• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.113-119
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• 2001

Interaction of flow through an Impeller and a Vaned Diffuser in Centrifugal Compressor was investigated using the 3-dimensional Wavier-Stokes solution method. To consider the interaction effect of impeller and vaned diffuser, Inlet boundary conditions are imposed with the results of the steady calculation of the impeller and rotates with time. The results have been compared to steady computation results and experiment. From this, it is discussed about the compatability of the method and the advantage and disadvantage of the steady calculation.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.11a
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• pp.130-134
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• 2001

In the re-entry control system, errors apt to induce because the time derivative of drag acceleration is analytically estimated. Still more, the difficulty of estimation of the exact drag coefficient in hypersonic velocity and the nun-reality of the scale height cause a steady-state drag error. This paper proposes the additional method of the disturbance observer. This reduces the steady-state drag error according to the following series. First, this method estimates a error in drag acceleration time derivative by the analytic calculation and then creates the new drag acceleration time derivative using the estimated error. The performance of the re-entry control system is verified about 32 reference trajectories.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.4
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• pp.34-43
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• 2001

Analysis and control of intake charge motion such as swirl and tumble are very important to improve the performance of gasoline engines. In this paper, single frame double exposure PTV(particle tracking velocimetry) is used to investigate intake flow characteristic in a steady flow test rig of gasoline engine with 2-valve and pent-roof combustion chamber. To validate this PTV method, we confirmed reliability of this PTV method using chopper, and coaxial burner experiments. The velocity Held of intake flow is measured with the intake valve lift variation. It is shown that maximum flow velocity is increased and tumble flow become stronger than inverse tumble flow as valve lift increase.

• The KSFM Journal of Fluid Machinery
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• v.5 no.2 s.15
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• pp.43-49
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• 2002

In this paper, the steady-state performances analysis of a tilting pad gas bearing(TPGB) we analyzed by using finite element method for compressible Reynolds' equation. TPGB is used in a high-expansion-ratio expander running at a speed of 230,000 rpm. In order to solve the nonlinear finite element equations, the Newton-Raphson method is applied. The variations of the loading capacity, friction force and tilting angle of a single pad v.s. eccentricity direction of eccentricity and bearing number are investigated. The condition for the equilibrium of a pad, which is important for safe working of the bearing, is stated. The performances of the three pad bearing such as loading capacity, friction moment are predicted.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.465-470
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• 2001

This paper presents an algorithm which seeks steady-state equilibrium positions of constrained multibody systems driven by constant generalized speeds. Since the relative coordinates are employed, the constraint equations at cut joints are incorporated into the formulation. The proposed algorithm leads to nonlinear equations that need to be solved iteratively. This algorithm should satisfy both types of conditions: the force equilibrium equations and the kinematic constraint equations. To verify the effectiveness of the proposed algorithm, two numerical examples are solved and the results are compared with those of a commercial program. This method, compared to the conventional method of using dynamic analysis, has the advantage of computational efficiency and stability.

• Journal of Environmental Science International
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• v.4 no.1
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• pp.71-80
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• 1995

A discrete state space model for a multiple-reach river system is formulated using the dynamics of biochemical oxygen demand(BOD) and dissolved oxygen(DO). A hierarchical optimization technique, which is applicable to large-scale systems with time-delays in states, is also described to control stream quality in a river as an optimal manner based on the interaction prediction method. The steady state tracking error of the proposed method is determined analytically and a necessary and sufficient condition on which a constant target tracking problem has zero steady-state error is derived. Computer simulations for the river pollution model illustrate the algorithm.

• Journal of Environmental Science International
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• v.17 no.9
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• pp.957-968
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• 2008

The purpose of this study is to analyze the characteristics of hydraulic behavior of the natural channel flow according to the temporal classification mode, and thus propose the hydraulic analysis method for future channel design. For analysis, the temporal flow characteristics of the channel section was divided into the steady flow and the unsteady flow. For hydraulic analysis, the HEC-RAS model, which is a one-dimensional numerical analysis model, and the SMS-RAM2 model, which is a two-dimensional model, were used and the factors used for analysis of hydraulic characteristics were flood elevation and flow rate. The flow state was analyzed on the basis of the one-dimensional steady flow and unsteady flow for review. In the unsteady flow analysis the flow rate changed by $(-)0.16%{\sim}(+)0.26%$, and the flood elevation varied by $(-)0.35%{\sim}(+)0.51%$ as compared to the values in the steady flow analysis. Given these results, in the one-dimensional flow analysis based on the unsteady flow the flood elevation and flow rate were greater than when the analysis was done on the basis of the steady flow. The flow state was analyzed on the basis of the two-dimensional steady flow and unsteady flow. In the unsteady flow analysis the flow rate varied by $(-)0.16%{\sim}(+)1.08%$, and the flood elevation changed by $(-)0.24%{\sim}(+)0.41%$ as compared to the values in the steady flow analysis. Given these analysis results, in the two dimensional flow analysis based on the unsteady flow, the flood elevation and flow rate were greater than when the analysis was done on the basis of the steady flow.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.217-218
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• 2002

An integrated adhesive wear model was proposed to determine the transient wear and steady-state wear of aluminium alloy matrix composites. The transient wear volume was described by an exponential equation, while the steady-state wear was governed by a revised Archard equation, in which both the transient wear volume and transient sliding distance were excluded. A mathematical method was developed to determine both the transient distance and the net steady-state wear coefficient. Experimental wear tests were carried out on three types of commercial A6061 aluminum alloy matrix composites reinforced with 10%, 15% and 20% alumina particles. More accurate wear coefficient values were obtained with the proposed model. The average standard wear coefficient, as determined by the original Archard equation, was found to be about 51% higher.

• Journal of the Korea Furniture Society
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• v.20 no.6
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• pp.599-604
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• 2009

For the search of unified law of moisture movement in wood, moisture distribution of Korean red pine at non-steady state was investigated. We assume that the equilibrium moisture content (EMC) in wood depends on only temperature and relative humidity, it can be control in temperature and humidity chamber. If temperature is constant and humidity or vapor pressure is changed with sin curve shape at adequate cycles, EMC in chamber can be changed as well with sin-curve shape. The setup condition of a non-steady state in humidity control chambers is a constant temperature at $20^{\circ}C$ and 15+10 sin ${\omega}t$ percent EMC. It can be found that the distribution of moisture in the specimen with varying relative humidity are illustrated various types. Moisture in wood is complicated and vibrates with the moisture sorption process. Considering a unified law of moisture movement in wood, it is considered that the most important fact is to search the method of precise diffusion & transfer coefficients.

• Transactions of Materials Processing
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• v.25 no.1
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• pp.56-60
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• 2016

Precise prediction and control of the strip profile is crucial for automatic process set-up and operation of a hot strip mill. In the current study, we present the effect of post-deformation on the steady-state strip profile. The process was simulated by a 3-D elastic-plastic finite element (FE) analysis. Comparisons are made between the strip profile measured at the roll exit and the steady-state strip profile. The results raised an issue with regard to the importance of taking into account the effect of post-deformation.