• Title/Summary/Keyword: Flow Path

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Reduction of Flow-Induced Noise in an Expansion Muffler with Lids (삽입관이 있는 확장형 소음기에서의 기류음 감소)

  • Kang, Woong;Kim, Hyung-Jin;Sung, Hyung-Jin
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.2
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    • pp.79-84
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    • 2009
  • Turbocharger has been widely used in many passenger cars in application with diesel engines because of high power and fuel efficiency. However, flow-induced noise (whoosh or hissing noise) which is generated within a compressor during its operation at marginal surge line can deteriorate noise characteristics. Hissing noise excitation is associated with the generation of turbulence within the turbocharger compressor and radiated through the transmission path in a turbocharger system. In this study, a expansion muffler with lids is devised and installed in the transmission path to reduce the hissing noise. Acoustic and fluid dynamic characteristics for the muffler are investigated which are related to the unsteadiness of turbulence and pressure in the turbocharger system. A transfer matrix method is used to analyze the transmission loss of the muffler. A simple expansion muffler with lids is proposed for the reduction of high frequency component noise. Turbulence simulation is carried out by a standard k - ${\varepsilon}$ model. An optimal design condition of the muffler is obtained by extensive acoustic and fluid dynamic analysis on the engine dynamometer with anechoic chamber. A significant reduction of the hissing noise is achieved at the optimal design of the muffler as compared with the conventional muffler.

Numerical study on PEM fuel cell performance with variation of GDL permeability and channel geometry (기체확산층의 유동투과율과 채널 형상 변화에 따른 고분자 전해질 연료전지 성능변화 수치연구)

  • Koh, Soo-Gon;Sohn, Sang-Ho;Nam, Jin-Hyun;Kim, Charn-Jung
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.3114-3119
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    • 2008
  • Relatively high convective flow exists in the under-rib regions of a gas diffusion layer (GDL) when serpentine flow fields are employed in a PEMFC. This under-rib convection is believed to be favorable for the performance of PEMFCs, by enabling more effective use of catalysts in the under-rib regions. From the fact that the under-rib convection in a GDL is directly proportional to the permeability of the GDL, computational fluid dynamics (CFD) simulations were performed to discover the relationship between the GDL permeability and the PEMFC performance. Single-, triple-, and quintuple-path parallel serpentine flow fields for $9\;cm^2$ active cell area were considered while changing the GDL permeability from $1{\times}10^{-12}$ to $5{\times}10^{-11}m^2$. The results showed that higher GDL permeability generally resulted in better performance of PEMFCs, but the degree of performance enhancement became smaller as the parallel path number increased. The effects of the permeability on the local variables were also discussed.

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A study on the Structural Stability about the Fan Blade by the Air Excited Forces. (공기 가진력에 의한 팬 블레이드 구조 안정성 평가에 관한 연구)

  • 정규강;김경희;조생현
    • Journal of the Korean Society of Propulsion Engineers
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    • v.4 no.1
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    • pp.93-101
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    • 2000
  • In a gas-turbine engine, fan blades in flow path are confronted with many kinds of loading. The study of the excited force by the wake of struts has proposed and the possibility of fatigue failure about rotating fan blades by the excited force at the steady state is evaluated. Equations of the excited force of wakes has been derived at the steady state and the maximum pressure distributions measured at the transient state are proposed. Dynamic characteristics and the fatigue strength of fan blades by experimental test were obtained. To evaluate HCF(High Cycle Fatigue) damage of fan blades, FEM analysis was performed with a steady state harmonic response, which was followed by high cycle fatigue damage factor from goodman diagram.

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Nonsteady Plane-strain Ideal Forming with Elastic Dead Zone (탄성 변형 영역을 고려한 비정상 평면 변형 이상 공정 이론)

  • Lee W.;Chung K.;Alexandrov S.;Kang T.J.
    • Transactions of Materials Processing
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    • v.13 no.6 s.70
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    • pp.540-545
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    • 2004
  • Ever since the ideal forming theory has been developed for process design purposes, application has been limited to sheet forming and, fur bulk forming, to two-dimensional steady flow. Here, application for the non-steady case was performed under the plane-strain condition based on the theory previously developed. In the ideal flow, material elements deform following the minimum plastic work path (or mostly proportional true strain path) so that the ideal plane-stram flow can be effectively described using the two-dimensional orthogonal convective coordinate system. Besides kinematics, fur a prescribed final part shape, schemes to optimize a preform shape out of a class of initial configurations and also to define the evolution of shapes and boundary tractions were developed. Discussions include the two problematic issues on internal tractions and the non-monotonous straining. For demonstration purposes, numerical calculations were made for a bulk part under forging.

