• Title/Summary/Keyword: Confined Jet Flow

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Numerical Study on Characteristics of Gas Leakage in an Underground Combined Cycle Power Plant (지하 복합발전 플랜트 내부의 가스 누출 특성에 대한 수치해석 연구)

  • Bang, Joo Won;Sung, Kun Hyuk;Ryou, Hong Sun;Lee, Seong Hyuk
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.5
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    • pp.594-600
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    • 2016
  • The present study numerically investigated the gas leakage characteristics in a simplified underground combined cycle power plant. The effect of obstacles near a crack location on the gas concentration in the confined space was analyzed by using the lower flammable limit (LFL) of methane gas. When the jet flow was close to the vertical walls, the longitudinal leakage distance increased by about 60% (when an obstacles was present) compared to the case without any obstacle, because these obstacles prevented transverse flows. In addition, when an air filter was installed near to the trajectory of the gas flow, the longitudinal leakage distance was similar to the distance between the crack and obstacle, whereas the transverse leakage distance increased up to 8 times compared to the case without any obstacle. As the jet flow impacts on the obstacle and changes its direction, the gas flows recirculate. Therefore, it is necessary to consider the effect of the structure and facility locations on the trajectory of the jet flow to propose an accident prevention system in confined spaces.

Numerical Simulations of the Supersonic Jet Impingement in a Confined Plenum of Vertical Launching System

  • Lee Kwang-Seop;Lee Jin-Gyu;Hong Seung-Kyu;Ahan Chang-Soo
    • 한국전산유체공학회:학술대회논문집
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    • 2006.05a
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    • pp.301-305
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    • 2006
  • The Vertical Launching System design is especially complicated by complex flow structure in a plenum with the severe thermal state and high pressure load form the hot exhaust plume. The flow structures are numerically simulated by using the commercial code, CFD-FASTRAN with the axi-symmetrical Navier-Stokes equations. Two different cases are considered; that is, the stationary fire and the moving fire.

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Heat/mass transfer characteristics of arrays of impingement jets using effusion holes (유출홀을 사용한 배열충돌제트의 열/물질전달 특성)

  • Yoon, P.H.;Hwang, S.D.;Cho, H.H.
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.125-131
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    • 2000
  • The local heat/mass transfer coefficients for arrays of impinging circular air jets on a plane surface are determined by means of the naphthalene sublimation method. Spent fluid makes a crossflow in the confined space. The crossflow reduces heat/mass transfer at the small gap distance between the jet plate and impingement surface because of reentrainment of the spent fluid. The present study suggests a new exhaust system having effusion holes in the impinging jet plate. The spent air flow out after impingement just through effusion holes located in the upper plate. This system increases heat/mass transfer coefficients and uniformity for small gap distances$(H/d{\leq}2)$

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Prediction of Turbulent Flows with Separation and Swirl Using the RNG K-$\varepsilon$ Turbulence Model (RNG k-$\varepsilon$ 난류모델을 이용한 유동박리 및 선회를 가지는 난류유동의 예측)

  • 김성구;오군섭;김용모;이창식
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.5
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    • pp.119-129
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    • 1996
  • This study is concerned with the critical evaluation of predicative capability of a k-$\varepsilon$ turbulence model using the Renormalization Group(RNG) theory. The present numerical model for solution of the Navier-Stokes System is based on the modified PISO algorithms. Computations have been performed with the RNG-based K-$\varepsilon$ model for the two-dimensional flow over a backward-facing step, a confined coaxial jet, and a swirling flow in a swirl combustor. Numerical results are compared with experimental data in terms of mean flow velocities, turbulent kinetic energy, and turbulent stresses. Numerical results clearly indicate that the RNG-based K-$\varepsilon$ turbulence model shows a significant improvement over a standard K-$\varepsilon$ model in predicting the turbulent flows with flow separation and swirl.

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A Numerical Study on the Heat Transfer Characteristics of the Multiple Slot Impinging Jet (다양한 노즐 수 변화에 따른 충돌 제트의 열전달 특성에 관한 수치적 연구)

  • Kim, Sang-Keun;Ha, Man-Yeong;Son, Chang-Min
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.23 no.11
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    • pp.754-761
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    • 2011
  • The present study numerically investigates two-dimensional flow and heat transfer in the multiple confined impinging slot jet. Numerical simulations are performed for the different Reynolds numbers(Re=100 and 200) in the range of nozzles from 1 to 9 and height ratios(H/D) from 2 to 5, where H/D is the ratio of the channel height to the slot width. The vector plots of velocity profile, stagnation and averaged Nusselt number distributions are presented in this paper. The dependency of thermal fields on the Reynolds number, nozzle number and height ratio can be clarified by observing the Nusselt number as heat transfer characteristic at the stagnation point and impingement surface. The Nusselt number at the stagnation point of the central slot shows unsteadiness at H/D=3 and Re=200. The value of Nusselt number at the stagnation point of the central slot decreases with higher Reynolds number and number of nozzle although overall area averaged Nusselt number increases. Hence careful selection of geometrical parameters and number of nozzle are necessary for optimization of the heat transfer performance of multiple slot impinging jet.

