국부적 정체 기류 지표(역류량 지수) 제안과 구조형상 영향 분석

오승택,김기수,강덕만,지광습 한국풍공학회 2021 한국풍공학회지 Vol.25 No.2

구조물 환기성능 평가에서 기존 사용된 환기 지표 (ACH: Air Change per Hour)는 유체가 거동하는 구조물 내 유량의 흡·배기량과 전체 볼륨에 의해 결정된다. 이는 구조물 내 유체 유동 중 국부적으로 정체된 흐름을 평가하는 지표로 사용하기 부적합하다. 본 논문에서는 구조물에서 국부적으로 정체된 흐름을 정량적으로 나타내기 위해 역류량을 이용하여 새로운 지표 (κ: 역류량 지수)를 제안 하고, 구조형상 변수에 의해 국부적으로 정체된 유체 흐름을 평가한다. 유체 흐름 영향인자로 구조형상 변수는 공극비 (ρ), 공극 개수 (N)로 선정한다. 전산 유체 역학 (CFD)에 의한 해석 결과, 구조형상 변수에 의한 자연 환기 성능은 유사하지만, 공극의 유무에 의한 국부 정체 기류의 크기에는 차이가 발생함이 나타난다. 또한, 역류량 지수는 구조형상 변수 각각 감소함에 따라 값이 증가하는 경향이 나타난다. 본 결과를 바탕으로 회귀분석을 통해 공극비과 공극 개수 변수에 의한 역류량과 역류량 지수의 근사값이 제시된다. A traditional ventilation index (ACH: Air Change per Hour) is determined by the total volume and supply/exhaust flow rate. However, this index is not suitable to evaluate the local stagnant air flow. In this paper, a new index (κ: Reverse-flow rate index) is proposed by using a reverse-flow rate in order to indicate the local stagnant air flow quantitatively. In addition, the amount of local stagnant air flow is evaluated by the change of structural shape variables. The structural shape variables which induced an influence on the fluid flow are considered by the porosity (ρ) and the number of gaps (N ). As the result from the analysis of computational fluid dynamics (CFD), the performance of natural ventilation by the structural shape variables is similar, but there is a disparity for size of a local stagnant air flow by presence or absence of gaps. In addition, it is showed that the reverse-flow rate index has a tendency to increase the value with decreasing the value of porosity and the number of gaps each. Based on these performances, the approximated values of reverse-flow rate and the reverse-flow rate index are presented by a function of the porosity and the number of gaps through the regression of surface fitting.

유량변화가 원심압축기 베인리스 디퓨저 내부유동에 미치는 영향

성선모(Seonmo Seong),강신형(Shinhyoung Kang) 한국추진공학회 2012 한국추진공학회 학술대회논문집 Vol.2012 No.11

원심압축기 전체 유로에 대한 수치해석을 수행하여 유량 변화에 따른 임펠러 출구와 베인리스 디퓨저 내부유동장의 변화를 상세히 검토하였다. 임펠러 출구에서는 익단 간극유동으로 인해 쉬라우드의 경계층이 두껍지만 디퓨저 하류로 갈수록 허브쪽 경계층이 급속히 성장하게 된다. 저유량에서 허브쪽으로 이동한 저운동량 유체는 디퓨저 입구에서 R=1.5 사이의 급격한 압력구배에 의해 원주방향 일부 영역에서 역류하게 되고 유량을 더 줄이면 역류영역이 전체 원주방향으로 확장되어 링 모양의 역류영역이 나타난다. 원주방향 전체로 확장된 역류영역은 디퓨저 내부유동을 불안정하게 하며 이러한 현상이 발생하는 작동점이 정상상태 계산의 한계점으로 판단된다. The flow fields at the impeller exit and in the vaneless diffuser with variation in the flow rate are investigated using the CFD approach. The boundary layer is thicker due to the tip clearance flow near shroud at the impeller exit, while the rapid growth of the boundary layer near hub is predicted as the fluid passes through the vaneless diffuser. Adverse pressure gradient in the vaneless diffuser causes the low momentum fluid moving towards the hub side at the impeller exit to be reversed at a part of the circumference. At further reduced flow rate, the reverse flow zone expands over the full circumference, resulting in the ring-shaped reverse flow zone. It is judged that this enlarged reverse flow generates the flow instability and the corresponding operating point is the limit of the steady state calculation.

장애물이 있는 정사각 덕트의 역류유동 특성

손동현(D.H.Sohn),손창현(C.H. Sohn),Gowda 한국자동차공학회 2007 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-

In the present study the reverse flow phenomenon in a square duct is investigated using PIV. The flow features are much different in this case compared to the two-dimensional channel as we are dealing with the three dimensional square duct flow (side:b) and the obstruction now is a square plate. The flow at the rear end of the duct where reverse flow enters, reveals features of three dimensional vortical flow and shear layer interactions. Figure 1 shows the flow field at the entrance and rear ends of the duct for a typical case. The detailed flow field including animation and PIV measurements will be presented in the final version of the paper.

받음각이 큰 평판 채널 내의 역류 유동 해석

최승(Seung Choi),손창현(Chang Hyun Sohn) 한국가시화정보학회 2007 한국가시화정보학회지 Vol.5 No.1

Reverse flow occurs in a channel when there is an obstruction at the entry. However it has been shown recently that reverse flow can be realized without an obstruction, by staggering the sides of the channel and placing it at an angle of attack to the oncoming flow. In this study the latter flow is computationally investigated. Studies have been carried out for different widths (gap between the two walls forming the channel), and at an angle of attack of 30.The results have captured all the essential features of this complex phenomenon and show the time dependent pumping mechanism which leads to the occurrence of reverse flow.

