• 제목/요약/키워드: Annular region

검색결과 79건 처리시간 0.02초

고속분사를 이용한 소형 축열식 복사관 버너시스템의 성능평가 (Performance Estimation of Small Regenerative Radiant Tube Burner System using High Velocity Discharge)

  • 조한창;조길원;이용국
    • 한국연소학회:학술대회논문집
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    • 한국연소학회 2004년도 제28회 KOSCO SYMPOSIUM 논문집
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    • pp.242-247
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    • 2004
  • An Experimental study was conducted on spray combustion using dual swirlers at different outlet angle; co-swirl and counter-swirl. To understand the characteristics of turbulent spray combustion of dual swirl flow (DSF), the axial helical annular vaned swirlers with various swirl ratios and combination of angle and direction were designed. and temperature measurements of a rapidly thermocouple insertion and measurements of soot volume fraction and microrstructure using thermophoretic sampling particle diagnostic (TSPD) as TEM were carried out. The NOx, $CO_2$, $O_2$, etc. was analyzed using emission gas analyzer. The results show that flame stability were maintained under very lean condition. for both co-swirl and counter-swirl case. And though Counter-swirl case kept the higher temperature region compared to co-swirl case, Counter-swirl combustion represented less NOx emission and soot formation than co-swirl case.

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선대칭 형태에 있어서의 베이스 압력의 예측 (Prediction on The Base Pressure for An Axisymmetric Body)

  • 백두성;한영출
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2000년도 추계학술대회논문집B
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    • pp.491-496
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    • 2000
  • The physics of the flow field surrounding an engine nacelle afterbody is very complex. A high pressure jet from the nozzle interacts with the external flow and causes upstream influence on the afterbody surface field. At certain conditions, the nozzle boundary layer can separate, either by shock wave interaction or by adverse pressure gradient effect, resulting in a severe drag penalty. Furthermore, a finite afterbody base implies a recirculating flow region. A flow modeling method has been developed to analyze the flow in the annular base(rear-facing surface) of a circular engine nacelle flying at subsonic speed but with a supersonic exhause jet. Real values of exhaust gas properties and temperature are included.

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Applicability of One-Dimensional Mechanistic Post-Dryout Prediction Model

  • Jeong, Hae-Yong;No, Hee-Cheon
    • 한국원자력학회:학술대회논문집
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    • 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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    • pp.586-591
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    • 1996
  • Through the analysis of many experimental post-dryout data, it is shown that the most probable flow regime near dryout or quench front is not annular flow but churn-turbulent flow when the mass flux is low. A correlation describing the initial droplet size just after the CHF position at low mass flux is suggested through regression analysis. In the post-dryout region at low pressure and low flow, it is found that the suggested one-dimensional mechanistic model is not applicable when the vapor superficial velocity is very low, i.e., when the flow is bubbly or slug flow regime. This is explained by the change of main entrainment mechanism with the change of flow regime. Therefore, the suggested correlation is valid only in the churn-turbulent flow regime ( $j_{g}$ $^{*}$=0.5~4.5).).

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2중스월류에 의한 난류분무화염의 연소특성 연구 (A Study on Combustion Characteristics of Turbulent Spray Flame by the Dual Swirler)

  • 이강엽;황상순
    • 한국연소학회지
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    • 제5권1호
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    • pp.67-79
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    • 2000
  • An Experimental study was conducted on spray combustion using dual swirlers at different outlet angle; co-swirl and counter-swirl. To understand the characteristics of turbulent spray combustion of dual swril flow(DSF), the axial helical annular vaned swirlers with various swirl ratios and combination of angle and direction were designed. and temperature measurements of a rapidly thermocouple insertion and measurements of soot volume fraction and microstructure using thermophoretic sampling particle diagnostic(TSPD) as TEM were carried out. The NOx, $CO_2,\;O_2$, etc. was analyzed using emission gas analyzer. The results show that flame stability were maintained under very lean condition. for both co-swirl and counter-swirl case. And though Counter-swirl case kept the higher temperature region compared to co-swirl case, Counter-swirl combustion represented less NOx emission and soot formation than co-swirl case.

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DEVELOPMENT OF AN LES METHODOLOGY FOR COMPLEX GEOMETRIES

  • Merzari, Elia;Ninokata, Hisashi
    • Nuclear Engineering and Technology
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    • 제41권7호
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    • pp.893-906
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    • 2009
  • The present work presents the development of a Large Eddy Simulation (LES) methodology viable for complex geometries and suitable for the simulation of rod-bundles. The use of LES and Direct Numerical Simulation (DNS) allows for a deeper analysis of the flow field and the use of stochastical tools in order to obtain additional insight into rod-bundle hydrodynamics. Moreover, traditional steady-state CFD simulations fail to accurately predict distributions of velocity and temperature in rod-bundles when the pitch (P) to diameter (D) ratio P/D is smaller than 1.1 for triangular lattices of cylindrical pins. This deficiency is considered to be due to the failure to predict large-scale coherent structures in the region of the gap. The main features of the code include multi-block capability and the use of the fractional step algorithm. As a Sub-Grid-Scale (SGS) model, a Dynamic Smagorinsky model has been used. The code has been tested on plane channel flow and the flow in annular ducts. The results are in excellent agreement with experiments and previous calculations.

