $BKNO_3$ mainly used in the PMD industries has been performed. Saint Robert's law, energy conservation equation, and the Noble-Abel equation of the state have been used for governing equations. The results of pressure obtained from established combustion models and actual CBT have been compared. In the case of ZPP, the model has predicted a pressure curve similar to that of the experimental results, but $BKNO_3$ has showed that the maximum pressure of the model is greater than the experiment at small chamber volume. For these gaps, the probability of $BKNO_3$ unburning has been considered.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.11a
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• pp.10-11
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• 1997

고체 추진제를 사용하는 추진 시스템을 개발하는데 가장 커다란 문제로 인식되고 있는 것은 추진제의 연소 특성을 이해하는 일이다. 그 중에서도 연소실의 압력 진동과 추진제 벽면으로 흡수되는 복사 열전달에 의한 연소율(burning rate)의 변화로 인하여 발생하는 연소 불안정에 대한 이해는 아직도 완전히 규명되지 않고 있다. 고체 추진제의 연소 불안정에 대한 이론적 해석은 준-정상 1차원 해석(Quasi-Steady Homogeneous One-Dimension) 방법에 의하여 단순화된 지배방정식을 해석하는 것이 일반적으로 잘 알려져 있는 방법이다. 이 가정은 고체 추진제가 연수되는 영역을 두께가 매우 얇은 영역의 표면반응영역(surface reaction layer)과 화학반응이 없는 응축상태영역(condensed phase zone) 그리고 기체상태의 연료와 화염이 존재하는 기체상태영역(gas phase zone) 등의 3영역으로 구분하며, 기체상태영역에서 발생하는 교란에 대한 응축상태영역의 반응시간 크기(response time scale)가 매우 크기 때문에 응축상태영역의 반응은 준 정상적으로 일어난다고 가정하는 것이다.그러나, 연소실의 온도가 $3000^{\circ}K$ 정도의 높은 온도이어서 복사 열전달에 의한 고체 추진제의 가열이 중요한 열전달 방법으로 작용하게 되므로 이를 무시한 이론적 해석은 물리적인 중요성이 약하여질 수밖에 없다. 본 연구에서는 기체영역으로부터 전달되는 복사 열전달은 투명(transparent)한 표면반응영역을 통과하여 응축상태영역에서 모두 흡수되며 추진제 표면에서의 복사열방출(emission)을 고려하였다. 또한 연소불안정 현상을 해석하기 위하여 표면반응영역에서의 경계조건은 선형교란량으로 대치하는 Zn(Zeldovich-Novozhilov) 방법을 사용하였다. 이 방법은 기체상태영역에 대한 구체적인 해석없이도 연소불안정 현상을 해석할 수 있는 장점이 잇다. 즉 응축상태영역에서의 연소율과 표면온도는 각각 기체영역으로부터 전달되는 온도구배와 연소압력, 그리고 복사 열전달의 함수관계이므로 선형교란에 의한 추진제표면에서의 교란경계조건을 얻을 수 잇으며, 응축영역의 교란지배방정식과 함께 사용하여 압력교란과 복사 열전달의 교란에 대한 연소율의 교란 증감 여부를 판단하여 연소 불안정 현상을 해석할 수 있다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.4
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• pp.69-75
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• 2003

The ideal thrust function is used to determine the local thrust of supersonic combustor. Method of thrust determination from measured pressures are applied to the Mach 2.5 model supersonic combustor. In this application, measured pressures from the experiments in the University of Michigan are used to determine the local thrust of supersonic combustor. Marginal results of local thrust are obtained and discussed. Combustion and wedge affect thrust distributions in the upstream region significantly. The thrust determination from pressure measurements can be a simple, feasible and applicable method, especially when thrust stand is not available.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.117-120
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• 2005