Saturation Tendency for Tracing of Runoff Path on GIS Platform (유출경로 추적을 위한 GIS상에서의 유역 포화성향 고찰)

  • Kim, Sanghyun;Kunyeoun Han
    • Proceedings of the Korea Water Resources Association Conference
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    • 1997.05a
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    • pp.192-198
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    • 1997
  • The spatial variation of saturation tendency can be calculated from the Digital Elevation Model (DEM) employing the multiple flow direction algorithm on the platform of Geographic Resources Support Analysis System (GRASS). It is expected that a bettter understanding of dynamical runoff processes in hillslope hydrological scale is obtained through tracing various runoff path such as infiltration excess overland flow component, strutation excess overland flow component and subsurface runoff component. A procedure is suggested to consider the effect of a tile system on calculating the topographic index. A small agricultural subwatershed (3.4 km2) is used for this study.

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Age Differences in Perceptions and Relationships Among Determinants of Loyalty in Online Games (연령별 차이를 중심으로 본 온라인게임 애호도 영향요인에 관한 연구)

  • Um, Myoung-Yong;Kwon, Moon-Ju;Byun, Wan-Soo;Kim, Tae-Ung
    • Journal of Information Technology Services
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    • v.6 no.1
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    • pp.83-99
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    • 2007
  • The purpose of this research is to identify the determinants of loyalty in online games. This study developed a research model to analyze the factors explaining the loyalty level from gamers, employing social identification, flow, and positive anticipated emotion as major research variables, and collected 1308 survey responses from gamers. Within the context of arguing that the exploration of age range issues with respect to online games is important, this research also examines the age differences in path coefficients. To this end, the structural model was tested with the data from entire data sample (i.e., the age of 10s, 20s, and 30s pooled together) and each of the subsamples (i.e., teens taken separately, twenties taken separately, and thirties taken separately). Properties of the causal paths, including standardized path coefficients, the significance of difference, in the hypothesized model, are also presented, so that we can investigate the relative influences of different dominants, demonstrating how teens, twenties, and thirties differ in their decision-making processes regarding the flow, social identification and loyalty from online games.

CFD Analysis for Spiral-Jacketed Thermal Storage Tank in Solar Heating Systems (태양열 시스템에 적용된 나선재킷형 축열조의 CFD 해석)

  • Nam, Jin-Hyun;Kim, Min-Cheol;Kim, Charn-Jung;Hong, Hi-Ki
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.10
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    • pp.645-653
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    • 2008
  • Spiral-jacketed thermal storage tanks can greatly simplify solar heating systems while maintaining the thermal performance at a similar level as conventional systems with an external heat exchanger. Proper design of the spiral-jacket flow path is essential to make the most of solar energy, and thus to maximize the thermal performance. In the present work, computational fluid dynamics (CFD) analysis was carried out for a spiral-jacketed storage tank installed in a solar heating demonstration system. The results of the CFD analysis showed a good agreement with experimentally determined thermal performance indices such as the acquired heat, collector efficiency, and mixed temperature in the storage tank. This verified CFD modelling approach can be a useful design tool in optimizing the shape of spiral-jacket flow path and the flow rate of circulating fluid for better performance.

