• Title/Summary/Keyword: Recirculation system

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Effects of Premixed Fuel and EGR on the Combustion and Emissions Characteristics of HCCI Diesel Engine (HCCI디젤엔진의 연소 및 배기 특성에 미치는 예혼합 연료와 EGR의 영향)

  • Yoon, Young-Hoon;Kim, Dae-Sik;Lee, Chang-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.9 s.240
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    • pp.1006-1012
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    • 2005
  • The effects of premixed fuels(diesel or n-heptane) and exhaust gas recirculation on combustion and exhaust emission characteristics in a DI diesel engine were experimentally investigated. To improve homogeneity of fuel-air mixture in the conventional diesel engine, the premixed fuel is injected by high pressure(5.5 MPa) into the premixing chamber prior to engine cylinder, And several additional systems such as an EGR system, air heating system and back pressure control system were equipped in the DI diesel engine. The results showed that premixed fuel-air mixture undergoes typical HCCI combustion prior to the combustion of DI diesel fuel. The ignition timing of HCCI combustion is delayed by application of EGR, and it also shows that HCCI combustion can be controlled by an EGR.

Clinical use of cold blood potassium cardioplegia (냉혈 K 심정지액의 임상적 이용)

  • Oh, Bong-Suc;Kim, Sang-Hyung;Lee, Dong-Joon
    • Journal of Chest Surgery
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    • v.15 no.1
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    • pp.35-39
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    • 1982
  • Cold blood potassium cardioplegia, by two types of the infusion systems, was used in 45 patients who were undergone the open cardiac operation. Method A [in 25 patients] was the syringe infusion system and method B [in 20 patients] was the pump infusion system. Cold blood potassium cardioplegic solution was used less amount on method B than method A. Serum potassium was often increased significantly on method A as a result of excessive infusion of cold blood potassium cardioplegic solution. But method B, excessive infusion of cold blood potassium cardioplegic solution was prevented by reperfusion of the previous infused cold blood potassium cardioplegic solution through the recirculation system. Alteration of infused rate and concentration of potassium in cold blood potassium cardioplegic solution during infusion [which might be suggested on the method A] could be controlled on method B.

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A Study on the Transient Flow Process in a Vacuum Ejector-Diffuser System (진공 이젝터-디퓨져 시스템내의 비정상 유동 과정에 관한 연구)

  • Vincent, Lijo;Kim, Heuy-Dong;Setoguchi, T.
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2009.05a
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    • pp.299-302
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    • 2009
  • The objective of the present study is to analyze the transient flow through theejector system with the help of a computational fluid dynamics (CFD) method. An attempt is made to investigate the interesting and conflicting phenomenon of the infinite entrainment into the primary stream without an infinite mass supply from the secondary chamber. The results obtained show that the one and only condition in which an infinite mass entrainment can be possible in such types of ejectors is the generation of a re-circulation zone near the primary nozzle exit. The flow in the secondary chamber attains a state of dynamic equilibrium of pressures at the onset of the recirculation zone. A steady flow in the ejector system is valid only after this point.

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Optical Fiber Delay-Line Filter with Recirculation Loop Structure Using a Fiber Grating (광섬유 격자를 이용한 재순환 광섬유 지연선로 필터)

  • 김성철;권서원;이상배;권상삼;이병호
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.36D no.5
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    • pp.80-87
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    • 1999
  • We propose a new recirculating fiber delay-line filter structure. In proposed system, we insert a fiber Bragg grating(FBG) into a recirculating fiber delay line and it operates as a partially reflection mirror. Therefore, the transfer function of the system is given by the recirculating delay output part and the multiple-reflected output part due to a FBG. By adjusting the parameters such as coupling coefficient, reflectivity of FBG, and gain, we can make the system operate in various filter.

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A Study on the Development and Application of a Design Program for Centrifugal Turbo Fan (원심 터보홴 설계용 프로그램의 개발 및 응용에 대한 연구)

  • Kim, Jang-Kweon;Oh, Seok-Hyung
    • Journal of Power System Engineering
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    • v.20 no.6
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    • pp.71-79
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    • 2016
  • This paper introduces the design method of the centrifugal turbo fan and the process of developing the design program of it. The developed design program confirmed the applicability by experimental performance data. Here, we proposed new velocity coefficients and considered various losses such as impeller inlet loss, vane passage flow loss, casing pressure loss, recirculation loss power, and disk friction loss power. Especially, the inlet and outlet widths of the impeller were newly determined by reflecting the experimental results. As a result, this fan design program shows a good performance result regardless of the types of impeller and is expected to be a very useful design tool.

