• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.8
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• pp.665-670
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• 2014

Because reducing atmospheric pollution is becoming a serious issue, studies are actively focusing on exhaust gas reduction. This study was conducted to determine the emission characteristics when applying an EGR system, the main approach used for NOx reduction, to an off-road mechanical diesel engine. For the application of the EGR system, the emission characteristics in consideration of the engine conditions were analyzed. The optimum EGR ratio for NOx emission reduction was determined by applying variable EGR conditions for each engine speed condition. Considering the above process, the emission characteristics of the modified EGR condition are compared with those of other conditions (non-EGR and existing EGR condition) in the NRTC mode. Consequently, NOx emission was reduced by around 42 compared with the non-EGR condition when using the modified EGR map.

• 한국전산유체공학회:학술대회논문집
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• 2001.10a
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• pp.1-9
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• 2001

In this paper, some numerical methods recently developed for gas-liquid two-phase flows are reviewed. And then, a preconditioning method to solve cavitating flow by the author is introduced. This method employs a finite-difference Runge-Kutta method combined with MUSCL TVD scheme, and a homogeneous equilibrium cavitation model. So that it permits to treat simply the whole gas-liquid two-phase flow field including wave propagation, large density changes and incompressible flow characteristic at low Mach number. Finally, numerical results such as detailed observations of the unsteady cavity flows, a sheet cavitation break-off phenomena and some data related to performance characteristics of hydrofoils are shown.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.99-100
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• 2006

최근 LNG 연료 시장의 호황에 힘입어 LNG선들이 점차 대형화 추세에 있고, LNG선의 추진 기판 또한 경제성, 환경 영향 등의 주어진 요구 환경에 따라 다양화 되고 있다. 기존의 Steam Turbine Propulsion 외에 Conventional 2-stroke Diesel Engine 및 Dual-fuel 4-stroke Diesel Engine 이 LNG선의 주 기관으로 각광받고 있다. 이에 따라 Dual fuel electric propulsion LNGC의 기본 개념, 작동 원리 주요 보조 기기, 타 추진 시스템과의 비교 능에 대해 고찰하였다.

• 한국가스학회:학술대회논문집
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• 2005.05a
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• pp.213-213
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• 2005

• Proceedings of the SAREK Conference
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• 2005.06a
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• pp.223-223
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• 2005

• Journal of the Korean Institute of Gas
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• v.8 no.4 s.25
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• pp.36-41
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• 2004

The breakthrough curve was obtained to evaluate separation efficiency of clinoptilolite as an methane/nitrogen separation adsorbent. The Ca-exchanged clinoptilolite showed improved separation efficiency. The nitrogen adsorption capacity of Ca-clinoptilolite was increased with decreasing temperature. The temperature was decreased from 293K to 253K(feed gas flow rate : 670ml/min, pressure : 333kPa). The adsorption capacity is increased with increasing pressure. The pressure was increased from 333kPa to 700kPa(feed gas flow rate : 670ml/min, temperature : 253K, 293K).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.8
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• pp.539-545
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• 2015

Intense acoustic load is generated when a launch vehicle lifts off, causing the damaging vibrations at the launch vehicle or satellite within the fairing. This paper is concerned with the prediction of lift-off acoustic loads for a launch vehicle. As a test example, the lift-off acoustic load on the Korean launch vehicle, NARO, is predicted by the existing calculation tool, the modified Eldred's second method. Although the acoustic sources, assumed as point sources, are to be located along the center line of the exhaust plume when using the Eldred's prediction method, the exact location of the deflected center line of exhaust gas flow is not usually known. To search for the most appropriate source positions, six models of source line distribution are suggested and the acoustic load prediction results from these models are compared with the actual measurements. It is found that the predicted sound pressure spectrum of the Naro is the most similar to the measured data when the centerline of the turbulent kinetic energy contour is used as the source line.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.181-181
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• 2012

The microwave probe for measuring plasma density is widely used for its advantages: First, it is not affected by the reactive gas. Second, it can measure local plasma parameters such as plasma density, plasma potential and plasma temperature. Third, it is simple and robust. A cut-off probe is the one of the most promising microwave probe. Recently, Kim et al. reveals the physics of the cut-off probe but the effect of the sheath on the determination of the plasma density is not explained. In this presentation, for taking account of sheath effects on determination of plasma density from the cut-off peak, a simplified circuit modeling and an E/M simulation are conducted. The results show that occupation ratio of sheath volume between two tips of the cut-off probe and subsequence pressure condition mainly change position of the cut-off peak with respect to plasma frequency. Magnitude of relative voltage taken on the impedance of sheath and the impedance of bulk plasma can explain this effect. Furthermore, effects of gap size, tip radius, and tip length ware revealed based on above analysis.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3291-3300
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• 2023

Recently molybdenum alloys have been introduced as accident tolerating materials for cladding of fuel rods. Molybdenum element has seven stable isotopes with different neutron absorption cross section used in various fields, including nuclear physics and radioisotope production. This study presents separation approaches for all intermediate isotopes of molybdenum element by squared-off cascades using a newly developed numerical code with Salp Swarm Algorithm (SSA) optimization algorithm. The parameters of cascade including feed flow rate, feed entry stage, cascade cut, input feed flow rate to gas centrifuges (GCs), and cut of the first stage are optimized to maximize both isotope recovery and cascade capacity. The squared off and squared cascades are studied, and the efficiencies are compared. The results obtained from the optimization showed that for the selected squared off cascade, Mo⁹⁴ in four separation steps, Mo⁹⁵ in five steps, Mo⁹⁶ in six steps, Mo⁹⁷ in seven steps, and Mo⁹⁸ in two steps are separated to the desired concentrations. The highest recovery factor is obtained 63% for Mo⁹⁴ separation and lowest recovery factor is found 45% for Mo⁹⁵.

• The KSFM Journal of Fluid Machinery
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• v.15 no.3
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• pp.51-56
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• 2012

This study analyzed the influence of firing biogas on the performance and operation of a gas/steam turbine combined system. A reference gas/steam turbine combined system, designed with biogas fuel(57% volumetric methane) was set up and off-design simulation was made to investigate operating characteristics when a couple of operating schemes to mitigate turbine blade overheating were applied. Performance at base-load operation using each scheme was compared and part load operation using the variable inlet guide vane was analysed. Also, differences in operating characteristics and performance caused by changes in the methane content of biogas and ambient temperature were examined.