대규모 와 모사를 통해 운전 부하가 튜브 축류홴의 날개에 작용하는 정압 분포와 항력에 미치는 영향 분석

김장권,오석형 한국동력기계공학회 2023 동력시스템공학회지 Vol.27 No.6

In this study, the model of a tube axial fan designed by assuming the total pressure ratio of the span length was analyzed by large eddy simulation in a three-dimensional, incompressible flow, and the drag and the static pressure distribution acting on the blade were investigated according to the change of operating point. As a result, the axial drag coefficient is highly dependent on the static pressure force and shows a decreasing distribution directly proportional with the flowrate showing about 0.27 and about 0.15 at the design operating point and maximum flowrate, respectively. On the other hand, the static pressure on the pressure surface of the blade varies in size according to the change in the operating load, and the contour line formed very narrowly at the blade hub from the leading edge to the trailing edge of the blade spreads and develops like a fan rib toward the tip of the blade and is distributed to the trailing edge of the blade. In addition, the static pressure of the suction surface of the blade has a gentle slope with a similar contour line size from the hub to the tip until the design operating point. However, after the design operating point, the size increases slightly and is biased toward the blade hub, developing near the middle of the blade.

저소음 패키지 에어컨 실내외기 개발에 관한 연구

김장권,Kim, Jang-Kweon 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.6

The purpose of this study was to reduce the airborne noise emitted from the package air-conditioner(PAC) therefore, the optimim design melthods of the fans and the flow-paths were investigated experimentally through the anlaysis of the nose problems caused by the conventional PAC system, and the fan performance tests and the systme resistance measurements of the parts which belong to the flow-paths of the PACwere used to study these noise problems. As a results, through the optimized flow-paths of the new PAC system with the lowset system resistance, and by adjusting and matching the operating point of each fan to each PAC system, the airborne noise reductions from the new indoor PAC and the outdoor one were achieved upto 5.5 dBA and 6.6 dBA respectively in overall noise level as compared with the conventional PAC system.

Gun식 가스버너의 난류유동장 발달에 미치는 슬릿과 스월베인의 영향

김장권,Kim, Jang-Kweon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.9

This paper is studied to investigate the effect of slits and swirl vanes on the development of turbulent flow fields in gun-type gas burner with a cone type baffle plate because this gas burner is generally composed of eight slits and swirl vanes. All of turbulent characteristics including mean velocities were measured in the horizontal plane and cross section by using X-type hot-wire probe from hot-wire anemometer system. This experiment is carried out at flow rate 450 l/min in the test section of subsonic wind tunnel. Slits cause the fast jets, and then they have the characteristic that the flow is not adequately spread to radial direction and has long flow length and very small flow velocity distribution in the central part. On the contrary, swirl vanes does not have long enough for adequate flow length to downstream because the rotational flow diffuses remarkably to radial direction. However, the suitable arrangement between slits and swirl vanes causes effective flow width and flow length, and then it promotes fast flow mixing over the entire region including central part to increase turbulence more largely and effectively. Therefore, it is thought as a very desirable design method in gun-type gas burner to locate slits on the outside of swirl vanes.

콘형 배플판을 갖는 Gun식 가스버너의 난류유동장에 대한 슬릿과 스월베인의 역할

김장권,정규조,Kim, Jang-Kweon,Jeong, Kyu-Jo 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.4

The gun-type gas burner adopted in this study is generally composed of eight slits and swirl vanes. Thus, this paper is studied to investigate the effect of slits and swirl vanes on the turbulent flow fields in the horizontal plane of gas swirl burner with a cone type baffle plate measured by using X-probe from hot-wire anemometer system. This experiment is carried out at flow rate 450 $\ell$/min in the test section of subsonic wind tunnel. The axial mean velocity component in the case of burner model with only swirl vanes shows the characteristic that spreads more remarkably toward the radial direction than axial one, it does, however, directly opposite tendency in the case of burner model with only slits. Consequently. both slits and swirl vanes composing of gun-type gas burner play an important role in decrease of the speed near slits and increase of the flow speed in the central part of a burner because the biggest speed spurted from slits encircles rotational flow by swirl vanes and it drives main flow toward the axial direction. Moreover, the turbulent intensities and turbulent kinetic energy of gun-type gas burner are distributed with a fairly bigger size within X/R<0.6410 than burner models which have only slits or swirl vanes because the rotational flow by swirl vanes and the fast jet flow by slits increase flow mixing, diffusion, and mean velocity gradient effectively.