하이브리드 스폴밸브의 정특성 연구 (Study on Static Characteristics of Hybrid Spool Valve)

  • 윤소남;함영복;김동수
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집B
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    • pp.121-126
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    • 2001
  • In this study, the 4-way spool valve characteristics are clearly defined and proposed new type of spool valve. This paper presents governing equations of the flow through clearances between sleeve and spool as a model of orifice flow for null characteristic analysis, and programmed analysis software of it. This software is possible to basically analysis that not only which case of open center, closed center or critical center but +,- displacement of spool, lab position, boundary region and spool opening of the valve, and to estimate the pressure variation in the spool and external leak flow variation. We are convinced that the scale of load pressure difference is changed as lab condition of spool valve, and this scale is changed with boundary point on the annular clearance. It is vary useful to designer and user of spool valve with this design data and analysis software.

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가스터빈 연소기의 화염 불안정성에 관한 연구 (A study on the combustion instability in a bluffbody dump combustor)

  • 이병준
    • 대한기계학회논문집B
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    • 제22권7호
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    • pp.1022-1029
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    • 1998
  • The relation of the inlet fuel distribution, velocity, and overall equivalence ratio to the stability of a lean burning no-swirl dump combustor was examined. Premixed or partially premixed natural gas was introduced into the air stream, which flowed to the dump region through an annular inlet pipe. Inlet air was preheated upto 400 deg.C. Combustion instability was observed to occur at higher value of equivalence ratio (> 0.6) as the degree of unpremixedness was increased. Instabilities exhibited a dominant frequency of ~ 500 Hz, which corresponded to a half wave mode of combustor. CH chemiluminescence and pressure fluctuations were in-phase when combustion instabilities occurred. Acetone LIF images revealed that there was a strong fuel concentration gradient across the inlet annulus. Phase resolved OH LIF images showed that inlet fuel distribution was affected by the combustion instabilities.

ON THE WEAKENED HYPOTHESES-BASED GENERALIZATIONS OF THE ENESTRÖM-KAKEYA THEOREM

  • Shahbaz Mir;Abdul Liman
    • Korean Journal of Mathematics
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    • 제32권2호
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    • pp.229-243
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    • 2024
  • According to the well-known Eneström-Kakeya Theorem, all the zeros of a polynomial $P(z)={\sum_{s=0}^{n}}a_sz^s$ of degree n with real coefficients satisfying an ≥ an-1 ≥ · · · ≥ a1 ≥ a0 > 0 lie in the complex plane |z| ≤ 1. We provide comparable results with hypotheses relating to the real and imaginary parts of the coefficients as well as the coefficients' moduli in response to recent findings about an Eneström-Kakeya "type" condition on real coefficients. Our findings so broadly extend the other previous findings.

S자형 환형덕트가 원심압축기 성능에 미치는 영향에 관한 연구 (A Study on the Influence of S Shaped Annular Duct on the Centrifugal Compressor Performance)

  • 정주현;전승배;김승우
    • 한국추진공학회지
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    • 제2권2호
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    • pp.64-73
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    • 1998
  • 항공기용 엔진에는 압축기단들 사이에 스트럿을 포함하는 S자형 환형덕트가 존재하기도 한다. 이러한 엔진에서 S자형 덕트를 통과하는 유동은 볼록면과 오목면을 따라 가면서 가속과 감속이 이루어지고, 벽면에서의 경계층 성장으로 인해 유로폐쇄량이 증가한다. 이처럼 S자형 덕트의 영향으로 후방에 존재하는 압축기는 불균일한 축방향 속도분포에 따른 영향을 받게 된다. 따라서, 후방 압축기는 전방에 위치한 S자형 덕트의 영향을 충분히 고려하여 설계하여야 한다. S자형 덕트가 미치는 영향을 고려하여 설계된 원심압축기의 성능을 검증하고, S자형 덕트가 원심압축기 성능에 미치는 영향을 파악해보기 위해 압축기 입구에 S자형 환형덕트를 장착한 경우와 원통형 덕트를 장착한 경우에 대해 각각 성능시험을 수행하였다. 시험결과를 통해 입구에 S자형 덕트가 있는 경우에는 없는 경우보다 압축비 및 효율 등 압축기 성능이 저하되고, 쵸킹유량이 감소함을 알 수 있었다. 이러한 성능저하의 원인을 분석하기 위해 S자형 덕트를 포함하는 임펠러의 유동해석을 수행하였으며, 그 결과 성능저하의 원인은, S자형 덕트와 임펠러의 상호작용으로 설계시 예측했던 것보다 인듀서팁에서 상대마하수가 증가하였고, 영각이 감소하였기 때문임을 확인할 수 있었다.

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환상이중원관에서 R-113의 비등열전달에 관한 연구 (A Study on the Boiling Heat Transfer of R-113 in a Concentric Annular Tube)

  • 김명환;김철환;오철;윤석훈;김경근
    • Journal of Advanced Marine Engineering and Technology
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    • 제18권5호
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    • pp.12-23
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    • 1994
  • The two-phase flow is observed in power plants, chemical process plants, and refrigeration systems etc., and it is very important to solve the heat transfer mechanism of a boiler, an automic reactor, a condenser and various types of evaporators. Recently, the problem of two phase heat transfer is braught up in many regions with development of energy saving technique. In flow boiling system it is necessary to store data in each condition because the heat transfer characteristics of flow boiling region vary by the change of flow pattern and the magnetude of heat flux to tube length, and be subtly affected by the flow and heating condition. So basic study for knowing flow pattern in heat transfer region and the relation between heat transfer characteristic and flow condition is desired to accumulate data in wide variety of liquid and flow system in the study of heat transfer of two phase flow. In this study R-113 was selected as working fluid whose properties were programmed by least square method, and experiment was conducted in the region of mass flow $1.628{\times}10^6$~$4.884{\times}10^6$/kg/$m^2$hr with inlet subcooling 10~3$0^{\circ}C$, sustaining test section inlet pressure to 1.5kg$_f$/$cm^2$abs.

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