The Effect of EGR on Exhaust Emissions in a Direct Injection Diesel Engine (직접 분사식 디젤엔진에서 EGR이 배기배출물에 미치는 영향에 관한 연구)

  • Jang, S.H.
    • Journal of Power System Engineering
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    • v.8 no.1
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    • pp.18-23
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    • 2004
  • The direct injection diesel engine is one of the most efficient thermal engines. For this reason DI diesel engines are widely used for heavy-duty applications. But the world is faced with very serious problems related to the air pollution due to the exhaust emissions of diesel engine. So, that is air pollution related to exhaust gas resulted from explosive combustion should be improved. Exhaust Gas Recirculation(EGR) is a proven method to reduce NOx emissions. In this study, the experiments-were performed at various engine loads while the EGR rates were set from 0% to 20%. The emissions trade-off and combustion of diesel engine are investigated. Hot and cooled EGR are achieved without cooling and with cooling respectively. It was found that the exhaust emissions with the EGR system resulted in a very large reduction in oxides of nitrogen at the expense of higher smoke emissions. Also, the reduction rates of NOx emissions for hot and cooled EGR are similar at load 20%.

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Two-phase flow and heat transfer characteristics in a submerged gas injection system (잠겨진 가스분사장치에서의 2상 유동 및 열전달 특성)

  • 최청렬;김창녕
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.11 no.6
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    • pp.824-834
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    • 1999
  • Characteristics of two-phase flow and heat transfer were numerically investigated in a submerged gas injection system when temperature of the injected gas was different from that of the liquid. The Eulerian approach was used for both the continuous and dispersed phases. The turbulence in the liquid phase was modeled using the standard $k-\varepsilon$$\varepsilon$ turbulence model. The interphase friction and heat transfer coefficient were calculated from the correlations available in the literature. The turbulent dispersion of the phases was modeled by a "dispersion Prandtl number". In the case with heat transfer where the temperature of the injected gas is higher than the mean liquid temperature, the axial and the radial velocities are lower in comparison with the case of homogeneous temperatures. The results in the present research are of interest in the design and operation of a wide variety of material and chemical processes.

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Applicability of Industrial Waste Management Evaluation Model (IWEM) in Korea (지하수 오염방지를 위한 산업폐기물 관리평가 모델(IWEM)의 국내 적용성 분석)

  • Park, Dong-Won;Woo, Nam-C.;Chung, David
    • Journal of Soil and Groundwater Environment
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    • v.17 no.1
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    • pp.1-7
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    • 2012
  • Selection of appropriate liner type would be the most important factor to prevent groundwater contamination by leachate from waste management site. This report introduces the IWEM (Industrial Waste Management Evaluation Model) developed by US EPA to evaluate the potential pollution of groundwater under the waste management unit and to suggest an appropriate type of liner, and provides with the results of IWEM application to a coal-ash landfill site in Korea as a case study. IWEM uses a standard method using a database, a decision-making process based on site characteristics, and the user-friendly input-and-output system. Authors evaluate this model to be applicable in Korea provided that the database is replaced into local data.

Comparative study of CFD and 3D thermal-hydraulic system codes in predicting natural convection and thermal stratification phenomena in an experimental facility

  • Audrius Grazevicius;Anis Bousbia-Salah
    • Nuclear Engineering and Technology
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    • v.55 no.4
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    • pp.1555-1562
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    • 2023
  • Natural circulation phenomena have been nowadays largely revisited aiming to investigate the performances of passive safety systems in carrying-out heat removal under accidental conditions. For this purpose, assessment studies using CFD (Computational Fluid Dynamics) and also 3D thermal-hydraulic system codes are considered at different levels of the design and safety demonstration issues. However, these tools have not being extensively validated for specific natural circulation flow regimes involving flow mixing, temperature stratification, flow recirculation and instabilities. In the present study, an experimental test case based on a small-scale pool test rig experiment performed by Korea Atomic Energy Research Institute, is considered for code-to-code and code-to-experimental data comparison. The test simulation is carried out using the FLUENT and the 3D thermal-hydraulic system CATHARE-2 codes. The objective is to evaluate and compare their prediction capabilities with respect to the test conditions of the experiment. It was observed that, notwithstanding their numerical and modelling differences, similar agreement results are obtained. Nevertheless, additional investigations efforts are still needed for a better representation of the considered phenomena.

A Fundamental Study of Hybrid Combustion System Applying Exhaust Gas Recirculation (배기가스 재순환을 적용한 하이브리드 연소시스템에 대한 기초 연구)

  • Oh, Wheesung;Yu, Byeonghun;Park, Taejoon;Lee, Chang-Eon
    • Journal of Energy Engineering
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    • v.25 no.1
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    • pp.100-107
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    • 2016
  • In this study confirmed the reduction effect of pollutant by applying Fi-EGR and FPI-EGR to hybrid combustion system realizing premixed flame and non-premxied flame at once. The results showed that NOx emission index decreased significantly in case of adopting EGR. Additionally, the hybrid combustion system with EGR resulted in a better performance compared to usual non-premixed combustion system such that it can reduce $NO_x$ emission at equivalent EGR ratios. Especially, in the case of 25% of FI-EGR ratio at hybrid combustion system that the ratio of non-premixed and premixed is 50 : 50, NOx emission index reduction rate was about 59% compared to $NO_x$ emission of non-premixed combustion system without EGR and in the case of 15% of FPI-EGR ratio at hybrid combustion system that the ratio of non-premixed and premixed is 70 : 30, $NO_x$ emission index reduction rate was about 48% compared to $NO_x$ emission of hybrid combustion system without EGR.