• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.57-61
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• 2003

In the combustion modeling of non-premixed flames, the mixture fraction conserved scalar approach is widely utilized because reactants are mixed at the molecular level before burning and atomic elements are conserved in chemical reactions. In the mixture fraction approach, combustion process is simplified to a mixing problem and the interaction between chemistry and turbulence could be modelled by many sophisticated combustion models including the flamelet model and CMC. However, most of the mixture fraction approach is restricted to one mixture system. In this study, the flamelet model based on the two-feed system is extended to the multiple fuel-feeding systems by the two mixture fraction conserved scalar approach.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.468-470
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• 2007

This paper is to present an approach for generating coarse resolution (MODIS data) fraction images of forested region in Korea peninsula using forest type area fraction derived from high resolution data (ASTER data) in regional forest area. A 15-m spatial resolution multi-spectral ASTER image was acquired under clear sky conditions on September 22, 2003 over the forested area near Seoul, Korea and was used to select each end-member that represent a pure reflectance of component of forest such as different forest, bare soil and water. The area fraction of selected each end-member and a 500-m spatial resolution MODIS reflectance product covering study area was applied to a linear mixture inversion model for calculating the fraction image of forest component across the South Korea. We found that the area fraction values of each end-member observed from high resolution image data could be used to separate forest cover in low resolution image data.

• 품질경영학회지
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• 제39권3호
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• pp.400-411
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• 2011

Process variables are factors in an experiment that are not mixture components but could affect the blending properties of the mixture ingredients. For example, the effectiveness of an etching solution which is measured as an etch rate is not only a function of the proportions of the three acids that are combined to form the mixture, but also depends on the temperature of the solution and the agitation rate. Efficient designs for the mixture components-process variables experiments depend on the mixture components-process variables model which is called a combined model. We often use the product model between the canonical polynomial model for the mixture and process variables model as a combined model. In this paper we propose three starting models for the mixture components-process variables experiments. One of the starting model we are considering is the model which includes product terms up to cubic order interactions between mixture effects and the linear & pure quadratic effect of the process variables from the product model. In this paper, we propose a method for finding robust designs and practical designs with respect to D-, G-, and I-optimality for the various starting combined models and then, we find practically efficient and robust designs for estimating the regression coefficients for those models. We find the prediction capability of those recommended designs in the case of three components and three process variables to be good by checking FDS(Fraction of Design Space) plots.

• 설비공학논문집
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• 제5권1호
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• pp.35-43
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• 1993

A numerical model for the solidification of binary mixture is proposed. Numerical model, which employs enthalpy method, is modified from Continuum model, that is, improved relation is proposed for the Enthalpy - Temperature - Concentration - Liquid Mass Fraction. One dimensional example was selected to verify the proposed model. The results show that the new relation can be applied successfully to the solidification or melting of binary mixture.

• 한국안전학회지
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• 제28권6호
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• pp.6-10
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• 2013

A numerical reproducibility of the backdraft phenomena in a compartment was investigated. The prediction performance of two combustion models, the mixture fraction and finite chemistry models, were tested for the backdraft phenomena using the FDS code developed by the NIST. The mixture fraction model could not predict the flame propagation in a fuel-air mixture as well as the backdraft phenomena. However, the finite chemistry model predicted the flame propagation in the mixture inside a tube reasonably. In addition, the finite chemistry model predicted well the backdraft phenomena in a compartment qualitatively. The flame propagation inside the compartment, fuel and oxygen distribution and explosive fire ball behavior were well simulated with the finite chemistry model. It showed that the FDS adopted with the finite chemistry model can be an effective simulation tool for the investigation of backdraft in a compartment.

• 대한원격탐사학회지
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• 제23권6호
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• pp.537-546
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• 2007