The present study describes unsteady flow phenomena generated in a supersonic flow passing over a rectangular cavity and suggests a way of control of pressure oscillation, doing harm to overall performance and stable operation of aerodynamic and industrial applications. The three-dimensional, unsteady, compressible Navier-stokes equations are numerically solved based on a fully implicit finite volume scheme and large eddy simulation. The cavity flow are simulated with and without control methods, including a triangular bump and blowing jet installed near the leading edge of the cavity. The results show that the pressure oscillation is attenuated by both control techniques, especially near the trailing edge of cavity.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.1
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• pp.15-24
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• 1986

Pressure trasients must deal with safety problem of system. For identification of physical situation that can and method of limiting surges are essential consideration in sucessful design. The finite difference equation by method of characteristics are derived from the governing equation of unsteady flow in a pipe, and solved by using boundary condition derived. A computer program which can simulate general hydraulic system is developed by using finite difference equations and boundary conditions derived. The sumulated resulted by developed computer program are in fair agreement with experiment result.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.678-681
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• 2010

In the present work, a numerical study is conducted to investigate the effect of the transient nozzle pressure ratio (NPR) on the flow fields inside the nozzle. The unsteady, compressible, axisymmetric, Navier-Stocks equations with SST $k-{\omega}$ turbulence model are solved using a fully implicit finite volume scheme. In order to simulate the start-up and shut-down processes of the engine, NPR is varied from 2.0 to 10.0. It is observed that the interaction patterns and the hysteresis phenomenon strongly depend on the time variation of NPR, leading to significantly different characteristics in the lateral forces.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.369-374
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• 2010

This paper presents a numerical investigation of the Deflagration to Detonation Transition (DDT) of flame acceleration by a shock wave in combustible gas mixture. A model consisting of the reactive compressible Navier-Stokes equations is used. The effects of viscosity, thermal conduction, species diffusion, and chemical reactions are included. Using this model, the generation of hot spots by repeated shock and flame interaction in front and back of flame and the change of detonation occurrence by various shock intensities (Ms=1.1, 1.2, 1.3) are studied. The simulations show that as the incident shock intensity increases, the Richtmyer-Meshkov (RM) instability becomes stronger and DDT occurrence time is reduced.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.3
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• pp.33-40
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• 2001

In order to investigate the operating characteristics of a supersonic steam ejector, the axisymmetric, compressible, Reynolds-averaged, Wavier-Stokes computations are performed using a finite volume method. The secondary and back pressures of the ejector system with a second throat are changed to investigate their effects on the suction mass flow. Three operation modes of the steam ejector system, the critical mode, subcritical mode and back flow mode, are discussed to predict the critical suction mass flow. The present computations are validated with some experimental results. The secondary and back pressures of the supersonic steam ejector significantly affect the critical suction mass flow. The present computations predict the experimented critical mass flow with fairly good accuracy A good correlation is obtained for the critical suction mass flow. The present results show that provided the primary nozzle configuration and secondary pressure are blown, we can predict the critical mass flow with good accuracy.

• Aerospace Engineering and Technology
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• v.1 no.2
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• pp.51-56
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• 2002

Satellite propulsion system is employed for orbit transfer, orbit correction, and attitude control. The monopropellant feeding system in the low-earth-orbit satellite blowdowns fuel to the thrust chamber. The thrust produced by the thruster depends on fuel amount flowed into the combustion chamber. If the thruster valve be given on-off signal from on-board commander in the satellite, valve will be opened or closed. When the thrusters fire fuel flows through opened thruster valve, instantaneous stoppage of flow in according to valve actuation produces transient pressure due to pressure wave. This paper describes transient pressure predictions of the KOMPSAT-2 propulsion system resulting from latching valve and thrust control valve operations. The time-dependent set of the fluid mass and momentum equations are calculated by MOC.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.6
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• pp.29-35
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• 2021

Bell mouth inlet is applied in various industries due to the advantage of little pressure loss and accurate flow measurement. In this study, the configuration of the bell mouth intake is designed in a long radius shape, and a suitable grid size was selected to minimize the pressure drop and to prevent the engine damage by foreign objects at outdoor operating conditions. It was able to present a modified pressure drop coefficient equation from two data obtained from the computational simulation and experimental results for the total pressure loss by inlet screen installation.