• Proceedings of the KSME Conference
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• 2001.11b
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• pp.723-728
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• 2001

Wind flow perturbations, recirculations and turbulence generated by buildings often dominate air pollutant distributions around buildings. This paper describes dispersion of contaminants in the vicinity of a building by solving the concentration equation based on previously simulated wind flow field. Turbulence closure is achieved by using the standard k-e two-equation model. The paper shows application of the CIP method for solving a species concentration equation of contaminant gas around a rectangular building for two different sources under conditions of neutral atmospheric stratification. Results have been compared to the experimental data and the previous numerical results by hybrid scheme. The computational results of concentration profiles by the CIP method agree well with experimental data.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.4
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• pp.328-334
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• 1984

본 연구에서는 기하학적으로는 물론이며 유동 장체가 축대칭이 되고 재순환 영역이 있는 노즐을 제작하여 우선 연구의 1차 단계로서 연소가 없을 경우 시간 평균 유속 및 난류 성분을 레이져 도플러 유속계로 비교적 정밀히 측정한후, 노즐 유체와 주위공기류와의 시간 평균 혼합특성을 구명하기 위하여 가스크로마토그라프에 의하여 농도 분포를 측정, 모델 검토를 위한 기초 데이타 제공과 실험용으로 채용한 노즐류의 구조를 구명하고저 한다. 특히 노즐유체를 수소/질소 혼합기인 경우와 공기를 사용 한 양 경우를 비교, 검토하므로써 부력효과에 대한 평가를 시도하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.12
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• pp.1663-1673
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• 2002

In the present paper, flow and heat transfer characteristics of confined impinging slot jets have been numerically investigated using a SIMPLE-based segregated SUPG finite element method. For laminar jets, it is shown that the skin friction coefficient obtained from the present SUPG formulation approaches the grid-independent Galerkin solution inducing negligible false diffusion in the flow field when a moderate number of grid points are used. For turbulent jets, the k-$\omega$turbulence model is adopted. The streamwise mean velocity and the heat transfer coefficient respectively agree very well with existing experimental data within limited ranges of parameters.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.326-331
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• 2003

Combustion using oxygen enriched air is known as a technology which can increase flame stability as well as thermal efficiency due to improvement of the burning rate. Lift-off, blowout limit and flame length were examined as a function of jet velocity, coflow velocity and OEC(Oxygen Enriched Concentration). Blowout limit of the flame below OEC 25% decreased with coflow velocity, but the limit above OEC 25% increased inversely. Lift-off height decreased with increase of OEC. Especially lift-off hardly occurred in the condition above OEC 40%. Flame length of the flames above OEC 40% was increased until the blowout occurred. Flame stability became improved since lift-off and blowout limit increased much with increase of OEC.

• Water Engineering Research
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• v.1 no.3
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• pp.187-197
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• 2000

This paper describes an adaptive quadtree-based 2DH wave-current interaction model which is able to predict wave breaking, shoaling, refraction, diffraction, wave-current interaction, set-up and set-down, mixing processes (turbulent diffusion), bottom frictional effects, and movement of the land-water interface at the shoreline. The wave period-and depth-averaged governing equations are discretised explictly by means of an Adams-Bashforth second-order finite difference technaique on adaptive hierarchical staggered quadtree grids. Grid adaptation is achieved through seeding points distributed according to flow criteria(e.g. local current gradients). Results are presented for nearshore circulation at a sinusoidal beach. Enrichment permits refined modelling of important localised flow features.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.24-33
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• 1999

This paper investigate the effects of the variations of engine operation condition in the flame kernel formation and developmnet . A model for calculating the initial kernel development in spark ignition engines is formualted. It considered input of electrical energy, combustion energy release and heat transfer to the spark plyg, cylinder head, and unburned mixture. The model also takes into accounts strain rate of initial kernel and residual gas fraction. The breakdown process and the subsequent electrical power input initially control the kernel growth while intermediate growth is mainly dominated by diffusion or conduction. Then, the flame propagates by the chemical energy and turbulent flame expansion. Flame kernel development also influenced by engine operating conditions, for example, EGR rate, air-fuel ration and intake manifold pressure.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1328-1333
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• 2004

The Flame length of $CH_4$ with the Oxidizer of air and $O_2$ has been measured respectively for the nozzle diameter of 1.6mm, 2.7mm, 4.4mm and 7.7mm. In all $CH_4$ flame on oxidizer of air and $O_2$. the flame length was independent of the initial jet diameter, dependent only on the flowrate in laminar flame regime, and in turbulent flame dependent on the initial jet diameter. Using correlation equation of Delichatsios, the flame length has been expected exactly for $CH_4/air$ flame, but has been underestimated for $CH_4/O_2$ flame. This paper has proposed correlation equation of $CH_4/O_2$ flame.

• Proceedings of the KAIS Fall Conference
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• 2001.05a
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• pp.290-291
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• 2001

The relationship between velocity, viscosity, diffusion coefficient, mass transfer coefficient and characteristic length and mass transfer data can be correlated by dimensionless relationship in electrolytic process. The performance of dyestuff removal was decreased as the flow rate of electrolyte was increased. It was due to the effect of retention time decreasing was superior to that of turbulent inlet mixing. Sh/Sc$\^$1/3/ vs Re plot for Al flat electrode did not showed the general tendency of the relationship between Sh/Sc$\^$1/3/ and Re. It can be thought that flow rate was not sufficiently high to increase the effect of mixing.

• 연구논문집
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• s.31
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• pp.23-43
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• 2001

An experimental investigation on the reduction of nitrogen oxide emission from swirling, turbulent diffusion flames was conducted using multi air staged combustor, The combustor utilizes swirler to dampen fuel/air mixing, allowing an extended residence time for fuel pyrolysis and fuel-N conversion chemistry in an locally fuel-rich environment prior to burnout. This process also allow to reduce thermal NOx formation to lessen the temperature of reaction zone. The aerodynamic process therefore emulates the conventional staged combustion process, but without the need for the physically separate fuel-rich and -lean stages. Parametric studies on the ratios of each staged air and droplet size were carried out the feasibility of fuel/air mixing for low NOx combustion with diesel and pyridine mixed diesel fuel oil.

• Journal of Energy Engineering
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• v.22 no.4
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• pp.399-405
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• 2013

The gas motion inside the engine cylinder plays a very important role in determining the thermal efficiency of an internal combustion engine. A precise information of in-cylinder three dimensional complex gas motion is crucial in optimizing engine design. Homogeneous charge compression ignition (HCCI) engine is a combustion concept, which is a hybrid between Otto and Diesel engine. The turbulent diffusion leads to increased rates of momentum, heat and mass transfer. The in-cylinder turbulence flow was found to affect the present HCCI combustion mainly through its influence on the wall heat transfer. This study investigates the effect of piston geometry shape on the turbulent flow characteristics of in-cylinder from the numerical analysis using the LES model and the results obtained can offer guidelines of the combustion geometries for better combustion process and engine performance.