Development of Non-Invasive Pressure Estimation Using 3D Multi-Path Line Integration Method from Magnetic Resonance Velocimetry (MRV) (자기공명유속계 (MRV) 에서 3차원 다중경로 선적분법을 활용한 비침습적 압력예측 방법 개발)

  • Ilhoon Jang;Muhammad Hafidz Ariffudin;Simon Song
    • Journal of the Korean Society of Visualization
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    • v.21 no.2
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    • pp.14-23
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    • 2023
  • The pressure difference across stenotic blood vessels is a commonly used clinical metric for diagnosing many cardiovascular diseases. At present, most clinical pressure measurements rely solely on invasive catheterization. In this study, we propose a novel method for non-invasive pressure estimation using the incompressible Navier-Stokes equations and a 3D multi-path integration approach. We verify spatio-temporal convergence on an in-silico dataset of a cylindrical straight pipe phantom with steady and pulsatile flow fields. We then evaluate the proposed method on an in vitro dataset of reconstructed control, pre-operative, and post-operative carotid artery cases acquired from 4D flow MRI. The performance of our method is compared to existing approaches based on the pressure Poisson equation and work-energy relative pressure. The results demonstrate the proposed method's high accuracy, robustness to spatio-temporal subsampling, and reduced sensitivity to noise, highlighting its great potential for non-invasive pressure estimation.

PATH VARIABILITY OF THE CHANGJIANG DILUTED WATER IN SUMMER

  • Yang, Joon-Yong;Cho, Yang-Ki;Chang, Kyung-Il;Suh, Young-Sang
    • Proceedings of the KSRS Conference
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    • v.2
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    • pp.688-691
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    • 2006
  • The current system of the East China Sea, a marginal sea in the northwest Pacific, has a seasonal variation. The Changjiang Diluted Water, Chinese coastal water in the East China Sea, has different seasonal paths. It flows southward along the Chinese coast within a narrow band in winter and does northeastward the Korea/Tsushima Strait in summer, which has been a subject to many researchers. In particular, low salinity in the South Sea of Korea in 1996 and 1998 was in discord with the Changjiang River discharge and the Changjiang Diluted Water seems to play an important role in occurrence of red tide in the South Sea of Korea in 1997 and on the contrary, disappearance in the next year. These facts suggested that the Changjiang Diluted Water does not flow along the same path in every summer. According to the analyses for path of the Changjiang Diluted Water using ocean color images by SeaWiFS and salinity observations by shipboard CTD in August for recent years, the Changjiang Diluted Water in summer flowed within the range of direction from southeastward to north-northeastward anticlockwise. However, the Changjiang Diluted Water flowed northeastward toward Jeju Island of Korea for the most part. It is necessary to examine the influence of major factors on path variability of the CDW in summer such as surface wind, the Changjiang River discharge and background current.

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Reaction Path Modelling on Geochemical Evolution of Groundwater and Formation of Secondary Minerals in Water-Gneiss Reaction System (편마암-물 반응계에서 지하수의 지화학적 진화 및 이차광물 생성에 관한 반응경로 모델링)

  • 정찬호;김천수;김통권;김수진
    • Journal of the Mineralogical Society of Korea
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    • v.10 no.1
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    • pp.33-44
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    • 1997
  • The reaction path of water-gneiss in 200m borehole at the Soorichi site of Yugu Myeon, Chungnam was simulated by the EQ3NR/EQ6 program. Mineral composition of borehole core and fracture-filling minerals, and chemical composition of groundwater was published by authors. In this study, chemical evolution of groundwater and formation of secondary minerals in water-gneiss system was modelled on the basis of published results. The surface water was used as a starting solution for reaction. Input parameters for modelling such as mineral assemblage and their volume percent, chemical composition of mineral phases, water/rock ratio reactive surface area, dissolution rates of mineral phases were determined by experimental measurement and model fit. EQ6 modelling of the reaction path in water-gneiss system has been carried out by a flow-centered flow through open system which can be considered as a suitable option for fracture flow of groundwater. The modelling results show that reaction time of 133 years is required to reach equilibrium state in water-gneiss system, and evolution of present groundwater will continue to pH 9.45 and higher na ion concentration. The secondary minerals formed from equeous phase are kaolinite, smectite, saponite, muscovite, mesolite, celadonite, microcline and calcite with uincreasing time. Modeling results are comparatively well fitted to pH and chemical composition of borehole groudwater, secondary minerals identified and tritium age of groundwater. The EQ6 modelling results are dependent on reliability of input parameters: water-rock ratio, effective reaction surface area and dissolution rates of mineral phases, which are difficult parameters to be measured.

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