가스난방기용 스월버너의 3차원 난류운동 특성에 관한 실험적 연구

김장권 대한기계학회 2001 大韓機械學會論文集B Vol.25 No.2

배플판 형상이 다른 Gun식 가스버너의 난류유동 특성치 고찰

김장권,정규조 대한기계학회 2004 大韓機械學會論文集B Vol.28 No.4

석유 팬 히터의 연소실 주변 열전달 특성

김장권,Kim, Jang-Gwon 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.4

This paper was studied to understand the characteristics of heat transfer coefficients and surface temperature distributions around a circular combustion chamber within the heat-intercept duct of kerosene fan heater. The experiment was carried out in the heat-intercept duct of kerosene fan heater attached to the blow-down-type subsonic wind tunnel with a test section of 240 mm * 240 mm * 1200 mm. The purpose of this paper was to obtain the basic data related with normal combustion for new design from conventional kerosene fan heater, and to investigate the effect of surface temperature, local and mean heat transfer coefficients versus flow-rate of convection axial fan according to the variations of heat release conditions from kerosene fan heater during normal combustion. Consequently it was found that (i) the revolution of convection axial fan during combustion had a smaller value than that of non-combustion because of the thermal resistance due to the high temperature in the heat-intercept duct, (ii) the pressure ratio P$_{2}$/P$_{1}$ had a comparatively constant value of 0.844 according to the revolution increase of turbo fan and the heating performance of kerosene fan heater had a range of 1,494 ~ 3,852 kcal/hr, (iii) the local heat transfer coefficient around a circular combustion chamber had a comparatively larger scale in the range of 315 deg. < .theta. < 45 deg. than that in the range of 90 deg. < .theta. < 270 deg. as a result of heat transfer difference between front and back of a circular combustion chamber, and (iv) the mean heat transfer coefficient around a circular combustion chamber increased linearly like a H$_{m}$=95.196Q+104.019 in condition of high heat release according to the increase of flow-rate of axial fan.n.

날개 길이가 다른 1피치 소형 나선형 축류홴의 공력성능에 관한 대규모 와 모사

김장권,오석형 한국동력기계공학회 2020 동력시스템공학회지 Vol.24 No.3

세 가지 유형의 소형 나선형 축류홴 (SSHAF) 및 소형 축류홴 (SSAF)의 공력성능을 분석하기 위해 비정상상태, 비압축 및 3 차원 직교 좌표계에서 대규모 와 모사(LES)가 수행되었다. SSHAF의 유량계수에 대한 정압계수 및 동력계수들은 날개 길이가 증가함에 따라 증가하며, SSAF와 달리 실속을 나타내는 불안정한 영역은 없다. 또한, 날개 길이가 증가함에 따라 SSHAF의 동력 계수의 증가율은 동일한 유량 대비 약 2배씩 나타난다. SSHAF의 유량계수에 대한 정압 효율 및 전압 효율의 분포는 날개 길이에 관계없이 SSAF의 것들보다 높으며, 날개 길이가 100mm 인 경우에 최댓값은 각각 약 48 % 및 54 %이다. 결과적으로 SSHAF는 날개 길이를 변경함으로서 SSAF와 유사한 공기 역학적 특성을 나타낼 수 있기 때문에, 새로운 축류홴으로 충분히 교체 가능하다고 간주된다.

질량유량 변화에 따른 실물 크기 원통다관식 열교환기의 열전달 성능 평가

김장권,오석형 한국동력기계공학회 2022 동력시스템공학회지 Vol.26 No.4

본 논문에서는 쉘과 관다발로 흐르는 질량유량이 5가지로 변경될 때, 열교환 길이가 2000mm인 실물크기 3차원 원통다관식 열교환기(STHEX)의 상호 열전달을 해석하기 위해 realizable k-ε 난류 모델을 사용하였다. 쉘에서 손실된 열량과 관다발에서 얻은 열량은 각각 쉘과 관다발의 질량유량이 증가할 때 거의 동일하며 비선형적으로 분포한다. 또한, 전체 열전달계수는 쉘과 관다발의 질량유량이 증가함에 따라 비선형적으로 증가하며, 주어진 질량유량에서 약 420~670W/m2·℃의 값을 나타낸다. 한편, 열전달량 등과 같은 다양한 근사식은 쉘과 관다발의 질량유량 변화에 대응하여 많은 정보를 제공하는 중요한 데이터가 될 수 있다고 판단된다.

실물 크기를 갖는 원통다관식 열교환기의 열전달 요구성능에 적합한 열교환 길이 결정

김장권,오석형 한국동력기계공학회 2022 동력시스템공학회지 Vol.26 No.5

본 논문에서는 시행착오 방법으로 STHEX의 요구되는 열전달 성능에 적합한 실제 열교환 길이를 결정하기 위해 4개의 열교환 길이를 갖는 완전한 3차원 STHEX 모델을 Realizable k-ε난류모델로 열전달 수치해석을 수행하였다. 관다발과 쉘측의 압력강하는 STHEX의 열교환 길이가 증가할 때 각각 비선형적으로 증가하거나 감소하는 분포를 나타내며, 최대크기는 요구되는 성능을 모두 만족한다. 쉘과 관다발측의 출구 온도는 열교환 길이가 증가함에 따라 각각 감소하거나 증가하며, STHEX의 열교환 길이 1300mm가 요구되는 성능에 가장 가깝다. 한편, 쉘과 관다발측에서 STHEX의 열전달량은 열교환 길이가 증가함에 따라 모두 비선형적으로 증가한다. 또 주어진 STHEX의 열교환 길이에서 총괄 열전달계수는 약 536∼583W/m2·℃를 나타낸다.