• Journal of the Society of Naval Architects of Korea
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• v.32 no.2
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• pp.75-83
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• 1995

As a basic research for the automation of plate forming process, the theoretical aspect of plate bending by line heating was surveyed and numerical simulation of plate bonding deformation was performed using the 3-dimensional nonlinear transient thermal elasto-plastic finite element analysis. Analyzing the unsteady heat conduction problem of the flat steel plate under heat flux input by gas torch, the time history of 3-dimensional thermal distribution was obtained. Transient thermal deformation process of the plate was analyzed under the thermal loading. And the calculated results are investigated in detail.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.2
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• pp.152-159
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• 2018

A numerical simulation was conducted to establish the analysis methods of the unsteady conjugated heat transfer with a hot gas valve. Two methods are proposed to reduce the computational cost and analysis time of the unsteady conjugate heat transfer; namely, the multi-section analysis method and the one-way analysis method. The multi-section analysis method exhibits relatively high reliability. In the one-way analysis method, the unsteady conjugate heat transfer from the fluid domain to the solid domain was simulated from the analysis results of the steady-state flowfield. The incipient accuracy of the analysis results obtained by the one-way analysis method was slightly lower than that of the results obtained by the multi-section analysis method. However, the discrepancy became smaller with time, as the analysis progressed.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.517-518
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• 2006

Transient and asymmetric density distributions have been investigated by three-dimensional digital speckle tomography with a novel integration method. Multiple CCD images captured movements of speckles in three angles of view simultaneously because the flows were asymmetric and unsteady. The speckle movements which have been formed by a ground glass between no flow and downward butane flow from a circular half opening have been calculated by a cross-correlation tracking method so that those distances can be transferred to deflection angles of laser rays for density gradients. A novel integration method has been developed to obtain projection data from the deflection angles for the speckle tomography.'The three-dimensional density fields have been reconstructed from the accurate projection values by a real-time multiplicative algebraic reconstruction technique (MART) with the developed integration method.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.11
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• pp.2169-2180
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• 1992

Solid propellant combustion is investigated for its response to several imposed pressure histories. For this purpose, it is assumed that combustion takes place in a premixed gas evaporated from a uniform melt of solid propellant. One-dimensional unsteady problem is than numerically solved for a pressure coupling, with a steady state as an initial state. The results in response to pressure of finite sinusoidal waves show that unsteady mass fluxes are sometimes quite different from those predicted by the classical quasisteady burning law of Vieile. In addition, abnormal mass flux excursions are captured for a large pressure exponent and a lower melting point.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.705-710
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• 2004

In the present study, a transient incompressible viscous turbulent flow is simulated for the automotive torque converter with moving mesh technique. For the analysis, entire torque converter flow passages are modeled. Computed torque ratio, capacity factor and efficiency show a good agreement with the experiment data. The flow instabilities characterized by back-flow and wake etc. appeared in some cascade passages are shown to be Propagating along tangential direction. These flow patterns are mainly influenced by the pump and turbine blade passing and can't be predicted through conventional steady simulation with a mixing plane approach. The understanding of the unsteady flow characteristics in a torque converter achieved in the present study may lead to the optimal design of a torque converter.

• The KSFM Journal of Fluid Machinery
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• v.9 no.5 s.38
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• pp.36-41
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• 2006

In the present study, a transient incompressible viscous turbulent flow is simulated for the automotive torque converter with moving mesh technique. For the analysis, entire torque converter flow passages are modeled. Computed torque ratio, capacity factor and efficiency show a good agreement with the experiment data. The flow instabilities characterized by back-flow and wake etc. appeared in some cascade passages are shown to be propagating along tangential direction. These flow patterns are mainly influenced by the pump and turbine blade passing and can't be predicted through conventional steady simulation with a mixing plane approach. The understanding of the unsteady flow characteristics in a torque converter achieved in the present study may lead to the optimal design of a torque converter.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.6
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• pp.769-777
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• 1999

This paper presents models for the dynamic simulation of a regenerative gas turbine and describes dynamic behaviors of a small regenerative engine. A quasi-steady model is introduced where the inertia of the working fluid is assumed to be negligible compared with the mechanical inertia of the rotating shaft. Based on this quasi-steady model, the transient model for the heat exchanger is employed to simulate the unsteady heat exchange in the recuperator. The effect of the thermal inertia of the recuperator metal on transient behaviors is analyzed by comparing the predicted results of the transient and steady state heat exchanger models. For several load change modes such as sudden increase, decrease and periodic variation, engine dynamic characteristics are investigated by applying a fuel control logic for the constant shaft speed. It is found that the thermal inertia of the recuperator metal has a dominant effect on the whole engine dynamic behavior.

• Tribology and Lubricants
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• v.22 no.1
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• pp.47-52
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• 2006

It is very important to control pressure and flow rate distribution on each component of engine lubrication network. Sometimes many kinds of orifice are used to control flow rate in the hydraulic lubrication field. In this study orifices were adopted on the lubrication network to control oil flow rate distribution. And unsteady transient flow network analysis was carried out to find out the effects of orifices on the engine oil circuit system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1995.11a
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• pp.139-144
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• 1995

The main purpose of igniter is sure ignition of main propellant at desired ignition delay times. Since ignition mechanism of solid rocket propellant involves so many complicated physical and chemical phenomena, it is almost impossible to predict ignition behavior with pure analytical means. In this study, one dimensional and unsteady ignition transient phenomena in solid rocket was analyzed by finite volume method. In analysis, assumption was made that ignition occurs when propellant surface temperature reaches to it's auto-ignition temperature.

• International Journal of Aeronautical and Space Sciences
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• v.7 no.2
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• pp.110-120
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• 2006

There have been developed many structural and fluid rotorcraft analysis models in rotorcraft community, and also lots of investigations have been conducted to combine these two models. These investigations turn out to be good at predicting the airloads precisely, but they have not taken the blade nonlinear deflection into account. For this reason, the present paper adopts a sophisticated structural model which can describe three-dimensional nonlinear deflection of the blade. And it is combined with two types of aerodynamic model. First one is generalized Greenberg type of finite-time aerodynamic model, which is originally established for a fixed wing, but later modified to be suitable for coupled flap-lag-torsional aeroelastic analysis of the rotor blade. Second aerodynamic model is based on the unsteady source-doublet panel method coupled with a free wake model. The advantages of the present method are capabilities to consider thickness of the blade and more precise wake effects. Transient responses of the airloads and structural deflections in time domain are mainly analyzed in this paper.