A Numerical Study for the Design of Ventilation System for the gaseous Pollutants (기체 유해물질 환기장치 설계를 위한 수치모사)

  • 엄태인
    • Journal of the Korean Society of Safety
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    • v.9 no.4
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    • pp.77-84
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    • 1994
  • A study is performed in order to design a effective ventilation equipment for the pollutants in workshop. The procedure has been used to calculate the flow in a confined rectangular space channel. A cross free stream is flowed from open space and jet stream including pollutants is injected from bottom area. Calculation results shows a wake region which exists immediarely downstream of the jet discharge and are compared with the experimental data. Calculation data are in good agreement with experimental results. A wake plays an important role on a stagnation of the pollutants. Thus ventilation equipment has to be designed without a stagnation region which give rise to concentration stratification. In this study, calculation parameters are the position and velocity of pollutants and fresh air from cross free stream. It is concluded that more measurements of local velocities, temperatures and concentrations of the pollutants.

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Generation and Characterization of Homogeneous Isotropic Turbulence (균질한 등방향성 난류 생성 및 특성 변화 분석)

  • Lee, HoonSang;Han, KyuHo;Park, Han June;Jung, HyunKyun;Hwang, Wontae
    • Journal of the Korean Society of Visualization
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    • v.16 no.1
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    • pp.21-29
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    • 2018
  • Homogeneous and isotropic turbulence (HIT) with no mean flow is a very useful type of flow for basic turbulence research. However, it is difficult to generate HIT in the lab. In this study, we implemented HIT in a confined box through synthetic jet actuators using sub-woofer speakers. Characteristics of HIT are varied depending on the strength of the jets. We used 2D PIV to measure the velocity field. Turbulence statistics such as homogeneity, isotropy ratio, turbulence kinetic energy, dissipation rate, Taylor microscale, Kolmogorov scale, and velocity correlation coefficient were calculated. Most of the turbulence statistics increased exponentially according to the strength of the jets, and the Taylor Reynolds number reached up to 185.

A Behavior of the Ultrasonically-atomized Kerosene Lifted-flame According to the Position of Ultrasonic Standing-wave Field (정상초음파장의 위치에 따른 초음파 무화 케로신 부상화염의 거동)

  • Chang Han Bae;Jeong Soo Kim
    • Journal of the Korean Society of Propulsion Engineers
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    • v.27 no.1
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    • pp.1-8
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    • 2023
  • A study was conducted to scrutinize the behavior of the ultrasonically-atomized kerosene lifted-flame according to the carrier gas flow-rate and position of ultrasonic standing wave (USW). The combustion region of the kerosene-aerosol generated through a slit-jet nozzle was visualized using a DSLR, ICCD, high-speed camera, and Schlieren technique, and the fuel consumption was measured by using a precision balance. As a result, the flame was confined within the region bounded by the USW-field, and the fuel consumption decreased as the position of the USW field increased.

Numerical Study of Turbulent Swirling Isothermal and Spray-Combusting Flows (난류선회 등온 및 분무연소 유동에 대한 수치해석)

  • 김성구;안국영;김용모;이창식
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.5
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    • pp.130-141
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    • 1996
  • Numerical study of a confined, swirling, isothermal and spray-combusting flows has been presented. The pressure-velocity coupling in the Eulerian gas-phase equation is handled by the improved PISO algorithm. The droplet dispersion by turbulence is introduced by a Stochastic Separated Flow(SSF) model. The k-$\varepsilon$ turbulence model and the eddy dissipation model are employed to account for turbulence-combustion interaction. The detailed comparison with experimental data has been made for the isothermal jet swirling flows and the nearly monodisperse spray-combusting flow in the swirl combustor.

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Effect of Arrays of Impinging Jets with Crossflow on Heat/Mass Transfer (배열충돌제트에서 횡방향유동성분에 따른 열/물질전달 특성 고찰)

  • Yoon, Pil-Hyun;Rhee, Dong-Ho;Cho, Hyung-Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.2
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    • pp.195-203
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    • 2000
  • The local heat/mass transfer coefficients for arrays of impinging circular air jets on a plane surface are determined by means of the naphthalene sublimation method. Fluid from the spent jets is constrained to flow out of the system in one direction. Therefore, the spent fluid makes a crossflow in the confined space. The present study investigates effects of jet-orifice-plate to impingement-surface spacing and jet Reynolds number. The spanwise- and overall-averaged heat/mass transfer coefficients are obtained by numerical integrating the local heat transfer coefficients. The local maximum heat/mass transfer coefficients move further in the downstream direction due to the increase of crossflow velocity. At the mid-way between adjacent jets, the heat/mass transfer coefficients have a small peak owing to the collision of the adjacent wall jets and are affected strongly by the crossflow. The effect of the crossflow occurs strongly at the small orifice-to-impingement surface distance.