초분광영상의 분석 기법 중 하나인 선형혼합분석기법은 각 화소를 구성하는 구성물질과 구성 비율을 추정하는데 매우 유용하게 사용되고 있다. 선형혼합모델은 지질 및 광물분포와 관련된 분야에서는 비교적 성공적으로 시도되고 있으나, 산림이나 여러 인공물들로 구성된 도시와 같은 상대적으로 복잡한 구조를 가진 혼합체에서는 그 정확도가 떨어진다. 본 연구에서는 식물과 토양의 혼합체를 대상으로 선형혼합모델을 적용하여 계산된 혼합체의 반사값과 실제 이 혼합체들을 분광측정기로 측정한 반사값과의 비교를 통해, 선형혼합모델의 오차를 계산하였다. 이를 통해 선형혼합모델의 오차 원인인 구성 물질간의 분광적 상호작용이 어느 경우 발생 혹은 증가하는지를 분석하고, 또한 파장대별 상호작용의 정도 차이가 있는지를 분석하였다. 연구 결과, 선형혼합모델은 혼합체를 구성하는 구성물질의 구성비율이 비슷한 경우, 각 구성 물질간의 상호작용이 증가하여 선형혼합모델의 오차가 가장 커지는 것을 알 수 있었다. 결과적으로 선형혼합모델의 오차 원인인 구성 물질간 상호작용의 발생 정도는 혼합체를 구성하는 성분의 종류, 반사 특성, 구성비율, 파장대와 구성 성분의 배열 상태에 따라 다르게 나타나는 것을 알 수 있었다. 향후 선형혼합모델의 정확도를 높이기 위해서는 이러한 혼합체의 특징들이 구성 물질간의 상호작용에 끼치는 영향을 정량적으로 분석하여야 할 것이다.

• 한국자동차공학회논문집
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• 제5권5호
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• pp.51-66
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• 1997

A heat transfer model of the intake valve in a spark ignition engine is presented, which is calibrated with a number of the valve temperature profiles measured during engine warm-up for the gaseous fuel(propane). The valve is divided into four identical elements for which the assumption of lumped thermal mass is applied. The calibration is made so that the difference between the measued and simulated valve temperatures becomes minimal. Then the model is applied to the cases of the liquid fuel(indolene) to estimate the amount of the liquid fuel vaporized from the intake valve by assuming that fuel evaporation accounts for the deficit of the heat balance budget. The results of the model show quantitative contribution of each heat transfer source to the heat balance. The behavior of the calculated mass fraction of the fuel vaporized from the intake valve explains how the liquid fuel evaporate during engine warm-up. The mass fraction at warmed-up condition is closely related with the fraction directly targeted on the valve back by the fuel spray geometry.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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• pp.118-125
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• 2007

The firtst-order conditional moment closure (CMC) model is applied to CH4/air swirl diffusion flame in a gas turbine model combustor. The flow and mixing fields are calculated by fast chemistry assumption with SLFM library and a beta function pdf for mixture fraction. RNG k-e model is used to consider the swirl flame in a confined wall. Reacting scalar fields are calculated by elliptic CMC formulation with chemical kinetic mechanism, GRI Mech 3.0. Validation is done against measurement data for mean flow and scalar fields in the model combustor [1]. Results show reasonable agreement with the mean mixture fraction and its variance, while temperature is overpredicted as the level of local extinction increases. The second-order CMC model is needed to consider local extinction with considerable conditional fluctuations near the nozzle.

• 한국연소학회지
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• 제15권4호
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• pp.15-21
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• 2010

The transported probability density function(PDF) model has been applied to simulate the turbulent nonpremixed piloted jet flame. To realistically account for the mixture fraction PDF informations on the turbulent non-premixed jet flame, the present Lagrangian PDF transport approach is based on the joint velocity-composition-turbulence frequency PDF formulation. The fluctuating velocity of stochastic fields is modeled by simplified Langevin model(SLM), turbulence frequency of stochastic fields is modeled by Jayesh-Pope model and effects of molecular diffusion are represented by the interaction by exchange with the mean (IEM) mixing model. To validate the present approach, the numerical results obtained by the joint velocity-composition-turbulence frequency PDF model are compared with experimental data in terms of the unconditional and conditional means of mixture fraction, temperature and species and PDFs.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.775-778
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• 2007

The present study numerically investigate the detailed structure of the syngas diffusion flames. In order to realistically represent the turbulence-chemistry interaction, the transient flamelet model has been applied to simulate the combustion processes and $NO_X$ formation in the syngas turbulent nonpremixed flames. The single mixture fraction formulation is extended to account for the effects of the secondary inlet mixture. Computations are the wide range of syngas compositions and oxidizer dilutions. Based on numerical results, the detailed discussion has been made for the effects of syngas composition and oxidizer dilution on the structure of the syngas-air and syngas-oxygen turbulent nonpremixed flames.