받음각이 큰 평판 채널 내의 역류 유동 해석

최승,손창현 한국가시화정보학회 2007 한국가시화정보학회지 Vol.5 No.1

Reverse flow occurs in a channel when there is an obstruction at the entry. However it has been shown recently that reverse flow can be realized without an obstruction, by staggering the sides of the channel and placing it at an angle of attack to the oncoming flow. In this study the latter flow is computationally investigated. Studies have been carried out for different widths (gap between the two walls forming the channel), and at an angle of attack of 30.The results have captured all the essential features of this complex phenomenon and show the time dependent pumping mechanism which leads to the occurrence of reverse flow.

3차원 현장 수리계측을 통한 팔당호 두물머리 합류부 역류 공간분포 분석

강용묵,김동수,최수인,박세휘,김영도 한국수자원학회 2025 한국수자원학회 논문집 Vol.58 No.12

This study aimed to investigate seasonal reverse flow phenomena in the upstream confluence zone of Paldang Lake, a river-type reservoir. Five field surveys were conducted from 2023 to 2024, focusing on discharge, flow momentum of the North Han River and South Han River, as well as vertical profiles of temperature and electrical conductivity at the confluence. Results showed that reverse flow from the South Han River into the North Han occurred consistently across all cases, regardless of momentum dominance, with its spatial extent varying seasonally. In contrast, inflow from the North Han into the South Han was limited and primarily influenced by localized stagnant zones formed by channel curvature, rather than by dynamic reverse flow. Stratified reverse flows were particularly evident under combined conditions of discharge imbalance and thermal contrast, indicating the influence of density gradients. The findings provide a useful foundation for understanding hydraulic complexity and mass movement within compound river confluence systems.

양광시스템용 사류형 펌프의 내부유동 해석

이진우(J. W. Lee),윤치호(C. H. Yoon),박종명(J. M. Park),최영도(Y. D. Choi),이영호 (Y. H. Lee) 한국동력기계공학회 2009 한국동력기계공학회 학술대회 논문집 Vol.2009 No.11

The development of lifting pumps that lift minerals to a mining vessel are one of the vital parts of the commercial mining process. Lifting pumps with a high total head are needed as lifting pumps transfer minerals from the deep sea to a waiting vessel. Accordingly, when we designed the lifting pumps we needed to design the centrifugal pump with a high total head. However, that kind of pump has a small specific speed and it created a small passageway, so they had a problem transferring the minerals. Therefore, we designed a mixed flow pump which has a wider passage way for minerals to flow. Technology to design the pump requires a lot of experience, so more research into how the pump operates is necessary. In this research, I examined the internal flow of the pump by CFD to gather basic information for developing the pump's performance.

1,000마력급 터보샤프트엔진 역류형 환형 연소기 성능시험평가 연구

김재호,이상윤,김형모,이동호,황동현,김주평,안철주,서중보 한국추진공학회 2024 한국추진공학회지 Vol.28 No.1

본 논문은 한국항공우주연구원과 한화에어로스페이스에서 수행하고 있는 1,000 마력급 터보샤프트엔진 개발과제에 활용될 역류형 환형 연소기 성능시험평가에 관한 내용이다. 연소기 개발과정은 노즐 버너시험, 섹터 연소기 성능시험, 환형 연소기 성능시험순으로 진행되었다. 연소기는 분무 성능이 뛰어난 공기 충돌 연료노즐과 유출냉각 방식이 적용된 라이너를 국내 최초로 사용하였다. 연소기 구성품의 성능시험 통해 엔진 개발 요구성능 목표 항목인 연소효율, 압력손실, Pattern Factor, Profile Factor의 성능 조건을 모두 만족함을 확인하였다. This paper presents research on the performance test evaluation of the reverse flow annular combustor used in the 1,000 shp(shaft horsepower)-class turboshaft engine development project conducted by the Korea Aerospace Research Institute and Hanwha Aerospace. The combustor development process was conducted in the order of fuel nozzle burner test, sector combustor performance test, and annular combustor performance test. An Air-blast fuel nozzle and a combustor liner with the Effusion Cooling method are used in gas turbine engines for the first time in Korea. Through the performance test of the combustor, the combustion test results demonstrated that all requirements for combustor performance, including maximum exit temperature, combustion efficiency, pattern factor, and profile factor, were met. The final shape of the combustor was derived.

병렬 미세관에서의 기포성장 및 역류현상에 관한 수치적 연구

이우림(Woorim Lee),손기헌(Gihun Son) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.2

The bubble dynamics and heat transfer associated with nucleate boiling in parallel microchannels is studied numerically by solving the equations governing conservation of mass, momentum and energy in the liquid and vapor phases. The liquid-vapor interface is tracked by a level set method which is modified to include the effects of phase change at the interface and contact angle at the wall. Also, the reversible flow observed during flow boiling in parallel microchannels has been investigated. Based on the numerical results, the effects of contact angle, wall superheat and the number of channels on the bubble growth and reversible flow are quantified.

다중 미세관에서의 비등 및 역류현상에 대한 수치적 연구

이우림(Woorim Lee),손기헌(Gihun Son) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10

The bubble motion and heat transfer during nucleate boiling in parallel microchannels is investigated by numerically solving the equations governing conservation of mass, momentum and energy in the liquid and vapor phases. A level set method, which is modified to include the effects of phase change at the interface and contact angle at the wall, is used to track the liquid-vapor interface. The reversible flow appears during flow boiling in parallel microchannels with a bubble located asymmetrically. The effects of contact angle and wall superheat on bubble growth and heat transfer from the numerical results are quantified.