• Journal of Welding and Joining
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• v.25 no.3
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• pp.64-71
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• 2007

The dissolution phenomenon of the solid phase powder and base metal by liquid phase insert metal during Transient Liquid Phase bonding using the mixed powder composed of the modified GTD111(base metal) powder and the GNi3 (Ni-l4Cr-9.5Co-3.5Al-2.5B) powder was investigated. In case of the mixed powder contains modified GTD111 powder 50wt%, all of the powder was melted by liquid phase at 1423K. At the temperature between solidus and liquidus of GNi3, liquid phase penetrated into the boundary of the modified GTD111 powder and solid particle separated from powder was melted easily because area of reaction was increased. With increasing mixing ratio of the modified GTD111, it needed the higher temperature to melt all of the modified GTD111 powder. During Transient Liquid Phase bonding using the mixed powder composed of the modified GTD111 50wt% and GNi3 50wt% as insert metal, width of the bonded interlayer was increased with increasing bonding temperature by reaction of the base metal and liquid phase in insert metal. Dissolution of the base metal and modified powder by liquid phase progressed all together and after all of the powder was melted nearly, the dissolution of the base metal occurred quickly.

• Journal of Energy Engineering
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• v.22 no.1
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• pp.28-37
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• 2013

Stirred tank is widely used in various industries for mixing operations and chemical reactions for single- or multi-phase fluid systems. For designing agitator of high performance, quantity data of internal flow characteristics influenced by mixing performance are definitely confirmed but quantity analysis about the transient flow characteristics of complicate structure is recognized as difficult problem in the present. In this study, two models of commercial CFD code Fluent 6.3 used to propose suitable for the tank analysis. Agitation of Stirred tank is analyzed using a mixed model and the flow in the stirred tank is analyzed using a standard k-${\varepsilon}$ model. Multiple reference frame(MRF) and Sliding mesh(SM), the analysis techniques were used For compare a result of CFD with a visualization experiment result, to grasp internal flow and mixing characteristic in stirred tank and to present fundamental analysis method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.3
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• pp.350-357
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• 1997

The transient incompressible flow behind the axisymmetric bluff body is numerically simulated using the random vortex method(RVM). Based on the vorticity formulation of the unsteady Navier-Stokes equations, the Lagrangian approach with a stochastic simulation of diffusion using random walk technique is employed to account for the transport processes of the vortex elements. The numerical solutions for 2-dimensional recirculating flow behind a backward-facing step in the laminar range of Reynolds number are compared with experimental data. The present simulation focuses on the transitional flow regime where the recirculation zone behind the bluff body becomes highly unsteady and large-scale vortex eddies are shed from the bluff body wake due to intrinsic shear layer instabilities. The unsteady vertical flow structures and the mixing characteristics behind the bluff body are discussed in detail.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.5
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• pp.114-122
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• 1997

Nowadays, gasoline direct injection engines are being commercialized by virtue of improvement in control technology of spray, flow, air fuel ratio. The stratified charge type has the advantage of improving lean limit. The homogeneous type has the advantage of reducing engine-out hydrocabon emissions in the first 30 seconds after a cold start, in addition, improving transient air fuel ratio control. The vaporization and mixing if injected fuel with air has to e completed in a short time and the fuel film in cylinder and on piston has to be minimized. So, the flow and injection should be well controlled. This paper surveyed the spray characteristics of gasoline direct injection by using laser equipment and the combustion characteristics of the single cylinder engine using homogeneousas-mixture type gasoline direct injection.

• International Journal of Automotive Technology
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• v.5 no.3
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• pp.165-172
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• 2004

Phenomenological models for direct injection diesel engine emissions including NO, soot, and HC were implemented into a full engine cycle simulation and validated with experimental data obtained from representative heavy-duty DI diesel engines. The cycle simulation developed earlier by Jung and Assanis (2001) features a quasi-dimensional, multi-zone, spray combustion model to account for transient spray evolution, fuel-air mixing, ignition and combustion. In this study, additional models for HC emissions were newly implemented and the models for NO, soot, and HC emissions were validated against experimental data. It is shown that the models can predict the emissions with reasonable accuracy. However, additional effort may be required to enhance the fidelity of models across a wide range of operating conditions and engine types.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.50-54
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• 2002

With a view to estimating the effect of flows on evolving sprays and combustion in ramjet combustor and corresponding extent of combustion, ram air flows in combustion chamber is numerically experimented. Preconditioned three dimensional Navier-Stokes system of equations per transient, compressible, turbulent flows in IRR(Integral Rocket Ramjet) combustor is numerically integrated. Flow properties in the side-dump ramjet combustor, rectangular duct with two 60-deg curved inlets located radially at an angle of 180-deg, are addressed in terms of mixing quality and extent of combustion efficiency.

• 한국전산유체공학회:학술대회논문집
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• 1995.10a
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• pp.246-252
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• 1995

The transient incompressible flow behind the bluffbody is numerically simulated using the random vortex method(RVM). Based on the vorticity formulation of the unsteady Navier-Stokes equations, the Lagrangian approach with the random walk technique is employed to account for the transport processes of the vortex elements. The random walk procedure for the diffusion process has been validated against the exact solutions. The present simulation focuses on the transition flow regime where the recirculation zone behind the bluffbody becomes highly unsteady and large-scale vortex eddies are shed from the bluffbody wake. The unsteady flow structures and the mixing characteristics behind the bluffbody are discussed in details.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.93-96
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• 2006

The heat transfer enhancement by pulsatile flow in the plate heat exchanger has been investigated numerically in the present study. The numerical study was performed in the range of the mass flux from 0.04 to 0.12 kg/s. The results showed that the pulsatile flow produces resonating vortex shedding at the groove sharp edges and a strong transient vortex rotation within the grooved channels. As a result, the mixing between the trapped volume in the grooved cavity and the main stream was enhanced. Good agreements between the predictions and measured data are obtained in steady flow. And the heat transfer of pulsatile flow is about 2.4 times than steady flow when frequency is 10 Hz and the mass flux of cold side is 0.04 kg/s.

• Nuclear Engineering and Technology
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• v.44 no.8
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• pp.831-846
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• 2012

KAERI has developed a two-phase CFD code, CUPID, for a refined calculation of transient two-phase flows related to nuclear reactor thermal hydraulics, and its numerical models have been verified in previous studies. In this paper, the CUPID code is validated against experiments on the downcomer boiling and moderator flow in a Calandria vessel. Physical models relevant to the validation are discussed. Thereafter, multi-scale thermal hydraulic analyses using the CUPID code are introduced. At first, a component-scale calculation for the passive condensate cooling tank (PCCT) of the PASCAL experiment is linked to the CFD-scale calculation for local boiling heat transfer outside the heat exchanger tube. Next, the Rossendorf coolant mixing (ROCOM) test is analyzed by using the CUPID code, which is implicitly coupled with a system-scale code, MARS.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.85-90
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• 2005

The heat transfer enhancement by pulsatile flow in plate heat exchanger has been investigated numerically in the present study. The numerical study was performed ill the range of the Strouhal number from 0.04 to 2 and the Reynolds number from 370 to 730. The results showed that the pulsatile flow produces resonating vortex shedding at the groove sharp edges and a strong transient vortex rotation within the grooved channels. As a result, the mixing between the trapped volume in the grooved cavity and the main stream was enhanced. Good agreements between the predictions and measured data are obtained for the optimum frequency of pulsation and corresponding heat transfer enhancement