• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.3-10
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• 2002

In this work, numerical parametric studies on spray combustion have been conducted. In simulation of turbulence, RNG ${\kappa}-{\varepsilon}model$ is adopted. Initial spray distribution is specified by Rosin-Rammler distribution function. Eddy break-up model is adopted as a combustion model. The parameters considered are inlet air temperature, swirl number, and SMD. With higher inlet air temperature, the axial velocities are increased and penetration of primary jet is stronger than that of lower inlet air temperature and temperature at the exit of combustor is more uniform. Combustion efficiency is improved with high inlet air temperature. The effect of swirl number on flow field is not significant. It affect only recirculation zone. So temperature at upstream of combustor is influenced. Combustion efficiency deteriorate as SMD of fuel spray increase.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.3
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• pp.89-95
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• 2002

This paper describes a new identification method for friction in motion control systems, in which the friction model is not necessarily linear in parameters. The proposed method works well with any measurement data of velocity and input control force, as long as the initial and final velocities are identical. Most importantly, the proposed method does not require the information of acceleration for its implementation, in contrast with the previously known methods. This is due to the orthogonality property between acceleration and a function of velocity. In particular, if the parametric model is linear in parameters, its friction parameters can be identified in closed form without resorting to numerical search methods. To illuminate further the generality and practicality of the proposed friction identification method, we show good performance of the proposed method through some simulation results.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.169-175
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• 2000

A design method for transonic turbine blades is developed based on Navier-Stokes equations. The present computing process is done on the four separate steps, 1.e., determination of the blade profile, generation of the computational grids, cascade flow simulation and analysis of the computed results in the sense of the aerodynamic performance. The blade shapes are designed using the cubic polynomials under the control of the design parameters. Numerical methods for the flow equations are based on Van-Leer's FVS with an upwind TVD scheme on the finite volume. Applications are made to the VKI transonic rotor blades. Computed results are analyzed with respect to the aerodynamic performance and are compared with the experimental data.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.1
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• pp.84-90
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• 2004

In order to evaluate the performance of carbon dioxide cycle, a simulation model was developed to predict the steady state performance of $CO_2$ transcritical cycle. The expansion process is treated as an isenthalpic throttling process or isentropic expansion process. The mathematical model is based entirely on the basic energy conservation law and thermodynamic and transport properties of $CO_2$. A Parametric study has been conducted in order to investigate the effect of isentropic efficiency of expansion turbine and various operating conditions on the cycle performance. An optimal heat rejection pressure existed for the given evaporating temperature and outlet temperature of gas cooler.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1269-1274
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• 2014

Due to the presence of Dean flow in curved ducts, helical channels have drawn attention recently because of the practical industrial applications. The manipulation of fluids through microfluidic devices is widely used in many scientific and industrial areas. In the present study, numerical simulations were performed on a helical microchannel to predict the impact of different design parameters that affect Dean flow. Important geometric parameters such as the channel cross section, pitch, radius of curvature, and number of turns were considered for the analysis. The study also incorporates the effect of varying flow rate on Dean flows. It was found from the simulation results that microchannel cross section and pitch have a significant impact on maintaining the Dean flow, compared to the radius of curvature, number of turns, and flow rate.

• Communications for Statistical Applications and Methods
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• v.19 no.6
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• pp.885-898
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• 2012

In this paper, we consider Bayesian approaches to partially linear models, in which a regression function is represented by a semiparametric additive form of a parametric linear regression function and a nonparametric regression function. We make a comparative study on the performance of widely used Bayesian partially linear models in terms of empirical analysis. Specifically, we deal with three Bayesian methods to estimate the nonparametric regression function, one method using Fourier series representation, the other method based on Gaussian process regression approach, and the third method based on the smoothness of the function and differencing. We compare the numerical performance of three methods by the root mean squared error(RMSE). For empirical analysis, we consider synthetic data with simulation studies and real data application by fitting each of them with three Bayesian methods and comparing the RMSEs.

• Transactions of Materials Processing
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• v.20 no.8
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• pp.555-561
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• 2011

The energy absorbing characteristics of crash members in a car collision play an important role in controlling the amount of damage to the passenger compartment. Crash members filled with aluminum foam are expected to have reduced mass while maintaining or even improving the crashworthiness compared to the conventional hollow-beam types. Finite element simulations are carried out in the present work to assess the improvement of crashworthiness by the use of aluminum foam fillers. The numerical results agreed well with experimental measurements. Parametric studies are conducted to analyze the effect of impact velocity, weld strength, and initiator on the crash response.

• Journal of the korean Society of Automotive Engineers
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• v.4 no.2
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• pp.58-68
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• 1982

It is well known to diesel engineers that the heat release pattern is one of the most important factors affecting engine performance. Thorough research in heat release pattern has materially helped the progress in high-speed diesel engine development . This paper is based on the research conducted at KAIST and Daewoo Heavy Industry last year. The purpose of this paper is to determine the heat release pattern in combustion chamber of MAN M type, the famous low-noise engine. Thermodynamic cycle simulation was performed using Whitehous-Way's heat release pattern with modified coefficients and Annand's heat transfer model. Instantaneous temperature and pressure of gas in cylinder could be determined by the numerical solution of simultaneous equation of mass conservation, equation of energy conservation, and state equation of ideal gas. Calculated results were compared with measured values in some details emphasizing upon the factors affecting rate of heat release. The agreement was fairly good and revealed why M type should have lower burning velocity at the early part of combustion in spite of high injection rate. Additional results by parametric studies were given in relation to fuel injection conditions for further application to engine development.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.6
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• pp.665-674
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• 2000

A major source of the hazardous waste generated is from chemical industries producing plastics, herbicides, pesticides and chlorinated solvents. All of these processes produce a class if hazardous waste termed the chlorinated hydrocarbons(CHCs), either directly or from undesirable side reactions. In this study, we investigated the destruction characteristics of hazardous waste through incineration. A nonequilibrium combustion model was used to describe the effect of the chemical kinetics due to the flame inhibition characteristics of $CCl_4$ which was used as the surrogate of hazardous waste. A parametric screening studies was made in a dump incinerator proposed in this study. The dump incinerator showed high $CCl_4$ DRE(Destruction and Removal Efficiency) as 5 nines. $CCl_4$/CH$_4$ ratio appeared to be most important in the destruction of $CCl_4$ through incineration.

• Journal of ILASS-Korea
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• v.12 no.4
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• pp.191-197
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• 2007

This study presents in-line digital particle holography and its application to spray droplets to measure the characteristics of spray droplets. Several important parameters at the time of hologram recording such as the object distance and the region of laser beam used were verified. The correlation coefficient method with important parameters such as the reconstruction interval and the correlation interval was used for determination of the focal planes of particles. The optimal values of all these parameters are obtained by either numerical simulation of holograms or experiments. Using these optimal parameters, double pulse digital spray holograms in a short time interval were recorded with the synchronization system for the time control. The spatial positions of droplets that are used for the evaluation of the three dimensional droplet velocities can be easily located, which proves the feasibility of the digital holographic technology for measurements of several important features of spray droplets.